Patent ID: 7661342

Claim:
A method for making a metallic workpiece, comprising: (a) providing a metallic sheet and a punching machine, wherein the metallic sheet comprises a curved portion, and a plurality of predetermined punching areas defined on the curved portion for being punched; the punching machine comprises a die set, a lifter disposed above the die set, a punch blade disposed at a bottom end of the lifter, a controller, a mechanical arm, and at least an emitter-sensor pair consisting of a laser emitter and a laser sensor disposed on a bottom end of the lifter on opposite sides of the punch blade, the laser emitter and the laser sensor disposed symmetrically relative to a longitudinal center axis of the punch blade, the mechanical arm and the lifter being controlled by the controller; (b) placing the metallic sheet on the die set; (c) determining whether a longitudinal center axis of the punch blade is perpendicular to a plane tangential to a center of the predetermined punching areas and adjusting a position of the metallic sheet for making the longitudinal center axis of the punch blade perpendicular to the plane tangential to the center of the predetermined punching areas; (d) applying the lifter to press downward, such that the punch blade punching one of the predetermined punching areas out of the metallic sheet; and (e) repeating steps (c) and (d) appropriately in turn to form a plurality of punched holes in the curved portion of the metallic sheet, whereby the metallic workpiece is formed.