Belt tensioning issues - firmware tensioning guide and website tensioning "app"
Hello,
I have a prusa core one built from kit.
I've never really managed to get exactly the tension in the belts suggested by prusa. I want to ask a few clarifying questions before i sink a few more hours in it tonight.
The current status of my belts is that, according to the website tuning app my top belt is at 99 Hz and my lower belt is at 90 Hz. The website app is satisfied with that ("just right"), this comes after fiddling with it for 3 hours last night, completely detaching the tensioners by mistake and so on.
Before doing this adjustment, I was at the exact same values - i.e. I only managed to do the best I managed to do when originally assembling the printer; I've always tried to get exactly where prusa says I should be (max 98 hz on the top belt and not more than 8hz difference between the belts) but I cannot get closer than 9Hz between the belts ; also my left tensioner is much tighter than my right one, if that matters.
Now that we have official firmware 6.4.0, I tried the manual belt tuning option in the firmware. It's hard for me to understand what exactly the firmware tuner wants from me or deduce from the GIFs on prusa's website how the belts should move but logic (it's very possible I am wrong, I am wrong all the time) tells me that in the tuner I should adjust the frequency until:
1. I get the belts to do a slow back and forth, one at a time
2. the correct value for the frequency I should stop at is the one where the belt has the highest amplitude or highest range of movement.
Is that correct?
If I do this, the frequencies where I get the largest amplitude in movement for the belt are about 2 Hz above what the web app tells me. At that point the tuner in the firmware cannot help me and tells me to go square the gantry or something ; my gantry is squared so maybe the only thing to do is take everything apart and make sure again I have the proper amount of teeth pulled in through the bracket behind the nextruder.
ALTERNATIVELY I can just leave it like it is and move one with my life.
Are people out there printing with slightly out of range frequencies in their belts?
Thank you
RE:
Your understanding of what to look for during the stroboscopic adjustment (your steps 1 & 2) is correct. In case you have not found it already, here is Prusa's support page describing the process. (And also describing gantry alignment and belt re-attachment if it should ever be needed.)
The overall logic is that the gantry should first be squared without any pull from the belts. Then the belts get tensioned symmetrically. So the belts must not be used to force an otherwise skewed gantry into alignment.
It seems that the belt adjustment wizard "gives up" when it detects that the two belt tensions differ too much from each other. It then concludes that you must have used unequal belt tension to force the gantry into alignment, hence suggests that you should start over with the "Quick Gantry Alignment" as described in the yellow box on the support page above.
In your case, the deviation from the ideal belt resonance frequencies is pretty small. If you experience reliable homing of the tool head (without excessive "head banging"), I would probably leave things as they are for now -- unless you are curious and just want to walk through the whole process outlined on the support page.
RE: Belt tensioning issues - firmware tensioning guide and website tensioning "app"
Thank you Jürgen, helpful as always.
That's good to know.
RE: Belt tensioning issues - firmware tensioning guide and website tensioning "app"
To add, it's seems to be a (the most) common issue for people to try to force the belts to be 98/92hz. I did this at first and it caused all sorts of issues by skewing the gantry followed by failing Y calibration, layer shifts and homing problems.