Color changeover. An invention that optimizes and can automate color changeovers in injection molding machines is the subject of a patent awarded to Inglass SpA, San Polo di Piave, Italy.
When molding large parts, such as automotive panels, multiple injectors are necessary to properly fill the mold. Each injector has a valve pin moved by hydraulic, pneumatic or electrical actuators controlled by an electronic unit. The electronic unit controls the opening and closing of the pins, typically opening the pin of a centralized injector first, and keeping it open the longest, so that it passes the most resin into the mold.
When changing the color of the molded component, a number of cycles are run as the new color works its way through the channels that connect the injectors. The components produced during the changeover are discarded until the desired aesthetic quality is achieved, requiring downtime. Conventionally, setting the sequence for opening the injectors during the color change is left to the discretion of the operator, which may not be optimal or repeatable.
The patent describes a method and means of color changeover that completely opens the peripheral injectors while keeping closed the central injector or injectors for a limited number of cycles. This “…allows minimizing both the time required to change color and the discarded pieces until the required aesthetic quality is attained with the relative reduction of waste of plastic material,” the patent states.
An optimized cycle of injector openings and closing can be programmed into the electronic control unit for each color change function, in some cases opening an injector to a minimum level so high injection pressure near the pin valve more easily removes residual material. These optimized cycles can be saved and selected by the operator to automate changeovers without requiring further operator intervention, according to the patent.
Patent 10,807,289; issued Oct. 20