Candle castings with 3D printed molds

I can safely say that my son is a Super Mario fan. He plays it, reads manuals, learns english for reading more about it from Wikipedia and generally knows a lot about the game and Nintendo as a company. We have printed and designed numerous Super Mario related items in the past with our Alibre+Ultimaker combination. As his 7th birthday is nearing he wanted us to make an Super Mario related candles for the party. And not just any character but an Bomb Omb – an round “bomb” shaped figure with small feet and large eys. And on top a fuse-line acts as a candle heart 🙂

I thought this was a perfect opportunity to test some castings with candle wax/stearin. It has a melting point of 70 C so PLA should be just fine for mold. I remembered reading from Thingiverse about Openscad script that someone had generated for making molds. After a while I found it: Parametric two-part mold generator for OpenSCAD by jasonwebb. We already had designed a Bomb Omb with Tinkercad but quickly realized it was not suitable for casting because of some shapes it had. And because Tinkercad is closing, we decided to model a new Bomb Omb with Alibre. That took only about half an hour and Jasonwebb’s Openscad script worked nicely after that. After some parameter tweaking we were quite certain that we had good mold halfs. After about 4 hours print we melted few candles in a small metal pot and poured them in to the mold. I was surprised to find that all wax was”lost” very quickly after pouring. None of it stayed in the mold but none of it dropped to floor either. I wondered where did it go – quickly realizing that mold was not solid enough and that it was sucking all that wax inside of the mold. Mold was printed with 20% fill and apparently had some very small holes in the inside surface.

We then coated inner surface with 2 compound epoxy resin and after curing overnight I did a new pour today. This time it seemed to fill just ok but after opening the mold I realized that the mold was only half filled and casting was not usable. Well, it was really quick to re-melt the cast and pour again. This time I poked and stirred molten wax inside the mold with a small metal file. This seemed to help and after cooling we got a nice little Bomb Omb candle. To next pour we’ll add a proper “candle heart” to act as a fuse for this little figure.

It was a nice experiment and I’m surprised with the results – this was my first casting ever with a proper mold. Only castings I have previously done were lost foam aluminum castings many years ago. In the future I would definitely like to test proper some sand castings with 3D printed mold positives.

Here are few pictures from our first succesful cast.

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