Closed Mold Processes Could Benefit Composite Businesses

Closed mold processes are methods of producing composite products in which composite fibers and resin cure inside a two-sided mold or a vacuum bag. 

Because resin is cured in a closed mold system, there are significantly fewer emissions, helping manufacturers meet Federal and State emissions standards, while reducing the need for worker protective clothing and other PPE equipment. These processes are also less operator dependent compared to open molding, reduce labor and may require fewer molds reducing tooling costs.

the most common type of closed mold processes are the Vacuum Infusion Process or VIP, Light Resin Transfer Molding or Light RTM and Resuable Bag Molding.

Vacuum Infusion Process (VIP)

VIP is one type of closed mold process which uses vacuum pressure to force resin into a laminate. Like other closed mold processes, VIP uses a rigid “A” side base mold, but unlike other processes, it uses a thin bagging film being as the “B” side or counter mold. Specialty reinforcements are laid into the base mold, with bleeder cloth and bagging film sealed onto the base mold. A vacuum is pulled through ports in the bagging film and catalyzed resin is pulled into the mold cavity based on the level of vacuum pressure.

Vacuum infusion processing allows users to create durable, lightweight composite laminates that can be used in a variety of applications, especially the manufacturing of large structures. In addition, this type of closed mold process offers users the benefit of reduced chemical vapor emissions when compared to composite production processes such as open molding. 

Light Resin Transfer Molding (LRTM)

Light RTM is a closed mold system that consists of an “A” side base mold and a semi-rigid fiberglass “B” side mold or counter mold. The mold flanges incorporate seals that create an air-tight seal when the counter mold is placed on the base mold and vacuum pressure is applied. The laminate stack plies of fiber reinforcements are placed in the mold and the tool set is clamped. As vacuum pressure is applied to the sealed mold, catalyzed resin is drawn into the mold through ports incorporated in the counter mold. A resin injection pump is typically used to accelerate the resin infusion process. Once the resin is cured, the counter mold is removed and the part is de-molded from the base mold. Light RTM is a versatile manufacturing process that can increase productivity with mold cycles as fast as twenty minutes using several base molds and a single counter mold. Light RTM also produces finished surfaces on both sides of the part, reduces labor costs, enhances dimensional stability, and improves process control. Because it is a closed mold system, Light RTM greatly reduces HAP emission and improves shop working conditions.

Reusable Bag Molding

Reusable Bag Molding (RSBM) is the fastest and easiest closed mold process to implement in a production shop. With excellent part-to-part consistency and ease of conversion from open molding, RSBM has become a viable alternative to open molding for numerous applications. Reusable Bag Molding incorporates a rigid “A” side or base mold and a flexible “B” side or counter mold that is made with silicone, latex or other rubber-like products. The bag may be made by brushing or spraying silicone material on the base mold and incorporating seals where the bag meets the mold flange. Like other closed mold processes, the base mold is charged with fiberglass, the flexible counter mold is put in place and a vacuum is drawn through ports incorporated into the bag. Catalyzed resin is introduced through the resin ports using a low pressure injection pump and the cavity is filled and cured. The advantages of Reusable Bag Molding include low tooling costs (existing open mold tooling can be easily converted), a reusable and repairable bag, significant reduction in HAP emissions, and ease in training operators with a relatively simple technology.

Turn to Composites One for All of Your Closed Mold Process Composite Supplies

Composites One is the leading distributor of composite materials in North America. If your business is looking for a customer-centered supplier of composite materials for your closed mold process business, look no further than Composites One. For information about composite supplies or technical assistance, contact the Composites One team today.