Importance

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Abstract

There is provided a thread cutting control method in an NC apparatus having a CPU in an arithmetic unit whereby real time clocks which are generated for every constant time are received as an interruption signal and a sampling operation is performed in response to the interruption signal, thereby controlling the feed system of a machine tool having a thread cutting function. In this system, the rotational speed of a spindle which is rotating asynchronously with the real time clocks is measured; the rotational amount of the spindle from a predetermined position on the rotational position of the spindle until the real time clock is just generated is measured; and after a feed system adapted to perform a thread cutting work on the basis of the rotational amount and the rotational speed has moved by a predetermined distance, a feed command to control the feed system is generated such that the movement distance is constant for the position of the spindle and at the same time, a predetermined ratio is held between the feed speed of the feed system and the rotational speed of the spindle. With this system, the feed shaft to cut the thread lead can be controlled with a high degree of accuracy.

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First Claim