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Prusa Compact MMU2 Spool Holder

by jgillick Apr 13, 2019
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How well does it work with TPU, Ninja flex or anything else that might rub against itself? Does that cause to much friction when the printer is pulling it?

Second question. Does TPU or other soft filaments get tangled up anyway? Or do they create the slack loops as well?

Softer filaments work, but not quite as well. For those filaments, sometimes I just don't wrap it around the wheel.

Thanks for this clever and compact design! Works very reliable so far, more so since I increased thickness of the wheel a bit for a tight fit to avoid filament getting caught between wheel sidewalls and guide.

I really want to like this. Any advice to keep the filament from crossing over on itself. I'm not even doing tool changes. Just printing 1 color prints keep failing because the filament wraps over itself in a knot and the extruder cannot pull it anymore. This is still so much better than the MK3s buffer but I just can't get it to work reliably without the filament crossing over itself. Do I have to use two wraps around the wheel or will this work with one? Thanks

I know you gave up on it but it sounds to me like your Tubes are curving sideways. aka bending left or right before they get to the MMU. That will cause the filament to spin and twist in the tube. Then when it goes slack it will twist up and get tangled on its self. It is best practice to keep the tube pointed in straight lines from the spool to the MMU. looping inline is okay. But the more you stray from one side to another the more problems you will have.

That sounds frustrating. Can you post a picture of what’s happening? I can’t say that I’ve experienced this with either single color prints or multi color. The filament might be wrapping over itself on the second wrap around the wheel when you’re loading it. Make sure on the second wrap, it’s wrapping towards the outside (opposite the spool). Also, a single wrap should be fine. Let me know if any of this helps.

Hi thanks for the reply, Sorry I didn't think to take any pictures. I have had too much other frustration with my MMU2 in general (Nothing to do with this filament holder) so I've disconnected it for now.

I had some issues with the filament not going back onto the wheel correctly and getting caught between the guide and the wheel.. See attached. Happens pretty much every time I put slack into the filament guide.

When loading the filament, as it comes from the filament spool, does it first go under the big wheel or over the big wheel, before going to the filament tube? I've not had it jam on that side of the wheel. It used to jam on the other side, so I changed the model to prevent that. Let me see if there's anything I can do with that side. Can you take a picture of the other side so I can see how the filament is going into that area?

Nice design. Glad to see people are finding good uses for all the leftover fidget spinner bearings. lol

Can you post a video of this in action please?

I'll try to pull one together. Until then, it's pretty much the same as this one: https://www.youtube.com/watch?v=XdYJgfy7VZ8

I like this design. It looks much simpler. Nice rework. I was thinking of taking it a step further with simplicity (maybe) and less print time and material.
I am staring at the holders/trays that came with the MMU2 thinking the tall spool part could be attached to the Prusa trays, then you don't need any of the roller parts. I was looking at how they had the clips that just snapped over the sides.
Is that something you would consider looking at as a modification?
At this point I would drill 2 holes through the side to mount it because that is the only way those trays are getting used. :)
I am a Fusion novice and messing with .stl in there is a pain.
Again, nice job.

That's a pretty good idea. I just uploaded the Fusion 360 file, if you wanted to give it a try. (it loads with the spool holder on its side, so everything is oriented well for Slic3r).

I personally don't like the trays because they make an annoying squeaking noise when the filament is rolling.

That said, I did consider making it so that the rods used in the trays could be used instead of the wheels. Maybe I'll revisit that idea. Then you'd be able to avoid printing the 4 wheels.

I may just have to go with your design. Printed one out. It looks so nice. :) Now for some testing. That slide adjustment is very well done.
I may mess with the Fusion file and tray for a challenge. Thanks for sharing.