FANUC Series 16/18/160/180-Model C for Lathe Operator Manual

PROGRAMMING
9. COORDINATE VALUE
AND DIMENSION
B–62754EN/01
102
Either inch or metric input can be selected by G code.
G20 ;
G21 ;
Inch input
mm input
This G code must be specified in an independent block before
setting the coordinate system at the beginning of the program.
After the G code for inch/metric conversion is specified, the unit of input
data is switched to the least inch or metric input increment of increment
system IS–B or IS–C (Section II–2.3). The unit of data input for degrees
remains unchanged. The unit systems for the following values are
changed after inch/metric conversion:
– Feedrate commanded by F code
– Positional command
– Work zero point offset value
– Tool compensation value
– Unit of scale for manual pulse generator
– Movement distance in incremental feed
– Some parameters
When the power is turned on, the G code is the same as that held
before the power was turned off.
WARNING
1 G20 and G21 must not be switched during a program.
2 When switching inch input (G20) to metric input (G21) and
vice versa, the tool compensation value must be re–set
according to the least input increment.
However, when bit 0 (OIM) of parameter 5006 is 1, tool
compensation values are automatically converted and
need not be re–set.
CAUTION
Movement from the intermediate point is the same as that
for manual reference position return. The direction in which
the tool moves from the intermediate point is the same as
the reference position return direction, as specified with bit
5 (ZMI) of parameter No. 1006.
NOTE
1 When the least input increment and the least command
increment systems are different, the maximum error is half
of the least command increment. This error is not
accumulated.
2 The inch and metric input can also be switched using setting
of data setting (III–11.4.3).
9.2
INCH/METRIC
CONVERSION
(G20, G21)
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