Development of CNC incremental forming machine with touch sense and its application to intelligent metal-flow control in sheet metal forming operation

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An incremental stretch-expandling is a process in which a sheet metal is stretch-expanded to fit on a tool-envelope surface made by relative motion of a tool around the sheet metal. The incremental forming process seems to be suited to small-lot production from viewpoint of a die-less forming operation, and is also thought to be important in metal-flow control operation. This study presents the development of the CNC incremental forming machine with touch sense in which the motion of the cylindrical tool can be controlled by a computer, made to imitate a figer motion in potter's wheel operation, and its application to intelligent metal-flow control in sheet metal stretch-expanding. Various kinds of axisymmetrical shell components, such as bulygy pot-shaped shell and deep cylindrical shell, were stretch-expanded by the developed machine. Effect of tool path schedules on strain distribution and limit in the shell components was examined using aluminum, aluminum alloy and copper sheets. It is found that the tool path schedules has influence on strain distribution in shell components, and the associated metal-flow has influence on the forming limit and large deflection. Experimental results suggest that the metal flow phenomena can be estimate qualitatively by the touch information between the tool and the sheet metal during the forming operation. Therefore, theproposed process by the developed machine with touch sense is useful for intelligent metal-flow control in sheet metal forming operation.