Manufacturing Silicone Rubber Parts

Silicone is one of the most popular elastomers used in manufacturing. It is a flexible material that resists harsh environments and can hold its shape at high temperatures.

Like most materials, silicone must be prepped before it can be molded. At WayKen, we use modern rapid prototyping technologies to create a master pattern for our silicone rubber molds.

Compression Molding

Compression molding is a manufacturing technique that uses heat and pressure to create molded parts. The process begins with the fabrication of a mold from a 3D printer or CAD software. Then, a raw material is placed in the mold and heated and pressurized. The resulting molded part is cured through a chemical reaction called crosslinking. The resulting cured product is strong, durable, and long-lasting.

Both thermoplastics and thermosets are compatible with compression molding. In the case of silicone rubber, this process produces extremely durable molded products that resist cracking and breakage. The cured silicone can maintain its physical properties across a wide range of temperatures, making it ideal for electrical insulation and aerospace applications.

In addition, compression molding provides a high level of versatility for complex and simple projects Silicone rubber parts alike. It is particularly useful for manufacturing high-performance materials that are not easily fabricated with other methods, such as carbon fiber composites.

The molding process utilizes a preform or charge that is typically a fiber-reinforced resin material, such as polyaryletherketones (PAEK) and polyetheretherketoneketones (PEEK). The mold is then closed under a programmed speed and temperature, creating an irreversible chemical reaction known as crosslinking that creates the final molded part. The molded product is then ejected from the mold and any excess material that remains, commonly known as “flash,” must be removed manually or by an automated deflashing process.

Liquid Silicone Rubber (LSR) Injection Molding

Liquid silicone rubber (LSR) injection molding allows manufacturers to build a wide variety of parts and seals. Durable and resistant to extreme temperatures, LSR provides reliable qualities for parts in automotive applications and other high-performance environments. It resists ozone, weathering and chemical solutions including acids and alkalis. LSR is crosslinked by a platinum-catalyzed reaction and, unlike thermoset plastics, it does not degrade at elevated temperature.

LSR injection molding uses the same principles as other injection molding processes, though there are a few differences. For example, production tooling for LSR is more complex than injection molds for thermoplastics, as LSR can flow into very thin wall sections and tight radii. The tooling must also be designed to minimize parting lines, as LSR can shrink and flash more easily than a typical thermoplastic component.

During the meter/mix/dispense phase of the molding process, a metering unit pumps the two primary liquid materials, ensuring that they maintain a constant ratio and are released simultaneously. These materials are then combined by a static or dynamic mixer, then deposited into the mold through a nozzle. A combination of heat and pressure then cures the molded material until it solidifies.

Once a cycle is complete, the mold clamps and the part and flash are removed with an automated robotic or, for smaller production runs, manually by a worker. Like other injection molding techniques, proper part design is important to avoid re-molding and quality issues.

Water Jet Cutting

Using a mixture of water and abrasive particles, the high pressure of a waterjet cutting machine allows it to cut through virtually any material. Waterjets are used for cutting metals like steel, aluminum, and titanium as well as soft materials such as dense foams, components for automobiles, and rubber.

A key advantage of the water jet cutting process is that it is a cold cutting technique and does not leave heat-affected zones or create stress on the final product. It also produces smooth, burr-free surfaces that eliminate the need for secondary finishing. The waterjet cutting method is being used to cut a variety of materials including the soft, porous types of silicone rubber, which are a good fit for this technology.

For complex 3D workpieces, a sacrificial material must Silicone Rubber Parts – Supplier be placed inside cylinders or in narrow holes to prevent the waterjet stream from contacting an opposing face of the material after it cuts through the original side. This is not an issue for a flat or 2D workpieces.

The ability to perform 5-axis cutting (Y back and forth movement, X left and right movement, and Z up and down movement) makes the waterjet a popular tool in the manufacturing industry. It can take a CAD model and produce a cut program within minutes and provide extreme precision that is hard to beat with other cutting methods.

Sheet Molding

If you manufacture glass-reinforced plastic (GRP) products, it’s likely that you have worked with sheet molding compound (SMC). This material has enjoyed something of a renaissance in recent years, thanks to its unique and versatile properties.

SMC is a form of prepreg used for making GRP composites by the compression molding process. It is made from a mixture of unsaturated polyester or vinyl ester resins and chopped fiberglass reinforcement. The fibers are impregnated in the resin and then compressed into a mold by a heated plug. This compression creates the final shape of the part and also cures the SMC.

Unlike other prepregs, which are usually cold-stored until they can be molded, SMC is already cured and ready to be used when it’s delivered. This makes it a popular choice for high-volume production of GRP components like class A automobile body parts and business equipment cabinets.

SMCs use a combination of specialized resins and fillers to achieve specific processing and performance characteristics, such as low viscosity. They also contain short-length fiberglass strands to provide strength and stiffness, and can be designed for a wide range of applications and manufacturability. For instance, IDI offers a line of SMCs with carbon-fiber reinforcement for exceptional strength and severe weight restrictions. This material is ideal for a variety of automotive and other applications, including interior components that require excellent surface appearance and electrical insulation.