注塑试样制备过程中注射速率的设定方法

Method of Injection Velocity Setting in the Preparation of Injection Moulding Specimens

注射速率表示塑料熔体在模腔内流动的快慢程度,对注塑试样的性能有很大影响。提出在注塑试样制备的注射阶段,熔体在模腔内应为流动状态,并应采用体积转换的方式确定模塑体积。在确定了正确的模塑体积基础上,通过控制螺杆的注射速度调整熔体的注射时间,当该注射时间达到根据标准公式计算的结果时,熔体在模腔内的注射速率则符合标准的要求。该方法的注射速率和注射压力为函数关系,注射压力在试样制备中不再是主要的影响因素,亦不能单独调整注射压力改变注塑试样的某项测试性能。该方法将注射过程与聚合物熔体的“流动”行为相关联,确保了注塑试样制备中的科学性和规范性,进而提高了重复性和再现性水平。

The injection velocity indicated the speed of melt flow in the moulding cavity, which had a great influence on the properties of specimens.In this paper, it was proposed that in the injection stage of injection, the melt should be in the flow state in the mold cavity, and the molding volume should be determined using volume switchover mode.Based on the correct moulding volume, the injection time of the melt was adjusted by controlling the injection speed of the screw.When the injection time could reach the results calculated according to the standard formula, the injection velocity of the melt in the mold cavity meets the requirements of the standard.Thus, the injection velocity of this method is a function of the injection pressure.The injection pressure is no longer the main influencing factor in the specimens preparation, and the injection pressure cannot be adjusted alone to change the test performance of the specimens.This method associates the injection process with the "flow" behavior of polymer melt, ensures the scientificity and standardization in the preparation of injection moulding specimens, and then improves the level of repeatability and reproducibility.