8396-8000
June 1999
OPERATION
3.7 PROGRAM F ORMAT
Program format, or style, is an important part of CNC machining. Each individual will format their programs
differently and, in most cases, a programmer could not identify a program written by themselves. The point is
that a programmer needs to be consistent and efficient, writing code in the way it is listed and in the order it
appears in the program. For example:
X, Y, Z is in order of appearance. The machine will read X, Y, or Z in any order, but we want to be consistent.
Write X first, Y second, Z third.
The first line or block in a program using active G codes should be a tool number and tool change command.
This would be a good safety measure.
The second line or block will contain a rapid command (G00), an absolute or incremental command (G90,
G91), a work zero for X and Y (G54), a positioning X and Y coordinate, a spindle speed command (S____), and
a spindle ON clockwise command (M03).
The third line or block will contain a îš“Read tool length compensationîš” command (G43), a tool length offset
number (H01), a Z-axis positioning move (Z.1), and an optional coolant ON command (M08).
An example programîš’s first three lines will look like this:
T1 M06;
G00 G90 G54 X0 Y0 S2500 M03;
G43 H01 Z.1 M08;
All the necessary codes for each operation are listed above. This format is a good practice and will separate
your style from other programmers.
QUESTION:
If G00, G90, and G54 are defaults, why do we list them in the second line of a program and for each different
tool?
ANSWER:
G00, G90, and G54 are listed for an operator/setup personîš’s aid. They show that the machine will rapid
position, that the machine is in the absolute coordinate mode, and most important, the work zero coordinates.
The work zero is always different between setups, and multiple work zeros are very common.
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