As stated in its name, compression molding uses the force of compression as well as heat, to shape large raw materials into actual molds. The process of this injection molding technique involves heating a given plastic material to the point of it being pliable, compressing it into its desired shape, and then curing it, ensuring that it keeps its proper dimensions.
Most Common Plastic Materials Used in Compression Molding
The two most common raw plastic materials used for compression molding are thermoplastics and thermoset plastics. Unlike thermoset plastics, thermoplastics can be heated and reheated as much as needed, while thermoset plastics can only be heated and shaped on the first go around.
Most Common Mold Types Used In Compression Molding
Straight- Does not require definitive dimensions of product. Needs removal of flash.
Landed- Must have accurate dimensions of product. Does not need removal of flash.
Flash- Must have accurate dimensions of product inserted into the mold. Requires removal of flash.
The Process of Compression Molding
Regardless of which plastic material or mold is used, it’s important to allow that material to cover not only the entirety of the molding surface, but also any nooks and crannies within the mold, to make sure that the material is distributed evenly.
Starting with material being placed into the actual mold, the material is then heated to the point of pliability. At this point, a hydraulic tool presses firmly against the mold, shaping it into its desired dimensions as shown in this image below featuring plastic pharmaceutical packaging containers.
The Basics To Consider
When using compression molding, there are several factors that need to be considered by an engineering team prior to production:
- Calculating the exact amount of raw material needed
- Calculating the proper time allocation required to heat the material
- Calculating the minimum amount of energy needed to heat the material
- Determining the proper heating technique
- Calculating the required force application needed to ensure that the mold attains proper shape
- Designing the mold for cooling after the material has been compressed
What Kinds of Products Are Made Using Compression Molding?
First developed in the manufacturing of composite parts for metal replacement applications, compression molding was designed to make large flattened parts or slightly curved parts. Due to the nature of its high volume, high pressure processing, as well as the durable materials used within production, compression molding was adopted early on by the automotive industry for the manufacturing of small intricate automotive parts, as well as spoilers, fenders, scoops, and hoods, just to name a few.
Advantages of Compression Molding
Taking into consideration the various ways that products can be massed produced, compression molding offers companies a low cost and efficient strategy for producing plastic goods. Compression molding is one of the least costly ways in mass producing products. Aside from it’s efficiency, the process leaves little energy or material wasted post use and is great for companies that require high volume products.