Printed game pieces can feel a bit too light... but we can fix that!
But let's step back a moment: what can you do with flexible 3D prints that you can't do with more conventional stuff? Well, it turns out that one area that flex shines is in moulding rigid materials. Rigid moulds are fine if the content has a bit of elasticity, but for something like concrete it's a huge pain! Even the fine texture inherent to FDM printing clings to the supremely solid cast interior.
So, concrete dominoes! Let's just mention one thing here - concrete isn't really ideal for relatively small castings like this. Something like plaster is undoubtedly superior. Except... it's not concrete, and doesn't sound as cool.
Right! So, I went through quite a number of approaches to the moulds themselves, and in the end I discovered that very thin walls were just fine, and allowed for easiest release of the cast object afterwards anyway. Also, this meant that the moulds were quick to print and used very little filament, so I just modelled moulds for all 28 standard pieces.
Originally, when the moulds were more complex, I had a modular approach that used fewer printed pieces, but there's really no need for such fussing around.
Now, printing was... interesting. If you already print with flexible filament, you won't have any issues. However, I had endless problems getting 28 good prints done. I worked initially with a "flexible PLA", but warping was ridiculous, even tearing itself off a few solid layers of regular PLA I tried layoing down underneath! In the end, though, I had good luck with TPU, and it proved to be nice and strong, too, when I stretched the moulds open to release the pieces.
If there's one thing that's really, really important, it's this: Always use a releasing agent! Always! What is a releasing agent? Basically, something to stop the concrete sticking permanently to the mould.
Canola oil, ideally just plain old canola cooking spray, is amazing for this. I was able to just push my cast dominoes out of the moulds, with no breakages or problems. If you don't have that, you can probably use most oils, as long as they don't have some incompatibility with your concrete.
I just really love finding the things that 3D printing lets us do, that we couldn't do otherwise.
And, precision concrete casting is just plain cool.