The beginning of the filament is stringy at MMU change.
I have an issue with my MMU2s who is doing strange.
It always gets stuck because the tip of the filament doesn't stay nice and straight anymore. Some pictures clarify this.
It always gets stuck because the tip of the filament doesn't stay nice and straight anymore. Some pictures clarify this. I want to add that I am printing with PETG here and it is in all colors. My filament is dry and not moist. The MMU is almost impossible to use this way because it jams between every filament change.
I read already this topic, but no luck
https://help.prusa3d.com/article/stringing-and-oozing_1805
RE: The beginning of the filament is stringy at MMU change.
Hello,
I had this same issue too, but have solved it.
There are two things i would recommend to try, the first being to change some of the settings in prusaslicer. Try changing the temperature around, and also try adjusting the cooling moves. Also, remember that these settings differ in brands of filament. I have only found the stock settings to work perfectly with prusament. Here is an article with more information about this. https://help.prusa3d.com/article/mmu2s-setup-and-inspection_2233 Just scroll down a bit.
The second thing I would do, which might help this problem, but definitely solve many future ones is to update to the mmu3 firmware. It works WAY better. It also tells you what's wrong if it goes wrong. FIRMWARE 3.13.1 (3.0.0) https://help.prusa3d.com/downloads/mmu2/firmware
Hopefully, this helped!
-Lucas Jaeger
RE:
Yes, filaments need to be dialed in, precisely for that, to prevent stringy tips. Some brands are easier to get stringless than others. If you struggle, start with Prusament filaments, get them dialed in nicely and once you managed to do that, you can try other brands. I would stay with a number of brands that you are confident with and also stay with brands with consistent quality (don't cheap out on filament when using the MMU).
A good starting point is printing temperature. For the MMU you usually want to be at the very low end that still gives you good printing results. Increase cooling moves, but if that is not sufficient, google for alternative ramping settings. There are some non-stock settings which are handling stringiness better.
Also, before printing something big, test your filament and settings with for example calibration cubes. Ideally a print with very frequent filament changes so that you can test a few hundred changes as fast as possible. Stringiness is a problem that only phases in slowly, so it is a good idea to have those test prints before a longer job to see if things stay nice beyond the very beginning.
Just as a heads up. It is possible to print PETG with the MMU without stringing issues.
Mk3s MMU2s, Voron 0.1, Voron 2.4