Rubber - Injection Molding - Stern Industries

RUBBER
INJECTION MOLDING

Injection molding is the most advanced method of molding rubber parts. Stern Industries supplies customers with the most consistant results by injection molding. The molding process consists of working and warming the uncured rubber and then injecting the material into the mold at controlled speeds, pressures and temperatures.

PLASTICS

Helping solve your dilemma is our core competency. The marriage of your part requirements to the right process is critical. Utilizing our access to a vast array of plastics choices will help your company succeed. Click for an extensive discussion of plastics processes.

RUBBER

COMPRESSION MOLDING
TRANSFER MOLDING
INJECTION MOLDING
EXTRUSION
BONDING
DIE CUTTING

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 thermal 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 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 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 molded rubber parts and components are used in a variety of markets and applications. Some of these parts have a metallic insert that is completely encapsulated in the rubber, adding dimensional stability or rigidity. Others may have the rubber bonded to an insert providing a friction, sealing, or flexible surface.

Injection tools and equipment are generally more expensive than those for either compression or transfer and have correspondingly higher overheads. The process is therefore suitable for higher volume production quantities.

Because modern rubber injection molding machines are digitally controlled; processing parameters can be controlled and in combination with good product design and a properly compounded elastomer, injection molding can contribute to a higher quality product.

Many different rubber compounds can be injection molded while requiring process consideration for the longer flow paths and higher mold temperatures. The end usage determines the design requirements and when an existing formula is not available that meets the design criteria, the chemist develops a compound to do so.