Hi (and sorry for my english),
it’s easy to have a perfectly squared frame, it’s not so easy to have a perfect squared gantry and even with that, there is some play between 2 X motors or 2 Y motors: you can move a little the MPCNC by hand. Ryan say to triple check distance between the steppers and one corner before starting to work. But it’s time consuming and sometimes not so easy to move around your MPCNC.
I just use a pen to loose time once, now it’s fast and easy to check the squarness:
1-use a straight edge or something flat to mark all rollers at the exact same distance from a corner (I use my corner ‘origin’ = front-left). Choose something to be around the middle of your working area if you can. (picture 1 )
2-move each axis +10mm then -10mm, to enable steppers. If you are not exactly at the marks, turn with force the pulley of the steppers to be at the exact position.
3-use your pen to mark each 10mm (for me 10mm it’s enough). Don’t wait too much between 2 marks to avoid the automatic disabled steppers (or change the value of 60s I think, in Marlin). (picture 2)
Now each time you start a new project, put your rollers at the place you want, move again +10mm then -10mm on X and Y axis, and if needed, adjust your rollers with force.
