Another PETG thread.

Been a while since I’ve been on here. I recently picked up some PETG from a local supplier as an emergency, they didn’t have any 2.85mm ABS which I usually use. I’ve had it a few days now and I just can’t get it to behave, I’ve had 3 nozzle jams and a tonne of stringing. I’ve googled and read about and tested many different things; temperatures ranging from 255 to 215, fan speed from 0 - 70%, print speeds from 30mm/sec to 60mm/sec, different retraction settings, travel settings, messed around with coast and wipe in s3d, the lot. Filament measurement is absolutely bang smack on - measured and remeasured 3 times just to be sure - and flow rate down to 95% (94% starts leaving gaps between passes).

I can get smaller objects or solid, single piece objects to print perfectly but anything with travel moves over the perimiters is just covered in globs and strings and nothing I’ve done has managed to change that.

I think I’ve since decided the standard Taz 5 extruder just doesn’t like this material. I know it can be printed cleanly, the shop I bought it from were using the same type (same brand, same colour, same size) when I went in to print 4 seperate large objects at once on one of those new raise3d printers without so much as a hint of stringing, and some of the prints they showed me which they’ve made with PETG were outrageously good (so good you would have thought they were injection moulded).

What kind of objects is everyone managing to print with PETG? I’m interested to see what people are pulling off without creating such a chaotic, hideous mess.

I’ve done pretty good Benchy prints with it. You can find my profiles on the forum here for S3D.

For grinding/jams, try adjusting the tension on the idler a little. Too much will actually be worse. And increase the temperature, particularly if you do a lot of retractions. I run my PETG at 275C. I only have Makergeeks and eSun here, both seem to print about the same for me. It is definitely more prone to grinding than ABS is.

For stringing, it’s really sensitive to having Z-offset set properly. Try increasing it a little, the first layer doesn’t need to squish much at all, unlike ABS. If you have it wrong, when it travels the head, it hits the print and pulls strings. Another thing that helps is to clean the nozzle thoroughly with a scotchbrite pad when hot, but before the print starts. I use the blue ones and they work well. Do not use metal stuff, it can short out things on the hotend and fry the control board.

Double check that you aren’t over-extruding, that makes strings as well. Though it sounds like you’re good there.

Try increasing the retraction speed. You want to clear the nozzle pretty quick as it’s a bit ooze prone. I think I have mine set at 30 mm/sec.

Other than some fine hair-like strings, PETG generally behaves very well and is pretty easy to print. It doesn’t bridge well, and you’ll need several solid layers or high infill to get a smooth top surface. I generally print at 245c on a 70c bed.

Do this test: Bring the nozzle to printing temp, manually extrude 20mm of filament, and immediately remove that filament with tweezers. Now watch for about 5 seconds. Normal behavior would be to see a little ooze, maybe even 5mm, quickly at first then much more slowly as pressure subsides. If, instead, you see it continuing to push out of the nozzle, twisting and bubbling/popping, amounting to 15mm or more in a few seconds… Then your PETG is damp.

Damp PETG will ooze out so quickly that (even with retraction) long travel moves are problematic. You’ll have all kinds of blobs and pieces of extruded filament getting caught on the perimeters of the part.

If you suspect moisture, take a few meters of filament (or the whole spool) and bake it in a 150-160F oven for 4+ hours. Cool it down, then try printing with that “dried” filament, and see if there is an improvement.

Thanks for the suggestions. I already had my finger on the pulse with most of them. I didn’t think moisture would be a problem, not where the printer is currently temporarily situated. Nonetheless I tried baking it just to see, after checking on it 30 minutes in the petg was dry as a bone and completely brittle, it’s unuseable now.

I just went and bought some ABS instead :laughing:

Proper PETG does not rely on “moisture” for any part of its flexibility. Accordingly, the removal of moisture by baking at 150F does not make it brittle. I have done this many times – in fact, I have a print running right now using a roll that was baked at 150F for 6 hours.

What brand PETG, and where did you buy it? If baking at 150F made it brittle, there is something VERY wrong with the formulation.

I’m based in the U.K., I think it’s an unbranded filament, I got it from technology outlet.

I get great results with PETG from eSun. If you are getting brittle petg from baking at only 150 or so, then I second what ScottW said. Something is very wrong with that PETG.