G20 Select Inches / G21 Select Metric (Group 06)
The G codes G20 (inch) and G21 (mm) codes are used to ensure that the inch/
metric selection is set correctly for the program. Selection between inch and
metric programming should be done using Setting 9.
G28 Return to Machine Zero Thru Optional G29 Reference Point
(Group 00)
G28 is used to return all axes to machine zero, unless an axis (or axes) is
specied, in which case only that axis (or axes) is returned to machine zero.
G28 cancels tool length offsets for the following lines of code.
.
Example 1
Work Offset G54: Z = 2.0
Tool 2 Length: 12.0
Program segment:
G90 G54;
G43 H02;
G28 Z0.;
G00 Z1.
The G28 block will move to machine coordinate Z = 14.0 before moving to Z =
0. The following block (G00 Z1.) will move to machine coordinate Z = 1.