Background

Liquid silicone rubber and the silicone compression molding process play a pivotal role in the manufacturing process of a broad range of industries. This manufacturing process changed the very nature of the manufacturing world. It made the fabrication of a wide range of parts for just about every industry imaginable possible. The fabrication process allows for a high productivity level, due to quick cycle time.

Product designers, engineers, and managers have the challenge of choosing a high-quality elastomer for a variety of critical applications, including medical devices, aerospace, and automotive components. These professionals must make a critical assessment of an array of material properties and processing capabilities to best determine which options meet their demanding performance specifications and budget requirements.

The versatility of the silicone mold-making process allows manufacturers to create parts featuring different colors, textures, shapes, and mechanical properties with highly detailed surface finishes. In many cases, Silicone Compression Molding produces parts that are as strong — if not stronger than — parts made with injection molding, with greater abrasion and chemical resistance as well.

This makes Compression Molding an excellent manufacturing method for producing rubber and plastic parts with joints, logos, and overlapping features, or parts that require high flexibility. This includes applications like electronics coverings, medical equipment, wheels, robotics, and conveyor systems.

The Process

Compression molding is the process of placing un-vulcanized LSR material into the cavity of each half of the mold. The mold is then assembled, placed into a heated compression molding press, and cycled. Silicone is vulcanized through this process and a part is formed. This process application yields quick turns on prototype or R&D phase parts as well as less costly tooling upfront.

Materials

1. Liquid silicone rubber (LSR)

Liquid silicone rubber (LSR) is a high purity platinum cured silicone with low compression set, great stability and ability to resist extreme temperatures of heat and cold ideally suitable for production of parts, where high quality is a must. Due to the thermosetting nature of the material, liquid silicone injection molding requires special treatment, such as intensive distributive mixing, while maintaining the material at a low temperature before it is pushed into the heated cavity and vulcanized.

Chemically, silicone rubber is a family of thermoset elastomers that have a backbone of alternating silicon and oxygen atoms and methyl or vinyl side groups. Silicone rubbers constitute about 30% of the silicone family, making them the largest group of that family. Silicone rubbers maintain their mechanical properties over a wide range of temperatures and the presence of methyl-groups in silicone rubbers makes these materials extremely hydrophobic, making them suitable for electrical surface insulations.

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