I believe that almost everyone knows plastic products, because in modern life, we often use plastic products, such as plastic washbasins, plastic buckets, plastic cups, plastic stools, and so on.It is believed that many people also know that most daily plastic products are produced by plastic injection molding process.But how many people know the five most important parameters in the injection molding process? I don't think many people know.Let's have a look at the five important parameters set by the injection molding machine during the injection molding process.

         1. Injection pressure

The injection pressure is provided by the hydraulic system of the injection system. The pressure of the hydraulic cylinder is transferred to the plastic melt through the screw of the injection molding machine. The plastic melt is pushed by the pressure and enters the vertical runner (also the main runner for some molds), the main runner and the diversion channel of the mold through the nozzle of the injection molding machine, and enters the mold cavity through the gate. This process is called the injection molding process, or the filling process. The existence of pressure is to overcome the resistance in the melt flow process, or conversely, the resistance in the flow process needs to be offset by the pressure of the injection molding machine to ensure the smooth filling process.

In the process of injection molding, the pressure at the nozzle of the injection molding machine is the highest to overcome the flow resistance of the melt in the whole process. Then, the pressure gradually decreases along the flow length to the front end of the melt. If the internal exhaust of the mold 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, which can be summarized into three categories: ⑴ material factors, such as plastic type, viscosity, etc.; ⑵ Structural factors, such as the type, number and position of the gating system, the shape of the mold cavity and the thickness of the product; ⑶ Forming process elements.

          2. Injection time

The injection time mentioned here refers to the time required for the plastic melt to fill the cavity, excluding the auxiliary time for mold opening and closing. Although the injection time is very short and has little impact on the molding cycle, the adjustment of injection time plays a great role in the pressure control of the gate, runner and cavity. Reasonable injection time is conducive to the ideal filling of melt, and is of great significance for improving the surface quality of products and reducing dimensional tolerance.

The injection time is much lower than the cooling time, which is about 1/10~1/15 of the cooling time. This rule can be used as the basis for predicting the total molding time of plastic parts. During mold flow analysis, the injection time in the analysis result is equal to the injection time set in the process conditions only when the melt is completely driven by the screw rotation to fill the cavity. If the pressure maintaining switch of the screw occurs before the cavity is filled, the analysis result will be greater than the setting of the process conditions.