Analysis of Injection Molding Elements

Several key elements of injection molding

Injection molding is also a separate engineering technology aimed at transforming thermoplastic raw materials into products that can be used and maintain their original performance through important process conditions of injection molding. 

Therefore, the formulation of process parameters for injection molding is an important link to ensure injection molding processing. The key elements to pay special attention to in the formulation of injection molding process parameters are temperature, pressure, and time.

Injection temperature control: The temperature that needs to be controlled during the injection molding process includes the barrel temperature, nozzle temperature, and mold temperature. The main purpose of controlling the temperature of the barrel and nozzle is to enable the material in the barrel to undergo sufficient plasticization and flow.

The purpose of controlling the temperature of the mold is to improve the fluidity of the melted material during the filling process, and to help the melted material quickly fill various parts of the mold cavity. Secondly, it enables the material filled with the mold cavity to undergo sufficient cooling and shaping at a constant temperature. Thirdly, the control of mold temperature has a great impact on the internal performance and apparent quality of products.

Pressure control: During the processing of injection molded products, it is necessary to control the pressure, including injection pressure and plasticizing pressure (i.e. back pressure).

Injection pressure: The pressure is transmitted to the tail end of the barrel through the hydraulic system of the injection machine (electric injection machine uses servo motor), which drives the screw to move forward. The pressure applied to the tail end of the screw is called injection pressure. In injection molding, the role of injection pressure is to overcome the flow resistance of molten plastic from the barrel to the mold cavity during the filling process, provide a rate of molten filling, and compact the molten material.

Plasticization pressure: refers to the pressure that the molten material at the top of the screw experiences when the screw rotates backwards, which is called plasticization pressure, also known as back pressure. It can also be said that overcoming the resistance generated by the rotation of the screw feed is called back pressure. In general, increasing the back pressure appropriately can make the temperature of the melt uniform, mix the pigments evenly, and discharge the gas in the melt. In normal production operations, the size of the back pressure should be as small as possible while maintaining good product quality.

Time control: The time that needs to be controlled during the injection molding process includes injection time, holding time, plasticization time, cooling time, and cycle time.