Injection moulding

Injection molding (also called injection molding / transfer molding) was developed to limit the disadvantages of compression molding (moulding). Rubber is loaded into a chamber that injects rubber via channels into the various mold rooms.

By forcing the rubber to flow through channels and ingots, the rubber is preheated. This preheating contributes to shortened vulcanization times. Provided that the injection pressure does not exceed the closing pressure of the mold, beard formation can be reduced as it enables the injection unit to control the amount of injected rubber.

The advantages of injection molding are mainly the following:
1. Fabrication of substances and their handling is greatly simplified
2. The preheating of the rubber shortens the vulcanization time
3. Because the rubber is preheated, it flows more easily and fills the mold space better
4. The tool is closed when rubber is injected giving less beard formation and better dimensional tolerances for the product
5. In the case of rubber-metal bonding, the rubber comes into better contact with the metal in the form of a "fresh" and clean surface
6. The process can be automated

The disadvantages of injection molding are mainly the following:
1. Tools and machinery are usually more expensive
2. Details with textile inserts are more difficult to manufacture
3. The method places higher demands on the rubber compounds in the form that, among other things, it needs to be easy-flowing