Vibration suppressing device and vibration suppressing method for machine tool

Abstract

A vibration suppressing device and a vibration suppressing method that are capable of obtaining an accurate optimum rotation speed and shortening a time period from generation of chatter vibration to calculation of the optimum rotation speed are provided. The vibration suppressing device 10 includes: vibration sensors 2a to 2c for detecting time-domain vibrational accelerations of a rotary shaft 3 in rotation; and a control device 5 for calculating a chatter frequency and a frequency-domain vibrational acceleration of the rotary shaft 3 at the chatter frequency on the basis of the time-domainvibrational accelerations detected by the vibration sensors 2a to 2c, and when the calculated frequency-domain vibrational acceleration exceeds a predetermined threshold value, calculating an optimumrotation speed on the basis of a predetermined parameter, and rotating the rotary shaft 3 at the calculated optimum rotation speed.

Description

technical field [0001] The present invention relates to a vibration suppressing device and a vibration suppressing method for suppressing vibration generated during machining in a machine tool that performs machining while rotating a tool or a workpiece. Background technique [0002] Conventionally, for example, there is a machine tool in which a workpiece is supported on a rotatable spindle, and a tool is fed to the workpiece while processing the workpiece. In this machine tool, when the amount of cut in the cutting process is greater than necessary, so-called "chatter" occurs during machining, and there is a problem that the finishing accuracy of the machined surface is deteriorated. At this time, self-excited vibration, that is, "regenerative chatter" is particularly problematic. In order to suppress this "regenerative chatter", as described in Patent Documents 1 and 2, the following techniques are known: Find the natural vibration frequency of the system that produces "...

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Problems solved by technology

[0006] However, in the method of the above-mentioned patent document 1, when obtaining the "natural frequency", an expensive pulse device is required, so there is a problem of high cost.

In addition, the vibration method of Patent Document 1 not only requires a high level of technology, but also has the difficulty of obtaining an accurate optimum rotation speed because the "natural frequency" measured before machining does not necessarily coincide with the "natural frequency" during machining. Such a problem of poor practicality

[0007] On the other hand, in the above-mentioned method of Patent Document 2, the "flutter frequency" is obtained by analyzing the whirling sound detected by the acoustic sensor, etc. Since there is a difference in the "flutter frequency" of the rotation speed, it is difficult to obtain an accurate optimum rotation speed similar to the method of the above-mentioned Patent Document 1

That is, in the case of calculating the "chattering frequency" from the whirling sound, etc., after detecting the vibrational frequency corresponding to the "chattering", the "chattering frequency" is obtained asymptotically by performing processing and measurement several times Therefore, it takes time to calculate the optimum rotation speed after the "chatter" is detected, and as a result, there is a problem that marks caused by high-frequency vibration remain on the processed surface

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