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Injection molding tooling is a process for manufacturing parts from plastic materials. A barrel feeds liquid plastic into a mold, where it hardens into the shape of the mold cavity. A toolmaker makes the mold out of metal by using precision machining to create the desired features. Injection molding tooling is a common manufacturing technique for a variety of parts.
John Wesley Hyatt patented the first injection molding tooling machine in 1872. The first products produced with this method included hair combs and buttons. Injection molding tooling advanced rapidly during World War II because of the need for mass-produced plastic products. James Watson Hendry invented the screw injection molding machine in 1946, which provided greater control over the injection speed. It also allowed for the use of colored plastic in injection molding.
Hendry also invented the gas-assisted injection molding tooling machine in the 1970s. It was capable of producing hollow products that cooled quickly, resulting in finished products with greater strength. Injection molding tooling can produce plastic products in a variety of industries, including aerospace, automotive, medical, plumbing and toys.
Injection molding tooling became the most common method for manufacturing plastic parts, and it is considered ideal for mass production. It has a high rate of production and is able to use a variety of materials. Injection molding also has a low labor cost because it can generally produce finished products. The primary disadvantages of this process include the requirement to design the mold and the high start-up cost.
Most polymers are suitable for injection molding tooling, allowing designers to choose from a large number of candidate materials. Common types of polymers include epoxy, polystyrene, polyethylene and nylon. Designers can also blend existing plastics to create a new alloy with the desired properties. Strength, melting point and flexibility are some of the characteristics that product designers must consider when selecting a material for manufacture by injection molding.
The basic components of an injection molding machine include the material hopper, the plunger and the heating unit. These machines are classified according to their clamping force, which is the force with which they can keep the mold closed. The clamping force of an injection molding machine can range from 5,000-6,000 tons (4,536-5,443 metric tons), although the lower end of this range is sufficient for most products. The specific clamping force required depends on factors such as the stiffness of the plastic and the size of the part.