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What is Rubber Injection Molding?

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  • Written By: Carol Francois
  • Edited By: Heather Bailey
  • Last Modified Date: 13 September 2016
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    2003-2016
    Conjecture Corporation
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Rubber injection molding is a manufacturing process used to create rubber parts. This type of process is ideal for creating small parts that require precision, or parts that fit inside other components. Rubber parts are widely used in a range of mechanical parts and machines. A rubber injection molding machine is typically found in a press shop or in the manufacturing sector.

The basic process used in rubber injection molding is quite simple. A mold is created out of metal with the exact specifications and dimensions of the rubber part. This mold is inserted into a press and connected to a rubber injection system.

A press applies pressure to hold the top and bottom parts of the mold together. Rubber is injected into the mold using a large ram or screw. The heated, uncured rubber is forced into the mold cavity using an injection nozzle. Extra rubber or overflow may occur, due to the force required and the need to fill the mold completely. As the rubber cools, it separates from the walls of the mold, while retaining the details and shape of the design. The press opens and the rubber part is released.

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It is important to note that there are no heater elements in a rubber injection molding system. The rubber is heated and temperature controlled by the rubber injection press. The actual molds themselves are typically made of stainless steel and are not designed to retain heat. In fact, many designs require the mold to be quickly cooled, forcing the rubber to cure within a smaller time frame.

There are two different types of molds: horizontal and vertical. These units have a great deal in common, but there are a few main items that differ between the two models. In a horizontal machine, robotics are often required to move the mold to another part of the machine and eject the finished product. In a vertical machine, the finished parts simply drop into a waiting container. There is less rubber lost with each part in a vertical system, since the pressure in the injection system must contend with the force of gravity.

Many units are designed to include press brushes, ejectors, and multiple molds. These enhancements greatly increase the productivity of the system and reduce the reliance on human intervention in the manufacturing process. Reducing the amount of rubber lost in the process is critical to maintaining low costs and minimizing waste. Rubber is a natural resource that is quite expensive to obtain and should not be wasted.

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anon344309
Post 3

Rubber being a live material, it has to be kept in air conditioned rooms before it is used for injection molding. No other cooling process is done.

anon306163
Post 1

Is the cooling of uncured rubber done before injection molding? If so, does it reduce rubber waste?

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