Firmware belt tension wizard fails on lower belt
I have the pre-assembled Core One+ with 6.4.0 firmware, turned it on and it passed all the built-in tests. First prints look really good, but there was some minor ghosting on the corners and relief-letters of my test cube. So I ran the built-in belt tension wizard, which found the upper-belt was way off and the lower belt was extremely unacceptable.
In other words, when I got tuned the freq. so the belts were doing a big, slow, consistent wobble with sharp-peaks, it presented screw-adjustments for the upper belt, but kicked me out with a failure message on the lower belt, directing me to re-square the gantry. But I think the gantry is basically square? My only skepticism here is on the left side, I can make it move perhaps 1/8 - 1/4 mm by pulling "fairly" hard on it (perhaps 1-2kg of force). I'm not sure if that means it's got a hair's misalignment or if I'm pulling so hard as to flex the joints 😜
So I turned to the Prusa app on my (Android) phone, and plucking the belts as documented. After 4-5 incremental screw-turnings, I got the top belt settled at around 100 Hz and the bottom at around 90 Hz. I monkeyed with it a little more, but ended up going back, as 100/90 was the best I could do, leaving the bottom belt slightly out of spec.
Out of curiosity I tried running the built-in tensioning wizard again, but again it failed with the same reason: Top belt is perfect, but bottom belt outside acceptable range. I'm uncomfortable with the plucking-based tuning and would like the built-in tensioning wizard to be happy. What should I do or check next?
RE: Firmware belt tension wizard fails on lower belt
When you turned the tensioning screws, did you always turn both by the same amount and in the same direction? If you turn them asymmetrically then you could possibly bend the gantry which will cause problems. I would start by completely loosening the belts and run through the quick gantry alignment guide: Adjusting belt tension When tightening the belts, always alternate between the screws turning both in the same direction by the same amount.