| 摘要 |
<p>A numerically controlled machine tool has a tool 12 on a support 13 for machining surface 11A of a workpiece 11, and for sensing the surface for measuring a dimension 43 between it and a datum surface 29. The tool is first moved to a position 44 clear of the surface 11A and an electric circuit 31 between the tool and the workpiece is switched on. The tool is then moved toward the surface 11A by a control system 17 which reads tool position by counter 39. When the tool touches the workpiece the circuit produces a signal 32 to read the content 43A of counter 39 into computer 37. This determines the difference between the actual and demanded dimension of the surface 11A and corrects the tool position accordingly. Alternatively, the signal 32 is produced by a piezo-electric crystal in the tool 12 to sense force when the tool engages the workpiece. Or the tool 12 is allowed to slide on the support, and the extent of the sliding used to measure the difference between actual and demanded dimensions. <IMAGE></p> |
