Compression molding is a molding method that utilizes custom machined molds to form parts and products from uncured rubber or plastic. The process involves placing the material into the open mold cavity, closing the mold, and applying heat and pressure to shape and solidify the material into the desired component. It can be used to turn a variety of designs into tangible objects for a wide range of industries and applications. However, while it is an ideal production solution for many projects, it is not suitable for all of them. 

Below, we highlight the key advantages and disadvantages of the compression molding process to help you understand if this is the right solution for your needs. 

Advantages of Compression Molding

There are many advantages to choosing compression molding for a rubber or plastic component manufacturing project, including, but not limited to, the following:  

It is a simpler process.

The compression molding process is relatively simple and straightforward compared to other molding and manufacturing processes. For some part designs this makes it easier for operators to perform, which translates to lower overall production costs. 

It involves lower tooling costs. 

Compared to injection molding, compression molding does not require special equipment and expensive complex tooling.  As a result, the equipment and tools required for the operation are much simpler, which typically means less capital investment.  Although it is a labor intensive process, when handled correctly, the wear and tear sustained by the molds during operations is relatively small, which can mean less maintenance needed over time, resulting in lower cost quotes for customers. 

It is great for producing large items and thicker parts.

As the compression molding process involves loading the material directly into the mold cavity, it is not subject to part weight limitations except for those imposed by the part design, and equipment (e.g., size and pressure capacities). As a result, it can usually handle the larger amounts of raw material needed to create bigger parts and products. 

It can be a good choice for insert molding and multi color molding.

Done in a vertical compression press with the right approach to tooling this process lends itself to some types of insert molding and dual color molding without the high cost of special equipment, very expensive tooling,  high set-up and material costs used in liquid injection molding of silicone

It is cost-effective for short production runs.

Due to its lower tooling and setup costs, compression molding is ideal for small to medium production runs. It is often used to create prototypes or samples of designs before proceeding to large-scale production. 

Disadvantages of Compression Molding

While the compression molding process carries many advantages for customers looking to start a new part production, it also has a few disadvantages, such as: 

It has a higher chance of post molding costs. 

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The size (projected area) of the part and its weight must be carefully calculated in relation to the  force available  from the press used to shut and hold the mold closed during a molding cycle.  Even if this is optimal expect more parting line flash and and parting line control issues that may need to be dealt with by hand trimming or nitrogen de-flash of the parts adding cost.

It has slower processing times.   

Compared to injection molding, compression molding requires more time to bring materials to cured state. These slower processing times can affect production rates and costs in higher volume projects. 

It is not suitable for all complex designs. 

The material used in compression molding operations may be subject to some limitations of flow within the mold cavity. As such, it may not reach into more intricate portions of the mold and tooling revisions may be needed to fill some parts. This quality makes the process unsuitable for some complex part and product designs. 

Elastomer Technologies, Inc.: Your Partner for Compression Molding Needs

Compression molding can be an effective and efficient manufacturing solution for many projects. By understanding the unique advantages and disadvantages it carries compared to other available solutions, you may find that it is the ideal solution for your project. 

Equipped with over 30 years of experience providing precision molded and die cut components to customers in a wide range of industries, the team at Elastomer Technologies, Inc. has extensive knowledge on compression molding and tailoring the process for each project. Check out our compression molding page to find out how we can benefit your next project.  

To learn more about compression molding and if it’s right for your needs, contact the experts at ETI today.