Which process parameters can be adjusted to improve the dimensional accuracy of injection molded parts?

Which process parameters can be adjusted to improve the dimensional accuracy of injection molded parts?

When producing critical injection molded parts with precise dimensional requirements, the tolerance for dimensional fluctuation within each part is extremely small, even requiring only a fraction of a millimeter.

During the production process, the primary factor affecting the dimensional accuracy of injection molded parts is shrinkage. The greater the shrinkage, the lower the precision. Therefore, since PP and POM injection molded parts have significant shrinkage, their precision is generally poor. Other materials also typically have shrinkage rates, so the dimensional accuracy of injection molded parts is not very high under typical molding conditions.

In fact, the shrinkage of injection molded parts can be reduced by adjusting the machine, thereby improving their dimensional accuracy. Simply increasing the injection or holding time and pressure can reduce the shrinkage of the molded part. This significantly reduces the shrinkage, and dimensional accuracy naturally improves.

Due to limitations in injection molding machine quality, injection pressure cannot generally be set too high, otherwise excessive flash will occur. Therefore, on commonly used conventional injection molding machines, increasing the injection or holding time is the primary method for improving the dimensional accuracy of molded parts.
To ensure the dimensional accuracy of molded parts, mold accuracy is paramount, and selecting a stable, reliable (with minimal parameter fluctuations) injection molding machine with sufficient pressure is even more crucial.

Some of the newly developed high-precision injection molding machines are actually high-pressure machines with stable performance and extremely high parameter accuracy. They are said to achieve near-zero shrinkage, meaning that the resulting part is virtually identical to the cavity dimensions, with only a slight fluctuation range, resulting in exceptionally high precision.