Control System Of Easy-open-end Dies’ Nick Depth

Go deep in research the structure and manufacturing process of the easy-open-ends and find that the nick depth is the key factor impacting on the quality of an easy-open-end. In order to ensure product quality, the machines have to stop, and a shim would be added or taken away from the bottom of an easy-open-end die. The worse, all the things, like when to stop and how thick should the shim be, are done according to experiences of the workers. The method mentioned above is low efficiency. So it’s necessary to make a research for the on-line control of an easy-open-end’s nick depth. The easy-open-end’s nick depth can be micro adjusted by heating or cooling the die, according to the property substances expanding when heated and contract when cooled. Induction heating is chosen as the heat method in this article. Heating by induction heating, the die’s temperature up soon and distributes evenly. The control system is of a three-series loop with feedback-feed forward for compound control. Output of main loop is a die’s changing depth. There is an interference due to cutting die’s skip off in the main loop. And the interference can affect the output of main loop. Therefore, the feed-forward control strategy is used to suppress interference and improve the system stability. The minor loop is about temperature control. A Smith predictive control method was adopted for the time-delay system Lots of simulation and experiment have also been done, the result shows the feasibility and practical applicability of the system. And the control system can keep the temperature accuracy at0.3℃, correspondingly, the changing depth of an easy-open-end die is2.1μm, and time constant of control plant is100seconds. Compare with the system’s performance target which requires easy-open-end’s nick depth changing between-3μm and+3μm, the control system designed in this article achieves good control result.