When producing injection molds, there are often many factors that affect the quality of the product.
To sum up, there are mainly four points:
1. Mold temperature
The lower the mold temperature, the faster the heat is lost due to thermal conduction, the lower the temperature of the melt, and the worse the fluidity. This phenomenon is particularly evident when lower injection rates are used.
2. Plastic materials
The complexity of plastic material properties determines the complexity of the injection molding process. The performance of plastic materials varies greatly due to different varieties, different brands, different manufacturers, and even different batches. Different performance parameters may lead to completely different molding results.
3. Injection temperature
The melt flows into the cooled mold cavity and loses heat due to thermal conduction. At the same time, heat is generated due to shearing. This heat may be more or less than the heat lost by thermal conduction, mainly depending on the injection molding conditions. The viscosity of the melt becomes lower as the temperature increases. 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 thermal degradation temperature and decomposition temperature.
4. Injection time
The impact of injection time on the injection molding process is reflected in three aspects:
(1) If the injection time is shortened, the shear strain rate in the melt will also increase, and the injection pressure required to fill the cavity will also increase.
(2) Shorten the injection time and increase 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 must also decrease.
(3) Shorten the injection time, the shear strain rate in the melt increases, the greater the shear heat, and at the same time less heat is lost due to heat conduction. Therefore, the temperature of the melt is higher and the viscosity is lower. The injection required to fill the cavity is Stress should also be reduced. The combined effect of the above three conditions makes the curve of the injection pressure required to fill the cavity appear “U” shaped. That is, there is an injection time when the required injection pressure is minimal.
Post time: Dec-11-2023
