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The turntable support part in my microwave has broken. It is a three armed part, with small wheels at the end of each arm.

support part

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?

aaaidan
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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.

SHORT TEST

  • 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.

darth pixel
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You really shouldn't

  1. PLA "glass point" (the temperature where it starts to get soft) is approximately 60C, even if it doesn't heat up from the microwaves it's way to likely the ambient temperature in the microwave will reach that level and cause the part to collapse (even if you "never" get it hot - it only have to get to 60C once during the lifetime of the part).

  2. PLA is not safe for cooking (or even for food storage) and your typical PLA filament isn't even pure PLA, only god knows what chemicals there are in your specific brand of filament and what will be released into the air inside the microwave when it's heated.

In first glance ABS seem to be a better option because it has an higher glass point and food-safe ABS exists - but it's still bad because even food-safe-ABS is only safe for cold and room temperature food.

I don't know about other materials.

Nir
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Yes. You can. I would think ABS would be a better idea, as it melts at a higher temp. http://www.thingiverse.com/thing:385288

EvilTeach
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There are Food Safe PLA filaments. These PLA filaments share similar qualities with ABS, in regards to temperature extremes et al. There are several on the market. (Eg. https://shop.germanreprap.com/en/pp-plastic-600g-3mm-black and http://www.formfutura.com/hdglass/ -- I've not used the HD glass personally but have been told it works well)

When shopping for food safe PLA filaments check for the Material Safety Data Sheet (MSDS) that comes with the filament. It will contain all the normal chemical warnings, some composition information, etc. but will also indicate if the material is Food and Drug Administration(FDA) approved.

PLA, food safe or not, can also have bacterialogical issues--the material is pourous enough to allow for bacterial growth. I would suggest using a polyurethane to seal the printed part to limit bacterial growth.

You will need to check what sort of extruder you have on your pinter. Many brass extruders also contain lead which can leach into the printed product. Switch to a stainless steel print head to avoid this issue.

General care--warm soapy water and handwashing.

I would not, as yet, recommend any printed product as a vessel for food--cup/bowl. This element is still somewhat new and I don't personally trust the materials for extended contact with food. (Knives/spoons et al. have much shorter contact with food vs. a plastic mug of hot coffee).

For your intended application, the piece in question would not come into direct contact with food to be consumed. As such, you should be fine with the correct filament.

WarOrdos
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