| 摘要 |
When a blank is cut from metal sheet which suffers from crystallographic anisotropy, there is a tendency for ears to be formed during subsequent forming operations, such as drawing or pressing. In order to compensate for this tendency, there may be used a metal blank which is not completely round, but has lobes at positions to cancel at least some of the valleys between the ears. There is described a punch (110) and die (111) which may be used to form such a lobed blank (112). The punch (110) has four circumferentially extending lobe-forming sections (124). Each lobe-forming section is constructed by forming a stepped recess in the cutting edge of the punch (110). In each lobe-forming section, the depth of the recess varies from a maximum at the middle of the section to zero at the ends. The die (111) is conventional. |
