Fanuc Series 15i/150i-MA (Programming) Operators Manual

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Linear interpolation can be commanded by specifying axial move
following the G31 command, like G01. If an external skip signal is
input during the execution of this command, execution of the command
is interrupted and the next block is executed. The skip function is used
when the end of machining is not programmed but specified with a
signal from the machine, for example, in grinding. It is used also for
measuring the dimensions of a workpiece.
G31 IP_ ;
G31 : One-shot G code (If is effective only in the block in
which it is specified)
The coordinate values when the skip signal is turned on can be used in
a custom macro because they are stored in the custom macro system
variable #5061 to #5080, as follows : (In a system with more than 20
axes, #100151 through #100174 are used.)
#5061 1st axis coordinate value
#5062 2nd axis coordinate value
#5063 3rd axis coordinate value
#5080 20th axis coordinate value
The feedrate of the block in which G31 is specified may be one of the
following, depending on the setting of the bit3 (SKF) in parameter No.
1400 :
(1) Feedrate specified by F (The feedrate may be specified either
in or before the block containing the G31 code.)
(2) Feedrate set in parameter No. 1428
- Servo delay compensation
When a skip signal is entered, the CNC internally stores the current
position. However, the current position stored in the CNC includes a
servo system delay, so that the current position is shifted from the
machine position by the servo system delay. This shift amount can be
found from the positional deviation value held in the servo system and
the number of remaining pulses due to a feedrate increase/decrease
made internally by the CNC. When this shift amount is considered, the
need to include a servo system delay in a measurement error is

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