Nozzle Continues to Clog  

RE: Nozzle Continues to Clog

Hi @treemeistah

I'm having a similar problem: got my mini+, it printed superbly for ~20h, then one print failed when one part lost adhesion roughly 1/4 of the way in and I came back to an unholy mess. Luckily the hot-end was only slightly mucked up so I could clean it quite quickly, but the following print developed the problem: towards the end of the print (1h 30 minutes) the extruder started making a loud clacking sound and no extrusion. I had to disassemble the extruder to remove the filament as it was so damaged it did not fit in the PTFE tube. Unclogged the nozzle, but then I had another clogging right away.

In another thread someone recommended checking that the hot-end PTFE tube is properly compressed using the procedure in this page: https://www.help.prusa3d.com/en/guide/how-to-change-a-heaterblock-heatbreak-mini_122769#_ga=2.27130173.1630013858.1620112452-178044355.1616250487 (from step 21). I will try it in the next couple of days and report back.

RE: Nozzle Continues to Clog

Today I've tried to properly re-seat the PTFE tube, as mentioned in my previous message. Afterwards I've printed one model that took almost 2 hours to complete and I had no clogging or under-extrusion problem whatsoever, so hopefully now everything is solved and my mini+ is back to performing very well 🙂 

One tip: Remove the lower fitting and the PTFE tube, and check if there is any residue in the nozzle and heat break. If there is, heat the nozzle to the extrusion temperature of your material. Once you reach the temperature "dip" the end of your filament in the plastic residue, making sure that there is good contact, then start cooling down the hot end and perform a sort of cold pull.

I hope this can help you as much as it helped me.

RE: Nozzle Continues to Clog

Posted by: @devcat

Today I've tried to properly re-seat the PTFE tube, as mentioned in my previous message. Afterwards I've printed one model that took almost 2 hours to complete and I had no clogging or under-extrusion problem whatsoever, so hopefully now everything is solved and my mini+ is back to performing very well 🙂 

One tip: Remove the lower fitting and the PTFE tube, and check if there is any residue in the nozzle and heat break. If there is, heat the nozzle to the extrusion temperature of your material. Once you reach the temperature "dip" the end of your filament in the plastic residue, making sure that there is good contact, then start cooling down the hot end and perform a sort of cold pull.

I hope this can help you as much as it helped me.

I've tried this and came to a conclusion that two possible fixes are likely.

1. If there is not a clog down in the heat break, replace the hot end PTFE tube with a new one, per the instructions. Removing it damages it more and it is not worth trying to reuse it. I feel the same about the grub screws. They easily strip and should just be replaced. I found them easily at a local source.

2. In my case, a piece of the PTFE tube broke off at the bottom and clogged up the heat break. I just could not get it cleaned out well. In addition, one too many spaghetti monsters baked plastic on my nozzle, heat block, heater and thermistor and I just could not get them apart without further damage. I'm just replacing the heat block, heat break, grub screws, nozzle, themistor and heater with new parts per the instructions and adding a silicone sock. It worked well for over a year and dozens of rolls of filament, but went to crap when a piece broke off the hot end PTFE tube. I'm maybe thinking that replacing the tube might be a scheduled maintenance item. I guess I will see if all the new parts get it back to proper operation.

When doing a cold pull, if you heat the nozzle up to a high temp and push the filament in manually from the top, you can tell if there is a clog by the pressure needed. In hindsight, I should have paid attention to that more.

Regards,

Mark

RE: Nozzle Continues to Clog

I had nozzle leak on my other printer (that was my fault - I didn't tightened heatbreak and nozzle the correct way). Melted plastic started to flow through the top of the heatblock and collecting under silicon sock. When I realized what is happening it was already a big mess, all heatblock was covered in melted filament. I turned on the printer, did cold pull to remove remaining filament, then heated the nozzle to 240C, removed silicon sock and using paper towels (be careful not to burn your hands) cleaned up the whole heatblock and silicon sock. While still hot I unscrewed the nozzle. Being careful I pulled heatbreak from the radiator, then again heated the block and unscrewed heatbreak and with paper towel cleaned the threaded part of the heatblock. Here the main idea is to do everything hot, as plastic will get into way and things will break.
Cleaning threads on nozzle and heatbreak was easy. Heated a bit with a lighter and using brass brush and paper towel cleaned the threads.
When assembling everything back, I had to heat the heatblock to 240C (it will soften the remains of plastic so it is easy to assemble everything), then fully screw in the nozzle and then released it half a turn. Then screwed in heatbreak till it met with nozzle. Added some thermal grease and inserted heatbreak into radiator, pushed to the end and fixed with grub screws. Then heated heatblock to 280C, tightened the nozzle and inserted PTFE tube while still hot.
Looks like a lot of work, but it took maybe few hours from a mess to printing. Being consistent and doing one thing at a time makes it easy.