Help with my belts
I experienced layer shift on a 20 hour print (annoying). I remembered the first thing people recommend is checking belt tension. Using the strobe tensioning tool in the firmware, I found the instructions fairly vague and subjective about the strobe induced “waveform” created. Until I found this video on Fakebook: https://www.facebook.com/share/r/14ZV1BXjaG7/
It said essentially you want the largest amplitude wave possible.
Is that accurate? Because to get that I had to go to a frequency well over 100 and subsequently loosen my tension adjusters by nearly 1/2 a turn. I haven’t printed yet, and I did double check the app recommended setting three times and It remained constant. Note this was a factory assembled unit, and the gantry aligned perfectly before the test. The final frequencies (after the adjustments) were 94.5 and 92.
So the question is, using the strobe, you want the largest, regular interval and amplitude “flap” of the belt possible when setting the frequency?
Thanks.
RE:
You want to pick the resonant frequency, where the amplitude is highest. When my core One was new, frequency kept going down over the first couple of weeks, probably belts stretching. So it may be that the factory-assembled printer is tuned with that in mind. If you print at higher chamber temperature, don't set resonance frequency at the top of the range as heating up belts will tighten them further.
What you see in the strobe light varies case by case, depending how close knob resolution gets you to the physical resonant frequency. If they match very accurately (say, 0.02 Hz - one cycle every 50 seconds) - the belt will look like it's standing still, just not straight. It will also take a few seconds to settle into a steady state. You can dampen it with a finger to start each frequency from a blank slate.
Is there any evidence that overly tight belts cause layer slip? I'm not aware of such reports. It may add some extra friction but it would need quite a bit to overload the "torque budget" of the motors, especially if not maxing out acceleration (I've experimented with "unreasonably" high printing speeds, it causes a headache watching the printer but it never skipped steps)
Instead, I'd look for other failure modes.
- There is one software bug "avoid crossing perimeters". Do not enable this option (off by default), it is reported to cause issues.
- Loss of adhesion and warping is the most common root cause, the nozzle crashes into the print
- Overhangs curling up is another common one
- Overextrusion can cause the nozzle to get stuck in excess material.
- The wipe tower brings another few potential issues but you probably were not using that feature.
RE: Help with my belts
What you see in the strobe light varies case by case, depending how close knob resolution gets you to the physical resonant frequency. If they match very accurately (say, 0.02 Hz - one cycle every 50 seconds) - the belt will look like it's standing still, just not straight. It will also take a few seconds to settle into a steady state. You can dampen it with a finger to start each frequency from a blank slate.
This part does not apply to the stroboscopic belt tuner as implemented by Prusa. As you change the belt excitation frequency in the "manual belt tuning" wizard, it will also change the frequency of the flashing LEDs in sync, always keeping a frequency difference of approx. 2 Hz. So you will always see a slowly oscillating belt (moving at that beat frequency of 2 Hz or so), and you are indeed looking for the maximum amplitude of the oscillation.
RE: Help with my belts
Thanks for the reply. I think I currently have it set correctly based on the video and your confirmation. So there’s that at least. I’ll look into your setting recommendation as well. It was a new filament (Polymakers polylite’s new PETG formula) and it did recommend slower print speeds as well as fan speeds, which I wasn’t quite sure why a standard PETG would need so. I may fall back to my default filment (overture or hatchbox) and try again with the standard profiles.
RE: Help with my belts
For something as important as this, I wish Prusa would post a real video showing the complete tuning process, not just this hacked together help page with a tiny gif.
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: Help with my belts
This video shows the moving belt and what to aim for. The relevant part begins at 2:40:
RE: Help with my belts
Good video. I actually like the second method (setting the target freq and adjust to it) vs. the “factory” method. I’ll see how mine looks later. Thanks.
RE: Help with my belts
Thanks for the comment. You're correct (I think, printer's busy so I can't confirm but it makes sense).
RE: Help with my belts
There are a few videos like this on YouTube—why Prusa can't to that themselves is beyond me. In fact, the overall quality of documentation seems to go down south. The Core to Core + upgrade is another example. Looks nothing like any of the other upgrade manual. Probably done by a high school student as a summer project 🙂
Formerly known on this forum as @fuchsr -- https://foxrun3d.com/
RE: Help with my belts
They needed the resources to burn the instruction manual for the Signature Core One onto solid oak panels. That takes time.