Quote Originally Posted by Davek0974 View Post
The post processor I have been looking at uses g31 z -100 to drop the torch until the probe switch changes state, g92 z0.0 to zero, then g00 z25.00 to raise it by the preset distance, g92 z0.0 to zero the z axis and g00 z1.00 to preset the pierce height.

this is from sheetcam, will that not work in mach3??
Ok well G92 is an Offset Coordinate from the exisiting coordinate point. What it's doing is using the probe to find the material surface and where ever that coordinate falls in the current WORK Coordinate system (G54) then it sets an offset coordinate value. (g92 z0) then Moves 25 away(g0 z25) resets the offset coordinate to Zero at this point (g92 z0) then moves to 1mm above this (g0 z1).

It doesn't actually Zero the DRO or should say Set the Zero WORK coordinate. It just applies an offset Coordinate from this WORK coordinate. If you cancel the Offset by using G92.1 you'll see the True WORK coordinate.

Try it in MDI in simulation mode. First make sure any Offsets are cancelled by typing G92.1
Next Zero the Work coordinates by zeroing the DRO's then jog a set distance away say 10mm positive.
Now type G92 z0 and you'll see the Z dro change to 0 now type G0 z5 which will simulate movement 5mm positive.
Now Cancel the Offset with G92.1.? . . . . Now you'll endup with 15mm positive in the Dro which is the true WORK coordinate. 10mm we started with plus 5mm the offset moved away from it's zero Offset coordinate.

To be honest using coordinate offsets is not the best way to do it and can easily get you in trouble with other g-code files because they stay in affect if not cancelled. This can lead to unexpected movements and crashes.!!