Material for autoclave-able part
I’m designing a part that will need to be autoclaved—it will be under steam at 121°C for about 15 min per job and I will want it to be able to go through the autoclave repeatedly. I ran a test PLA part through the autoclave and it warped noticeably; based on their glass transition temperatures, ABS (105ºC) and PETG (80ºC) would probably also not hold up. For a consumer-grade FDM printer, what filament materials that could be used for parts that could be autoclaved?
What do you consider common filaments? This PEEK filament specifically lists its resistance to autoclaving up to 250C. https://www.3dxtech.com/carbonx-carbon-fiber-peek-3d-printing-filament/ The other PEEK and PEKK filaments there also list high continuous use temperatures and glass transition temps. It takes nozzle temperatures in the 400C range and bed temp above 130C, but it you want high temperature resistance you're going to need to be able to print at fairly high temperatures.
Doesn't PLA need >180C to melt? My spool from MG Chemical is labelled 200-210C. 121C is way below that. https://www.digikey.com/products/en/maker-diy-educational/3d-printing-filaments/944?k=pla&k=&pkeyword=pla&sv=0&pv2053=1&sf=0&FV=ffe003b0%2Cfffc01d9&quantity=&ColumnSort=0&page=1&stock=1&pageSize=25 I don't see any under 185C as the lowest temp. I've only been 3D printing about a week (after solving several assembly issues), but I would think 60C below the lowest material extruding temperature would be okay. ABS is even higher, I recall 230 being the lowest extrudable temp.
@CrossRoads: I had PLA wine charms that "melted" in the dishwasher, which doesn't even get to boiling...
Huh. I haven't tried doing any heat tests with the few pieces we've printed, will have to look into that for durability.
@CrossRoads I edited my question to correct it: the problem isn't that these materials melt at 121ºC, it's that they soften and warp at below that temperature.
@T.M. I was afraid that the problem was that if I wanted something temperature resistance, I'd need to be able to print at higher temperatures than my printer can accommodate. I have a Prusa i3 MK3s which used an E3D v6 hotend.
I don’t have the expertise others here do but the e3d v6 can reach high temps especially if it has a higher temp pt100 thermocouple and compatible heater block. The bigger problem would be the heated bed that might not be hot enough. Also if you autoclave at 121C, there must be some filament in the middle between that and peek that can handle that temperature.
I'm also considering 3D printing a mold that could accommodate a material suitable for autoclaving or using another fab method altogether, such as CNC milling.
Either of those would work too. It looks like you tested with PLA and it warped some but not too bad. Did you test PETG? The glycol is supposed to keep the PET from crystallizing and it may work for you. I’m curious if you have a chance to try it.
It might seem that common 3D printer materials such as PLA and ABS should be capable of being autoclaved—unfortunately. However, although their melting temperatures are higher than autoclave temperature (typically 121ºC), their glass transition temperatures are below that limit so they can warp or undergo creep deformation.
Sterilization of numerous plastics is described here, with PLA, ABS, and PET all being described as "poor" for autoclaving. For each "good" material on that list, I looked for filament by Googling and consulting material guides from Prusa and Matter Hackers.
Polypropylene (PP) or acetal (POM, also known as Delrin) are the best choices. Filament is available for PEEK, PEI (ULTEM), FEP, PPSU, and PPS but these filaments are expensive (>$100/kg) and require high extruder temperatures (>300ºC).
In contrast, PP is about $50/kg and uses an extruder temperature of 254ºC; POM is similarly priced and uses an extruder temperature of 210ºC. Nylon (depending on the exact type) and HT-PLA may also be worth considering.
"High temperature" filaments are not worthwhile for this application. Again, they're expensive and, more significantly, do not work well with consumer-grade 3D printers. For example, the upper limit for a Prusa i3 MK3s is about 280ºC—the thermistor only is good up to that temperature. Higher temperatures would require swapping out sensors and modifying firmware and building an enclosure. It's been done. Printers designed for high-temperature filaments easily cost thousands of dollars.
At work, colleagues print PLA parts and cycle them in an autoclave session. But for high temperatures and long exposure and frequently reuse, they print them in aluminium.
@0scar Yeah, my test part is still functional after going through the autoclave but it warped enough that I don’t think it would remain useful after multiple cycles. I wish I could print aluminum!