Filament stuck / clogging  

RE: Filament stuck / clogging

Hi, if it occurs when you feed the filament into the extruder, ensure you feed with a straight filament (cut any curved end) and ensure your bondtech gears are alined together and alined with the PTFE tube.

If it occurs during printing, and seeing your picture, it could be a too low temperature, but you are used to print this PLA so it should not be the case. Then it could be a clogged/durty nozzle. You can check this in swaping to another one. If you do not have any other nozzle, you can try to clean with a cold pull, you will find how to in various sites, for example here or here.

RE: Filament stuck / clogging

Posted by: @andreas-orlyng

[...] Yesterday it happened again and the filament broke off just inside the PFTE tube so I had to disassemble the extruder and swap out the PFTE tube with a new one to get the filament out.

If this happens again, you may be able to avoid tearing down the extruder by doing the following:

Raise Z to max

1. Open the extruder door
2. Visually inspect the extruder gears and top of the PTFE tube to ensure you can't just grab any suck filament with needle-nose pliers or tweezers
3. Heat up the extruder well above print temp for the stuck filament
4. Use a 1.5x150mm rod (I like brass rods available at hobby stores) to push down through the top, past the Bondtech extruder gear and into the PTFE tubing. You may be able to push the filament down into the hotend where it will be extruded. In a pinch, you can try a small hex wrench though it may not have sufficient reach.

If you are unable to push the filament down through the PTFE tube, you can try the following additional steps:

1. Heat the nozzle to 285C.
2. Remove the nozzle.
3. Clear out the heater block to remove any remaining filament build-up (a coarse bit of stranded wire works well).
4. Grasping the rod with pliers, insert it slowly up through the heater block into the PTFE. If you meet resistance, maintain upward pressure and allow the brass rod to heat. With any luck, the blockage will pop loose and let you push the stuck filament up into the extruder where you can remove it.

I started a small print and after a couple of hours the filament got stuck again, this time I managed to get the filament out more or less undamaged, see attached picture.

Looking at the depth of the extruder gear marks, I suggest 2 things:

1. Before manually pulling filament out, open the extruder door. You don't want to put pressure on any parts, and pulling filament out can generate a bit of back current feeding into the controller. (You may see the panel light up if the gear is engaged when you pull.)
2. Loosen the extruder tension gear. You want it to grip the filament, but not so much that it is distorted. Distorted filament may jam and too much pressure can aggravate feed problems.

Consider the possibility of heat contributing to your problems. Be sure the ambient temp around the hotend is below 40C for optimum cooling efficiency. If using an enclosure, open the doors when printing PLA.

I have considered swapping out the nozzle, but it seems unlikely that its been damaged by a couple of months of use with PLA.

Keep a spare on hand, but you're more likely to see stringing with a damaged nozzle. Partial clogs are a possibility, but you're already doing cold pulls to address those.

Is the nozzle too close to the bed? I think I have managed to level the printer correctly but I am pretty new at this so the nozzle might be too close to the print bed?

Very possibly. Post a pic of your 1st layer results. I suggest using Jeff Jordan's "Life Adjust" procedure for optimal Live-Z calibration.

RE: Filament stuck / clogging

Posted by: @andreas-orlyng

Hi,

I have had my pre-assembled Prusa MK3S for a couple of months now and I have had no real issues, a couple of days ago the printer started making clicking sounds when trying to feed filament to the extruder. The first time this happened I cleaned it out with no major issues and resumed the print successfully. Yesterday it happened again and the filament broke off just inside the PFTE tube so I had to disassemble the extruder and swap out the PFTE tube with a new one to get the filament out. I am currently printing with Prusament PLA, Army Green and Gentlemens Gray and so far I have only been printing with PLA.

I started a small print and after a couple of hours the filament got stuck again, this time I managed to get the filament out more or less undamaged, see attached picture.

 

I presume the tearing is caused by me pulling out the filament, and the squashed bit is caused by the teeth of the extruder gearing grinding on the filament.

Any tips on what might be causing this?

I have considered swapping out the nozzle, but it seems unlikely that its been damaged by a couple of months of use with PLA.

Is the nozzle too close to the bed? I think I have managed to level the printer correctly but I am pretty new at this so the nozzle might be too close to the print bed?

if you print inside an enclosure and the temperature rises above 35 degrees Celsius, the PLA becomes soft and the gears cannot transport it properly. To clean the nozzle there are needles with different diameters to clean it (like this): https://filament2print.com/gb/spares-extras/853-nozzle-cleaning-needles.html

If a piece of filament is stuck in the hotend, you can try to remove it with this welding electrode: https://www.amazon.com/Welding-Tungsten-Electrodes-Thoriated-10-Pack/dp/B075BBC3LT

RE: Filament stuck / clogging

Hi,

Thanks for the replies, I have spent a couple of hours adjusting the z axis in increments of 5 and printing out test squares so I am pretty sure the layer height is ok.

I printed a couple of smaller 30 minute prints just fine, but when I ran a 4 hour print it clogged 3 hours in.

I have a replacement nozzle lying around so I will replace the nozzle to see if it helps. Is there any way of figuring out if the nozzle is damaged or should I just throw it away if the printer stops clogging with the new nozzle?

Best Regards,

Andreas

RE: Filament stuck / clogging

@andreas-orlyng

Hi Andreas, what is the ambient temperature in your printing room... 
my room is abour 25C at  the moment, I use generic PLA profile with 70C on the heatbed, 0.2mm layer height and o.4mm retractions, 
I can print for hours, 

If I increase the retractions to 0.8mm, I get blockages especially on items with lots of retractions!

If the ambient temperature gets to 35C I get occasional blockages even with short retractions

if I use lower layer heights I sometimes get blockages. 

If I turn the desk fan on, and point it art the printer, the blockages stop again... 

regards Joan

RE: Filament stuck / clogging

Hi,

The outside temperature is just below 30C, inside where the printer is located is probably around 22C, humidity is outside is ~30%. I did try with some additional cooling but I still got clogging after 1-2 hours.

So I decided to replace the nozzle, which was an adventure in of itself :). After I replaced the nozzle I calibrated the Z layer and did a couple of small prints with much better quality than I had before, currently the printer is 12 hours into a 40 hour print and it is still looking good.

It seems like the nozzle was the reason behind the clogs, at least I hope so :).

Thank you for the prompt responses and your assistance.

Best Regards,

Andreas

RE: Filament stuck / clogging

@andreas-orlyng

Good news Andreas

regards Joan