MECH3660 9660 CNC Machining Manual 2015
Contents
1. EJ t 10 0 et 10 20 30 Lea e 5 20 0 10 0 10 0 20 4 10 0 20 0 al Figure 1 2b Typical example segment of a program that uses both G90 and G91 commands Spindle Speeds The relative hardness of the material and the type of cutting tool affect spindle speed The harder the material 1s the slower the speed should be The load put on the spindle motor must also be taken into account Heavy cuts at low speeds will make the motor run hotter than lighter cuts at higher speeds The selected feed rate and the depth of cut should not cause the spindle motor to greatly lose speed or cause the tool to chatter against the job The machinist usually sets the spindle speed however an approximate guide is given in a later part of these notes Up cut and Down cut Milling or Standard and Climb Milling The cutting action of a milling cutter varies with the direction of feed Referring to Figure 1 3 below in up cut milling the direction of feed is opposite to the direction of cutter rotation In down cut milling the direction of feed is the same as the direction of cutter rotation On some manually operated mills only up cut milling could be performed due to the backlash or slop in its driveline As the Mori Seiki NV4000 mill has a ball screw driveline with no backlash in its drive it can perform both forms of milling However up cut milling is still usually preferred over down cut milling because of t2. Cutting Speed mimin VG 1000 M RPM D Diameter of End mill mm _ 000 Va F Feed Rate mmv min xD f Feed per Tooth imm tooth F 7 No of Cutter Teeth ba NxZ m 3 142 C Factor Cutting conditions F NxZxixl 18 B kasaas iska 25 Chapter 2 FORCE AND POWER IN MACHINING Referenced from Materials and Process in Manufacturing Section 21 5 pg 607 610 8th Ed and Computer Aided Manufacturing section 6 0 basic machining calculations pg 195 209 3 Ed These two texts have been written for U S based Engineering students hence the use of imperial measurements Some conversions are given below However you may wish to either research your own conversions or use a WEB based converter such as http www convett me com en A basic nomenclature of some of the terms used in this part of the notes is provided below However it is recommended that you read one of the two texts in order to gain a better understanding of the concepts involved Nomenclature and some basic conversion factors applicable to Lathes CF Correction Factor used to account for dull tools and other issues usually set to 1 25 CT Cutting time sec E Efficiency of machine dimensionless HP Horsepower hp MRR Metal Removal Rate volume of cut cutting time V Cutting Speed feet per minute Vr Feed rate inches per minute f Feed inches per revolution n Number of teeth in the cutter N Rotational
3. Tool fed into or hit against the workpiece Tool damage Machine damage G43 Tool Length Compensation Reference to the Suttons Tool catalogue in your notes illustrates that tool length varies with tool size and type even short or long series within the same type The G43 allows compensation for the tool that you have nominated in the Z axis for the tool you have nominated This command ties in closely with H command 11 G54 Work Coordinate System1 Select The G54 command moves the coordinate system from the machines coordinate system usually located on one of the machines corners to the working area G54 PZ G54 1 P2 Machine Coordinate System G80 Cancel Canned Cycle Some routines such as hole drilling cycles are modal 1 e they remain active until turned off When completing a canned cycle or in your case for good practice you must ensure that any canned cycles are cancelled before your program can proceed 12 Common Control Statements These statements or codes do not involve any tool motion but set up certain parameters needed for the machining operation Examples are described below M00 Program Stop Program Execution and the machine stop temporarily M01 Optional Stop If the optional stop switch on the operation panel is ON The machine stops temporarily If the optional stop switch on the operational panel is OFF The M01 command is ignored and the program is executed continuously M02 End of program Takes
4. down Z 11mm at a feed rate of 70mm min rapid traverse up Z 1mm rapid traverse to the location of hole 4 feed tool down Z 11mm at a feed rate of 70mm min rapid traverse up Z Imm rapid traverse to the location of hole 5 feed tool down Z 11mm at a feed rate of 70mm min move tool up Z Imm at rapid traverse 17 Basic Operations Plan Machining the Profile Figure 1 10 Figure 1 10 is a subset of the drawing included in Figure 1 7 It is included to give a clearer picture of the outside profile relative to the home position in the XY plane and the path that the cutting tool will take The cutting tool begins cutting the profile at the bottom left hand corner nearest to hole 5 This location is chosen because it 1s closest to where the tool finished drilling all of the holes Hence the tool has less distance and consequently time to travel to its next cutting position The lines of code listed below represent the CNC code instructions as per the comments described in points 8 through to 13 of the Operation Plan The code is a continuation from the previous page N18 GOO X112 5 Y 65 0 N19 G01 Z 10 0 F70 0 N20 G01 Y 5 0 F170 0 N21 G03 X92 5 Y15 0 R20 0 N22 G01 X57 5 N23 G02 X47 5 Y25 0 R20 0 N24 G01 Y45 0 N25 G03 X27 5 Y65 0 R20 0 N26 G01 X 18 0 N27 G03 X 33 77 Y 57 33 R20 0 N28 G01 X 108 25 Y 37 85 N29 G03 X 112 5 Y 50 17 R20 0 N30 G01 Y 65 0 N31 G01 X112 5 N32 G00 Z1 0 N33 GOO X0 0 Y0 0 22
5. 0 move tool down Z 11mm at a feed rate of 70mm min N4 G01 X39 4 Y39 4 F170 0 move tool to position 39 4 39 4 at a feed rate of 170mm min N5 GOO Z50 0 rapid feed the tool up Z 50mm for clearance N6 M05 spindle motor off N7 M02 end of program Figure 1 4 G02 Circular interpolation clockwise G03 Circular interpolation counter clockwise Circular interpolation moves the cutting tool along an arc from the starting point to an end point specified in the CNC block The curvature of motion is determined by the location of the arc s radius R which must be specified in the same CNC block The direction of rotation from the starting point determines the actual shape of the arc relative to the spindle axis A G02 code moves the tool in a clockwise CW motion from the starting point a G03 code moves the tool in counter clockwise CCW motion from the starting point Referring to Figure 1 5 plus the sample G codes and explanations in Figure 1 6 illustrate these points more clearly Start Point CW End Point G90 G01 X28 0 Y0 0 F50 0 G01 Y20 0 G03 X18 0 Y30 0 R10 0 G01 X 8 0 G02 X 28 0 Y 10 0 R20 0 G01 Y 10 0 G02 X 8 0 Y 30 0 R20 0 G01 X18 0 G91 G03 X10 0 Y10 0 R10 0 G90 G01 Y0 0 Figure 1 5 Cutting feed Figure 1 6 StartPoint CCW End Point ABSOLUTE REGION 1 REGION 2 REGION 3 a REGION 4 REGION 5 b REGION 6 REGION 7 c REGION 8 INCREMENTAL
6. 5 0 N34 M05 N35 M02 rapid traverse to bottom left corner offsetting 5mm for the 10mm tool diameter feed tool down Z 11mm at a feed rate of 70mm min feed tool towards radius at a feed rate of 170mm min feed tool c clockwise with a 20mm radius turn feed tool towards next position feed tool clockwise with a 20mm radius turn feed tool towards next position feed tool c clockwise with a 20mm radius turn feed tool towards next position feed tool c clockwise with a 20mm radius turn the end point of the radius could be found by using trig feed tool towards next position feed tool c clockwise with a 20mm radius turn feed tool towards next position feed tool towards next position rapid traverse up Z 1 I mm move tool to 0 0 0 0 25 0 to allow tool removal spindle motor off end of program 18 Mori Seiki NV4000 CNC Template 2015 LEAVE THIS LINE BLANK ALL PROGRAMS WRITTEN FOR THE MORI SEIKI NV4000 REQUIRE A SYMBOL ON THE SECOND LINE OF THE FILE 0229 ALL PROGRAMS BEGIN WITH THE CAPITAL LETTER O AND THE LAST FOUR DIGITS OF YOUR SID N110 MORI SEIKI NV4000 FORMAT TEMPLATE FOR MECH3660 MECH9660 2015 N120 INCLUDE BELOW THIS LINE AS A HEADER N130 CONNECTING ROD DESIGNED BY STUDENT NAME STUDENT SID PART CNC CODED BY STUDENT NAME 9 STUDENT SID PART NAME N140 G21 METRIC UNITS N150 G90G80G40G17G94G00 G90 ABSOLUTE PROGRAMMING G80 CANCEL CANNED CYCLE G40
7. 82 0 091 Nickel cobalt based 200 360 2 0 2 5 0 09 0 11 E temperature materials alloys Aluminium 2014 T6 2017 T4 30 150 at 6064 T6 R Pure 108 Hard rolled ae k Mata 80 TOOK 0 S 1 0 0 036 0 046 Musgo alam 210 390 2628 oi Table 2 3 Where E 1s the efficiency of the machine This factor accounts for the power needed to overcome friction and inertia in the machine and drive moving parts Usually 80 is used Correction factors CFs may also be used to account for variations in cutting speed feed and rake angle There is usually a tool wear correction factor of 1 25 used to account for the fact that dull tools use more power than sharp tools The primary cutting force F can be roughly estimated according to F HP MRR 33000 V Ib 2 0 10 0 This type of estimate of the major force F is useful in analysis of deflection and vibration problems in machining and in the proper design of work holding devices as these devices must be able to resist movement and deflection of the part during the process In general increasing the speed feed or depth of cut will increases the power requirement Doubling the speed doubles the HP directly Doubling the feed or the depth of cut doubles the cutting force Fc In general increasing the speed does not increase the cutting force Fe which has also been a puzzle Equation 2 0 7 0 can be used to estimate the maximum depth of cut d for a process as limi
8. CANCEL CUTTER COMP G17 XY PLANE G94 FEED PER MINUTE GOO RAPID TRAVERSE N160 G91G28Z0 G91 INCREMENTAL PROGRAMMING G28 RETURN TO MACHINE HOME ON Z AXIS FIRST N170 G91G28Y0 INCREMENTAL PROGRAMMING RETURN TO MACHINE HOME ON Y AXIS SECOND N180 T Select either TI 3mm Dia Long Series Slot Drill N190 or T2 5mm Dia Long Series Slot Drill N200 or T3 5 1mm Dia Drill N210 or T4 10mm Dia Long Series Slot Drill N220 M06 TOOL CHANGE N230 M01 OPTIONAL STOP FOR INSPECTION MEASUREMENT N240 S12000 SPINDLE SPEED 12000 RPM N250 M03 SPINDLE MOTOR ON CW N260 M08 COOLANT ON N270 G90 ABSOLUTE PROGRAMMING N280 G54 WORK COORDINATE SVSTEM 1 SELECTED N290 ENSURE ALL MACHINE COORDINATE VALUES HAVE A DECIMAL POINT eg X2 32 N300 G00 X2 22 V 2 22 RAPID TRAVERSE TO FIRST X AND Y COORDINATES N310 G43 Z50 0 H G43 TOOL LENGTH COMPENSATION POSITIVE H HEIGHT OFFSET ON SAME LINE AS FIRST Z RAPID MOVEMENT N320 G00 Z15 0 RAPID TRAVERSE TO 15MM ABOVE Z0 N330 MACHINING OPERATIONS INSERT YOUR CNC MACHINING CODE IN HERE AND RENUMBER N340 G01 Z F70 LINEAR INTERPOLATION TO Z COORDINATE AT PLUNGE FEEDRATE 70mm MIN N350 601 X2 2 Y F170 LINEAR INTERPOLATION TO X AND Y COORDINATES AT FEEDRATE 170mm MIN N360 G01 Z 12 3 F70 0 REMOVE COMMENT PLUNGE DISTANCE amp FEEDRATE mm min FOR PENERATION THROUGH CIRCULAR JOB OR N370 G01 Z 10 3 F70 0 REMOVE COMMENT PLUNGE DISTANCE amp FEEDRATE mm min FOR PENERATION THRO
9. G30 allows easier repetition of the same program by pressing one button on the control panel H Command The H command calls up a predetermined height offset for the particular tool that you have nominated In our configuration if you are using Tl then you should specify HI as your height offset The H commands have been numbered to correlate with the tool numbers The H values for our pump project have been entered into the Mori Seiki controller memory by the operator beforehand T Commands Although the T command is not part of the header they are a requirement of any program The T command rotates the tool carousel into the required position in anticipation of a tool change Please note that the command does not perform the tool change The following tools available to you and their relevant T number are listed below for your reference T1 3mm Long Series Slot Drill T2 5mm Long Series Slot Drill T3 5 1mm Long Series Drill T4 10mm Long Series Slot Drill Use the appropriate T number for your program S Command The S command specifies the spindle speed The Mori Seiki MV4000 is capable of spindle speeds ranging from 0 12 000 RPM In the sample program given a nominal value of 12 000 RPM has been specified In your code it would be advisable 1f you could use the same value If the required value differs from what you have specified The operator will adjust the spindle speed either by editing your code or manually controlling the
10. MECH3660 Manufacturing Engineering MECH9660 Foundation in Manufacturing Engineering Compiled by Paul Briozzo School of Aerospace Mechanical amp Mechatronic Engineering University of Sydney 2015 Contents CNC Machining Manufacturing Processes Chapter 1 CNC Machining Writing CNC code Chapter 2 Forces in Machining References Preface The MECH3660 5660 students of 2014 are thanked for their enthusiasm for the subject and their support The year 2015 brings with it new challenges and opportunities Some major changes for 2015 include the introduction of a group 3D printing laboratory which should enable students to develop some basic skills in this exciting and developing field The other minor change is the use of pdf lecture notes for information distribution throughout the semester Throughout the semester you will be provided with lecture notes tutorials and all course data at the following location http web aeromech usyd edu au MECH3660 Course Documents Paul Briozzo February 2015 Sydney Australia Chapter 1 CNC Machining Writing CNC code Introduction The numerical control part of MECH3660 MECH5660 Manufacturing Engineering is designed to give a basic but realistic overview of the general area of CNC machine tools In 2015 this component is roughly four weeks in duration It incorporates a number of lectures and tutorials covering the definition and usage of CNC commands and the use o
11. REGION 9 d ABSOLUTE REGION 1 e 10 G17 Select the XY Plane Using G17 indicates that you are intending to work in the XY plane All work in this course is based around the XY plane For reference G18 refers to the XZ plane and G19 refers to the YZ plane G28 Return the Axes to the Machine Zero Point Returns the machine to its home position in preparation for a tool change A G91 incremental mode modal command must precede the G28 command Also note that a G90 absolute mode modal command must be initiated before machining takes place G40 Cancel Cutter Compensation Cutter compensation 1s used by professional CNC machinists as a finishing cut to a CNC project It is usually used in conjunction with the cutter compensation commands G41 cutter radius offset to the left and G42 cutter radius offset to the right In this course we do not use G41 or G42 commands as they are tool specific commands and require more experience and understanding than we are able to provide in the time available You may r the less please refer to the figure below for an appreciation of their use Taal The lool radius offset commands ar as folkowa Gdi Offsets the programmed paths to the lan in reference to the tool advannoing direction Offsets the programmed paths t ihe might in refereri t ihe lool advancing direction Th programmar must thoroughly understand the G41 and 647 functions as well as the tool paths to be generated
12. UGH 10mm LID JOB OR N380 G01 Z 20 3 F70 0 REMOVE COMMENT PLUNGE DISTANCE amp FEEDRATE mm min FOR PENERATION THROUGH 20mm BASE JOB N390 G00 Z50 0 RAPID TRAVERSE TO 50 00mm ABOVE Z0 0 MOVES TOOL AWAY FROM JOB N400 M09 COOLANT OFF N410 M05 SPINDLE MOTOR OFF N420 G91G28Z0 INCREMENTAL PROGRAMMING RETURN TO MACHINE HOME ON Z AXIS FIRST N430 G91G28Y0 INCREMENTAL PROGRAMMING RETURN TO MACHINE HOME ON Y AXIS SECOND N440 RETURN TO MACHINE HOME ON X AXIS NOT REQUIRED N450 M30 END OF PROGRAM 19 Suggested Tool Types and Sizes The following pages include some of the more common commercially available tool types and sizes that are available commercially available SHORT SERIES 52 ZT CENTRE CUTTING METRIC PLAIN SHANK di ta No of TEMM mm mmi Flutes TIGN 2 amp EO 2 0102 2648 2 5 E 50 2 0102 4954 3 6 SO 2 Ome iggi 3 6 5 50 2 Oia sBid 4 E 66 2 0102 2597 4 5 EO 2 Oe 45870 5 5 B 3 102 2563 5 5 5 59 2 Dino 4546 6 BO 2 Do 4525 6 5 10 60 iz z Di0 4512 7 10 ES 14 2 0102 4495 To 65 z _ IME 4478 E 65 2 DIOS 4461 a5 Es 2 T 4424 g 70 2 DIOS 4427 3 5 TO 2 p02 4999 10 70 gt ta 4342 10 5 2 gige 4359 11 2 0102 4335 E z moe 4308 2 2 2 z z a z z yaa J etry P i ta pee a Made in Australia 1 F a 20 LONG SERIES L2 37 CENTRE CUTTING METRIC PLAIN SHANK mh m oy dh Pa RRRIESB do P3 Ag A R r Bad hR r
13. a ion saia areia ce ture 1 0mm to 6000 0mm min PCCW ACY L ae ves pesos ice eae nine eee 0 001mm Spindle speed range iaassssssssssssssaaaaa 1 to 12 000 RPM Hold down provision cccccceeeeeeee eee e eens Pneumatic air vice and conventional T Slots Motor Spindle iaasiaasaasaassasaasaaaaaaaaa 11kW continuous Motor Feed eee X 1 6kW x 2 Y 1 6kW x 2 Z 3 0kW x 2 Power requirements ccc cece cece eee e ee ee eens 27 4KVA Writing a Program A part program consists of lines of code each comprising one block and each representing the next location of the tool centre point along the tool path Traditionally a line of code begins with a block number N followed by a G code indicating a geometric motion by the tool or an M code representing a machine function such as turning the spindle on The Mori Seiki mill does not require block numbers except when you need to reference back to a particular point on the program Each line of a program has a standard form with variations according to the particular motion required for the tool and the corresponding machine codes used Referring to Figure 1 1 and the sample code is included below Figure 1 1 Sample code Comments NO M03 set spindle on NI G90 in absolute co ordinates N2 GOO X17 1 Y 18 0 Z1 0 move rapid to next position 17 1 18 0 1 0 N3 G01 Z 5 0 F70 0 move tool down Z 5mm at a feed rate of 70mm min N4 G01X82 9 Y32 0 F170 0
14. e of program as Z is not in the last example then the previous value of Z is used These are retained or modal values until they are changed by another line of program Some G codes behave similarly e g G90 G91 GOI and G02 Every command code stays effected until cancelled Co ordinate System The system of axes arranged in the Mori Seiki NV4000 and most milling machines of this type is that the Z axis is along the spindle axis vertically upwards the X axis is in the largest slide direction to the right and the Y axis is from the front to the back of the table These axes are determined by the right hand screw direction This means that looking from the top down onto the table the X axis is due east the Y axis is due north and the Z axis 1s towards you These directions are set so that the motion of the tool relative to the table is called positive when it moves in the positive X or Y or Z directions Note that in actual fact it may be the table that is moving while the tool may be stationary but the RELATIVE motion between the two is as described above Absolute dimensions Each position for the tool is specified by giving its X Y or Z co ordinates with respect to a program zero point On the machine when the program is run the program zero is set by the operator according to written instructions supplied by the programmer When absolute co ordinates are used the X Y or Z values are always relative to this zero positio
15. effect after all motion has stopped turns off motors spindle and accessory outlets M03 Spindle Motor On Activated concurrently with motion specified in the program block remains in effect until superseded by another M code M04 Spindle Motor On Reverse As above only in the opposite direction M05 Spindle Motor Off This command turns the spindle off The command is placed as part of the header to ensure that the spindle is in the off position This step is undertaken for safety and for completeness to ensure that the spindle is placed in a nominated position M06 Retract and pause for tool change Generally this statement is found at the end of a sequence which uses the one tool within the program The following sample code illustrates some of the more common control commands on lines N1 N13 and N14 The location of these commands in the program is also typical Sample code NO HOUSING PROGRAM LOMM DIA TOOL program name amp tool used NI M03 spindle on N2 INSERT YOUR PROGRAM IN HERE N12 N13 M05 spindle off N14 MO2 end of program 13 M08 Coolant On M09 Coolant Off Turns the coolant on and off as required M19 Spindle Orientation ON Turns on the feature which allows alignment of a rotating spindle in preparation for a tool change Not always required if a M06 tool change command is used but is included for completeness M30 End of Program and Rewind The M command M30 is similar to a M02 Program End However
16. ering feed in inches per tooth of revolution MRRwin ap W fn N Figure 2 2 or Face Milling MRRwin 12apwn xD fV in min 2 0 7 0 Where N 12V n D In metal cutting a very useful parameter is called the unit or specific horsepower HP which is defined as HP HP MRR hp in min hp 2 0 8 0 Thus this term represents the approximate power needed at the spindle to remove a 1 in of metal per minute Specific horsepower factors for some common materials are given in Table 2 3 Specific horsepower is related to and correlates well with shear stress for a given metal Specific power can be used in a number of ways First it can be used to estimate the motor horsepower required to perform a machining operation for a given material HP values from the table are multiplied by the approximate MRR value for the process The motor horsepower HP is then HP HPs MRR CF E hp 2 0 9 0 29 Values for Specific or Unit HPs for Various Metals during Metal removal BANOR a oe Lo Steels including plain 85 200 Values assume normal feed carbon alloy steel tool ranges and sharp tools Multiply hot or cold rolled or cast value by 1 25 for a dull tool Cast iron 100 190 i 1 0 0 03 0 045 Add 10 for milling to table 190 300 1 4 1 6 0 05 0 07 value Stainless steels 1 150 450 1 2 1 4 0 05 0 068 Iron based alloys 180 320 1 2 1 6 0 055 0 073 Temene temperature alloys Nickel alloys 80 360 1 8 2 0 0 0
17. f a computer package to view machining simulations Some coverage of advanced machining methods using Solidworks CamWorks will also be included Aims The aim of the CNC machining part of MECH3660 MECH5660 is to give students a basic introduction into numerically controlled machine tools such as the Mori Seiki NV4000 mill that are used in practice for producing real products If each student gains some understanding and feel and perhaps some enthusiasm for this area of manufacturing then the main aim of this component has been largely achieved Overview The topic that students will consider in Manufacturing Engineering MECH3660 MECH5660 for 2015 is a connecting rod During semester there will be lectures and tutorials that will concentrate on providing you with the information and time that you will need to produce CNC code for the manufacture of the connecting rod Some emphasis will also be placed on material removal rates and the forces generated during the machining process Some basic coverage of rapid prototyping and the kinematics of CNC machines will also be presented as will an appreciation of the precision accuracy and repeatability of CNC machines Programming the NV4000 mill The CNC part of this course 1s intended to introduce the topic of numerically controlled machines and machining by brief descriptions of the construction and operation of such machines and comparing their function to manual processes In addition sa
18. file outline The following basic systematic operation plan is suggested for you to consider with comments to explain the reasoning behind each step Consider machining the holes before machining the outside profile From a common sense point of view 1f the holes were not machined first the part would fly off after the profile operation 1s over With this thought in mind the following steps are suggested jek a RA DR gde Ra 11 12 13 Clamp the job in position on the machine bed and load the 10mm slot drill into the chuck The tool home position is set at 10mm above the job to enable plenty of clearance for safety Turn the spindle motor on The tool will move at rapid traverse to the first hole co ordinates select the hole closest to the home position and then plunge down at a plunge feed rate to a depth of 10mm below the top of the job Retract the tool up to Z 1mm so that the bottom of the tool is 1mm clear of the job At rapid traverse move to the next hole location Moving in a counter clockwise or clockwise manner repeat the operation for each hole After finishing the machining of the five holes select a point on the outline and rapid traverse to that location This position on the outline must be offset to compensate for the tool radius 5mm Plunge down at a plunge feed rate to a depth of Z 10mm Move the tool at a cutting feed rate around the profile offset 5mm to compensate for the tool diameter After f
19. he likelihood of the cutting tool coming undone Up cut milling Down cut milling Figure 1 3 Geometry or Preparatory Statements G codes These all start with a G and relate mostly to some tool motion The most common of these GOO G01 G02 G03 are all self retained and need not be repeated in consecutive blocks Most geometry codes require co ordinates in Cartesian XYZ form in the same block to indicate the next position of the tool G00 Rapid traverse Rapid traverse will move the tool at the maximum available feed rate on the X and Y axis on the Z axis Rapid traverse is used to reposition the tool in preparation for the next cut or before ending a program Rapid traverse can be used for all tool positioning motions to reduce run time for the part program The GOO code remains in effect until linear G01 or circular G02 603 interpolation is specified Linear or circular interpolation will resume at the feed rate last specified prior to the rapid traverse motion unless a new feed rate 1s specified Rapid traverse is never used for cutting G01 Linear interpolation Linear interpolation is the movement of the tool in a straight line from its current position to a co ordinate location specified in a CNC block Referring to Figure 1 4 and the sample G code Sample code Comments NO M03 set spindle on NI G90 in absolute co ordinates N2 GOO X7 1 Y7 1 Z1 0 move rapid to next position 7 1 7 1 1 0 N3 G01 Z 11 0 F70
20. inishing the machining of the profile retract the tool up Imm above the job and rapid traverse back to the home position Turn the spindle motor off End of program 16 Basic Operations Plan Machining the Holes Figure 1 9 Figure 1 9 1s a subset of the drawing included in Figure 1 7 Figure 1 9 has been redimensioned with all of the dimensions which describe the positions of the holes based from program zero 0 0 0 This figure has been included to give a clearer picture of where all of the holes are located relative to the home position in the XY plane and the path that the cutting tool will take The lines of code listed below represent the CNC code instructions as per the comments described in points 1 through to 7 of the Operation Plan on the previous page NI M03 N2 G90 N3 G00 X92 5 Y 5 0 Z1 0 N4 G01 Z 10 0 F70 0 N5 GOO Z1 0 N6 GOO X27 5 V 45 0 N7 G01 Z 10 0 F70 0 N8 GOO Z1 0 N9 GOO X 18 0 Y45 0 N10 G01 Z 10 0 F70 0 N11 GOO Z1 0 N12 G00 X 88 5 Y 45 0 N13 G01 Z 10 0 F70 0 N14 G00 Z1 0 N15 G00 X92 5 Y 45 0 N16 G01 Z 10 0 F70 0 N17 G00 Z1 0 spindle on in absolute co ordinates rapid traverse to hole 1 stopping 1mm above the job feed tool down Z 11mm at a feed rate of 70mm min rapid traverse up Z 1mm rapid traverse to the location of hole 2 feed tool down Z 11mm at a feed rate of 70mm min rapid traverse up Z 1mm rapid traverse to location of hole 3 feed tool
21. move tool to position 82 9 32 0 at a feed rate of 170mm min N5 600 Z50 0 rapid feed the tool up Z 50 0mm N6 MO5 spindle motor off N7 M02 end of program Feed rates shown by an F code will appear in conjunction with a G01 G02 or G03 code Most G codes are followed immediately by X Y and Z values to show the next physical position of the tool centre There is in every program an arbitrary point called the program zero chosen by the part programmer to which all co ordinates are referred whether absolute or incremental values This point is not referred to in the program but is implied by the co ordinates of the tool path The location of this zero point has to be communicated to the machine operator using a drawing of the part and of the blank as it appears before any machining is done N B For ease of setting up and checking that the program does not send the tool into the machine table the program zero should always be IN THE MIDDLE amp AT THE TOP SURFACE OF THE BLANK If a program is already stored on a USB stick it may be read into the memory of the controller and run In every case the program zero the point from which every co ordinate dimension 1s measured 1s lost if the machine is shut down For this reason the program zero position should be set up at the start of each session The program contained on your USB stick and the machine settings are always independent If a co ordinate is not specified in a lin
22. mple tool path programs for simple illustrative examples are included in these notes The software package CIMCO is available in the Undergraduate Computer rooms 345 S322 and N216 This package allows editing graphical simulation and verification of the CNC code before it is run on the milling machine The example programs included in these notes for the Mori Seiki NV4000 mill have every line fully described These programs may be used as a starting point for writing and checking your own programs for your own needs Students are encouraged to read each program included in these notes and to ensure that they understand what each function does and how it in turn influences the tool s motion The Mori Seiki NV4000 mill Figure 1 0 is a standalone industrial 3 axis machine The instructions are in a systematic CNC machine code form consisting of the so called G amp M codes The main or more commonly used G amp M codes will be covered in the lectures and will be demonstrated via examples It is these codes that most students will use to produces their designs Other less commonly used codes will still be included in these notes for reference purposes Figure 1 0 Mori Seiki NV4000 mill System Specifications Basic Mechanical DADICSIZO nts kaba atg laa ii nais 700 0mm x 450 0mm Throat depth a i l E ie 139 7mm Travel X AXIS aaaaasasaasssaaaadadadaskakaasakaaa 600 0mm Travel Y RA f k a 400 0mm Travel ZA AR 400 0mm ESCUTAS ession aa
23. n irrespective of where the tool is at any given time Absolute co ordinate mode is programmed by the G90 code You may like to refer to Figures 1 2a and 1 2b to clarify this point Incremental dimensions Not recommended for beginners or students This method of identifying the tool position means that the X Y or Z co ordinates are relative to the previous position of the tool Using incremental dimensions sometimes called chain dimensions is very useful where the co ordinates of a radius centre for example is easily determined relative to the last tangent point but is much more difficult to find relative to the zero position Use G91 to set the incremental co ordinate mode You may like to refer to Figures 1 2a and 1 2b to clarify this point Ye P Absolute command gt I 35 2 G90 G00 X 175 0 Y 100 0 250 0 175 0 C 100 0 250 0 eee es 3 XD YO Z0 X175 0 Y100 0 250 0 Workpiece zero point o YO 20 X 175 0 7100 0 Z50 0 eat ae i ne i s iet incremental command gt 690 600 X 175 0 Y 100 0 50 0 11 G91 X350 0 Y0 Z0 xD 200 0 20 X 350 0 10 20 0 0 0 0 Ms Since the commands given in call no axis movement they can be omitted Figure 1 2a Typical example segments of programs that use G90 and G91 commands G90 GOO X10 0 Y10 0 X 20 0 Y20 0 G91 X5 0 Y 30 0 X25 0 Y 10 0 G90 X20 0 Y 10 0 fus i Pj i jif Ta on
24. o Pacha fa Mb jal capability of plunge IG Curie Slotu ari 21 SHORT SERIES 54 56 TIN CENTRE CUTTING METRIC PLAIN SHANK p02 6365 4 ove 6382 4 0102 6999 4 0102 6416 i 4 i 4 il d a 4 i d 4 4 4 4 da 40 025mm 0 02 amp mm da h Sutton Standard Is Sutton Standard 22 LONG SERIES L4 L6 sis CENTRE CUTTING METRIC PLAIN SHANK CNC Qualified End mills feature a Plain shank suit ER or Roll lock style holders Tightly toleranced OD and shank to suit CNG machine tools a Centre Cut full range 4 flute and 2 flute Specially edge conditioned for high performance in light or heavy cuts Eccentric relief for maximum strength behind cutting edge TiCNite coated for superior performance in tool steels dj 0 025en 0 025 da ho ly Sutton Standard lz Sutton Standard 23 LONG REACH L2BN utta METRIC CENTRE CUTTING PLAIN SHANK t K R RJ to Pa ho R A AJ B la Sutton Standard 24 Suggested Spindle Speeds RPM Table ERES Example of Calculation for Cutting Conditions End mill O 20mm KARATTRI Tharefora pega ess A E inte ain F 350RPM x 0 070 x 4 x 0 8 teel H13 Die si 3 Brinell 76 4 mm min Speed Vek 350 APM 20 to 30 Vc Feed per tooth fi 0 070 Cutting Condition C 0 8 roughing side cut Calculation formula for cutting conditions DaN Ve
25. of the machine is therefore HP F V 33 000 hp 2 0 2 0 26 Fo Cutting force Radial force F Tool force Ib F Feed force F Radial force 0 0 100 500 0 01 0 02 0 05 0 1 V Cutting speed ft per min D D gt t Depth of cut in F Cutting force Tool force Ib F Radial force Feed direction 0 001 0 002 0 005 0 01 0 02 f Feed in per rev Figure 2 0 Three measurable components of forces acting on a single point tool oblique machining with effects on the forces of varying speed depth of cut and feed Turning single point tool process Figure 2 1 Basics of the turning process In turning for example where MRR 12 V f d in min 2 0 3 0 HP Fe 396 000 f d hp 2 0 4 0 27 Cutting Speed The cutting speed V can be defined as the maximum linear speed between the tool and the workpiece The cutting speed for drilling turning and milling can be determined as a function of the workpiece or the tool diameter D and the rotation speed N and is given by V nDN 12 2 0 4 1 Metal Removal Rate Metal removal rate MRR is a measurement of how fast material is removed from a work piece The unit of the metal removal rate is usuallv expressed in cubic inches per minute A different formula 1s used for different processes In our case we will generallv consider the milling formula All three terms are included for completeness DRILLING In drilling the cro
26. speed of the cutter drilling amp milling or work piece turning revs per minute D Drill diameter inches 1 inch 25 4mm 1 cubic inch 16 39 cubic centimetres 1 pound force 4 46 newtons 1 foot per minute 0 3048 metres per minute 1 foot pound per minute 0 0226 watts 1 horsepower 745 7 watts The cutting force system in a conventional oblique chip formation process is shown schematically in Figure 2 0 Oblique cutting has three components 1 Fo primary cutting force acting in the direction of the cutting velocity vector This force is generally the largest force and accounts for 99 of the power requirement by the process 2 Fr feed force acting in the direction of the tool feed This force is usually about 50 of F but accounts for only a small percentage of the power required because feed rates are usually small compared to cutting speeds 3 Fv radial or thrust force acting perpendicular to the machined surface This force is typically about 50 of Fr and contributes very little to power requirements because velocity in the radial direction is negligible Figure 2 0 shows the oblique geometry and Figure 4 1 also shows the general relationship between these forces and speed feed and depth of cut These figures cannot be used to determine forces for a specific process as the following discussion will explain The power required for cutting 1s P F V ft Ib min 2 0 1 0 The horsepower at the spindle
27. spindle speed override knob on the control panel 14 Example of a profile cut program The drawing below Figure 1 7 describes a profile that 1s to be machined Note the following points e The profile is to be manufactured from 10mm thick Perspex stock e The cutting tool available will be a 10mm slot drill slot drill tools have the ability to cut both down and across their blades e To simplify this first example the method of holding the job down is not considered e Note that program zero the origin of the co ordinate system is located at the centre top of the object This point can be referred to as 0 0 0 Figure 1 7 Figure 1 8 The example in Figure 1 7 shows the X and Y plane on top of the object Figure 1 8 shows the orientation of the positive and negative axis relative to 0 0 0 The Z axis is positive out of the page This axis convention 1s referred to as the right hand rule The tool s movement in the Z axis will be mainly to lift and clear the tool as it moves to the next cutting region 15 Basic Operations Plan Consideration must now be given to what steps must be performed in order to machine this part This part of the exercise is called the operations plan The operations plan describes in step by step text format all the procedures involved in machining a stock piece of material to a finished product Careful examination of the drawing Figure 1 7 shows that the part is comprised of five holes and the pro
28. ss sectional area of the chip is 7 D 4 Where D Drill Diameter inches V Feed Rate inches per min f Feed inches per revolution N Rotational Speed revolutions per minute Hence MRRprin a D 4 Ve a D 4 f N Because N 12 V n D MRRprin D 4 f 12 V x D MRRprin 3 Df V in min 2 0 5 0 28 TURNING For turning the chip width is Do Di 2 where Do and Di are the outer and inner work piece diameters respectively The cross sectional area is n D D 4 Therefore the material removal rate is Where D Outer Diameter of the work piece inches D Inner Diameter of the work piece inches Vr Feed Rate inches per minute f Feed inches per revolution N Rotational speed of the cutter drilling amp milling or work piece turning revs per minute V Speed feet per minute MRR torn 1 Do Di 4 Ve 7 Ds Di 4 fN Because N 12 V a Do Di 2 MRR urn 6 Do Di f V in min 2 0 6 0 MILLING In a milling process the chip cross sectional area is as per Figure 2 2 below Where ap depth of cut inches w width of cut inches n number of teeth in cutter D cutter diameter inches f feed in per tooth per revolution inches V speed feet per min Vr feed rate in per min A cross sect area of cut a w squared inches a cutting width MRRmin ap W Vr Also used when consid
29. ted by the available power dmax HP E 12 HP V fr CF inches 2 0 11 0 30 References Writing CNC code e NV Series User s Manual Mori Seiki Editing and Simulating Machining e Blackwoods Publication Sutton Tools 1997 13 Cooper St Smithfield Sydney Force and Power in Machining e Materials and Processes in Manufacturing Eight Edition 1999 E Paul DeGarmo J T Black and Ronald A Kohser Chapter 21 Section 21 5 Energy and Power in Machining Pages 607 610 ISBN 0 471 36679 X e Computer Aided Manufacturing Third Edition 2005 Tien Chien Chang Richard A Wysk Hsu Pin Wang Pages 195 204 Pearson Prentice Hall ISBN 0 13 129334 6 Manufacturing Processes e Manufacturing Engineering and Technology Sixth Edition 2010 Serope Kalpakjian Steven R Schmid ISBN 978 0 13 608168 5 e Guidance Note 6 Post Weld Heat Treatment of Welded Structures Welding Technology Institute of Australia WTIA February 2003 31
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