Hot end jams

tom10122 · Post by **tom10122** » Sun Mar 03, 2013 7:47 pm

For what ever reason, my hot end is now jamming up frequently, no change in temp, it actually gets up to that temp, repeatedly torched the nozzle. I have been a week without jams until today. Any ideas? It doesn't even extrude the correct amount of filament when it is first is re done.

rs50pilot · Post by **rs50pilot** » Mon Mar 04, 2013 4:15 am

Mine started doing that to. I took it apart and found there was a tiny bit of resistance at both ends. I took a countersink and opened up both ends a little. Just enough so the filament slides smooth. Did this on both ends of the Bowden tube too.
Also made sure when I cut the filament that the cut was clean. Wire cutters will distort the end and make a burr. A razor blade makes a clean square cut.

tom10122 · Post by **tom10122** » Mon Mar 04, 2013 6:54 pm

I Have an H-1 so no Bowden and the ptfe is fine, could the nozzle possibly shrink after so much heat with the torch?

tom10122 · Post by **tom10122** » Tue Mar 05, 2013 9:21 pm

anyone?

mhackney · Post by **mhackney** » Tue Mar 05, 2013 9:27 pm

Probably not, however, how hot do you heat it? If to red hot, you will anneal the brass. Soft brass is quite easy to deform. Hold the nozzle up to a bright light and look through. It should be nice and round.

What are you printing when this happens? Do you use retract and if so, is that going on right before a jam? PLA or ABS? We need a fe more details!

tom10122 · Post by **tom10122** » Wed Mar 06, 2013 7:01 am

It may be deformed , I never heated it that much but that's all I can think of as the problem. I print in PLA and can't even use my hand to extrude filament through the nozzle. But when I look through the nozzle it Is round.

mhackney · Post by **mhackney** » Wed Mar 06, 2013 8:00 am

Thanks Tom, it really would be unusual to have deformed the nozzle to cause this problem. Many folks print with .35mm and even smaller nozzles. PLA is notorious for "barrel lock". Do you have a fan cooling the PEEK tube above the hot end/nozzle?

When you say you can't use your hand to push the filament through the nozzle I assume you actually men you are trying to push the filament through the entire hot end - PEEK barrel/teflon liner, hot end and nozzle. Is that correct or have you actually rigged up something to isolate and test just the nozzle? If the former, again, the blockage could be from the PLA locking above the hot zone.

With everything cold, remove the nozzle and push some filament through the upper part of the hot end from the Bowden connector through the teflon liner and out the bottom. Any significant resistance is an issue, it should be really easy to push. Check the teflon liner for constrictions, when it gets over heated, that can happen. And the PLA can expand to fill the tube and lock in.

Let me know re: the above.

regards,
Michael

tom10122 · Post by **tom10122** » Wed Mar 06, 2013 1:45 pm

i print with a .5 nozzle, i have tried putting filament thriugh the entre hot end and through the nozzle itself while being heated with a torcb same problem

mhackney · Post by **mhackney** » Wed Mar 06, 2013 2:20 pm

Tom, not sure what you are saying. Are you pushing the filament by hand? And when doing so through the entire hot end feel it is clogged? How about the other questions I asked above? I don't mind trying to help at all but you really need to open the information flood gate and provide answers and details!

At this point, I suspect you are just experiencing the typical issue that all PLA users experience - you are getting blockage due to the PLA melt creeping up into the cold area of the barrel and then locking in. The best way to eliminate this is to cool the upper part of the barrel (the PEEK area) with a small fan.

Torches are horrible devices to use to try to get a controlled temperature! You could very well be making the problem worse by charing the PLA with the torch.

tom10122 · Post by **tom10122** » Wed Mar 06, 2013 4:27 pm

I have a fan on my peek, when I push it though by hand it feels like it hit something hard, not really a jam . I have also tried pushing it through just the nozzle with no luck, as for the torch, I heated it up then test with a thermo couple and when it got to 220c I tried pushing it through, I am convinced there is something up with my nozzle.

Polygonhell · Post by **Polygonhell** » Wed Mar 06, 2013 5:52 pm

It could be a small piece of debris in the hotend, especially if you've been repeatedly cleaning it with a torch, I'd run a 0.5mm drill through it.
The PTFE liner could have deformed if you're getting it too hot.
If you were getting a "normal" PLA jam what would happen is assuming you start with an empty hotend when pushing through by hand it would extrude then get harder and harder to push through.
Have you checked what temperature you are trying to extrude at?

Post by **geneb** » Thu Mar 07, 2013 10:15 am

I'd pull it apart and check the teflon liners. I've had issue in the past with the inner liner being overheated and it shrinks a bit. You should be able to thread filament through the inner liner with little or no drag at all. If you get any, replace it.

g.

tom10122 · Post by **tom10122** » Thu Mar 07, 2013 4:46 pm

New ptfe (3rd actually) , and cleaned the nozzle really well with a pin and it extrudes properly now.

mhackney · Post by **mhackney** » Thu Mar 07, 2013 4:56 pm

Great. The PTFE used to cause me a fair amount of trouble swelling and locking the filament. I've added fans pointed at the PEEK on my printers and run it all the time. This issue has completely gone away and I haven't had to replace my PTFE at all for quite a long time (6+ months).

tom10122 · Post by **tom10122** » Thu Mar 07, 2013 5:25 pm

Yup, printing now, It seems to extrude a lot more then before (bigger strands) XD I think There was a lot of burned up filament in there for a while .

mhackney · Post by **mhackney** » Thu Mar 07, 2013 5:32 pm

Do this - position the nozzle about 8" above the platform. Then, extrude 10mm into air and let it hang straight down and cool. Once cool, measure the diameter in several places. It will likely be greater than .5mm, mine is .55mm. You can use this as gauge in the future to see if maybe something is blocking the orifice.

tom10122 · Post by **tom10122** » Thu Mar 07, 2013 5:45 pm

Ok thanks

Vallick · Post by **Vallick** » Sun Mar 10, 2013 5:33 pm

this must happen all the time with PLA cuz of the stock .5mm nozel

http://www.makerbot.com/support/guides/pla/
try using MK8 nozzle .4mm

https://www.google.com/search?q=MK8+noz ... e&ie=UTF-8

how are the prints with the restockmax any pics with prints Over 1300 cubic inches

Flateric · Post by **Flateric** » Sun Mar 10, 2013 6:32 pm

Has anyone considered replacing the two plastic tubes inside the hotend with carbon fibre? Seems like it might be worth a shot. It would never melt, acts as an excellent heat insulator. If something does melt to it it will not really stick at all. It's also self lubricating with filament, should be far harder to jam up.

Since my hotend is in two pieces I have been fiddling with it and I happen to have a piece of carbon fiber that is perfectly size to go into the tube and also has the exact size interior hole for my 1.75 filament.

Anyone tried this yet?

tom10122 · Post by **tom10122** » Sun Mar 10, 2013 8:40 pm

Are you talking just carbon fiber or carbon fiber with the resin?

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Hot end jams

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