Influence of process conditions on products in injection molding

Generally speaking, the complexity of plastic material properties determines the complexity of the injection molding process. This is recognized. The performance of plastic materials varies greatly due to different varieties, different grades, different manufacturers of injection molded parts, and even different batches. There are also rules to follow. Therefore different performance parameters may lead to completely different molding results. Pay attention to the performance parameter setting, which must be kept in mind.

Injection temperature also needs attention. 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. 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 is so variable. 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, and at the same time, the injection temperature is also limited by the thermal degradation temperature and decomposition temperature.

As we all know, there are various factors that affect the temperature. The mold temperature of the injection molded part, the lower the mold temperature of the injection molded part, 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 a lower injection rate. Therefore, it is not easy to adopt the conditional method of low rate.

In addition, the injection time, the impact of injection time on the injection molding process is manifested in three aspects: shortening the injection time, the shear strain rate in the melt will also increase (1) the injection pressure required to fill the cavity should also increase. (2) 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) The greater the shear heating, the less heat is lost due to heat conduction, so the higher the temperature of the melt, the lower the viscosity, and the lower the injection pressure required to fill the cavity. 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. There is an injection time at which the minimum injection pressure is required.

In this injection molding process, the influence of different conditions on the product is diverse. The material properties of plastics are different, and the parameters are different. Injection molding conditions of injection molded products, the higher the temperature, the lower the viscosity and the lower the pressure. This is the injection temperature, the performance of many factors. The factors affecting the temperature are diverse, the lower the temperature of the melt, 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 will also increase. If the viscosity decreases, the injection pressure should be reduced; if the melt temperature is high and the viscosity is low, the injection pressure should also be reduced. This pressure curve is U-shaped. This is the influence of process conditions on products in injection molding.