3D Printer Calibration

Dear all! I’m new to the MPCNC world and I’m planning to build my own machine!
I already have a small CNC, a Proxxon MF70 converted to CNC and an Anycubic i3 Mega as 3D printer.
I was checking some prints and I’ve found that my printer prints in square but a little under dimensions.
Checking the diagonal of a 50x80mm piece (which should be 94,34mm) I’ve measured 93,34mm, but both the diagonal are the same value. Also the holes are a little small.
What can I check on the printer before I start printing the MPCNC parts? I was thinking about loosen the belts a bit.
What do you think? Any advice will be appreciated!
Thank you very much!
Best regads


If everything is square on the print you can compensate for the under dimension by scaling the stl up slightly in your slicer. Test a few until you get the dimensions you want. It sounds like you may only need a very tiny upscale.

I made an lr2 myself so others could chime in for critical fit items on the mpcnc.

Have you checked that 100 mm command results in 100 mm of movement?

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Are the other dimensions 50x80mm? 0.9mm is a lot, but under extrusion or a hard to measure corner may be adding to the error.

Thanks all for the aswers!
the others dimensions are 49,8x79,6mm so a little small, now I have to check the 100mm travel and adjust the step/mm…

Also make sure that the mechanical system doesn’t have any “slop” in it. Check things like the grub screws that hold pulleys to motor shafts, etc.

If the mechanical and steps per mm check out all right, the next thing to look into is the universe of variables that govern the amount of plastic being extruded. Once the current mechanical checks are completed I can provide a pointer to a process for fine tuning E steps per mm, temperature, and extrusion multiplier settings.

Thank you for your reply! I’ve tensioned the X belt and now I’m doing some check with a centesimal comparator. I’ve now set the X step/mm to 80.50 and I have error of +/- 1 cent. Now if I run the X axis of 10mm I have 10mm movement.
I only have to do the same with Y axis…
Can you please tell me the process for fine tuning?
Thank you very much!

Working through the process described here should get you dialed in very well.

Thank you very much! I think I’ve tuned the 3D printer in the right way :smiley:
Now I’m doing some other prints just to test the accuracy of the machine. Then I can start with the MPCNC parts :wink:

Best of luck!

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