plastic jam in hot-end

Hello,

Today I tried to print the gauntlet of the "Raptor hand" (http://www.thingiverse.com/thing:476403) in scale 130%, to donate to the e-nable project.
It is difficult! Has anyone tried? Lots of bridging and overhang. Hard to get a nice surface.

After hours of printing the last part, I went for a short walk (I shouln't have done that).
The head was about 15 mm over the object, but no plastic came out. Could have been about 75 layers at 0.2 mm layers not extruding, just moving around in the air, maybe 30 minutes or so.
So, by some reason the plastic was not extruded. Could be some little particle in the filament, but I rather believe it was due to the following:
I have a 1 kg spool, and I made myself a crude spool holder (picture attached) by wiring some pvc tubes and a 3d-printed adapter for the roll (this will be improved in a near future). it went smoothly, but then I think the friction became too high, as I printed my adapter (black, hard to see in the picture) with too small inner diameter. Had some grease there, but apparently that wasn't enough.
So this may be the cause of the extruder not being able to pull the plastic down. Stupid me... too impatient, I should have designed it more carefully.

I printed at 212 celcius, with esun black filament from Gigamax3D, Hungary.
I have tried increasing from 185 gradually up to 212 and I found after many failed attempts that this was the least inappropriate temperature.
Some stringing, but not excessive. Slicing with skeinforge, nopheads settings.

Anyway,
I attached two photos, from above and underneath.
The plastic went off when I tried to pull it out. I tried to push a needle into the tip of the hotend, but it was too thick. I don't know if the plastic has been "baked".
How can I detect that?

I dissassembled the extruder partially, and I could see the hobbed bolt had small platic particles between its teeth. So it has to be cleaned.
I let the hot end hang out and connected the printer again. Heated up the end to 100 degrees and pulled gently with a pliers. It was stuck. Increased to 170 and tried pulling. Nothing loosened. Then the end went off. No more grip.
I guess I have to disassemble the hotend and drill into it somehow? Or dissolve it in, perhaps, sodium hydroxide?

How do I proceed?
The red tape seems to be of a special material, Can I remove it and put it back again, or do I have to buy new tape?
Is it difficult to remove the plastic?
Otherwise, I might order a new one from nophead, assembled with thermistor, red tape as it came with the kit?

A meta question about this forum:
I have many issues with various printing challenges, but I find it hard to post questions since I dont know how hard the rules are about how much research one has to do in the forum before asking things.
Is it ok to post a question like this, or do I have to post it as a reply in an existing thread if there is already a thread with the topic of my question?
For instance for this question, maybe I should search for all threads about jamming issues and post my question in the one that seems closest to my issue.
Ideally the mendel90 forum should be organised in categories.
Also I guess you want only one issue per post. It is tempting to mention all isues in the same post...

Best regards,
David

Hi again.
I saw this quite similar thread: [forums.reprap.org]
So, I think I'll try to repair my hotend.

Just asking for some advice about hotend repair:
1. how to remove baked (if it is baked, I'm not sure) plastic from the brass part of the hotend? Would it be possible?
2. Is it hard to separate the hotend's plastic and the brass parts from each other?
3. Can I reuse the "self fusing silicone tape", just temporarly? I can imagine one could attach it with some thing iron wire, I dont know.

/David

Edited 1 time(s). Last edit at 12/21/2014 05:19AM by dawa.

There is no need to remove anything, get yourself acupuncture needles, set the hotend to normal printing temperatures and push the debris inwards. Maybe now you can push out some filament so you can attach filament that you can use to pull out the debris: [hydraraptor.blogspot.de]

Ingo

Thanks! I thought about that possibility. So I'll go for it.
Thanks a lot!
/David

Hi again,
I tried the following:
1. I heated up the hot end to 215 celcius
2. I put about 20 cm filament in the extruder
3. I pushed a needle up the nozzle, and there seems to be nothing in the way. strange. there is some air in there
4. I extruded 5mm in slow speed, repeatedly to see if something would come out.
nothing happens, and the extruder cant press the filament down at all.
5. I remove wades idler and try to push by hand. totally blocked.

(edit: I wrote block, but I meant idler, corrected now, maybe doesn't matter very much anyway)

So, the blockage seems to be in the entrance of thehot end, where the filament is unfortunately cut off.
I guess that the filament is stuck in the upper part, and doesnt melt since it is too far away from the hot part of the hotend.
Any ideas what to do? increase temp even higher and push even harder?

BR,
David

Edited 2 time(s). Last edit at 12/29/2014 07:25AM by dawa.

If it is stuck at the cold end you need to remove the hot end from the wades block and heat it with a hot air gun. PLA becomes rubbery and can then be pulled out backwards with pliers.

If you haven't got a hot air gun you need to heat the whole hot end to about 70-80C. You can do that by building a make shift oven using the heated bed with a cardboard box over it.

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[www.hydraraptor.blogspot.com]

Thanks.
There is no margin, no plastic outside the cold end.
So there is no grip for a pliers. I thought I could drill into it, but it could be risky of course ...

Would it be possible to cut a piece of filament at an angle (much like a spear) and push that into the heated cold-end then attempt to pull out the combination as it cools?

With these situations I guess it always helps to have some filament still present at the cold-end entry.

Regards,
Neil Darlow

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

Maybe. There is really nothing to get hold on, I attached a picture in the first message in this thread.
Another idea is to push a crooked heated metal wire into the plastic at the "cold side".
For instance a short copper wire mounted in a soldering pen.
I can also try heating the hot end at the same time, and push down the plastic to free up the entrance.
I think I'll try something in that direction...

It worked! Many thanks to all of you for support and ideas!

I took some copper wire out of a cable, jammed it into the soldering pen, together with some thinner copper wires in order to get decent heat conductivity, and made a small crook in the outer end of the 1 mm copper wire.
I heated up the pen and melted the crook into the cold end of the hotend. Then I turned off the soldering pen and let it cool for a while.
Now, I heated the hotend to 90 celsius, and pulled the soldering pen.
It got loose, Poff! (see picture)

Cheers,
David

Well done.

Note that you don't necessarily need anything sticking out to get hold of. When PLA is heated past its glass transition it is like rubber, so you can dig slightly opened needle or snipe nosed pliers into it and close them to nip it and then pull it out. It stretches and so gets thinner, so it pulls away from the sides easily.

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[www.hydraraptor.blogspot.com]