I’ve searched high an low but have come up empty handed in my search for any information regarding how to calibrate the Mbot cube so that the prints come out to the correct size. I printed the 20m x 20mm x 20mm cube and the dims came out at Z 20.37mm, Y 19.86mm, X 19.96mm measured with reasonable quality digital calipers. Machine specs are the 17 tooth Mbot cube kit with original acrylic/ fiberglass build plate printing with PLA
(solution) In Mprint version 184.108.40.206 the print size calibration is under the tool tab and provides instructions on how to calibrate it, I guess I just missed it.
There is also on the control panel, in control|motion where you can set steps/mm.
I found that mine was pretty much dead on at build time, but you can adjust it. (I believe that mine was set to 88.9 for both X and Y)
Take the design size (20mm), divide by actual print size (say 19.86mm) and then multiply the result by the current steps/mm to get the new steps/mm.
I would say that you should be careful of changing the Z axis, since errors in the Z offset will translate directly to the printed object, and the 400 steps/mm default is mathematically correct for the Z leadscrew. It is highly unlikely that the Z steps/mm should ever be adjusted. It is possible that the X and Y steps are slightly wrong, but I would also see if you get a consistent ratio of error for larger sizes.