B-63324EN/03 PROGRAMMING 8.COORDINATE VALUE AND DIMENSION
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8.3 INCH/METRIC CONVERSION (G20,G21)
Either inch or metric input can be selected by G code.
G20 ; Inch input
G21 ; 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 (See II-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
- Workpiece 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.
G20 and G21 must not be switched during a program.
When the input unit is switched between inch input
(G20) and metric input (G21), a workpiece origin
offset value and tool offset value are automatically
converted according to the selected input unit; those
values need not be set again.
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
settings. (See Operation II-12.2.1)