I'm working on making a torch height control for Mach3.

Does Mach not have a built in THC DELAY. Judging by what I read in the documentation it seems the THC becomes active as soon as Mach gets the ARC OK signal. However the torch could still be in the middle of a pierce and you don't want to have THC moves then.

I've got a Candcnc system and it has a user adjustable THC DELAY. I think from when the ARC OK is recieved the THC ignores any UP/DOWN signals for the duration of the THC DELAY setting. The DRO code is OEM 177 which is just a reserved DRO, so I'm guessing that the THC DELAY is part of the Candcnc plugin and not native to Mach3.

I can get around this easily enough by programming it into the THC controller, but just want to double check first that Mach doesn't have anything built in.

Keith.

Going into it in a little more detail, here is how the THC operation is described in the Mach2 manual (italics):

1.   The part program moves the torch at Safe Z to the start of the cut then moves to Z = 0
     (This is pierce height).

2.   It then executes M3 ("spindle start") to start the arc. Mach2Mill stops executing the part program and completes the torch switch circuit. Piercing starts.
      
3.   When the THC interface detects that the arc is good it signals this to Mach2Mill which switches on the torch height servo and resumes execution of the part  
      program. This can have a short Dwell (G4) or immediately commence the first move for the cut.

4.   Whenever the height servo is on it will sample the Torch Up and Torch Down inputs. If Torch Up is active then the Z axis will move in the plus direction at the rapid  
      feed rate multiplied by the Correction Speed percentage DRO. Similarly Torch Down will move in the minus Z direction.

The way it's worded sounds to me like as soon as the ARC OK is recieved, the THC will respond to the UP/DOWN signals. My plasma cutter puts the ARC OK signal out very quickly after the TORCH ON signal is given, so I can see the THC reacting in the middle of a pierce when the voltage is sky high, and driving the Z down while piercing.

Have I got any of that wrong

Keith.

Looks like it does exist. The documentation I was reading was obviously older stuff.

I've found OEM DRO 177 is "Torch Pierce Delay", but can't find any explanation of how it operates in Mach. The name "Torch Pierce Delay" is not very indicative of it being a THC Delay, where it does not react to the THC UP/DOWN signals for its set duration.

But then again, neither is THCOn for the ARC OK signal 

Keith.

Keith Mach3 has a long history of having unusual NAMES for functions. You kinda have to get inside of Arts head to understand his method of function naming. Remember he is Canadian and the language is different.  Close but not the same.

Things like I say X Zero he says X ZED.

(;-) TP

I've got a Canadian mate. I'll have to give him a call and see if he can teach me the language 

Keith.

Hi all,
Did you ever figure this out? I've noticed that my machine seems to ignore the Z move from pierce height to cut height after M3 when THC is activated. I think this is similar to what you were describing.

The pierce height delay IS to allow the pierce to finish before motion begins. When Mach3 gets the ArkOK signal this delays motion until it times out allowing the ARC voltage to stabilize before the THC UP/DOWN takes over.

(;-) TP

What I have been finding is my pierce delay works but my movement begins from pierce height instead of moving to the cut height first. It seems to only do this when THC is ON. Tomorrow morning I am going to try using M667 (EndTHC()) after M3 (torch on) and the M666 (StartTHC()) after the Z move to cut height to see if does what it should.

Adding the StartTHC() and EndTHC() seems to work for allowing the machine to first move to cut height before THC is active