Chapter 3_NC Programming

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Chapter 3

NC part programming

Type of programming

1. Manual part programming

2. Computer assisted part programming

1. Manual part programming

Machine instructions are written on a special form called manuscript.

NC tape is directly made from manuscript.

two categories of manual programming jobs:-

1. Point-to-point jobs.2. Contouring jobs.

Part program formats

1. Fixed Block Format

a) Fixed Sequential Format (Fixed Block)

Ex: N010 G00 X10 Z0 F60 S800 EOBN020 G01 X20 Z0 F60 S800 EOB

b) Tab Sequential Format (Fixed Block)

Ex: N010 G00 X10 TAB Z0 TAB F60 TABS800 EOB

2. Word Address Format (Variable block)

N020 G01 X20 TAB Z-5 EOB

Ex: N010 G00 X10 Z0 F60 S800 EOBN020 G01 X20 EOB


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NC programming buildup

Dimensional Tool word

n g x y z a f s t m

Sequencenumber

Rotationalaxis

SpindleSpeed (rpm) Miscellaneous

function

Preparatoryfunction

Feed(tool movement mm/min)

1. Sequence number (n)

Initiate the block. To identify specific machining operations.

2. Preparatory word (g)

prepare the MCU circuits to perform a specific mode of operation.

ex: go2- prepare the NC controller unit for circularinterpolation along the arc in CW direction.

Miscellaneous Words ,m

The miscellaneous function words consist of two digits.

This function pertains to auxiliary information which does not relate to

dimensional movement of the machine, such as spindle command.coolant on and off. and other functions.

It should be noted that the m00, m01, m02, m06, and m30 areexecuted only after completion of all other commands in the block.

Dimensional words

distan ce dim en sion words c ircular dimen sion word s an ular dim en sion al word

classificationof

dimensional words

Type title here thread-cutting dimension word Type title here


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COMPUTER-ASSI STED PARTPROGRAMMI NG

Computer-assisted part programmingUsed for complex,tedious and time consuming jobs .

machine instructions are written in English-like statement of the NCProgramming language, which are then processed by the computerto prepare the tape.

Basic steps:-

.2. Specifying the operation sequence and tool

path

1. Defining the work part geometry

Work art com osed of basic eometric elements.

Any component can be described by points, straight lines,circles, cylinders and other mathematical defines surface.

Each geometric element must be identified and the dimensionsand location of the element explicitly defined.

Steps in computer assisted part programming

Part pr ogrammers job

APT programming

Computers job

Inputtranslation

Arithmeticcalculations

Cutteroffset

Postprocessor


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NC part programming languages

1. APT (Automatically Programmed Tools)2. ADAPT (Adaptation of APT)3. EXAPT (Extended subset of APT)4. UNIAPT (developed by UNIted Computing Corp.)5. SPLIT (Sundstarnd Processing Language Internally Translated).

7. PROMPT8. CINTURN II

APT Language

APT is an NC lan ua e/ com uter ro ram ca able of

performing calculations to generate cutter positions

based on APT statements.

APT is a 3 D system.

more than 400 words in the APT language.

Four types of statements in APT Language:

1. Geometry statement or definition statements

2. Motion statement

3. Postprocessor statements

4. Auxiliary statement

Geometry Statement

.

Tool is directed to move to the various point and along surfacesof the work part.

Syntax of Geometry statement:-

Symbol= geometry type/ descriptive data


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Symbol= geometry type/ descriptive data

Identify the geometry element.

Combination of


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LINE:LINE: (cont.)(cont.)

5. B a oint and bein arallel to andperpendicular to another line-L5=LINE/P2,PARLEL,L3L6=LINE/P2,PERPTO,L3

6. By being tangent to two circles-L7

L9L8

= / , , , , ,L8=LINE/LEFT, TANTO,C3,RIGHT,TANTO, C4L9=LINE/RIGHT, TANTO,C3,LEFT,TANTO, C4L10=LINE/RIGHT, TANTO,C3,RIGHT,TANTO, C4

L10

C3 C4

CIRCLE: used to define a circle in xy-plane.

. y e coor na e o e cen er an e ra us.C1=CIRCLE/ CENTER, 2.0, 1.0, 0.0, RADIUS, 2.0C1=CIRCLE/2.0, 1.0, 0.0, 2

2. By the center point and the radiusC1=CIRCLE/ CENTER, P1, RADIUS, 2.0

3. By the center point and tangent to a line.C1=CIRCLE/ CENTER, P1, TANTO, L2

4. B the three oint on the circumference

C1=CIRCLE/ P2, P3, P4

P4

P1

P3

P2 C1

CIRCLE: used to define a circle in xy-plane.(cont.)

5. By intersecting lines and radius-

C2=CIRCLE/XSMALL,L2,YSMALL,L3,RADIUS,0.375C3=CIRCLE/YLARGE,L2,YLARGE,L3,RADIUS,0.375C4=CIRCLE/XLARGE,L2,YLARGE,L3,RADIUS,0.375C5=CIRCLE/YSMALL,L2,YSMALL,L3,RADIUS,0.375

C3

C4

C5L2

C2

L3

PLANE: Used to define a plane.

. . .

PL1=PLANE/P1,P2,P3

2. By a point and being parallel to another plane-

PL2=PLANE/P4,PARLEL,PL1

3. By 2 points and being perpendicular to anotherplane-

PL3=PLANE/PERPTO,PL1,P5,P6

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PLANE: Used to define a plane..

planes

PLANE/PARLEL, PL1, (XLARGE or XSMALL), offset distance between planes

YLARGE or YSMALL

ZARGE or ZSMALL

Example

MOTION STATEMENT

-

motion command/descriptive data

Types of MOTION STATEMENT:

.tool at the desiredpoint.

2.contouring motion statement: for cutting operation.

Point-to-Point motion statement

FROM/symbol for a defined point indicates the initial position of the cutter

GOTO/ symbol for a defined point positions the tool center at a specified point

GODELTA/X,Y,Z positions the cutter in the specified incrementfrom its current location.

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Contouring Motion Statements

.

3 surfaces control the tool motion in contouring:1. Part surface (tool end/base moves)2. Drive surface (guides the side of the cutter)3. Check surface(stop the movement of the tool)

Initial motion statement:

GO/cutter specifier, drive surface, cutter specifier,partsurface, cutter specifier, check surface

Cutter Specifier

TO ON PAST

TAN TO

Intermediate Motion Statement:

Actual cutting is controlled.

There are 4 variant if intermediate motion statements in APT.most useful is given below:

:

motion word/derive surface, cutt er specifier,check surface

Motion Words:

GOLFT, GORGT, GOFWD, GOBACK, GODOWN, GOUP

GOFWD

GOUP

GOBACK

GOLFT

PREVIOUS CUTTER MOTION

GODOWN

Cutter

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EXAMPLE:-. r e an anguage e mo on s a emen requ re o mac ne

the part shown in figure. The part surface is called PLN.

Solution:

GO/TO, L1, ON, PLN, ON, LLGORGT/L1, TO, L2GORGT/L2, TANTO, C1GOFWD/C1, TANTO, L3

C1

, ,

GPLFT/L4, PAST, L5GOLFT/L5, PAST, L6GOLFT/L6, PAST, LLGOLFT/LL, PAST,L1GOTO/SP

Additional APT Statement:-os processor s a emen s: to control the operation of the spindle,

the feed, and other features of the machine tool.first statement :

MACHIN/Processor name

COOLNT/SPINDL/ Descriptive data are required after slash (/).

FEDRAT/TOOLNO/

RAPIDEND

Additional APT statement (cont.)

Auxiliary statement:- tolerance specification

OUTTOL/ affects overcutting;

INTOL/ affects undercutting

TOLER/ outer and inner tolerance are equal.

Cutter specification

CUTTER/(upto 7 arithmatic parameters)

(where first is the cutter diameter)

CLPRNT

Additional APT statement (cont.)

n a an erm na on s a emen

PARTNO PROGRAMMING EXAMPLE (INITIAL)

FINI (TERMINATION)

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Structure of APT program

PARTNO/ part number and nameMACHIN/postprocessor nameDescription and definition of the PART GEOMATRYCutter and Tolerance specifications

Motion StatementsSpindle and Coolant offFINI

Macro Statement in APT.

To repeat motion statement several times within the program.To reduce the total number of statements in the program.Job of part programmer becomes easier and quickly.Format:

Symbol=MACRO/parameter definition(s) [1]

// set of APT statements //

TERMAC [2]To activate the MACRO subroutine within the APT program.

CALL/ symbol, parameter specification [3]

Example of MACRO statement

=GOTO/PXGODELTA/0, 0, -1.0

GODELTA/0, 0, +1.0TERMACFROM/P0CALL/DRILL PX=P1CALL/DRILL, PX=P2CALL/DRILL, PX=P3GOTO/P0

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Example 2

Geometry Statement

PO=0,0,0

P2=POINT/20,20,0

L1=LINE/P2, 20,100,0

L2=LINE/20,100,0,ATANGL,45

P1=POINT/110,20,0

C1=CIRCLE/90,110,0,20

C2=CIRCLE/CENTER,P1,RADIUS,20

L4=LINE/P1,PERPTO,(LINE/XAXIS)L3=LINE/50,130,0, PARLEL, (LINE/XAXIS)

PLO=PLANE/P2,P1,PO

PL1=PLANE/(0,0,-0.5), PARLEL,PLO

Motion StatementFROM/PO

CUTTER/20

TOLER/0.01

GO/TO,L1,ON,PL1,ON,L5

GOLFT/L1,PAST,L2

GORGT/L2,PAST,L3

GORGT/L3,TANTO,C1

GOFWD/C1,TANTO,L4

GOFWD/L4,PAST,1,INTOF,C2

GORGT/C2,PAST,L5

GORGT/L5,PAST,L1

GODLTA/0,0,8

GOTO/PO

Examples:3

Write geometry statement in APT Language for the following Part.

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Example: 4

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Chapter 3_NC Programming