I am not sure what I am doing wrong with my MMU3 unit.
I have an MK4S that I upgraded from an MK4. I also have the MMU3 unit that I have had for a while now and have recently gotten the time to put it together. I also have an enclosure that I want to combine all of these things to make a single unit.
The printer was upgraded a few months ago and was working perfectly. Just recently got the MMU unit all assembled and setup. I do have the 'Unoriginal Prusa Drybox' from Printables attached to the top of my enclosure. This is where my filament is and it running out of the back through PTFE tubes into the buffer. I had the buffer screwed to the side of the enclosure but I took it off and sat it right behind the printer trying that way in my endless troubleshooting. Then from the buffer into the back of the MMU unit through another set of PTFE tubes. The printer is sitting just to the side of the enclosure while I am testing the MMU unit before putting the printer inside of the enclosure. All of the filaments flow as freely as they need to to the best of my knowledge.
This is where the trouble starts.
Filament loads from slot 1 but the printer clicks and makes a ton of noise. It also often gets stuck behind the selector. I will mention problems with this later on.
Filament in slot 2 is an absolute nightmare. It also clicks. It does load if I force it through manually but the gear and bearing that spin to pull the filament in, just seem to spin and wear the filament away and create weak points. There is now bits of filament stuck in the gears which have basically made the gear in this slot smooth. I would love some advice for cleaning this out so the gear works correctly.
Filament in slot 3 is iffy. If the filament doesn't jam while picking up filament from slot 1 and 2 then it may load. It looks like it struggles to pull this filament in as well similar to slot 2 but not as bad. Having to load filament manually, I get it correctly in the printer and then after I put the buffer cassette in the filament is then pulled out of the slot and is no longer up where it needs to be. Not sure why this is because there is a LOT of excess in the buffer.
Filament slots 4 and 5 are normal.
I have also notices that when retracting to the finda, a lot of times, the filament does not retract far enough so it either sticks out and gets caught behind the selector, then I get an error about the printer not being able to home. This happens often with the filament in slot 1.
I thought there was a blade that was in the selector that is supposed to help with this? However it does so about 50 percent of the time.
I also had it cut a tiny bit of filament off and then fall into the tube going down into the printer and then prevent the filament from reaching the fsensor.
This whole process has been a nightmare. Today I have considering converting this printer back to the standard MK4S and throwing the MMU3 unit in the trash.
Can someone help me out with what I am doing wrong? I followed the instructions making sure that I assembled everything correctly. I don't think I did anything wrong but I'm not sure why I can't get this thing to work like it should.
In case anyone is wondering. The filaments in slot 1 - 3 are all Jessie Silk PLA (Perhaps this is the issue with feeding correctly.) These are all partially used 1KG spools. 4 and 5 are Protopasta HTPLA 500 gram spools. (Also, perhaps why these are loading smoothly.)
Any help with this would be appreciated.
Thanks!
RE: I am not sure what I am doing wrong with my MMU3 unit.
The first thing to look at is the resistance of the filament in the PTFE tubes. Minimize the severity of bends in the tubing (think 4" radius minimum?) and as straight a path as possible. I have had translucent filament that seemed to be twice as "sticky" in the PTFE so that silk PLA might also have that problem. If you feel more than a little friction pulling the filament from the MMU "output" then it's time to re-think buffer and spool placement. I also found the Unoriginal Drybox puts a sharp initial bend in the PTFE (I'm feeding it out the back). I printed the "extended" PTFE holders that seemed to reduce the bend quite a bit and that helped.
This was my solution to try and minimize PTFE length and bends: https://www.printables.com/model/1180632-vertical-buffer-mount-for-rear-of-unoriginal-drybo
If you post a picture of your setup that might help find other potential issues.
Prusa MK4 since Jan 2024, Printables: @MikeB_1505898
RE: I am not sure what I am doing wrong with my MMU3 unit.
My end goal is to have the printer inside of the enclosure. This is obviously just testing functionality. But, I am currently printing the Auto rewind spool holders for the drybox now. I want to put those in the enclosure.
https://www.printables.com/model/702217-mmu3-mmu2s-5-spools-auto-rewinder-adapter-for-unor/files
Coming out of the back of the enclosure, through this....
https://www.printables.com/model/702362-guide-ptfe-mmu-top-on-prusa-enclosure
into the enclosure into the back of the MMU unit eliminating the buffer all together.
It seems to travel through them smoothly, loading and unloading it. The bearing and gears just seem to be struggling a bit.
Does the layout look as if it can cause problems or is it likely the filament choice? I just had these handy because i've used them lately just to throw in the drybox really quick to test this thing out.
RE: I am not sure what I am doing wrong with my MMU3 unit.
Those filament paths look fine actually. Straighter than mine... 🙂 But to completely eliminate that concern, just open the idler completely and push the filament until you can grab it, and pull it a bit more. If it's not really easy then start looking for restrictions or binding spots.
Assuming that's all good, how about the idler tension screws? Are they flush with the top of the housing (the usual starting point for adjustment)?
Also, with the idler open, when you push the filament through each PTFE, does it lay exactly on the middle of the toothed wheels? And do the idler wheels line up perfectly with those toothed wheels?
Reading the comments on the MMU3 assembly guide gives more clues that you can follow up with. Hopefully there are others who have some ideas...
Prusa MK4 since Jan 2024, Printables: @MikeB_1505898
RE: I am not sure what I am doing wrong with my MMU3 unit.
I just checked the alignment and it looks fine to me. Actually the first few lanes are aligned better than the last two which adds further confusion as to why the last two spools feed fine when I am having so many problems with the first few.
I had to give it a rest yesterday, it was getting frustrating.
Today I am going to remove all of the silk PLA and see if it works any different with a different filament.
RE: I am not sure what I am doing wrong with my MMU3 unit.
Just to clarify, you mention the printer is clicking and making lots of noise. Is that the Nextruder in the MK4S, or the MMU3 feed that is clicking? When you also mention forcing the filament through, that makes me think it's the MMU3 that's having the issues. Is that correct?
It's starting to seem like there's something out of whack in the assembly of the MMU3 - maybe the selector isn't lining up right with the filament, or the hole is blocked, or something like that...
Prusa MK4 since Jan 2024, Printables: @MikeB_1505898
RE: I am not sure what I am doing wrong with my MMU3 unit.
There is nothing at all wrong with the printer. I did the MK4S upgrade a few months ago and it has been printing great. I did the Nextruder upgrades for the MMU on Friday but when the printer did actually load filament, it printed nicely. I printed maybe 2 or 3 layers that was a circle split up into 5 colors as a test of the MMU unit. After that, I kept running into feeding issues.
The clicking occurs when loading filament. I tried my best to look at it and see if I could see anything with the idler body closed but it is difficult to pinpoint exactly where the click is coming from.
RE: I am not sure what I am doing wrong with my MMU3 unit.
May or not be helpful, but my main issue with the MMU3 ended up being too many clips constraining the filament loops in the filament buffer.
I had rotated mine 90 degrees like yours using a modified base ( https://www.printables.com/model/680464-top-loading-buffer-segmenter-for-mmu3)
and ended up having clips at the front and back of the buffer. This caused an issue that the filaments not always retracted fully from the mmu3 unit. Removing one of the clips allowed the filaments to loop outside the bounds of the filament buffer just slightly (which was enough) and all my problems went away.
e.g. try removing the clip circled here
RE: I am not sure what I am doing wrong with my MMU3 unit.
I could try removing a few, but I am honestly trying to eliminate the entire buffer. I have been printing auto rewinding spools this week put inside the drybox to eliminate the buffer all together. Haven't had a chance to mess around with it much this week but I will jump back into it this weekend.
May or not be helpful, but my main issue with the MMU3 ended up being too many clips constraining the filament loops in the filament buffer.
I had rotated mine 90 degrees like yours using a modified base ( https://www.printables.com/model/680464-top-loading-buffer-segmenter-for-mmu3)
and ended up having clips at the front and back of the buffer. This caused an issue that the filaments not always retracted fully from the mmu3 unit. Removing one of the clips allowed the filaments to loop outside the bounds of the filament buffer just slightly (which was enough) and all my problems went away.
e.g. try removing the clip circled here
RE: I am not sure what I am doing wrong with my MMU3 unit.
The fact that 1/2/3 does not load correctly and 4/5 does, would lead me to check and adjust the Idler Screw tension on the left side. Sound like the right hand screw is spot on, but the left might be too loose / tight.
RE: I am not sure what I am doing wrong with my MMU3 unit.
From my previous test when I initially posted, I'm going to say it was the particular spools of filament that were part of the issue. These were the very heavy Jessie PLA spools from PrintedSolid. Yesterday I had a small window of time and I picked different roles of filament. I was able to get the first lane to load correctly. The second lane would load correctly, but I kept getting errors where it would retract to the FINDA. It would feed into the printer just fine and then retract back and from there I was not able to see where it was retracting too but it would go through this process a few times on a filament load test and then give me the FINDA error code. Had not tried the other 3 lanes yet. Hopefully I can get some time today to work on it.
I also finished printing the auto-rewinding spools and I gave those a shot in this process. First one worked flawlessly. Second one as mentioned had issues. Not sure if it was the auto-rewinding spool or something else. I would prefer not having to use the buffer but if it sits beside the printer pretty well inside the enclosure then I may just go that route. At this point, I would just prefer all of this stuff to work. It is very disappointing after you spend a ton of time trying to get this stuff set up and you have this many problems with it.
I still have to figure some things out but I will work on it when I have some time available.