RPM Industries LLC
Rubber Compression Molding Process

Rubber Compression Molding Process: From Start to Finish

If you need rubber compression molding services, it is imperative that you hire the right company. It is also advantageous to learn what the different steps of the rubber molding process are. By doing so, you will realize the many advantages of compression molding are critical for your business and your customers. However, learning about this process will also help you understand how rubber compression molding defect occur.


Steps for Rubber Compression Molding

The company that you hire will help you select the appropriate rubber material based on the product that you need. For controlling the shape and weight of the product, the uncured rubber is preformed and then placed directly into the mold cavity. Once the mold closes, the rubber material compresses between two plates that force the compound to flow, thereby filling the cavity.


The rubber material remains pressed with the right amount of pressure and at the correct temperature, which allows the cure system in the compound to activate. The professional operator overseeing the compression molding process determines the necessary cycle time for the material to cure, thereby reaching the optimal level. With the cycle finished, the molded parts or components get ejected from the mold cavity.


Compared to other processing methods, there are several advantages of compression molding. For example, tooling is typically less complex, making it easier and less expensive to manufacture parts and components. Also, the amount of wasted rubber material is less than with transfer molding or traditional injection molding. Finally, this process is ideal for more cure systems and elastomers. On the downside, preforming rubber requires time and effort that can impact the cost and, in many instances, extend cycle times.


Common Rubber Compression Molding Defects

Top manufacturing companies use state-of-the-art machinery, high-quality rubber, and skilled operators to prevent defects in the finished product. Although this dramatically reduces any risk, sometimes things cannot be avoided. A few examples of defects include:

  • Blistering – Usually, blistering is due to uncured rubber compound.
  • Short Moldings – The reasons for this defect include insufficient material charge, improperly distributed material, low pressure, the low closing speed of the press, and material that is too stiff.
  • Porosity – If the material charge is insufficient, the flash line too tight, the material flow too easy, or mold temperature too high, this type of defect becomes a risk.

For the perfect compression molding product, you can always count on the professionals at RPM Industries. We invite you to visit our website to learn more about our services or call us today.