Compression Moulding is one of three processes used to mould rubber parts, the oldest and simplest, and in many specific applications, is still the best.

The first step in Compression Moulding is loading a carefully measured amount of the chosen compound, into the bottom portion of the preheated mould tool. The two halves of the mould are brought together, forcing the material to conform to the shape of the mould. The material is compressed and heated until cured to the desired shape. The two halves of the mould tool are then opened and the part created is removed.

Tooling for Compression Moulding are often simpler than tooling for injection moulding, less expensive, lower maintenance and less wasteful (for low volume).  The process may be suitable for, low, medium and high throughput, depending on the application.
compression moulding

Step 1 A piece (approximately 110% of the finished part weight) of cold, uncured rubber compound is placed in the heated mould.


compression moulding

Step 2 The mould is closed up and held under hydraulic pressure and heat while the rubber cures.

compression moulding		 Step 3 When the mould opens the part can be removed; the excess rubber (flash) needs to be trimmed off the part.

 

Advantages of Compression Moulding

  • Lowest cost tools

Disadvantages of Compression Moulding

  • Offers least process consistency
  • Difficult to control flash
  • Not suited for some types of parts
  • The tool is held partially open due to the excess of rubber
  • A “flash” line will always be present where the tool closes