In the production of important injection parts that require more precise dimensions, the range of permissible size fluctuations of each part is very small, and even a fluctuation of one or two filaments is required.
In the production process, the main factor that often affects the dimensional accuracy of injection molded parts is the shrinkage rate of the molded parts. The higher the shrinkage rate, the worse the accuracy. Therefore, due to the large shrinkage of the PP and POM injection molded parts, they The accuracy of the injection molded parts is usually poor. This is the reason why the shrinkage rate of other materials is usually not very small. Therefore, the dimensional accuracy of the injection molded parts is not very high under normal general injection molding conditions.
In fact, by adjusting the machine to reduce the shrinkage rate of the injection molded part, the purpose of improving the dimensional accuracy of the injection molded part can be achieved. We only need to greatly increase the time and pressure of injection or holding pressure, so that the shrinkage of the injection molded part can be reduced. The shrinkage rate is significantly reduced, and the dimensional accuracy can naturally be improved.
Due to the limitations of the quality of the injection molding machine, the pressure of the injection can not normally be adjusted too high, otherwise it will produce a large number of batch fronts. Therefore, in the common ordinary injection molding machine, mainly rely on the time to increase injection or hold pressure to achieve Improve the dimensional accuracy of injection molded parts.
In order to ensure the dimensional accuracy of injection molded parts, the precision of the mold is the first requirement to be guaranteed. However, it is more important to choose a stable and reliable (parameter fluctuation is not enough) and an injection molding machine with a sufficient pressure to produce.
Some of the new high-precision injection molding machines developed 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 injection molded parts can be almost 0, that is, the parts that are molded out each time. The size is almost as long as the size of the cavity, the fluctuation range is only about a trace, the precision can be described as extremely high.