Finishing parts so they're not so brittle

General Discussion
1

I have some parts that are relatively thin(~1mm)

Over time, a few days or a week, I’ve noticed the parts getting noticably more brittle.
I’ve read some threads that suggest that leaving parts in the IPA bath for too long makes them more brittle.

I’m wondering if anyone has had luck post finishing parts… for example, clear coating them to make them stand up a little better.

Any ideas?

Thanks,
Dave

2

Yes, definitely the Krylon Fusion clear UV protectant has kept my parts from yellowing and will lock in some of its earlier properties. My guess, is a UV protectant with color would be even better.

3

In parts where strength is a priority, I am printing a positive, casting a negative out of silicone rubber, and then using a high strength epoxy resin. You can make about 50 copies of the original positive with a silcone negative and its yield before break and break strength are superior.

I realize this a bit different then “finishing,” but in parts requiring strength and where you want to make many of them, its the best option. I use this to make housings for prototypes.

4

Do you know of a service that could do this or a do it yourself guide. My prototypes are too complicated for a mold but I’d be willing to just destroy the mold with each prototype.

5

I don’t know of a service, but they must exist. If your part cannot be removed from the mold because of undercuts, there are a couple of options. Sometimes small seems cut with an exacto blade (as seen in video below) can then be pushed back together after you pull out the printed positive model. If the model is so complicated that these seems will likely destroy the function of the mold then you may want to chemically remove the printed part. Silicone is inert and fairly chemical resistant. The part may be dissolved out without harming the silicone mold. The other option is doing an investment like casting and melting out the core, but instead of replacing it with metal, you could replace it with plastic resin.

There are many demonstrations on how to do the silicone molds. This is one that shows it for specifically 3d printed parts:

6

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