168
G CODES
96-8000
June 1999
INCH / METRIC S ELECTION (G20, G21)
G20 Select Inches Group 06
G21 Select Metric Group 06
The standard G codes G20 and G21 are sometimes used to select between inch and metric BUT, in this
control, the G20 (inch) and G21 (mm) codes can only be used to ensure that the inch/metric setting is set
correctly for that program.
Selection between inch and metric programming can only be done from the Setting 9.
REFERENCE P OINT D EFINITION AND R ETURN
G28 Return To Reference Point, set optional G29 REFERENCE point Group 00
The G28 code is used to return to the machine zero position on all axes. If an X, Y, Z, or A axis is specified on
the same block, only those axes will move and return to the machines' zero point. If X, Y, Z, or A specifies a
different location than the current position, then the movement to machine zero will be through the specified
point. This point is called the G29 reference point and is saved for use in G29. If no X, Y, Z, or A is specified,
all axes will be moved directly to machine zero. Any auxiliary axes (B, C,...) are returned to home after the X,
Y, Z, and A axes. G28 also cancels tool length offsets.
G29 Return From REFERENCE point Group 00
The G29 code is used to move the axes to a commanded X, Y, Z, or A position. The axes that are selected in
this block are moved to the G29 reference point saved or recorded in G28 and then moved to X,Y,Z or A
specified in the G29 command point. The positions are interpreted in the current coordinate system.
SKIP F UNCTION (G31)
G31 Feed Until Skip (This G-code is optional and requires a probe) Group 00
F Feed rate in inches (mm) per minute
X Optional X-axis motion command
Y Optional Y-axis motion command
Z Optional Z-axis motion command
A Optional A-axis motion command
The skip function is a non-modal operation that causes a linear move to the specified X, Y, Z, and A position. It
applies only to the block in which G31 is specified. A feed rate must be defined previously or in this block. The
specified move is started and continues until the end point or the skip signal. The skip signal is a discrete input
that usually indicates that the end of travel has been reached; this is usually a probe. The keypad will beep
when the end of travel is reached. Cutter compensation may not be active during a skip function. M78 or M79
may be used to test if the skip signal was received.
An M75 can be used to mark the probed point as the reference point for G35 or G136.
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