JP2009190160A - Vibration suppression method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration suppression method and apparatus which, even when chatter continuously occurs, an accurate stable rotation speed is realized for vibration suppression without causing a gradual decrease or increase of the rotation speed. <P>SOLUTION: A vibration suppression apparatus 10 is provided with vibration sensors 2a to 2c that detect a chatter frequency and a vibration acceleration in a time domain in a rotation shaft 3 during rotation. The vibration suppression apparatus 10 is further provided with a control unit 5, wherein, when the vibration acceleration in the time domain detected with the vibration sensors 2a to 2c has exceeded a predetermined threshold value, a machining information determined using the chatter frequency is calculated and stored, and when an already stored machining information is present, a stable rotation speed, which suppresses chatter vibration of the rotation shaft 3, is calculated using at least the machining information. When any stored machining information is not present, the stable rotation speed is calculated using the calculated machining information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for suppressing vibration generated during processing in a machine tool that performs processing while rotating a tool or a workpiece, or a vibration suppression device capable of executing the method.

  As a conventional vibration suppression method for machine tools, a method described in Patent Document 1 below is known. In this vibration suppression method, in order to suppress regenerative chatter vibration as self-excited vibration that causes deterioration of the finishing accuracy of the machined surface, a natural frequency of a system in which chatter vibration such as a tool or a work is generated is obtained, A value obtained by multiplying and dividing by the number of tool blades and a predetermined integer is defined as a rotational speed (stable rotational speed). This natural frequency can be obtained by impulse excitation of a tool or a workpiece.

  Moreover, the thing of the following patent document 2 is also known as a vibration suppression method. In this vibration suppression method, a chatter frequency during machining of a system in which chatter vibration occurs is obtained, multiplied by 60, and a value obtained by dividing by the number of tool blades and a predetermined integer is used as the rotation speed. The chatter frequency during machining is obtained on the basis of the vibration frequency detected by the sound sensor during rotation by arranging a sound sensor near the tool or workpiece.

JP 2003-340627 A JP-T-2001-517557

  In the vibration suppression method of Patent Document 1, an expensive impulse device is required, and excitation using this device requires advanced technology and takes time. In addition, since the natural frequency obtained before processing does not necessarily match the natural frequency during processing, it is difficult to obtain an accurate optimum rotational speed.

  On the other hand, in the vibration suppression method of Patent Document 2, since the chatter frequency and the natural frequency during processing are slightly different from each other, it is difficult to obtain an accurate optimum rotational speed. And, it is conceivable to improve accuracy by estimating the natural frequency from the chatter frequency during machining, but when chatter occurs again after chatter suppression, the rotational speed has changed from before chatter suppression For this reason, the parameters (k value related to the stability limit diagram) used in the estimation of the natural frequency or the calculation of the stable rotational speed for suppressing chatter again often change, and when the k value changes in this way In some cases, the rotational speed gradually decreases or increases, and when this occurs, the rotational speed gradually decreases or increases each time chatter occurs.

  Therefore, the inventions according to claims 1 and 3 are vibrations that can obtain an accurate and stable rotational speed for vibration suppression without gradually decreasing or increasing the rotational speed even when chatter occurs intermittently. The object is to provide a suppression method and apparatus.

  In order to achieve the above object, the invention according to claim 1 is a machine tool having a rotating shaft for rotating a tool or a workpiece, in order to suppress chatter vibration generated when the rotating shaft is rotated. A vibration detecting method for detecting a vibration in the time domain due to the rotating shaft during rotation, and a chatter frequency and a frequency domain in the chatter frequency based on the vibration in the time domain detected by the detection step. And calculating and storing machining information determined using at least the chatter frequency when the calculated vibration acceleration in the frequency region exceeds a predetermined threshold, and the previously stored When machining information does not exist, a stable rotation speed capable of suppressing chatter vibration of the rotating shaft is calculated using the calculated machining information, and stored in advance. When the machining information exists, at least a calculation step for calculating the stable rotation speed using the processing information and a rotation speed control step for rotating the rotation shaft at the stable rotation speed calculated by the calculation step. It is characterized by having.

  In addition to the above object, the invention described in claim 2 is the above invention, in order to achieve the object of preventing the increase or gradual decrease of the stable rotational speed simply and efficiently by keeping the processing information constant. In the calculation step, when the previously stored machining information exists, the stable rotation speed is calculated using only the machining information.

  In order to achieve the above object, a third aspect of the present invention provides a machine tool having a rotating shaft for rotating a tool or a workpiece, in order to suppress chatter vibration generated when the rotating shaft is rotated. A vibration detecting device for detecting vibration in the time domain due to the rotating shaft during rotation, and a chatter frequency and a frequency domain in the chatter frequency based on the vibration in the time domain detected by the detecting means. And calculating and storing machining information determined using at least the chatter frequency when the calculated vibration acceleration in the frequency region exceeds a predetermined threshold, and the previously stored When machining information does not exist, a stable rotation speed capable of suppressing chatter vibration of the rotating shaft is calculated using the calculated machining information, and the previously stored When engineering information is present, it comprises at least a calculation means for calculating the stable rotation speed using this, and a rotation speed control means for rotating the rotation shaft at the stable rotation speed calculated by the calculation means. It is characterized by this.

  In addition to the above object, the invention described in claim 4 is the above invention, in order to achieve the object of simply and efficiently preventing the increase or gradual decrease of the stable rotational speed by keeping the machining information constant. In the calculation means, when the previously stored machining information exists, the stable rotation speed is calculated using only the machining information.

  According to the present invention, machining information is stored, and a stable rotation speed capable of suppressing chatter vibration of the rotating shaft is calculated based on the past machining information. Therefore, the calculation of the stable rotation speed is greatly different from the past stable rotation speed. Therefore, even if chatter occurs intermittently, it is possible to prevent the rotational speed from gradually decreasing or increasing.

  Hereinafter, an example of an embodiment according to the present invention will be described with reference to the drawings as appropriate. In addition, the form of this invention is not limited to the said example.

  FIG. 1 is a block diagram of a vibration suppression device 10 according to this example, FIG. 2 is a side view of a rotary shaft housing 1 to be subjected to vibration suppression, and FIG. 3 is a diagram showing the rotary shaft housing 1 from the axial direction. It is. The rotating shaft housing 1 includes a rotating shaft 3 that can rotate around the C axis, and the vibration suppressing device 10 suppresses chatter vibration generated on the rotating rotating shaft 3. The vibration suppression device 10 includes vibration sensors 2a to 2c as detection means for detecting vibration acceleration in the time domain generated on the rotating rotating shaft 3, and rotation of the rotating shaft 3 based on detection values of the vibration sensors 2a to 2c. And a control device 5 for controlling the speed.

  As shown in FIGS. 2 and 3, the vibration sensors 2a to 2c are arranged so as to detect the vibration acceleration in the time domain (vibration acceleration on the time axis) in the directions perpendicular to each other. It is attached to the rotary shaft housing 1 in a state where vibration acceleration in the time domain in the Z-axis direction can be detected.

  The control device 5 includes an FFT calculation device 6 that performs Fourier analysis based on vibration acceleration in the time domain detected from the vibration sensors 2 a to 2 c, calculation of a stable rotation speed based on a value calculated by the FFT calculation device 6, etc. And a NC device 8 as a rotational speed control means for controlling machining in the rotary shaft housing 1. The NC device 8 of the control device 5 monitors the rotational speed of the rotary shaft 3. Note that the FFT arithmetic unit 6 or the stable rotational speed arithmetic unit 7 corresponds to an arithmetic unit.

  An example of a vibration suppression method for chatter vibration by the vibration suppression device 10 configured as described above will be described with reference to FIGS. 4 and 5. FIG. 4 shows an example of a Fourier analysis result of vibration acceleration in the time domain, and FIG. 5 shows a flowchart of the suppression control.

  First, the FFT arithmetic unit 6 performs a Fourier analysis on the time domain vibration acceleration that is always detected by the vibration sensors 2a to 2c during rotation, and the maximum acceleration and its frequency 4 (chatter frequency) as shown in FIG. ) Is constantly calculated (step S1, detection step in FIG. 5). When Fourier analysis is performed on the vibration acceleration in the time domain, a plurality of waveforms as shown in FIG. 4 showing the relationship between the frequency and the vibration acceleration in the frequency domain are acquired. In this embodiment, the vibration acceleration in the frequency domain is acquired. The waveform with the maximum value is used.

Next, the stable rotation speed calculation device 7 compares the vibration acceleration in the frequency domain calculated by the FFT calculation device 6 with a preset threshold value, and the vibration acceleration in the frequency domain has exceeded a predetermined threshold value. In the case (for example, when vibration acceleration in the frequency domain at frequency 4 in FIG. 4 is detected), it is assumed that chatter vibration to be suppressed occurs on the rotating shaft 3, and the following equations (1) and (2) are used. The k value is calculated and stored as machining information, and the stable rotational speed is calculated by the following equation (3) and output to the NC device 8 (step S2, calculation step, no machining information stored previously) If). Here, the processing information indicates a k value and a k ′ value here. Further, the number of tool blades is set in advance in the stable rotation speed calculation device 7. Further, the rotation shaft rotation speed is the current rotation speed of the rotation shaft 3 before the stable rotation speed. In addition, the chatter frequency is a frequency 4 when chatter vibration occurs.
k ′ value = 60 × chat frequency / (number of tool blades × rotating shaft rotational speed) (1)
k value = integer part of k ′ value (2)
Stable rotational speed = 60 × chat frequency / {number of tool blades × (k value + 1)} (3)

  Then, the NC device 8 that has received the output of the stable rotational speed from the stable rotational speed computing device 7 in step S2 changes the rotational speed of the rotary shaft 3 to the stable rotational speed (step S3, rotational speed control step). By setting the rotational speed of the rotary shaft 3 to the stable rotational speed, chatter vibration is suppressed and a stable machining state is achieved.

  Even when such a stable machining state due to suppression of chatter vibration is reached, the vibration sensors 2a to 2c detect vibration acceleration in the time domain (detection step). If chatter vibration occurs again and the vibration acceleration in the frequency domain exceeds a predetermined threshold value, the machining information is calculated again and a stable rotational speed is output in the same manner as in step S2, but the calculated k value is When it differs from the previously stored k value (in step S2), the calculated k value is replaced with the stored k value to calculate the stable rotation speed (step S4, calculation step, previously stored machining information is If any). In step S4, the stable rotation speed may be calculated based on the stored k value without calculating the machining information.

  Receiving the output of the stable rotational speed from the stable rotational speed calculation device 7 in step S4, the NC device 8 changes the rotational speed of the rotary shaft 3 to the stable rotational speed (step S5, rotational speed control step). By setting the rotational speed of the rotary shaft 3 to the stable rotational speed, chatter vibration is suppressed and a stable machining state is obtained again. Further, since this stable rotation speed is calculated based on the same k value as before (step S2), it is substantially the same as the previous stable rotation speed and does not deviate from the previous stable rotation speed.

  Further, when the vibration acceleration in the frequency domain again exceeds a predetermined threshold after such a stable machining state (when chatter vibration occurs intermittently), detection by the vibration sensors 2a to 2c and steps S4 and S5 are performed. Is repeated to set the rotational speed of the rotary shaft 3 to a new stable rotational speed, thereby obtaining a stable machining state. Since this new stable rotation speed is also calculated based on the same stored k value as in the previous step S4, it becomes the same as the previous stable rotation speed and does not deviate from the previous stable rotation speed, and chatter vibration. Even if this occurs intermittently, the stable rotational speed does not continue to decrease or increase continuously.

  In the vibration suppression device 10 described above, since the stable rotation speed is calculated with the k value being constant based on the k value calculated and stored from the past machining result, chatter vibration is generated intermittently. However, the stable rotational speed can be made not greatly different from the previous rotational speed, and the gradual decrease or increase of the rotational speed of the rotating shaft 3 can be prevented, and the machining surface is made high-quality while considering the efficiency. Can keep. Moreover, since the change of the rotational speed of the rotating shaft 3 is small, it is possible to prevent a situation in which an excessive load is applied to the tool and the spindle.

  In addition, the other form of this invention which mainly consists of changing the said form is illustrated. For the k value, the past several times (for example, 5 times) are stored together, and the average value for the predetermined number of times (for example, 5 times) is rounded off to be a new k value or the most within the predetermined number of times (for example, 5 times). Even in these cases, the unidirectional increase or gradual decrease in the rotational speed can be prevented. Further, at the time of Fourier analysis by the control device, vibration frequencies in vibration accelerations in a plurality of upper (for example, upper three) frequency regions may be extracted, and a stable rotation speed may be calculated using these vibration frequencies. Furthermore, instead of or along with the vibration acceleration of the rotation shaft, a sound pressure generated by displacement or rotation due to vibration may be detected and used for calculation of a stable rotation speed.

  In addition, the detecting means can be arranged on the fixed side (workpiece and / or its vicinity) instead of the rotating shaft side or together with the rotating shaft side. Furthermore, the present invention can also be applied to other machine tools such as a lathe for rotating a workpiece. In a machine tool that rotates a workpiece, it is possible to detect vibration on the spindle side that holds the workpiece, or to detect vibration on the tool side that is the fixed side. Further, the number and arrangement of detection means may be appropriately changed according to the type and scale of the machine tool. Furthermore, various arithmetic devices can be integrated or separated, and a separate storage device can be provided in addition to the arithmetic devices.

It is a block diagram of the vibration suppression device concerning the present invention. It is side surface explanatory drawing of the rotating shaft housing in FIG. It is explanatory drawing at the time of seeing the rotating shaft housing in FIG. 1 from an axial direction. It is a figure which shows an example of the Fourier-analysis result about the vibration acceleration of the time domain performed with the control apparatus of FIG. It is a flowchart of the vibration suppression method performed in the vibration suppression apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft housing 2a, 2b, 2c Vibration sensor 3 Rotating shaft 5 Control device 6 FFT computing device 7 Stable rotational speed computing device 8 NC device 10 Vibration suppression device

Claims (4)

In a machine tool having a rotating shaft for rotating a tool or a workpiece, a vibration suppressing method for suppressing chatter vibration generated when the rotating shaft is rotated,
A detecting step for detecting vibration in the time domain due to the rotating shaft during rotation;
Based on the vibration in the time domain detected by the detection step, the vibration frequency and the vibration acceleration in the frequency domain at the chatter frequency are calculated, and when the calculated vibration acceleration in the frequency domain exceeds a predetermined threshold, Calculate and store machining information determined using at least the chatter frequency, and can suppress chatter vibration of the rotating shaft using the calculated machining information when the previously stored machining information does not exist Calculating a stable rotational speed, and when the previously stored machining information is present, at least a calculation step for calculating the stable rotational speed using this, and
A vibration suppression method comprising: a rotation speed control step of rotating the rotation shaft at a stable rotation speed calculated in the calculation step. 2. The vibration suppressing method according to claim 1, wherein in the calculation step, when the previously stored machining information exists, the stable rotation speed is calculated using only the machining information. In a machine tool provided with a rotating shaft for rotating a tool or a workpiece, a vibration suppressing device for suppressing chatter vibration generated when the rotating shaft is rotated,
Detection means for detecting vibration in the time domain due to the rotating shaft during rotation;
Based on the vibration in the time domain detected by the detection means, the vibration frequency and the vibration acceleration in the frequency domain at the chatter frequency are calculated, and when the calculated vibration acceleration in the frequency domain exceeds a predetermined threshold, Calculate and store machining information determined using at least the chatter frequency, and can suppress chatter vibration of the rotating shaft using the calculated machining information when the previously stored machining information does not exist A calculation means for calculating the stable rotation speed using at least the calculation information when calculating the stable rotation speed and the previously stored machining information exists,
A vibration suppression apparatus comprising: a rotation speed control unit that rotates the rotation shaft at a stable rotation speed calculated by the calculation unit. 4. The vibration suppressing device according to claim 3, wherein, when the machining information stored previously is present in the arithmetic means, the stable rotation speed is calculated using only the machining information.

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