Compression Molding: How It Works

Compression molding is a standard process used to make stock shape thermoplastic and thermoset materials and parts. Broadly speaking, you put a pre-heated plastic material into an open, heated mold cavity. The mold is then closed by a hydraulic press and compressed. This ensures the content in the mold comes into contact with all areas of the mold within an airtight cavity.

To find out more about compression molding, continue reading…

Tell Me More

Three-dimensional materials and parts are of different lengths, thicknesses, and sizes. They are very strong and so useful for all kinds of industries—one industry that commonly uses this to produce high volume parts is the automotive industry.

Once the materials are in the mold cavity, heat and pressure are applied to make the material in the mold harden. The mold temperature is typically 350°F, and mold pressure is 100 psi (180°C and 700 kPa) with a curing time of 3 min. Once it’s hardened, the material is removed from the mold.

The Materials Use Compression Molding

Compounds such as:

  • Melamines
  • Polyesters
  • Phenolics

That’s as well as other types of resins are used in the process to create the final product. Different kinds of thermoplastics are also compression molded.

The Advantages of Compression Molding

There are notable advantages to using this process when creating parts for industry. Namely, it’s economical because it can produce high volume parts at a high-quality. It’s worth noting that tool costs are also relatively low. As such, compression molding is an effective way of producing robust and light parts that are more resistant to corrosion than metal

The Disadvantages of Compression Molding

It’s fair to say; this process is suited to particular types of industries that need to create stock shapes and parts. That said, there are downsides:

  • It can be a slow process which may impact production times when high volume is a necessity
  • You have to get the heat right.

If the plastic polymer isn’t hot enough, it may not fill the mold cavity. If it’s too hot, it may create too much pressure and need a longer cooling time.

Four Simple Steps to Compression Molding

You can summarize the compression molding process in four simple steps:

  1. A reliable metal tool is made that matches precisely the measurements needed to produce the desired part. This is then inserted into a press and heated.
  2. The desired composite is made before inserting it into the tool.
  3. The composite put into the heated mold. Depending on how thick the part you’re making is, a process of compression using high pressure now takes place.
  4. Once the pressure is released, the part you’ve created is removed from the tool. If there’s any resin around the edges, this is got rid of.

Ready to Start Using Compression Molding?

We hope to have read this article; you now have a better idea of how compression molding works.

SMI Composites uses the compression molding process to create materials used across a variety of industrial needs. We have a comprehensive range of options – especially if you need to produce high volume parts. Contact us today for more information on the services and products we can provide for you. Speak soon!

About the author