This chapter examines the following concepts: process overview, gel coat considerations, lay-up molding, spray-up molding, tooling (molds), and quality control and safety. The simplest technique to mold a composite part, probably the first used in modern times, puts fibers into an open mold and then adds resin to the fibers. After ensuring that the fibers are fully wetted by the resin, the resin is cured. Because the resinis added at about the same time the fibers are placed into the mold, these processes are called wet. The methods of placing the fibers into the mold can be divided into two general methods — lay-up and spray-up. In both lay-up and spray-up, the mold is not only the definer of the shape of the part, but it provides the surface on which the materials are deployed prior to cure. All parts made by lay-up and spray-up should be inspected after removal from the mold. When a simple method for making a part is desired, lay-up is the method most often used. Spray-up is similar to lay-up in many ways but adds the advantage of faster application of the resin and reinforcement. The tooling for both lay-up and spray-up is generally made of composites. This tooling is made from a master model shaped like the final part. The mold is made by laying up composite on the master model. This mold is then conditioned with mold release and then can be used to make many parts.
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