Machining centers that have fixture offsets (also called coordinate system
shifting) allow the user to specify the position of the program zero point
within offsets, keeping the assignment of program zero separate from the
Zero Points allow parts to be programmed without regard for their position
on the machine or to machine more than one part on the machine without
re-coding all the points.
It is common for six zero points to be available, but this varies from
control to control. The commands to activate them are usually G54, G55, G56,
G57, G58 and G59. The X, Y and Z values in the Zero Point become the new
zero position when the command G5x is used and all axis movement is now
relevant to this new position until either another zero point is activated
or the zero point is cancelled with a G53 command.
The G53 command makes all axis moves relative to Machine Zero. This is used
for tool changing and work piece changing.