Compression Moulding
Compression molding is a method where GRP composite materials are shaped under high pressure in a mold. The process starts with placing a mixture of fibers (like chopped glass fibers) and thermoset or thermoplastic resin into the mold. The mold is closed, and pressure, typically ranging from 3.5 MPa to 70 MPa, is applied to compress the material into the desired shape. Simultaneously, the mold is heated to temperatures between 120°C and 180°C, causing the resin to flow and cure.
The fiber content in compression molding typically ranges from 20% to 50% by weight, depending on the application. The cycle time for each part can range from 1 to 5 minutes, making the process suitable for high-volume production. The molds are made of hardened steel or aluminium, ensuring dimensional precision with tolerances as tight as ±0.1 mm.
Compression molding can create complex, high-strength parts with uniform wall thicknesses, typically between 1 mm and 10 mm. The process is capable of producing parts with high structural integrity, offering tensile strengths of up to 1000 MPa and flexural strengths of around 1500 MPa. Since the material flow during molding is controlled, the method yields parts with excellent surface finishes and minimal post-processing.
Compression molding is widely used in the automotive industry for producing body panels, under-the-hood components, and bumpers, which must meet high strength and impact resistance standards. For example, components like headlamp housings may need to withstand forces up to 1000 N without cracking. It is also used in aerospace for interior panels and the electrical industry for making switchgear parts that require electrical insulation up to 35 kV. In the consumer goods sector, it is used to make durable parts like plastic furniture.
