How Does Compression Molding Work?

Compression molding is a molding process that involves the use of a heated and pressurized plastic polymer material to create three-dimensional objects. From rubber boots and shoes to automotive fenders and spoilers, it’s become a common process in the manufacturing industry. However, compression molding differs from other molding processes by relying on pressure to completely fill the mold with plastic. To learn more about compression molding and how it works, keep reading.

The Basics of Compression Molding

To perform compression molding, a manufacturing company first heats the plastic polymer — typically granular or pellet plastic polymer — after which the polymer is inserted into the cavity of a mold. Next, the manufacturing company closes the top of the mold with plug. After closing the mold, the manufacturing company pressurizes the mold through the plug, allowing the heated polymer to expand and fill the mold’s cavity.

While the plastic polymer used in compression molding is generally heated before it’s inserted into the mold, the mold is also heated to encourage expansion. The combination of both pressure and heat makes compression molding a highly effective molding process in the manufacturing industry.

Compression Molding vs Injection Molding: What’s the Difference?

Injection molding and compression molding are two similar molding processes that involve forcing heated and pressurized plastic polymer into the cavity of a mold. With that said, they aren’t necessarily the same. Compression molding begins with the extrusion of a plastic workpiece, which is typically heated and cut before it’s inserted into the mold’s cavity. In comparison, injection molding begins with heating and injecting the plastic polymer into the mold’s cavity.

Factors That Affect Compression Molding

As with other molding processes, several factors can affect the performance of compression molding. If the plastic polymer isn’t heated to an appropriate temperature, for example, it may fail to fill the mold’s cavity. If the plastic polymer is heated too much, on the other hand, it may create an excessive amount of pressure while requiring a longer cooling time. There are also different heating methods available for compression molding, which can affect the performance of this molding process.

To recap, compression molding is an advanced molding process that involves heating plastic polymer, followed by forcing the plastic polymer into the cavity of a mold. It’s a popular choice among manufacturing companies because of its ability to mass-produce plastic products and objects while creating minimal waste in the process.