Grinding Filament :(

[armstrom 0]

Well, it seems I too am plagued by the "grinding filament" problem. I thought I would take on a large detailed print (yoda scaled 1.5x sliced at 0.1mm and 20% infill). I was only about 8mm of Z height into the print and it started under-extruding. I tightened the thumb screw slightly and force the filament a bit to get it past the ground-out groove. Things went on ok for another few mm before it happened again. I started making small black marks on the filament just before it went into the extruder and watching them in the bowden tube. I saw it stop moving a second and third time when I finally just scrapped the print.

So, at the moment I'm unable to print unattended :(. I made sure the hobbed bolt was clean prior to starting the print (this is the v3 bolt). I don't think I have a plug in the hot end since this has happened a few times before and I'm able to just cut off the filament and print something else with no extrusion problems (a plug would require disassembling the hot end to clear it, right??)

My current working theory is that I'm having an issue with the bowden tube ID being slightly too small (may be perfectly within spec, I don't know) combined with filament that is JUST over 3.0mm (3.04mm in my case) in diameter. The raw filament moves easily through the tube if I push it by hand. However, I've noticed a few times where the filament has been very difficult to remove from the bowden. When I try to reinsert it I find it equally difficult to push through by hand. It seems the extruder is deforming the filament enough that it rubs the inside of the bowden tube. So, it seems my problem is a bit of a negative feedback loop. I start to grind the filament, so I tighten the screw which solves the issue for the moment, but the extra pressure deforms the filament more which increases the friction and causes the filament to grind again.. Ugh.. any suggestions?

I've heard of people changing to a different bowden tube with a 4mm ID and 6mm OD but I'm not sure what other modifications would be required for this to work. Gotta say, I'm a bit frustrated at this point. Other than the extruder problems the printer works well. But unless I can leave it to print unattended with confidence it's of limited usefulness.

Again, I'm open to suggestions. Thanks!

-Matt

[destroyer2012 0]

I think the easiest way for you to solve the problem is to email ultimaker and have them send you new filament that is smaller. The fact that they provide filament which is too big for their own bowden tubes is a defect, and it should be corrected by them. DO THAT BEFORE YOU TAKE ANYTHING APART or else fiddling might make things worse. If you do develop a plug you should read my post here viewtopic.php?p=5842#p5842

In the future you could try getting a bigger bowden tube although I suggest getting a PTFE tube that is 1/8" ID (3.125mm) as opposed to 4mm because with 4mm the plastic will flow backwards up the tube and cause plug-like symptoms. Or you could do what I did here viewtopic.php?f=6&t=995 which does involve a good deal more fiddling and in my opinion is not sufficiently tested (I've only printed one thing with this setup so far, but I've printed a lot of things with my 1/8"ID PTFE tube.)

Good luck! I'd recommend to draw a line on your bowden tube just so you could know if/when it starts moving upward.

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I know that it may seem a silly question, but for the sake of science ;-) : what is your step per E value? I imagine that with a V3 bolt you started with 865.88 as a default?

JP

[rewolff 0]

That will happen if you try to extrude too much plastic. Too much plastic can be printing at a high speed. So: How fast are you printing? How hot?

(I'm not that experienced yet...)

At the moment I like printing at 210, and 150mm/s is close to the extrusion limit at 0.2 mm layer height. Hmm. at 0.1 mm you have a factor of two margin there...

Maybe you're extruding too cold?

[armstrom 0]

I think the easiest way for you to solve the problem is to email ultimaker and have them send you new filament that is smaller. The fact that they provide filament which is too big for their own bowden tubes is a defect, and it should be corrected by them. DO THAT BEFORE YOU TAKE ANYTHING APART or else fiddling might make things worse. If you do develop a plug you should read my post here viewtopic.php?p=5842#p5842

In the future you could try getting a bigger bowden tube although I suggest getting a PTFE tube that is 1/8" ID (3.125mm) as opposed to 4mm because with 4mm the plastic will flow backwards up the tube and cause plug-like symptoms. Or you could do what I did here viewtopic.php?f=6&t=995 which does involve a good deal more fiddling and in my opinion is not sufficiently tested (I've only printed one thing with this setup so far, but I've printed a lot of things with my 1/8"ID PTFE tube.)

Good luck! I'd recommend to draw a line on your bowden tube just so you could know if/when it starts moving upward.

This is not the filament that came with the ultimaker kit. That filament is all well under 3mm and I have not yet had any major issues stripping that. However I have had other issues with that filament since it varies so much in diameter. This is very high quality filament with a nominal diameter of 3.00mm and a tolerance of +/- 0.05mm. I have not observed any diameters (I measure before each print) outside of this tolerance. I think the problem is that the ultimaker is supposed to work with 3mm filament but the reality is that the 1/8" ID bowden tube (3.175mm) is not large enough to accomodate filament that has been deformed by the hobbed bolt. As long as the nominal diameter of the filament is significantly less than 3mm it is probably fine. Unfortunately I bought two kilos of this 3mm PLA. I have not yet opened the other package so perhaps it is on the lower end of the tolerance range but I'm not sure that will be enough. In reality I need some filament closer to 2.85mm like the stuff shipped with the kit. :( OR I need a bigger bowden tube.

-Matt

[armstrom 0]

That will happen if you try to extrude too much plastic. Too much plastic can be printing at a high speed. So: How fast are you printing? How hot?

(I'm not that experienced yet...)

At the moment I like printing at 210, and 150mm/s is close to the extrusion limit at 0.2 mm layer height. Hmm. at 0.1 mm you have a factor of two margin there...

Maybe you're extruding too cold?

I'm printing at 225 degrees and only 50mm/s (to start, I typically crank up to 150% speed after it seems things are going well.. but even that is only 75mm/s. This is what I normally do with 0.2mm layer heights. I did the same last night when trying to print at 0.1mm but that was my only (failed) attempt at that layer height.

-Matt

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"this Will happen if you try to extrude too much plastic"... Too much plastic can also be caused by incorrect steps per E value...

What is your Step per E value? Did you calibrate it (using Cura wizard for instance)?

I had the same issue because my steps per E was to high...

JP