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Closed Mold:
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Reusable Bag Molding Reusable Bag Molding is often described as a hybrid process that borrows desirable features from both LRTM and VIP. Reusable bags are especially useful in applications where part geometry is complex and where high glass-to-resin ratios are desired, but where disposables and slow cycle times are not acceptable. In the last five years, reusable bag molding has emerged as an economically viable process for a wide range of composites molding applications. Many reusable bag processes are patented processes (like CCBM, Flex Molding and Sprayomer) that is simple to adopt and features tooling with one rigid mold half and one very flexible mold half. With the exception of a wide perimeter flange, the rigid mold half can be constructed in exactly the same manner as an open mold. The reusable bag process uses vacuum to clamp the mold halves and to help pull the resin through the reinforcement. However, the resin is injected rather than infused as in VIP, but under relatively low pressure (the use of vacuum and injection pressure simultaneously is often referred to as a push/pull system). Rusable bag molding is gaining popularity because it works well in many applications and because it has truly fulfilled the promise of a simple, low-cost closed molding process. Each of the popular low cost molding processes has advantages and disadvantages. A typical molder should learn all three processes, choosing the process that is most suitable for each application, based on part geometry, customer specifications, and desired production volume. If an open molder has concerns related to styrene emissions, shop working conditions, worker retention and training, or part-to-part consistency, reusable bag molding may provide a viable alternative to open molding.
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