Precision injection molding is determined on the basis of the accuracy of the injection products, namely, product size tolerance, shape and position tolerance and surface roughness. Precision injection molding must have many related conditions, and the most essential is the plastic material, injection mold, injection molding process and injection molding equipment these four basic factors. When designing plastic products, engineering plastics should be selected firstly, and engineering plastics which can be precisely injected must be selected materials with high mechanical properties, stable size, good creep resistance and environmental stress cracking resistance. Secondly, suitable injection moulding machines should be selected according to the selected plastic materials, dimensional accuracy of finished products, weight, quality requirements and expected mold structure. In the process of processing, the main factors affecting the precision injection molding products come from the precision of the mold, injection shrinkage, and the environmental temperature and humidity of the products.

In precision injection molding, the mold is one of the keys to obtain precise plastic products which meet the quality requirements. The mold used in precision injection molding should conform to the requirements of product size, precision and shape. But even if the precision and size of the mold are the same, the actual size of the plastic products molded by the mold will be different because of the shrinkage. Therefore, controlling the shrinkage rate of plastic products effectively is very important in precision injection molding technology.

Whether the mold design is reasonable or not will directly affect the shrinkage rate of the plastic products, because the mold cavity size is calculated by the size of the plastic products plus the estimated shrinkage rate, and the shrinkage rate is recommended by the plastic manufacturer or engineering plastics manuals within a range of values, it is not only with the mold gate form, gate position It is related to the distribution and the crystalline orientation of engineering plastics.

The shape and size of plastic products are related to the distance and location of the gate. Thermal shrinkage, phase change shrinkage, orientation shrinkage, compression shrinkage and elastic recovery are the main factors affecting the shrinkage of plastics. These factors are related to the molding conditions or operating conditions of precision injection molding products. Therefore, the relationship between these factors and injection conditions and their apparent factors, such as injection pressure, cavity pressure and filling speed, injection melt temperature and mold temperature, mold structure, gate form and distribution, gate cross-section area, product wall thickness, and the content of reinforcement filler in plastic materials, must be considered in the design of molds. The influence of quantity, crystallinity and orientation of plastic materials and so on. The above factors are also affected by different plastic materials, other molding conditions such as temperature, humidity, continuous crystallization, internal stress after molding, changes in the injection molding machine.

The shape and size of plastic products are related to the distance and location of the gate. Thermal shrinkage, phase change shrinkage, orientation shrinkage, compression shrinkage and elastic recovery are the main factors affecting the shrinkage of plastics. These factors are related to the molding conditions or operating conditions of precision injection molding products. Therefore, the relationship between these factors and injection conditions and their apparent factors, such as injection pressure, cavity pressure and filling speed, injection melt temperature and mold temperature, mold structure, gate form and distribution, gate cross-section area, product wall thickness, and the content of reinforcement filler in plastic materials, must be considered in the design of molds. The influence of quantity, crystallinity and orientation of plastic materials and so on. The above factors are also affected by different plastic materials, other molding conditions such as temperature, humidity, continuous crystallization, internal stress after molding, changes in the injection molding machine.

Considering the above reasons, the following points should be considered in the design of precision injection mold besides the design elements of general mold: (1) adopting appropriate mold dimension tolerance; (2) avoiding forming shrinkage error; (3) preventing injection deformation; (4) preventing demoulding deformation; (6) minimizing mold manufacturing error; (3) preventing forming shrinkage error; (3) preventing injection deformation; (3) preventing injection deformation; (3) preventing demoulding deformation; (3) preventing mould manufacturing error; Error of mold accuracy; keep mold accuracy.