Circle problem

[Orangejbird]

Any ideas?

Belts are tight, rails/gears/gear tracks clean. Gears on motor shafts tight. DynaCNC/Mach 3/sheetcam/Cutmaster52.
9 ga mild steel. 40Amp 100 ipm.
Each circle was was cut in the opposite direction so you can see the jog change sides in each.

We run without the torch on at 5 ipm and can't see any visible play.

[Bigrhamr]

It's very likely mechanical, backlash or slop on one axis. Keep looking for any possible source. Are all of the gears or pullies keyed to their shafts? Flat spots with set screws? No flat spots with set screws? Sometimes with a flat spot on the shaft if the set screw isn't centered on the flat it can feel tight but still move slightly under load. If no flat spot it may have moved enough over time to round off the set screw and wear a path in the shaft. You can drill for an extra set screw 90 degrees off of the first one. Paint a line of something like red nail polish on the end of the shafts and pulleys, that makes it easier to see if it has moved since the polish will crack. Do you have gear boxes? Also check the couplers between box and motor.

[acourtjester]

It seems like a problem when you transition from both X & Y stepping together to only one stepping. since it seems to have bump opposite each other. Also the circles are not round so the calibration (steps per) may be off.
I would tape a pen to the torch and draw on paper until you find the problem you could waste metal trying to find out what is causing it. You state the circles were cut in different directions that may be why the bumps don't line up

[chasxjs]

It definitely appears to be an issue with play in the drive system.
Try energizing the stepper motors and then try to move each axis back and forth.
It should lock solid with no noticeable play.
I would guess that your issue is in whichever axis is top to bottom in your picture.

[jimcolt]

Replace the torch with a pen and trace the same part at the same speed. If the problem is still there....then you need to look at machine mechanics. If the pen tracing looks good.....put the torch back in an do a cut, then rotate the torch 90 degrees.....do the cut anomalies go with the torch? Then it will be a torch or consumable related issue. If the anomalies do not rotate with the torch....do the same cut but with height control of. Set the torch at the exact right height with feller gauges. Height control that makes a move partway through a circle will dramatically alter the shape.

Jim Colt Hypertherm

[Orangejbird]

WE FOUND IT!

The sprocket on the Y-axis motor was loose. Tightened with allen wrench and circles work great!

Thanks for all the advice!