Circles not round after upgrade

Hey all. I haven’t posted a bunch as I’ve been enjoying working with my X-Carve for the last three years! But this year, I decided to expand the machine’s size from 500x500mm to 750x1000mm. The rebuild took a couple of months, but I’m quite pleased with the result. I spent a lot of time squaring and tramming the machine and have been happy with the parts I’ve cut except it doesn’t seem to cut circles as well as it did previously. As they get to around 1" in diameter, they start getting oblong between 11 o’clock and 5 o’clock by about 10/1000ths. I’m assuming this means my machine isn’t quite square, but I wanted to ask and see if there might be another explanation. I’ve checked the machine for backlash (none that I can see) and made sure the belts are similarly tight, and I’ve tried adjusting the steps per mm without much change. Anyone have any advice?


  • Machine isnt square (like you mentioned)
  • Fine step/mm difference between the X and Y axis
  • Different backlash component between X and Y axis
  • Different rigidity (or “give”) between X and Y axis
  • Different wheel friction / belt tension between X and Y axis

You mention its oblong at around 10/5 o´clock which seem to indicate that its the transition from Y-direction to X-direction that trigger this. I have higlighted my primary suspect.

What about bit deflection based on the wood grain direction?

Good point!
Quick and easy to test by reorienting the material 90deg and carve.

Great suggestions. I should have mentioned these cuts are in plastic not wood, although I see similar out of round issues in wood as well.

I’ve had some success by adjusting the belt tension and the V-wheels on the x-axis. The Y belts were much looser than the x, but the X wheels were much tighter. Circles are more round…

I’m also now investigating the steps/mm numbers as I’ve noticed that test square cuts are longer on the X-axis by a few thoutsanths.

Thanks all for your help!!