ScorpioEF
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Re: Blockage troubleshooting.

Dec 12, 2017 8:42 pm

Hi, just to share my experience. I tried to print with Unicofil PLA Rainbow. I had 3 failed prints by blockage between the PTFE tube and the heat-breaker in single filament mode. The last one was at 205°C and no retraction at all in Slic3r settings. So I tried to re-seat the PTFE tube and now it fails every time halfway through the "first layer calibration" bundled in the firmware. Every single time blockage between the PTFE tube and the heat-breaker. I then switched to a white ColorFabb filament and no problem at all.

So maybe it's just me, but Unicofil PLA Rainbow filament doesn't work with this machine. I even used a caliper and the diameter seemed very consistent.

nils.t
Posts: 187
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Re: Blockage troubleshooting.

Dec 13, 2017 12:42 pm

I looked up Unicofil and they say on their website it is based on Natureworks Ingeo with embedded corn starch. So the basis is exactly the same as for my Sakata Ingeo, which has absolutely great tolerances as well. Just speculating, but maybe the problem is with the distribution of the embedded starch fibers. If this is irregular, it would lead to differing friction and melting points within the filament. Bottom line: stick away from Ingeo with the MMU.

joris.m
Posts: 189
Joined: Oct 08, 2017 9:23 am
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Re: Blockage troubleshooting.

Dec 17, 2017 5:37 pm

I have prints failing all the time now, in single extrusion mode. If I use multiple colors and switch a lot no problem, but a single color print fails after a couple of layers with a blockage just below the ptfe tube. I can simply remove the tube, cut the blockage and restart printing, only for it to happen again after a couple of layers.

It's driving me nuts. No idea what's going on, I already lowered the PLA temperature a couple of times but the problem remains.

If anyone wants to have a shot, here is the file that consistently fails on me, it uses extruder 1:
reno.gcode.zip
(3.76 MiB) Downloaded 3 times

nils.t
Posts: 187
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Re: Blockage troubleshooting.

Dec 17, 2017 9:20 pm

Itˋs about bloody time someone from PR comments on this. At least acknowledge something is wrong.

gregory.s4
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Re: Blockage troubleshooting.

Dec 18, 2017 2:19 pm

I am getting super fed-up with this issue at this point.

I've tried every conceivable slicer and slicer setting.
I've tried inconceivable slicer settings.
I've rebuilt the entire hotend.
I've ordered replacement heatbreaks, ptfe tubes, steel tubes and paid the huge shipping costs.


Lately, I can't even get 50% of my single-filament models to print anymore. I almost wonder if this is essentially a heat-creep issue. I think my next step will be to break into the extruder design and super-cool the heatsink. But I'm not hopeful.

I really hope Prusa and Co. haven't responded because they've been busy fixing the issue and any day now they will swoop in with the solution. Or more likely, they're putting Mk3's in boxes... I would've ordered one myself, but this MMU has soured me lately.

nils.t
Posts: 187
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Re: Blockage troubleshooting.

Dec 18, 2017 3:31 pm

I would've ordered one myself, but this MMU has soured me lately.
Signed. In fact that was my plan since it was obvious that some flexibility and quality would be lost when installing the MMU. If it somehow worked reliably at least with PLA/PETG/PVA, I'd eventually move towards a second printer. But not at this point. What's most frustrating is that I know it can produce great 4-color quality, my demo prints look awesome.

tarek.l
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Re: Blockage troubleshooting.

Dec 19, 2017 3:15 am

Hello all,

I want to thank the people here for the extensive discussion about the MMU's blockage issues. Like many here, I made the mistake of thinking that my extensive experience printing with a single extruder (and some dual-head dual extrusion) would make the MMU work easy.

I think the most important thing for me was to do serious failure assessments and extensive printing until I 'got it'. In the end, the main key for me was playing with temperatures. Even though I use exclusively filaments.ca filament, almost every different colour has its own temp. I start with 205/198, and then go up and down as necessary depending on the blockage. Until now, I have tried about 10 colours, and I would dare say only a couple worked without modifying the temperature. up or down 2C.

How do I do my failure analysis?

I start at 205/198 and then go until failure. Once that happens, I take out the filament that failed and look at it. If it has a hair, then I reduce the temp. If not, then I increase the temp. Repeat until success, and then lock down that number for that filament in a filament profile.

Like you, I wish there were more information about this. I think barring this, my advice to Prusa Research is: Just call this an "advanced" user or "professional" upgrade or "beta" product. I WANT Prusa to keep working on this. I had a Prusa i1 and it was freaking hard. But the constant work and feedback and input gave us the mk3. We are in early days for multicolour printing. This is the Gestetner. I want PR to keep working on it. At the same time, I can see why users feel betrayed: Not many people expected to buy this thing and spend hundreds of hours learning multicolour printing.

Thank you to PR and to all of you for the community.

tarek : )

mike.m18
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Joined: Nov 10, 2017 6:33 pm
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Re: Blockage troubleshooting.

Jan 02, 2018 12:27 am

I have had the mm printer since November 28th. For the first few weeks I printed 4 color objects with no issues. The last 2.5 weeks I get a clogged steel tube in one of the 4 chambers. It is never the same one. I have reduced the temp to 200 as suggested by Peter. I have emailed Prusa multiple times, and have yet to get a suggested solution. What would cause the printer to degrade within a few weeks? Of course, 1 color prints fine. 2 color , sometimes, 3 color maybe (2 out of 3 whale prints), 4 color fails after 3-4 hours due to a clogged steel tube. BTW, I got to page 28 before throwing out a help post. Filaments used are Hatchbox, Atomic, and Solutec.

michael.a23
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Joined: Aug 23, 2017 11:33 pm
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Re: Blockage troubleshooting.

Sep 12, 2018 3:59 am

Hello all,

I have been reading through this forum looking for an answer and unless I missed it I havent come across anyone with the same problem I have been facing, I have a MK2/S with MMU1.0 and I keep getting a jam right before the heatbreak. It seems as though the filament is too larger to enter the Heatbreak to melt again. When I start the print I snip all the filament ends and they load fine and run the pre print wipe fine, but then after a few filament changes, boom, jam. The filament just wont load into the heatbreak to melt, it will try to print and nothing will come out, then it goes to change color again and the other filament will load, sometimes it wont. Like I said i have been looking and reading through this forum hoping for an answer or something to try. Please if anyone has anything i would love to get this working. Thanks in advance!

johann.d
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Joined: Sep 30, 2016 8:47 am
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Re: Blockage troubleshooting.

Sep 26, 2018 1:29 pm

It has been mentioned numerous times now but there's an alternative multiplexer part - https://shop.prusa3d.com/forum/-f26/mon ... 12801.html - without steel tubes.

This one *completely* fixed the jamming problem on my printer, while I could hardly finish one single print with the original multiplexer.

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