Patent ID: 9687900
Date: 2017-06-27
CPC Classifications: B21D,B23D

Claim:
1. A method for working a steel sheet into a predetermined shape, comprising: a drawing step for drawing the steel sheet using at least one pair of dies; and a cutting step for cutting the steel sheet drawn in the drawing step using at least one nibbler, wherein the nibbler has a cylindrical case, a punch housed in the case, which reciprocates in a top-bottom direction to punch the steel sheet, and a die arranged below the case so as to be on the opposite side of the case across the steel sheet, the die having a die hole into which the punch enters, and an ejecting hole communicating with the die hole, through which a scrap punched from the steel sheet is ejected, and in the cutting step, while moving the nibbler, the steel sheet fed between the case and the die is continuously punched by the punch to cut the steel sheet, wherein in the drawing step, a bead protruding toward a side where one of both surfaces of the steel sheet is situated is formed in a ring on a peripheral part of the steel sheet over the whole circumference of the peripheral part, a low part having a height smaller than the shortest distance between the case and the die of the nibbler is formed in at least one part of the bead, in the cutting step, a part of the peripheral part including the bead is cut out by moving the nibbler over the low part from a periphery of the steel sheet to a part of the steel sheet situated inward from the bead and changing the cutting direction of the nibbler.