Inch/Metric Command Change; G20, G21 - Mitsubishi Electric MELDAS C6 Programming Manual

5. Position Commands

5.2 Inch/metric command change; G20, G21

Function and purpose
These G commands are used to change between the inch and millimeter (metric) systems.
Command format
G20/G21;
G20
G21
Detailed description
G20 and G21 selection is meaningful only for linear axes and it is meaningless for rotary axes.
The input unit for G20 and G21 will not change just by changing the command unit.
In other words, if the machining program command unit changes to an inch unit at G20 when the
initial inch is OFF, the setting unit of the tool offset amount will remain metric. Thus, take note to the
setting value.
(Example 1) Relationship between input command units and G20/G21 commands
Input command
Axis
unit type (cunit)
X
Y
Z
X
Y
Z
(Note 1) When changing between G20 and G21 with program commands, it is necessary in
(Example 2) Input setting unit #1015 cunit=10, #1041 I_inch=0
(Note 2) Since the data before the change will be executed at the command unit after the change,
: Inch command
: Metric command
(with decimal point input type 1)
Command
example
10 X100;
10 Y100;
10 Z100;
1 X100;
1 Y100;
1 Z100;
advance, to convert the parameters, variables, and the offsets for the tool diameter, tool
position, tool length, to the units in the input settings of the input setting unit system (for
each axis) that have inch or metric commands, and make the settings using the
parameter tape.
Position command unit ..... 0.001mm
Compensation amount setting unit
In the above example, when changing from G21 to G20, the compensation amount
must be set to 0.002 (0.05 ÷ 25.4
command the F speed command for the change so that it is the correct speed command
for the command unit system applied after the change.
5.2 Inch/metric command change
Metric output (#1016 iout=0)
G21 G20
0.100 mm 0.254 mm 0.0039 inch
0.100 mm 0.254 mm 0.0039 inch
0.100 mm 0.254 mm 0.0039 inch
0.0100mm 0.0254 mm 0.00039inch 0.00100inch
0.0100mm 0.0254 mm 0.00039inch 0.00100inch
0.0100mm 0.0254 mm 0.00039inch 0.00100inch
..... When the compensation amount is 0.05mm for
0.001mm
.
=
0.002).
.
20
Inch output (#1016 iout=1)
G21 G20
0.0100 inch
0.0100 inch
0.0100 inch