Repeated extruder clog issue  

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rpriegu
(@rpriegu)
Active Member

Hi, I'm having an extruder clog issue with my MK3s for the third time in a short period of time (60 printing hours) after printing around 2200 hours without even one clog.

Everything started when I eared the extruder motor missing steps and immediately stooped the print.

Heated the nozzle to 280C and tried to force the clog out manually but it didn't work.

Checked if the nozzle was cloged with a needle and I was able to insert the needle beyond the nozzle up to the heat brake.

FYI, nozzle is the original one (has never been removed, and it has the corresponding 0,5mm gap to the heater block.

I had to take out the PTFE that came with a piece of filament glued to it (the three times the same way).

Already cleaned the heatsink with canned air and the extruder fan is working without problem.

So my question is... what I'm missing that could be the cause of this?

Thanks and regards

Ramiro

Posted : 18/09/2020 4:56 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @rpriegu

[...] Everything started when I eared the extruder motor missing steps and immediately stooped the print.

First question to get out of the way: Are you printing in an enclosure or room with ambient temps approaching 40C/104F? High ambient temps can be problematic with low temp filaments like PLA due to loss of efficiency in cooling of the air cooled E3D V6 hotend.

Heated the nozzle to 280C and tried to force the clog out manually but it didn't work.

Checked if the nozzle was cloged with a needle and I was able to insert the needle beyond the nozzle up to the heat brake.

After a few similar experiences, I have abandoned the idea of using needles. They're tiny, prone to breaking, and will only move a clog around, not get rid of it. I would suggest reading up on and doing a few cold pulls. [Edit: Pic looks like you have done this, but worth confirming.] Done properly, a cold pull will pull any blockages out the top (with the big hole) and not try to force them through the small nozzle opening. This also avoids possibly damaging the nozzle with a metal needle which can cause stringing and other problems later.

FYI, nozzle is the original one (has never been removed, and it has the corresponding 0,5mm gap to the heater block.

Keep spares on hand. If nothing else, swapping in a known-good nozzle is a quick way to narrow the problem down.

I had to take out the PTFE that came with a piece of filament glued to it (the three times the same way).

After I've cleaned everything out, I like to open the extruder door and feed a 15cm X 1.5mm rod down through the top of the extruder, past the Bondtech gears, down the PTFE tubing, and into the hotend to verify there are no obstructions. This is a good opportunity to verify the idler gear in the door is properly seated and spins freely.

Already cleaned the heatsink with canned air and the extruder fan is working without problem.

So my question is... what I'm missing that could be the cause of this?

Have you switched from higher-temp filaments (e.g. PETG) to lower (e.g. PLA) recently? If so, do a cold pull whenever going from high-to-low in case any stray filament gets left behind and can't be melted out at lower print temperatures.

[Edit: Last thought. DO the jams occur at specific parts of your print (e.g. infill) where speed can come into play? Does slowing down help?]

This post was modified 1 month ago 2 times by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 18/09/2020 5:07 pm
rpriegu
(@rpriegu)
Active Member

@bobstro

Thank you for your feedback!!

Let me reply some of your questions to clarify the situation:

1- I'm not using any enclosure for the printer. I'm printing PLA in a room with a temp around 24C so I don't think high temp is an issue.

2- Yes, after the first two clogs I did a couple of cold pulls using PLA, it didn't came out dirty and I was able to get the inner form of the nozzle nicely. So I think if there was something there, I guess it was removed.

3- Checked the idler and it spins freely.

4- I have been printing PLA on this Printer for the last I'd say 1200 printing hours (before that I printed some Flex). So no mix of PetG and PLA here. Always the same PLA brand and in fact, last time was an almost new roll (I'd say it was at 90% full).

5- The clogs happened a different high of the print (I usually print many small objects, all the same). I haven't tried to slow down the printing.

 

I was thinking about to remove the heatsink and put some extra thermal paste on the heatbreak and check if everthing looks good on the heatbreak. I'm a little concerned about taking out the heatsink and not able to place it back in in a right way. :-/ :-/

What do you think about that?

 

 

Posted : 18/09/2020 6:39 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @rpriegu

[...] I was thinking about to remove the heatsink and put some extra thermal paste on the heatbreak and check if everthing looks good on the heatbreak. I'm a little concerned about taking out the heatsink and not able to place it back in in a right way. :-/ :-/

What do you think about that?

A bit of thermal paste at the TOP of the heartbreak is a good idea. There are also a lot of complaints about the Prusa heatbreak with the 2.2-2.0mm step. Ie never had an issue with mine over roughly 2 1/2 years. I did manage to strip out my heater block, so took that opportunity to do several small upgrades:

  • Replaced Prusa-fied heatbreak with E3D Titanium heatbreak without the step.
  • Applied Arctic thermal paste to the top of heatbreak.
  • Replaced the heater block with nickel-plated copper E3D heater block.
  • Applied Slice Engineering Boron-Nitride high-temp thermal paste to replacement heater cartridge and thermistor (originals were entombed in the original heater block).

I also use a silicone sock and plated/coated nozzles. This combination has been working very well for me for over 6 months now.

Not sure why yours only acted up after prolonged use, but if you're going to tear it down, might as well upgrade a few parts.

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 18/09/2020 7:25 pm
rpriegu
(@rpriegu)
Active Member

@bobstro

Thank You again for your suggestion. I'll take note and maybe in the future will make some of those upgrades.

Meanwhile will go ahead with the thermal paste and we'll see if that fix the problem.

Regards

 Ramiro

Posted : 18/09/2020 10:16 pm
charles.h13
(@charles-h13)
Famed Member

Ir nothing else works, try a cold pull and cleaner filament.  

Posted : 18/09/2020 11:19 pm
charles.h13
(@charles-h13)
Famed Member
Posted by: @charles-h13

Ir nothing else works, try a cold pull and cleaner filament.  

If not Ir

Posted : 18/09/2020 11:50 pm
rpriegu
(@rpriegu)
Active Member

@charles-h13

Thank you for your suggestion. Yes I did. First with PLA and later with some Nylon I was able to borrow.

I have now applied the thermal paste, cleaned the heatsink and done some cold pulls to clean up the nozzle.

So far is working fine.

Regards

Posted : 21/09/2020 4:04 pm
charles.h13
(@charles-h13)
Famed Member
Posted by: @rpriegu

@charles-h13

Thank you for your suggestion. Yes I did. First with PLA and later with some Nylon I was able to borrow.

I have now applied the thermal paste, cleaned the heatsink and done some cold pulls to clean up the nozzle.

So far is working fine.

Regards

Just so you know, I do not use cleaner filament the cold pull method.

 

Read this: https://rigid.ink/blogs/news/how-to-use-3d-printer-cleaning-filament

Posted : 21/09/2020 4:18 pm
rpriegu
(@rpriegu)
Active Member

OK, after like 12hs of printing, got the same problem again... 🙁 🙁 🙁

I haven't seen the extruder fan failing (and it shows OK in all the tests), so I think my options are...

to change: #1 the nozzle or #2 the heatbreak

Any other ideas regarding what could be causing this?

Regards

  Ramiro

 

Posted : 21/09/2020 6:31 pm
rpriegu
(@rpriegu)
Active Member

Could this problem be related to what is talked on this forum thread?

https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/replacing-the-heat-break/

Posted : 21/09/2020 9:02 pm
charles.h13
(@charles-h13)
Famed Member

@rpriegu

It must be.  I have had similar problems a few hours in.  I use the cleaning filament and it will help for few days or more and it might happen again.  

I am not sure if it is a jam.  I unload the filament, clean, and I will be ok for a few days to a week.  

I am not sure how dire it is.  

This post was modified 1 month ago by charles.h13
Posted : 21/09/2020 9:26 pm
charles.h13
(@charles-h13)
Famed Member
Posted by: @charles-h13
Posted by: @charles-h13

Ir nothing else works, try a cold pull and cleaner filament.  

If not Ir

This is the stuff I use.  

Posted : 21/09/2020 9:28 pm
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