The injection molding of liquid silicone rubber (LSR) is a highly automated and precise manufacturing process, and its core principle is completely opposite to that of thermoplastic injection molding. Thermoplastic solidifies in a cooled mold, while liquid silicone rubber solidifies into a highly elastic solid component by injecting cooled liquid raw materials into a high-temperature mold and triggering a chemical reaction through thermal activation.

The entire injection molding process begins with precise measurement and mixing of raw materials. Liquid silicone rubber is usually composed of two components, A and B, which respectively contain platinum based catalysts and crosslinking agents. A specialized precision metering pump extracts these two liquids in a strict 1:1 ratio and mixes them thoroughly and bubble free through a static mixer. The mixed rubber material is fed into the cooling cylinder of the injection molding machine to slow down its reaction rate and prevent pre curing before injection. Subsequently, under high pressure, the rubber material is rapidly injected into the closed high-temperature mold cavity through a heating nozzle and a cold runner system. The role of the cold runner system is crucial, as it ensures that the rubber material inside the runner remains at a low temperature until it enters the mold, thereby minimizing material waste to the greatest extent possible.

Liquid silicone rubber injection molding has unique technical requirements in mold design and temperature control. There are heating channels inside the mold, usually using hot water or hot oil to maintain the mold temperature between 160 and 200 degrees Celsius. Due to the extremely low viscosity and fast filling speed of liquid silicone rubber, the mold must be designed with an extremely precise exhaust system or equipped with a vacuum device to prevent air retention from causing bubbles or missing glue in the product. In addition, the shrinkage rate of liquid silicone rubber after demolding and cooling is usually between 2% and 3%, and it exhibits the characteristics of thermal expansion and cold shrinkage. Therefore, precise shrinkage rate compensation must be carried out in mold size design.

In the demolding and post-processing stages, due to the excellent flexibility and high-temperature tear strength of liquid silicone rubber, the cured product can be easily peeled off by demoulding, ejector pin or compressed air, and even without the need to design a draft angle. For high demand applications such as medical or food grade, the demolded parts usually need to undergo secondary vulcanization (post curing), that is, continue heating in a high-temperature oven for several hours to thoroughly evaporate residual low molecular substances and further improve the mechanical strength and chemical resistance of the material. This injection molding process not only has a short production cycle and minimal waste, but also can perfectly replicate complex structures at the micrometer level, making it an ideal choice for large-scale, high-quality elastic component manufacturing.