WHAT IS RUBBER INJECTION MOLDING?
Stern Rubber Company’s expertise in injection molding goes back as far as the process itself. Injection molding of rubber has its roots in the molding of plastics. In the 1960’s, engineers developed a way to use the same principles in molding plastics to mold rubber, making rubber injection molding one of the most efficient rubber manufacturing processes. The rubber injection molding process works significantly heating the rubber and using a very high pressure to inject the rubber compound in to the mold.
STARTING WITH THE RIGHT RUBBER COMPOUND
Natural or synthetic rubbers (elastomers) are compounded with additives to meet design use specifications and/or ease of processing. The compounded rubber, more technically a thermo set elastomer (TSE) is generally fed in strips into the screw and barrel where it is warmed to temperatures approaching but below that of the rubber mold.
INJECTING THE RUBBER INTO THE MOLD
From there it is injected through channels in the tool into the cavities of the closed hot mold. The combination of pressure, temperature and time facilitates the crosslinking of chemical bonds commonly referred to as vulcanization. Process parameters are usually programmed into the press to control temperature, volume and rate that compound is injected into the mold cavities.
THE FINAL PRODUCT
The process engineer also programs the press to provide adequate time for complete crosslinking. When the press opens, parts are removed and allowed to cool to ambient temperature before deflashing (if necessary), inspection and preparation for shipment. Injection molding of rubber is cost efficient, reduces waste, and it is great for larger volume or more complex geometric parts.
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