Plastic Injection Mould

Plastic Injection Mould

The plastic injection mould process is used to fabricate parts with a range of complexities, from simple shapes to precision parts of geometric complexity. While the majority of plastic injection mold processes use thermoplastics such as ABS, polysulfones, polycarbonate, polyamides and fluoropolymers, a small amount of plastic materials such as thermosets, elastomers and biodegradable plastics are used as well. Typical applications of the plastic injection mold process include catheters, plugs, caps, electronic enclosures, automotive parts, medical components, video game cartridges, consumer appliances and screwdriver handles. As a result, plastic injection mould processes are often utilized in industries such as electronics, aerospace, manufacturing, construction, medical, automotive, consumer and telecommunications. Some advantages of plastic mold processes include high production rates, little need to finish parts after the molding is complete and cost-efficiency, as the cost per part is very low despite the high cost of tooling. Additional advantages of the plastic injection mould process include the efficient use of materials and energy, precision-formed parts and a negligible amount of waste produced.

In order to begin the plastic mould process, the barrel section of a plastic molding machine must be heated. For the next step, plastic pellets or granules are fed into a hopper where a screw pushes them to the heated barrel. In the barrel, the pellets or granules are heated to the melting point. The molten plastic material is then injected into the cavity of a split die chamber/mold, which is then clamped shut. The plastic resin cools as water or other fluids circulate through the cooling system of the mold, extracting the heat. The molded plastic part is held in the mold under high pressure until the part solidifies. The plastic part is finally ejected from the plastic mold, and the process begins again. Although much of the process remains the same, there are a number of different kinds of plastic mold processes including gas assist injection molding, rapid injection molding and reaction injection molding. Gas assist injection molding is a low-pressure process in which inert gas, such as nitrogen, is forced into the melt while it is entering the mold, packing the plastic into the cavities. Rapid injection molding is primarily used in prototyping and the low-volume production of plastic parts since the production time is drastically shorter than conventional molding process. Reaction injection molding is often used to produce larger parts because of low viscosity and low injection pressures.