Development of Incremental Forming by Simultaneous Control of Bending and Twisting

Abstract

In the press forming of various small-quantity products used in social infrastructure products, the increase in forming cost and die adjustment based on expert know-how have become issues. For these reasons, the development of flexible forming technology has been promoted. In this study, from the application viewpoints of high accuracy and cost reduction for the impeller used in the pump and the compressor, we have developed an incremental method that sequentially repeats bend and twist forming accomplished with a pair of straight punches and a pair of clamps. Since this method incrementally forms the material, the shape error of the final shape becomes the accumulation of forming errors in each forming element. Thus, in the forming of each element, in-process shape evaluation and feedback to the forming conditions are performed. To achieve this, we constructed a process control system with shape correction and a condition database, using the amount of bending and twisting, and the spacing between the two linear punches as process control factors. In addition, we developed new forming equipment with the process control system and verified its use in the forming of impeller blades (approx. overall length 210 mm). As a result of the shape evaluation of the formed blades, while an error of 0.5 to 1.0 mm occurred at the edges of the segment line, the error in almost regions of the formed blades was within ± 0.5 mm. Thus, it was confirmed that forming can be performed flexibly without using a pair of punches and clamps.