Patent ID: 8229598

Claim:
A vibration suppressing device for a machine tool having a rotary shaft for suppressing a chatter vibration generated when a rotary shaft is rotated, the device comprising: detecting member for detecting time-domain vibration due to the rotating rotary shaft; calculating member for calculating a chatter frequency and a frequency-domain vibration at the chatter frequency based on the time-domain vibration detected by the detecting member, and calculating an optimum rotation speed of the rotary shaft capable of suppressing the chatter vibration, when the calculated frequency-domain vibration exceeds a predetermined threshold value, using a k-value and phase information, in which the k-value is an integer portion of a value obtained by dividing the frequency of chatter vibration by a product of the number of tool blades and the rotary shaft rotation speed and the phase information is a decimal part of the value obtained by dividing the frequency of chatter vibration by a product of the number of tool blades and the rotary shaft rotation speed; storing member for storing the k-value and the phase information; and rotation speed controlling member for rotating the rotary shaft at the optimum rotation speed calculated by the calculating member and the storing member, wherein the calculating member compares the calculated phase information with a predetermined constant to determine whether a generated chatter vibration is a forced chatter vibration or a regenerative type chatter vibration, determines whether a chatter vibration different from the determined chatter vibration determined before the current vibration is generated by using the phase information stored in the storing member, and changes the k-value according to an existence of generations of the determined chatter vibration and the different chatter vibration, so as to calculate the optimum rotation speed.