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In injecting molding processes, injection tooling consists of the metal mold and fixtures into which a material, such plastic, rubber or metal, is injected to produce parts. This tooling allows parts to be mass-produced at a relatively inexpensive per part cost. These parts are used in many industries, such as automotive, healthcare, and consumer goods. A bottle cap is an example of a part created from injection molded plastics.
Injecting tooling is complicated and expensive to make. Custom injection molding and tooling is designed and built by skilled workers. When designing the tooling, elements such as the part’s material thickness, part tolerance, the number of parts expected to be produced, and the injecting molding machine requirements are considered.
The injection tooling molds are commonly made from steel, which is usually a hardened or a pre-hardened steel. When small numbers of a part are expected to be produced, the mold might be made out of aluminum. Aluminum is less expensive than the steel, but it may not last as long. In situations in which the material to be used is sensitive to the heat generated in the injection molding process, beryllium-copper alloy may be used instead.
An injection molding prototype may be developed to ensure the parts produced by the injection tooling will meet specifications. The injection molding process for the part in question may also be fine-tuned during prototyping. Building a prototype is less expensive than building production-quality injection tooling meant to withstand heavy usage.
The basic process of rubber and plastic injection molding consists of using an injection molding machine, setting up the injection tooling, and filling the machine’s hopper with the rubber or plastic material. The machine will move the material from the hopper to the tooling, heat the material, and melt it. A specified amount of material, known as a “shot,” will be injected into the mold. When the molding process is completed, the mold opens and the parts are unloaded.
Rapid injection molding is a process that speeds tooling design and parts production. It is appropriate for generating prototype parts or for small production runs. In the case of large production runs, this process may not be cost effective.
The first injection molding machine, which was plunger-style, was patented in the U.S. in the 1870s. Demand for injection tooling grew rapidly during World War II because parts were needed for the war. With this increased demand came the development of the screw injection machine. This style of machine was able to produce better quality parts than the previous plunger style.
Injection molding companies can be found throughout the world. Some of the countries producing injection molding parts include China, the U.S., Germany, and Japan. The parts may be shipped elsewhere for assembly.
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