I found a small length of filament in the parts bin. I don’t know what it is, and nobody else here does, or remembers ordering it. I’m pretty sure it’s a sample that was sent by Prusa when we ordered the printer, and it’s probably not a special material.
It’s feels “gummy” and a lot softer than PLA, but not really rubbery either. And I tried printing something with it at 230C as if it was PLA and it’s clearly not hot enough: it’s able to flow out of the nozzle but it barely sticks to the bed.
Any idea what it could be?
Well, I toyed with the printer’s temperature settings until I found a combination of nozzle temperature and bed temperature that finally made it spew out parts without making a disaster.
It seems to flow best at 260C, but then when it lands on the bed, it immediately shrinks as it cools and the part curls up and comes unstuck. I had to lower the temperature to 245C and raise the bed temperature to the maximum this printer does - 110C - for the part to stick enough to complete.
The nozzle clearly isn’t hot enough because some layers on the final parts look like they’re about to delaminate. But any hotter than that and the material curls up. And it doesn’t matter what bed plate I use: that stuff doesn’t seem to stick to anything properly.
I printed spectacles with that mystery filament. You can see how floppy it is here:
https://toobnix.org/w/qJJ1htb9eqmiHx7gSpq2RT
It looks like TPU alright, but the temperatures involved aren’t really typical of TPU. Also, acetone does nothing to it whatsoever.
The material also doesn’t like to be filed or sanded, and the best results for a nice finish without bits of material sticking out all over the place is to “polish” it by running a very sharp x-acto blade across the surface until all the junk is gone and the surface is shiny.
Weird filament. Kind of useless…
You might have some polypropylene there. Really strong material! Won’t stick to shit, temperature resistant, chemical resistant, can bend without breaking… never tried it, personally but it’s interesting stuff.
And notwithtanding that the damn stuff is around $78 for a kilo of filament! My other guess was polyethylene (HDPE). These two are pretty similar mechanically, both being polyolefins, but polypropylene melts at a higher temperature.
It might be TPU too. I’ve used it to print function tires and the random deformable fidget.
The more I look at it, the more I think that is in fact TPU. And in fact I’ve read somewhere that most varieties of TPU are in fact impervious to acetone. The one roll I have here isn’t, but maybe this yellow piece is such a kind.