MMU needs user attention - filament clogged MMU2S  

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. 

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.

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.

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.

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.

RE: MMU needs user attention - filament clogged MMU2S

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

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.

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.

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.

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.

RE: MMU needs user attention - filament clogged MMU2S

@nikolai-r

Yes but I already did so.

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. 

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.

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

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