Ultimaker 3 Dual Extrusion Stripping Filament

[Glensafro 1]

Hi everyone,

 

*** EDIT: For clarification the filament is only stripping when running a dual colour print. I've been able to run single colour prints from both nozzles without any issues using this filament. ***

 

I'm having issues with the drive gears stripping filament on a dual colour PLA print. It seems to happen at random - both nozzles will be printing fine for a couple of hours and then out of nowhere one or the other will start having massive underextrusion and the filament will look as slightly torn up over a 10-15cm span out of the drive gear housing, and then the fatal groove where the gear finally ate too much. I'm using a "glitter" filled PLA with the 0.4mm AA print cores at 200C and 70mm/s. Here's a list of things I've tried to save people time suggesting things I've already done:

 

- Changing the tension on the drive mechanism. I've tried it real tight, real loose and everywhere in between and the only thing affected is how much the filament gets chewed.

- Thoroughly cleaning out the drive mechanisms, including cleaning the gears down.

- Cold pull cycling the nozzles. I don't think the issue is clogged nozzles as filament extrudes freely without cleaning the nozzle out each time I have a problem, but I tried this anyway.

- Changing the standby temperature from 100C to 160C and a couple of stages in between.

- Changing retraction distance, limit and speed to try to limit the number of times the filament was run over the drive gear in the same place. Feel free to suggest any settings you know to work well for 2 colour prints as I'm not sure I've covered all the options on the retraction side of things!

 

If anyone has seen this before or has any new ideas that'd be extremely helpful, thanks in advance!

 

Glen

 

Edited July 5, 2019 by Glensafro
Clarifying dual extrusion is causing the issue.

[Enigma_M4 119]

Hi,

 

some markings on the filament after passing the feeders, like shown here: 

is ok and shows that spring pressure is set correctly. Tension indicator ad middle position is a good starting position.

 

Is it possible that your filament is blocked by some reason (for example tangled on the spool or similar)?

 

Greetings

 

[Glensafro 1]

Hi,

 

Many apologies for taking a long time to reply, we are a small company and I have to wear many hats in my role! So my filament looks similar to this when printing normally, with just the teeth marks, but more chewed up when a failure happens.The filaments I am using come on 1kg spools so I'm having to use a homemade spool holder as the UM3 holder won't accept 2 x 1kg rolls. I thought the spool holder wasn't the issue as the rolls rotate freely but maybe the feed of the the filament into the drive mechanisms is a tad too shallow and causing some extra resistance. I'm going to modify things to feed the filament in a little better and reply with my results.

 

Glen

Edited April 17, 2019 by Glensafro

[Matioupi 1]

I'm quite new to 3D printing, UM3 is my first printer. I noticed same behaviour, and here are my findings :

I solved it by changing the retractation parameters in CURA 4. I believe that the default settings are very strange with those default values (PLA) :

Minimum retractation travel : 0.7 mm
Maximum retractation count : 25

Minimum extrusion distance window : 1 mm

I found that this would cause a large number of retractations on some prints / print parts and that would cause grinding and / or under extrusion.

After changing those values to 2 mm / 20 / 4.5 mm solved my issue on a part that was repeatingly failing.

 

Something interesting in CURA would be capability to display the retractations in order to have a pre-print analysis on this (important) parameter

[Glensafro 1]

Hi all,

 

I've updated the title and original post to clarify that this only seems to happen when running dual colour prints. Single colour prints with the same filaments seem to be working fine. I have an update on the situation. I'm still having the same issues, but I noticed that when I remove the material from the printer following a failure the end which was in the hot-end is larger in diameter, up at 3.4mm from 2.85 as shown below. Could it be that the nozzle isn't getting back up to temperature quickly enough, causing a temporary clog until the filament is heated enough to pass through the extruder, then the backpressure on the filament is causing the filament to tear and then eventually strip? This would explain why I don't have to clean the nozzle out after failures, as the "clog" fixes itself when the nozzle hits temperature, but it creates just enough backpressure to cause the problem? Would this make sense or am I talking from my armpit?

 

 

[fbrc8-erin 272]

You usually see swelling like that when your front fan isn't running strongly enough (or at all). It can get tiny filament hairs wrapped around it that choke the fan motor. Have you cleaned the fan with tweezers recently?

https://ultimaker.com/en/resources/52501-check-for-residue-in-the-front-fan-of-the-print-head