Computer Aided Part Programming

 

COMPUTER AIDED PART PROGRAMMING (APT LANGUAGE) BY S.R.CHAUHAN MED NIT HAMIRPUR

 

COMPUTER AIDED PART PROGRAMMING 

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Computer aided part programming computer is used to generate the part program to machine the components. The process of generating part program is  partially done by the programmer and partially  by the computer

 

COMPUTER AIDED PART PROGRAMMING 

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Part programmer’s job in the computer aided of part  programming is to first define part geometry the component from the component drawing. Geometry of shape is split into simple elements like  points, lines, arcs, full circles, distances, directions and these elements are assigned specific numbers to identify there positions. Programmer can see the geometric construction on the VDU depending on the system capability

 

COMPUTER AIDED PART PROGRAMMING 

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Second function of the programmer is to give additional information regarding the machining sequence, type of operation, tool sizes etc. From the geometry system generate the data for machining machini ng called cutter location (CL). The data generated upto the point is independent of the machine and can be used on any machine capable of doing the required operations.Data does not contain G and M codes. CL data is post processed in the computer to translate into a form which a particular machine control system can understand. Post processing involves addition of G codes and other machine dependent information. Part programming at this stage is machine dependent and used by the specific machine only.

 

Advantages ofProgram computer Aided Part 

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Part programming is simplified Part program generated are accurate and efficient All the arithmetic calculations are done by the computer,resulting in saving time and elimination of error The part program for different machines can be done by a single person which can then be post processed for specific machines.Such system can deal with many axis for simultaneous movement.

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If new machines are added, only a post processor may be needed to integrate the new machines to the existing systems.

 

Computer Aided part programming languages 

Large no.of part programming languages have  been developed to meet particular needs.

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Most widely used languages are: APT

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COMPACT-II

 

Automatically Programmed Tools(APT) 

Most widely used and comprehensive language

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APT is 3-Dfive system controlling axis.and can be used for 

In APT programming it is assumed that work  piece remain stationary and tool moves

 

APT Statements 

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Geometry Statements:these are also called definition statements and are used to define geomtric elements elements like point,line,arc,circle and plane. Motion statements:The motion statements are used to define the cutter path. Post Processor statements:These statements are machine tool specific and are used todefining machining parameters like feed,speed,coolant on/off etc. Auxilliary statements:These are miscellaneous statements

 

Geometry statements 

General form of APT Geometry statement is: Symbol=geometry type/descriptive data 

 p=POINT/x,y,z - a cartesian point

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 p=POINT/l1,l2 - intersection of two lines

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 p=POINT/c - the center of a circle

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 p=POINT/YLARGE, INTOF,l,c INTOF,l,c - the largest y intersection of a line and a circle *Note: we can use YSMALL,XLARGE,XSMALL in  place of YLARGE

 

Lines     

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L1=LINE/x1,y1,z1,x2,y2,z2 - endpoint cartesian components L1=LINE/p1,p2 - endpoints L2=LINE/p,PARLEL,Ll - a line through a point and parallel to another line L3=LINE/p,PERPTO,Ll - a line through a point and perpendicular to a line L4=LINE/p,LEFT,TANTO,c L4=LINE/p,LEFT,TANT O,c - a line from a point, to a left tangency point on a circle L5=LINE/p,RIGHT,TANTO,c - a line from a point, to a right tangency point on a L5=LINE/p,RIGHT,TANTO,c circle L6=LINE/LEFT,TANTO,c1,LEFT,TANTO,c2 L6=LINE/LEFT,TANTO,c1,L EFT,TANTO,c2 - defined by tangents ta ngents to two circles L7=LINE/LEFT,TANTO,c1,RI L7=LINE/LEFT,TANTO,c1,RIGHT,TANTO,c2 GHT,TANTO,c2 - defined by tangents to two circles L8=LINE/RIGHT,TANTO,c1,LEFT,TANTO,c2 L8=LINE/RIGHT,TAN TO,c1,LEFT,TANTO,c2 - defined by tangents to two circles

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L9=LINE/RIGHT,TANT L9=LINE/RIGHT,TANTO,c1,RIGHT,TANTO,c2 O,c1,RIGHT,TANTO,c2 - defined by tangents to two circles

 

Circle  

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C1=CIRCLE/x,y,z,r - a center and radius C2=CIRCLE/CENTER,p,RADIUS,r - a center point C2=CIRCLE/CENTER,p,RADIUS,r po int and a radius C3=CIRCLE/CENTER,p,TANTO,l C3=CIRCLE/CENTER,p,TA NTO,l - a center and a tangency to an outside line C4=CIRCLE/p1,p2,p3 - defined by three points on the circumference C5=CIRCLE/YLARGE,l1,YLARGE,l2,RADIU C5=CIRCLE/YLARG E,l1,YLARGE,l2,RADIUS,r S,r tangency to two lines and radius *Note: we can use YSMALL,XLARGE,XSMALL in  place of YLARGE

 

More complexare geometric constructions possible  

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PLANE/ - defines a plane QUADRIC/a,b,c,d,e,f,g,h,i,j - define a polynomial using values GCONIC/a,b,c,d,e,f - define a conic by equation coefficients

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LCONIC/p1,p2,... - defines a conic by lofting (splining)  points RLDSRF/ - a ruled surface made of two splines

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POLCON/ define a surface using sections PATERN/ -- will repeat a motion in cross a linear or circular array

 

Motion Statements     

FROM/p - specify a start point FROM/x,y,z - specify a start point GOTO/p - move to a final point GOTO/x,y,z - move to a final point GOTO/TO,p - move until the tool touches a point

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GOTO/TO,l GOTO/TO,c -- move move until until the the tool tool touches touches aa line circle GOLFT/l1,TO,l2 - go on the left of l1 until the tool touches l2

 

Motion Statements 

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GORGT/l1,TO,l2 - go on the right of l1 until the tool touches l2 GOBACK/l1,TO,l2 - reverses direction along l1 to l2 GOBACK/l1,TO,c1 - reverses direction along l1 to c1 GOUP/l1,TO,l2 - goes up along l1 to l2 GODOWN/1l,TO,l2 - goes down along l1 to l2 GODLTA/x,y,z - does a relative move  Note: TO can be replaced with PAST, PAST, ON to change whether the tool goes past the structure, or the center stops on the structure.

 

Motion Statements 

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The following commands will create complex motion of the tool POCKET/ - will cut a pocket PSIS/ - will call for the part surface

 

POST PROCESS STATEMENTS 

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CUTTER/n1,n2 - defines diameter n1 and radius n2 of cutter MACHIN/n, m - uses a post processor for machine `n', and version `m' COOL/ANT/n - either MIST, FLOOD or OFF TURRET/n - sets tool turret to new position

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TOLER/n FEDRAT/n- sets - setsa atolerance feed rateband n for cutting SPINDL/n, CW - specifies n rpm and direction of spindle

 

AUXILIARY STATEMENT   

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REMARK - starts a comment line that is not interpreted $$ - also allows comments, but after other statements  NOPOST - turns off the post processor that would generate cutter  paths CLPRNT - prints a sequential history of the cutter center location SQRTF(n) - calculates the floating point square root FINI - stop program PARTNO/n - allows the user to specify the part name LOOPST and LOOPND - loop instructions RESERV/n,m - defines an array of size `n' by `m' JUMPTO/n - jump to line number

 

EXAMPLE