Digitized die forming system for sheet metal and springback minimizing technique

A flexible production system for sheet metal parts was developed based on the "digitized die" concept. The system can produce a variety of three-dimensional parts without the need for conventional dies, and given only the geometry and the material information of the desired part. The digitized die forming (DDF) system includes the forming press, the shape control system, and software modules with the functions of forming process planning, digitized die shape design, forming process numerical simulation, and springback correction. The digitized die installed in the forming press is the kernel component of the system, it is composed of a pair of matrices of punches, and sheet metal is formed by the enveloping surface of the punches. The working surface of the digitized die are modeled by Non-Uniform Rational B-Spline (NURBS) and constructed by adjusting the height of each punch. Forming process simulation software was developed based on updated Lagrangian formulation and elastic-plastic material model of the finite element, it conducts the numerical simulation to predict the springback and forming defect that may occur in the forming process. A simulation-based approach to compensate for material springback was developed, by correcting the forming surface numerically, an accurate digitized die surface for desired part is obtained. In this paper, the overall structure of the DDF system and the methods of design and control of digitized die shape are described, the detailed steps of the die shape correction for springback and forming process simulation are explained. Applications of the system for the forming of typical sheet metal parts are described.