What reasons will affect the quality of injection molds?
by：Vowin Rapid Prototyping2023-02-10
In the production of injection molds, the most important issue for customers should be the quality of the mold. The quality of a mold is directly related to the quality of the products produced in the later stage. So what aspects will affect the quality of the mold in the production process? It is specifically manifested in the following four aspects:
1. Raw materials of the product
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 can 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, due to the heat generated by shearing, this part of the heat may be more or less than the heat lost by heat conduction, mainly depending on the injection molding 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 melt temperature, and the worse the fluidity. This phenomenon is especially evident when using lower injection rates.
4. Injection time
The influence of injection time on the injection molding process is manifested 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) The injection time is shortened, the shear strain rate in the melt is increased, and due to the shear thinning characteristics of the plastic melt, the viscosity of the melt is reduced, and the injection pressure required to fill the cavity is also reduced.
(3) Shorten the injection time, the shear strain rate in the melt increases, the greater the shear heat, and the less heat is lost due to heat conduction, so the higher the temperature of the melt, the lower the viscosity, and the injection required to fill the cavity Stress is also lowered. As a result of the combined action of the above three conditions, the curve of the injection pressure required to fill the cavity presents a 'U' shape. That is, there is an injection time at which the minimum injection pressure is required.