What is injection molding

Injection molding is a manufacturing process for producing parts by injecting molten material into a mold. Injection molding can be performed with a host of materials mainly including metals (for which the process is called die-casting), glasses, elastomers, and most commonly thermoplastic and thermosetting polymers. The method is suitable for the mass production of products with complicated shapes, and takes a large part in the area of plastic processing.

The first stage of injection molding is to create the mold itself. Most molds are made from metal, usually aluminum or steel, and precision machined to match the features of the product they are to produce. Once the mold has been created by the mold-maker, the material for the part is fed into a heated barrel and mixed using a helical shaped screw. Heating bands melt the material in the barrel and the molten metal or molten plastic material is then fed into the mold cavity where it cools and hardens, matching the shape of the mold. The cooling time can be reduced through the use of cooling lines that circulate water or oil from an external temperature controller.

Injection molding uses a special-purpose machine that has three parts: the injection unit, the mold and the clamp. Parts to be injection-molded must be very carefully designed to facilitate the molding process; the material used for the part, the desired shape and features of the part, the material of the mold, and the properties of the molding machine must all be taken into account. The versatility of injection molding is facilitated by this breadth of design considerations and possibilities.

The functions of the injection unit are to melt plastic by heat and then to inject molten plastic into a mold. The screw is rotated to melt plastic introduced from the hopper and to accumulate molten plastic in front of the screw . After the required amount of molten plastic is accumulated, injection process is stared. While molten plastic is flowing in a mold, the machine controls the moving speed of the screw, or injection speed. On the other hand, it controls dwell pressure after molten plastic fills out cavities.