Reusable Bag Molding is an Easy Entry into Closed Mold Processes

Composites One is leading supplier of composites and high performance materials. Because we are knowledgeable about composites manufacturing processes, our team at Composites One often shares that knowledge with our partners in the industry. One of these manufacturing processes is a closed mold process called Reusable Bag Molding. This process produces a higher quality product in less time and for lower cost than the traditional open molding process, making it appealing to manufacturers, allowing them an easy entry to closed mold processes in general.

With a quick turnaround time and little to no clean-up time required between molds, the Reusable Bag Molding process is an efficient alternative to traditional molding methods.

How Does the Reusable Bag Molding Process Work?

The Reusable Bag Molding process can be simplified into a series of steps that allow the resin injected into the bag to set and form the desired mold. This process is completed as such:


Step 1: A mold is created with one rigid base side (side A) and one flexible side (side B). Side B is often created using silicone, latex or other rubber-like material.

Step 2: The base mold is filled with fiberglass, and other materials like gel coat, core, etc., and the reusable bag is placed on top. Once the bag is properly in place a vacuum is applied to insure a secure seal.

Step 3: Using a low pressure injection pump, catalyzed resin is injected into the mold.

Step 4: Once the resin is cured, the part is de-molded and trimmed for further production.


This is a highly simplified description of the Reusable Bag Molding process; a more detailed description can be found in this demo video. Some of the advantages of the Reusable Bag Molding process include:


  • Low tooling costs
  • Reusable and repairable bag
  • Environmentally conscious with significantly lower HAP emissions


Because of the simple technology involved in the Reusable Bag Molding process, this technique is easy to explain when training new employees.

Composites One is the Leading Supplier of Composites

Composites One is named one of the thought leaders in the composites industry. Known for bringing the latest processes and material available in the composites industry, we continually strive to educate manufacturers about cutting-edge processes that can save time and money. To learn more about the latest processes, view our process news section at