The multi-point forming (MPF) technology is a flexible forming method for three-dimensional sheet metal parts. In multi-point forming, the conventional stamping dies are replaced by a pair of matrices of elements (punches) and the relative positions of the elements can be varied to suit the requirements.
In the multi-point forming (MPF) for sheet metal, precisely constructing the die surface according to the geometry of parts is important for improving the dimensional accuracy and shape accuracy of products.
Today, a method based on NURBS surface is one of the generating methods of die surface using multi-point elements. This method can freely describe various curves and surfaces by using a general mathematical model. However, the NURBS method tends to lose data when the surface information (boundary information and shearing information, etc.) of product is obtained.
The method of representing complex geometry and location using triangular mesh data files (STL) is being widely used in the fields of high speed forming, inverse forming, finite element analysis, etc., and it is now widely accepted as the data exchange files of CAD/CAM/CAE systems. The triangular mesh model is convenient for processing and display on a computer, and it can represent any complex surface shape. Using the file of the triangular mesh data in a multi-point forming process can overcome the shortcomings of the NURBS method and solve the problem of data loss.
Paek Kuk Song, a researcher at the Faculty of Materials Science and Technology, has introduced the finite element theory into the construction of multi-point forming die surface to calculate the height of the elements according to the product geometry given by the triangular mesh data file (STL), and optimized the multi-point forming die surface by simulation analysis.
He performed the simulation analysis using ABAQUS software, and a full-scale experiment for the product that underwent the simulation analysis. The maximum absolute error between the target surface and the formed product was 0.09mm.
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