When conducting plastic injection molding, there are many factors that can affect product quality, but in summary, there are four key points.
1. Plastic materials
The complexity of plastic material properties determines the complexity of injection molding processes. The performance of plastic materials varies greatly depending on the variety, brand, manufacturer, and even batch. Different performance parameters may lead to completely different forming results.
2. Injection temperature
The melt flows into the cooled cavity and loses heat due to heat transfer. At the same time, depending on the injection molding conditions, heat is more or less lost due to thermal conductivity, and heat is generated due to shear action. The viscosity of the melt decreases with increasing temperature. Therefore, the higher the injection temperature, the lower the viscosity of the resin, and the lower the required filling pressure. At the same time, the injection temperature is also limited by the thermal degradation temperature and decomposition temperature.
3. Injection temperature
The lower the temperature of plastic injection molding, the faster the heat loss caused by thermal conductivity, the lower the resin temperature, and the poorer the fluidity. This phenomenon is particularly evident at low injection rates.
4. Injection time
The impact of injection molding time on plastic injection molding process is reflected in three aspects:
(1) In order to shorten the injection time, the shear strain rate inside the resin also increases, and the injection pressure required to fill the cavity also increases.
(2) Shortening the injection time and increasing the shear strain rate of the molten resin reduces the viscosity of the molten resin and the injection pressure required to fill the cavity.
(3) Shorten injection time and increase shear strain rate of molten resin. The higher the shear heating, the lower the heat loss caused by heat conduction, the higher the melting temperature, and the lower the viscosity. Therefore, the injection pressure required to fill the cavity should also be reduced. As a result of the above three situations, the injection pressure curve required for filling the cavity is in a "U" shape. In other words, there is an injection time that requires minimum injection pressure.
