Cnc Programming Basics

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CNC Programming Basics

Program structureEvery program consists of:1. Program Start

The program start is the program number. The program number begins with character/letter O.

2. Program ContentsNC blocks

3. Program EndM30 for a main programM17 for a sub-program

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CNC Program Numbers

Program Numbers

O6999 . . .O0256O0255 . . .O0000

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CNC Program Blocks (1)

• N is the address• Block numbers from

N0000 to• N9999• A block consists of

number and words• Words are contents of a

block• Block numbers are

selected in the jumps of ten for the purpose of insertion

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CNC Program Blocks (2)

• A block consists of one or more blocks

• A Word consists of a character (address) and a number.

• Every address has a certain meaning, on which the corresponding number depends

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CNC Prg. Syntax Regulations

• The maximum block length must not exceeded four lines. If max. length exceeded alarm 650 occurs.

• Every block starts with a block number.• After the block numbers follows the G

command.• Words consists of coordinates X(U), Z(W).• For G02, G03 program interpolation parameter

I and K are placed after X(U), Z(W).• The F word (feed, thread pitch).• The S word (cutting speed).• The T word (tool address).• The M word (additional functions).

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Absolute Value Programming

P0 N… …P0 P1 N… G01 X40. Z25. F…P1 P2 N… G01 X60. Z-40. F…P2 N… …

Absolute coordinatesystem

Example:

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Incremental Value Programming

Incremental coordinatesystem

Example: P0 N… …P0 P1 N… G01 U5. W-25. F…P1 P2 N… G01 X10. Z-15. F…P2 N… …

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Mixed Programming

Mixed coordinatesystem

Example: P0 N… …P0 P1 N… G01 U5. W-25. F…P1 P2 N… G01 X60. Z-15. F…P2 N… …

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Self-holding Functions (1)

• The majority of G and M commands and other words are self-holding, remain active until overwritten or deactivated/deselected.

• Aimed to simplify and to reduce programming tasks. Example: G41 can be deactivated by issuing G40 command.

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Self-holding Functions (2)

Take-over of G00 commands in block N0110In block N0120 G00 is deactivated by G01. G01 is active.

N0100 G00 X50. Z+10.N0110 X36. Z+2.N0120 G01 X40. Z-10. F…

N0050 M03N0060 … …N0120 M04

Example 1:

Example 2:

M03 activated at N0050 and effective from N0050 through N120. M03 deactivated at N0120 by M04 command

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Reference Points

M = Machine zero point.(unchangeable ref. Point determined by machine manufacturer)N = Tool mounting reference pointW = Work piece zero point. (can be freely determined by the programmer and can be moved within program

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Work piece (1)

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Work piece (2)

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G & M Commands

G00: Rapid traverseG01: Linear interpolationG02: Circular interpolation clockwiseG03: Circular interpolation counter clockwiseG70: Measuring in Inch (USA)G71: Measuring in mm (Other countries)

M03: Spindle ON clockwiseM04: Spindle ON counter clockwiseM20: Tailstock backM21: Tailstock forward

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G00, Rapid Traverse

Absolute dimensions of the target point coordinates:N030 G90N040 G00 X48 Z-26An absolute X coordinate related to the diameter.

Incremental dimensions of the target point coordinates:N030 G91N040 G00 X-10,5 Z-31

Tool position X69 Z5

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G01, Linear Interpolation

P0: tool position

G90:N030 G00 X39 Z2N040 G01 X39 Z0N050 G90N060 G01 X48 Z-37G91:N030 G00 X39 Z2N040 G01 X39 Z0N050 G91N060 G01 X4.5 Z-37

G01 X… Z…

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G90 & G91 Commands

G90G01 X+140 Z-90 Target point abs.

G91G01 X+40 Z-60Target point incr.PO: Start Point

P1: Target Point