Compression molding is one of the most common processes used to mold plastics into a usable form, and it is also one of the most cost effective. Most often, compression molding is used to create a wide variety of parts and components ranging from compression molded car parts to medical products.
The first commercial foray into compression molding was in 1847, when the technology was used to create hand mirror frames and other domestic products. Later, the then primitive process was completely overhauled in the 1930s when the first compression molding machine was created giving way to increasingly more modern machines and eventually leading to the level of speed, efficiency, and precision we expect from products today.
This technology of manufacturing is especially used when the density and material type required must remain uniform throughout the part. It will also have no moving parts, and will be molded all at once. However, many small compression molded parts are often assembled together to form larger machines like automobiles. For the right industries, compression molding has proven that it is one of the most effective and efficient methods for creating certain products, and this has remained true for years. Some examples of compression molding parts and products include everything from ash trays and appliance knobs to vehicle panels and radios.
In basic terms, compression molding is a simple process where plastic is heated and pressed into the required shape. Compression molding is typically done with thermosetting materials. While thermoplastics remain capable of melting when subjected to heat, thermosets are used because they do not soften with heat and retain their molded form. In compression molding, technicians use a hydraulic press to force the liquid plastic material into a mold shaped like the desired product. When the material inside cools, the mold is removed from the mold in the proper shape, excess plastic is trimmed away, secondary operations and finishing are completed, and the part or product is either ready for sale or use as a component in a larger product.
Compression molding comes with a variety of advantages ranging from low cost moldings and lower labor costs to less shrinkage and a high level of repeatability. Additionally, due to the extremely small amount of material that gets wasted, manufacturers can afford to use more expensive plastic compounds in their products. Some of the downsides to compression molding include somewhat lower product consistency than other methods, uneven lines, and less flexibility when it comes to the depth of the mold. Regardless, for certain parts and products compression molding is a fantastic technology that has been and will continue to be a stable in the industrial community.