Can I repair my microwave with a PLA part?
The turntable support part in my microwave has broken. It is a three armed part, with small wheels at the end of each arm.
I'm confident I could print a replacement, and reuse the existing wheels (since they can be removed).
The heat of the food would be unlikely to conduct through to the PLA, but I'm concerned that it might get heated up by the microwave radiation. I can't find any clear information online about whether PLA absorbs microwaves, or if it is in any other way unsuitable for this.
Will this be a disaster, or should I give it a go?
This raises the question of what the original part was made of, and whether or not *that* material be used in a 3D printer.
I would say PLA itself should not be heated up by microwave. It's because microwave oven creates oscilations which excites water particles (see microwave explanation here)
so assuming PLA doesn't contain water, it won't heat up.(removed to not mislead as the water is not only material which heats up by microwaves. Thanx to Tom van der Zanden for being vigilant)
But as usual, it's more complicated.
First. PLA can contain water as while producing it can be cooled down in water bath. Of course well made PLA will have as less water as possible as water has an influence on printing process.
Second. PLA is absorbing humidity so in fact it gets water inside right from the air. This unfortunately causes problems in microwave oven.
Water can be overheated and oven can overheat water above 100C. But even at 100C, PLA will not be hard anymore so your 3 arm star would "collapse". Wheels could get oval or start sticking to their axis.
Eventually if high power is delivered to very "wet" PLA, I think it can... well maybe not explode but break.
Here goes a test which shows it can be used to defrost things on PLA plate in microwave
But here Daan Snijders claims PLA gets soft in microwave during the test
Will it be a disaster?
In my opinion it will work only for short uses of MW. Heating up a glass of milk or so. But for longer sessions when there will be much more heat (out of heating dish) it won't work.
- 20sec and 950W gives no effect on my sample (hotend cooling fan duct)
- 40sec and 950W caused the sample became a bit warm
Inspite that it's not a good idea to run MW without "proper-absorber" this little test confirmes my suspisious - short sessions are ok.
The idea that a microwave only heats up water is completely wrong. Many more materials can be heated by microwaves.
Of course you are right. But microwave is generally designed (oscilation selected) to excite water particles primarily. Many metals get heated up by MW (of more prcisely by eddy currents). But in terms of PLA and his 3 arm star it's not applicable :)
here is a part of the article you linked: "...and therefore rotate as they try to align themselves with the alternating electric field of the microwaves. Rotating molecules hit other molecules and put them into motion, thus dispersing energy...". My understanding of microwave oven is precisely as this citation and my answer is based on this understanding. "Frequecy" means "oscillation" for me... and not only for me (wiki:frequency-This article is about the rates of waves, oscillations, and vibrations.) I have a feeling you are trying to over-generalize questions and then answers ;) no offence
Heat IS rotation/oscillation so obviously that will be involved at some point. However, you are making the claim that microwaves are designed to heat up water *and only heat up water* and therefore items not containing water do not heat up. This is not true. It could very well be (or not) that PLA has dipoles as well. The exact mechanic by which the heating happens is secondary to this (if you continue reading beyond the quoted portion you'll notice that they mention that heating through *resonance* is a common misconception which I thought your argument about oscillation was referring to).
:) I've read whole article in EN and in my native lang again to not argue without arguments. As I said - you are right but it's not really applicable to his question.
ABS filament tends to absorb water over time, so I would think and ABS part wouldn't hold up.