THC and touch off problems.

[ShopTeacher76]

I was wondering if anyone could help me. I am trying to get my first cnc plasma table up and running again. I built it with a precision plasma DIY kit using a CandCNC Bladerunner control. It has DTCII THC on it. I am using SheetCAM and Mach3 to program and run it. I am currently having two issues:

First... I can't find a post in sheetcam that has a touch off commend in it, which i believe is a G28 or G31...??? Mach3 shows that it is recieving the input from the z touch off switch in the floating head.

Second... I can't get the THC to work. I am not showing any voltage when I fire the torch. I am receiving a voltage from the plasma cutter where cpc cable enters the THC module (checked it with my multimeter). I can't find any of my old manuals.

Any help would be greatly appreciated.

[acourtjester]

So you know the G-code G28 and G31 are looking for a different input signal. The G28 is a homing switch for touch off would be the Z home, most ue a floating head switch for that. G31 is a probe input and most use a Ohmic sensor for that. With Mach you can put all home/limit switches in series on one input pin ( I do it that way) and an Ohmic sensor will be a separate input pin. You can have both where the floating head would be a safety if the Ohmic sensor failed.
Here are some Post Processors that you can use, the one labeled with backlash is for the floating head and the others are for Probe. If you edit them you can look down at the "Open Down" section and see which G-code they use.

Mach 3 withTHC edited with switch backlash.zip

posts.zip

[acourtjester]

I use a similar CandCNC electronics package (DTHC-VI) on the module that the plasma signal connected to had a small switch on the back. The switch was for sending a test signal with a set voltage to the controller for checking the wiring.
This manual may help you somewhere near page 14 is the test switch info, this is a download from the Google drive.

[ShopTeacher76]

I figured out the right post to use. Now I will have to find out why my voltage DRO isnt showing anything.

[tcaudle]

Yoou can get rapid help on the CandCNC support forum . The link is in the SUPPORT section of the website. Yes, you have to join and be accepted (we stop an average of 5 to 7 spammers a day ) but its free and there are 3500 members with our products. DTHCII is old and not many know how to use it . Its a parallelport system and uses the MACH3 internal THC logioc not the later direct loop of the DTHC IV and DTHC5. A touch off from code is pretty easy and the SheetCAM MP1000 THC POST has that appraoch. Using a probe command is a little more difficult.

We try not to use Plasma Spider as a support forum for our specific equipment