| 摘要 |
The holes in the plate, which plates are used, in particular, as supporting plates for tube bundles in heat exchangers, are produced by combined punching and embossing. The combined punching and embossing tool used has, starting from the cutting edge, a conically tapering portion (5) with a taper of about 1-2 DEG and, adjoining this conical portion (5), a widening embossing portion (a). The circumferential wall of this embossing portion is a surface of revolution with a generatrix which follows an ellipse or an oval course, adjoins the circumferential surface of the conical portion (5) without a kink and has a radius of curvature (r2, r3) which increases gradually or in steps. The radius of curvature is initially about 0.6-1 mm and increases in such a way that the embossing portion has an axial height (a) of about 1-4 mm. This combined punching and embossing tool produces holes with an edgeless entry rim rounded with a radius of curvature of about 0.8-5 mm in axial section, a cylindrical portion free from scale and a conical punch break-out portion, with the result that no sharp edges or burrs come into contact with the tubes. <IMAGE>
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