| 摘要 |
<p>The sheet (2), passing through an elongated aperture in the press, is gripped along the leading edge by the jaws (151) of a drawing head (15), under pressure applied by wedge faces (150) or hydraulically. These draw the sheet between fixed (161) and movable (162) die-bars, with rounded contact surfaces (165), retained by key-bars (131,141) in holder (13,14) mounted in the press frame. As the sheet advances, the movable holder and die-bar are raised towards their fixed counterparts, progressively reducing the thickness. The two motions are coordinated to achieve the required convergence angle between the opposite sides. Die-bar movement is produced by a motor-driven inclined plane interposed between the press frame and the holder (14). Lubricant is sprayed on sheet surfaces entering the die. Die-bars are of e.g. tungsten carbide, surface-treated to produce suitable hardness and coefficient of friction. The change in thickness is monitored and parameters adjusted to obtain the desired result. More than one pass may be required; opt., the sheet is treated successively in two differently set presses.</p> |
