injectionmolding

Injection molding is a manufacturing process used to produce parts by injecting molten material into a hollow mold. It is widely used for thermoplastics and thermosets and is suitable for high-volume production with tight tolerances. The basic equipment comprises a clamping unit and an injection unit mounted on a common frame.

During each cycle, the mold is clamped shut. Molten polymer is injected under high pressure into the mold cavity through sprues and runners, then flows to gates. The material cools and solidifies, the mold opens, and ejector pins push the part out.

Key process variables include melt temperature, injection speed, mold temperature, packing pressure, and cooling time. Proper control reduces defects such as sink marks, flash, and warpage. Parts are designed with uniform wall thickness, draft angles, ribs, bosses, and appropriate gate locations.

Materials used include thermoplastics such as polystyrene, ABS, polycarbonate, polypropylene, and polyethylene, often with additives. Thermosets and some metal or ceramic composites require specialized variants. Molds, usually steel or aluminum, include cooling channels, vents, and ejection systems.

Advantages include high production rates, repeatable tolerances, and the ability to produce complex shapes. Limitations include high tooling costs, long lead times for molds, material and design constraints, and waste from sprues and runners. The process is common in automotive, packaging, electronics, and medical devices.