Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
Hi
Printing white PETG I've had a blockage causing the printer to through the motions and thought it finished fine, but the top half of the job was missing.
The filament was jammed and unable to unload. I had to take the front off the nextruder to remove the filament and get the small pieces cleaned out. When I heat the nozzle I can get a needle up it a long way, and liquid plastic coats the needle, but I can't feed anything in to force that old filament through. The attached photo shows the filament is the full length of the nozzle, flush with the end. This is the standard 0.4 CHT nozzle that shipped on the Core One.
I was thinking of putting the nozzle in a vice and put a flame onto it to try to push this filament through manually, but wonder if the normally cold end is up to that heat? Or is this simply a lost case and just get another nozzle?
Very happy to hear other suggestions.
Cheers ! Geoff
White and pastel filaments are often tricky to print as they contain so much pigment that the melt can become a non-Newtonian fluid.
Open the extruder idler - you are going to feed directly to the print head ...
Heat the nozzle to at least 10° above the hottest printing filament you use.
Take 50cm or so of PLA and, by hand, push it down through the nozzle - it may take some force at first - if it does feed push the filament slowly at first then accelerate to as fast as it will go - finish by pulling the last few cm back out as fast as you can.
If it doesn't feed, you have a ruined nozzle.
Cheerio,
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
I have the exact same issue with some white PLA stuck in a .4 hardened nozzle. Simply won't budge.
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
Thanks @Diem - that's pretty much what I was trying last night and I couldn't get it to budge. The material in the hot end being so cooperative gave me hope I could maybe push some of the solid filament into the heat, but it's rock solid.
I've ordered a new nozzle, but since I have nothing to lose I will still try the idea of putting this in a vice and gently waving a butane flame over it to see if I can soften the blockage and nudge it further down with the blunt end of a 1.5mm drill bit. If whatever alloy the filament guide is made of doesn't survive the process, the whole thing was going in the recycling bin anyway so nothing lost 😀
White and pastel filaments are often tricky to print as they contain so much pigment that the melt can become a non-Newtonian fluid.
Thanks for confirming this. I wondered why I have challenges with white PETG I don't often see with the other colours, and wasn't shocked it was the white that played up this time. The datasheets don't show different settings so I'd thought it was all me!
Cheers, Geoff
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
I put the nozzle in a bench vise and heated it with a heat gun. I was able to push the PLA down through the nozzle with a 5/64" drill bit to clear the blockage, but it was not long enough to push the melted filament all the way through to the heating area, so it's still stuck. I thought about pushing the bit all the way down, but what if THAT gets stuck 😬 . I ended up ordering a 1.7mm nozzle clearing rod to finish the job. It's annoying but looks promising. My only concern is that the copper colored sleeve is now brass colored, presumably from the heat.
RE:
For my first update the result is promising. I was able to push the drill bit in the full length, and the jammed filament emerged as a goo from the nozzle. And the nozzle hasn't deformed visibly so there's progress. However, I only had a 1.5mm drill bit so it's cleared a tunnel that's not wide enough to push a filament into, with a coating of white PETG now on the inside of the filament guide.
If I can find a solid core wire with 1.75mm cross section and repeat the process I think I might get this restored, but that's where I've come unstuck. There's nothing I've found so far.
Alternatively, I'll be searching for a commonly available solvent that eats PETG for that next step.
Any thoughts on solid core 1.75mm wire/rod or a solvent? Any suggestions gratefully accepted.
Thanks, Geoff
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
I ended up ordering a 1.7mm nozzle clearing rod to finish the job.
I swear your reply wasn't there when I posted last. I'm keen to hear how you go with this.
I'm picking up a litre of Dichloromethane paint stripper tomorrow to soak my nozzle in. Will be good to compare results
I have always just pushed through fresh filament - once it has displaced the overcooked residue follow up with a cold pull.
Cheerio,
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
I have always just pushed through fresh filament - once it has displaced the overcooked residue follow up with a cold pull.
Cheerio,
Previously same, but somehow I leveled up with this blockage. The replacement nozzle is installed and printing fine now (took the opportunity to pull the gears out of the nextruder, clean them up and re-grease too).
PETG is supposed to dissolve in Dichloromethane so hopefully tomorrow I'll get the original nozzle back serviceable as a ready-spare.
If the filament is white you may have a sludge of pigment remaining, probably TiO2, it is a hard grained powder and will need to be removed to prevent further jamming.
Cheerio,
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
It's almost impossible to buy methylene chloride paint stripper here. Be careful with the stuff as it's been linked to heart failure and other things. Also, grease is essential for the Nextruder gears, but don't let even a trace get over to the filament area. These posts make me wary of heavily pigmented filaments!
RE:
Another update. The paint stripper is sold as liquid and says so on the tin, but my dream of just soaking the nozzle for an hour was dashed as what I bought is more of a gel with the consistency of clear slime. So I got to poke it down the tube (the thickest CNC Kitchen 1.4mm wire was fine for this), wait a while, then rinse with water while pulling out the degraded PETG pulp with the same wire. In between rinses I could measure the progress by the increasing distance a piece of PLA could feed in.
So this paint stripper is too thick to soak the nozzle in, and I wouldn't describe it as eating the PETG, but it took the solid mass lining the filament guide and turns it into a chunky goop that can be manually pulled out.
A few cycles of this process (rinse/repeat) and the PLA can be poked in to behind the start of the threaded section of the nozzle. Since that bit's heated, I think we're back in good shape, and later tonight when the printer's finished its present tasks I'll swap this nozzle on, give it a purge with some cleaning filament, and print the next queued job with it completing the test.
@Conrad you're totally right it's nasty. Much of the tin is covered in words explaining why it was a bad idea to buy it. It's definitely a job for eye and hand protection, where the gloves follow everything else contaminated into the bin when done.
Here's the product I used (link to Poly product page)
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
The nozzle is back working great, after a lengthy purge it's just passed 2 hours into a 6 hour PETG print. I do love it when a plan comes together.
Thanks everyone for your info, tips, and encouragement.
Cheers, Geoff
RE: Blocked nozzle somewhere above hot end - any tips for clearing, or just buy another?
It's almost impossible to buy methylene chloride paint stripper here. Be careful with the stuff as it's been linked to heart failure and other things. Also, grease is essential for the Nextruder gears, but don't let even a trace get over to the filament area. These posts make me wary of heavily pigmented filaments!
I have acetone, acetal acetate, methyl(ethyl) ketone MEK, and Dichloromethane/methylene chloride AKA "liquid cancer." Doing an article on vapor smoothing (if I survive it). Dichloromethane should be used either outdoors or under a fume hood and if outside with a respirator and PVA gloves (it will eat through nitrile and latex).