G31 uses machine coordinates?

[kerryveenstra]

I have successfully connected a touch probe to the accessory socket, but the coordinates of a successful probing are not as expected. I do this:

g0 z0
g31 z-0.5 (probe downward)

After the probe trips, parameter #2002 is supposed to be the Z coordinate of the location at the time the probe tripped (section 7.7.12 of the manual). And so I expect this command to do nothing:

g0 z#2002

If the program coordinates are the same as the machine coordinates, then the result of the g0 above is just a *tiny* movement, probably correcting for the probe having overshot or having backed off slightly.

But if the program coordinates are not the machine coordinates, the command g0 z#2002 causes a downward movement.

1. Is this expected operation?

2. Am I using g31 correctly?

3. What is the best way to get the program coordinates of the probing?

Thanks,

Kerry

[kerryveenstra]

I've confirmed through the MDI in the Offsets screen of Mach 2 that G31 definitely returns its probe results as machine coordinates. I can program for machine coordinates (yuck!), except that the tool-length offsets won't be automatic. Unless there's another way to do this, I'll end up copying tool length info into the G-code program, and I'll always need to confirm that the work offsets are 0,0,0 before running the program.

I hope there is a better way. I'll post what I learn.

Kerry