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Clogged extruder

Posted by Rural 
Clogged extruder
July 07, 2016 01:13AM
A recent print failed, which is fairly rare for my Mendel90. Unfortunately, it failed in a new (for me) way. For some reason, which probably involves one of my sons, the print bed was badly out of level. Of course, I didn't know this when I started the print. It didn't look quite right when printing perimeters, but still looked like it would work. When I came back later I found that the hobbed bolt had clogged up before finishing the first layer. It looks like the nozzle was basically blocked and the back-pressure built until the hobbed bolt tore the filament to shreds. A bit of inspection has confirmed that the hobbed bolt chewed into the filament.

Trying to remove the filament (85C, M302, retract 100mm with help from me to get it started), I can't get it to budge. I've tried hotter temperatures with no luck, but am getting nervous. I think that the filament melted well up the hot end and is unwilling to let go.

Unfortunately, with the Mendel90 version I have, I can't remove the hot-end unless it is free of filament. But if it were free of filament, all would be well.

Any suggestions? I'm thinking I might be able to get something sharp between the top of the hot end and the part that holds it. If I can cut through the filament, I can remove the hot end. But I'd rather just soften the filament to the point that I can pull it free.
Re: Clogged extruder
July 07, 2016 01:49AM
Got it! Most of it, at least. See the attachment.

I kept raising the hot end temperature by 20C, letting it sit for a few minutes, then tried retracting with manual help. At normal extrusion temperature for this filament (205C), I let it sit for 10 minutes, after which, it released. The attached picture shows the result.

Just have to clean off the hobbed bolt and probably clean out the nozzle, then I'm just a bed levelling away from being back in business.
open | download - hotend_clog.jpg (441 KB)
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