qtplasmac 2.10 arc ok, thcad thc, and Thcad Ohmic troubleshooting help needed.

Well I made that one line code change and........ She works!!!!!! Cut a project with 500ish pierces and all was great.

Got a backlog of parts to cut so will keep everyone updated on how well she is working. So far it cut for about an hour with only one minor hiccup (arc ok didn't transfer so the torch didn't start cutting). THC and ohmic worked amazing! No stops because of those two. It was crazy watching the steel bend while it was being cut and the torch followed the height perfectly. With just the float switch this wouldn't happen and the float switch would trip stopping the cut. Due to float flexing the sheet in an inconsistent manor.... With ohmic....No diving, no probing issues....nothing... it just worked.....frankly I was amazed.... And it was wicked fast too....gonna keep turning it up cause why not! Clearly ohmic can handle it.

I did pause the program every now and again and checked the ohmic voltage. What was interesting is sometimes it was the 15 volts or so but next time I paused it.... Nothing it was back to zero. So whatever slag builds up seems to get shot out before it completely shorts the torch out..... Which is awesome! I will cut a full 8x4ft sheet in the next few days and report if that hysteresis problem shows up..... But honestly I doubt it after seeing it build up then return to zero in a 4x4ft sheet.

Thanks for the help everyone.

As a side note/side project. I might attempt later. I bet we can do ohmic with the arc voltage. Add a 500k resistor between the torch and the shield. Add the 24v ps with 24+ and some resistor....would try 24k....to the table and - to the torch. Make the ohmic component link to the arc voltage (which now displays the 24v of the ps) and whenever the arc voltage goes to zero you know your on the material. Eliminates ohmic thcad entirely and should do the same thing.

Thanks for the words of warning! Will post docs here before attempting anything too crazy.


Agree on the resistor values, will keep an eye out on my table. I dont have a water table but will bring in wet sheets of steel every now and again. Will calibrate then.

I posted the doc changes on git, might as well post that ohmic bug fix as well?

That would be great. The docs are in the comp anyway.
There is no need for you to use the ohmic3 comp without any water.

I am upgrading the table to include a 4th axis rotary and figured i would update the system to debian 12 while at it and provide a update on how things went. 

I forgot to push that update, if it wasnt made will push it when i go to debian 12. 

Well its been a while but here are the results of ~ 1 year of use. (see pic)
a little over 8.4 miles of cutting or 13.4 km, and about ~53k pierces. 
torch was on for 63 hours. 

ohmic has worked flawlessly in all kinda of weather (rain/snow)/ well below freezing to very hot. (table under a carport so kinda exposed to the weather),. I much prefer ohmic as i full rapid for each pierce so times are ~1 sec instead of the ~3-4 that probing takes.....when doing ~53k peirces that saved a day worth of run time!

a few bugs i ran into, not sure if they have been fixed as i am on the same version (been to big of a chicken to update... trying to keep up with orders so didn't want to break things) 
1. sometimes when using ohmic touchoff it would hit a pile of junk, bird poop, etc , and ohmic would not sense. This would cause the float switch to trip but it wouldn't continue...... would just get stuck. pause, unpause, stop, restart from line, etc nothing would make it pierce. Would required a full reset of linuxcnc, disabling ohmic, allowing it to pierce, with float, then going back to ohmic mid program. This happened ~25 times. every now and then it would work with the float if ohmic failed but not usually (or maybe i just didn't notice until it failed) 
2. z axis, if failed to home (broken stepper wire) would still cause the x and y axis to move even after it failed!!!!!! had this happen twice over the last year with the thin nema 17 wires breaking at the connectors after all those pierces. 
3. i have a custom user button to move the table to origon. However their is no way to stop the machine from software after that command has been sent (left parts on the carriage a few times whoops) requiring the estop to be hit, when a simple pause or cancel would have worked great. 


Missing Features (hope this is around now)
the biggest one is when the program is paused (cause the tip is burnet out), not being able to move to a specific location to make changing tips easy. 


Below is my current ohmic setup via a terrible paint drawing if anyone wants to replicate my setup.

5x5k 1w resistors for ~25kohm (22.5k in reality)  between v+ of power supply and in- of thcad.. The table connects to -in at the thcad as well
1x250kohm resistor between thcad v+ of power supply and in+ of thcad
power supply v- to torch (ohmic shield) 

With this setup when the torch is full of junk it reads ~24v letting you know the torch is messed up while allowing ohmic probing to continue
 

Will post those files this evening.

Yep x and y would keep moving even after the z failure.

I'll try cycle stop in Debian 12 I think I tried it in the 2.10 pre version I was running and no luck. I saved that hdd so if you need any info from it will pull it back in.

Awesome on the change consumables, will give that a shot.

Agreed, I know of a few machines where this would cause significant damage. If nothing else it should be a default with the ability to disable.

I've got a few linuxcnc machines I don't mind helping test. I can code ok but cant find files for the life of me in Linux (C# windows guy). If someone can point me in the right area I'll do some digging.