I’ll try my best, and others will be able to help too. Here’s a quick summary though:
- If all your squares are the wrong size in X and/or Y, you either have lost steps or you need to calibrate the axis. If they’re all off by the same percentage, it’s probably a calibration issue.
- If your depths are off by a small amount, you probably just need to calibrate the Z axis.
- If your circles are somewhat oval, that indicates you’re losing steps. The way to figure out which axis is losing steps is to compare the direction it was cutting (clockwise or counterclockwise) to the long axis of the oval. For example, if it was cutting clockwise and the longest measurements are at the 1 and 7 o’clock positions, that says you lost steps on your Y axis (because it traveled too far on the X before the Y started to move).
I’ve got a video explaining how I calibrate my machine in this thread: X-Carve Maintenance/Troubleshooting Videos - Add Your Own!
There is a great explanation and procedure for fixing lost steps in this thread: [Guide] Offset cutting, Lost steps, Positioning errors, etc