Patent ID: 8005574

Claim:
A vibration suppressing method for suppressing chatter vibration generated upon rotation of a rotary shaft in a machine tool including the rotary shaft for rotating a tool or a work, the method comprising: a first step for detecting a time-domain vibration due to the rotary shaft during rotation; a second step for calculating a chatter frequency and a frequency-domain vibrational acceleration at the chatter frequency based on the detected time-domain vibration; a third step for calculating a k number and a k′ number by following calculation formulae (1) and (2) and storing these numbers as machining information where the calculated frequency-domain vibrational acceleration exceeds a predetermined threshold value; a fourth step for calculating an expected stable rotation speed by following calculation formula (3) using the calculated k number and corresponding rotation speed of the rotary shaft for the expected stable rotation speed; a fifth step for changing the rotation speed of the rotary shaft from the expected stable rotation speed where the frequency-domain vibrational acceleration exceeds again the predetermined threshold value in the rotary shaft during rotation at the expected stable rotation speed; a sixth step for calculating a k″ number using calculation formula (1) with the expected stable rotation speed, where the frequency-domain vibrational acceleration further exceeds the predetermined threshold value after executing the fifth step; a seventh step for comparing an amount of change being a difference between the calculated k″ number and the k′ number stored as machining information with a predetermined phase threshold value, and updating the k″ number as the k′ number where the amount of change does not exceed the phase threshold value; and an eighth step for changing the rotation speed of the rotary shaft, calculating the k″ number, and updating the k′ number until the amount of change exceeds the phase threshold value, and keeping the rotation speed when the amount of change exceeds the phase threshold value as a stable rotation speed: k ′ number={60×chatter frequency/(the number of tool flutes×rotation speed)}; Calculation formula (1): k number=integer part of k′ number; Calculation formula (2): and expected stable rotation speed=60×chatter frequency/{the number of tool flutes×( k number+1)} Calculation formula (3).