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I hate my MMU2s  

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Romio
(@romio)
Active Member
I hate my MMU2s

Ever since i got my MMU2S (firmware 3.8.1) installed it's giving my headache.

What's going on.... Where to begin......

A multicolor 55 minute print with  19 color change takes 2 hours to complet. Why? Almost every color change i need to reset the mmu or pull filament out because the retracting doesn't do anything. Sometimes the mmu changes filament without pulling the last used filament out. Or the latest issue. The Filament only pulls out halfway. Filament cutting doesn't work even with the "improved" mmu selector. So I need to cut the filament by hand if the extruder doesn't accept the filament.

Even with a single color print there issues. After a print is at 99%  the filament won't retract. All off the mmu lights are flashing. I need to retract the filament en reset the mmu before the printer says he's done.

Help, help. What can i do besides going crazy and throw away the mmu.

 

Best Answer by karl-herbert:

Welcome in Prusa Forum!

There could be many reasons for this. Precise assembly is generally importan. You could change the 4/2 PTFE tubes against 4/2.5 tubes. The filament must be able to be transported easily. Check the gear drives. Are they clean and have they all the same diameter? 

Maybe you can find here a tipp/solution for your problems with the MMU2:

 

Posted : 29/12/2019 10:46 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: I hate my MMU2s

Welcome in Prusa Forum!

There could be many reasons for this. Precise assembly is generally importan. You could change the 4/2 PTFE tubes against 4/2.5 tubes. The filament must be able to be transported easily. Check the gear drives. Are they clean and have they all the same diameter? 

Maybe you can find here a tipp/solution for your problems with the MMU2:

 

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 30/12/2019 2:17 am
Romio
(@romio)
Active Member
Topic starter answered:
RE: I hate my MMU2s

Thnx for you're advice. 

After months of errors with mmu prints suddenly this morning i started a 5 hour print with 9 color changes without changing my setup. All color changes are done successful.  I'm at a lost. I need to wait until this print is done and try another print.

The mmu was properly scared after i treated is last night 🙄 

I saw the youtube clip a whille back. I'll check the alignment asap.

 

Posted : 30/12/2019 1:40 pm
Romio
(@romio)
Active Member
Topic starter answered:
RE: I hate my MMU2s

Happy new year to all.

It looked good for a second but wasn't.

After a 49 point test on the bed and before de filament selection the mmu restarts a 3 times resulting in all the lights on de mmu starts flashing. I needed the reset the mmu 3 times before it would load the filament.

At the first filament change the selector changes to another filament without retracting the previous filament en tried to load the new filament (that wouldn't load of course). It wouldn't even try to retract the filamant. Changing filament without retraction goes at random.

Problem a curse with and without octoprint.

Can someone help me?

Posted : 01/01/2020 2:29 pm
Simplexify
(@simplexify)
Active Member
RE: I hate my MMU2s

@romio

I've been struggling quite a bit too with my MMU. Turned a perfectly good running MK3 in a utterly frustrating experience. I've been fighting (and most of the time loosing) with it for almost 8 weeks now.

Only thing that seams to help is to factory reset and reflash the lastest firmware every 50 hours or so. When I do that, I can get some prints going until the next fight. 

The fact that resetting everything fix my problems for a while is leading me to think that the firmware(s) still need A LOT of work. 

That upgrade is a huge deception and definitely not on par with what we got to expect from Prusa in the past. Maybe they need to start thinking of us as customers instead of testers...

Posted : 27/01/2020 1:30 am
Stephen
(@stephen-8)
Active Member
RE: I hate my MMU2s

I was ready to return my MMU. Then I thought to contact the tech support live chat that Prusa offers. After spending several hours with them while I implemented their suggestions, my printer is printing better than it ever has. Just completed a 20 hour print with over 200 tool changes without a single intervention.

I'm absolutely loving my printer after tech support helped me tune the hell out of it.

Posted : 29/01/2020 4:29 am
Simplexify
(@simplexify)
Active Member
RE: I hate my MMU2s

@stephen-c30

Good to know! Can you elaborate a little on the main interventions they asked? I already spent 1h30 with them but nothing really good came out of it. It surely depends on the tech you get assigned and the kind of problem you have and I must admit, my patience got pretty thin at that point.

Even if I still wish I'd never bought the unit, at this point if I can make it work, I'd rather keep it and enjoy it.

Cheers

Posted : 29/01/2020 10:59 am
Stephen
(@stephen-8)
Active Member
RE: I hate my MMU2s

I ended up spending more than 5 hours with them as I was making the adjustments as they suggested them and then printing the five color, 16 tool change test print to test out their suggestions. I think it was 1 hr the first night, then 2-3 hours per night for two nights. Have patience. Each printer will have different issues. Let them walk you through fixing it.

Here's the two suggestions they made which had the biggest impact:

* Change my PTFE tube. Luckily I had a couple left over from the install. I've now ordered about 30 of them and plan on changing it once a month. In order to have a jam-free filament change, they need to shape the tip of the filament. They do this with a process called "ramming". They shove a large quantity of filament out the nozzle in a short time, then pull it back. The PTFE tube shape is essential to this. Now, when you change the PTFE tube, there are several VERY important bullets in step 8. If you miss one of them, you will have to disassemble the extruder and re-do it. Have the instructions next to you as you change the tube and follow every bullet point. Having done this, I watch the tips as they retract and they look perfect now. No stringing.

* Calibrate my IR sensor. And then the tech had me re-check my work on that. Sure enough, I hadn't done it right. The IR sensor is key for loading/unloading filament. It has to be spot on.

They had me fine tune what at the time felt like every last screw on the MMU. I'm thankful now. "What's that noise? Oh, I need to loosen the screws on the MMU idler". They also talked about cleaning the gears. I did so with a toothbrush, but need to get a proper wire brush to clean them still.

Lastly - print this and buy the M10 couplers: https://www.prusaprinters.org/prints/6605-prusa-mmu2-ptfe-holder-m10-passthrough-adapter/comments

That wasn't a suggestion by them, but it is such a major improvement to the "tighten the screw holding the PTFE tube in place, but not too much because then it will jam and not too loose because then it will fall out" approach of the original assembly.

Posted : 29/01/2020 1:33 pm
Stephen
(@stephen-8)
Active Member
RE: I hate my MMU2s

I've had very good luck with the techs. Many seem to have this as their hobby too. e.g. comments like "when I print, this is what I do"

They have become my go-to when having a questions. I post a video or photos to dropbox or Flickr and they are very helpful. I just found out about bed level adjustment which is in addition to the 49 point mesh leveling to help me get a perfect first layer. https://help.prusa3d.com/article/TPGip0OmaP-bed-level-correction

Posted : 29/01/2020 1:42 pm
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