Rubber Moldings: What Are They and How Are They Made

Rubber moldings include seals, gaskets and other custom molded rubber products made from elastomers that provide high durability and elasticity. Precision molded rubber products are ideal for indoor and outdoor sealing because they can withstand a wide temperature range and return to their original shape after being distorted.

Examples of industrial molded rubber products include:

  • Aircraft gaskets
  • Automotive seals
  • Bellows
  • Chemical resistant seals
  • Grommets
  • Industrial gaskets
  • Window seals

Standard Processes for Rubber Moldings

Industrial molded rubber products are created using various processes and a wide range of rubber materials. Standard processes include compression, injection, and transfer.

Compression Rubber Moldings

During this molding rubber process, raw rubber materials or compounds, known as pre-forms, are placed into molds that have a top plate and bottom plate. As the plates are pressed together, the rubber fills the mold cavity with excess flowing into overflow grooves. Once the molding process is complete the rubber moldings are taken out of the mold and the excess flash is removed.

This process is suitable for smaller production runs as it has lower tooling costs than other methods, making it an economical molding process. Compression rubber moldings require deflashing and are best suited for medium hardness compounds. They are not ideal for complex or intricate shapes.

Injection Rubber Moldings

Injection molding is a process where heated rubber is injected into a mold containing a series of cavities. The process reduces the need for pre-formed rubber and therefore, has a reduced cycle time. It is also ideal for more complex designs because the heated material flows easily into the cavities.

This process is suitable for medium to high volume production runs, has a shorter production time, and is ideal for complex shapes and intricate designs.

Transfer Rubber Moldings

The transfer molding rubber process is similar to compression molding in that pre-forms are used instead of heated rubber. There are, however, some differences in the two processes. During transfer molding, the pre-forms are placed into a top portion of the mold known at the pot. As the mold closes, the rubber is compressed and forced through a sprue and into the mold. Once formed, the custom molded rubber products are deflashed and the excess rubber is discarded.

This process is suitable for medium to large production runs as it is cost-effective and reduces tooling and production. It can accommodate high cavity counts and allows for tight tolerances. Furthermore, transfer moldings can be used for overmolding.

Specialty Processes for Rubber Moldings

Our standard molding rubber processes can be further customized to create rubber moldings designed for high demand applications via fabric reinforcement or rubber-to-metal bonding.

Fabric Reinforced Rubber Moldings

This method of molding involves adding a layer of fabric to the rubber moldings to increase durability and longevity. The fabric is layered into the mold first, then rubber is compressed into the mold to bond the two materials.

Fabric reinforced custom molded rubber products feature higher tensile strength and abrasion resistance than standard rubber moldings, making them ideal for aerospace and other demanding applications.

Rubber-to-Metal Bonded Rubber Moldings

Rubber-to-metal bonding is a molding rubber process where rubber is bonded onto a metal insert. To form the bond, the metal inserts are coated in adhesive and then placed into a mold. After the mold closes, heated rubber flows around the metal insert and attaches to the adhesive. The rubber-to-metal molding process is used for applications requiring both flexibility and stability and can be used for both large and small components.

Contact us to learn more about custom molded rubber products created using a range of processes and materials or request a quote.

NW Rubber Extruders