In the production of some important injection molded parts that require more precise dimensions, the allowable range of fluctuations in the dimensions of each part is very small, even requiring only one or two fluctuations.

In the production process, the main factor that usually affects the dimensional accuracy of injection molded parts is the shrinkage rate of injection molded parts. The greater the shrinkage, the worse the accuracy. Therefore, due to the large shrinkage of PP and POM injection molded parts, the accuracy of their injection molded parts is usually poor for this reason. The shrinkage of other materials is usually not very small, so the dimensional accuracy of injection molded parts is not very high under normal injection molding conditions.

In fact, the shrinkage rate of injection molded parts can be reduced by adjusting the machine, so as to achieve the purpose of improving the dimensional accuracy of injection molded parts. We only need to greatly increase the time and pressure of injection or holding pressure to reduce the shrinkage of injection molded parts, the shrinkage rate is significantly reduced, and the dimensional accuracy can naturally be improved.

Due to the limitation of the quality of the injection molding machine, the injection pressure should generally not be adjusted too high, otherwise a large amount of injection will be generated. Therefore, in the commonly used ordinary injection molding machines, the main purpose of improving the dimensional accuracy of injection molded parts is to increase the time of injection or holding pressure.

In order to ensure the dimensional accuracy of injection molded parts, the accuracy of the mold is the first condition that needs to be guaranteed, and it is more important to choose a stable, reliable (with little parameter fluctuation) and adequate pressure injection molding machine for production.

Some of the newly developed high-precision injection molding machines in modern times are actually high-pressure injection molding machines with stable performance and extremely high parameter accuracy. According to reports, the shrinkage rate of its injection molded parts can be almost zero, that is to say, the size of each injection molded part is almost as long as the size of the cavity, the fluctuation range is only about a trace, and the accuracy is extremely high.