PETG is truly a pain!! You'd think with a plastic used in water bottles, it would do better with moisture. I recommend the brand CC3D if you want something reliable (and ultra cheap!) Also remember that PETG needs more room between the nozzle and the build plate (higher z offset) so that the filament doesn't stick to the nozzle and make a mess :)
this post was submitted on 16 Jun 2023
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Drying is part of the process when raw plastic pellets are used in injection molding. The only reason it's not more common in 3DP is that common materials like PLA and ABS arent particularly hygroscopic. PETG is slightly more hygroscopic, but materials like TPU, PET, nylons, etc are highly hygroscopic and definitely need drying to print well.
Also remember that PETG needs more room between the nozzle and the build plate (higher z offset) so that the filament doesn't stick to the nozzle and make a mess
This is one of those pieces of 3DP lore that isn't correct. If Z offset is set accurately, it doesn't need to be changed for any material, but extrusion multiplier/flow does.
The reason why bumping z offset bandaids the problem is because PETs are highly incompressible, i.e., they don't respond well to being squeezed and will displace under pressure. Raising the z offset means you're putting the same amount of material into a larger physical volume. This effectively lowers EM for the first layer, but introduces accuracy issues in the rest of the print.
Instead, it's better to make sure z offset is dead on accurate and then adjust EM down so that flow is correct throughout the print.
Think about what happens to water if it's heated above 100C... it turns into steam! The more water there is in the plastic the more steam there will be, causing the various issues like bubbling. The release of steam also means some of the heat is not being absorbed by the filament, leading to temperature issues as it exits the nozzle
I have found the same, especially with PETG and PA. I even live in a fairly dry climate (Colorado, USA) and the normal air humidity is low (15-30% is not in common) so I figured it would be okay but nope! Huge differences in print quality and layer adhesion. PLA seems to not be remotely as picky but it does help.
PLA will mostly get brittle over time as it absorbs water. Biggest issue is that if it becomes more likely to break while feeding. Drying will help some there. On the whole, it's fairly low in hygroscopicity compared to a lot of other materials.
oh, I've actually been thinking that people in really dry climates must have a great time; I guess the dry air alone isn't enough though!
Okay glad it wasn’t just me then haha. I think it was Zach from VoidStar that mentioned he lived in Denver area in one of his videos and I was like “wait a second, he has a whole dry room…” and gave it a whirl and the results spoke for themselves.
I had the same experience...someone on the BK Discord shared this link, which I found pretty interesting https://fillamentum.com/pages/drying-filaments-before-processing/
Key take-away: cooling the filament after drying needs to be done in a controlled environment, i.e. put it in a zip lock bag with desiccant immediately after its taken out of the heat.
I have used my oven on the lowest temp but it really stinks up the house. I just realized that my food dehydrator basically does the same thing...worked out awesome
You're starting to make me think that my own PETG issues may be due to more than my laziness about fine-tuning after all. Time to break out the dryer (which I've previously only used with PVB, another one of those highly hygroscopic materials).
Good luck to you! Let us know if it works out. (If not, just keep that to yourself!)
Heh. Don't worry—if it doesn't help, there are plenty of excuses available. I'm not going to bother doing anything with the spool I've currently got on the printer, since I'm not sure there's enough of it left to print even a calibration cube. I'll test the next spool fresh out of the package, and then after drying it for a few hours, and see whether it makes a difference. If not, it just means that the supplier I buy from actually is as careful in producing and storing their house brand as their marketing claims, and I left the old spool out for too long.
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