I have been dealing with a drifting issue on my machine. Every once and a while my right had motor for the y position begins to rattle, then my entire bridge gets out of whack. This causes the y axis to drift, either up or down my cutting surface. It moves it so far out of its original path that it messes the entire piece up. sometimes I get lucky and catch it before it can do any real damage but about 50 percent of the time i end up having to start the project over completely. Do i need to buy a new motor and replace it? i have tightened and retightened my bands over and over again with the same result. please let me know what you think.
Check all the wiring and connectors — is everything secure and in good condition and positioned so that it will not shift as the machine moves?
Check the pulleys on the Y-axis motors — are they secure with both pulley set screws in place? Put a witness mark across the ends of the pulleys and motor shafts.
Power down and remove both Y-axis belts and put a bit of tape on the pulleys so as to more easily see their rotation, then power up, connect and try initializing — Z-axis should initialize normally, then the machine should try to move X- and Y-axes — the X-axis also should initialize normally while the Y-axis motors should turn until CM times out. Do they turn evenly and in synch? If they do, reinstall the belts, swapping them end-for-end and side-for-side.