Those are some good suggestions from Eric (BalsaMan).
If you're not losing steps, there are a couple of other things that you could check, too.
First is to verify that your configuration is, in fact, correct...I know you said it was correct, but it never hurts to go back and verify it, again. Over a few hundred, or a few thousand steps, errors will be cumulative. Check to make sure your config is as perfect as you can make it.
Second is backlash. This is an error that depends on the fit of *each* screw/nut pair, individually. It's possible that there is greater backlash in the X axis than in the Y axis...this would account for a slightly flattened circle, too. It rears its ugly head, whenever you change directions.
-- Chuck Knight |