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Filament twists and leaks out

Posted by rockstorm 
Filament twists and leaks out
March 09, 2016 11:16AM
Hi everyone!

The thing I've noticed is that when I tell the printer to extrude, say 20mm, the extruder motor will spin for a few seconds and stop when 20mm have been pulled in, but filament will keep flowing out from the nozzle for a while after the motor has stopped. This makes that after a while of printing, the filament will either leak out of the extruder or twist between the drive and the nozzle. Am I printing too hot? too cold? Maybe printing too fast or too slow? is the direct drive mechanism not aplying enough preassure?

The extruder is a E3D-Lite v6 mounted on a Prusa i3. I am printing 1.75mm PLA, the box in which the filament came says "Range of Printing Temp.: 220 - 240ºC" so I was printing at 230ºC (or so does Pronterface say).

Thanks a lot
Re: Filament twists and leaks out
March 09, 2016 12:21PM
maybe you are trying to extrude at a rate faster than 50mm/s.
Re: Filament twists and leaks out
March 09, 2016 12:26PM
Oh no, this happens when printing at 100mm/min, that's 1.67mm/sec, is it too slow? 100mm/min is the default configuration on Pronterface
Re: Filament twists and leaks out
March 09, 2016 12:27PM
That's normal, when the filament is pushed into the hotend a pressure will build up and the only escape is the nozzle. Therefor while printing you will set the retract to solve the oozing.

Edited 1 time(s). Last edit at 03/09/2016 12:28PM by Frans@France.
Re: Filament twists and leaks out
March 09, 2016 08:16PM
to hot for pla 220 unless in a special pla, pla should extrude between 180 -200

Check my rubbish blog for my prusa i3

up and running
Re: Filament twists and leaks out
March 11, 2016 11:57AM
I agree, for slow speeds the temp can be even under 180 with some filaments.
Mark the properties on every filament roll you have and keep it as a reference in a file too.
Start with (too) low temps and check the layer adhesion, if bad go up until you have strong parts but not higher.
Use this temp as the baseline - higher print speeds might require higher temps and slower speeds lower temps.
You will notice that with the right print temp the oozing will be far less compared to higher temps winking smiley

PLA loves to drop if too hot but in any case you check the retraction manually.
Extrude a few mm and then retract one mm, you can do in Pronterface or write some simple Gcode if you prefer.
The PLA that was extruded should drop off with the retraction.
If nothing changed wipe the nozzle and repeat with 2mm retraction.
On a bowden system you can start directly with 4 or 5mm.
Once you see the filament actually looks like it wants to stop after the retraction try these settings in a small testprint.
Try with a thin line width and print with single line walls, for example create a box with walls 0.33mm thick for a 0.3mm nozzle.
You should see small gaps where the retraction happens as before we set it quite high in manual mode, this is good winking smiley
Now you lower the retraction until it looks like the gap is just gone - note this value down.
Lower the retraction further until you think there is a small bump forming - note this value too.
Add the first value to the second and devide by 2 - you are now right in the sweet spot smiling smiley
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