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Combining 3D Printing and Lost Wax Casting to Make a 3D Puzzle

Creative craftsman Seth of Robinson Foundry makes things out of metal that would be difficult or impossible to machine the traditional way. As an example, these bolts with zigzag threads:

He then struck upon the idea of creating a rather unique maze, or a sort of three-dimensional combination lock:

The point is to get the nut, which has a protrusion on the inside, all the way along the shaft by rotating and advancing it:

So how did he make them? Using the lost wax casting process, but with PLA rather than wax. After designing the shape in CAD, Seth 3D-printed models of both the nut and bolt.

“Then I coated the models 10 times with a ceramic material called Suspendaslurry,” he writes. “After the ceramic shells were completely dry I placed them in my kiln and melted out the PLA plastic. 

"At 1500 degrees Fahrenheit the ceramic shells became vitrified, turning into a ceramic that can withstand the heat of molten bronze. I melted the bronze in my homemade keg foundry furnace and then poured the liquid metal into the ceramic shell molds.”

Here’s a look at his process: