PETG Annealing
Hi All-
I've got a part that I'm working on that where I'd like to increase the impact resistance. The material I'm using is Extrudr PETG.
I read the article about the benefits of annealing, so I thought I'd give that a shot. Reading the article, I thought I would try annealing at 250F (120C) for 30 min.... well.... that didn't turn out so good. Part completely melted and collapsed.
I used a meat thermometer to monitor the oven cycle. I monitored the cycle the whole time and the thermometer never got above 265F. The thermometer might not be the most accurate tool, but the tolerance should have been close enough for my purposes.
Certainly the material should have never got close to the 340F (170C) to break down like I'm seeing.
I'm not sure what happened or if I did something wrong... but I'm leaning toward the material not actually being PETG.
RE: PETG Annealing
I think PETG will begin to soften at around 85C much earlier than the melting point around 260C .
Add another 20-40C to the 85C and you might have no structural strength all all.
Reminds me of the argument about iron steel beams .........
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RE: PETG Annealing
You need something to help the part hold/keep its shape while softened otherwise it will just ooze into a pile. There are videos/articles about people using various powders (salt, talcum, etc.) and I think CNCKitchen has a video trying plaster.
Annealing 3d printed parts is a bit more laborious than just chucking it into an oven and waiting for it to bake esp with a usual imprecise kitchen oven.
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RE:
Yeah, copy that. Started thinking about some way to fixture after I posted. Thanks for the reply.
RE: PETG Annealing
I think PETG will begin to soften at around 85C much earlier than the melting point around 260C .
Add another 20-40C to the 85C and you might have no structural strength all all.
...
I can attest to that. Recently I tested small triangular "pillars" (printed from newly opened Prusament PETG) that were supposed to hold LED strips on the back of an IR-panel heater (red LEDs in silicone, supposed to act as on/off-indicator). Since the panel can reach 110 °C in the center, I needed to make sure the pillars hold shape enough over an extended time of heating to keep the LED strip in a stable position.
To cut a long story short: using a T-controlled hot gun and a laser temperature meter (so I reckon T was close within 5 °C), my results were:
- T ~ 80 °C: softens only slightly, disfigures under higher pressure, regains shape when deformed within small margin
- T ~ 100 °C: even more, a bit gummy; still sufficiently stable
- T ~ 120 °C: too hot to hold for more than a few seconds, edges deform easily, shape not entirely regained; feels a bit like a rubber inner-tube
Knowing a tiny little bit about metallurgic annealing from a past profession in the field of CAE/FEA, plastics are an entirely different material. There's not "sticking together better" of tiny printed lines since the base material does not change characteristics, compared to "cristalline arrangement optimization" in annealed metal. If you need something to have a high(-er) structural strength, fiber additives in your filament may help. Or ultimately have your part made from injection molded (carbon-) fiber reinforced material.
RE: PETG Annealing
I'm pretty sure annealing 3D printed parts are most realistically done on 100% infill and simple shapes, like a flat rod or something.
I'm sure it's possible to anneal more complex shapes using e.g. sand to maintain shape etc, but at that point I've got to ask if there really isn't a more easy solution. A different filament type (PETG isn't the stiffest / toughest), a different material altogether, or just a different geometry.