The influence of injection molding process conditions on products
1. Plastic materials
The different properties of plastic materials determine the complexity of the injection molding process. Different performance parameters may lead to completely different molding results.
2. Injection temperature
The melt flows into the cooled cavity and loses heat due to heat conduction. At the same time, heat is generated due to shearing, which may be more or less than the heat lost by heat conduction, mainly depending on the injection conditions. The viscosity of the melt decreases with increasing temperature. In this way, the higher the injection temperature, the lower the viscosity of the melt, and the smaller the required filling pressure. At the same time, the injection temperature is also limited by the thermal degradation temperature and decomposition temperature.
3. Mold temperature
The lower the mold temperature, the faster the heat loss due to heat conduction, the lower the temperature of the melt, and the worse the fluidity. This phenomenon is particularly obvious when a lower injection rate is used.
IV. Injection time
The influence of injection time on the injection molding process is manifested in two aspects:
(1) Shortening the injection time increases the shear strain rate in the melt. Due to the shear thinning characteristics of the plastic melt, the viscosity of the melt decreases, and the injection pressure required to fill the cavity also decreases.
(2) Shortening the injection time increases the shear strain rate in the melt, the greater the shear heat generation, and the less heat dissipated by heat conduction. Therefore, the higher the melt temperature, the lower the viscosity, and the lower the injection pressure required to fill the cavity.
The result of the combined effect of the above three conditions makes the curve of the injection pressure required to fill the cavity present a "U" shape. In other words, there is an injection time when the required injection pressure is the minimum.
