Accuracy

[Rolfey]

Hi All,

I've been working on a home built plasma machine, using a Hypertherm Powermax 65. Everything works OK, but I'm really wanting to dial the machine in a bit more and try to get it to cut smoother. I have attached some pictures, you'll notice an inconsistent cuts when performing arcs/circles and a little bit of extra kerf I suppose. It's also hard to tell if the machine feels jerky when putting my hand on the torch during a cut.

Any guidance is appreciated!

[DDoug]

found this problem on a torchmate table.

Burned out test circles, until I found the slop in one axis.

The pinion was loose on the shaft, no key applied, they jammed the set-screw into
the motor shaft keyway. So there was a little back/forth slop.

Your problem looks identical.

[Rolfey]

That makes total sense! I'll check the pinions tomorrow morning, but I know for a fact that the set screws would be hard against the shaft.

Did you create a keyway, or change the pinion to suit?

[DDoug]

Torqued them in tighter, might have used loctite as well.
Not my machine, just got it up and running, and then owner sold it.

[bLouChip]

I built my CNC plasma as well, and it also has laser and milling swap-able heads. As such, I have discovered axis acceleration config in the grbl controller to be a huge factor in how smooth the XYZ axes move through corners, cutting smooth curves and straight lines on entrance and exit of corners. When running plasma and routing processes, because of the mass of the heads and resulting mechanical resonance when direction change occurs, I dial down the XY axes acceleration configs to 400mm/sec2, but when running laser (a much lighter head weight) I can dial it up to 800 or 1400mm/sec2 depending on the motion patterns of the job.

So once you make sure pinions or gears and belts are tight and tensioned correctly, then perhaps experiment with axes acceleration values.

Also, consider taping a marking pen to the torch and you can test and dial in the motion using paper instead of cutting steel.