Fiberglass Molding is a process in which fiberglass reinforced resin plastics are formed into useful shapes.
Making a Mold
A plug or buck is required first to make a mold. This will be an orginal part that is to be copied. First the plug must be waxed with mold release wax. Depending on the desired surface, PVA (Poly Vinyl Acetate) may be sprayed on as an additional mold release agent. However this will reduce the smoothness of the molds finish.
Once the plug has its release agent applied, gel-coat is sprayed onto the plug. Gel-coat is a pigmented resin without reinforcement. Tooling gel-coat is used for its harder more durable finish.
Molds are usually made from the same fiberglass the part is made from. A mold should be 5 times thicker than the part being made. Such as if a part is made from two layers of 1.5 ounce mat, then the mold should be 10 layers of 1.5 ounce mat. Layers of fiberglass will be applied, and resin added bonding the fiberglass layers together.
Once the final layers of fiberglass are applied to the mold and allowed to set up, wedges are driven between the plug and the mold to separated the two. Once released you have a negative image of the orginal part.
Making a part
The making of a part is the reverse of making a mold. The mold is waxed, and PVA is applied if desired. The mold will be sprayed with gel-coat in the desired color of the part, then layers of fiberglass are built up to the desired thickness. Once complete wedges are used to separate the part from the mold.