Sunday, April 3, 2011

Ichabod: Molding the Eyepiece

Continuing with the Ichabod eyepiece, I seal the outside with Bondo™ auto body putty so that the mold material won't leak in between the individual pieces of acrylic.
I hot glue the model to a small piece of Formica. Here I am hot gluing a paper popcorn cup down around the model to contain the rubber.

This is the model, cup and wooden dowel (to make it easier to demold and to save on rubber) ready for the silicone rubber.

The silicone rubber RTV (room temperature vulcanization) is ladled out with a spatula.

First I weigh out the white rubber base......

.....then I weigh out the dark blue activator, which is 10% of the base weight.

After mixing it completely with the spatula, the silicone mix is placed into a vacuum chamber to boil out any excess air. This picture shows the rubber mix boiling away (at room temperature).

Once it is vacuumed (deaired) the silicone rubber is poured over the model.

The next morning I demold the eyepiece, and cast it in a charcoal colored urethane resin. I sand smooth both the interior and the exterior of the casting.

Now for the decoration. Rather than add screws or bolts as I have with earlier steampunk eyepieces I have decided to add a design in bas relief. First I draw out the design with a black Sharpie™ on white paper, then scan it. Bringing it into CorelDraw™ I vectorize it and clean up the lines, then laser cut it out of green card stock to check the fit onto the eyepiece.

All looks well so I proceed to laser cut a thin piece of foam with mirror images of my design. The pressure sensitive tape on the back allows them to be attached and ready to mold.