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Injection molding process parameters

Injection molding Injection pressure

Injection pressure is provided by the hydraulic system of the injection molding system. The pressure of the hydraulic cylinder is transmitted to the plastic melt through the screw of the injection molding machine. Under the pressure, the plastic melt enters the vertical flow path of the mold through the nozzle of the injection molding machine (also the mainstream channel for some molds), the main flow channel, and the split flow. The process passes through the gate into the mold cavity. This process is the injection molding process, or the filling process. The pressure is present to overcome the resistance during the melt flow, or conversely, the resistance present during the flow process needs to be offset by the pressure of the injection molding machine to ensure a smooth filling process.

During the injection molding process, the pressure at the nozzle of the injection molding machine is highest to overcome the flow resistance throughout the melt. Thereafter, the pressure gradually decreases toward the front end of the melt along the flow length. If the internal exhaust of the cavity is good, the final pressure at the front end of the melt is atmospheric pressure.

There are many factors affecting the melt filling pressure. There are three categories in general:

(1) material factors such as the type and viscosity of the plastic, and (2) structural factors such as the type, number and location of the casting system, and the cavity of the mold. Shape and thickness of the product, etc.;

(3) Process elements of molding.

Injection molding process parameters