Plastic Injection

Mold Building

Prototyping

Injection Parts

 

 

Plastic Injection

The plastic injection molding process has been around since 1872 and is a process of injecting molten material (typically metal or plastic) into a void or cavity that has been created in a particular shape. In plastics, the raw material comes in pellet form, can be pre-colored or in either a natural state to be colored by the processor, or molder. The natural material is usually colored with a pelleted concentrate that looks much like the base material (resin) but has been formulated with high concentrations of pigment. The color concentrate is typically added to the base resin at a ratio of 25/1, or 4%. The resin is then gravity fed through a hopper into a heated barrel that contains a reciprocating screw that rotates, homogenizing the color and base resin together changing the color. Once the machine cycle is started, the plastic injection molding process begins. The mold closes and the material is injected out of the barrel under very high pressure, typically 15-30,000 psi, via a hydraulic pump through a hole in the mold (sprue hole), down a channel (runner), through the gate, and into the cavity. The mold that houses the cavity has cooling channels drilled into it to transfer the heat away much like an engine block, and the material then cools and re-solidifies. Lastly, the mold (or die) opens and the part is ejected. When the part is ejected out of the mold, the steel required to create any undercut design features of the part that prevent it from being removed straight out of the mold need to be dislodged before it can be ejected. This could be threads, holes, or simply a step in the part that traps steel and prevents a straight ejection. Molds are made by POWSTAR from metal, usually either steel or aluminum, and precision-machined to form the features of the desired part. Injection molding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars and parts of home appliances.