Hole Irregularities

[TrinityFabworks]

Have any of you had a problem with your small circles having almost like a triple backlash situation? Usually with normal backlash it will make more of an oval than anything. As of lately I'm getting more of a triangulated backlash type of deal going on. Any ideas?

[adbuch]

I would suggest installing a pen holder (Sharpie) in place of your torch and letting your machine draw these circles, as well as some other shapes. This may help you to confirm and isolate if this is a mechanical issue.
David

[sonbakler]

Ya, I'm with Dave on the pen holder to see if is in fact sloppy motion or a wandering arc. Is that the backside or front side of the plate?

[mdwalker]

Try running your holes at 60% of your normal cut speed.

[Rodw]

A collapsed bearing somewhere?

[Deezl Smoke]

Try running your holes at 60% of your normal cut speed.

I've tried that and many speed variations and still have the same issue as Trinity. I've reversed the cut direction, as well as turned DTHC off, but to no avail. Same issues as well as diameter is always more than kerf width small. New electrodes, new nozzles etc. Hypertherm 105 @ 480v. 50' mechanical torch with 50' toolset. Arclight arcmax table. Using qcad, sheetcam, and CandCNC Linux.
Set to begin cut in center of circles smaller than 2". One thing I have used to some advantage, is over cutting by the material thickness.

[weldguy]

Have you tried the pen holder idea mentioned above? If you can securely hose clamp or tape a sharpie to your torch it will a quick and easy check. If you see the same triangulated irregularity the problem lies in your machines motion, if it draws perfectly round the problem will be with the plasma arc "wandering" and we can try some things once that is determined.

[Deezl Smoke]

Have you tried the pen holder idea mentioned above? If you can securely hose clamp or tape a sharpie to your torch it will a quick and easy check. If you see the same triangulated irregularity the problem lies in your machines motion, if it draws perfectly round the problem will be with the plasma arc "wandering" and we can try some things once that is determined.

I'll attempt that asap. I should have a bit of down time today. I imagine I should find something that is perfectly round to start with, and write a program for that diameter so I have something to gauge the hole condition since I can't grind the pen mark away to reveal that condition. I know I have a dimension issue somewhere as I always have to ad about .050" to the diameter in any material thickness to get the hole size needed. But I would think that must be a software setting somewhere,....maybe.

[weldguy]

The out of shape hole is pretty obvious in your above pics so it should be immediately clear once you draw a circle with a Sharpie if it looks the same as above pics or not. Maybe the .050" difference your talking about is the kerf width but that can be dealt with later. Post pics of your Sharpie test.

[Deezl Smoke]

Did'nt make it today. One bad thing about people liking the work one does, is even when you don't want to do a job for them, they insist. So.....I'll try again tomorrow.
But I am not the author of this thread. The author posted the out of round pics. My .050" is software I'd bet. Just don't yet know where or which program is it is.