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Water-resistant flexible filament

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I'm not new to 3D printing, and I've used a broad range of filaments (PLA, ABS, PET, HIPS). Recently I've bought a Flex filament from ICE-Filaments (a Thermoplastic Co-Polyester - Shore45D). Has anyone tried it?

I think it's quite flexible, so I'd like to print a mould to cast some clay and other materials that are very moist and rich in water.

How well Flex resists being in contact with water? Does it tend to warp? Probably I'll need to warm the mould up to 50°C to dry up the clay.

If Flex is not suitable, what other filament could I use?

Thank you!

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I would think that the heat would be more of an issue than anything else. Check your datasheets to see what temps are being listed.

Since most are some sort of TPU or TPU like material, water resistance should not be a problem.

PLA would not do well for that though. It is too soft when heated beyond skin temps.

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I agree with kmanstudios: heat may be a bigger problem than water (to test water-resistance, I have made a filter for the sink in PLA a year ago: it hasn't rotten away yet). Just don't use water-soluble materials like PVA. :)

In addition to this, the flexibility or lack of it may also be a problem. Heavy clay or sand will deform a flexible mould due to its weight. And a non-flexible mould of course is difficult to remove after casting. But you know that for sure.

What about printing the original model (not the mould)? And then make a silicone mould around it, and a plaster or epoxy shell to stabilise the silicone? Or use a high temp rigid material to print the shell. In this way both water and temperature are no problem. Most silicones can handle up to 200°C. On Youtube there are lots of good videos on mould making and casting.

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