RPM Industries LLC
rubber compression molding

Defects that can Occur in a Product after Rubber Compression Molding

When it comes to rubber compression molding, it is essential that you hire a manufacturing company with experience and expertise. That way, you have assurance that the molding process gets done by an expert so that you ultimately end up with a precision product as opposed to one with defects.


Rubber Molding Process

The process of rubber molding entails the appropriate rubber material getting placed inside of a mold and is compressed between two plates. That pressure is what forces the material compound to flow into and fill the cavity. Until reaching the right pressure at the correct temperature, the rubber material remains compressed. Once cured, the molded part or component gets ejected from the mold cavity in the shape and size that you need.


Rubber Compression Molding Defects

As long as a professional operator uses a high-quality material, oversees the rubber molding process, and relies on a state-of-the-art machine, you can expect perfection in the finished product. These things combined significantly reduce any risk of imperfection. However, even under the best of circumstances, defects occur. The following are the most common types of flaws associated with this molding process.


  • Blistering – Typically, a blistering defect is the result of an uncured rubber compound.
  • Chips – Chips consists of damage to the surface of the part or component, usually around the edge. The causes include rough handling or bypass, a defect in the mold, or an issue with tooling.
  • Contamination – A contaminated finished product is the result of foreign material in the raw rubber.
  • Flow Lines – Flow lines appear when creating a prototype. The primary cause is the varying speeds of the molten plastic changing direction through the mold’s bends and contours. However, flow lines also develop due to a slow injection speed, if the material flows through cross-sections of different wall thicknesses, or if the rubber begins to solidify.
  • Porosity – With an insufficient material charge, several problems occur, including the material flowing too easily, the flash line getting too tight, and the temperature of the mold becoming too hot.
  • Short Moldings – Defect causes include an insufficient material charge, a pressure that is too low, an inadequate distribution of the material, overly stiff rubber, or low press closing speed.


For precision molded products, you can always count on us at RPM Industries, Inc. For information about our company and the various services that we offer, visit us online or call today.