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 guys. i had a pocket blow-torch on hand and i fired heat directly at the gears and it was juuust enough to make the PLA malleable. and yanked it out. add a pocket blow torch to your toolkit :)

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ok, guys, I tested the following: new, coated heatbreak and nozzle from microswiss, new PTFE-Tube, everything cleaned and scrubbed and... Still got jams. But only with Prusa-PLA and Colorfabb-PLA. All other materials I tried so far, seems to work, although I printed only small parts since. Now, I won't use those crappy PLA's anymore, I got more expensive ones that work. But I'm still some kind of disappointed about this printer. Prusa support is kind and try to help, but the help does'nt really help ;) In the meantime, I ran in another problem concerning dimension-issues when printing taulman nylon, but thats off topic. Cheers, Lorenz

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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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This method cleared my filament jam when I was using Wood filament. Thank you Jakub Dolezal for the tip.

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Hi Nick, glad to hear it helped ;)

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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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get a small blow torch and fire heat directly onto the gears. you only have to do it for like a second or so maximum.

it sorted the pla enough for it to be pulled it with no fuss. i then let the extruder run the filament through and a big blob came through but it came out.

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Unplugging the filament sensor worked for me too! Thanks guys!

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This happened while printing a rather small item. The filament broke and loading filament generated load clicking. I heated up to 255 and let it sit for about 5 minutes as suggested in another post. After numerous attempts of loading and unloading the filament it finally extruded PLA.

Now I am printing a test pattern and am a bit leary I hear a random click this sound like the filament is not feeding correctly. Will keep an eye on the current setup and post if it fails again.

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Hi, my experiment is not complete however I wanted to share this data sooner than later.

Mk3

Filament sensor is installed and enabled in software.

A Texas Instruments LM35 is secured to the top surface of the extruder stepper motor using electrical tape.

LM35 configured per datasheet to give 10mV/C.

HP3478A monitors the LM35 circuit output.

Room temperature at start of experiment is 80F, or 26.7C.

Using the PLA that came with the Mk3 kit.

Many successful prints at the 150um setting using Slicr3. Almost no success at 100um,

A 10mmX10mmX10mm cube is the test print.

Standard settings in Slcr3 used, 150 um, 100um 50um.

Using 150um layer thickness the print was 90% complete after 11 minutes and the LM35 reported extruder temperature of 33.8C, a rise of 7C. A plot of the temperature vs. time, taken about every 3 minutes, suggests the temperature was approaching an asymptote.

Using 100 um layer thickness the extruder was at about 34C at the start of the print and was 90% complete after 18 minutes. The temperature at 18 minutes was 39.6C, a rise of about 6C. A plot of temperature vs. time suggests the temperature was at its peak.

Using 50 um layer thickness the extruder was at about 41 C at the start of the print and after 12 minutes, 30% complete was at about 43 C. The print probably failed at about 4 minutes in. The extruder was making the clicking sound. Print was terminated at 30%. Filament path is severely jammed up. Usually I can pre-heat to ABS temperature and get the "Load FIlament" to clear the PLA. Not this time. I'll take the fan off and try ABS temp again. If it doesn't clear I'll use the 1,5 mm wire method.

My plan is to repeat the experiment with the filament sensor disconnected.

In addition to using the LM35 I also placed a finger lightly onto the extruder motor. It was warm, but not uncomfortable.

The measured temperatures seem low to cause deformation?

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Repeated with the filament sensor disconnected. 150 um layer thickness and 100 um layer thickness the extruder heated 10C in ten minutes of printing with the rate of heat increase decreasing. Meaning it looks like the extruder will hit some peak temp and quit getting hotter. No jam.

At 50 um layer thickness the extruder jammed within 2 minutes of printing, about a 2C rise in extruder motor temperature. The jam was 2.3mm diameter region on the filament. Summary: My measurements for don't show any difference in extruder motor temperature with or without the filament sensor Unable to print 50 um using 210C extrusion temperature. I like the hypothesis others have presented here that the jam is due to too much heat in the upper end of the filament feed path leading to deformation of the filament. My data of extruder motor temperature sdoes not upport extruder motor being the cause. I'm wondering if the thinner layers result in such a slow feedrate there isn't enough volume of plastic to take in the heat.

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@paulstevenson upgrade the FW to 3.2 and above - it decreases the stepper motor current which was causing the PLA filament to warp (for some)

IF that doesn’t resolve the issue, ask Prusa to replace your filament sensor.

Those two actions together got me back in action!

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Charles will be eternally grateful.
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