| 摘要 |
<p>A bed is provided that is adapted to support the workpiece, the bed having a nonplanar supporting surface so that when the workpiece is supported by, a number of evacuation spaces are formed between the lower surface of the workpiece and the nonplanar surface of the bed. The bed is also provided with a number of vacuum ports that extend through it, which ports are in fluid communication with the evacuation spaces so that at least one port communicates with each such space. In the practice of the method a continuous flexible tape is secured to and along the peripheral edge of the workpiece, which tape has a continuous flexible lip portion that curves generally outwardly from the edge of the workpiece. The workpiece with the tape secured to it is placed on the supporting surface of the bed so as to form a number of evacuation spaces between the lower surface of the workpiece and the nonplanar surface of the bed. Vacuum ports in the bed that are located outside the periphery of the workpiece are blocked or closed, and a vacuum is pulled through the open vacuum ports and evacuation spaces beneath the workpiece so as to hold the workpiece on the bed. In the practice of this method, the lip portion of the tape will seat on the surface of the bed so as to form a seal between the tape and the surface of the bed at the periphery of the workpiece.</p> |
