A study on quality monitoring of injection-molded parts

Quality of injection-molded part is dependent on both mold design and processing conditions. From the design point of view, an optimal shrinkage should be used to compensate for the shrinkage of molded parts. From the processing point of view, it is important to analyze the priority of processing conditions because a number of processing conditions affect the quality of molded parts. Difference between designed and measured shrinkage at the specific position of a specimen box is minimized as a characteristic value to decide the quality of molded parts. Optimal processing conditions are 53.56 mm/s of injection velocity and 41.89 bar of holding pressure. The ranges of indirect control parameters, such as maximum cavity pressure or weight of molded part measured at the optimal processing condition, are used for monitoring the quality of molded parts in process. The judged results are displayed at the monitor by alarming a sound or lighting a lamp in case of bad-conditioned part.