Good day.
Anyone who has a good running plasma where the THC works good.
and willing to share your sheetcam path rules?
I cut alum and it warps …so I need a working THC it seems to me… that my sheetcam rules is preventing my THC to work correctly.
On a job after 30 cuts I only saw the THC indicated down only once and I had to stop
after 2 crashes…the target and the the voltage are close.
Attached are the ones that I use…
Not ignoring you, I would like to help on this one but I’m not using SheetCAM or Mach-4, so I don’t have any constructive input there. Hopefully others that are using that combo will have some input…
Over here a ~20yr old CAD package is beging used. The CAD package is not plasma aware, so the output is used for it’s definition of the path only. That output G-Code, ‘path’, is then run through an external ‘post-post-processor’ that inserts the necessary touch-offs, speed adjustments for consumables, voltages, currents, pauses, etc into the G-Code. The AVIDcnc here is still running with Mach-3 and it has been doing a good job. I can confirm that the THC hardware itself is responsive enough to sense and deal with thinner metal pulling up (heat distorting) when cutting out longer shapes, like 1/2in-wide x 3.5ft-long strips that tend to bend up a large amount when one cuts out large numbers side by side.
Hello, yes I do cut a fair amount of steel and aluminum using Sh*tcam and Mach4. Yes, I use the rules that AvidCNC shipped and added a few of my own for cutting small holes in steel.
Warping is kind of what aluminum does. Keep it nearly submerged and move faster I guess?
Maybe you shouldn’t use any of the rules, follow your plasma maker’s recommendations for pierce and feed rates and try cutting that way. THC should remain on for the vast majority of the cuts for that.
You could have a bad THC sensor if it keeps crashing.
For me, plasma has always been pretty reliable. Never crashed it but have collided with tip-ups. Holes look like garbage but that’s because we are missing voltage, current and gas flow regulation via ModBus (Google “Hypertherm Jim Colt True Hole” for more info).
As much as I hate Sh*tcam, Fusion 360 doesn’t support us yet. They claim they are going to add the missing stuff someday…
Don’t hold your breath.
Thank you!
I am trying to eliminate all possible errors…as I wait for a new pc. (Which I do think is part of the problem)
Strangely enough the plasma seemed to work better when the machine was new…
I do not have a water table yet…so I am using sheetcam minimize thermal distortion option…
I also did reduce the rules…after the pc there is not much more to replace…but Mach4…and that is a route I do not want to go unless I really need to…
When it cuts it does it beautifully…
Have you replaced your consumables since you got it?
@davidcnc, Good question and I am not answering for @ROTM here, but just curious, do you find there to be a connection between the THC diving and consumables completely worn out?
If so that would cause me to question a whole lot of things.
I’m still using Mach-3 and there the THC feedback is pretty darn active and I see it compensating real time as the cut conditions change. I tend to run my consumables until they are WAY past their normal pull schedule (when possible)(having achieved just north of 500pierces on a single electrode) but often up to 400 or a little more. (I get into weird cases where I’m cutting expanded or perforated steel and the high frequency start keeps kicking back on) I do notice a huge difference in cut quality and slag, etc. on worn consumables, but I have not noticed any relationship to THC crashes. Other than tip-ups and figuring out a problem with the routing of the ground sense wire back to the THC, I just don’t have those. I’m runing my plasma table at least every other weekend and often with friends and neighbors, multiple jobs on a weekend. So I would be interested if others are having issues? The only times I seem to have problems is when I forget to move the ground clamp(w/return sense line) to the part and leave it connected to the tank wall. Hasn’t happened in a long, long time but when I was learning, I did that a time or two and the sheets I’ve messed up were expensive enough that I learned my lesson quickly. Since then though, I’ve made many hundreds of parts (mild steel, thick & thin, stainless and aluminum) without incidence.
I think that is one of the reasons I’ve been such a big hold out on Mach-3. It is working, working well (for the things I use it for) and I haven’t found the killer-app / feature to push me to wanting Mach-4 yet.
Oh! Good call!
Also check the wire lead for the THC sensor. Make sure it still has a good connection to the torch and that the ohmic shield isn’t corroding or worn.
I see so many people’s plasma setups where they never clean it or keep the parts in good condition. There was a YouTube channel where a guy was asking if he should get a new plasma CNC and I commented and said, “You should be arrested for abusing you dern machine. Had you kept the one you had clean it would have lasted forever.”
Well, he did not like that response! 
But good catch @davidcnc It may not be this issue but it is THE place to start when you see issues like that.
ADDITIONAL: I made an error above, not just the Ohmic shield but more importantly the Ohmic Retainer Cap;
I have in the past and once I got into the habit of replacing everything referred to as “Ohmic” when they start getting grungy I never see it. But that dern lead that goes to the Ohmic Retainer Cap can also significantly degrade over time.
Consumables have been replaced many times…Mach4 acting weird…but that is probably my computer and it will be replaced…hopefully everything will be ok.
I’ll have to keep a better eye on this. I just don’t seem to have THC issues, so maybe I shouldn’t poke the sleeping bear. 
Got a new PC …last crash was machine, computer everything.
So I waited for the new pc to arrive reinstall everything…Finally I could finish cutting a plate I had on the machine…The only thing now is to fine tune the THC it seems to follow the plate going down but not reacting quick enough going up…any tips?
Tnx.
