MK3 Extruder clogged after 28m / 1d4h printing  

Re: MK3 Extruder clogged after 28m / 1d4h printing

It seems the only way to fix a badly clogged extruder on the MK3 is following the steps in the assembly instructions backwards. This seems a tedious job, there seem to be no shortcuts and the design is not optimized to fix this problem easily.
Is a jammed extruder really so a rare problem or is there a way to fix this that I have not found, yet?

Re: MK3 Extruder clogged after 28m / 1d4h printing

It is not a rare incident, but it is generally an unusual condition or improper operation that causes it. It would help if you could describe what led to the clog condition.

Have you tried heating up the extruder to at least 25 degrees above the filament temperature and then running the acupuncture needle through the passageway? You need to see if there is anything lodged in the heater block.

Re: MK3 Extruder clogged after 28m / 1d4h printing

Hey Reid,

thanks for the answer. I fixed it and I learned a lot. So for further reference and to shame myself here is what I think what happened:

I tried to print a model with two filament changes shortly after each other. Since this was a mistake in my code (there should only be one change) I didn't change the filament the second time. I did not remove the filament "immediately" but I thought that it would just stay on the filament it had. So the extruder failed not accidentally when I (not) changed the filament but because of it.

Heating up to a temperature higher than PLA and cleaning the nozzle with a needle did not help, neither did removing the nozzle. Here I realised that I was in trouble, because the extruder was obviously clogged above the nozzle. And here the time Prusa took to deliver my MK3 was suddenly very useful. I think I watched most videos on filament printers on youtube while waiting for my preciousss printer and so I had an idea of what may have been wrong.
So I took the extruder apart, which took me a few hours, because I was very unexperienced and careful. But it's possible to take apart the extruder only from the front and only to remove a few relevant parts. I removed the hotend

I heated up the extruder without the cooling-fan (after checking what the maximum temperature for PTFE is) and removed the hotend from the coldend (that was a little hot now, too.)
I removed the heat fuse (the little connecting piece between them?) and cleaned it. It was full of filament on both sides.
I removed the filament from the hotend side of the PTFE-Tube in the coldend. This piece capped the end of the tube and absolutely made sure that no filament would evermore reach the liquifying heat of the extruder.

I put everything together and - surprise - it works again.

So I learned a lot today:
- Changing filament is serious business. If Prusa says "remove immediately" you remove immediately. He has a plan.
- You can take apart the extruder. If you are careful not to rip off the cables at the hotend (power and temperature I guess) it will work if you put it together. Just remember that the nozzle is not flush with the hotend but the distance is caused by the nozzle and the heat fuse meeting inside the hotend and thus sealing the connection (do I make sense?)
- 230C is awfully hot. You will burn your fingers. The hotend may not /look/ hot, but you'll burn your fingers every time you touch it and it will hurt while typing an answer into the forum.

Re: MK3 Extruder clogged after 28m / 1d4h printing

- 230C is awfully hot. You will burn your fingers. The hotend may not /look/ hot, but you'll burn your fingers every time you touch it and it will hurt while typing an answer into the forum.

I was wondering why the word "HOT" was printed on the printer..... 😆

Re: MK3 Extruder clogged after 28m / 1d4h printing

You can’t see the word ‘HOT!’ when the fan is unmounted 😀

(Of course, I’m not complaining)