Male and female molds are the two main types of forms, but they produce significantly different finished parts. The most time consuming and cheapest method is a male (or positive) mold. This is a form that mimics the final shape of a part by being fabricated on its outer surface. Indeed, this type of mold is constructed faster, but each part produced has a rough outer texture, which requires laborious finishing. This part will also “grow” during lamination. Generally, this is undesirable unless the mold is intentionally made slightly smaller in the event that such growth is expected. When producing less than 5-10 parts, a male mold should be used, which should not be used when aesthetically pleasing surface treatment is required. Large production runs often require time and cost associated with female molds. The remainder of this white paper focuses on the construction of female molds, but male molds can be made from the same materials.
Female (or cavity) molds are generally more expensive, but they offer many advantages for medium to large production runs and applications that require aesthetically pleasing surfaces. Finishing time is significantly reduced because each part has a smooth outer surface. Female molds are also suitable for core materials because the external skin is always smooth regardless of the inconsistency of the core used within the part. Any type of mold can be used for vacuum bagging, but the female mold is usually easier to seal while achieving good surface characteristics. If you produce more than 5-10 parts that require a smooth surface, the female mold is worth the extra effort.
Compression molds are sometimes made by using male and female forms. These “matching” molds are ideal for producing precision parts. The mold is filled with reinforcement and resin prior to closing and tightening. Excess resin is squeezed out, voids are reduced, parts appear smooth and finished on both sides. Compression molds can also be modified for resin infusion or injection. The key is to consider the intended use of the finished part and the type of mold needed to build it. If this is considered in advance, there is no limit to the types of parts that can be produced.
Post time: Aug-22-2019