Part 4 – Mold Making

For HEXAPODA, creating a piece like the Magicicada, involves a two-stage casting process. The first stage – covered previously in Casting in Metal – involves creating a master casting in metal, while the second stage, – which we’ll cover here – uses the re-worked master casting to create a latex rubber mold that will be used to help create derivative castings.

Most ‘molds’ are used to directly create a finished item (think jello or ice cubes), but due to the 3 dimensional complexity of the Magicicada’s body, a direct approach like this won’t work in our case.

Fortunately, the investment casting process, does allow the creation of multiple, complex pieces – but to do so, it also requires a wax model for each metal item created.

This is what our mold will provide.

To create the mold itself, the bronze master casting created previously is placed within an aluminium frame and covered with thin rubber strips to a level slightly above the top of the frame.

The frame is then sandwiched between two aluminium plates and set into a special press called a Vulcanizer. This device heats and compresses the aluminium frame assembly, and the rubber strips within.

As the assembly reaches 300F, the latex rubber begins to melt, flowing into the spaces it doesn’t already occupy within the frame. With the pressure generated from compressing the frame assembly in the press, the liquid rubber flows into and around all the highly detailed areas of the master casting.

When the assembly has cooled, the now solid latex block, which totally encapsulates the master casting is removed from the aluminium frame.

The master casting is then removed from within the block by carefully cutting it in half. 

Barely recognizable as an exact and precise negative of the master casting, this then becomes the mold from which all wax models will be created for each and every subsequent Magicicada.

When it’s time to create wax models, the mold is reassembled, and injected with melted wax under pressure. This creates a precise wax model of the original master casting, which can then be used to repeat the metal casting process described in Casting in Metal.

Now, with the means to create more than one Magicicada – next month, in the final installment of the series, I’ll describe the finishing steps, that ultimately make each Magicicada unique, yet appear like the ones you see below.

>> Part 5 – Finishing

Would you like a Magicicada smilar to the one
featured in this article?


Click for more information