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E3D UMO+ under-extrusion problems

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Hi folks,

I encounter a lot of under-extrusion on one of my UMOs and I can't seem to find the fix. This machine is upgraded with an E3D v6 (0.4mm nozzle) where I've made a special mount for. The fact that I upgraded to a E3D was because of under-extrusion with the original hotend in the first place. I thought that it was the teflon coupler because I print a lot of ABS and colorfabb XT in the >235ºC range. After changing the teflon coupler it seems to work fine for a short while but the problems started to occur again, so I decided to switch to E3D.

I'm using the original heater block of the Ultimaker itself on the E3D because it fits well, and I didn't have to change stuff in the firmware, which I never did by the way.

Apparently the E3D upgrade didn't fix the issue. When I'm printing Formfutura ABS, I have to turn up the temperature to 255-260ºC to get good extrusion (@4,8 mm3/s).

Printing Colorfabb XT is even worse. I'm printing at 260 and it still is not printing very well. I mean, the layers are laid down kinda okay, but the infill lines do not touch each other, as you can see in the pic below. When I slow down the print speed to 75%-50% of 60mm/s, the lines start to touch each other and it starts to form a smooth layer. But it is really slow and it doesn't have to be that slow, not at those temperatures anyway.

What I tried already:

• Tighten the feeder mechanism, didn't work.

• Loosen the feeder mechanism, didn't work.

• Turn of the cooling fans, didn't work

• Feeding material without the nozzle at 250ºC, which works pretty smooth.

• Bowden tube doesn't have any noticeable friction.

So, somehow it feels like the nozzle has a lot of friction. A problem I was thinking about is a possible temperature flaw, like it displays a higher temperature than it actually is, or something. Temperature is very constant though. Oh, and PLA printing is not possible without the 'oil on filament' technique.

Anyone has suggestions? :)

5a3317a4b11e2_Foto03-02-16152518.thumb.jpg.0f9d19e3febdcd1cca9f178041f21446.jpg

5a3317a4b11e2_Foto03-02-16152518.thumb.jpg.0f9d19e3febdcd1cca9f178041f21446.jpg

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Why do you think the nozzle has a lot of friction?

Could you also upload some pictures of your feeder?

Have you checked if none of the internal parts of the feeder show any signs of wear?

Could you also upload a close up picture of your knurled wheel?

- is it clean?

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Well I obviously do not know for sure if it has a lot of friction, but the theory I came up with is because of the fact I torch out the nozzle when it gets clogged.

This torching gives the nozzle a dull look, because of oxides formed in the process. This oxide layer has a slightly rough feeling to the touch and I can imagine that materials have more friction to this surface compared to the bare brass metal.

This is just a theory, and I can't really come up with something to test this properly.

As you can see in the pics below. The knurled bolt is clean, and bearing (instead of the POM wheel) pushes the filament against the knurled bolt very well.

When I try to pull the filament out while rotating the extruder gear, I need quite a lot of force to let the filament slip.

5a3317d4e4212_Foto07-02-16125802.thumb.jpg.62f58b6d1f3d568039fd416d2606319e.jpg

5a3317d536086_Foto07-02-16130019.thumb.jpg.0e43fd0a771726957d20e4f63c610c2f.jpg

5a3317d4e4212_Foto07-02-16125802.thumb.jpg.62f58b6d1f3d568039fd416d2606319e.jpg

5a3317d536086_Foto07-02-16130019.thumb.jpg.0e43fd0a771726957d20e4f63c610c2f.jpg

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Not sure if the picture is playing tricks but on your drive bolt it looks like the bottom half has pointy teeth and the upper half has flat teeth?

Seeing if you can pull out the filament by hand is a good test and your theory also sounds plausible.

Do you have a spare, new nozzle? Only swapping the nozzle could be a good test to check your theory.

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Yeah, maybe I have to design a better one. I also have a Lulzbot Taz5 which I developed a better extruder for with a drivegear that has extreme grip on the filament. Is also is able to handle flexible filaments like ninjaflex without it tangling around de drivegear.

Maybe I'll just flip the design, add some hooks like the ultimaker extruder has, and try that design out. If only I had more time...

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Use the Knurled Bolt of this design: http://www.thingiverse.com/thing:15897

With this design: https://www.youmagine.com/designs/modified-geo-hangen-ultimaker-extruder-by-antiklesys--2

And I suggest buying one of these to use with it: http://e3d-online.com/Mechanical/Bowden/Bowden-Adaptor-3mm-Filament

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