Patterns, Moulds & Tooling
The first step in many composites projects is the creation of a patterns and moulds. Patterns are shaped exactly like the finished part that you will ultimately make but are often made from easily shape-able materials such as tooling board, foam or MDF. Patterns are then surfaced and finished such that a release surface can be obtained. In a simple mould making process this pattern is then used to create the mould itself which is made by coating the pattern in release agent, then tooling gelcoat and then resin and reinforcement. In more involved mould making (to achieve a higher quality finish or means of making more moulds) the first mould is then used to produce a GRP master (which is like the pattern only now made from fibreglass) before the master is finished to an even higher standard and then used to create a final mould.
If you intend to make parts using high performance epoxy resin, it is necessary to make your moulds out of epoxy gelcoat and epoxy resin and not out of polyester resin (used in more basic composites).
Whilst chopped strand mat reinforcement is often used in mould making, it is important to be aware that conventional chopped strand mat, designed for use with polyester resin, is not suitable for use with epoxy resin because the binder used to hold the fibres together on the roll will not be broken down by the epoxy resin. Instead, special powder-bound chopped strand mat should be used with epoxy resin systems.