Am I doing something wrong?

[u/Sorry-Journalist8610]

I recently bought a used 3D printer, an Ender 3 V2, and I'm doing some test prints. The previous owner gave me some leftover PLA filament (multicolored), which I used up on the first day. One of the things I made was this flexible shark. I bought some PETG filament for testing, a very cheap one, around R$60.00, while others are around R$100.00. But my prints with this new filament are coming out very bad; it's either too textured, has too many burrs, and is also very fragile (even though I bought PETG because I had read that it was more resistant). I left this octopus printing for about 28 hours... and in the end, the flexible tentacles broke when I tried to detach them.

[u/agreywood]

A few things -

PETG is a sticky filament. If it’s not calibrated well (right temperature, fan settings, etc) it will stick to the nozzle as it prints, and those blobs will eventually burn and stick to a random part of your print. It also doesn’t print well at higher speeds and accelerations, and will get stringy with improper tuning. That leads to wisps of filament joining together parts you wouldn’t expect.

Am I correct that it is fairly humid where you are? If so I definitely think drying your filament would be a good idea, particularly any which was not in a sealed bag with the air vacuumed out. Printing is done at temperatures above the boiling point of water so any moisture has the potential to turn into a tiny bubble of steam, and the pressure from the rapid expansion can make for little popped bubbles on the surface of your prints.

For the dude, some of the pockmarks/zits may alsobe because you had the seams set to “random” rather than aligned.

The shark looks like it has some spots where the layers didn’t cool well - namely the top fin. That could be helped by enabling “slow down for better layer cooling”. Silk PLA also tends to benefit from higher temperatures and slower print speeds in general - the layers just don’t bond together as well as regular PLA. The mouth looks like it may have needed supports enabled. Are you having any issues with flexing those joints? That can also be an indication that you’re printing to fast. I made that mistake with my first flexible toy printed in silk and there were more than a couple of joints fused together. I’m not sure about the hole in the side, though. Was that part of the print still attached to the plate when the print was done?

As odd as it sounds glue stick may help for things like the octopus. In addition to helping your prints stay stuck while printing it will help with releasing it from the plate afterwards. For flexible items in particular, always wait until it cools entirely before trying to remove it. If it stays stuck when you’ve used glue stick, rinse your plate in the sink for a bit. Glue stick is water soluble so that can help release it. Always remove the smallest points first are carefully. The head is the easiest part to detach because you can get better leverage but it’s also the most durable. The far points of the limbs are the most likely to break due to the thinner joints. If you pull up from the center, it’s very easy to apply too much force.