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[Solved] Leaves thick strings and lumps during printing

Posted: Mon Jan 07, 2019 4:27 am
by davorin
Good morning (o;

I just installed a new roll of PLA to my Ender-3 printer...

It starts printing very nicely....but from time to time a clog comes out of the nozzle like the attached picture...
It's not that it is stringing all the time.....and some PLA material gets collected on the it seems...

Do I need to reduce the "Extrusion Multiplier" ?

Re: Leaves thick strings and lumps during printing

Posted: Mon Jan 07, 2019 10:06 am
by davorin
Seems I have found the source.....before I ran some tests with Wood filled PLA....which caused the nozzle to totally clog up....

I cleaned out the heater element and the nozzle....but seems I could not fit it tightly back to the heater....
Between the heater and the heatsink it was filled with PLA....yellow and dark....so somehow the PLA escaped not only from the bottom of the nozzle.

The print itself was perfect except for all the dirty PLA thrown onto the surface....


Just dunno where it actually escaped and got pulled up between heating element and heatsink...

Re: Leaves thick strings and lumps during printing

Posted: Mon Jan 07, 2019 11:23 am
by dkightley
I think you got off light there!!

I had a leak from the nozzle thread once when I set a print off ….and went out! for the day. When I got back, I had a lovely shiny golfball sized blob encasing my extruder. I killed the thermocouple in the process of removing the damn thing!...cost me a 2 week wait and the cost of a t/c!!

Re: Leaves thick strings and lumps during printing

Posted: Mon Jan 07, 2019 12:32 pm
by davorin
Well I hope PLA was running out of the nozzle screw....can't imagine where else...
What puzzles me is the fact how the excess PLA moved all the way up to the heatsink....

The new painlss steel nozzles should arrive by Friday....0.4mm and 0.6mm....maybe I split the nozzle sizes on two Ender 3 machines....as I just love the build quality for that price.....used to have a Velleman K8400...hours to assemble....difficult to adjust and terrible hard time to get the first layer right...

Re: Leaves thick strings and lumps during printing

Posted: Sun Jan 13, 2019 6:57 am
by davorin
Replaced the nozzle now....had one spare...and the ones I ordered where M6 instead of MK10 (o;

Looks somehow the PLA runs out above the heater......just dunno why...never touched the upper part....and the nozzle I screwed in very tight.

Re: Leaves thick strings and lumps during printing

Posted: Sun Jan 13, 2019 7:44 am
by blackbird2016
davorin wrote:
Sun Jan 13, 2019 6:57 am
never touched the upper part....and the nozzle I screwed in very tight.
Do not tighten the nozzle in the block!
The nozzle needs to be tightened against the heat sink!

Re: Leaves thick strings and lumps during printing

Posted: Sun Jan 13, 2019 2:05 pm
by davorin
Hmm...what you mean by that? The thread for the nozzle is in the heating block....

Guess I have to rip all apart or get me a new head....though can't seem to find one on ebay...

Re: Leaves thick strings and lumps during printing

Posted: Sun Jan 13, 2019 3:09 pm
by dkightley
Try Amazon...

Re: Leaves thick strings and lumps during printing

Posted: Sun Jan 13, 2019 3:17 pm
by greybeard
In general, this is how most hot-ends are assembled…

Starting with Un-assembled condition with clean parts (removed filament, goop…):

Heat the hot-end (I usually use the filament pre-heat feature on my printers. If not on the printer, use a small torch/etc). Don’t need to fully heat it, just enough to expand metal. About 150C.

Screw the nozzle into the heat-block, leaving a gap the thickness of a sheet of paper (~0.1mm/0.004inch - the thickness of a human hair). Very-Light-Finger-tight will provide this ‘hardly noticeable’ gap.

Screw the hot-end’s heat-tube into the heat-block until it meets up with the nozzle. Snug it up but, DON’T tighten it (can break the tube - it’s thin walled).

Now, tighten the nozzle to remove the gap thus, it will press tightly against the heat-tube. Don’t over-tighten - the thread section on nozzle can break off!

Pre-heat as usual and re-snug (by hand) the tube section.
Re-tighten the nozzle.

In above condition, no plastic can ooze out from between Nozzle and Tube, thus, no plastic to leak out of the interface between nozzle and/or top of block.

IMPORTANT:

Know your hot-end’s construction: some have PTFE in the heat-tube, some have PEEK, some have full metal (stainless steel…). Depends on brand and purpose.
I have 6 different hot-ends and some came in kits with interchangeable parts for different filaments…

The Key-to-success: Ensure the tube (PTFE, PEEK, Metal) fully butts up against the nozzle inside the block.

Re: Leaves thick strings and lumps during printing

Posted: Tue Jan 15, 2019 3:28 am
by davorin
Took now the print head apart....removed all PLA.....cut off a little of the PTFE tube end...and put everything back together....

After a longer test print (7 hours) the print head still looks clean ;-)
So back to normal :-)


Thanks for the suggestions...