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How Does Compression Molding Differ From Other Molding Process

The choice between compression molding over other molding processes has been a point of contention for many manufacturers. All of these manufacturing processes have their advantages and disadvantages and choosing the right fit will depend on the product requirements.
To know why compression molding is reigning supreme over the rest means that we have to take a deep dive into what compression molding is all about.

An In-Depth Look at Compression Molding

The compression molding process features the use of a heated mold treated with pressure. Just like in the other molding process, it also uses the same materials, typically a polymer or plastic and a mold cavity. When the material hardens, the product will be removed from the cavity. What makes it unique is it uses both the capabilities of pressure and heat. When both of these variables are added to the production process, it alters the properties of the molded material.
The compression molding process begins with heating the material and the mold cavity. When the desired temperature is achieved, the material will be introduced into the mold. Using heat alone can cause the heated material to expand. The use of pressure in compression molding makes it an effective process.
To apply the pressure, the molded cavity with the molten material will be properly sealed with a plug. The pressure is then exerted so that the material fills all the smallest crevices in the mold. In some processes, the pressure can reach up to 2,000 pounds per square inch or PSI. When this pressure combines with heat, the pressure will push the materials throughout the cavity.
When the materials cooled down, the final product will then be removed from the cavity. While other molding processes are the same, the pressure makes all the difference in compression molding.

The Advantages of Compression Molding

Compression molding is ideal when creating durable products. Here are the rest of the benefits of using this molding process.
1. Seamless Design - The compression molding technique can make products with different wall thicknesses. It can vary from 1.3 millimeters to one inch.
2. Lower Costs – When used in low-pressure molds, producing multiple cavities incur lower costs.
3. Varied Options for Materials – In compression molding, you can use materials that stay pliable after the cooling process. Some of the most common materials used are natural rubber, silicone, and EPDM.
4. Seamless Design – The final product in compression molding is seamless without knitting or flows. Some of the products it can produce is a gasket that has a cohesive characteristic and with a good surface finish.
5. Fit for High Volume Manufacturing – Compression molding has longer production time, but it’s a low-pressure mold, so it has inexpensive tooling costs.

Drawbacks from Compression Molding

Here are the disadvantages of using compression molding:
1. Slower Turnaround Time – The time it takes to complete a compression molding cycle is much slower than other molding processes.
2. Higher Labour Cost – In compression molding, it is necessary to remove flash, which translates to additional manpower requirements.
3. Lower Productivity – Removing the flash lowers down the productivity because it slows down the production.
4. Production of Simple Parts – This technique is best for parts with simple geometry.


Compression molding has its benefits and drawbacks that companies should consider before going into production. The manufacturer has to select a technique that best suits their requirements.

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