Preface.

Stamping is a long-established, widely used industrial process for economical high-volume production. It is used extensively in the automotive industry, as well as for production of white goods and many other products. In this book we present an approach, based on process control, to improve stamped part quality at reduced cost by eliminating tearing, wrinkling and springback. The concept is straightforward: measure punch forces and then adjust the blank holder (i.e., binder) forces (i.e., how tightly we hold the blank material in place) at various locations around its periphery and at various times during the stamping process to properly control the draw-in of blank material into the die. Of course, how to do this is the challenge! This book describes in detail how this simple goal can be achieved through real-time control technology. A reconfigurable set of hydraulic actuators (e.g., 12–24) is placed under the die to enable the control of the blank holder forces at various locations around the die periphery. These blank holder forces at each actuator are varied during the short duration (e.g., \1 sec) of the press stroke. The careful design of a controller, termed the machine controller, is needed to ensure that the desired blank holder forces are achieved at each hydraulic actuator and at each instant in time during the press stroke. Furthermore, we also measure the punch force during stamping, and design another controller, termed the process controller, to ensure that the desired punch force values are achieved during stamping despite the presence of disturbances (e.g., lubrication or material thickness variations). Maintaining the desired punch force leads to consistent draw-in of blank material and improves stamped part quality by eliminating wrinkling, tearing and springback. In this book we describe the methods for designing these controllers, and present experimental validation results from die try-out tests. The proposed system has also been evaluated in pilot tests in production and has also been shown to improve the formability of hard-to-form materials, such as lightweight alloys. This book is the result of a multi-year research collaboration among the authors. We would like to thank the State of Michigan’s Twenty-first Century Fund for their financial support of this research project, and also thank our industrial collaborators Troy Design And Manufacturing (TDM) Company, Ogihara America Corporation and OPAL-RT Technologies. The real-time computer control equipment used was provided by OPAL-RT. The die try-out tests, and the experimental results presented in the book, were