Our comprehensive rubber molding capabilities including injection and conventional hydraulic presses.  Both types of presses utilize Programmable Logic Controls to control and monitor the molding process ensuring a consistent process and quality product.

Mid-States has over 20 injection presses and over 70 hydraulic press operating at our Princeton, Indiana Facility.   Our substantial capacity of injection and hydraulic presses allows Mid-States Rubber to offer the appropriate molding technology in meeting the customers needs. 

Depending on the customers application, Mid-States is able to offer Injection, Transfer Injection, Compression or Transfer molding processes.  Working with the customer, Mid-States will select one of the above process to produce a part, balancing capacity and tolerance requirements with cost constraints

Injection Molding Procedure: The injections presses are more automated than the hydraulic presses. The press opens the mold. The operator removes the parts from the cavities, often using compressed air to separate the part from the mold. The mold is closed by the press and the fully automated injection cycle begins. A large screw and ram assembly forces preheated uncured rubber through the injection nozzle, through the mold's runner system, and into the cavities. The uncured rubber is then forced into the shape of the cavity in the mold. The mold remains closed until the rubber is cured. The injection procedure is used for large parts, particularly part with thin walls and large surface areas.
 

Hydraulic Molding Procedure: The mold used in this process consists of a cavity shaped like the part to be produced and a top plate that presses down to form out the part. The heated mold is removed from the press and opened. A precut and weighed piece of custom mixed uncured rubber, is placed into the cavity. If the rubber is to be bonded to metal, the metal piece is placed into the cavity at the same time. The loaded mold is returned to the press and the press is then closed. The pressure exerted by the press pushes the plates together and forces the uncured rubber to flow into the shape of the cavity in the mold. The mold remains closed until the rubber is cured. A compression mold may have many cavities.

A variation on the compression mold is the transfer compression mold, usually used for small parts where a precut and weighed piece of custom mixed uncured rubber, is placed into a "pot" either above or below the part, and rubber is squeezed into the small cavity. This process uses more rubber and creates more scrap, but allows small parts to be made economically since hand loading a small slug of rubber in to dozens or hundreds of cavities would be too expensive.

Mold Design and Fabrication

The molds for customers' products are designed and manufactured by independent tool shops with proven records
of quality craftsmanship. The process of mold design and manufacture is a joint effort between Mid-States and the
tool shop to ensure a mold that is durable, works smoothly and produces a quality product.