Core One Y-Axis Calibration suddenly fails
I've been using my Core One for about 5 months now. It has not given me any issues. After the 6.4 firmware update, I had my printer recalibrate. For some reason, the printer never passes the y calibration test. As best as I can tell when I watch the positioning, it seems to think it only gets to Y=219.6. However, if I go into control and adjust the y-axis manually, it will move to 221.
I went back to the previous firmware, and I am still having the Y-axis calibration failure. I did once get it to pass, but I can't remember how I did it. I want to say it was after I loosened the tension on the belts, as I have read others doing.
My belts, at the moment are tuned 98MHz top belt, 92 MHz bottom belt. The past two weeks I've been plagued with headaches with my Core One, and this is just yet another. I really don't want to spend all my time troubleshooting a 3D printer. I've had 5 great months, but not so fortunate now.
RE:
You need to be very careful how you tune the belts. The left and right screws tension both belts and both screws must always be turned in the same direction by the same amount. Never turn the screws independently of each other for any reason. If you are turning just one screw to make adjustments it will (most likely) bend the gantry and you will fail the Y calibration and perhaps homing could fail as well. If you are turning the screws to get exact 98/92hz tension, you will bend the gantry for sure. As long as both belts are in the 90's and the upper belt has a higher frequency than the lower belt and the gantry is still square then you fine. If the lower belt has a higher frequency than the upper belt then loosen the belts and try again. With it completely loose, start with left 2 turns, right 2 turns, left, right etc until the belts are starting to get tight. Then left 1 turn, right 1 turn. Always both screws and always the same amount of rotation.
Start by following this guide and make sure the gantry is as square as you can make it (bending it by hand if necessary) before tightening the screws. Follow the process in the "Quick Gantry Alignment" section.