Circle problems

Hey Guys,

Im new here. I’ve had the MPCNC for a couple months and it has been working great.

Today, I’ve had a file that I have encountered a problem with. When cutting circles they are not concentric for me, at first I thought maybe since the circle was so big I was hitting the size limit of my machine and maybe it bumped the edge. (24"X24").

I did some tests on foam and the smaller I made the circle the worst it became. Also the holes were misaligned on every file.

I’m using Vcarve with the post processor linked on this site, with a 1/8 inch end mill. I’ve tried Estlcam also but got the same results. I don’t know if the problem is my machine or my Gcode. Other things cut out great for me.

I checked the machine for square and it seemed to be good. I also did a 400mm test cut and it was maybe 1/16th an inch short on the Xaxis and perfect on the Y

I hope I am attaching all the pictures needed here. If you need any more please let me know.




Iris1Pass.gcode (65.6 KB)

Ypur gcode is fine. It looks like you have something that resembles backlash in the x direction but it’s inconsistent. Sometimes its there and other times not. The most telling example is your smallest circle. The outer circle halves are shifted and the loop doesn’t close. But then other cuts appear to be fine, with no backlash at all.

Are you running dual endstops? Maybe one motor driver is overheating and shutting down sometimes, but not always? Thats all i can think of right now.


Thank you Jamie,

Appreciate you taking the time to verify the Gcode for me.

I don’t have any endstops. I will check the motors, and tonight I am going to make sure nothing came loose anywhere.
I’m not sure what else to do right now.

Check the set screws om your pulleys. Maybe it’s loose but staying on the flat part.


Thanks for the reply Jeff,

I wouldn’t have thought to check that but it looks like the pulley in the back has lost both its set screws. I am going to order new ones now

and hopefully that fixes the issue.