Filament Jam on the MK3

I just received a pre-assembled MK3. It was printing fine until I had to change the filament. Halfway through a 10 hour print. The extruder started clicking again( I previously fixed this by removing the filament and running filament through the whole thing a few times) I noticed there was no plastic coming out of the extruder. I stopped the print and did a remove filament procedure. The filament would not come out, I pulled and now a piece of filament is stuck in the tube running up to the barels. How do fix this problem? This is my third prusa. I have the MK2 and MK2S and now the MK3. I am having more problems with my MK3 for some reason. I assembled the MK2 and MK2S myself. So I am unfarmilar with the extruder on the MK3. Is this a common problem with the MK3 and how do I remove the filament that is stuck and prevent it from happening again?

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Hi

I have the exact same issue. My MK3 worked perfect after assembling. After printing some parts with PC at 270 nozzletemp and 100 bedtemp and switching back to PLA, I had one jam after the other. The only PLA I can make to work is PolymakerPLA, but the prints are not to good in quality. All other brands = jam.

I tried all advices from the prusa-help, the e3d-site and other forums, but nothing worked, the printer jams after about 1.5 hour of printing with 50microns and after about 2.5 hours with 100 microns.

Extrudermotor gets hot to about 60-70 C. Jam is always somewhere in the heatbreak, the nozzle is always free. It seems that heat is going up and passes the break and goes up further, what is strange.

But: I read alot about the exact same problem with the e3d v6...

I read, to change the heatbreak to a coated one could help. I doupt, that this will help, but I'll give it a try. I'll keep you updated, but its gonna be somewhere within the next week.

Cheers

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Hi Lorenz, it might be there is some filament left and causing the jam, try heating up the hotend to 285-290 °C, release the idler and carefully press through a straight metal wire (like the filament would go). Also, the PTFE tube inside might be damaged, this would require getting a new one and changing it.

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Hi Charles,

Extruder construction for MK3 is visually different, but the logic behind it is the same ("feeding" pulley + hotend).

In your case try to heat up the hotend to high temp (270-280°C), let it hot for a while (4-5 minutes) and then try to load the filament again.

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One interesting point. I think using simply 3d as my slicing program may have contributed to the problem. It seems files over 65k end up incomplete causing the print to stop extruding and jams the extruder. Switching to Slic3r really helps with projects with large files and long print times.

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I had a very similar problem.

I have a Mk3 and I was 5 hours into a 20+ hour print, using PLA.

The filament Bondtech Pulley Idler began to make a clicking sound and very little plastic was extruding out of the nozzle. I tried doing a filament unload/reload several times and it came good for a few more layers of printing, but then the clicking began again.

To solve this issue, I loosened the M3x40 screws securing the Extruder Idler (shown in Step 15 of the Mk3 Assembly instructions (also, don't forget to take out and place the Idler-plug somewhere safe, a picture of this is found at step 43)) and eventually found a small (1.5mm) fragment of plastic caught between the Bondtech Pulleys. This fragment must have been impeding the filament cable and partially displacing it every so often. It is show in the tweezers in the picture below.

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What caused the filament to break: I don't know. It is possible the original clicking was due to another issue, and I inadvertently caused the second lot during the unload/reload routine. If the print continues without further problems, I'll assume it was due to the fragment after-all and update this post and let you know.

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I am also having the same issue with a filament jam. However, it visually looks like the filament itself has melted right beneath the pulley. Which would be very odd for the heat to get that far up.

It only happens on the tops of objects, meaning the print is slowed down due to S3Ds rule of "Reduce speed if layer will take less than <x> seconds" Approx 15mm/sec

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I found what was happening is that while the printer is idle (if the nozzle was left pre-heated for too long), that the filament tip was forming a slightly bulbous plug on the end. This prevented the filament from being forced into the hot end. And further, this plug was not allowing the filament to extract out of the aperture at the top (stopping below the pulleys). In the first case I had above, I force-ably pulled the filament out, (I now know) breaking off this plug inside the pulley assembly, which subsequently jammed the filament. I had to open the idler and manually remove this broken bit before reloading the filament.

Maybe, in your case, it is the friction of the pulleys eroding the filament, which is not being pushed through.

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Thanks Nate for the thoughts, but I've just discovered what is actually causing it: the extruder motor is getting too hot, which puts heat onto the shaft, causing the PLA to soften right beneath the gears - which then jam it there. Some on the forums think it is the filament sensor that is causing this (not sure!), but support had told them to unplug it, and things worked fine again. Happy printing!

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This is exactly what I am experiencing: About an hour into a print when working on slow, detailed parts the PLA jams beneath the gears. How does unplugging the filament sensor help? (Has that actually solved your problem?) Thanks.

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It turns out that there was a bug in Simply3d slicer. large prints were not slicing correctly and were too large, thus being incomplete. This caused problems with the printing and the extruder. Once I downloaded the bug fix and cleared the nozzle, it prints fine. I figured it out, by switching to slic3r and it worked and then when I tried Simply3d it failed. Then downloaded the bug fix and it prints very well so far.

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It has nothing to do with Simplify3D, since even small parts have this issue and I have the latest version w/bugfix.. If a print were truly incomplete, it would simply stop printing, not melt the filament inside the extruder. Pat, I can't explain why unplugging the sensor works, but after a lot of failing, I can tell you that it does! The extruder motor doesn't get as hot now, and I finally have a working printer. Unplug it for a long print and give it a go!

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