ACU-RITE CNC 3500i - Manual (Page 226)

200 7 Programming: Canned Cycles, sub-programs
7.
3 Pr
obing Cy
cles
Tool Probe Cycles
Before using your tool probe and tool probe cycles, you must setup
the probe following the probe manufacturer's specifications.
The tool probe updates the tool registers only. If you are going to use
the tool being measured after the probing cycle, you must recall that
tool for the new offsets to be active.
For tool probing, Tool-Length Offset (TLO) is the distance from
machine home to top of work piece or wherever you wish to set your
part Z zero or if used in conjunction with a Z axis work offset, a fixed
surface on the machine.
Before starting to set your tools, you must calibrate the probe. Once
the probe has been calibrated, calibration does not have to be done
again unless you remove the probe or replace the stylus.
Recalibration may also be required if the Z location of the top of the
part changes, and is not compensated by a Z work offset shift.