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MMU needs user attention - filament clogged MMU2S  

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jason.nemirov
(@jason-nemirov)
Active Member
MMU needs user attention - filament clogged MMU2S

I'll start off here... the MMU2S is the crappiest piece of engineering ever invented. At least halfway through every Print, it stops and says "mmu needs user attention." I unclog the filament in the gear and there is a lot of tension and drag in the PTFE tubes. I can't do anything about it. I tried adjusting the settings as well as the cooldowns and speed stuff but nothing works. I also tried changing the temperature of the nozzle. Is there anything I can do? If not, I am seriously considering fighting back with prusa for a refund AND purchasing the BETTER multi-material upgrade called the PALLETTE 2. It may be more expensive, but it is so much more worth it. Thanks guys!

 

Posted : 03/01/2020 10:48 pm
Nikolai
(@nikolai)
Noble Member
RE: MMU needs user attention - filament clogged MMU2S

Hi Jason,

Sorry for your frustration. If you can provide more details on your issue we could try to give you better hints. Like how often does it happen (every 1/10/100/1000 tool changes), what kind of filament are you using, what kind of settings are you using right now, what printer MK2.5/MK3 ...

Based on your vague description your filament tip is too thick. It can be because of over extrusion, thick filament, wrong settings ...
Some pictures of the filament tip could be also helpful to see what's going on.

If you think Palette2 is a better product for you, then go for it. MMU2 needs always operators attention. I would say it's part of the design. Sometimes it's around ~1000 tool changes, sometimes ~2000 and sometimes 1. Depends on the filament/settings used and the operator. 

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 03/01/2020 11:06 pm
jason.nemirov
(@jason-nemirov)
Active Member
Topic starter answered:
RE: MMU needs user attention - filament clogged MMU2S

I can't take pictures right now but I am using matterhackers pla at 215c on the nozzle and 60c on the bed. I am also using the prusament preset which worked fine on the single extruder. The only settings I changed were unload speed at start which was changed to 120 and number of cooldowns which was changed to 3. I am using the i3 mk3s. Btw, the filament is 1.75mm diameter and the issue happens about every 10 filament changes. Hope you can respond fast! Thx.

Posted : 04/01/2020 12:11 am
Nikolai
(@nikolai)
Noble Member
RE: MMU needs user attention - filament clogged MMU2S
Posted by: @jason-nemirov

Hope you can respond fast! Thx.

Why? Is there any emergency? 😊 

Go back with cooling moves to 1. If it's MH PLA pro, consider to go higher with the temp. Your filament tip should become more stringy but thinner.
Some background: With more cooling moves, the filament tip will also get harder. If it doesn't have a perfect shape, it will get stuck. With only one cooling move it can still be squished a little bit with the gears.

I had bad experience with MH PLA and MMU2. Best worked Hatchbox PLA with low temp ~195C and Polyalchemy  PLA is my favorite for MMU2. So you could also consider trying out different PLA filament types and see how they perform with default settings. Hope that helps a little bit.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 04/01/2020 12:27 am
jason.nemirov
(@jason-nemirov)
Active Member
Topic starter answered:
RE: MMU needs user attention - filament clogged MMU2S

@nikolai-r

Thanks. I do have the MH build series pla but the problem is that I bought like 7 spools of them, thinking that they would work well and I don't want to put them to waste.

Posted : 04/01/2020 12:32 am
Nikolai
(@nikolai)
Noble Member
RE: MMU needs user attention - filament clogged MMU2S

@jason-nemirov

Sure thing. Try the recommendation above. You might also tighten the screws on the MMU2 a little bit more, so it has more force to pull out the filament. I'm pretty sure it's doable to reach at least 100-200 tool changes without intervention with this filament. Don't care about the small strings at the first stage. This is the last step in calibration process.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 04/01/2020 12:37 am
jason.nemirov
(@jason-nemirov)
Active Member
Topic starter answered:
RE: MMU needs user attention - filament clogged MMU2S

Thanks! Just started another Print! Hopefully it will be good.

Posted : 04/01/2020 12:39 am
Nikolai
(@nikolai)
Noble Member
RE: MMU needs user attention - filament clogged MMU2S

Another hint in this process. Start with two color print and pick selector 1 and 5 (far away from each other). Once one filament is used, you can always push out the other filament a little bit and check the filament tip (don't forget to pull it back it 🙂 ). Feel also free to choose different temps for this filaments. For example 200C and 220C. You should also see a difference pretty quick. That should help to see what's really going on pretty fast without many slices/start/stops.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 04/01/2020 12:43 am
Nikolai
(@nikolai)
Noble Member
RE: MMU needs user attention - filament clogged MMU2S

BTW: MH build series PLA has one of the worst tolerances (1.75 ±0.07mm). Not really ideal for MMU. And I can recommend to print a temp tower 190C - 220C to check if it's printable in this range and how stringy it is at certain temp.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 04/01/2020 12:51 am
jason.nemirov
(@jason-nemirov)
Active Member
Topic starter answered:
RE: MMU needs user attention - filament clogged MMU2S

Thanks. I just tried a print but it stopped at the first layer while trying to switch and the gears can't seem to reach or get a hold of the filament. What can I do? I've tried tightening the mmu but no luck.

Posted : 04/01/2020 12:57 am
Nikolai
(@nikolai)
Noble Member
RE: MMU needs user attention - filament clogged MMU2S

Have you used the filament from the old tries? If yes, then you need to cut big chunk of it (length from extruder to MMU2). Maybe it's eaten up somewhere in between.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram...
Posted : 04/01/2020 1:03 am
jason.nemirov
(@jason-nemirov)
Active Member
Topic starter answered:
RE: MMU needs user attention - filament clogged MMU2S

@nikolai-r

Yes but I already did so.

Posted : 04/01/2020 1:05 am
jason.nemirov
(@jason-nemirov)
Active Member
Topic starter answered:
RE: MMU needs user attention - filament clogged MMU2S

I am going to try a dual color print with whatever prusament I have left and then get back to you. 

Posted : 04/01/2020 12:57 pm
jason.nemirov
(@jason-nemirov)
Active Member
Topic starter answered:
RE: MMU needs user attention - filament clogged MMU2S

Hey I'm back. I tried printing with two prusament pla filaments and it could not load the filament into the extruder. The print didn't even start yet and it couldn't load. I am ordering capricorn tubing to see if it could fix the issue.

Posted : 05/01/2020 9:39 pm
wpegden
(@wpegden)
Trusted Member
RE: MMU needs user attention - filament clogged MMU2S

This video is old now but it still has some good tips I think:

 

For me reducing friction in the filament path really seemed to help.  In particular through where the ptfe tubes come in the back.  I used this mod to improve this and it seemed to help:

https://www.thingiverse.com/thing:3233579

Posted : 20/01/2020 3:47 am
wpegden
(@wpegden)
Trusted Member
RE: MMU needs user attention - filament clogged MMU2S

Oh one more thing.

When printing with PLA, heat creep from the extruder motor can sometimes be enough to cause bulging near the tip, if the printer is not in a cold environment.  There are some shrouds on thingiverse to add a fan to cool the extruder, but I just ordered two of these heatsinks and stuck one on top of the extruder and one on the left side. $3 each and self-adhesive:

https://www.digikey.com/product-detail/en/cts-thermal-management-products/BDN14-3CB-A01/294-1101-ND/272739

Posted : 20/01/2020 3:53 am
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