Print stopping with ground down (devil design) filament: Why?  

RE: Print stopping with ground down (devil design) filament: Why?

Something in the nozzle is plugging, or something in the hot end is jamming, or something is snagging the filament above the extruder (spool unable to turn freely).

A couple of cold pulls will clean the nozzle of any stray bits.

If a cold pull doesn't resolve the problem, then remove the nozzle and blow canned air through the hot end to dislodge any collected dust and debris from the heat break.

And you can always try printing with a bit higher nozzle temps with that specific filament.

RE: Print stopping with ground down (devil design) filament: Why?

Thank you for the tips!

The spool turns smoothly and I have done several cold pulls without anything unusual showing up at the end of the filament coming out of the nozzle.
I'll definitely try the canned air approach, though.

What baffles me is that this filament (both colours) ran perfectly for most of the spool this past month or two and is now starting to show problems, especially after quite some time (usually only after several hours into a print).

RE: Print stopping with ground down (devil design) filament: Why?

Hi,

a huge amount of retraction and a small layer height could also be a reason for grinding the filament.

RE: Print stopping with ground down (devil design) filament: Why?

That's a good tip. Thank you!

I'll lower the retraction and see what that does.  I was indeed printing at relatively low layer height (0.1mm)

RE: Print stopping with ground down (devil design) filament: Why?

Hello,

I had a similar issue, but with PLA. I am able to print relative small objects, but when the object has a large surface on the bed (e.g. 18x18 cm) at the first layer, during the slow infill, it slowly under extrudes and jams the filament into the heat break. The nozzle is unaffected. It has  just no filament.

The cause seems due to a combination of perfect situations:

• I have 30°C in the room.
• The bed is at 60°
• There is constant long uninterrupted pressure of the extruder over the filament (e.g. long infill line at reduced speed) without any retraction.
• The filament is at higher temperature that normal (it is the 1st layer)

then the temperature inside the heat break is enough to soft the PLA filament as a modelling wax, and the pressure, instead of pushing it in the nozzle direction, expands it laterally filling all the heat break channel (that is 2.2 mm), so that it creates a dummy piece of filament-end that instead of being 1.75mm has a diameter of 2.2 mm.

You should know that the E3D PRUSA version heat break, has not a constant inside diameter channel, but just in the middle, reduces its diameter from 2.2mm to 2.0.

Then it is alchemy ! Once that some environmental factors cool the soft PLA for a fraction of degrees to a level that it becomes crystalline again, the extruder can't extrude it any more through the 2.0 mm channel part that shrinks and reach the nozzle, and the filament jams into the heat break bottleneck. No PLA arrives to the nozzle any more. You need to stop the print, extract the filament, cut the final 5mm with the 2.2mm clog, and restart again.

I have attached a PDF I have done explaining this.

Let me know if this is also you issue.

Regards

RE: Print stopping with ground down (devil design) filament: Why?

You're a treasure, antimax. I haven't printed anything yet (still assembling the MK3, had to put it on the shelf the last week as had other work to do with existing Lulzbot). This sort of information is incredibly helpful to learn before I get the MK3 running.

Again thanks!

RE: Print stopping with ground down (devil design) filament: Why?

printing large flat surfaces means the printer is likely at max speed when doing so (layer>first), this can result in bad quality since it might print a little too fast for the filament to have time to melt.

this is why i always lower the Max volumentric speed from 15 to 11.5
this will reduce the top speed and hopefully allow filament a little more time to melt. there is a separate thread regarding max volumetric speed on this forum you may want to read.

i believe this is why i had white stripes when using my transparent pla filament to print a box, bottom part close to the middle (longest extrusion when doing bottom solid layers) of it had not melted properly.

RE: Print stopping with ground down (devil design) filament: Why?

Hi guys, I had similar problem with different PLA filament (3D Fillies). Basically what @wilko described. I eventually had to replace PTFE tube as the filament jammed inside. 

Originally I thought the nozzle is clogged. Tried cold pulls and everything around, until I end up with jammed filament in PTFE tube (before heatbreak). 

I do speculate, that the filament has some imperfections and due to E3D Prusa heatbreak not linear diameter it causes the filament to "snap" and jam. 

I experience this frustrating behaviour on printing simple triangle with gyroid infill (10cm a side). Other filament no problem with same print. I basically gave up on that specific filament brand as that happened with 3 different spools (silk, pla+, metalfill). 

Adding my experience here as it might help someone else in future.