Problem with 3D printer

[bojan]

After more than 10 years of use, last couple of days I have a problem with my 3D printer head (MK8, 0.3 mm nozzle).
It seems the resistance to push the filament (ABS) through teflon tube of the hot end increased for some reason, and I at this time I can't figure our the reason for this..

It started with new filament reel, but even with old one the problem is here now.
I tried with higher temperature (250~260°C), but no results.
Then I put the new nozzle, new teflon tube.. no joy - it seems the filament gets stuck inside, so it is even not easy to pull it out, from either side when cold.

In the past, I had insulator wool around hot block, but stop using it as it was not doing much (then).

Did anybody have the similar problem and what was the solution?

[iborg (Philip)]

Hi Bojun


I would guess you have tried this, but, does the filament move freely through the tube when the tube is not connected?


Also, is the thermistor correct? If that is reading a higher than actual temperature, then it would be harder for the filament to go through the hot end.


Does the filament move through readily with no nozzle? Hot or cold?


Hopefully it doesn't take too long to solve.


Good luck


Philip

[bojan]

OK, problem is apparently solved, by using slower printing speed (40 instead of 60 mm/sec) and wider nozzle (0.4 mm instead of 0.35 mm).

the change applied is not too drastic, so I still don't know why then everything was OK with previous settings and for such a long time... maybe it was warmer in the room?

Anyway.. now the printing of motorized BM can continue... hopefully.

[bojan]

Hi Philip,

Thank you for the suggestions.
Yes, I checked most those and all was OK.

The resistance when pushing the filament through hot nozzle varied..


Anyway, it all work now, it seems - with new nozzle and slower speed.

[bojan]

Today, the problem is back.. not un-expected, because I didn't do anything really.
I found out that the resistance is happening inside teflon tube.
For some reason the plug is formed in the heat-break area (pictured), and that plug prevents the gear mechanism to push the filament towards the hot nozzle..

I just found the discussion about "heat creep", I suspected something like that, especially after finding that plug in the teflon tube..

Now, why this problem started to appear now? Some of the settings must be in the critical area, and slight variation of something else (environment temperature?) cause the whole process to go to the wrong (or right) direction..

[iborg (Philip)]

Hi Bojun


Glad you got it sorted.


Late last night I remembered I something similar happen with mine. The gear which drives the filament had partly filled with in with particles of filament, which reduced the grip. Cleaning the drive gear fixed that.


I really should replace it with a hobbed gear.



Philip

[bojan]

Well, not solved yet, still working on this..
Another article discusses the same issue:
https://help.prusa3d.com/article/ext...eat-creep_1948

I am now trying to improve the thermal contact between heat break and heatsink.. but the suspicion is still on filament (both reels ?? )