Injection molding

Injection molding is a manufacturing process for producing parts by injecting molten material into a mold, or mold. Injection molding can be performed with a host of materials, including metals, glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and forced into a mold cavity, where it cools and hardens to the configuration of the cavity.

History

The first injection molding machine was patented in 1872, and celluloid was used to produce simple everyday items such as hair combs. The industry progressed slowly over the years, producing products such as collar stays, buttons, and hat bands. In the 1940s, the need for mass production of plastic products increased and saw the introduction of the first screw injection machine.

Process

Injection molding consists of high pressure injection of the raw material into a mold which shapes the polymer into the desired shape. Initially, material is fed into a heated barrel and then forced into a mold cavity. After that, it cools down and hardens into the shape of the mold cavity.

Injection

The raw plastic material is pushed into a hot barrel where it gets melted down into a liquid state. The material is then forced into a mold cavity, which it fills and solidifies, forming the final product.

Cooling

The molten plastic that is inside the mold begins to cool as soon as it makes contact with the interior mold surfaces. As the plastic cools, it will solidify into the shape of the desired part.

Ejection

After the cooling process, the hardened plastic part is ejected from the mold by the ejection system of the injection molding machine.

Applications

Injection molding is used in the manufacturing of a wide range of products, from small components to entire body panels of cars. It is widely used for manufacturing a variety of parts, from the smallest plastic production to entire body panels of cars.

Advantages and Disadvantages

Injection molding has many advantages such as high production rates, repeatable high tolerances, the ability to use a wide range of materials, low labor cost, minimal scrap losses, and little need to finish parts after molding. However, the machinery is expensive and requires high setup cost.

See Also

• Plastic molding
• Blow molding
• Compression molding
• Rotational molding