[Cerrado] Extruder stepper motor goes CLUNK, CLUNK and skips  

Re: Extruder stepper motor goes CLUNK, CLUNK and skips

The clunk noise could be the stepper motor skipping steps. It does snap back a bit when skipping.

Your questions:

1) Not sure if this cleaning filament helps much with partial blocked nozzles. I have some esun cleaning filament, but never got around to use it. To me, it sounds more like a gimmick, but I could be totally wrong. My preferred method for cleaning the nozzle is cold pulls. Supposedly cold pulls with nylon is even better. I usually use PLA for it.

2) calibrating e-steps. Well. I guess if you try to push more filament than it can handle this could cause skipped steps, but my gut (and there's alot of it) tells me, it'd have to be way off..

3) Not sure. If it doesn't get enough current, it will be more likely to skip.. but I am not sure if this is a typical sign of failure for these motors

Lets try some of the basics first.
We think it is skipping, so something is possibly causing too much resistance for the motor to advance more filament.

Some ideas:

Are you printing too fast?
- there's a limit of how much filament you can push thru any given nozzle. If you exceed this limit, you'll get skipped steps. If you're printing with big layer heights >0,25mm and nozzle temps on the cold side, this can become a limiting factor very quickly. Try printing slower or a bit hotter. I used to know the recommended limit for E3D V6 with a 0.4 nozzle, but I guess i am getting old...

Bad filament?
- some (usually cheap) filaments are inconsistent in diameter. If the filament gets much over 1.75mm, friction could be too high causing skipped steps. Use calipers to verify filament diameter a couple of times every now and then.

A partially clogged nozzle perhaps?
- Try a few cold pulls (there's gotta be a tutorial for that somewhere), if that doesn't work, try regular nozzle cleaning like poking it with the supplied acupuncture needle or taking it apart for a good clean.

Idler spring tension too high?
- If the idler springs are too tight, the filament gets squished flat and rubs against the side of the tube

Is the Hotend fan working correctly?
- If the hotend fan isn't cooling sufficiently, heat creeps up the heatbreak and the causes a (partial or complete) block.
(My hotend fan got increasing loud over time and seemed slow, i had to replace it and the problem was gone. Also something to watch out for when you swap fans for "more quiet" 3rd party fans. If they're not providing enough cooling, this will happen)

If this happens during prints with extreme retractions:
- alot of retractions can cause (partial) blockage in the heatbreak and or the filament being ground down (ok, no clunk there, just underextruding or not extruding at all). Trying to cut down on retractions, lower retraction settings might help. If its repeatablem try printing with retractions off to verify if it is related to retractions.

Deformed, frayed, blocked PTFE tube or tube not seated properly:
- that one is a pain to check cause you need to take whole extruder apart. But if there's something with the tube causing friction, you'll end up with an extruder skipping. The PTFE tube end needs to be cut precisly at an 90° angle and inserted all the way into the hotend and then locked in place with the black clip (i.e. push the tube down and hold it there while using the other hand to pull up the black clip. To remove: push the black clip down then try to pull the tube out)

If this happens right at loading filament:
- check alignment of drive gear to entrance of the ptfe tube and idler springs tension. I had a problem where my ptfe tube entrance was frayed and the filament got stuck there and never loaded properly. Had to use an exacto blade to smooth it out

Hope this helps a least a little

Re: Extruder stepper motor goes CLUNK, CLUNK and skips

Thanks, Stephan, for taking the time to write such a comprehensive list of items to check. Not only is this helpful to me right now, but it will also serve as a reference for others in the future.

I will check out your suggestions and then reply back once the mystery is solved.

Thanks!

- Brad

Re: Extruder stepper motor goes CLUNK, CLUNK and skips

Mystery solved.

It turns out that the nozzle was indeed clogged - and I am now a true believer in cleaning filament. We have been printing PLA, ABS, and Ninjatek Semi-Flex. When materials were switched, we just ran through the new stuff until the old stuff appeared to be gone. Apparently we left bits and pieces inside the print head that built up over time.

I ordered some eSun cleaning filament on Amazon. This filament has a very wide temperature range and feels kind of waxy. I believe it is supposed to be able to latch onto anything in the nozzle and clean it out.

To use it, simply heat the print head to hottest temperature used to print the last material. Then load the cleaning filament into the printer and keep extruding until it comes out clear. This should flush out most of the gunk that will fit out of the nozzle. Then let the print head cool down to just under 100 degrees. At this point the cleaning filament is solid inside the print head. Then set the print head temperature to something over 150 degrees. As the head heats up, release the tension on the pinch wheel and pull fairly aggressively on the filament. At about 139 degrees, the filament will come loose. You want to pull it out quickly (all at once) so that all of the cleaning filament comes out of the print head.

The first time we did this, we found bits of black inside the end of the removed cleaning filament even though the extruded filament appeared clear. A second time, we pulled out a bit more black specks. The third time, the filament was clear.

We then ran a print of Ninjatek Semi-Flex and the print was beautiful - just like when the printer was new! No more CLUNKs at all.

Later, we had some blockage in the print head. ABS wouldn't feed past a certain point even though the head was plenty hot. Likely the problem was just up from the hot end. Previously, I would have removed the cooling fan on the print head and let the heat creep up to melt the blockage. However, this time I simply loaded some cleaning filament. Since it goes soft at around 140 degrees, it fed just fine and cleared the blockage.

Hope this helps someone else.

Re: Extruder stepper motor goes CLUNK, CLUNK and skips

Glad you got it sorted.

And I guess I better give my esun cleaning filament shot as well. Didn't know you were supposed to do a "cold pull" at the end. Mine came with no instructions. Thanks for the follow up 🙂

Re: Extruder stepper motor goes CLUNK, CLUNK and skips

Hi Brad,

I'm experiencing similar problems. Did the skipping of the motor in your case happen immediately after you started printing, or later in the print? In my case, this happens after some time, sometimes even after 3 hours of flawlessly looking print.

Cheers,
Ivan

Re: Extruder stepper motor goes CLUNK, CLUNK and skips

Ivan,

After 1.5 years of 3D printing, every time we had this issue, it has been when there is something blocking the filament from feeding. I can't remember how often it used to happen, but it likely could have happened in the middle of a print. If the feeder is Clunk Clunking, then you have a pretty serious blockage.

Now, every time we change filament types (e.g. PLA > PETG), we clean with the eSun cleaning filament as described in the earlier post. Never had a problem since.

Note that the original post was on a MK2. We now have a MK3. If you have a MK3 with the geared feeders and it is clunking, then there really is a serious block. This has happened only once on our MK3 machine. The filament detector stopped a print automatically when the filament ran out. When we went to load the new filament, we got the Clunk Clunking and we found that the old filament was stuck in the tube below the feeder. We had to pull the tail of the old filament out with pliers before feeding the new filament. However, it was very cool that the print was saved even though the filament spool ran out mid-print.

Hope that this helps.

- Brad

Re: Extruder stepper motor goes CLUNK, CLUNK and skips

My two-week-old kit printer starting doing this clunking about four days ago. Having now disassembled the extruder assembly about four times, with lesser disassemblies added in, I think I have the printer back in operation. And I learned a lot about how the printer works. (Not that I have it all correct, just so you know.)

The plastic housing for the hot end assembly is attached by long bolts from the front. So when the extruder stepper shoves down on the filament, but the filament can't move, that housing is pried away from the part the stepper motor is attached to, and it makes a loud clunking noise when it snaps back up, when the extruder "gears" slip. So much for the noise, now for why the filament won't feed.

The obvious reason for a failure of the filament to feed properly is a plug somewhere down in the hot end. That Teflon tube in the top of the cooling fin part of the hot end assembly is supposed to extend all the way to the bottom of that assembly, either right up against the nozzle, or possibly up against a metal bottom with a small hole roughly the size of filament, but in any case close enough to the heat that plastic in that area will melt. If there is a gap between the Teflon tube and that metal part (or nozzle), then the end of the plastic filament will mushroom and the filament then cannot be pulled out - unless it has been melted. And pulling on it may break it off inside the hot end. My point here is that it is important that the Teflon tube be bottomed out in the hot end assembly.

Of course the nozzle should not be plugged. If clogged with PLA when PLA filament is loaded, there probably will not be a problem. The "plug" will melt and extrude out just fine. But if there is an ABS plug, it may not get soft enough, and then the PLA won't load properly. Clear enough, and probably obvious.

But that makes me think that the principal reason the cleaning filament recommended here works is because of the recommendation to set the temperature to that of the last-used filament. I suspect that most of the time one could switch from ABS directly to PLA with little trouble by first lying to the printer about the filament, and loading it as ABS. After the old filament has been purged, then it would be safe to set the temperature properly for PLA and get on with the printing. I do not say the cleaning stuff won't do any good, only that it probably isn't necessary. The "cold pull" may sometimes pull out a piece of broken-off filament, and if it does, then it was probably worth the cost. Or the cleaning filament may break off inside the hot end and further plug the thing.

Oh, I see where a similar reply to this has already been posted. Do as he said.