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I was just shopping for filament, and saw some glowing claims about PETG being as easy to work with as PLA, but as strong as ABS, and less brittle. Anyone know if that's actually true, or what the tradeoffs are?

1 Answer 1

PETG is great, but definitely not as easy to print as PLA. However the advantages of higher impact resistance, temperature resistance and longevity make it superior to PLA for parts that require those properties. ABS is even harder to print than PETG and has worse strength and layer adhesion so no reason to bother with it in my opinion.

I print PETG at 80°C bed temp on PEI bed material, with 250°C nozzle temp. At first I was trying my old BuildTak bed material and it works at 40°C but the base of my parts was warping up some, it still worked but they didn't come out flat.

If you raise the temp on BuildTak to 80°C bed then the PETG permanently bonds to the BuildTak and rips up pieces of it upon removal.

PEI at 80°C keeps the base of printed parts perfectly flat (up to a certain part size/thickness) and has good adhesion and release properties with no wear showing on the bed after many prints.

If your parts are 100% infill and over about 3/4" (20 mm) tall you may still have problems with the base not ending up completely flat. In such large rigid parts the upper area that does not stay properly heated through conduction from the bed will shrink some and pull the lower sections up with it. Lower fill density like 50%, 20% help with this problem.

PETG build up on the nozzle was a real problem for me until I got a silicone sleeved hotend, E3D is the only one who makes them that I know of right now, but I am sure there will be others shortly. This completely fixed the problem of filament sticking to the hot nozzle and later being deposited as black charred blobs.

Another thing to consider is moisture, after even a day in high humidity PETG absorbs enough moisture to undergo hydrolysis upon extrusion at 250°C and become very brittle. To avoid this I use a conventional food dehydrator with the plastic being fed from inside, you can lookup designs on Thingiverse.