Ran the 500mm X movement test again, same issue. 497mm.
500mm move left then 500 move back right returned it right to the same spot, so maybe step loss isnt the issue here. I’ll check the bearings.
Removed the X belt and the core slides pretty freely along the X axis.
When you home the location is set at 3mm. When you ask to move to x=500 it moves 497mm.
The location is set to 3mm just in case you want to use some of the space wasted by triggering the endstops. On most machines you have 4-5mm I used 3mm to be safe.
This is relative vs absolute positioning.
From your current location you can issue a g92 X0, then a G0 X500, to move 500mm
I wasn’t running the test from home. I homed the machine, moved it about 100mm to the right of home, made a mark then moved it 500mm right X and made another mark.
Its interesting that its 3mm out, however I thought as I wasn’t running the test from the home position it wouldn’t affect that.
3mm is a lot. We are all assuming something is mechanically wrong. The most common, by far, 1000x over is …
Loose grub screws.
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its 3mm off on the X and also the Y.
Which grub screws? How should I best check them?
3mm off over 500mm is a lot.
we freaked out over 1.75mm over 1220mm, belt error.
All your pulleys. Use an allen key and make sure the set/grub screw is tight and seated on the flat of the D notch on your steppers.
Youre spot on. One of the grub screws on the Y axis is missing! The ones on the X axis werent fully tight. I’ll have to pull this thing apart to access the Y axis screw holes I think
Replacing the missing grub screw and tightening them all up “seems” to have fixed it. I’ll do a test cut and see.
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It just cut a 100mm x 100mm part perfectly. 18mm MDF, the edges are all neat on all sides.
Fingers crossed the issue appears resolved! Thanks Ryan and everyone else.
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Did you locktite these? If not, you’ll be repeating this exercise soon enough.
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Is that recommended? Just ordered some Blue locktite from amazon.
Excuse my ignorance but to apply it I assume I just remove the set screws, apply a small amount of locktite to the thread and screw them back in and leave it to dry?
Yes, but use purple not blue.
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Whatever you do… absolutely DO NOT use red lol
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Help I’m color blind what properties do i want
Property… correct strength for the fastener (primarily fastener diameter unless the number of engaged threads are many) according to the manufacturer.
Henkel specifies purple Loctite 222 for diameters under 1/4". Permatex has a similar product.
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Just to share my process. Loosen both grub screws, put loctite on the one that will seat on the flat area. Tighten. Then, once you’re convinced that one is tight and seated properly on the flat, then loctite and tighten the second screw. Others may have better methods.
The tube should say purple (or blue) on it. It should NOT say red…
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Yeah, solved by Dreyfus in post 1, not Ryan! Boo! 
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