Engineering technology of Plastic Injection Molding

In the injection molding process, the complete technology is an indispensable engineering technology. It involves transforming plastics into products that retain their original properties. The important process conditions of injection molding are the temperature, pressure and corresponding action time that affect the plasticizing flow and cooling. This can be roughly divided into three aspects: one, temperature control, two pressure control, and three molding cycles. There are a total of 3 temperature control points to explain the barrel, nozzle, and mold temperature as follows:

1). The temperature of the barrel. According to the different conditions, the selected barrel temperature is also different. The temperature that needs to be controlled in the injection molding process is the barrel temperature which mainly affects the plasticization and flow of the plastic. Each plastic has a different flow temperature. For the same plastic, due to different sources or grades, its flow temperature and decomposition temperature are different. This is due to the difference in average molecular weight and molecular weight distribution. Plastics in different types of injection The plasticization process in the machine is also different, so the temperature of the barrel is also different.

2). Nozzle temperature: Normally, the nozzle temperature is slightly lower than the maximum temperature of the barrel. This is to prevent the occurrence of drooling when the melt is in the straight-through nozzle. The temperature of the nozzle should not be too low, otherwise it will cause the premature solidification of the melt and block the nozzle, or the performance of the product will be affected due to the premature solidification of the material injected into the cavity. The proper temperature can guarantee the performance and other characteristics of the product.

3). Mold temperature: Generally speaking, the mold temperature has a great influence on the internal performance and apparent quality of the product, which can be said to be one of the most important factors. The mold temperature depends on the crystallinity of the plastic, the size and structure of the product, performance requirements, and other process conditions such as melt temperature, injection speed and injection pressure, and molding cycle are all important reasons for molding.

2. Pressure control. As we all know, it can be said that the control of pressure is one of the important courses. The pressure in the process of injection molding includes plasticizing pressure and injection pressure, and directly affects the plasticization of plastics and product quality. The plasticizing pressure and injection pressure have the following points.

Plasticizing pressure: When using a screw injection machine, the pressure on the top of the screw when the screw rotates and retreats is called the plasticizing pressure, also known as the back pressure. This pressure has played a very important role in shaping. The size of this pressure can be adjusted by the overflow valve in the hydraulic system. In the injection, the size of the plasticizing pressure is constant with the screw speed. When the plasticizing pressure is increased, the temperature of the melt will be increased, but the speed of the plasticizing will be reduced.

Injection pressure: In the current production, it is foreseeable that the injection pressure of almost all injection machines is based on the pressure exerted by the plunger or the top of the screw on the plastic. The role of injection pressure in the molding of injection molded parts is to overcome the flow resistance of the plastic from the barrel to the cavity, the rate of filling the mold with the melt, and the compaction of the melt. This is the injection pressure.

Third, the molding cycle. We know that the time required to complete an injection molding process is called the molding cycle, also known as the molding cycle. The molding cycle directly affects production efficiency and equipment utilization. No matter how it works, in the production process, we should try to shorten the relevant time in the molding cycle under the premise of ensuring quality. This can improve production efficiency. This is also a nature of the molding cycle. In the injection molding process, each interval is short, and the overall quality and efficiency will naturally increase.