Quick and easy one here. I was looking at the possibility of casting a mixture of epoxy/sand using a 3D printed mold. Molds are a bit slower to make, but you can get much more complex with designs without too much extra effort in their construction. I was mostly concerned about whether PLA would retain it’s shape with the heat of curing epoxy, and whether it would separate after it had cured.
I didn’t use any mold release at all, and with the help of @Boo we mixed up some epoxy the other night. Roughly adding 4 parts sand to 1 part epoxy, we filled the mold I’d printed and gave it a bit of a shake to try and get as many bubbles out as we could. We didn’t know if the epoxy was going to cure, so in hindsight knowing it was going to work we could have spent much more time on this.
After 24hrs I took absolutely ZERO care in separating them as I didn’t think they’d come off - and they did perfectly. All I’d coated the PLA in was some plastic primer, which seems to have prevented it from sticking totally. Cast detail is great, so much so that you can see the individual layer line (0.2mm) on the epoxy. If I’d been a bit more careful, I have no doubts that I could have saved and reused the mold.
I gave it a quick wire brush to remove the sharp edges, and I am pretty happy with the result.