Long time since my last post, but we the problem actually was in old Mach3 version. Purchased & upgraded to the latest one and THC works almost smoothly.
There is now only one problem with homing of Z axis- when the Z axis position is increased by THC (plate warped upwards) and the cut is finished, when the cutter moves to next piercing point, it triggers a limit switch when homing Z axis (I have modified the Sheetcam post processor to home the axis on each cut).
It seems to me that the problem lies in fact, that THC correction value is not added/subtracted from Z axis position in Mach 3. After cutting, the real position of Z axis might be 10mm (from initial plate position), but Mach thinks it's 4mm. Now, if the plate below the next cut has also warped a bit upwards, when homing through 3mm (G28.1 Z3.00) it might trigger the limit switch before the middle point is reached - and that triggers a limit switch instead of home switch (floating head with a single switch). Isn't there a command in Mach3 that will home the axis, regardless where it's located without going through a middle point?
This is the problematic part of generated G-code:
This is full code we were running:
N0450 (Operation: No Offset, Layer1, T1: Plasma, 3 mm kerf)
N0470 G00 Z30.0000
N0480 X294.4400 Y59.7263
N0500G92 G28.1 Z3.00
N0510 G92 Z0.0
N0520 G00 Z0.0000
N0530 G92 Z0.0
N0540 G00 Z6.0000