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?
Best Answer by hyiger:
👍I'll try loosening both adjusters fully, then following the Quick gantry alignment guide as suggested and report back. Thanks!
If needed, don't be afraid to bend the gantry by hand. Also, as you are tensioning the belts, keep an eye on the gantry and make sure it's not getting skewed as you are turning the screws. I use a Wera 2.5mm hex driver and I've marked the handle with 1/8 gradations.
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.
RE:
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.
I don't think that is what happened. In my experience, the belt tuning wizard always has you measure both belts first, then gives adjustment instructions for both tensioners. It makes sure that you always tension both belts by equal amounts.
If the wizard is presented with a setup where the tension of the two belts is too widely different, it concludes that your belt & gantry system is out of whack and directs you to re-squaring the gantry. You have used strongly asymmetrical tensioning of the belts to force your gantry into alignment -- without the belt tension, it is probably skewed.
Please follow the suggestion from the belt tuning wizard and @hyiger, and square your gantry first. It's the Quick gantry alignment procedure (yellow box) on the page hyiger linked to. Then, when roughly tensioning the belts again to get them into the working range of the wizard, make sure to always tighten both tensioners symmetrically.
RE: Firmware belt tension wizard fails on lower belt
Thanks guys. Yes, I was careful to always tighten/loosen both belts symmetrically and by the same amount (I even used a protractor!). BUT! You both pointed out an imbalance and that made me think: What if it they were tightened asymmetrically from the factory!
👍I'll try loosening both adjusters fully, then following the Quick gantry alignment guide as suggested and report back. Thanks!
RE:
👍I'll try loosening both adjusters fully, then following the Quick gantry alignment guide as suggested and report back. Thanks!
If needed, don't be afraid to bend the gantry by hand. Also, as you are tensioning the belts, keep an eye on the gantry and make sure it's not getting skewed as you are turning the screws. I use a Wera 2.5mm hex driver and I've marked the handle with 1/8 gradations.
RE: Firmware belt tension wizard fails on lower belt
👍I'll try loosening both adjusters fully, then following the Quick gantry alignment guide as suggested and report back. Thanks!
If needed, don't be afraid to bend the gantry by hand. Also, as you are tensioning the belts, keep an eye on the gantry and make sure it's not getting skewed as you are turning the screws. I use a Wera 2.5mm hex driver and I've marked the handle with 1/8 gradations.
After loosening both screws, getting the belt all floppy-floppy, indeed the left side of the gantry was substantially off, perhaps 5-10mm. I tried gently man-handling it back into shape but that didn't work 😑 So I upped the effort to medium man-handling, and it only made perhaps a very small difference 😥 Finally, heavy man-handling seemed to do the trick. Millimeter by millimeter the left side came into square after maybe 3 or 4 tries. I was astonished by how much force this took, but happy I didn't break anything.
Then as suggested, I used my phone app while symmetrically tightening the tensioner screws until I got the bottom belt making an acceptable pitch. Oddly the top belt was extremely far off, beyond the app's measurement range 🤐 I think maybe when I was initially tightening the screws, I was missing the threads on the tensioner 🙄 So I put a finger on it until the screw popped out, and gave it a few turns individually until the belt tension "felt" roughly the same as the lower one.
Worried I un-squared the gantry, I moved the head to all 4 corners, then re-checked square (with the head in the middle). It was still dead-nuts on perfect. So I went back into the app, and got the upper belt in "tune" (turning both screws symmetrically again). Re-checked the bottom belt, and it was still acceptable.
Back in the calibration wizard, I followed the steps, and it reported 97Hz top / 96Hz bottom "No adjustment necessary" 😎
Thanks guys, I really appreciate the help, wouldn't have figured this out on my own 😀
RE: Firmware belt tension wizard fails on lower belt
Back in the calibration wizard, I followed the steps, and it reported 97Hz top / 96Hz bottom "No adjustment necessary" 😎
Thanks guys, I really appreciate the help, wouldn't have figured this out on my own 😀
Yep, that seems like a good result to me. What I did was wedged the universal wrench on the opposite side I was bending then just bent it until square. I didn't have to go caveman on it to get it to bend.
Anyway, this seems to be tripping up a lot of kit builders I would say.
RE: Firmware belt tension wizard fails on lower belt
Back in the calibration wizard, I followed the steps, and it reported 97Hz top / 96Hz bottom "No adjustment necessary" 😎
Thanks guys, I really appreciate the help, wouldn't have figured this out on my own 😀
Yep, that seems like a good result to me. What I did was wedged the universal wrench on the opposite side I was bending then just bent it until square. I didn't have to go caveman on it to get it to bend.
Anyway, this seems to be tripping up a lot of kit builders I would say.
Mine was an assembled unit, but yes I believe it would confuse builders even more. To be clear, I didn't need to go caveman, it just required a lot more force than I expected it would. Anyway, thanks again for your help.