Silicone rubbers undercuts

Mold A manufactured cavity which preserves a negative impression of a specimen. The cavity can be filled with uncured polyurethane blends. Can be manufactured from a variety of materials depending on the production requirements, such as steel, aluminum, polyurethane, epoxy, FRP, silicone rubber, or latex. It can be manufactured in "one piece" or in multiple interlocking pieces. Multi-piece molds are used when the cast has a complex shape or undercuts which would make demolding from a one-piece mold difficult or impossible. 

The bonding is achieved by different methods. The hard component can contain undercuts where the rubber is anchored during its vulcanisation, a primer on the hard component or even using self-adhesive silicone rubber will give sufficient anchorage. 

Section 11.5. will explain the three alternatives for bonding, where mechanical anchorage (undercuts) or self-adhesive silicone rubber allow for two colour injection moulding. 

In such cases the processor basically has the choice between undercuts, primers or primerless self-adhesive silicone rubber. 

In some cases more silicone rubber is used to fill undercuts than would be required for the rubbery function of the part. 

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