Silicone Injection Molding: What is it?

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Silicone injection molding is a cost-effective process used to produce a wide range of silicone products, including gaskets, insulators, and baking pans. Liquid and fluoro silicone rubbers are commonly used, and the process involves mixing resins, a catalyst, and a coloring agent before injecting the mixture into a mold. The process offers benefits such as stability in various environments and temperature ranges, making it suitable for industries such as aerospace, energy, and healthcare.

Silicone injection molding is an inexpensive and widely used industrial process for manufacturing a wide variety of silicone products. These include gaskets for aerospace applications, sealing membranes for industrial use, insulators for electrical connections and even baking pans and spatulas. Silicone rubber products are mass produced using machines of various sizes.

The main types of silicone rubbers are liquid silicone rubber (LSR), fluoro silicone rubber (FSR), high consistency silicone rubber (HCR) and fluoro liquid silicone rubber (F-LSR). While all variants of this thermoset elastomer family are used with the injection molding process, LSR and F-LSR can only be formed by injection molding. Silicone injection molding is used to make products for a wide variety of industries, including agriculture, aviation and aerospace, energy, and medical and health care.

The basic idea in any injection molding process is for a machine to mix two component resins together along with a catalyst and, often, a coloring agent. The machine will then force the mixture into the mold where it will cure, setting the shape of the mold. Typical machines used for silicone injection molding have six essential parts: injectors, dosing units, feed drums, mixers, a nozzle, and the mold clamp.

The injectors pressurize the silicone rubber into the pumping section. The operator can adjust the pressure and pumping speed to the best level for the product to be made. The dispensers pump the component resins in carefully controlled portions, simultaneously releasing them at a constant ratio. The feed drums contain the resins; often another drum will contain pigment.

The components are pumped into the mechanical mixer, where they are mixed. After mixing, the LSR or F-LSR is forced through the nozzle into the mold. The nozzles usually have automatic shut-off valves to prevent overfilling or leaks. The die clamp is a device that is activated in coordination with the injector, pump and feed units. It fixes the mold in place and opens it when the product has hardened.

Silicone injection molding offers many benefits to the manufacturer and consumer. Silicone products remain stable when exposed to the elements, ozone and ultraviolet rays. Conversely, organic elastomers tend to become brittle and break down after prolonged exposure to the environment. Silicone rubber products can function properly in temperatures as low as -140° F (-100° C) or up to 600° F (316° C). They remain good electrical insulators and retain a high percentage of their flexibility and resilience over most of that temperature range.




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