Compression Molding

process

A molding process where preheated plastic material is placed in an open mold cavity, then compressed under heat and pressure until it conforms to the mold shape and cures.

In Simple Terms

Think of compression molding like making a waffle - you place the plastic material in the bottom half of a heated mold, close the top half, and apply pressure. The heat and pressure force the material to flow and fill the entire mold cavity, creating the final part shape.

Why It Matters

Compression molding is essential for producing high-strength thermoset parts with excellent surface finish and dimensional accuracy. It's particularly valuable for thick-walled parts and applications requiring superior mechanical properties that injection molding cannot achieve.

Technical Details

The process typically operates at 150-200°C with pressures of 10-100 MPa. Cycle times range from 1-30 minutes depending on part thickness and material cure characteristics. Critical parameters include mold temperature uniformity, compression force distribution, and material preheating temperature to ensure proper flow and cure.

Real-World Examples

Thermoset SMC automotive panels

Sheet molding compound is compression molded into automotive body panels, hoods, and structural components requiring high strength-to-weight ratios and Class A surface finish.

BMC electrical components

Bulk molding compound is compression molded into electrical housings and insulators where flame retardancy, dimensional stability, and electrical properties are critical.

Rubber gaskets and seals

Elastomeric compounds are compression molded into O-rings, gaskets, and seals where precise dimensional control and chemical resistance are required.