Advantages, inspection and improvement of Automotive Parts plastic parts

With the development of automobile manufacturing technology, many auto parts are injection molded parts, which has resistance to stretch, impact and bending, with better functional performance.
In order to ensure the quality of auto injection parts, series of tests are required after the production. Usually, the parts need to be immersed in water for 4 hours, keeping water temperature at 60 degrees, and then special tools are used for testing. If there is no big change in size, the quality of the product is good, otherwise the injection parts are not up to standard.
How can this situation be improved? On the one hand, reducing the mold temperature and extend the cooling time; improving the injection pressure, or the production on the other hand.