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LabVIEW Statistical Process Control Toolkit Reference Manual

1. LabVIEW SPC Toolkit Reference Manual 1 12 National Instruments Corporation Chapter 1 Introduction to Statistical Process Control in LabVIEW Figure 1 6 Diagram for Basic Tier Chart Upper Specification Limit Lower Specification Limit ATER show natural process limits ta a Creating Control Charts and Determining Whether the Process is in Control You use control charts to determine if a process is in control The LabVIEW SPC Toolkit VIs generate the following standard types of control charts e Variables charts X bar and standard deviation X bar amp s Chart VI X bar and range X bar amp R Chart VI X and moving range x amp mR Chart VI moving average and moving range mX bar amp mR Chart VI e Attributes Charts p p Chart VI np np Chart VI u u Chart VI c c Chart VI The control chart VIs calculate the control limits for a control chart Normally the control chart VIs use the process data to calculate the control limits You must choose the set of samples from which to calculate the control limits Variables charts typically use the first 20 to 30 samples of sample size four or five for a total of about 100 individual observations of the process The control chart VIs can also calculate control limits from standard values Once the VI calculates the limits there are several ways to plot the control charts with corresponding VIs that will generate
2. LabVIEW ll Statistical Process Control Toolkit acuuscsss Reference Manual onog Copyright 1994 National Instruments Corporation Part Number 320753A 01 All rights reserved September 1994 National Instruments Corporate Headquarters 6504 Bridge Point Parkway Austin TX 78730 5039 512 794 0100 Technical support fax 800 328 2203 512 794 5678 Branch Offices Australia 03 879 9422 Austria 0662 435986 Belgium 02 757 00 20 Canada Ontario 519 622 9310 Canada Qu bec 514 694 8521 Denmark 45 76 26 00 Finland 90 527 2321 France 1 48 14 24 24 Germany 089 741 31 30 Italy 02 48301892 Japan 03 3788 1921 Netherlands 03480 33466 Norway 32 848400 Spain 91 640 0085 Sweden 08 730 49 70 Switzerland 056 20 51 51 U K 0635 523545 Limited Warranty The media on which you receive National Instruments software are warranted not to fail to execute programming instructions due to defects in materials and workmanship for a period of 90 days from date of shipment as evidenced by receipts or other documentation National Instruments will at its option repair or replace software media that do not execute programming instructions if National Instruments receives notice of such defects during the warranty period National Instruments does not warrant that the operation of the software shall be uninterrupted or error free A Return Material Authorization RMA number must be obtained from the factory
3. Fule 1 One point outside 3 std errors Rule 2 Two out of three consecutive points outside 2 std errors Zone A or beyond ule 3 Four out of five consecutive points outside 1 std errors Zone B or beyond Rule 4a Seven consecutive points on one side of the center line Rule 4b Eight consecutive points an one side of the center Tine Fi 1 14 Di for Zone Rule Test AT amp T WE Example Wes Fule Violations Rule daigh After you have identified samples that have violated run rules you can recalculate the control limits by calling the Control Chart VI again and pass in the list of sample indices to ignore Note Before ignoring a sample in a control limit calculation you must know what caused the sample to be out of control that is you need to know the assignable cause You can also apply run rules to detect process shift which indicates that control chart limits should be recalculated because the process has changed shifted with respect to the center line The Process Shift LabVIEW SPC Toolkit Reference Manual 1 18 National Instruments Corporation Chapter 1 Introduction to Statistical Process Control in LabVIEW Detector VI uses four rules to detect process shift and identifies the first point of the process shift Process Capability Analysis Using process capability analysis you can quantify the ability of your process to create product within specification Once your process is in co
4. 1 use std cO chart limits are calculated from the standard value c0 std c0 The standard cO value to use when calculating chart limits from standard values The center line for the control chart c bar will then be set to c0 The control limit calculations are as follows If standard values are used for the control limit calculations then c bar is set to std c0 otherwise c bar is calculated from the input samples as specified by the index spec and indices to ignore inputs c c if calculated from the input data c array length otherwise c c0 UCLc stderr mult Je CLC National Instruments Corporation 2 31 LabVIEW SPC Toolkit Reference Manual Control Chart VIs DEL Chapter 2 LCLnp c stderr mult Je standard error Je u Chart Computes points and limits for a u chart a control chart for fraction of non conformities or defects Number of units inspected n can be constant for all c or vary for each element in c Calculates both variable and constant chart limits Optionally you can choose a range of indices for samples to use and indices of samples to ignore in the control calculation The actual number of samples the VI uses to calculate the control limits is also output By default control limits are calculated from the input samples You can also calculate control limits from standard values by wiring the chart limit sre input chart limit sre Copt J samples in calc c defects sample
5. Chapter 2 DBL Fl HERE JR Control Chart VIs starting individual number 0 Samples X upper spec limit lower spec limit process mean process sigma display mode CFF 3 You can turn on and off drawing of the specification limits or the natural process limits and choose the sigma multiplier to use for the natural process limits default three by wiring in the display mode If you do not wire the display mode the VI does not draw the specification limits and natural process limits by default samples X The points to be plotted on the run chart Each row is a sample with n observations where n is the number of columns in the 2D array N is also known as the subgroup size You can generate a run chart from a 1D array by wiring it to a build array primitive before wiring it to the samples X input starting individual number The individual number of the first individual the VI uses to label the chart x axis If you do not wire this input sample labeling on the x axis will start at zero upper spec limit The upper specification limit of the process lower spec limit The lower specification limit of the process process mean The estimated process mean See the description of the Process Mean and Sigma VI in Chapter 3 Process Statistics VIs for an explanation of how the process mean and process sigma values are calculated process sigma The estimated process sigma display mode Optional display mode speci
6. individual x Individual on which to compute the control chart points n sample size The sample size to use for the moving average and moving range calculations n sample size ranges from 2 to 25 By default sample size is 2 EE first point F Use this input to initialize the VI first point should be TRUE for the first point FALSE afterwards The VI will calculate the first point moving range mR as zero i F individual x Wire this output to the waveform chart to create an X control chart moving Average mX bar The average of the current individual x and the previous sample size n 1 individual x values Wire this output to the waveform chart to create a moving average control chart moving Range mR The range of the current individual x and the previous sample size n 1 individual x values Wire this output to the waveform chart to create a moving range control chart aE valid mX bar mR This is set to TRUE when the VI has accumulated sample size n points to calculate the moving Average and Range For example for sample size n 2 the VI would have to be called twice in order to have accumulated 2 individual x values from which it calculates the moving average and range Until sample size n values have been TE National Instruments Corporation 2 23 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 accumulated the moving average and range are calculated from a smaller sample size and valid
7. HE CLr The center line for the R chart CLr R bar if calculated from the input samples otherwise this is standard RO or standard sigma d2 LCLr The lower control limit for the R chart E LabVIEW SPC Toolkit Reference Manual 2 12 National Instruments Corporation Chapter 2 Control Chart VIs standard error The standard error associated with CLr R bar d2 This is an estimate of the process sigma standard deviation based on the average range of the samples included in the control limit calculation If the control limits are calculated from standard values this is set to standard RO d2 or standard sigma samples in calc The number of samples the VI used in the control limits calculation chart limit src Specifies whether or not to use standard values for the chart limit calculations If unwired this defaults to the common case where the chart limits are calculated from the data in the input sample array You do not have to wire this cluster unless you want the chart limits to be calculated from standard values When using standard values the center line for the X bar control chart X bar bar is set to std mean and the center line for the Rcontrol chart R bar is set to std RO or std sigma d2 source Selects one of three sources for chart limits calculation 0 from data chart limits are calculated from the data in the samples X array as qualified by the index spec and indices to ignore inputs default select
8. 16 National Instruments Corporation Chapter 1 Introduction to Statistical Process Control in LabVIEW Figure 1 12 Diagram Plot bar chart for X bar amp Range Lee eos ecbar char Chart Check Limits ae eee Example Control Limits computed H from first 25 samples H Re par a gt H imi T Foints Exceeded Limits Check limits on both charts control chart Control points calculated from a process can stay within the control limits but still exhibit nonrandom behavior such as repeated patterns in the data To detect such patterns you can use the rule checker VIs to apply run rules to the control chart array The run rules included in the SPC Toolkit are AT amp T Western Electric and Nelson rules The rule checker VIs identify the indices of samples that violate the run rules You can individually enable run rules Figure 1 13 shows the Zone Rule Test AT amp T WE Example which applies the AT amp T Western Electric rules to an X bar chart Figure 1 14 shows the block diagram for this example National Instruments Corporation 1 17 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 Figure 1 13 Zone Control Chart with Zones Rule Test AT amp T WE Example Points Center Line cones Rule Yiolations ist point Run Length a a T w EH oo Ayo ao Ho cH tH tH of Control Points
9. Bins is an array of clusters where each cluster defines the range of values for a bin The cluster includes the following elements lower specifies the lower boundaries of the bin upper specifies the upper boundaries of the bin LabVIEW SPC Toolkit Reference Manual 3 6 National Instruments Corporation Chapter 3 B E i te M Process Statistics VIs inclusion specifies how the boundaries of each bin are treated The acceptable values for inclusion are listed as follows 0 lower 1 upper 2 both Choosing 0 causes the lower boundary to be part of the bin but not the upper boundary Choosing 1 is exactly opposite Both boundaries can be included by choosing 2 If no bin specifications are provided in the input bins the inputs max min bins and inclusion will be used to specify a set of uniformly spaced bins max specifies the maximum value to include in the histogram This parameter is optional as explained below min specifies the minimum value to include in the histogram This parameter is optional as explained below If you do not wire the inputs max and min the VI will use the maximum and minimum values in the input sequence Xd bins specifies the number of bins in the histogram This parameter is optional as explained below If bins is left unwired the number of bins will be determined according to Sturges Rule number of bins 1 3 3log sizeof X inclusion specifies how the boundaries of e
10. Instruments Corporation 2 37 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 average UCL The average upper control limit for the control chart CL The center line for the control chart average LCL The average lower control limit for the control chart standard error The standard error associated with CL A BEE starting sample number The sample number of the first sample the VI uses to label the chart x axis If you do not wire this input sample labeling on the x axis will start at one control chart A control chart XY graph with points and variable limit lines drawn You can wire this to the Control Chart with Var Limits custom SPC control control chart lines This cluster is useful as a legend for the constant limit lines You can wire this to the Control Chart Lines custom SPC control UCL The average upper control limit value for the control chart CL The center line value for the control chart HE E LCL The average lower control limit value for the control chart Draw Run Chart Draws a run chart of the individuals making up the samples X array in time order The VI interprets the individual observations in the samples array to be in time order by row and the individuals within each row by column Optionally the VI plots the specification limits and or the natural process limits against the observations LabVIEW SPC Toolkit Reference Manual 2 38 National Instruments Corporation
11. Refnum Abbreviations acronyms metric prefixes mnemonics symbols and terms are listed in the Glossary National Instruments Corporation xi LabVIEW SPC Toolkit Reference Manual About This Manual Related Documentation The following documents contain information that you may find helpful as you read this manual e Your LabVIEW tutorial e Your LabVIEW user manual e American Society for Quality Control American National Standard Definitions Symbols Formulas and Tables for Control Charts 1987 Publication number ANSI ASQC A1 1987 e Breyfogle Forest W Statistical Methods for Testing Development and Manufacturing John Wiley and Sons 1992 e Montgomery Douglas C Introduction to Statistical Quality Control J Wiley and Sons 2nd edition 1991 e Wheeler Donald J and Chambers David S Understanding Statistical Process Control SPC Press 2nd edition 1992 Customer Communication National Instruments wants to receive your comments on our products and manuals We are interested in the applications you develop with our products and we want to help if you have problems with them To make it easy for you to contact us this manual contains comment and technical support forms for you to complete These forms are in the appendix Customer Communication at the end of this manual LabVIEW SPC Toolkit Reference Manual xii National Instruments Corporation Chapter Introduction to Stat
12. The Draw Run Chart and Draw Tier Chart VIs create graphs that are independent of the type of control chart you use and are convenient for viewing the individual observations that make up your samples This class of graphs will optionally plot your data against specification limits or natural process limits National Instruments Corporation 2 5 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 Specification limits are user defined tolerances for the process output Natural process limits are computed from the samples and represent the process mean and 3 sigma The natural process limits are not control limits but are a statistic of the variability in your raw data The Draw Run Chart and Draw Tier Chart VIs are described as follows e Draw Run Chart VI plots a run chart of the individuals within each sample in order of occurrence This VI optionally displays specification limits and or natural process limits process mean and 3 sigma against the data e Draw Tier Chart VI variables charts only plots all observations individuals within each sample This VI optionally displays specification limits and or natural process limits process mean and 3 sigma against the data These VIs have a display mode specifier that you can use to turn on and off drawing of the specification limits or the natural process limits The display specifier also designates the sigma multiplier for the VI to use for the natural process limi
13. Zones Given an array of control chart points and the chart limits cluster as created by the chart VIs creates a control chart graph XY graph indicator with points plotted against zones This VI is useful when visually applying run rules to a control chart points ERER control chart with zones chart limits control chart lines zones 3 starting sample number 0 points The points to be plotted on the control chart Normally the pet output of one of the control chart VIs such as an X bar array chart limits This cluster is output by the control chart VIs UCL The upper control limit for the control chart CL The center line for the control chart LCL The lower control limit for the control chart ALA standard error The standard error associated with CL zones The number of zones to mark on the control chart If you do not wire this input three zones zone A B and C are marked on the chart starting sample number The sample number of the first sample the VI uses to label the chart x axis If you do not connect this input sample labeling on the x axis will start at zero control chart with zones A control chart XY graph with points and horizontal zone lines drawn You can wire this to the Control Chart with Zones custom SPC control control chart zones This cluster is useful as a legend for the zone lines You can wire this to the Control Chart Zones Cluster custom SPC control H H BE
14. and clearly marked on the outside of the package before any equipment will be accepted for warranty work National Instruments will pay the shipping costs of returning to the owner parts which are covered by warranty National Instruments believes that the information in this manual is accurate The document has been carefully reviewed for technical accuracy In the event that technical or typographical errors exist National Instruments reserves the right to make changes to subsequent editions of this document without prior notice to holders of this edition The reader should consult National Instruments if errors are suspected In no event shall National Instruments be liable for any damages arising out of or related to this document or the information contained in it EXCEPT AS SPECIFIED HEREIN NATIONAL INSTRUMENTS MAKES NO WARRANTIES EXPRESS OR IMPLIED AND SPECIFICALLY DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE CUSTOMER S RIGHT TO RECOVER DAMAGES CAUSED BY FAULT OR NEGLIGENCE ON THE PART OF NATIONAL INSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER NATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA PROFITS USE OF PRODUCTS OR INCIDENTAL OR CONSEQUENTIAL DAMAGES EVEN IF ADVISED OF THE POSSIBILITY THEREOF This limitation of the liability of National Instruments will apply regardless of the form of action whether in contract or tort including negligenc
15. and tutorial manuals which cover basic LabVIEW principles To modify the more advanced SPC application examples successfully however you must be an advanced LabVIEW user In the next section you will take a brief look at the organization of the SPC VIs Then the following section guides you through some of the LabVIEW programming techniques you will use in statistical processing SPC Toolkit Organization The SPC Toolkit is organized into three sections VI Libraries Custom Controls and Examples VI Libraries After you have read this chapter you are ready to begin using the SPC Toolkit VIs Click on the block diagram to activate it and select SPC under the Functions menu You see the menu and submenu shown in the following illustration Then select the VI you want the icon corresponding to that VI will appear in the block diagram ready for you to wire it Note The screens illustrated in this manual were taken on the Macintosh If you are using Sun or Windows your screens will look slightly different but the information on the screens is the same across all three platforms LabVIEW SPC Toolkit Reference Manual 1 4 National Instruments Corporation Chapter 1 Introduction to Statistical Process Control in LabVIEW Structs amp Constants Arithmetic Trig amp Log Comparison Conversion String Array amp Cluster File 1 0 Dialog amp Date Time Miscellaneous Ul Analysis DAQ GPIB Network Serial g
16. bar Default is 0 0 dx Bar spacing Default is 1 0 baseline Baseline of bar graph Default is 0 0 alignment Alignment of bar from reference point x 0 Left 1 Center 2 Right Default is 0 Left bar graph An XY graph National Instruments Corporation 4 5 LabVIEW SPC Toolkit Reference Manual Appendix Customer Communication For your convenience this appendix contains forms to help you gather the information necessary to help us solve technical problems you might have as well as a form you can use to comment on the product documentation Filling out a copy of the Technical Support Form before contacting National Instruments helps us help you better and faster National Instruments provides comprehensive technical assistance around the world In the U S and Canada applications engineers are available Monday through Friday from 8 00 a m to 6 00 p m Central time In other countries contact the nearest branch office You may fax questions to us at any time Corporate Headquarters 512 795 8248 Technical Support fax Branch Offices Australia Austria Belgium Denmark Finland France Germany Italy Japan Netherlands Norway Spain Sweden Switzerland U K National Instruments Corporation A 1 800 328 2203 512 794 5678 Phone Number 03 879 9422 0662 435986 02 757 00 20 45 76 26 00 90 527 2321 1 48 14 24 00 089 741 31 30 02 48301892 03 3788 1921 034
17. default control limits are calculated from the input samples You can also calculate control limits from standard values by wiring the chart limit sre input chart limit sre Copt 7 samples in calc r units non conforming sa r units non conforming sa n sample size P std error multiplier 3 np chart limits index spec Copt indices to ignore Copt r units non conforming sample unit The number of units non conforming per sample inspected n sample size Number of units in each sample std error multiplier The multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 index spec Use this cluster to choose a range of samples in r to use for the control limit calculation start index Index of the first element of r to include in the control limit calculation Default is zero which is the index of the first sample in samples X array National Instruments Corporation 2 27 LabVIEW SPC Toolkit Reference Manual Control Chart VIs DEL H BE Chapter 2 end index Index of the last element of r to include in the control limit calculation Default is zero which selects the last sample in r array If you do not wire this cluster the VI includes all elements in r input array in the control limit calculation indices to ignore Indices of r to exclude from
18. directory where you have write permission such as var tmp or your home directory 2 Insert the first SPC Toolkit disk into the 3 5 in disk drive 3 Type tar xf dev rfd0c INSTALL to extract the installation script 4 Torun the installation script type INSTALL Follow the instructions on the screen The installer will prompt you to name the directory that contains LabVIEW and its associated files LabVIEW SPC Toolkit Reference Manual 1 2 National Instruments Corporation Chapter 1 Macintosh Introduction to Statistical Process Control in LabVIEW After you install the LabVIEW SPC Toolkit your LabVIEW directory should contain a new SPC directory and the LabVIEW Functions and Controls menus will contain SPC entries the next time you launch LabVIEW 1 Insert the first SPC Toolkit disk into the 3 5 in disk drive and double click on the LabVIEW SPC Toolkit Installer icon 2 After you select the Install button you are prompted to select a destination directory Select your LabVIEW folder 3 Follow the instructions on the screen After you install the LabVIEW SPC Toolkit your LabVIEW directory should contain a new SPC directory and the LabVIEW Functions and Controls menus will contain SPC entries the next time you launch LabVIEW Requirements for Using the SPC Toolkit Some of what you need to build an SPC application is already part of the LabVIEW programming environment The SPC Toolkit package adds the mis
19. is two Optionally you can choose a range of indices for individuals to use and indices of individuals to ignore in the control calculation The actual number of individuals the VI uses to calculate the control limits is also output By default control limits are calculated from the input samples You can also calculate control limits from standard values by wiring the chart limit sre input LabVIEW SPC Toolkit Reference Manual 2 14 National Instruments Corporation Chapter 2 DEL F la D Control Chart VIs chart limit sro kopti m bar amp mR bar dz individuals x f x index spec kopt f ox chart limits indices to ignore Copt fm moving range mR std error multiplier 2 Eo mR chart limits n sample size C2 individuals in calc individuals x Individual observations or samples of subgroup size 1 on which to compute control limits index spec Use this cluster to choose a range of individuals to use for control limits calculation start index Index of the first individual to include in the control limit calculation Default is zero or index of the first individual in individuals x array end index Index of the last individual to include in the control limit calculation Default is zero which selects the last sample in individuals x array If you do not wire this cluster all values in individuals x input array are included in the control limit calculation indices to ignore Indices of individ
20. of units was inspected for each entry in r Otherwise if you are providing an array for n leave this input unwired LabVIEW SPC Toolkit Reference Manual 2 24 National Instruments Corporation Chapter 2 DEL J J D D gt kd D Control Chart VIs std error multiplier The multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 index spec Use this cluster to choose a range of samples to use in r for the control limits calculation start index Index of the first element of r to include in the control limit calculation Default is zero which is the index of the first sample in r array end index Index of the last element of r to include in the control limit calculation Default is zero which selects the last sample in r array If you do not wire this cluster the VI includes all elements in the r input array in the control limit calculation indices to ignore Indices of r to exclude from the control limit calculation This input is useful for eliminating out of control points from the control limit calculation By default this is an empty array samples in calc The number of samples used in the control limits calculation p fraction non conforming The number of units non conforming divided by the number inspected This is the fraction non confor
21. size 1 DEL ee peL on which to compute control limits LabVIEW SPC Toolkit Reference Manual 2 18 National Instruments Corporation Chapter 2 1 i E J D Control Chart VIs index spec Use this cluster to choose a range of individuals to use for control limits calculation start index Index of the first individual to include in the control limit calculation Default is zero or index of the first individual in individuals x array end index Index of the last individual to include in the control limit calculation Default is zero which selects the last sample in individuals x array If you do not wire this cluster all values in individuals x input array are included in the control limit calculation indices to ignore Indices of individuals to exclude from the control limit calculation This is useful for eliminating out of control points from the control limit calculation By default this is an empty array std error multiplier The multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 x bar bar This is an estimate of the process mean based on the moving average of the individuals included in the control limit calculation If the control limits are calculated from standard values this is set to the standard mean moving Average mX bar The moving average of
22. test bound violations per run The number of violations per run length that indicate a rule has been violated run length The run length for the rule violation start point Start point of each sequence violating the rule violation run length The length of each sequence violating the rule National Instruments Corporation 2 47 LabVIEW SPC Toolkit Reference Manual Chapter Toooogogogoooogo Process Statistics VIs v 200 A DEL This chapter describes the process statistics VIs which are useful for process capability analysis and for viewing and measuring process distribution The process statistics VIs perform the following operations e compute process mean and sigma e compute process capability ratios and reject rates e create and graph histograms e plot normal probability distribution functions against histograms and process specification limits Process Mean and Sigma Computes process mean and sigma and upper and lower natural process limits from process samples You can estimate the process sigma in several ways If the sample size is greater than one you can use either sample standard deviation s or range R to estimate the process sigma You select s or R by the type input If the sample size is one the VI automatically uses the moving range to estimate the process sigma Samples X it process mean type S F Cs process sigma n for moving Range 2 upper NPL sigma multip
23. the VI will draw the specification limits The default is FALSE show natural process limits If TRUE the VI will draw the natural process limits on the plot The default is FALSE NP limit sigma The sigma multiplier for the natural process limits By default this is 3 The natural process limits drawn on the plot will then be process mean NP limit sigma process sigma Note Ifyou wire the display mode cluster to change one of the default settings you must select all three elements tier chart A graph in which the VI plots the observations in each sample vertically Optionally the VI plots the upper and lower specification limits and the mean specification value and or the natural process limits and process mean against the sample plots You can wire this to the Tier Chart custom SPC control National Instruments Corporation 2 41 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 Rule Checker VIs As described earlier in this chapter you use the rule checker VIs to test whether points exceed the control limits or whether any of the run rules are violated Check Control Limits Given a set of control chart points and the upper and lower control limits from the control chart VIs this VI checks for points that exceed the control limits If such points exist the VI lists the index of each point that exceeds the limits in the order of how much each point exceeds the control limits points points excee
24. the XY graphs National Instruments Corporation 1 13 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 for the different chart styles The most common presentation is a control chart that draws the data against the three standard error control limits illustrated in Figure 1 7 in which the Draw Control Chart VI does the graphing Figure 1 8 shows the block diagram for this VI example Fi 1 7 X b Samples igure 1 7 X bar 31a 5 and S Control Chart TEN trai Example F io 12 14 16 5 CLs LCLs at or m PEEN AN eners 12 i4 16 Figure 1 8 Diagram for X bar and S Control Whar Chart Chart Example LabVIEW SPC Toolkit Reference Manual 1 14 National Instruments Corporation Chapter 1 Figure 1 9 p Chart Example Var Limits Figure 1 10 Diagram for p Chart Example Var Limits Introduction to Statistical Process Control in LabVIEW The Draw Chart with Zones VI divides the area between the three sigma control limits into six zones that are one sigma wide and draws the zones against the control chart points This presentation is useful when you want to apply rules to the chart to detect out of control points This use of a zones chart is illustrated in the next section Detecting Out of Control Points Figures 1 13 and 1 14 Some of the attributes charts calculate variable control limits which are plotted by the Draw Ch
25. the control limit calculation This is useful for eliminating out of control points from the control limit calculation By default this is an empty array samples in calc The number of samples used in the control limits calculation r units non conforming sample unit The number of units non conforming found per sample unit This is identical to the input array r These are the points plotted on the np control chart np chart limits This cluster contains the limits for the np chart UCLnp The upper control limit for the np chart If Std error multiplier is three this will be np bar 3 standard errors CLnp The center line for the np chart np bar or standard pO n np bar is the estimated number non conforming for the process if calculated from the input data LCLnp The lower control limit for the np chart If Std error multiplier is three this will be np bar 3 standard errors standard error The standard error associated with CLnp ia oe chart limit src Specifies whether or not to use standard values for the chart limit calculations If unwired this defaults to the most common case where the chart limits are calculated from the data in the input array You do not have to wire this cluster unless you want the chart limits to be calculated from standard values When using standard values the center line for the control chart np bar is set to n p0 source Selects one of two sources for chart limits calculatio
26. u average defects unit n sample size variable ca UcLu n sample size constant LCLu std error multiplier 3 H B u chart limits index spec Copt a indices to ignore Copt c defects sample The number of non conformities or defects found for each number inspected n sample size variable The number of units inspected for each value of c Use this array if a variable number of units were inspected for each entry in c The array length must be the same as the length of the array c n sample size constant Use this input if the same number of units was inspected for each entry in c Otherwise if you are providing an array for n leave this input unwired std error multiplier The multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 index spec Use this cluster to choose a range of samples in u to use for the control limit calculation LabVIEW SPC Toolkit Reference Manual 2 32 National Instruments Corporation Chapter 2 J D kd J D D Control Chart VIs tart index Index of the first element of u to include in the usz S sz control limit calculation The default is zero which is the index of the first sample in samples X array end index Index of the last element of u to include in the control limit calculation The default is
27. zero which selects the last sample in c array If you do not wire this cluster the VI includes all elements in u input array in the control limit calculation indices to ignore Indices of u to exclude from the control limit calculation This is useful for eliminating out of control points from the control limit calculation By default this is an empty array u average defects unit The number of defects divided by the number inspected This is the average number of non conformities or defects per unit inspected This array is plotted on the u control chart UCLu The variable limit for the upper control limits If std error multiplier is three this output will be u bar 3 standard errors LCLu The variable limit for the lower control limits If std error multiplier is three this will be u bar 3 standard errors The standard error calculation varies with n u chart limits This cluster contains the constant limits for the u chart average UCLu The average value of the variable upper control limit for the u chart If the number inspected is constant use this for the upper control limit CLu The center line for the u chart u bar or standard u0 u bar is the estimated fraction of non conformities or defects for the process if calculated from the input data average LCLu The average value of the variable lower control limit for the chart If the number inspected is constant use this for the lower control limit stand
28. 80 33466 32 848400 91 640 0085 08 730 49 70 056 20 51 51 0635 523545 Fax Number 03 879 9179 0662 437010 19 02 757 03 11 45767111 90 502 2930 1 48 14 24 14 089 714 60 35 02 48301915 03 3788 1923 03480 30673 32 848600 91 640 0533 08 730 43 70 056 20 51 55 0635 523154 LabVIEW SPC Toolkit Reference Manual Technical Support Form Photocopy this form and update it each time you make changes to your software or hardware and use the completed copy of this form as a reference for your current configuration Completing this form accurately before contacting National Instruments for technical support helps our applications engineers answer your questions more efficiently If you are using any National Instruments hardware or software products related to this problem include the configuration forms from their user manuals Include additional pages if necessary Name Company Address Fax __ Phone ___ Computer brand Model Processor Operating system include version number Clock speed MHz RAM MB Display adapter Mouse ___ yes __no Other adapters installed Hard disk capacity MB Brand Instruments used Boards installed include revision and configuration LabVIEW Version VI Libraries installed other than standard libraries The problem is List any error messages The following steps reproduce the problem Document
29. LabVIEW SPC Toolkit Reference Manual 2 36 National Instruments Corporation Chapter 2 DEL DEL Iza J mr ie fae Control Chart VIs zone A The upper 3 standard error control limit value for the control chart zone B The upper 2 standard error control limit value for the control chart zone C The upper standard error control limit value for the control chart CL The center line value for the control chart zone C The lower 1 standard error control limit value for the control chart zone B The lower 2 standard error control limit value for the control chart zone A The lower 3 standard error control limit value for the control chart FEE EAE Given an array of control chart points arrays for the upper and lower control limits and the control chart limits cluster as created by the chart VIs creates a variable limits control chart XY graph indicator Use this VI with the u chart and p chart if you have a variable number n per unit inspected points UCL LCL 5 control chart lines control chart with var limits chart limits starting sample number 0 points The points to be plotted on the control chart normally the output of one of the control charts such as an u chart array UCL The variable upper limit to be drawn on the control chart LCL The variable lower limit to be drawn on the control chart chart limits This cluster is output by control chart VIs National
30. Manual Pareto Analysis VIs Chapter 4 Pareto Counter Given an unsorted list of causes and the number of occurrences for each cause sorts the list from the cause with the largest number of occurrences to the smallest and computes Pareto statistics for each cause causes pm Pareto values causes with count eee T total of occurrences causes with count An array of clusters for which the number of occurrences for each cause is already counted If the cause input is empty the VI calculates the Pareto values from the causes with the count input causes with count The number of occurrences of cause cause The name of the assigned cause The causes with count array has the number of occurrences for each cause counted If the causes input is empty the Pareto values are calculated from the causes with count input Pareto Values An array of clusters consisting of the following outputs cause frequency The number of occurrences of cause cumulative frequency The total of occurrences at the time this value was read percent of total The percent contribution of cause cumulative percent The total of percentages at the time this value was read sorted by frequency of occurrence of reach cause total of occurrences The total number of occurrences of all causes LabVIEW SPC Toolkit Reference Manual 4 2 National Instruments Corporation Chapter 4 Pareto Analysis VIs Pareto Chart Given a set of Pareto values o
31. VIEW features or the additional SPC Toolkit features to use when implementing an application Definitions of the SPC terms used in this overview appear in the Glossary at the end of this manual All examples that appear in this section are located in the SPC_EXMP 11b library Representation of Process Data in LabVIEW In SPC applications some key characteristics of the process are measured or counted and then tracked In this manual measurements of these processes are referred to as individual observations or individuals These measurements are often grouped into samples or subgroups The number of observations in a sample is referred to as the sample size also known as subgroup size Deciding which measurements to make how many and how often to make them and how they are grouped is beyond the scope of this manual See rational subgrouping in the sources cited in the Related Documentation section of About This Manual for more information on this topic In the SPC VIs for calculations on variable measured data samples consisting of a number of individual observations are handled as 2D arrays The arrays are set up where each row is a sample and the columns LabVIEW SPC Toolkit Reference Manual 1 8 National Instruments Corporation Chapter 1 Introduction to Statistical Process Control in LabVIEW contain the observations To use these VIs group your measured process data into appropriate 1D array samples subgroups and t
32. able the VI calculates the variable control limits National Instruments Corporation 2 3 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 A typical attributes chart VI the p Chart VI is shown in the following illustration chart limit sre Copt 7 samples in calc r units non conforming sa eel p fraction non conforming n sample size variable UCLp n sample size constant f 7 LELp std error multiplier 3 H bap chart limits index spec Copt i indices to ignore Copt The attributes chart V Is generate outputs for a single control chart Inputs are one or more 1D arrays that contain values counted from the process The output includes an array of points for the control chart and the chart limits In the case of the p chart shown in the preceding illustration and the u chart the sample size inspected may vary for each value of units non conforming or the sample size may be constant So you can choose one of the following two inputs a scalar input for a constant number inspected n or an array input for a variable number inspected n You should use only one of these two inputs The output arrays UCL and LCL are the variable control limits p and u charts only The chart limits cluster contains the average upper control limit UCL center line CL average lower control limit LCL and the standard error from which the VI calculates the upper and lower control limits The attribut
33. ach bin are handled The valid values for inclusion are 0 include the lower boundary 1 include the upper boundary 2 include both boundaries histogram specifies the resulting histogram axis specifies the center values for each bin of Histogram The centers of each bin are set according to the following equation and returned in the output array axis lower upper center i 7 National Instruments Corporation 3 7 LabVIEW SPC Toolkit Reference Manual Process Statistics VIs Chapter 3 outside is the output cluster outside contains three elements total Upon successful execution the element total will contain the total number of points in X not falling in any bin The elements above and below have meaning only if Bins are specified such that Bin 0 upper lt Bin 1 lower lt Bin 1 upper and so on above represents the number of values in X above Bin sizeof Bins 1 upper EA below represents the number of values in X below Bin 0 lower EA error No errors are returned This output maintains compatibility with the Advanced Analysis Library General Histogram VI Fit Nrml PDF to Histogram Given the bin centers from a histogram axis values output from the General HistogramVI the estimated sigma of the observations for the histogram and the total number of observations in the histogram calculates the height for a normal probability distribution function PDF that fits the histogram bin center
34. al Instruments Corporation 2 29 LabVIEW SPC Toolkit Reference Manual Control Chart VIs r il DEL 132 DBL Chapter 2 chart limit sre Copt samples in calc c defects sample c defects sample std error multiplier 3 c chart limits index spec Copt indices to ignore Copt c defects sample The number of non conformities or defects per sample inspected std error multiplier The multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 index spec Use this cluster to choose a range of samples in c to use for the control limit calculation start index Index of the first element of c to include in the control limit calculation The default is zero which is the index of the first sample in samples X array end index Index of the last element of c to include in the control limit calculation The default is zero which selects the last sample in c array If you do not wire this cluster the VI includes all elements in c input array in the control limit calculation indices to ignore Indices of c to exclude from the control limit calculation This is useful for eliminating out of control points from the control limit calculation By default this is an empty array samples in calc The number of samples used in the control limits calculation c non confor
35. al process limits calculated by the Process Mean and Sigma VI and the specification limits Figure 1 4 illustrates the block diagram for the Basic Histogram Plot VI example Samples Observations gt Upper Specification Limit Lower Specification Limit H histogram bins AE Histogram Upper Spec Limit Spec Mean Lower Spec Limit Upper Nat Limit Process Mean Lower Mat Limit 73 94 73 96 73 98 7400 74 02 74 04 74 06 process mean 74 004 process sigma pono National Instruments Corporation 1 11 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 Figure 1 4 Diagram for Basic Histogram Plot LERT process mean LEAT process sigma Another useful way to view the raw process data is on the tier chart also known as a tolerance diagram This plot charts the observations in each sample in a straight vertical line With this vertical line plot you can visualize the spread and location of the observations in each sample The Draw Tier Chart VI generates the tier chart for you as shown in Figure 1 5 Figure 1 6 illustrates the block diagram for the Basic Tier Chart VI Figure 1 5 Basic Tier Chart Upper Specification Limit Lower Specification Limit Haos Tier Chart Upper Spec Limit Spec Mean Lower Spec Limit Upper Mat Limit Process Mean Lower Mat Limit Observations
36. and S Chart Example 00 0 1 14 Figure 1 9 p Chart with Variable Limits VI Example 1 15 Figure 1 10 Diagram for p Chart with Variable Limits VI EXAtMple sieeve ect supvcss uessoass EEO oe etestess AOE EEE 1 15 Figure 1 11 X bar and R Chart Check Limits Example 1 16 Figure 1 12 Diagram for X bar and R Chart Check Limits Example a cct225 ce hula iis Spheclesvehs rae E E et 1 17 Figure 1 13 Zone Rule Test AT amp T WE Example ee 1 18 Figure 1 14 Diagram for Zone Rule Test AT amp T WE Example 1 18 Figure 1 15 Process Capability Example 1 sses 1 20 Figure 1 16 Diagram for Process Capability Example 1 1 20 Figure 1 17 Pareto Chart Example ec cee esecseeeeceeesseeneeeaes 1 21 Figure 1 18 Diagram for Pareto Chart Example 0 0 0 eee 1 21 National Instruments Corporation vii LabVIEW SPC Toolkit Reference Manual Introduction About This Manual The LabVIEW Statistical Process Control Toolkit Reference Manual describes the LabVIEW add on package you can use for implementing statistical process control functions Organization of This Manual This manual is organized as follows Chapter 1 Introduction to Statistical Process Control in LabVIEW contains installation instructions gives an overview of Statistical Process Control SPC and discusses the LabVIEW SPC Toolkit VIs and examples Chapter 2 Control Chart VIs descr
37. ard error The standard error associated with CLu 1a of E chart limit sre Specifies whether or not to use standard values for the chart limit calculations If unwired this defaults to the most common case where the chart limits are calculated from the data in the input array s You do not have to wire this cluster unless you want the chart limits to National Instruments Corporation 2 33 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 be calculated from standard values When using standard values the center line for the control chart u bar is set to u0 source Selects one of two sources for chart limits calculation 0 from data chart limits are calculated from the data in the input arrays as qualified by the index spec and indices to ignore inputs default selection 1 use std uO chart limits are calculated from the standard value u0 std u0 The standard u0 value to use when calculating chart limits from standard values The center line for the control chart u bar will then be set to u0 UCLu stderr mult f n CLu u LCLu stderr mutt f standard error E n LabVIEW SPC Toolkit Reference Manual 2 34 National Instruments Corporation Chapter 2 Control Chart VIs Draw Control Chart VIs DEL As described earlier in this chapter you use the draw control chart VIs for graphing control charts and raw process data Draw Control Chart Given an array of control
38. art run rules S s std dev chart sample or subgroup size sample specification limits standard values subdiagram subgroup subVI National Instruments Corporation Glossary A measure of the ability of a process to produce product within specification assuming the process is stable Specifically the variability that can be expected for a given process characteristic with respect to the specification limits for the characteristic Menus accessed from a menu bar Pull down menu options are usually general in nature Control chart that uses the sample range R to track the stability of the variation in the process Sample range is max sample value minus min sample value Sample size must be two or more Subtype of the numeric data type of which there are signed and unsigned byte word and long integers as well as single double and extended precision floating point numbers both real and complex A chart of the individual observations in a set of samples plotted in time order of occurrence Rules applied to a consecutive set of points on a control chart that are used to detect changes in the process such as out of control conditions or process shift Control chart that uses the sample standard deviation s to determine the stability of variation in the process Sample size must be two or more For measurement data this is the number of observations or individual measurements making up the sample Fo
39. art with Var Limits VI The front panel and block diagram of the p Chart with Variable Limits VI Example which uses the Draw Chart with Var Limits VI are shown in Figures 1 9 and 1 10 r units non conforming 10 12 i4 16 18 20 Detecting Out of Control Points and Process Shift After a variable or attribute chart VI calculates the control limits you can determine if the process is in control The most basic way to determine if a process is in control is to observe which points exceed the upper and National Instruments Corporation 1 15 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 lower control limits The Check Limits VI identifies the index of each sample that exceeds the process limits Figure 1 11 shows the Check Limits VI applied to the X bar chart in the X bar amp Range Chart Check Limits example its block diagram is illustrated in Figure 1 12 Notice that out of the given 40 samples 25 samples index zero to 24 are selected for calculating the control limits The VI calculates the points of the remaining samples for the graph but does not include them in the control limit calculation Figure 1 11 X bar Z Observations 7 amp Range Chart Check Limits Example ints Exceeded Limits Samples that exceeded limits T4014 LabVIEW SPC Toolkit Reference Manual 1
40. ation Comment Form National Instruments encourages you to comment on the documentation supplied with our products This information helps us provide quality products to meet your needs Title LabVIEW Statistical Process Control Toolkit Reference Manual Edition Date September 1994 Part Number 320753A 01 Please comment on the completeness clarity and organization of the manual If you find errors in the manual please record the page numbers and describe the errors Thank you for your help Name Title Company Address Phone Mail to Technical Publications Fax to Technical Publications National Instruments Corporation National Instruments Corporation 6504 Bridge Point Parkway MS 53 02 MS 53 02 Austin TX 78730 5039 512 794 5678 Glossary A Assignable Cause Attribute Data Attributes Chart B block diagram Boolean controls and indicators C c Chart A cause that can be detected and identified as contributing to process variation Data from counting process results such as number of units non conforming per inspected sample or number of defects per inspected sample containing n units As opposed to measured data attribute data has a discrete number of possible values p np u and c control charts are used to track attribute data A control chart that tracks whether a process is in control by tracking attribute data data c
41. chart points and the chart limits cluster as created by the chart VIs creates a control chart XY graph indicator with points plotted against upper and lower control limits and center line points ag control chart chart limits ha control chart lines starting sample number COJ points The points to be plotted on the control chart normally the output of one of the control chart VIs such as an X bar array chart limits This cluster is output by the control chart VIs UCL The upper control limit for the control chart CL The center line for the control chart LCL The lower control limit for the control chart standard error The standard error associated with CL ARIEL starting sample number The sample number of the first sample the VI uses to label the chart x axis If you do not wire this input sample labeling on the x axis will start at zero control chart A control chart XY graph with points and limit lines drawn You can wire this to the Basic Control Chart custom SPC control control chart lines This cluster is useful as a legend for the limit lines You can wire this to the Control Chart Lines custom SPC control UCL The upper control limit value for the control chart CL The center line value for the control chart FE National Instruments Corporation 2 35 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 LCL The lower control limit value for the control chart Draw Chart with
42. ded limits upper control limit ini out of control points lower control limit points The points plotted on the control chart normally the output of DBL one of the control chart VIs such as an X bar array es upper control limit The upper limit line from the control chart VI limits cluster lower control limit The lower limit line from the control chart VI limits cluster TE points exceeded limits TRUE if any of the points exceeded the limits given out of control points Lists the index of each point in the points array that exceeded the limits The out of control points are listed in order of how much each point exceeds the control limits The most extremely out of control point is listed first followed by the next most out of control point and so forth AE AE LabVIEW SPC Toolkit Reference Manual 2 42 National Instruments Corporation Chapter 2 DEL HABE Control Chart VIs Rule Checker AT amp T WE Applies AT amp T Western Electric run rules to the input points array Given a set of control chart points and the center line and std error from the control chart VIs this VI checks whether points are out of control or non randomly distributed according to the rules enabled rule 4a 4b points fore violations center line std error rule enable out of control points The front panel in the following illustration lists which rules you can enable The VI outputs the rules that are violat
43. displayed Figure 1 16 illustrates the block diagram for this example National Instruments Corporation 1 19 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 Figure 1 15 Process Capability Example 1 Samples Observations gt Histogram Upper Spec Limit Spec Mean Lower Spec Limit Upper Mat Limit Process Mean Lower Proc Limit tt Normal PDF 73 94 73 96 73 98 7400 7402 74 04 74 06 Figure 1 16 Diagram for Process Capability Upper Specification Limit Example 1 Lower Specification Limit process mean Pareto Analysis In SPC applications you often need to quantify and prioritize assignable causes that prevent a process from being in control or otherwise prevent a product from conforming to specifications You can assign causes to a sample when you detect samples being out of control from a control chart There are other things that can prevent a product from conforming to specifications that need to be analyzed such as tabulated results from product inspection You can totalize order and present causes using the LabVIEW SPC Toolkit Reference Manual 1 20 National Instruments Corporation Chapter 1 Introduction to Statistical Process Control in LabVIEW Pareto VIs Figure 1 17 shows the Pareto analysis and presentation example Pareto Chart Example Figure 1 18 ill
44. e Any action against National Instruments must be brought within one year after the cause of action accrues National Instruments shall not be liable for any delay in performance due to causes beyond its reasonable control The warranty provided herein does not cover damages defects malfunctions or service failures caused by owner s failure to follow the National Instruments installation operation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent acts and power failure or surges fire flood accident actions of third parties or other events outside reasonable control Copyright Under the copyright laws this publication may not be reproduced or transmitted in any form electronic or mechanical including photocopying recording storing in an information retrieval system or translating in whole or in part without the prior written consent of National Instruments Corporation Trademarks LabVIEW is a trademark of National Instruments Corporation Product and company names listed are trademarks or trade names of their respective companies WARNING REGARDING MEDICAL AND CLINICAL USE OF NATIONAL INSTRUMENTS PRODUCTS National Instruments products are not designed with components and testing intended to ensure a level of reliability suitable for use in treatment and diagnosis of humans Applications of National Instruments products involving medical or clinical treatment can create a
45. e display mode If you do not wire the display mode the VI automatically draws the specification limits and natural process limits upper spec limit The upper specification limit of the process lower spec limit The lower specification limit of the process process mean The estimated process mean See the description of the Process Mean and Sigma VI in this chapter for an explanation of how the process mean and process sigma is calculated process sigma The estimated process sigma PDF points to plot The number of points to create for the normal PDF plot In most cases you can leave this unwired By default 50 points are plotted PDF height The height to draw the PDF If zero the VI will draw the PDF with a height proportional to 1 process sigma corresponding to an area of one under the PDF curve When fitting a normal PDF to a National Instruments Corporation 3 9 LabVIEW SPC Toolkit Reference Manual Process Statistics VIs Chapter 3 histogram use the PDF height output from the Fit Normal PDF to Histogram VI HEL PDF width The width to draw the PDF in terms of sigma If unconnected the VI draws the PDF from 3 sigma to 3 sigma by default display mode Optional display mode specifier If you do not wire this cluster the specification limits and the natural process limits will be drawn by default This cluster contains the following inputs show spec limits If true the specification limits will be dra
46. e input sample data you select a subset of the array input to the Control Chart VI by wiring an index specifier The index specifier designates the start and end index of the samples the control chart limit calculations use You can also exclude specific samples from the control limit calculation by wiring an array of the sample indices to the indices to ignore input of the VI Doing this is useful when samples are detected to be out of control by one of the rule checking VIs The samples in calc output returns the actual number of samples the VI used to calculate the control limits If you do not wire either input the VI calculates the control limits from the entire input array Normally the control limits are calculated from the input sample data however the control chart VIs will calculate control limits based on standard values if you wire the chart limit sre input cluster National Instruments Corporation 2 1 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 The standard error multiplier input specifies the multiplier for the VI to use when calculating the upper and lower control limits normally three You do not need to wire this input unless you are using upper and lower control limits that are not at 3 0 standard errors Variables Chart VIs You use variables charts to detect out of control conditions on measured process values The VIs for creating variables charts generate outputs for two control chart
47. ed If true the VI detected one or more of the four patterns listed above in the control chart points with respect to the center line indicating a process shift El E first point of shift If process shift detected is true this outputs the index of the first point in the detected process shift This point can be used as the start index for recalculating control limits LabVIEW SPC Toolkit Reference Manual 2 46 National Instruments Corporation Chapter 2 ABE EE Control Chart VIs pattern If process shift detected is true this outputs the number of the first pattern 1 to 4 the VI found Sequence Checker Searches Boolean input array point exceeds bound for violations per run set to TRUE within run length Values in the point exceeds bound array are set to TRUE if they violate some rule limit Returns arrays with the index of each violation point and run length associated with that point You use this VI as a generic building block in the rule checker VIs point exceeds bound ra violation start point violations per run run length wiolation run length For example to test the rule four out of five points above two standard errors set violations per run to four and run length to five test whether each of the control chart points is greater than center line plus two standard errors and wire resulting boolean array to point exceeds bound input point exceeds bound Set each element to TRUE if point exceeds
48. ed along with the first point and length of the sequence of points violating the rule and a list of all points violating any of the enabled rules rule violations rule enable rule 4a 4b out of control points 4b Rule 1 One point outside 3 std errors Rule 2 Two out of three consecutive points outside 2 std errors Zone 4 or beyond Rule 3 Four out of five consecutive points outside 1 std errors Zone B or beyond Fule 4a Seven consecutive points on one side of the center line Rule 4b Eight consecutive points on one side of the center line points The points plotted on the control chart normally the output of one of the control chart VIs such as an X bar array center line The center line from the control chart VI limits cluster std error The standard error associated with CL from the control chart VI limits cluster rule enable The run rules to apply to the points array Each element of the array corresponds to a rule 1 2 3 4 from element 0 to 3 in that order National Instruments Corporation 2 43 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 see front panel for rule explanation Set the corresponding element to TRUE for each rule you want to apply An easy way to do this from the diagram is to use an unsigned 8 bit integer set the appropriate bits and then use the number for binary array conversion rule 4a 4b Selects rule 4a or 4b when rule 4 is enabled rule vio
49. encecerceeneceeneesaeeeneeees 2 7 X Bar GS CHALE ocvessesceshvoody cess septs suyeectecvepeussecesve votes 2 7 X Bar amp R Chart nnen a ei ei 2 11 Xe MR Charts oiner ieie eee NE E 2 14 mX bar amp MR Chatt oo ec ccecsseeeeeeceeeeeeeseeeeeenees 2 18 Single Point X Bar amp R S woe eee cece ceeeeeeeeeeee 2 22 Single Point x mX bar amp MR wo eeeeeeeeeee 2 23 Attributes Charts VIS irene ene irie a EE E R 2 24 Pehari eia Gan E E A E E RE E 2 24 Pips O De i p ARAE Ant ETNE TAE AE EEES EEE A E 2 27 Chart ert eea eee ea nied Nees 2 29 WCRart EAEE A AE E AATE 2 32 Draw Control Chart VIs s sssseeesesseeseesseesersseesressresreeerssreesessee 2 35 Draw Control Chart geeks aR es 2 35 Draw Chart with Zones eessseessssseessssessrssrsserssessresress 2 36 Draw Chart with Var Limits 20 0 0 ce eeeeeeeeeeeeeeeeeees 2 37 Draw Run Chart 2000 ceeecceeeeesseeecceceeeeeseceeeeenseeeseeees 2 38 Draw Tier Chant oerien r aen e AE E ENE EESE inas 2 40 Rule Check r VIs erreen ea ei ER RE 2 42 Check Control Limits sessseseesesseseessssseesessseeseessrssese 2 42 Rule Checker AT amp T WE sssseeseseisrreresrreerssree 2 43 Rule Checker Nelson ccccecesceceeseceeseseeeeseeeeeeeeees 2 44 Process Shift Detector essessessesseesesererserssreessesersee 2 46 Sequence Checker inre eter dueeetenesntentsaee 2 47 Chapter 3 Process Statistics VIS 0 00 0 cccccccccccccsesesesessssestessstesesnesees 3 1 Process Mean and Sigma sssee
50. erage range from n consecutive observations where n is sample size input By default n is set to two The Single Point X bar amp R S VI calculates points for sample mean and variation control charts one sample at a time and uses both the range and sample standard deviation calculations This VI is useful for calculating individual points for a control chart when generating control charts in real time It is still necessary to use the X bar amp s or X bar amp R VI for calculating the control limits The Single Point x mX bar amp mR VI calculates the individual points for an X and moving range or moving average and moving range control chart This VI is useful for calculating individual points for a control chart when generating control charts in real time It is still necessary to use the X amp mR or mX bar amp mR VI for calculating the control limits The variables control chart VIs are each described in more detail later in this chapter Attributes Chart VIs You use attributes charts to detect out of control conditions on process data that is counted such as the number of parts defective in a sample of n units inspected The attributes charts included in the SPC Toolkit are the following e pchart e np chart e cchart e uchart The attributes chart VIs take one or more one dimensional arrays as the input data The p chart and u chart can handle both a fixed sample size or variable sample sizes If the sample sizes are vari
51. es chart VIs are described in more detail later in this chapter VIs for Drawing Charts The control chart VI library contains several VIs for graphing control charts and raw process data You can also use the built in LabVIEW waveform chart and XY graphs to present SPC data The VIs in this library use the XY graph to draw limits against control chart points a format that is typical of SPC graph presentations The following illustration shows a typical diagram using the control charts and draw control charts VIs LabVIEW SPC Toolkit Reference Manual 2 4 National Instruments Corporation Chapter 2 Control Chart VIs nobar Chart Custom controls already preformatted for use with the VIs for drawing charts are available in the SPC Graphs amp Legends Control Menu VIs for Plotting Control Chart Points and Limits The control chart VIs calculate control chart limits and points The VIs in the following list generate a graph of center lines the upper and lower limit lines and the computed points from the control chart e Draw Control Chart to use with constant control limits this is your basic control chart graph e Draw Chart with Zones draws zones or warning limits from constant control limits useful for testing run rules e Draw Control with Var Limits to use with variable control limits p and u charts These VIs are described in more detail later in this chapter VIs for Creating Graphs of Raw Process Data
52. es to ignore inputs mR UCLx X stderr mul q J x E R for stderr mult 3 0 2 CLx x National Instruments Corporation 2 17 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 mR LCLx X stderr mutt q 2 j x E R for stderr mult 3 0 mR standard error 2 L d mR UCLmr mR stderr mult FP D mR for stderr mult 3 0 2 CLmr mR dmR LCLmr mR stderr mult a eal D3mR for stderr mult 3 0 2 d mR standard error d mX bar amp mR Chart Computes points and limits for mX bar and moving Range charts These are control charts for charting moving average and moving range This VI computes moving average and range over n observations By default nis 2 Optionally you can choose a range of indices for individuals to use and indices of individuals to ignore in the control calculation The actual number of individuals the VI uses to calculate the control limits is also output By default control limits are calculated from the input samples You can also calculate control limits from standard values by wiring the chart limit sre input chart limit sro opti a m bar bar amp mR bar d individuals i moring Average m bar index spec kopt af z Ho m bar chart limits indices to ignore kopt 7 moring Range mF std error multiplier 3 H mF chart limits n sample size C2 individuals in calc individuals x Individual observations or samples of subgroup
53. fier If unwired the VI will not draw the specification and natural process limits by default This cluster contains the following show spec limits If TRUE the VI will draw the specification limits on the chart The default is FALSE show natural process limits If TRUE the VI will draw the natural process limits on the chart The default is FALSE National Instruments Corporation 2 39 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 NP limit sigma The sigma multiplier for the natural DEL osx process limits By default this is 3 0 The natural process limits drawn on the chart will then be process mean NP limit sigma process sigma Note If you wire the display mode cluster to change one of the default settings you must specify all three elements run chart An XY graph with the individual observations in each sample plotted in order of occurrence Optionally the VI plots the upper and lower specification limits and the mean specification value and or the natural process limits and process mean against the sample plots You can wire this to the Run Chart with Limits custom SPC control Draw Tier Chart Draws a tier chart also known as a tolerance diagram Plots the spread of the observations in each sample Optionally the specification limits and or the natural process limits are also plotted against the observations starting sample number 0 Samples upper spec limit lower spec limi
54. gend custom SPC control National Instruments Corporation 4 3 LabVIEW SPC Toolkit Reference Manual Pareto Analysis VIs Chapter 4 Cause Code Lookup Given an unsorted list of numeric cause codes an array of numbers and a cause code lookup list containing the cause string for each cause code returns a sorted list of causes with the count of the number of occurrences of each cause cause codes f causes with count code lookup table cause codes Array of 32 bit integers code lookup table An array of clusters consisting of the following cause code The code for cause cause name String associated with the cause code causes with count An array of clusters consisting of the following causes on count The number of occurrences of cause cause Name of cause LabVIEW SPC Toolkit Reference Manual 4 4 National Instruments Corporation Chapter 4 ARARE 132 Pareto Analysis VIs Array to Bar Comb Graph Makes a vertical bar graph from a single array of numbers The X axis values begin at x with increments of dx The width of the bars can be between 0 single line comb plot to 100 percent space between bars The Pareto Graph VI uses this general purpose bar graph as a subVI width 100 y Array xo 0 0 dx 1 0 baseline 0 0 alignment CO Left width Width of bar in percent Default is 100 percent y Array An array of heights for each bar Xo The reference point of first
55. hart with Var Limits VI Control Chart show pts not in control A pre formatted X Y graph useful for highlighting out of control points See the example VI X bar amp S Chart correct limits in SPC_EXMP 11b for a demonstration of how to use this type of graph format Control Chart with Zones show pts A pre formatted X Y graph useful for highlighting out of control points on a Control Chart with Zones See the example VI Zone Rule Test Nelson Example in SPC_EXMP 11b for a demonstration of how to use this type of graph format Control Chart and Limits cluster A cluster containing a pre formatted X Y graph and three numeric indicators for the control chart lines This is a useful organization and grouping for a control chart and limit values Run Chart with Limits A pre formatted X Y graph for use with the Draw Run Chart VI Tier Chart A pre formatted X Y graph for use with the Draw Tier Chart VI Histogram Bar Graph with Limits A pre formatted X Y graph for use with the Draw Vertical Bar Graph with Limits VI Normal PDF Graph with Limits A pre formatted X Y graph for use with the Normal PDF Graph with Limits VI Histogram and Normal PDF Plot A pre formatted X Y graph for use with histogram and superimposed normal PDF plot with limits See the example VI Proc Cap Example 2 in SCP_EXMP 11b fora demonstration of how to use this type of graph format Pareto Chart A pre formatted X Y graph for use with either Pa
56. harts one point at a time while you are collecting samples You must continue to use the X bar amp R or X bar amp s Chart VIs to calculate the control limits for the chart range R Std dew s sample X Sample on which to compute the control chart points sample X contains two or more individual observations X bar The mean of the input sample Wire this output to the waveform chart to create an X bar control chart range R The range of the input sample Wire this output to the waveform chart to create an range R control chart std dev S The sample standard deviation of the input sample Wire this output to the waveform chart to create an s control chart LabVIEW SPC Toolkit Reference Manual 2 22 National Instruments Corporation Chapter 2 Control Chart VIs Single Point x mX bar amp mR Computes single points for the x and moving range or moving average and moving range control charts Computing single points is useful for plotting control charts one point at a time while you are collecting samples You must still use the x amp mR Chart or mX bar amp mR Chart VIs to calculate the control limits for the chart This VI is reentrant so that you can use multiple copies Each time it is called this VI saves a copy of the previous n 1 individuals to use in calculating the next moving Average and Range individual x gent individual x n sample size 2 pt moving A erage mx bar moring Range mE valid mX bar mR
57. hat track whether a process is in control by tracking mean and variability of samples of measured data Variables charts include X bar and s X bar and R x and mR charts and mX bar and mR charts Special file that contains a collection of related VIs for a specific use A numeric plotting indicator modeled after a paper strip chart recorder which scrolls as it plots data Data path between nodes Tool used to define data paths between source and sink terminals Control chart that uses the individual observations from a process to track the stability of the process mean This type of control chart is typically used when sample size is one Control chart that uses the sample mean X bar to track the stability of the process mean Sample size must be two or more G 6 National Instruments Corporation
58. he LabVIEW Functions and Controls menus will contain SPC entries the next time you launch LabVIEW National Instruments Corporation 1 1 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 SPARCstation You can install the SPC Toolkit as shown in the following steps You do not need root privileges to install the SPC Toolkit but you must be able to write to the LabVIEW directory where the SPC Toolkit will be installed On systems running Solaris 2 2 or later you must determine whether your system is running the volume manager by entering the following command ps a fgrep vold The following message usually appears to tell you that the volume manager is running 14818 pts 9 S 0 01 usr sbin vold If volume manager is running install the SPC toolkit as follows 1 Use the cd command to change to a directory where you have write permission such as var tmp or your home directory 2 Insert the first SPC Toolkit disk into the 3 5 in disk drive 3 Type volcheck 4 Typetar xf vol dev aliases floppy0 INSTALL to extract the installation script 5 Torun the installation script type INSTALL Follow the instructions on the screen The installer will prompt you to name the directory that contains LabVIEW and its associated files If volume manager is not running or if your system runs Solaris 1 install the SPC toolkit as follows 1 Use the cd command to change to a
59. hen group the samples together to form a 2D array All samples in a 2D array must be the same size The control chart VIs automatically calculate sample size by measuring the width of the 2D array You can use the LabVIEW Reshape Array function to convert a 1D array to a 2D array If you have a sample subgroup size of one you can keep your data in 1D arrays In this case you will be limited to using the X amp moving Range chart or mX bar amp moving Range VIs Attribute data such as number of defects per unit are handled as 1D arrays There are two ways you can graphically present your measured data in LabVIEW as you acquire each data point or sample and after you have acquired a collection of samples Lab VIEW has several standard methods for viewing process data Three basic graph types the waveform chart the waveform graph and the XY graph are all useful to you You can implement a run chart a plot of the individual observations plotted in time order by wiring a 1D array containing your observations to the standard waveform graph If you want to monitor your incoming data one point at a time use a waveform chart If you are plotting all the points at once you can use a waveform graph SPC charts typically plot process data against reference lines which may be specification limits control chart limits or some other useful reference In LabVIEW you can use an XY graph to plot a set of points and reference lines by spec
60. his input is ignored unless the sample size number of columns in the input array samples X is one in which case the moving range is used as a basis for estimating process mean and sigma n for moving Range ranges from 2 to 25 By default n for moving Range is set to 2 LabVIEW SPC Toolkit Reference Manual 3 2 National Instruments Corporation Chapter 3 DEL DEL rm ir b j DEL DEL E Process Statistics VIs Compute Process Capability Given the specification limits and the process mean and process sigma computes the process capability ratios Cp Cpk and Cpkm as well as the estimated process fraction non conforming in parts per million ppm Notice that the fraction non conforming is valid only if the process is normally distributed Computes one sided upper and one sided lower in addition to two sided process capability ratios and fraction non conforming mode upper spec limit lower spec limit process mean i process sigma H fraction non conf ppm sigma tolerance 6 p U amp L fraction non conf Cppmi upper spec limit The upper specification limit of the process lower spec limit The lower specification limit of the process process mean The estimated process mean See the description of the Process Mean and Sigma VI in this chapter for an explanation of how the values for process mean and process sigma are calculated process sigma The estimated process sigma mode Selects whether to calc
61. ht given in the histogram input and centered at the values given in the bin centers input National Instruments Corporation 3 13 LabVIEW SPC Toolkit Reference Manual Process Statistics VIs Chapter 3 Rotate Graph Given a multiplot XY graph transposes the X and Y values so that the graph is rotated clockwise 90 multi plot X Y graph You can use this general purpose VI to rotate any XY graph It is particularly useful for plotting horizontal histograms and normal distributions when comparing them against the Y axis of control charts Eo multi plot X Y graph An array of clusters of an array of clusters containing X X value of point i Y Y value of point This array is equivalent to an X Y multi plot graph ona rotated X Y graph An array of clusters of an array of clusters containing X X value of point i Y Y value of point This array is equivalent to a multi plot graph in which the input X and Y values have been transposed LabVIEW SPC Toolkit Reference Manual 3 14 National Instruments Corporation Chapter doogogoogoooog Pareto Analysis VIs This chapter describes the Pareto analysis VIs which include the Pareto Counter VI the Pareto Chart VI and the Cause Code Lookup VI The Array to Bar Comb VI which the Pareto Analysis VIs use as a subVI is also included e Pareto Counter given either an unsorted list of causes or a list of causes and corresponding coun
62. ibes the control chart VIs which include the variables charts attributes charts chart drawing and rule checking VIs The control chart VIs compute control limits for control charts create control chart graphs and apply rules to control chart data that detect out of control conditions Chapter 3 Process Statistics VIs describes the process statistics VIs which are useful for process capability analysis and for viewing and measuring process distribution Chapter 4 Pareto Analysis VIs describes the Pareto analysis VIs which include the Pareto Counter VI the Pareto Chart VI and the Cause Code Lookup VI The Array to Bar Comb VI which the Pareto Analysis VIs use as a subVI is also included The Appendix Customer Communication contains forms you can use to request help from National Instruments or to comment on our products and manuals The Glossary contains an alphabetical list and description of terms used in this manual including abbreviations acronyms metric prefixes mnemonics and symbols National Instruments Corporation ix LabVIEW SPC Toolkit Reference Manual About This Manual Conventions Used in This Manual The following conventions are used in this manual bold italic bold italic monospace A Warning Caution Note LabVIEW SPC Toolkit Reference Manual Bold text denotes menus menu items and VI input and output parameters Italic text denotes emphasis a cross reference or an
63. ification Limit Run Chart Individuals Upper Spec Limits Spec Mean Lower Spec Limit ce ida CLAS al Upper Nat Lim Process Mean Lower Mat Lim 100 120 140 160 180 200 Another useful reference for viewing the raw process data is the natural process limits calculated from the average mean and sigma of the group of samples The natural process limits measure the distribution of the process data The natural process limits are typically the process mean 3 0 process sigma The Process Mean and Sigma VI in the process LabVIEW SPC Toolkit Reference Manual 1 10 National Instruments Corporation Chapter 1 Figure 1 3 Basic Histogram Plot Introduction to Statistical Process Control in LabVIEW statistics library estimates the process mean and sigma from the process samples For viewing the distribution of your data a histogram is useful The General Histogram VI computes a histogram automatically estimating a reasonable number of bins based on Sturges rule You can also choose the number of bins or specify bin sizes LabVIEW then plots the histogram using the Vertical Bar Graph VI and an XY graph You can superimpose the specification limits on the histogram which the Vertical Bar Graph with Limits VI does for you Figure 1 3 shows a basic histogram plot of the individual observations in the 2D samples array plotted against both the natur
64. ifying the reference lines as X Y pairs The LabVIEW SPC Toolkit automatically generates these types of XY graphs for you The SPC Toolkit includes a set of custom SPC controls including XY graphs that are preformatted for various types of SPC charts and chart legends These charts are preformatted to work with the SPC VIs that create SPC graphs If you are updating a waveform chart one point at a time you can group each point into a cluster with the reference points and wire the cluster to your waveform chart Viewing Raw Process Data It is useful to view your raw process data before calculating control limits and plotting control charts The SPC VIs provide three methods for National Instruments Corporation 1 9 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 Figure 1 1 Basic Run Chart Figure 1 2 Diagram for Basic Run Chart viewing your raw process data a basic run chart a histogram and a tier chart An example of a basic run chart is illustrated in Figure 1 1 A run chart is a plot of the individual measurements plotted in time order It is displayed on an XY graph and generated by the Draw Run Chart VI The specification limits are shown against the individuals in the example The block diagram for the example VI Basic Run Chart is illustrated in Figure 1 2 Samples Observations gt oso Afs l arze rze i Upper Specification Limit Lower Spec
65. in the samples X input array in the control limit calculation indices to ignore Indices of samples to exclude from the control limit calculation Excluding samples is useful for eliminating out of control points from the control limit calculation By default this is an empty array std error multiplier The standard error multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 X bar bar This is an estimate of the process mean based on the grand average of the samples included in the control limit calculation If the control limits are calculated from standard values this is set to the standard mean X bar The mean of each input sample This is the array plotted on the X bar control chart X bar chart limits This cluster contains the limits for the X bar chart UCLx The upper control limit for the X bar chart CLx The center line for the X bar chart Clx X bar bar or standard mean and is also the estimated process mean if calculated from the input samples EE LCLx The lower control limit for the X bar chart Ble standard error The standard error associated with CLx range R The range of each input sample This is the array plotted on the R control chart R chart limits This cluster contains the limits for the Range chart UCLr The upper control limit for the R chart
66. include XY graphs specially preformatted to match the multiplot XY graphs output by the various SPC subVIs The following illustration shows the SPC Graphs amp Legends palette with a set of custom controls for use with the SPC Toolkit VIs Numeric Boolean String Array Cluster Graph Path RefNum Decorations Control tl The custom controls are installed as part of SPC Toolkit These custom controls are pre formatted and labeled X Y graphs and legends for wiring directly to the outputs of the drawing VIs for control charts process statistics and Pareto analysis They are as follows Basic Control Chart A pre formatted X Y graph for use with the Draw ead Control Chart VI I Control Chart Lines cluster A cluster displaying values for the control chart lines for use as a legend with all the drawing VIs for control charts a Control Chart with Zones A pre formatted X Y graph for use with the Beare Draw Control Chart with Var Limits VI mL Control Chart Zones cluster A cluster displaying values for the control m chart zones A B and C for use as a legend with the Draw Control Chart with Zones VI LabVIEW SPC Toolkit Reference Manual 1 6 National Instruments Corporation Chapter 1 ra En Ee EE wat H E E LabVIEW SPC Toolkit Examples Introduction to Statistical Process Control in LabVIEW Control Chart with Var Limits A pre formatted X Y graph for use with the Draw Control C
67. individuals x i x i 7 1 where n is the sample size This is the array plotted on the x control chart mX bar chart limits This cluster contains the limits for the moving average chart UCLmx The upper control limit for the moving average chart CLmx The center line for the x control chart Clmx x bar bar or standard mean and is also the estimated process mean if calculated from the input individuals LCLmx The lower control limit for the moving average chart Ae oa standard error The standard error associated with CLmx National Instruments Corporation 2 19 LabVIEW SPC Toolkit Reference Manual Control Chart VIs DBL Chapter 2 moving range mR The moving range of individuals x i x i 7 1 where n is the sample size This is the array plotted on the mR control chart mR chart limits This cluster contains the limits for the mR chart UCLmr The upper control limit for the mR chart CLmr The center line for the mR control chart Clmr mR bar if calculated from the input data individuals or standard RO or standard sigma d2 LCLmr The lower control limit for the mR chart standard error The standard error associated with CLmr HE BE individuals in calc The number of individuals the VI uses in the control limits calculation chart limit src Specifies whether or not to use standard values for the chart limit calculations If unwired this defaults to the common case where
68. introduction to a key concept Italic text also denotes a variable such as filename or N when it appears in a text passage Bold italic text denotes a note caution or warning Monospace font denotes text or characters that you enter using the keyboard File names directory names drive names sections of code programming examples syntax examples and messages and responses that the computer automatically prints to the screen also appear in this font This icon to the left of bold italicized text denotes a warning which alerts you to the possibility of damage to you or your equipment This icon to the left of bold italicized text denotes a caution which alerts you to the possibility of data loss or a system crash This icon to the left of bold italicized text denotes a note which alerts you to important information x National Instruments Corporation LabVIEW Data Types About This Manual Each VI description gives a data type picture for each input and output parameter as illustrated in the following table Control Data Type HAEREERE RE EADAE ANTAARBARBAERN Signed 8 bit integer Signed 16 bit integer Signed 32 bit integer Unsigned 8 bit integer Unsigned 16 bit integer Unsigned 32 bit integer Single precision floating point number Double precision floating point number Extended precision floating point number String Boolean Array of signed 32 bit integers Cluster File
69. ion 1 use std mean RO chart limits are calculated from standard values for mean and sample standard variation 2 use std mean sigma chart limits are calculated from standard values for mean and sigma std mean The standard mean value to use when calculating chart limits from standard values std RO sigma The standard RO or sigma value to use in calculating chart limits from standard values The control limit calculations for the chart limits are as follows If standard values are used for the control limit calculations then X X bar bar is set to std mean R R bar is set to std RO or std sigma d2 otherwise X and R are calculated from the input samples as specified by the index spec and indices to ignore inputs National Instruments Corporation 2 13 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 UCLx X stderr mul R X A R for stderr mult 3 0 d n CLx X LCLx X stderr matt R d n X A R for stderr mult 3 0 R d standard error a d R 2 UCLr R stderr mult D R for stderr mult 3 0 2 CLr R d R LCLr R stderr mult S5 D R for stderr mult 3 0 d dR standard error d X amp mR Chart Computes points and limits for individuals x and moving Range charts These are control charts for charting mean and moving range This VI computes for a moving range from n consecutive observations By default n
70. ion The VI outputs the actual number of samples it uses to calculate the control limits Use the Range Chart for samples or subgroups of 25 or less because for sample size of ten or more the sample range loses efficiency of sample variance For sample sizes of ten or larger you should use the X bar amp s Chart VI instead of Range Chart chart limit sre opt samples X index spec kopt 1 io bar chart limits indices to ignore Copt g Range R std error multiplier 2 B F chart limits R bar de samples in cale samples X Samples on which to compute control limits and points for the X bar and Range charts Each row is a sample with n observations where n is the number of columns in the 2D array N is also known as the subgroup size The maximum sample subgroup size permitted is 25 the minimum is 2 index spec Use this cluster to choose a range of samples to use for the control limits calculation start index Index of the first sample to include in the control limit calculation Default is zero which is the index of the first sample in samples X array end index Index of the last sample to include in the control limit calculation Default is zero which selects the last sample in samples X array National Instruments Corporation 2 11 LabVIEW SPC Toolkit Reference Manual Control Chart VIs J E E J D DEL Chapter 2 If you do not wire this cluster the VI includes all the samples
71. is is an estimate of the process mean based on the average of the moving averages included in the control limit calculation If the control limits are calculated from standard values this is set to the standard mean mR bar d2 This is an estimate of the process sigma based on the average of the moving ranges included in the control limit calculation If the control limit s are calculated from standard values this is set to the standard RO d2 or the standard sigma The control limit calculations are as follows If standard values are used for the control limit calculations then X X bar is set to std mean mR mR bar is set to std RO or std sigma d2 otherwise X and mR are calculated from the input samples as specified by the index spec and indices to ignore inputs UCLx X stderr mult R X A R for stderr mult 3 0 d 4n CLx X LCLx X stderr mutt R d 4n aX A R for stderr mult 3 0 R d n standard error d mR UCLmr mR stderr mult q D mkR for stderr mult 3 0 2 National Instruments Corporation 2 21 LabVIEW SPC Toolkit Reference Manual Control Chart VIs DEL AEE Chapter 2 CLmr mR d mR nen LCLmr mR stderr mult q D mR for stderr mult 3 0 2 d mR standard error dz Single Point X Bar amp R S Computes single points for both X bar and Range or X bar and s control charts Computing single points is useful for plotting control c
72. istical Process Control in LabVIEW Installation Windows This chapter contains the installation procedure gives an overview of Statistical Process Control SPC and discusses the LabVIEW SPC Toolkit VIs and examples The following sections contain instructions for installing the SPC Toolkit on Windows Sun SPARCstation and Macintosh The SPC Toolkit comes in compressed form on floppy disks Installing the SPC Toolkit requires approximately 4 MB You can install the SPC Toolkit from the DOS prompt the Windows File Manager or with the Run command from the File menu of the Program Manager 1 Insert the first SPC Toolkit disk into the 3 5 in disk drive and run the SETUP EXE program using one of the following three methods a From Windows select Run from the File menu of the Program Manager A dialog box appears Type X SETUP where X is the proper drive designation Press lt enter gt or select OK b From Windows launch the File Manager Click on the drive icon that contains the installation disk Find SETUP EXE in the list of files on that disk and double click on it 2 After you choose an installation option follow the instructions that appear on the screen The installer will prompt you to name the directory that contains LabVIEW and its associated files After you install the LabVIEW SPC Toolkit your LabVIEW directory should contain a new SPC directory and t
73. its for the s chart UCLs The upper control limit for the s chart CLs The center line for the s chart Cls s bar if calculated from the input samples or is standard s0 or standard sigma c4 LCLs The lower control limit for the s chart HE BE standard error The standard error associated with CLs s bar c4 This is an estimate of the process sigma standard deviation based on the average standard deviation of the samples included in the control limit calculation samples in calc The number of samples the VI used in the control limits calculation If the control limits are calculated from standard values this is set to standard s0 c4 or sigma chart limit src Specifies whether or not to use standard values for the chart limit calculations If unwired this cluster defaults to the common case where the chart limits are calculated from the data in the input sample array You do not have to wire this cluster unless you want the chart limits to be calculated from standard values When using standard values the center line for the X bar control chart X bar bar is set to std mean and the center line for the s control chart s bar is set to std s0 or std sigma c4 source Selects one of three sources for chart limits calculation 0 from data chart limits are calculated from the data in National Instruments Corporation 2 9 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 the samples X arra
74. lations This cluster lists the rules being violated and which sequence of points violated the rule rule The rule violated 1 4a and so forth first point The index of the first point of the sequence of points violating the given rule run length The length of the sequence of points violating the given rule out of control points Lists the index of each point in the points array that the VI identified as out of control according to the applied rules Rule Checker Nelson Applies Nelson tests to the input points array Given a set of control chart points and the center line and std error from the control chart VIs this VI will check whether points are out of control or non randomly distributed according to the enabled Nelson tests points center line Std error test enable tests flagged out of control points The front panel in the following illustration lists which tests you can enable The VI outputs the rules that are violated along with the first point and length of the sequence of points violating the tests and a list of all points violating any of the enabled tests LabVIEW SPC Toolkit Reference Manual 2 44 National Instruments Corporation Chapter 2 DEL H BBE Control Chart VIs points tests flagged center line Heo std error 0 00 test out of control points Test 1 One point beyond Zone A 3 std errors Test 2 Nine points in a r
75. lier 2 lower MPL samples X Samples on which to compute process mean and process sigma Each row is a sample with n observations where n is the number of columns in the 2D array To calculate process mean and sigma on a 1D array use the array builder primitive to create a 2D array and then wire to the samples X input type s R Type of process sigma computation to perform National Instruments Corporation 3 1 LabVIEW SPC Toolkit Reference Manual Process Statistics VIs Chapter 3 s base process sigma estimate on mean sample standard deviation default R base process sigma estimate on mean sample range Note If sample size is 1 process sigma estimate is based on mean moving range sigma multipler The sigma multiplier for calculating upper NPL and lower NPL By default sigma is multiplied by 3 0 process mean Mean of the process estimated from X bar bar or x bar if sample size is one AEE process sigma The sigma of the process estimated from Ss P if type is S C4 R if type is r or d mR if sample size is 1 d upper NPL The upper natural process limit of the process computed as process mean sigma multiplier process sigma By default this is process mean 3 0 process sigma lower NPL The lower natural process limit of the process computed as process mean sigma multiplier process sigma By default this is process mean 3 0 process sigma H E n for moving Range T
76. limit P 0 5 sigma tolerance process sigma By default 0 5 sigma tolerance 3 0 Cp The process capability index also known as PCR or PCI Cp Upperspec limit lower spec limit p sigma tolerance process sigma Cp is always calculated with respect to both the upper and lower specification limits By default sigma tolerance 6 0 Cpk The centered capability ratio also known as the Cpk index Cpk MIN CpU CpL Cpkm A centered process capability ratio upper spec limit lower spec limit CpU sigma tolerance tau where tau upper spec limit lower spec imin process sigma process mean 5 LabVIEW SPC Toolkit Reference Manual 3 4 National Instruments Corporation Chapter 3 sus gt Process Statistics VIs fraction non conf The estimated fraction non conforming in parts per million based on a normal process distribution U amp L fraction non conf This cluster contains the estimated fraction non conforming in parts per million above and below the specification limits raction gt The estimated fraction non conforming in fraction gt USL The estimated fract fi parts per million above the upper spec limit based on a normal process distribution fraction lt LSL The estimated fraction non conforming in parts per million below the lower spec limit based on a normal process distribution Note Ifyour process distribution is not normal the fraction non conforming estimates a
77. mX bar mR is set to FALSE Attributes Chart VIs As described earlier in this chapter you use the attributes chart VIs to detect out of control conditions on counted process data p chart Computes points and limits for a p chart a control chart for fraction non conforming Number of units inspected n can be constant for all r or vary for each element of r Calculates both variable and constant chart limits Optionally you can choose a range of indices for samples to use and indices of samples to ignore in the control calculation The actual number of samples the VI uses to calculate the control limits is also output By default control limits are calculated from the input samples You can also calculate control limits from standard values by wiring the chart limit src input chart limit sro Copt samples in calc r units non conforming sa arreman p fraction non conforming n sample size variable UCLp n sample size constant 4 LCLp std error multiplier 3 H oo chart limits index spec Copt i indices to ignore Copt r units non conforming sample unit The number of units non conforming in each sample inspected LEA n sample size variable The number of units inspected per sample for each value of r Use this array if a variable number of units were inspected for each entry in r The array length must be the same the length of the array r n sample size constant Use this input if the same number
78. ming in each input sample This is the array plotted on the p control chart UCLp The variable limit for the upper control limits If std error multiplier is three this will be p bar 3 standard errors The standard error calculation varies with n LCLp The variable limit for the lower control limits If std error multiplier is three this will be u bar 3 standard errors The standard error calculation varies with n p chart limits This cluster contains the constant limits for the p chart average UCLp The average value of the variable upper control limit for the p chart If the number inspected is constant use this for the upper control limit CLp The center line for the p chart p bar or standard p0 p bar is the estimated fraction non conforming for the process if calculated from the input data National Instruments Corporation 2 25 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 DEL LCLp The average value of the variable lower DBL average p 2 a control limit for the p chart If the number inspected is constant use this for the lower control limit standard error The standard error associated with CLp chart limit src Specifies whether or not to use standard values for the chart limit calculations If unwired this defaults to the most common case where the chart limits are calculated from the data in the input array s You do not have to wire this cluster unless you want the cha
79. mit for the mR chart CLmr The center line for the mR control chart Clmr mR bar if calculated from the input data individuals or standard RO or standard sigma d2 LCLmr The lower control limit for the mR chart HE BE standard error The standard error associated with CLmr mR bar d2 This is an estimate of the process sigma standard deviation based on the average of the moving range between individuals included in the control limit calculation individuals in calc The number of individuals the VI uses in the control limits calculation chart limit sre Specifies whether or not to use standard values for the chart limit calculations If unwired this defaults to the common case where the chart limits are calculated from the data in the input individuals array You do not have to wire this cluster unless you want the chart limits to be calculated from standard values When using standard values the center line for the x control chart x bar is set to std mean and the center line for the mR control chart mR bar is set to std RO or std sigma d2 source Selects one of three sources for chart limits calculation 0 from data chart limits are calculated from the data in the individuals x array as qualified by the index spec and indices to ignore inputs default selection 1 use std mean RO chart limits are calculated from LabVIEW SPC Toolkit Reference Manual 2 16 National Instruments Corporation Chapter 2 Co
80. mities inspection unit The number of non conformities or defects found per sample unit This is identical to the input array c These are the points plotted on the c control chart c chart lines This cluster contains the limits for one c chart UCLe The upper control limit for the c chart If std error multiplier is three this will be c bar 3 standard errors LabVIEW SPC Toolkit Reference Manual 2 30 National Instruments Corporation Chapter 2 Control Chart VIs CLc The center line for the c chart c bar or standard c0 c bar is the estimated number of non conformities for the process if calculated from the input data LCLe The lower control limit for the c chart If std error multiplier is three this will be np bar 3 standard errors standard error The standard error associated with CLc chart limit src Specifies whether or not to use standard values for the chart limit calculations If unwired this defaults to the most common case where the chart limits are calculated from the data in the input array You do not have to wire this cluster unless you want the chart limits to be calculated from standard values When using standard values the center line for the control chart c bar is set to c0 source Selects one of two sources for chart limits calculation 0 from data chart limits are calculated from the data in the input arrays as qualified by the index spec and indices to ignore inputs default selection
81. n 0 from data chart limits are calculated from the data in the input arrays as qualified by the index spec and indices to ignore inputs default selection LabVIEW SPC Toolkit Reference Manual 2 28 National Instruments Corporation Chapter 2 Control Chart VIs 1 use std pO chart limits are calculated from the standard value p0 std p0 The standard pO value to use when calculating chart limits from standard values The center line for the control chart n p bar will then be set to n p0 The control limit calculations are as follows If standard values are used for the control limit calculations then np bar is set to std n p0 otherwise np bar is calculated from the input samples as specified by the index spec and indices to ignore inputs r p at array oi if calculated from input data otherwise p p0 UCLnp nx P stderr mult np 1 p CLnp nxp LCLnp nx p stderr mult np 1 p standard error Jnp 1 p c Chart Computes points and limits for a c chart a control chart for number of non conformities or defects Optionally you can choose a range of indices for samples to use and indices of samples to ignore in the control calculation The actual number of samples the VI uses to calculate the control limits is also output By default control limits are calculated from the input samples You can also calculate control limits from standard values by wiring the chart limit sre input Nation
82. nd DEL Sigma VI or the Sample Statistics VI to calculate this value points to plot The number of points to create for the PDF plot Normally you can leave this unwired By default 50 points are plotted J A EE PDF height The height to draw the PDF If 0 the VI will draw the PDF with a height proportional to 1 sigma corresponding to an area of 1 under the PDF curve When fitting a normal PDF to a histogram use the PDF height output from the Fit Normal PDF to Histogram VI PDF width The width to draw the PDF in terms of sigma By default the width is 3 and the VI draws the PDF from 3 sigma to 3 sigma normal PDF values XY values making up the PDF plot An array of clusters made up of the following inputs X The X value of each normal PDF plot point Y The Y axis value of each normal PDF plot point This output can also be treated as an XY graph output you can wire it directly to an XY graph E normal PDF graph An XY graph of a normal PDF with the specified height width and number of points National Instruments Corporation 3 11 LabVIEW SPC Toolkit Reference Manual Process Statistics VIs DEL JBE DEL DBL Chapter 3 Vertical Bar Graph with Limits Creates a vertical bar graph centered at each of the bin centers x and plots the specification limits and natural process limits as vertical lines against the bar graph This type of bar graph is useful for viewing the results of a hi
83. ntrol you can calculate its capability which is a predictor of the process performance as long as the process remains in control It is misleading to perform these computations unless your process is in control If it is not in control process capability analysis is no longer predictive but can still characterize the past performance of your process Two common measures of process capability are the process capability index PCI or Cp which measures the process variability with respect to the specification limits and the centered capability index or Cpk which measures how centered the process is with respect to the specification limits The Compute Process Capability VI performs these calculations If your process is normally distributed you can estimate the process fraction non conforming in parts per million The Compute Process Capability VI performs this computation but is invalid unless the process is normally distributed One method for determining whether your process is normally distributed is to view a histogram of the observations against a normal curve fitted to the histogram It is useful to visualize the distribution of the process relative to the specification limits Figure 1 15 shows a histogram of the process observations against the specification limits and natural process limits A normal distribution curve is fitted to the histogram The process capability measures Cp Cpk and reject rate are also calculated and
84. ntrol Chart VIs standard values for mean and range 2 use std mean sigma chart limits are calculated from standard values for mean and sigma std mean The standard mean value to use when calculating chart limits from standard values std RO sigma The standard RO or sigma value to use in calculating chart limits from standard values n sample size The number of consecutive individual values to use in the moving range calculation n sample size may range from 2 to 25 By default n sample size is 2 x bar amp mR bar d2 This cluster contains estimates on process mean and sigma based on individuals included in the control limit calculation or on standard values x bar This is an estimate of the process mean based on the average of the individuals included in the control limit calculation If the control limits are calculated from standard values this is set to the standard mean mR bar d2 This is an estimate of the process sigma based on the average of the moving ranges included in the control limit calculation If the control limits are calculated from standard values this is set to the standard RO d2 or the standard sigma The control limit calculations are as follows If standard values are used for the control limit calculations then x x bar is set to std mean mR mR bar is set to std RO or std sigma d2 otherwise X and mR are calculated from the input samples as specified by the index spec and indic
85. o assignable causes of variation are present Front panel object that displays output A single measurement of a process characteristic Two dimensional array Data that is a result of observations or measurements of a characteristic that has a continuous range As opposed to attribute data measurement data is not discrete that is any discreteness in measurement data is due to the resolution of the measuring device not the characteristic Control chart that uses the average of n successive individual observations from a process to track the stability of the process mean This type of control chart is typically used when the sample size is one Control chart that uses the range between n successive individual observations from a process to track the stability of the process LabVIEW SPC Toolkit Reference Manual Glossary variation This type of control chart is typically used when sample size is one N natural process The limits which contain a stated fraction of the individual limits observations in a population For a normally distributed population the stated fraction is typically the process mean 3 0 sigma non conforming unit A unit of product or service that does not meet a specification requirement normally distributed If a process is normally distributed expected values for individuals within the process population fall on a normal or bell shaped curve np Chart Control chart that uses the number of non conf
86. of points violating the given test run length The length of the sequence of points violating the given test National Instruments Corporation 2 45 LabVIEW SPC Toolkit Reference Manual Control Chart VIs Chapter 2 out of control points Lists the index of each point in the points array that the VI identified as out of control according to the applied tests Process Shift Detector Uses run rules to detect a process shift in a control chart with respect to the center line Returns whether or not a process shift was detected and if so the index of the first point of shift and the pattern detected are output This VI can be used to determine when to recalculate control limits points E process shift detected first point of shift center line The VI searches for the following patterns that signal a process shift Pattern 1 At least 10 out of 11 consecutive data points are on the same side of the center line Pattern 2 At least 12 out of 14 consecutive data points are on the same side of the center line Pattern 3 At least 14 out of 17 consecutive data points are on the same side of the center line Pattern 4 At least 16 out of 20 consecutive data points are on the same side of the center line points The points plotted on the control chart normally the output of one of the control chart VIs such as an X bar array center line The center line from the control chart VI limits cluster process shift detect
87. orming units in a sample to monitor the stability of the process The sample contains n units and zero or more units may be non conforming The value n be constant from sample to sample numeric controls Front panel objects used to manipulate and display or input and output and indicators numeric data O observation A measurement of a process characteristic P p chart Control chart that uses the fraction of non conforming units in a sample to monitor the stability of the process The sample contains n units and zero or more units may be non conforming The value n may vary from sample to sample Panel window VI window that contains the front panel the execution palette and the icon connector pane plot A graphical representation of an array of data shown either on a graph or a chart pop up To call up a special menu by clicking on an object with the right mouse button pop up menus Menus accessed by command clicking usually on an object Menu options pertain to that object specifically Pareto chart A chart of a set of counted or totalized characteristics in which the characteristics are ranked in order of their frequency of occurrence In SPC Pareto charts are normally used to evaluate relative contribution of assignable causes and prioritize corrective action LabVIEW SPC Toolkit Reference Manual G 4 National Instruments Corporation process capability pull down menus R R Range chart representation run ch
88. ossible and many different types of defects are possible Also known as a non conformity if the characteristic prevents the unit from meeting a specification requirement National Instruments Corporation F fraction non conforming front panel H Help window Histogram I icon in control process indicator individual observation M matrix measurement data moving Average chart moving Range Chart National Instruments Corporation G 3 Glossary the number of units in a sample not conforming to specification divided by the total number of units in the sample The interactive user interface of a VI Modeled from the front panel of physical instruments it is composed of switches slides meters graphs charts gauges LEDs and other controls and indicators Special window that displays the names and locations of the terminals for a function or subVI the description of controls and indicators the values of universal constants and descriptions and data types of control attributes A graphical summary of data in which the individual values are sorted by the range of values into which they fall also known as bins and in which the number of individuals falling within a each bin is counted The data is plotted by showing the number of values frequency in each bin Graphical representation of a node on a block diagram A stable process whose variation is due only to chance causes that is n
89. ounted from the process p np u c charts are attributes charts Pictorial description or representation of a program or algorithm In LabVIEW the block diagram which consists of executable icons called nodes and wires that carry data between the nodes is the source code for the VI The block diagram resides in the Diagram window of the VI Front panel objects used to manipulate and display or input and output Boolean TRUE or FALSE data Several styles are available such as switches buttons and LEDs Control chart that uses number of defects per sample to monitor the stability of the process Each sample contains n units and contains c defects per sample zero or more defects per unit The value of n must be constant from sample to sample National Instruments Corporation G 1 LabVIEW SPC Toolkit Reference Manual Glossary center line cluster connector control control chart control limits Cp process capability index Cpk centered capability ratio current VI D Diagram window Defect LabVIEW SPC Toolkit Reference Manual G 2 A line on a control chart representing average long term value of the statistic plotted on the control chart A set of ordered unindexed data elements of any data type including numeric Boolean string array or cluster The elements must be all controls or all indicators Part of the VI or function node that contains its input and output terminals through which data pa
90. ow in Zone C center line or beyond Test 3 Six points in a row steadily increasing or decreasing Test 4 Fourteen points in a row alternating up and down Test 5 Two out of three points in a row in Zone A or beyond outside 2 std errors Test amp Four out of five points in a row in Zone B or beyond Coutside 1 std errors Test 7 Fifteen points in a row in Zone C within 1 std errors above and below center line Test S Eight points in a row on both sides of the center line with none in Zones C Cwithin 1 std errors points The points plotted on the control chart normally the output of one of the control chart VIs such as an X bar array center line The center line from the control chart VI limits cluster std error The standard error associated with CL from the control chart VI limits cluster test enable The run rules to apply to the points array Each element of the array corresponds to a test 1 2 3 8 from element 0 to 7 in that order see front panel for test explanation Set the corresponding element to TRUE for each test you want to apply An easy way to do this from the diagram is to use an unsigned 8 bit integer set the appropriate bits and then use the number to binary array conversion tests flagged This cluster lists the tests violated and which sequence of points violated the test test The test violated 1 4 and so forth first point The index of the first point of the sequence
91. potential for accidental injury caused by product failure or by errors on the part of the user or application designer Any use or application of National Instruments products for or involving medical or clinical treatment must be performed by properly trained and qualified medical personnel and all traditional medical safeguards equipment and procedures that are appropriate in the particular situation to prevent serious injury or death should always continue to be used when National Instruments products are being used National Instruments products are NOT intended to be a substitute for any form of established process procedure or equipment used to monitor or safeguard human health and safety in medical or clinical treatment Contents About This Manual sitio eerie pilin age Aiden omar iste ix Organization of This Manual sseeseeseeesseeeeeseeseseerrereseeresereesee ix Conventions Used in This Manual esseeeeseeeeseeeeeereeeerrseeeeeee X Related Documentation 0 0 0 eeceececsseeeseeeeeeceeceeeeeeeeeeaeeeeeees xii Customer Communication essesseeesseeeseseestsrestsersreersseereseseesee xii Chapter 1 Introduction to Statistical Process Control in LabVIEW 0 0 cccceeeeeeees 1 1 T stallatiOi wro ern seeeiay cueve svouy E E E 1 1 WINO aa a aai e EE EA A E A 1 1 SPARGStat O nene e a E e E S 1 2 Macintosh esearon ne nn a e ai 1 3 Requirements for Using the SPC Toolkit n se 1 3 SPC Toolki
92. r attribute data this is the number of units n inspected for the counted characteristic a set of measurements observations or units from which counted data is taken used as a basis for evaluating the process Limits that define the range within which a product or characteristic conforms to specification or user requirements also known as tolerance limits known standard values for process range sample standard deviation mean or sigma from which control limits can be calculated Block diagram within the border of a structure a set of measurements observations taken from a larger set VI used in the block diagram of another VI comparable to a subroutine G 5 LabVIEW SPC Toolkit Reference Manual Glossary T tier chart top level VI u chart Vv variables chart VI library W waveform chart wire Wiring tool X x individual chart X bar chart LabVIEW SPC Toolkit Reference Manual A chart in which the individual observations in each sample are plotted vertically It is a useful means of visualizing the variation or spread in each sample VI at the top of the VI hierarchy This term distinguishes the VI from its subVIs Control chart that uses the average number of defects per sample to monitor the stability of the process The sample contains n units and contains c defects per sample zero or more defects per unit The value n may vary from sample to sample A pair of control charts t
93. re invalid Sample Statistics VI DEL HE F Computes statistics on the input array sample X sample std der skewness kurtosis sample X Individual observations on which to compute sample statistics median The center value of the points in sample X when sorted in ascending order If the number of points in sample X is even the median is the average of the center pair of points mean The average of the points in sample X sample std dev sample standard deviation computed as fsum x i x n 1 where n is the number of points in X National Instruments Corporation 3 5 LabVIEW SPC Toolkit Reference Manual Process Statistics VIs Chapter 3 skewness degree of asymmetry in the distribution of the points in sample X around the mean A normal distribution has a skewness of 0 Skewness is computed as sum x i x n sample std dev where n is the number of points in X kurtosis The relative peakedness or flatness of the distribution of the points in sample X A normal distribution has a kurtosis of 3 Kurtosis is computed as sum x i oan n sample std dev where n is the number of points in X General Histogram Finds the discrete histogram of the input sequence X based on the given bin specifications x i histogram bins a a axis max foo gytside mir error bins inclusion OBL X The input data 2n bins specifies the boundaries of each bin of the histogram The input
94. reto Chart output of the Pareto Chart VI Pareto Chart legend A pre formatted table indicator for use with the legend output of the Pareto Chart VI There are two libraries of examples with the SPC Toolkit The SPC_EXMP 11b library contains basic to intermediate SPC examples National Instruments Corporation 1 7 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 These examples are useful for getting started and learning how to group the SPC VIs to perform typical SPC calculations and presentations The SPC_DEMO 11b SPC demonstration library contains an example application the Real time SPC Demo that analyzes process data acquired point by point This is a more advanced VI that you could modify once you are more proficient at using the SPC Toolkit These libraries of examples are contained in the SPC directory in your LabVIEW folder or directory Implementing SPC Applications in LabVIEW This section discusses the main components that make up an SPC application and guides you through some of the programming techniques you can use in your statistical processing These programming techniques include representation of process data viewing raw process data creating control charts and determining whether your process is in control detecting out of control points and using process capability and Pareto analysis This section also directs you to the relevant standard Lab
95. rt limits to be calculated from standard values When using standard values the center line for the control chart p bar is set to p0 source Selects one of two sources for chart limits calculation 0 from data chart limits are calculated from the data in the input arrays as qualified by the index spec and indices to ignore inputs default selection 1 use std pO chart limits are calculated from the standard value p0 std p0 The standard pO value to use when calculating chart limits from standard values The center line for the control chart p bar will then be set to p0 The control limit calculations are as follows If standard values are used for the control limit calculations then p bar is set to std p0 otherwise p bar is calculated from the input samples as specified by the index spec and indices to ignore inputs T p if calculated from input data otherwise p pO r i n i UCLp P stderr mult PUP LabVIEW SPC Toolkit Reference Manual 2 26 National Instruments Corporation Chapter 2 DEL H E 132 Control Chart VIs LCLp p stderr mult pUSP n pd P n standard error np Chart Computes points and limits for an np chart a control chart for number non conforming Optionally you can choose a range of indices of samples to use and indices of samples to ignore in the control calculation The actual number of samples the VI uses to calculate the control limits is also output By
96. s sample mean and variation The chart for sample mean tracks variation in the mean of each sample against control limits The chart for sample variation tracks the variation in the distribution of each sample against control limits A typical variables control chart VI the X bar amp R Chart VI is shown in the following illustration chart limit sre Copt samples index spec Copt oH ale ii io bar chart limits indices to ignore Copt poy Range R std error multiplier 3 i F chart limits Ri bar d2 samples in calc The variables chart VIs whose names appear in the following list are described in more detail in this chapter e X bar amp s Chart e X bar amp R Chart e x amp mR Chart e mX bar amp mR Chart e Single Point X bar amp R S e Single Point x mX bar amp mR The X bar amp s Chart and X bar amp R Chart VIs take a two dimensional input array of samples where each column contains an individual observation within a sample and each row is a sample The sample size is the number of columns in the 2 D array The X bar amp R Chart VI is limited to sample sizes of 25 or less 25 columns The X bar amp s Chart VI has no limit on the sample size LabVIEW SPC Toolkit Reference Manual 2 2 National Instruments Corporation Chapter 2 Control Chart VIs The x amp mR Chart VI and mX bar amp mR Chart VI take a one dimensional input array of individual observations The VIs calculate the moving av
97. s Corporation Chapter 2 Control Chart VIs Rule Checker VIs for Testing Out of Limits Run Rules and Process Shift The SPC Toolkit contains the following rule checker VIs to test whether points exceed the control limits or whether any of the run rules are violated and to detect process shift e Check Control Limits identifies samples that exceed the upper and lower control limits e Rule Checker AT amp T WE identifies samples that violate one or more of the selected AT amp T Western Electric run rules e Rule Checker Nelson identifies samples that violate one or more of the selected Nelson run rules e Process Shift Detector detects process shift with respect to center line e Check Sequence identifies samples violating a generic n out of m sequence After a VI has identified out of control points you can wire the rule checker VI output to the indices input of the control chart VIs and exclude these samples from the control limit calculation The rule checker VIs are described in more detail later in this chapter Variables Chart VIs As described earlier in this chapter you use the variables chart VIs to detect out of control conditions on measured process characteristics These VIs generate outputs for control charts for sample mean and variation X Bar amp s Chart Computes points and limits for X bar and s control charts These are control charts for showing mean and sample standard deviation Op
98. s Fit hizt Sigma i h number of observations bin centers The x axis values for the center of each histogram bin DEL mei Connect the x values output of the histogram VI to this input sigma The estimated sigma of the observations from which the histogram was created See the description of the Process Mean and Sigma VI or the Sample Statistics VI in this chapter for an explanation of how this value is calculated number of observations The number of observations from which the histogram was created LabVIEW SPC Toolkit Reference Manual 3 8 National Instruments Corporation Chapter 3 DEL I Li DEL DEL DEL a EE Process Statistics VIs normal PDF height The height of the normal PDF that will fit the histogram Use this as an input to the Plot Normal PDF VI or Normal PDF Graph with Limits VI Normal PDF Graph with Limits Given the specification limits and the process mean and process sigma creates a graph of anormal probability distribution function PDF of the process against the specification limits and process mean and sigma PDF points to plot 50 PDF width sigma PDF height upper spec limit i normal PDF lower spec limit graph with limits process mean process sigma display mode T T 3 You can turn on and off drawing of the specification limits or the natural process limits and specify the sigma multiplier to use for the natural process limits default 3 by wiring in th
99. seesseeesererereererrerereee 3 1 Compute Process Capability 0 eee eeeeeeeeeeeee 3 3 Sample Statistics VI oe eee cece eeeeeeeeeeeeeeeeseeeee 3 5 General Histogram 0000 0 ee eee cece eeeceeeeeseeeeeeeeneeseeens 3 6 Fit Nrml PDF to Histogram s s s 3 8 Normal PDF Graph with Limits 0 3 9 Pl6t Normal PDF er e heise tent este Ee EEE EEE 3 10 Vertical Bar Graph with Limits 00 eee eee 3 12 Vertical Bar Graph oo eee ee eeceeeeeceeeeeeeeeeeeeeens 3 13 Rotate Graph eiiie iieis cesses ssseneesaee 3 14 Chapter 4 Pareto Analysis VIS 0 0 ccccccccscsessssesceseesesesteseeseseeseses 4 1 Pareto Counter nintuan ieii 4 2 P reto Chart e seerne a e E E E AE E EEA 4 3 Cause Code Lookup sreci insasi 4 4 Array to Bar Comb Graph ou eee eee eeeeeeeeeeneeeeeeee 4 5 LabVIEW SPC Toolkit Reference Manual vi National Instruments Corporation Contents Appendix Customer Communication eee A 1 Glossary ea ae E E N a ST A T G 1 Figures Figure 1 1 Basic Run Chart sersissoreissrsvoessiioesevsiisssr 1 10 Figure 1 2 Diagram for Basic Run Chart 0 cece eeeeseeeeeeeee 1 10 Figure 1 3 Basic Histogram Plot occ eecseeeseceeeeneeeeeaes 1 11 Figure 1 4 Diagram for Basic Histogram Plot 2 0 0 0 eseeseeseeeeeees 1 12 Figure1 5 Basie Ter Chart serren e e 1 12 Figure 1 6 Diagram for Basic Tier Chart 00 0 0 eee eeeeeeeeeeeeeeee 1 13 Figure 1 7 X bar and S Chart Example 00 0 cece eeeeeeeeseeeeeeeee 1 14 Figure 1 8 Diagram for X bar
100. sing pieces you need to complete your application The SPC Toolkit consists of a set of VI libraries that implement key SPC functions such as control charts process statistics and Pareto analysis The SPC Toolkit also contains several subVIs that generate the typical SPC graphical presentations To use Statistical Process Control effectively you must be trained in SPC methods SPC training is necessary because success in an SPC program depends on educated judgment and experience Rote application of pre existing templates is no substitute for this judgment The SPC Toolkit package is a way to use LabVIEW to create SPC applications If you are using this package to analyze and improve your process you must receive training in SPC methods or have access to someone who has SPC expertise Two good sources on Statistical Process Control methods are the Wheeler and Chambers work and the Montgomery work cited in the Related Documentation section of About This Manual The first reference can help you understand how to apply SPC methods and the National Instruments Corporation 1 3 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 second reference provides a good theoretical and mathematical basis for SPC You must have LabVIEW programming experience to use this package You can explore the simple examples included in the SPC_EXMP library after going through Chapter 1 in both the LabVIEW user
101. sses to and from the node Front panel object for entering data to a VI interactively or to a subVI programmatically A charting method for determining the stability of a process that is whether or not a process is in a state of statistical control Shewart control charts monitor process stability by plotting sample statistics against a center line and control limits Upper and lower limits on a control chart represent the amount of variation about a center line that can be attributed to chance causes for a given process characteristic Control chart points that fall outside the control limits signal that the process is not in control and that some action should be taken Control limits may be calculated from process data or from standard values A measure in sigma units of the process capability that is a ratio of the spread between the specification limits over the m sigma spread of the process variation where m is normally 6 A measure in sigma units of the process capability with respect to how well the process is centered relative to the specification limits also known as distance to nearest specification VI whose Panel window Diagram window or icon editor window is the active window VI window that contains the block diagram code A measured characteristic of a specific unit of product or service that prevents the unit from meeting a specification requirement or is otherwise undesirable In a unit one or more defects are p
102. stogram against relevant limits bin centers axis x histogram y upper spec limit in vertical bar graph lower spec limit with limits process mean process sigma display mode T T 3 You can turn on and off drawing of the specification limits or the natural process limits and specify the sigma multiplier to use for the natural process limits default 3 by wiring in the display mode If you do not wire the display mode the VI will draw the specification limits and natural process limits at 3 sigma by default histogram y Each element of this array is arranged so that the number of observations in each bin of the histogram is from left to right This is an output from the Histogram VI or the General Histogram VI bin centers axis x The x axis values for the center of each histogram bin Connect the x values output of the Histogram or General Histogram VI to this input upper spec limit The upper specification limit of the process lower spec limit The lower specification limit of the process process mean The estimated process mean See the description of the Process Mean and Sigma VI in this chapter for an explanation of how the process mean and process sigma are calculated process sigma The estimated process sigma display mode Optional display mode specifier If unwired the VI will draw the specification limits and the natural process limits by default Cluster of the following inputs show spec limi
103. t process mean process sigma display mode FF 3 You can turn on and off drawing of the specification limits or the natural process limits and choose the sigma multiplier to use for the natural process limits default three by wiring in the display mode If you do not wire the display mode the specification limits and natural process limits are not drawn samples X The values to be plotted on the tolerance chart Each row is DEL ost a sample with n observations where n is the number of columns in the 2D array n is also known as the subgroup size starting sample number The sample number of the first sample the VI uses to label the chart x axis If unwired sample labeling on the x axis will start at zero LabVIEW SPC Toolkit Reference Manual 2 40 National Instruments Corporation Chapter 2 Control Chart VIs upper spec limit The upper specification limit of the process lower spec limit The lower specification limit of the process AGE process mean The estimated process mean See the description of the Process Mean and Sigma VI in Chapter 3 Process Statistics VIs for an explanation of how the process mean and process sigma values are calculated process sigma The estimated process sigma display mode Optional display mode specifier If unwired the VI will not draw the specification limits and the natural process limits by default This cluster contains the following JE show spec limits If TRUE
104. t b b gt gt gt gt gt gt gt Control Charts b Tutorial Process Statistics gt Utilit T vYA YY vV Vv The Control Chart VIs include VIs for calculating control chart limits for both attributes and variables charts drawing control chart graphs and applying run rules to control charts The Process Statistics VIs include VIs for estimating process distribution and capability calculating and plotting histograms and functions for plotting and fitting normal probability distribution functions to histograms The Pareto Analysis VIs include VIs for counting and sorting assigned causes and for creating Pareto charts When you view the VIs from your block diagram using the help window notice that some of the input parameters are labeled in bold typeface Bold typeface identifies parameters that should be wired to make the VI operate properly Plain typeface identifies input parameters that are optional Optional parameters can help you take advantage of advanced modes of operation but are not necessary for the VI to work When you do not wire the optional input parameters they are automatically set to reasonable default values National Instruments Corporation 1 5 LabVIEW SPC Toolkit Reference Manual Introduction to Statistical Process Control in LabVIEW Chapter 1 Custom Controls A set of custom controls for SPC graphs and legends are also installed as part of the LabVIEW front panel Controls menu These
105. t produces a set of Pareto totals for each cause including frequency cumulative frequency percentage of total and cumulative percentage of total for each cause The VI sorts the list from the cause with the highest occurrence to the cause with the lowest occurrence e Pareto Chart given a set of Pareto values creates a Pareto chart of the frequency of occurrence of each cause and a Pareto chart of the percentage contribution of each cause e Cause Code Lookup given an unsorted list of numeric cause codes and a list of the cause for each cause code produces of list of causes with the count for each cause sorted from the cause with the highest count to the cause with the lowest count See Figure 1 17 in Chapter 1 for an example of a Pareto chart application The Pareto Counter VI will accept two alternative inputs You can either pass in an unsorted list of causes an array of strings or an array of clusters with each cluster containing a cause string and the corresponding total number of occurrences of that cause You may be using numeric cause codes instead of strings In this case you can use the Cause Code Lookup VI to count the number of occurrences of cause codes and generate a list of cause strings with the count for each cause to be passed to the Pareto Counter VI If no cause string is given for a cause code the code itself will be put in string form National Instruments Corporation 4 1 LabVIEW SPC Toolkit Reference
106. t Organization cece eeceseceeeeseeeeeeeeeeeeeseeees 1 4 MT TeADParies onem neninn a a st cateces shiv a 1 4 Custom Controls 0 cee eeeececceesceeceseeeeeeeeeeeeeseeeseesaeeneenaes 1 6 LabVIEW SPC Toolkit Examples 0 0 eee eects 1 7 Implementing SPC Applications in LabVIEW 1 8 Representation of Process Data in LabVIEW 0 1 8 Viewing Raw Process Data eeeeceeeeeesseeeeeseeseeeneeeaes 1 9 Creating Control Charts and Determining Whether the Process Is in Control 1 13 Detecting Out of Control Points and Process Shift 1 15 Process Capability Analysis eee eeeseeeeeseeseeeneeeees 1 19 Pateto Analysis sscsvecsspissescesis steed et ES aT echawes esse E EENE erae 1 20 Chapter 2 Control Chart VIS vis gciscessssisissensoeesiseccnemesecomemavnmenestineies 2 1 Calculating Control Chart Limits and Points 0 ee 2 1 Variables Chart VAS is scsisess cssscsvsipetencsrteovsooseceevtneassedeoens 2 2 Attributes Charts VIS eeeeeeceseeeecseeeeecseessecseesaeeneeeaes 2 3 VIs for Drawing Charts 0 eee eee eseeeeecneecsecneeeseesseeaes 2 4 VIs for Plotting Control Chart Points and Limits 2 5 VIs for Creating Graphs of Raw Process Data 2 5 Rule Checker VIs for Testing Out of Limits Run Rules and Process Shift 2 7 National Instruments Corporation v LabVIEW SPC Toolkit Reference Manual Contents Variables Chart VIS 0 cescesecessscesceceseeesece
107. the chart limits are calculated from the data in the input individual array You do not have to wire this cluster unless you want the chart limits to be calculated from standard values When using standard values the center line for the mX bar control chart X bar bar is set to std mean and the center line for the mR control chart mR bar is set to std RO or std sigma d2 source Selects one of three sources for chart limits calculation 0 from data chart limits are calculated from the data in the individuals x array as qualified by the index spec and indices to ignore inputs default selection 1 use std mean RO chart limits are calculated from standard values for mean and range 2 use std mean sigma chart limits are calculated from standard values for mean and sigma std mean The standard mean value to use when calculating chart limits from standard values std RO sigma The standard RO or sigma value to use in calculating chart limits from standard values LabVIEW SPC Toolkit Reference Manual 2 20 National Instruments Corporation Chapter 2 Control Chart VIs n sample size The number of consecutive individual values to use in the moving range calculation n sample size may range from 2 to 25 By default n sample size is 2 mX bar amp mR bar d2 This cluster contains estimates on process mean and sigma based on individuals included in the control limit calculation or on standard values mX bar bar Th
108. the control limit calculation indices to ignore Indices of samples to exclude from the control limit calculation This is useful for eliminating out of control points from the control limit calculation By default this is an empty array std error multiplier The multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 X bar bar This is an estimate of the process mean based on the grand average of the samples included in the control limit calculation If the control limits are calculated from standard values this is set to the standard mean X bar The mean of each input sample This is the array plotted on the X bar control chart LabVIEW SPC Toolkit Reference Manual 2 8 National Instruments Corporation Chapter 2 DEL Control Chart VIs vas bar chart limits This cluster contains the limits for the X bar chart UCLx The upper control limit for the X bar chart CLx The center line for the X bar chart Clx X bar bar or standard mean and is also the estimated process mean if calculated from the input samples LCLx The lower control limit for the X bar chart HE BE standard error The standard error associated with CLx s The sample standard deviation of each input sample This is the array plotted on the s control chart s chart limits This cluster contains the lim
109. tionally you can choose a range of indices for samples to use and indices of samples to ignore in the control limit calculation The VI outputs the actual number of samples used to calculate the control limits By default control limits are calculated from the input samples You can National Instruments Corporation 2 7 LabVIEW SPC Toolkit Reference Manual Control Chart VIs DEL 1 i E DBL Chapter 2 also calculate control limits from standard values by wiring the chart limit src input chart timit sre Copt Samples index spec opt J io w bar chart limits indices to ignore Copt g hs std error multiplier 2 Hoos chart limits scbar fod Samples in calc samples X Samples on which to compute control limits and points for the X bar and s charts Each row is a sample with n observations where n is the number of columns in the 2D array N is also known as the subgroup size The minimum sample subgroup size is 2 index spec Use this cluster to choose a range of samples to use for the control limits calculation start index Index of the first sample to include in the control limit calculation Default is zero which is the index of the first sample in samples X array end index Index of the last sample to include in the control limit calculation Default is zero which selects the last sample in samples X array If you do not wire this cluster the VI includes all samples in the samples X input array in
110. ts If set to TRUE the VI draws the specification limits By default this is TRUE LabVIEW SPC Toolkit Reference Manual 3 12 National Instruments Corporation Chapter 3 DEL Process Statistics VIs show natural process limits If set to TRUE the VI draws natural process limits on the plot By default this is FALSE EL NP limit sigma The sigma multiplier for the natural process limits The natural process limits are drawn at process mean NPLimit sigma process sigma By default this is 3 0 If you wire the display mode cluster to change one of the default settings you must specify all three elements vertical bar graph with limits Centered vertical bar graph in which each bar is the height given in the histogram input and is centered at the values given in the bin centers input You can wire this output to the Histogram Bar Graph with Limits custom SPC control Vertical Bar Graph Creates a centered vertical bar graph Bars are centered at the x values with height y Can be used to plot a histogram histogram y bin centers x histogram Each element of this array is arranged so that the number of observations in each bin of the histogram is from left to right This is an output from the Histogram VI bin centers The x axis values for the center of each histogram bin Connect the x values output of the histogram VI to this input bar graph Centered vertical bar graph Each bar is of the heig
111. ts default 3 You can leave the display mode input unwired in which case the graphing VI will use the defaults The defaults are not the same for all the VIs The x axis on all the graphs in the control chart VI library is labeled by sample number the default starting sample number is zero You can wire a different number to suit your needs Notice that array index counting in LabVIEW is zero based therefore numbering samples starting from zero is the least confusing method to use The control chart VIs use simple X Y pairs to define horizontal limit lines drawn on the XY graph An easy way to use these graphing VIs is to copy the graph on the front panel of the VI and paste it on the front panel of your application The graph already has appropriate labels colors and patterns selected for all the graph lines You can then size and customize the graph display to fit your needs You can also use waveform charts sometimes called strip charts to plot your control charts in which case the VI passes information to the chart one sample at a time The SPC Toolkit does not provide VIs for strip chart presentation To draw control chart natural process or specification limits against your control chart points cluster the limit values with your point and wire the cluster to your waveform chart The VIs for drawing charts are described in more detail later in this chapter LabVIEW SPC Toolkit Reference Manual 2 6 National Instrument
112. uals to exclude from the control limit calculation This is useful for eliminating out of control points from the control limit calculation By default this is an empty array std error multiplier The multiplier to use for the upper and lower control limits Normally you leave std error multiplier unwired and the VI sets the control chart limits to 3 0 standard errors The default is 3 0 x bar This is an estimate of the process mean based on the average of the individuals included in the control limit calculation If the control limits are calculated from standard values this is set to the standard mean x The individual observations This is the array plotted on the x control chart x chart limits This cluster contains the limits for the x chart UCLx The upper control limit for the x chart National Instruments Corporation 2 15 LabVIEW SPC Toolkit Reference Manual Control Chart VIs DBL Chapter 2 CLx The center line for the x control chart Clx x bar or standard mean and is also the estimated process mean if calculated from the input individuals LCLx The lower control limit for the x chart HE E standard error The standard error associated with CLx moving range mR The moving range of individuals x i x i 7 1 where n is the sample size This is the array plotted on the mR control chart mR chart limits This cluster contains the limits for the mR chart UCLmrr The upper control li
113. ulate two sided one sided upper only or one sided lower only process capability and fraction non conforming By default mode is two sided 0 two sided Cpk and fraction non conf are calculated with respect to both the upper and lower specification limits 1 upper only Cpk and fraction non conf are calculated with respect to the upper specification limit only In this case Cpk CpU and fraction non conf fraction gt USL 2 lower only Cpk and fraction non conf are calculated with respect to the lower specification limit only In this case Cpk CpL and fraction non conf fraction lt LSL The values Cp and Cpkm are always calculated from both the upper and lower specification limits regardless of the value of mode sigma tolerance The sigma multiplier to use in the process capability calculations If sigma tolerance is left unwired a value of 6 0 is used by National Instruments Corporation 3 3 LabVIEW SPC Toolkit Reference Manual Process Statistics VIs Chapter 3 default which is the tolerance spread most commonly used for process capability calculations 2n CpU amp CpL This cluster contains the one sided upper and lower process capability ratios CpU The one sided upper process capability ratio CpU Upper spec limit process mean P 05 sigma tolerance process sigma By default 0 5 sigma tolerance 3 0 CpL The one sided lower process capability ratio Cpu Process mean lower spec
114. ustrates the block diagram for this example Figure 1 17 Pareto Causes Chart Example mo__ Cause Frequency Cumulative Freq Frequency Graph Cause percentage Percent Graph Cumulative Figure 1 18 Diagram for Pareto Chart Example Percent Graph National Instruments Corporation 1 2 LabVIEW SPC Toolkit Reference Manual Chapter Control Chart VIs This chapter describes the control chart VIs which include the variables charts attributes charts chart drawing and rule checking VIs The control chart VIs compute control limits for control charts create control chart graphs and apply rules to control chart data that detect out of control conditions Calculating Control Chart Limits and Points The variables and attributes chart VIs compute the points to be plotted on the control charts as well as the center line and control limits for the control chart The process data input to the chart VIs is a one or two dimensional array of samples The control chart VIs pass output arrays and chart limits clusters to one of the chart drawing VIs to create the desired control chart graph The chart limits cluster contains the upper control limit UCL center line CL lower control limit LCL and the standard error from which the upper and lower control limits are calculated The limits are center line 3 standard errors by default To compute the control limits from th
115. utput of the Pareto Counter VI creates two Pareto charts and the associated legend One is a bar chart of the frequency of occurrence of each cause The other is a bar chart of the percentage contribution of each cause The legend is a list of cause codes with their rank in a table 2D array of strings format EB ln Pareto chart freq Pareto values Pareto cooParete chart percent chart P kaalegend Pareto Values An array of clusters consisting of the following cause The name of the assigned cause frequency The number of occurrences of cause cumulative frequency The total number of occurrences at the time this value was read percent of total The percent contribution of cause JB EEE cumulative percent The total of percentages at the time this value was read Entries are sorted by frequency of occurrence of each cause Pareto chart freq Bar graph of frequency of occurrence of each cause with superimposed cumulative plot of frequency You can wire this output to the Pareto Chart custom SPC control Pareto chart percent Bar graph of percentage contribution of occurrence of each cause with superimposed cumulative plot of frequency You can wire this output to the Pareto Chart custom SPC control Legend A table 2D array of strings listing the cause string for each bar in the Pareto chart from the rank of 1 cause with highest frequency of occurrence on You can wire this output to the Pareto Chart Le
116. wn show natural process limits If true the natural process limits will be drawn on the plot LA NP limit sigma The sigma multiplier for the natural process limits By default this is three The natural process limits drawn will then be process mean NP limit sigma process sigma Note Ifyou wire the display mode cluster to change one of the default settings you must specify all three elements normal PDF graph with limits An XY graph with the normal PDF of the process plotted against the specification limits and process mean and standard deviation You can wire this output to the normal PDF graph with Limits custom SPC control Plot Normal PDF Given the process mean and sigma creates a graph of a normal probability distribution function PDF for the process Also returns an array of XY values for the normal distribution This graph is useful for LabVIEW SPC Toolkit Reference Manual 3 10 National Instruments Corporation Chapter 3 Process Statistics VIs viewing the estimated distribution of a sample or group of samples or for plotting a normal PDF against a histogram points to plot 50 process mean a normal POF yalues rocess sigma p 2 graph PDF height normal POF graph PDF width sigma process mean The estimated process mean See the Process Mean and DEL Sigma VI or the Sample Mean and Std Dev VI to calculate this value process sigma The estimated process sigma See the Process Mean a
117. y as qualified by the index spec and indices to ignore inputs default selection 1 use std mean sO chart limits are calculated from standard values for mean and sample standard variation 2 use std mean sigma chart limits are calculated from standard values for mean and sigma std mean The standard mean value to use when calculating chart limits from standard values std s0 sigma The standard sO or sigma value to use in calculating chart limits from standard values The control limit calculations for the chart limits are as follows If standard values are used for the control limit calculations then X X bar bar is set to std mean s s bar is set to std sO or std sigma c4 otherwise X and s are calculated from the input samples as specified by the index spec and indices to ignore inputs UCLx X stderr mutt C4vn I CLx LCLx X stderr mutt C4Vn S eal standard error E UCLs 5 stderr nun z 4 CLs LCLs ay s stderr oun C4 LabVIEW SPC Toolkit Reference Manual 2 10 National Instruments Corporation Chapter 2 DEL Note Control Chart VIs s 1 c C4 standard error X Bar amp R Chart Computes points and limits for X bar and Range control charts These are control charts for charting mean and range Optionally you can choose a range of indices for samples to use and indices of samples to ignore in the control limit calculat

LabVIEW Statistical Process Control Toolkit Reference Manual

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