Terminology:

• Positives: the inner shape of a hot wire cut, essentially, the not hollow part of a cut
• Negatives: the outer shape of a hot wire cut, essentially, the hollow part of the cut

Overview

One of the main processes that we do in manufacturing is the creation and usage of molds. Molds are used to create every part of the aircraft, from the fuselage to the wings to the tail. It allows use to create the shape contours that we want while also allowing us to have a hollow interior for the payload and structure parts like ribs, bulkheads and spars. Generally, our molds are made of XPS foam, either we purchase them from home depot or borrow some from AFL. Previous molds have been made of loose fiber glass that was composite layuped onto the positives of the mold after they were hot wire cut out. The reason why we use the foam is because it is easy to manipulate with the hot wire to create complex shapes and it isn't as expensive as other materials. After we CNC hot wire cut what we want, we use the negatives and sand them down slightly to smooth them out. We then use an epoxy toolkit layer painted on to leave an even smoother and finish and harder surface for the carbon fiber or fiber glass that will be layuped on it. Finally, we apply a wax on top as a release film so the skin does not get stuck to the mold. The process is explained in this document in more detail here.

Here is an updated version of our mold manufacturing process we completed for the onboarding aircraft.