X-Controller/X-Carve positional repeatability?

I received my X-Controller .last week and assembled it, this weekend I attempted to calibrate the steps/mm for X and Y. In the process of doing this I’d move the head to a point on a tape measure, then instruct the machine to move X +600mm and notice the offset of about 1mm. Then I’d instruct the machine to move X-600mm, but found that it missed the original location by about 1mm. Now I’d expect that even if the steps/mm was off, moving a given amount and then the same amount back would return it to its original position, so something else must be going on here. I didn’t hear any jerkiness in the machine’s motion and it seems fairly repeatable.

I don’t know for sure whether this actually has anything to do with the X-Controller or not, might have been the case before I upgraded, not sure.

Has anyone seen anything like this? What did you do about it?

Check the usual, that your belts and wheels are tensioned properly, that your pulleys’ grub screws are tight against the stepper shafts, etc. How fast were you sending the gantry? If you try slower do you still get the same discrepancy?

I don’t know about the X-Controller, but with the old Arduino+G-Shield setup a common solution was to turn the pot screw up a little for the axis where there’s a discrepancy like this. Doesn’t take much.

I’m not completely sure, it’s easy to strip the little buggers, but I think the grub screw going into the flat on the X axis motor may have come loose. I removed it, replaced it with a fresh one and blue Loctite. Will have to run some tests and see if that fixes it. Never had similar issues with my kit built 3D printer, so I just have to train myself to think of those things.