Is there a fundamental problem with the Prusa i3 MK3 design? It's time to talk about blob filament jams.

Is there a fundamental problem with the Prusa i3 MK3 design? It's time to talk about blob filament jams.  

New Member

A week after I assembled my Prusa i3 MK3 kit, I had a print job fail due to a filament jam. I tried various clearing techniques like checking the nozzle with the acupuncture needle, heating up the hotend to PLA temperature setting and even higher (eventually all the way to 290c) and ended up disassembling the extruder assembly to find the problem. But I think the problem is really just a symptom.

In researching my problem, I've found others with the same or very similar problems: (my personal thread)

A Google search reveals that many people (no idea how many or what percentage) are experiencing blob filament jams with their Prusa i3 MK3. It may be that heat creep within the E3D hotend is warming the filament too close to the Bondtech drive pulleys. Many of the problems I've seen, and my personal one, had a blob of filament below the pulleys and above the PTFE tubing leading into the heatbreak of the hotend. Another symptom is the filament stops advancing, causing the extruder stepper motor to click like it's skipping gear teeth. The Prusa filament sensor is supposed to sense filament jams and stop the print, but it seems that it isn't working correctly.

Is anyone seeing a trend of a problem with the extruder assembly and print blob jams, or is it just me being over-sensitive?

VidMate AnyDesk
Posted : 24/08/2018 6:26 pm
Noble Member

Hello Jaison,

This topic was already discussed so heavily. Some people like myself are tired to discuss any "generic MK3" problems. Please use the search function and try to understand out why the specific model failed (and most likely repeatedly). You will find many hints how to reduce the risk of heat creep.

You can also post an image of your blob under the gear, sounds interesting.

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Posted : 24/08/2018 9:23 pm
Active Member

I did not believe there was a "fundamental flaw" with the Mk3 design but I have always suspected there was something seriously wrong with my factory assembled Mk3. I have a Mk2s that always printed better than my Mk3. My Mk3 suffers from inconsistent extrusion, skipping, and random jamming. This weekend I upgraded my Mk2s to a Mk2.5. The quality and consistency on the prints is INCREDIBLE. My first layers are absolutely consistent and perfect. I did a 24 hour print with PLA and the extruder never skipped or jammed. I can't find any skipped layers or imperfections. The Mk3 would have failed or at least had many skipped layers. I have been printing non stop with the Mk2.5 since Sunday and I absolutely love this thing. My Mk3 is mediocre at best.

Is there a fundamental problem with the Mk3 design? I don't know. I do now know for sure that there is something fundamentally wrong with my Mk3.

Posted : 05/09/2018 5:49 am

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