Enhancement of Injection Molding Consistency by Adjusting Velocity/Pressure Switching Time Based on Clamping Force

Abstract

Abstract The velocity/pressure (V/P) switching time, the transition from the filling phase to the holding phase during the injection molding cycle, plays a crucial role in ensuring the quality of the injection molding. Improper settings can lead to a variety of defects, including oversize/undersize, excessive residual stress, flash, warpage, and the like. There are currently many V/P switching methods to choose from. For example, when the injection time or the screw position reaches a prescribed value, that is, when a specified percentage of the cavity is filled with the molten resin, the switching time can be started. These traditional V/P switching methods should work well using precision injection molding machines to ensure accurate and repeatable motion control. However, the quality of shot-to-shot injection molding still varies with environmental changes, such as varying mold/melt temperatures. In this study, we propose a V/P switching adjustment method involving part weight or maximum clamping force increments. It was found that the weight of the injection molded part was highly correlated with the maximum clamping force increment and the V/P switching time. Experimental verification by considering various settings such as V/P switching time, injection speed and holding pressure show that the adjustment method is a feasible means of assuring quality consistency.