plasma touch off for cnc4640 controller

Hi have built a 8x4 router/plasma table, most things going well but would like to add touch off height setting, sounds like the controller won't do the gcode G28.1 G90
has anyone got one going on plasma, every thing else is working well,

thanks

Do you have any of the required hardware for the touchoff? You'll need something like an ohmic sensor or floating torch to do it.

yes got all sensors etc , its the gcode the cnc4640 doesn't know?

runs standard gcode and i can cut parts and route parts fine, just wanted to add initial torch hight, at start of cut

looking at using a XPTHC-4 torch hight controller , but doesn't really connect that well to the 4640

Have you tried using G31 for probing? It would probably be something like "G31 Z-10." which would send the Z in the negative direction for 10 units and it will stop whenever the probe input is activated. After that you'll need a "G92 Z0." if using something like an ohmic sensor or "G92 Z-.5" if you were using a floating torch that traveled .5 before activating the probe.

Attachment 410884got round the problem by purchasing a THC unit works great but modify the Z axis for plasma as I thought someone was going to purchase the machine,
so building an other table slightly bigger, with plasma / router in mind again, just made modify a china spindle for ATC works great, Attachment 410880Attachment 410882

John are you still around? getting ready to hook up our acorn / plasma and may have a few questions for you.