Types of plastic injection molding technology: Injection, Bi-injection, Co-Injection and Over Molding

Plastic injection molding is a manufacturing process for the production of parts by injecting material into a mold.

The resin in the form of plastic granules is fed through a hopper to a cylinder (barrel) by heating with an internal screw (Spindle) that melts and plasticizes the plastic by means of heat and friction and then injects it under pressure into the cavities of a mold, where it cools and solidifies to the configuration of the mold cavities

From the elaboration of tables, chairs to electrical connectors, Injection Molding is undoubtedly one of the most important plastic parts manufacturing processes in the industry. It consists of melting the resin to feed it into a mold with the shape of the piece, allowing the material to cool and expelling the molded piece.

That is, the resin in the form of granules is fed through a hopper to a cylinder (barrel) heated with an internal screw (spindle) that melts and plasticizes the plastic by means of heat and friction and then injects it under pressure into the cavities. of a mold, where it cools and solidifies to the configuration of the cavities of the mold.

To achieve different textures and finishes there are some variables within injection molding that consist of:

1. Over-molding: Injection molding where a material is injected onto a part or insert of the same or another material.

2-step molding is a type of over-molding where the insert is made of the same material. The second injection can cover the entire insert or just go on a couple of selected surfaces.

Overmolding can take place on the same machine with a rotating carousel or on a second machine.

2. Bi-Injection: it is the simplest variant of injection molding, of two components, from the point of view of the machine and the mold, in which the cavity is simultaneously filled with the two different components that come from two points different injection. The problem with this technique is that when injecting two different components, the welding line, which is produced by the meeting of said components, is a little out of control.
3. Co-Injection: it is a process in which two or more different polymers are laminated together by injection molding. These polymers can be identical, except for color or hardness, or they can be of different types of polymers. When different polymers are used, they must be compatible (soldered) and melt at approximately the same temperature.

These variables of the molding process allow to have a great variety of finishes, decorative and functional techniques.

All of these procedures come with an intention. As we well note, the finishes on the plastic pieces may vary depending on the procedure. If we seek to make quality pieces, the ideal is to specialize in these different processes, in this way, a better variety of pieces and better quality can be obtained (not only in finishes, but also in decorative and functional themes)

For more about the types of plastic injection molding technology: injection, bi-injection, co-injection and over molding,you can pay a visit to Djmolding at https://www.djmolding.com/technology-application/ for more info.