Precision Forming of Electric and Electronic Small Parts Made of Metal Foil Using Multi-functional Forming Machine

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The blankholding pressure required to prevent wrinkling increased considerably with a decrease of blank thickness. The maximum deep-drawing stress also increased greatly with an increase of the blankholding pressure, according to the decrease of blank thickness. Fractures and wrinkles in deep drawing of metal foil occurred easily and the formability deteriorated. In order to form very thin shells without failure, blankholding pressure should be loaded along optimum paths. In addition to the failure due to the decrease of blank thickness, tooling imperfections such as ununiform contact between tools and the foil blank, unequal clearance along the circumference and inaccurate alignment between the punch, die and blank greatly influence the onset of wrinkling and fracturing. The use of auxiliary sheets in the formation reduced the influence of tooling imperfections and prevented wrinkling and fracturing.Piercing fine holes in very thin sheets is important in manufacturing miniaturized parts. In piercing process by means of explosive-impulsive pressure, a punch is not required but only a die cavity is required. This process will be very effective for piercing fine holes. The explosive-impulsive intensity strongly influenced the state of pierced holes. The optimum intensity improved the quality of the pierced holes. The kind of foil materials and their mechanical properties also influenced the pierced holes.