| 摘要 |
An numerical control (NC) device capable of machining a workpiece with high accuracy by accurately commanding a feed speed of a tool, even if a sudden change occurs in an actual speed of a spindle motor. If a rotational speed of a spindle changes, a change amount calculation/storage device calculates and stores a change amount on the basis of the rotational speed already detected. A rotational speed detected by a rotational speed detection device is corrected thereafter according to the change amount, and a proper feed speed is commanded from a feed speed control device. If thread cutting is carried out by employing the NC device, the tool feed speed is commanded in proportion to the actual speed of the spindle motor, and therefore, even though the rotational speed of the spindle motor is lowered at the moment the workpiece is started to be subjected to thread cutting by the tool, a move command signal with a proper tool feed speed is outputted.
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