APT.pdf

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COMPUTER AIDED PART

PROGRAMMING - APT

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Methods of NC Part Programming

1. Manual part programming

2. Manual data input

3. Computer-Aided part programming

4. Part programming using CAD/CAM

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Manual Part Programming

• Variety of CNC machine tools and equal variety

of controllers

• part program for a little complex parts

– Extensive calculations – Error prone

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Computer Aided Part Programming

• Use of part programming language:

– use an “English-like” programming language – More than 100 part programming languages

developed in the last 50 years – describe

• geometry of the part • tool motions

• machining parameters, and • all other auxiliary operations

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APT-Automatically Programmed Tool

• A compiler for simplifying NC Programming

• Developed by MIT in 1955, refined in early 1960’s

• Most widely used part programming language

• Other languages developed as variants

– APT (Automatically Programmed Tools)

– AUTOSPOT (Automatic System for Positioning Tools) – COMPACT II

– ADAPT (Adaptation of APT)

– EXAPT (Extended Subset of APT) – FAPT (Fanuc APT)

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Why?

• Use of symbolic language

• Programming independent of machine tool

• Reduced programming time

• Reduced possibility of human error

• Capability of simple changeover of machining

sequence from machine to machine

• Only postprocessor required to include new

machine tool

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Role of part programmer

• Define the geometry of the workpiece in terms of

basic geometric elements such as point, lines,

circles, planes, etc.

• Specify the tool motion and/or operations to

guide the too along the geometric elements

defined earlier in order to machine it

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Role of computer

• Input translation

– Covert the part program into computer usable format for further processing

• Arithmetic calculations

– complex arithmetic and trigonometric calculations to generate the part surface data

• Cutter offset computation

– Generate the CL data after considering the tool geometry

• Postprocessing

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Engineering Drawing

Develop process plan for the part

Write a part program using APT language

Process part program

-generate CL data Diagnostics Correct the part program

Post process the CL Data for a specific machine tool

Part program

Generation of CL Data

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APT language features

• Major words -

left of slash, special meaning

• Minor word – right of slash

• Symbols -

geometric elements, numerical values

L2=LINE/(POINT/100,40),PERPTO,L1

• Subscripted Symbols

• Numbers

• Angles –

decimal degrees

• Arithmetic operators:

+

--

* / **

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APT Statement Types

• Postprocessor (feed, speed, coolant, … etc.)

• Auxiliary (tool, tolerance, part, … etc.)

• Geometry statements

• Motion statements

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Postprocessor Statements

COOLNT/ : coolant to be turned on or off:

COOLNT/ MIST

COOLNT/ FLOOD

COOLNT/ OFF

UNITS

UNITS/METRIC/INCH

RAPID

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Postprocessor Statements

FEDRAT/ : feedrate for moving the tool along the part surface

FEDRAT/ 75,MMPM

SPINDL/ : spindle rotation in revolutions per minute

SPINDL/ 850,RPM

SPINDL/ON

LOADTL/ : load a specific tool from an ATC tool changer

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Auxiliary Statements

MACHIN: specify machine tool and call the postprocessor

MACHIN/ MILL, 3

PARTNO: part program number, inserted at the start of the program.

PARTNO EXAMPLE6

PRINT: Display of tool geometry on screen (ON/OFF)

PRINT/ON

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Auxiliary Statements

CUTTER:

cutter diameter for offset

CUTTER/ 46

TOLERANCE : Nonlinear motion accomplished

with straight-line segments

INTOL/ 0.015

OUTTOL/ 0.01

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OUTTOL Specified path Specifie d path INTOL

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Geometry statements

General format

<Symbol>=Geometry/Definition & Modifiers

Modifiers

INTOF PARLEL PERPTO TANTO

LARGE SMALL LEFT RIGHT XLARGE

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• Point

POINT

• Line

LINE

• Plane

PLANE

• Circle

CIRCLE

• Pattern (of parts)

PATERN

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Geometry statements:

POINT

• Cartesian coordinates

PTA = POINT / 40,10,0

• Center of a circle

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Geometry statements:

POINT

• Polar coordinate

PTI=POINT/XYPLAN,RTHETA,45,-30

• Intersection of two lines

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Geometry statements:

POINT

• Intersection of a line and a circle

PTC=POINT/XSMALL,INTOF,LIN1,C1

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Point (POINT)

PTC = POINT/ YLARGE, INTOF, LIN3, C1

PTC = POINT/ XLARGE, INTOF, LIN3, C1

PTD = POINT/ YSMALL, INTOF, LIN3, C1

PTD = POINT/ XSMALL, INTOF, LIN3, C1

x PT C PT D LIN 3 _C 1 y

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Geometry statements:

LINE

• Two points

• One of the coordinated axes

• Passing through a point and parallel to a line

• Passing through a point and perpendicular to a

line

• Passing through a point and at angle with a

line or axis

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Line (LINE)

LIN1 = LINE/ P1, P2

P1 P2 y x LIN1

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Line (LINE)

LEFT or RIGHT modifiers indicates whether

L1A

C11

L1A = LINE/ PT51, LEFT, TANTO, C11

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Geometry statements:

LINE

• LIN1 = LINE/P1,LEFT,TANTO,C1

• LIN2 = LINE/P1,RIGHT,TANTO,C1

• LIN3 = LINE/P2,RIGHT,TANTO,C1

• LIN4 = LINE/P2,LEFT,TANTO,C1

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Geometry statements:

LINE

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Line (LINE)

L8=LINE/RIGHT,TANTO,C3,LEFT,TANTO,C4

C3 L6 L9 C4 L8 L7 Right Left Left Right

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Geometry statements:

CIRCLE

C1 = CIRCLE/ 70, 60, 5, 40.3

PT3 (70,60,5) C1 y x 40.3

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Geometry statements:

CIRCLE

C3 = CIRCLE/ CENTER, PT6, TANTO, LN4

C7 = CIRCLE/ CENTER, PT8, PT5

C3 Y X LN4 PT6 C7 PT8 PT5 Y X

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Geometry statements:

PLANE

• PLAN1 = PLANE/P1,P2,P3

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Motion Statements - PTP

Rapid from current position to a specified location

FROM/

<point location>: starting point for the tool, with

the end of the tool at that point.

GOTO/

<point location>: rapid, straight- line move to the

point specified in absolute mode.

GODLTA/

<coordinate increments>: move incremental

distance from the current position.

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Z

Y

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Continuous Path Motion Commands

GOLFT/

_{: Move left along the drive surface}

GORGT/

_{: Move right along the drive surface}

GOFWD/

_{: Move forward from a tangent position}

GOBACK/

_{: Move backward from a tangent position}

GOUP/

: Move up along the drive surface

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PARTNO EXAMPLE5 $$POSTPROCESSOR STATEMENTS CLPRNT MACHIN/MILL,3 INTOL/0 OUTTOL/0.01 PRINT/ON $$ GEOMETRY STATEMENTS SP=POINT/0,0,10 P0=POINT/-70,-140 ZSURF/-10

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$$ CIRCLE DEFINITIONS C1=CIRCLE/0,0,30 C2=CIRCLE/-100,80,25 C3=CIRCLE/-100,-80,25 C4=CIRCLE/100,0,30 $$ LINE DEFINITIONS L1=LINE/RIGHT,TANTO,C1,LEFT,TANTO,C2 L2=LINE/LEFT,TANTO,C1,RIGHT,TANTO,C3 L3=LINE/LEFT,TANTO,C2,LEFT,TANTO,C4 L4=LINE/RIGHT,TANTO,C3,RIGHT,TANTO,C4

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$$ TOOL PATH DEFINITION CUTTER/20 LOADTL/1 SPINDL/1200,RPM,CLW COOLNT/ ON $$ MOTION STATEMENTS FROM/SP RAPID TLLFT GOTO/P0 GODLTA/-20 AUTOPS GO/TO,L4 FEDRAT/50

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$$ CONTINUOUS PATH MOTION STATEMENTS GOLFT/L4,TANTO,C3 GOFWD/C3,TANTO,L2 GOFWD/L2,TANTO,C1 GOFWD/C1,TANTO,L1 GOFWD/L1,TANTO,C2 GOFWD/C2,TANTO,L3 GOFWD/L3,TANTO,C4 GOFWD/C4,TANTO,L4 GOFWD/L4,TANTO,C3

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GODLTA/20 GOTO/P0 COOLNT/OFF SPINDL/OFF RAPID GOTO/SP

END $$ End of this program FINI $$ End of APT processing

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CL File

$$ GEOMETRY STATEMENTS SP=POINT/0,0,10 *SP .0000 .0000 10.0000 P0=POINT/-70,-140 *P0 -70.0000 -140.0000 .0000 ZSURF/-10

$$ ALL GEOMTERY DEFINITIONS HAVE Z=-10 $$ CIRCLE DEFINITIONS

C1=CIRCLE/0,0,30

*C1 .0000 .0000 30.0000

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CL File

$$ LINE DEFINITIONS L1=LINE/RIGHT,TANTO,C1,LEFT,TANTO,C2 *L1 .2288 .9735 .0000 30.0000 L2=LINE/LEFT,TANTO,C1,RIGHT,TANTO,C3 *L2 -.2288 .9735 .0000 -30.0000 L3=LINE/LEFT,TANTO,C2,LEFT,TANTO,C4 *L3 .3497 .9368 .0000 64.9739

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CL File

$$ CONTINUOUS PATH MOTION STATEMENTS

GOLFT/L4,TANTO,C3 *FEED -87.7591 -112.7897 -20.0000 GOFWD/C3,TANTO,L2 *CIR -100.0000 -80.0000 35.0000 CLW -108.0074 -45.9283 -20.0000 GOFWD/L2,TANTO,C1 *FEED 4.5756 -19.4695 -20.0000 GOFWD/C1,TANTO,L1 *CIR .0000 .0000 20.0000 CCLW