| 摘要 |
A numerically controlled machine tool having a tool secured to a support for machining a surface of a workpiece. The tool is also used for sensing the workpiece surface for measuring the distance between the workpiece surface and a datum surface. To this end, the tool is at first moved to a position clear of the workpiece surface and an electric circuit between the tool and the workpiece switched on. The tool is then moved toward the workpiece surface by a control system adapted to continually read the position of the tool by means of a counter. When the tool touches the workpiece the circuit is made and produces a signal used to read the instantaneous content of the counter into a computer. The computer determines the difference between the actual and demanded dimension of the workpiece surface and corrects the next machining position of the tool accordingly. In a modification, the signal generated when the tool touches the workpiece is produced by a piezo-electric crystal embodied in the tool and adapted to sense the force on the tool when the latter engages the workpiece. In a further modification a clamp bolt securing the tool to the support is released to allow the tool to slide on the support as the support continues to move after the tool engages the workpiece surface. The commencement of this sliding is used to produce the signal. The extent of the sliding may be used to measure the difference between the actual and demanded dimension.
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