Compression Molding Explained: Key Processes and Tools

While there are different techniques for compression molding, there are usually four main steps involved. For starters, specialized tooling is often needed to mimic the same geometry and dimensions as the engineered drawing. Typically, tooling may consist of a bottom mold and a top mold machined from aluminum or steel. However, hydraulic presses can also be integrated into the process depending on the overall design requirements and features. Once the tooling has been successfully developed, a specific level of raw materials is introduced into the bottom mold cavity. While many materials can be used in compression molding, such as thermoplastics, this manufacturing process is ideal for thermosets like polyurethanes. Afterward, the top mold with matching geometries is placed on top as the material begins to cure. A hydraulic press may be used at this time for additional pressure to prevent material from overflowing, creating a uniform part with minimal to no flash. The mold is kept tightly sealed for a specific period, enabling the material to cure fully into the final shape. Ultimately, the upper mold or hydraulic press is removed, and the final product is demolded. Depending on the tool design, compression molding can take on most complex shapes, patterns, and textures. Additional design features, such as inserts, can be molded-in or included as a secondary step.