THC Setting Issue?

[Davek0974]

Hi all

after doing some nice work on my little CNC plasma table, I have now got a job which uses all of its travel capacity.

The steel is a bit bowed, probably max 4-5mm variation so not too bad across 625mm.

What happened on the first cut was that it started out perfectly then the cut started losing penetration intermittently, my guess was that the THC was not tracking properly the bow in the sheet and i ended up with too high a cut.

I am stuck between it being the cheapo Proma THC i bought, or a setting issue.

In Mach i have the THC anti-dive at 90% and THC Z rate at 7%.

The rate was low because before it seemed to be overshooting, i.e. the THC loop could not keep up with torch travel and was adjusting too much, too late.

I think the Z axis screw is 2mm pitch and direct drive from a small Nema23 motor.

Maybe the rate is too low, the THC is crap, or something else is not right.

As this is my first table, I have no idea how much travel a THC is supposed to compensate for so I'm not sure where to pin the blame.

Any tips would be much appreciated.

I have no objection to getting a new THC but must know before if it is the right thing.