The complexity of the properties of plastic materials determines the complexity of the injection molding process. The performance of plastic materials varies greatly due to different varieties, different processing conditions for producing injection molded parts, different grades, and even different batches. This is a rule. Therefore, different performance parameters may lead to completely different molding results. The setting of performance parameters must be paid attention to. The injection time needs attention. The impact of the injection time on the injection molding process is manifested in three aspects: shorten the injection time, and the shear strain rate in the melt will also increase.
(1) 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.
(2) The injection pressure required to fill the cavity should also be increased.
(3) The greater the shear heating, and the less heat lost due to thermal conduction, the higher the temperature of the melt and the lower the viscosity, which is needed to fill the cavity. The injection pressure should also be reduced. As a result of the above three conditions, the curve of the injection pressure required to fill the cavity presents a “U” shape. There is an injection time, at which time the required injection pressure is the smallest.
The injection temperature also needs attention. The melt flows into the cooled cavity and loses heat due to heat conduction. At the same time, heat is generated due to shearing. This part of the heat may be more or less than the heat lost by heat conduction. This is caused by many factors, mainly depending on the conditions of the injection molded parts. In addition, the viscosity of the melt becomes lower as the temperature increases. Performance changes like this. In this way, the higher the injection temperature, the lower the viscosity of the melt and the smaller the required filling pressure. This change is different. At the same time, the injection temperature is also limited by the thermal degradation temperature and decomposition temperature.
In this injection molding process, the effects of different conditions on the products are diversified. The material properties of plastics are different, and the parameters are different. The injection molding conditions of injection molded products, the higher the temperature, the lower the viscosity and the lower the pressure. This is the performance of the injection temperature under multiple factors. The factors affecting temperature are diversified. The lower the melt temperature, the worse the fluidity. The last is the injection time. It has several major performances that need attention. If the shear strain rate in the solution increases, the required injection pressure must also increase. If the viscosity is reduced, the injection pressure should be reduced; if the melt temperature is high, If the viscosity is low, the injection pressure should also be reduced. This pressure curve is U-shaped. This is the impact of injection molding on the product.
Post time: Sep-18-2021