Closed mold processes create lower cost precision parts

Closed mold processes can help produce precision parts at a lower cost and can be used in a variety of applications. Traditional composite tooling is typically used for the rigid base – the “A” side mold; different materials can be used for the “B,” or counter, side, depending on the process application. Regardless of the type of closed mold process used, dry reinforcements are laid into the base mold. The mold is then closed and the resin is introduced into the closed cavity via a pressure pump or vacuum. Once the laminate is cured, the mold is opened and the part can be removed.


Closed mold processes have a distinct benefit over open molding as they allow manufacturers to produce better parts more quickly and consistently with less waste, which can help save on cost. These finished parts also feature better surface cosmetics, which means less need for post work.


In addition, there are fewer emissions in a closed mold process, which helps manufacturers meet Federal and State emissions standards. Workers don’t need to wear as much protective clothing or other PPE equipment, and these processes are less dependent on operators than open molding, reducing labor costs. Finally, since closed mold processes require fewer molds, they help reduce tooling costs.


There are several different types of closed mold processes:


Light Resin Transfer Molding

Light RTM is a good choice for production parts that require consistent quality and surface cosmetics.  A versatile manufacturing process, it can increase productivity with mold cycles as fast as 20 minutes, thanks to several base molds and a single counter mold. Light RTM can reduce labor costs, enhance the dimensional stability of the part and improve process control.


Reusable Silicone Bag Molding

The fastest and easiest closed mold process for a production shop, Reusable Silicone Bag Molding offers excellent consistency and an easy conversion from open molding. Other benefits include low tooling costs, a reusable and repairable bag, significantly lower HAP emissions than open mold processes, and a relatively simple technology that makes it easier to train operators.


Vacuum Infusion Process

Rather than using a rigid “B” side mold, Vacuum Infusion Process (VIP) uses a thin bagging film. It’s governed by the principles of D’Arcy’s law, making it a highly controllable process, as well as an accurate bill of material for a given part, with constant resin and fiberglass uses. Styrene emissions are minimal as the resin cures in a closed environment, and VIP results in an excellent glass-to-resin ratio with little to no voids in the finished laminate.


Composites One can help manufacturers with closed mold processes

As a founding member of the Closed Mold Alliance, Composites One can help manufacturers source equipment and raw materials, along with hands-on training and information on the appropriate processes for your applications. To learn more about Composites One’s dedicated Technical Support Team – the only one in the industry – contact us today.