Plasma made in a barn as cheap as possible :) and it's not going smooth

phillc54 wrote:

Well everyone is wiser after the event, it is a pity it took almost 18 months for this to show up. I certainly don't remember anyone complaining about the upper limit until recently.

Yeh, I think its only come to a head becasue people are pushing the envelope with HF start machines instead of blowback torches.
The HF machines must be much more erratic with torch voltage. But allowing it to be set to 9999 should have solved the issue
Sorry I never thought to look at it earlier but it stood out immediately when I saw Fred's post.

I am hoping the arc voltage blows the cobwebs out of the system so it reports a clean voltage signal without significant variations. If it doesn't, I think the work done inside the plasma need to be reviewed.

This afternoon i'm stripping the plasma cutter, probing where i can get a clean voltage reading. But i get the same on the IGBTs, the feedback coils, the torch nozzle, etc.....so i think it's inherent to the design of this machine.

but does it vary much when cutting when you scope it?

Rod, problem solved

I still have around 15v on the nozzle, but now it's firing up in mode 0
Did 2 things :
_set the upper limit to 300 (maxed out) and lower to 50
_opened the cutter, again, and connected right after the 2 big chokes and i had a bunch of various MOV on hand so i changed those on the torch/ground connections to a lower voltage while testing the cutter, and found-out that a 250v MOV works perfectly.

After all that the ARC OK signal based on the THCAD voltage is good, fires 100% of the time.

Now i need to find a table to help me out with the various voltages depending on the thickness for the THC control and the tool table.

BTW do i need to fiddle around with the PID / GAIN section of the configuration panel ( i did and it's all messed up i guess) ?? and still waiting on some larger metal sheets to adjust off of it.

Oh i forgot the "dive" when starting the cut was from my probing sensor, the offset was off by 3 mm ...........typical PEBKAC ......

jay1st wrote:

Rod, problem solved

After all that the ARC OK signal based on the THCAD voltage is good, fires 100% of the time.

Now i need to find a table to help me out with the various voltages depending on the thickness for the THC control and the tool table.

There are no shortcuts here, in the absence of manufacturer's cut charts, you need to do test cuts. Pick a height, write a gcode file that cuts a few lines about 6 inches long at different speeds. Pick the cleanest cut with the best angularity, use that height and then repeat the same process with that speed at different heights. Then you might need to repeat with a finer resolution between cuts.I suspect this might be a bit fiddly with Plasmac as it does not allow z axis code so you might have to write a materials file for each different option and change the material between cuts from the gcode.

that's what i was afraid of ...........

Yes it was close to the diodes, and now it's connected close to the massive chokes.

Could i use a Hyperthem table with speeds and rates depending on thickness as a base to start with ?