Developing a method for evaluating color changeover in a hot-runner multi-cavity injection mold

Quality control, which nowadays almost always involves the integration of online measurement methods into the production process, is of paramount importance for injection molding. Online pressure and temperature measurement is already widespread and essential for quality and production control. On the other hand, monitoring the appearance, color, or surface defects of products is less common. It is usually carried out with a camera system installed on a conveyor belt independently of the injection molding process. However, color defects in injection molded products, which are caused by the poor distribution of the colorant, are common defects that usually occur after color changeover in injection molding. Color changeover is currently not a well-controlled procedure, and it is associated with high additional costs. It also requires a large amount of material and causes extended downtime of the injection molding equipment. Color changeover can be even more complicated due to the specific design of the injection unit, the presence of static or dynamic mixers, and the hot runner system design of the molds. In this study, we develop a measurement method to monitor color change and the amount of material and time needed to clean the injection system. This method is based on digital image processing. It can be very useful in the plastic industry and can greatly help manufacturers to develop and produce more efficient injection molding systems.