Importance

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Abstract

Disclosed is a numerical control apparatus for controlling a numerically controlled machine tool such as a hobbing machine and the like. An axis control circuit (14) provided with a synchronization control means (8) controls the rpm of a spindle motor (5) and the rpm of a servo motor (11) based on feedback pulses supplied from a position coder (7) connected to a hob axis (3), so that a ratio of the rpm of the hob axis (3) to the rpm of a C-axis (13) has a given value. A first internal counter (15a) monitors the number of feedback pulses supplied from the position coder (7) and a second internal counter (15b) monitors the number of pulses distributed to the C-axis (13), and when a ratio of the rpm of the hob axis (3) to the rpm of the C-axis (13) is to be changed, a correction pulse calculation means (9) calculates correction pulses based on the number of rotation pulses of the hob axis (3) and the number of the rotation pulses of the C-axis (13) counted by the first and second internal counters (15a, 15b). The correction pulses are supplied to the C-axis (13) to accelerate or decelerate the rpm of the C-axis (13) and thereby achieve a new synchronous relationship between the hob axis (3) and the C-axis (13) during the rotation of the hob axis (3) and C-axis (13).

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First Claim