Filament clogged in hotend
So, first clogged filament. ABS.
When changing filaments during color print, my extruder started to grind trough filament. I unloaded the filament, trimmed it and tried re-load - no success. It seems to be solidified somewhere above heatbreak; i can insert up to 74mm of filament onto extruder by hand and it hits solid block. If my measurements are correct, I have solid filament ~11mm above heatbreak and I am unable to push it trough.
I tried acupuncture needle and it goes in 33mm in (from tip of the nozzle) - hitting resistance somewhere around last 2-3mm. It is actually penetrating the block, as if I heat up nozzle to ABS printing temp and force it trough (it goes trough if it's hot enough), i can push it out a bit with filament inserted from top.
At this point I have some ideas, but they seem risky. I could remove hotend fan, allowing heat to creep up the cold end and try to push block trough. I could try to disassemble the hotend and soak it in acetone (ABS should dissolve), or manually clean it. Cold pull technique seems out of the question, as my block is not melted.
Please advise. TIA.
Re: Filament clogged in hotend
I could remove hotend fan, allowing heat to creep up the cold end and try to push block trough. I could try to disassemble the hotend and soak it in acetone (ABS should dissolve), or manually clean it.
That's exactly what I would do. Try the heat creep first and if that fails, go and disassemble the hotend.
Re: Filament clogged in hotend
That's exactly what I would do. Try the heat creep first and if that fails, go and disassemble the hotend.
Do you have recommendations for temperature and time of time creep approach?
I tried up to 235'C/10 mins, with locked fan. I felt any longer would risk damaging ABS printed hotend housing. Yet I might be wrong here, no real experience. Thermal imaging shown that radiator fins around jam were at ~70'C at this point (this is inaccurate, as they are way to shiny for thermal imaging).
Re: Filament clogged in hotend
I usually even go to 250°C, but it's not that significant. ABS should not soften till 90-100°C. (Most sites state around 105°C glass transition temperature) That's a bit of a catch-22 here, if the clog sits that high up in the cold zone the housing might actually get warmer than the clog.
I am thinking maybe hot allen key?
Re: Filament clogged in hotend
I have (hopefully) fixed the issue. Doing a test benchy now, it should show any deviations.
Since heat creep didn't help me, I'm sharing technique used that did work. Tools requires: syringe with needle, some ABS filament, some PLA flament, compressed air in can, acetone.
Procedure I used:
1. Hot-end fully assembled, sans idler door. Cold. Powered on (to have z-steppers powered).
2. Put ~0.05ml of acetone, via needle, to the top of PTFE tube.
3. Quickly blow excess acetone and all drips with compressed air.
4. Plug top of PTFE with PLA. If any acetone leaks out, blow it away.
5. Wait ~10-15 minutes.
6. Check with PLA that clog is softer; blow away any acetone that gets out. Remove PLA.
7. Insert ABS and heat nozzle to 255'C. Push gently with hands.
8. Clog should move to melt zone and... well, melt and extrude.
9. Extrude some filament by hand to clean us acetone remainders.
10. Do "cold pulls" to clean up rest of residues.
Key point - acetone helped to loosen up the plug enough, that I was able to push it into melt zone.