Second layer issue

Hi everyone! I build my MPCNC a few months ago and it was working perfectly.
But one day it started to fail when milling. The thing is that when it starts milling, the first layer is nice, but the rest of them has a offset of almost 1 cm.
I have tried to re-flash the firmware, but it doesn’t work… I think that the error is in the communication between X and Y axis, because it cuts s square nice, but a circle doesn’t.

Thank you very much!

Just curious, was everything drawn with the same CAD program?

Yes, I tried with and old file that had worked perfectly before.

An old file from the same program? I ask because some programs seem to draw arcs/circles differently than others.

Same program and same file

I wish I could help, that the first cut is fine and the rest offset doesn’t ring any bells with me.

Well, thank you anyway!

I would check the grub screws holding the pulleys to the motor shaft.

Also, is your bit dull?

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You were right! I just had to tighten that screw.

Thanks!!!

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Consider adding some temporary thread locker (e.g. blue locktite) to the grub screws so they don’t continue to work themselves loose. The “blue” formulation doesn’t require heat to break loose but will prevent vibrations from backing the screw out again.