RE: Best way to completely dissolve PETG from nozzles?
@vintagepc
Same for the paint stripper.
Reporting back: It's making progress. Instead of dissolving the PETG, it seems to make it flake off. I've renewed the solvent bath, and this time I'll cover it to retain more of its stripping goodness.
RE: Best way to completely dissolve PETG from nozzles?
It turns out the paint stripper is ultimately a fail. It did more than the others, but there's still residual PETG that's clinging to the nozzle and not coming off.
The THF obviously isn't worth the price for just a single nozzle, but if it works great I suppose it could more than pay for itself by periodically doing a thorough cleaning of nozzles and hotends.
The same person on the chemistry stack exchange who spoke highly of THF also spoke highly of simply vaporizing the PETG off the nozzle with a blow torch. That would have the virtue of being fast....
RE: Best way to completely dissolve PETG from nozzles?
I've don't the propane torch method in the past, it works well, hold the nozzle with long forceps and put it in the blue part of the flame, stop if it starts to get red hot. Then you've got to clean the carbon off but that usually takes only a little scrubbing.
FYI: It has been years since I've had to do it, and not since getting printers with E3D V6 hot ends so I've never put a torch to the V6 nozzles, but they aren't that different from the brass nozzles I used to have to clean out on some of my older printers (burnt PLA inside was a problem with them).
Also only do it on the brass nozzle, a torch will melt the aluminum parts of the hot end.
RE: Best way to completely dissolve PETG from nozzles?
It turns out the paint stripper is ultimately a fail. It did more than the others, but there's still residual PETG that's clinging to the nozzle and not coming off.
The THF obviously isn't worth the price for just a single nozzle, but if it works great I suppose it could more than pay for itself by periodically doing a thorough cleaning of nozzles and hotends.
The same person on the chemistry stack exchange who spoke highly of THF also spoke highly of simply vaporizing the PETG off the nozzle with a blow torch. That would have the virtue of being fast....
Reporting back with a revision: after letting it sit for a day or so, I transferred the E3D-V6 nozzle to a fresh bath of the paint stripper, and in doing so about 80+% of the PETG flakked off when it was hit with the force of the stream of new paint stripper (the paint stripper I'm using comes in a spray can). So, as long as it's making progress, I'll keep at it. Although a slow process, it requires only very time or little effort from me, as I'm letting the chemicals do all the hard work.
Part of the reason to press-on is what @martys mentioned: things like the hot-end, which might be made from either aluminum or copper, might also benefit from a good cleaning now and then. In addition, I'm unsure how brass nozzles with coatings (like the matchless nozzles) would respond to a blowtorch.
RE: Best way to completely dissolve PETG from nozzles?
With a brass nozzle, by the time you've paid for all these dodgy chemicals, would it not have been both faster and cheaper to just buy a new nozzle?
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RE: Best way to completely dissolve PETG from nozzles?
If you are worried about overheating you could put the metal parts in your kitchen oven at max temperature for a few hours, most household ovens have a maximum temp of 525°F or 273°C. The wiring probably wouldn't like those temps, or the holder for the PFTE tube, so only the metal parts would go in the oven.
I would be wary of using paint stripper on aluminum, if it happens to be a strong base it will corrode aluminum. Acid will eat the brass and steel parts but won't touch the aluminum, base will eat the aluminum and leave the brass and steel alone.
THF is nasty stuff to work with, smells terrible, has health risks, and it can oxidize to form explosive peroxides. So not something you want to leave sitting around for years.
RE: Best way to completely dissolve PETG from nozzles?
If you are worried about overheating you could put the metal parts in your kitchen oven at max temperature for a few hours, most household ovens have a maximum temp of 525°F or 273°C. The wiring probably wouldn't like those temps, or the holder for the PFTE tube, so only the metal parts would go in the oven.
I would be wary of using paint stripper on aluminum, if it happens to be a strong base it will corrode aluminum. Acid will eat the brass and steel parts but won't touch the aluminum, base will eat the aluminum and leave the brass and steel alone.
THF is nasty stuff to work with, smells terrible, has health risks, and it can oxidize to form explosive peroxides. So not something you want to leave sitting around for years.
Good to know. The amazon stuff says it contains BHT in it to stabilize against peroxides, presumably for the reason you gave. I don't know enough chemistry to evaluate that claim or how effective/ineffective BHT might be in mitigating against it. As you say, probably not a good choice for me.
What exactly would happen to the PETG if it were put in an oven at those temps? Would it melt off and flow away, vaporize, char into ash, or...?
RE: Best way to completely dissolve PETG from nozzles?
@chocki
I can't really answer that for myself just yet, but I imagine it really just depends on your situation. For some people, like apartment dwellers, yes, that might be a better solution. At the other extreme, the incremental cost is very low if you're a home owner and the solvent turns out to be something you have on-hand anyway or can also use productively for other things.
RE: Best way to completely dissolve PETG from nozzles?
What's particularly frustrating is that much of the public data on the chemical resistance of PETG is contradictory. For instance, this chart: https://www.kendrion.com/fileadmin/user_upload/Downloads/Datasheets_Operating_instructions/Valves_Fluid_Control/Chemical-resistance-valve-technology-Kendrion-EN.pdf
implies that PETG is not resistant to MEK, but is highly resistant to Toluene, but this other chart: https://media.suweb.site/2016/04/chemical_compatibility_for_nalgene_containers.pdf
says exactly the opposite. And so it goes with other charts also, with some saying that PETG is chemically resistant to acetone (which, from my testing seems to be true), whereas other chemical resistance charts say it's not. When I posted the OP, I thought this would be a settled matter with trustworthy answers, not requiring new R&D to test their veracity.
RE: Best way to completely dissolve PETG from nozzles?
What exactly would happen to the PETG if it were put in an oven at those temps? Would it melt off and flow away, vaporize, char into ash, or...?
Stabilizers just buy you extra storage time, they oxidize first, so how long they last depends on the storage conditions. The thing about peroxides is that they are fairly harmless in solution, but when the solvent dries out leaving the peroxide behind they turn explosive, this normally happens in the threads of the cap, where I work when we had to dispose of some old bottles of solvents that form bad peroxides we had to hire someone and they set up a remote station that unscrewed the cap in a box outside about 20 feet away from the disposal guy. I don't remember ever needing that level of precaution with THF but even a small "pop" while unscrewing the cap could cause a fire.
PETG goes fairly liquid above 250°C, so it should flow away, should get the parts clean enough to reassemble. They are just going to get covered in plastic again anyway so you don't need them super clean... 😀
RE: Best way to completely dissolve PETG from nozzles?
OK, I think on a going-forward basis I have maybe found the right answer for me. As long as the chrome coating on the matchless nozzles is at least 0.001 inch thick (cf: https://www.electro-coatings.com/hard-chrome-hardness-value.php), it will have a hardness much harder than brass. In this case, brushing the nozzle with a brass brush (as suggested by swisscheese earlier in this thread) should pose no risk, and one could even add an automatic nozzle wiper to brush off PETG at the end of every print, similar to what this guy has done on his Ender:
😀
RE: Best way to completely dissolve PETG from nozzles?
What exactly would happen to the PETG if it were put in an oven at those temps? Would it melt off and flow away, vaporize, char into ash, or...?
Stabilizers just buy you extra storage time, they oxidize first, so how long they last depends on the storage conditions. The thing about peroxides is that they are fairly harmless in solution, but when the solvent dries out leaving the peroxide behind they turn explosive, this normally happens in the threads of the cap, where I work when we had to dispose of some old bottles of solvents that form bad peroxides we had to hire someone and they set up a remote station that unscrewed the cap in a box outside about 20 feet away from the disposal guy. I don't remember ever needing that level of precaution with THF but even a small "pop" while unscrewing the cap could cause a fire.
PETG goes fairly liquid above 250°C, so it should flow away, should get the parts clean enough to reassemble. They are just going to get covered in plastic again anyway so you don't need them super clean... 😀
In that case, no need to even disassemble: just increases the hotend to 250C+ while the nozzle is still installed. Then I guess all the PETG should just drip off, except maybe whatever might be caught between the threads.
RE: Best way to completely dissolve PETG from nozzles?
One last thing that I'll memorialize: here's a link to the best analysis I've so far found regarding the efficacy of different solvents relevant to 3D printing and their relative safety: https://www.reddit.com/r/3Dprinting/comments/4f52hm/more_chemical_solvent_choices_to_consider_for_pla/
The TL;DR is that safety is pretty much inversely related to efficacy. He ranks Methylene chloride as the most efficacious, but Methylene chloride is getting much harder to find these days due to earlier actions by the EPA to remove it from the market (which, since then, have been put on hold). The spray-on paint stripper that I'm using still contains some amount of it, which is maybe why it's the only solvent I've tried that shows any results. Maybe it's been heavily diluted though, which might explain why it's so slow. Hard to say, because most MSDS for these types of products typically show a wide range for what percentage of different chemicals might be in the product. That unfortunately may also mean that the contents of one batch might vary quite a bit from the next, so even if it works well the first time you try it, it may not work so well the next time you buy it, because the wide ranges provide cover for the formulation to vary.
RE: Best way to completely dissolve PETG from nozzles?
I'm sticking with cold pulls since it physically pulls stuff out of the nozzle. Early on I had one of those stupid "cleaning needles" snap off inside. I've had odd stuff get on the filament while feeding without a filter. I've even had filament with bits of crud insdie. Something that melts filament might not help if the blockage is caused by something else that might not even melt out at high temperatures.
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RE: Best way to completely dissolve PETG from nozzles?
I'm sticking with cold pulls since it physically pulls stuff out of the nozzle. Early on I had one of those stupid "cleaning needles" snap off inside. I've had odd stuff get on the filament while feeding without a filter. I've even had filament with bits of crud insdie. Something that melts filament might not help if the blockage is caused by something else that might not even melt out at high temperatures.
Makes sense to me, as solvents seem even less active when it comes to cleaning the inside of the nozzle.
How are you keeping the outside of your nozzle clean? If I do nothing, I find that eventually there will accumulate enough buildup that it may interfere with the print. What I recently started to do, and which has helped a lot, is run "End g-code" after a print which heats up the hotend to 250C for 3 minutes, so that PETG in the hotend completely drains out and doesn't become drool at the start of the next print:
G4 ; wait
M140 S0 ; turn off heatbed
M104 S250; set extruder temp to 250C so hotend filament will ooze out (so it won't get in the way at the start of the next print)
{if layer_z < max_print_height}G1 Z{z_offset+max(layer_z+1, max_print_height-80)}{endif} ; Move print head up to make nozzle access easier
G1 X150 Y200 F3000 ; move X axis toward the center in case I later need to unload the filament
G4 S180; wait 3 minutes for the filament to ooze out.
M221 S100 ; reset flow
M900 K0 ; reset LA
{if print_settings_id=~/.*(DETAIL @MK3|QUALITY @MK3|@0.25 nozzle MK3).*/}M907 E538 ; reset extruder motor current{endif}
M104 S0 ; turn off temperature
G4 S300; wait 5 minutes before turning off fan
M107 ; turn off fan
M84 ; disable motors
RE: Best way to completely dissolve PETG from nozzles?
As my garage has gotten colder due to the shift into winter, the paint stripper reaction has largely stopped. This is consistent with what I've learned from reviewing the various charts on PETG chemical resistance: temperature is often an important factor in driving the reaction, with higher temperatures rendering PETG less resistant to chemical attack.
So, based on observations to date, I have a new hypothesis as to what I think will likely work:
1. put the nozzle in a test-tube or similar small chemical-proof container, add enough paint stripper to cover the nozzle, and then add a press-fit cap/lid. The purpose of the that last step is (1) to keep the vapors in but also (2) act as a safety pressure relief so that, in a worst case scenario where the vapors ignite, the lid would pop off like a cork from a pop gun toy and thereby avert a more forceful explosion. i.e. the lid should fit tight, but not too tight--perhaps about the tightness of the lid on a tin of Danish cookies or the tightness of an old-school, screwless plastic snap-cap like the kind often used on pill bottles back in the day before "child proof" lids were a thing.
2. Suspend (but do not completely submerge) that assembly in a heated ultrasonic water bath.
If my guess is right, that should cavitate off any remaining PETG and would likely also be effective at cleaning dirty hot-ends.
WARNING! It should be obvious, but I'll say it anyway: don't attempt this without suitable PPE that's good enough to fully protect you in a worst-case scenario, and don't forget to protect anything else that needs protecting. In addition, consider anti-static countermeasures, like grounding yourself and the equipment to further mitigate against possible ignition sparks. Consider high-quality anti-static matts for work surfaces. Even more obviously: no smoking or open flames, and only work in a well ventilated area. Don't breath any fumes, and always be mindful of fumes and where they may travel. In short, if you lack the appropriate skills. knowledge, or protective gear, or are just unsure or are unwilling to accept full responsibility for anything that might happen, including unforeseen consequences, then immediately stop and do not proceed.
RE: Best way to completely dissolve PETG from nozzles?
After thinking about this more, I think a safer way that will probably work just as well is to alternate between soaking in the paint stripper and then ultrasonically cleaning the nozzle with just ordinary water. The soaking should attack the PETG and allow it to flake off when put in the water ultrasonic bath.
RE: Best way to completely dissolve PETG from nozzles?
I have what I think is all the right equipment ordered, so if there are no shipping delays I'll be testing this hypothesis sometime on Monday or Tuesday.
RE: Best way to completely dissolve PETG from nozzles?
One other possibility: Matter hackers says that ethyl acetate is effective for polishing both PLA and PETG, and it's a lot less toxic than some of the solvents listed above. It turns out that M.E.K. substitute is a 100% mixture of acetic acid and ethyl acetate, though I can't infer the ratio. Anyhow, it should be relatively cheap. Unfortunately, the acetic acid may eat at the metal... So, that leaves non-acetone nail polish remover as perhaps (?) a better choice of ethyl acetate. Maybe in the future there will be better guidance as to what a good solvent is--if a "safe" one even exists--but at the moment the chemical options are mostly just rumored suggestions or somebody's theory on what might work. Sorting that out would require trial-and-error, which is better suited to a group effort. whereas I am but one person.
This thread isn't really helping me, so this is my last post on it.
RE: Best way to completely dissolve PETG from nozzles?
Closing the loop: as you can see in the photo, after a lengthy soaking in the epoxy/paint stripper, rinsing it off, and then drying/buffing the nozzle with a paper towel, most of the PETG was removed, with some still clinging in the nooks and crannies. I suspect an ultrasonic water bath may dislodge at least some of what remains. After that the nozzle could either be put back into service or else run through another cleaning cycle.
So is it worth the effort? Maybe not if you have just one nozzle. On the other hand, if you had a pile of dirty nozzles, then the math changes: it's nearly the same amount of work whether you clean just one nozzle or whether you clean a dozen nozzles at a time, because most of the effort is just setting up to do the work, not the work itself.