Injection Molding
Injection molding is a cost-effective manufacturing process for creating high volumes of consistent molded seals and gaskets with a flash-free finish.
What Is Injection Molding?
Developing the mold, often from aluminum or steel, is the initial step of the injection molding process. We machine the mold to mirror the precise desired features for the final seals and gaskets. Once the mold is ready, we feed uncured elastomeric polymers into a heated barrel, where a helical-shaped screw mixes the material as it heats. This transforms the contents into a molten material that is then injected into the cavity of the heated mold. As the material vulcanizes, it takes the mold’s shape, thus creating a finished component. When vulcanization is complete, the plate mold’s platens open up and the parts pop out with the help of ejector pins.
When to Use Injection Molding for Seals and Gaskets
Injection molding rubber is ideal for high-volume manufacturing, producing parts in the thousands. The process is capable of generating highly intricate components, but to do so also necessitates complex tooling. This results in higher initial costs and longer setup times, making the process more cost-effective for larger production runs. Injection molding is also well-suited for producing smaller components of almost any polymer and durometer.
Advantages of Injection Molding for Seals and Gaskets
The injection molding process allows for uniform seals and gaskets with tight tolerances, even at rapid production speeds, with little to no finishing required due to the lack of flashing. In turn, this consistency equates to high product reliability in injection molded gaskets and seals. The superior cycle times of the molding process itself allow companies to quickly and cost-effectively scale production for lower per-part costs on these molded components.
Compression Molding
Compression molding is another available manufacturing process, rapidly and affordably generating large seals and gaskets.
What Is Compression Molding?
While compression molding is similar to injection molding, it utilizes compressive force on a set amount of elastomeric molding material, or charge, already placed in the mold. As the mold closes around the material, the controlled heat and compression of the material create components in the mold’s shape as it cures. Once they are released from the mold, compression molded seals and gaskets typically require additional trimming and cleaning.
When to Use Compression Molding for Seals and Gaskets
Compression molding is ideal for components that can be easily and quickly loaded into a normally less expensive tool. While it can still create intricate parts, it’s best for runs ranging from low to average volumes.
Advantages of Compression Molding for Seals and Gaskets
Compression molded seals and gaskets offer a cost-effective approach and generally lower tooling costs. The molding process achieves rapid manufacturing for large components and is compatible with a wide range of materials as well for greater versatility. Compression molding also allows for solid molded seals and gaskets with few knit or flow lines. Compression molded seals and gaskets have very high structural stability, are dimensionally accurate, and have controlled durometers within ±5.
Choosing the Right Material for Your Application
Injection and compression molding processes are compatible with an array of material options, the most common of which are:
- Nitrile. Nitrile is a synthetic rubber that offers good resistance to acids and alkalis as well as abrasion and chemicals. It can withstand temperatures ranging from -60 to 250° F, and the material offers good resistance to compression set.
- Ethylene Propylene Diene Monomer (EPDM). This synthetic rubber has a working temperature range of -60 to 300° F. It’s flexible, durable, and possesses good acid resistance, with excellent resistance to alkalis.
- Viton®. This particular brand of Fluorocarbon (FKM) operates in temperatures ranging from -20 to 400° F. Of these common materials, it offers superior acid and chemical resistance, with average resistance to alkalis and good compression set. We also work with all three families of this material and choose based upon application.
- Silicone. Delivering flexibility and good mechanical properties, silicone provides particularly impressive thermal resistance. The material maintains its integrity from -100 to 450° F. It’s also highly resistant to alkalis, with superior resistance to compression set.
- Neoprene. Neoprene is another material option, with a temperature range of -45 to 250° F. With average resistance to compression set and resistance to alkalis, this synthetic rubber withstands tears and holds up well against oils, solvents, UV light, and the elements.
These materials give us the versatility to create molded seals and gaskets for virtually any temperature, pressure, or pH condition.
Contact MPRC for Molded Seals and Gaskets
Although injection and compression molding are similar in their use of heat and pressure, they vary in their exact procedures, results, and optimal applications. By understanding the differences between the two main processes, and by partnering with a company specializing in custom seal and gasket solutions, you are ensured of receiving quality products that fit your unique application.
Master Packing and Rubber Company has been solving customers’ sealing challenges since 1982, providing various industries with a wide range of custom molded seals and gaskets. Through innovative, computer-simulated design analysis and quality materials, the MPRC team develops real solutions for customers from design and engineering through manufacturing and shipping. We carefully analyze application and environmental exposures to create ideal sealing solutions using the best materials and molding manufacturing techniques to ensure high-performance products and customer satisfaction.
Contact us to learn more about our molded seal and gasket options, or request a quote today for your custom product.
