8. COORDINATE VALUE
Either inch or metric input can be selected by G code.
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–A or IS–B
(Section 2.3). The unit of data input for degrees remains unchanged.The
unit systems for the following values are changed after inch/metric
– 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.
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 reset.
3 Reference position return is performed at a low speed for
the first G28 command after the inch input is switched to the
metric input or vice versa.
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
2 The inch and metric input can also be switched using