JP5301946B2 - Vibration suppression method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for suppressing vibration capable of obtaining more accurate and stable rotational speed when chatter vibration occurs continuously, and surely suppressing the chatter vibration. <P>SOLUTION: Whenever the chatter vibration is detected, a phase &epsi;1 is calculated and the calculated phase &epsi;1 is compared with a phase &epsi;0 calculated last time the chatter vibration is detected. In the case where the phase &epsi;1 calculated this time is smaller than the phase &epsi;0 calculated last time, the phase &epsi;1 calculated this time is renewed and stored as the phase &epsi;0, and the rotational speed of a rotating shaft is changed by the predetermined amount of change. On the other hand, in the case where the phase &epsi;1 calculated this time is equal to the phase &epsi;0 calculated last time or more, the rotational speed of the rotating shaft is changed to the last rotational speed. As a result, machining can be performed with a rotational speed having a minimum phase value, and the quality of the surface to be machined can be improved, and tool wear can be suppressed. <P>COPYRIGHT: (C)2010,JPO&amp;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, and a vibration suppression device capable of executing the method.

  Conventionally, for example, a method described in Patent Document 1 is known as a vibration suppression method for machine tools. 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, The value obtained by multiplying and dividing by the number of tool blades and a predetermined integer is taken as the stable rotation speed. And it is going to suppress the chatter vibration which generate | occur | produces during a process by processing at the said stable rotational speed. The natural frequency is obtained by impulse vibration of a tool or workpiece.

  A vibration suppression method described in Patent Document 2 is also known. In this vibration suppression method, chatter vibration during machining of a system in which chatter vibration occurs is obtained, and this is multiplied by 60 and machining is performed with a value obtained by dividing the number of tool blades and a predetermined integer as a stable rotation speed, thereby causing chatter vibration. It is intended to suppress. The chatter frequency during machining is obtained based on 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

However, the vibration suppression method described in Patent Document 1 requires an expensive impulse device, and the vibration using this device requires a high level of technology and is troublesome. In addition, since the natural frequency obtained before machining does not always match the chatter frequency generated during machining, there is a problem that it is difficult to obtain an accurate stable rotational speed.
On the other hand, in the vibration suppression method described in Patent Document 2, the chatter frequency obtained by analyzing the rotational sound and the chatter frequency actually generated (natural frequency) are slightly different from each other. After all, it is difficult to obtain an accurate stable rotation speed. For this reason, the present applicant installs a detecting means for detecting the vibration in the time domain of the rotating rotating shaft and a calculating means for calculating the chatter frequency based on the vibration in the time domain, and more accurately. A vibration suppression device (for example, Japanese Patent Application No. 2007-138166) was devised to obtain the chatter frequency and to obtain an optimum stable rotation speed. However, in the vibration suppression device, due to the detection error of the detection means, a calculation error occurs between the chatter frequency calculated by the calculation means and the chatter frequency actually generated, and the rotating shaft rotates stably. It is possible that chatter vibration will continue despite the speed.

  Therefore, the present invention has been made in view of the above problems, and in the case where chatter vibration continues, a more accurate stable rotational speed can be obtained, and vibration that can reliably suppress chatter vibration. It is an object of the present invention to provide a suppression method and apparatus.

In order to achieve the above object, according to the first aspect of the present invention, in a machine tool having a rotating shaft for rotating a tool or a workpiece, chatter vibration occurs on the rotating shaft during rotation. A vibration suppressing method for suppressing the chatter vibration by changing the rotation speed of the rotation shaft, the first step of detecting time domain vibration due to the rotating shaft during rotation, and the detected time domain vibration Based on the second step of calculating the chatter frequency and the vibration acceleration in the frequency domain at the chatter frequency, and when the calculated vibration acceleration in the frequency domain exceeds a predetermined threshold, the phase ε1 is calculated by the following equation (1). And the phase ε1 calculated and stored in the same equation (1) as the phase ε1 when the previous vibration acceleration exceeds a predetermined threshold. A fourth step of compare, with comparison of the results in the fourth step, the calculated phase ε1 is smaller than the phase .epsilon.0 previously calculated updates stored phase ε1 calculated this time as a phase .epsilon.0, of the rotary shaft While the rotation speed is changed by a predetermined change amount, if the calculated phase ε1 is equal to or greater than the previously calculated phase ε0 as a result of the comparison in the fourth step, the rotation speed of the rotating shaft is calculated at the time of calculating the phase ε0. The fifth step of changing to the rotation speed is executed.
Arithmetic Formula (1): Decimal Part of Phase ε1 = {60 × Chatter Frequency / (Number of Tool Blades × Rotational Speed)} Note that “vibration” detected by the first step according to claim 1 is vibration acceleration. In addition to vibration itself, such as displacement due to vibration and sound pressure due to vibration, it includes a physical change that occurs on the rotating shaft due to vibration and can indirectly detect vibration.

On the other hand, according to the second aspect of the present invention, in a machine tool having a rotating shaft for rotating a tool or a workpiece, when chatter vibration occurs on the rotating shaft that is rotating, the rotating speed of the rotating shaft is changed. A vibration suppressing device for suppressing the chatter vibration, the detecting means for detecting the vibration in the time domain of the rotating shaft during rotation, and the chatter frequency and the chatter frequency based on the detected vibration in the time domain A first computing means for calculating the vibration acceleration in the frequency domain in the case, and a second computing means for calculating the phase ε1 by the following formula (1) when the calculated vibration acceleration in the frequency domain exceeds a predetermined threshold value: When the previous vibration acceleration exceeds a predetermined threshold value, the storage means for storing the phase ε0 calculated by the same calculation formula (1) as the phase ε1 by the second calculation means, and the second calculation means are the phase ε1 When output, when the calculated the phase ε1 said comparing the phase ε0 stored in the storage means, the calculated phase ε1 is smaller than the phase ε0 calculated last time, updates the phase ε1 calculated this time as the phase ε0 While storing, the rotational speed of the rotary shaft is changed by a predetermined change amount, and when the calculated phase ε1 is equal to or larger than the previously calculated phase ε0, the rotational speed of the rotary shaft is set at the time of calculating the phase ε0. Control means for instructing to change to the rotation speed and rotation speed control means for controlling the rotation speed of the rotating shaft are provided.
Operational expression (1): Phase ε1 = {60 × chatter frequency / (number of tool blades × rotational speed)} decimal part Note that “vibration” detected by the detection means in claim 2 is also “ This is the same as “vibration”.

According to the present invention, when “chatter vibration” occurs, the phase ε1 at the rotational speed is calculated, and the phase ε1 is compared with the phase ε0 at the rotational speed when the previous vibration acceleration exceeds a predetermined threshold. Since the rotation speed of the rotating shaft is changed according to the result, it is possible to cope with the situation, and the influence of “regenerative chatter vibration” can be suppressed more than before.
In particular, the phase ε1 at the current rotational speed is compared with the phase ε0 at the previous rotational speed, and when the phase ε1 becomes equal to or greater than the phase ε0, the rotational speed is converted to the previous rotational speed (that is, the rotation at the time when the phase ε0 is calculated). By changing to (speed), it becomes possible to perform processing at a rotational speed at which the phase value is minimized. Therefore, the occurrence of “regenerative chatter vibration” can be more effectively suppressed, and as a result, the quality of the machined surface can be improved, and tool wear can be suppressed.

Hereinafter, a vibration suppressing method and apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating the vibration suppressing device 10. FIG. 2 is an explanatory view showing the rotary shaft housing 1 to be subjected to vibration suppression from the side, and FIG. 3 is an explanatory view showing the rotary shaft housing 1 from the axial direction.

  The vibration suppressing device 10 is for suppressing “chatter vibration” generated in the rotating shaft 3 provided in the rotating shaft housing 1 so as to be rotatable around the C axis, and is a time generated in the rotating rotating shaft 3. Vibration sensors (detection means) 2a to 2c for detecting the vibration acceleration of the region (meaning vibration acceleration on the time axis), and the rotation speed of the rotary shaft 3 based on the detection values by the vibration sensors 2a to 2c And a control device 5 for controlling the control.

  As shown in FIGS. 2 and 3, the vibration sensors 2 a to 2 c detect time domain vibration accelerations in the X axis, Y axis, and Z axis directions orthogonal to each other in order to detect time domain vibration acceleration in directions perpendicular to each other. It is attached to the rotary shaft housing 1 in a state where vibration acceleration can be detected.

  The control device 5 also includes an FFT operation device 11 that performs Fourier analysis based on vibration acceleration in the time domain detected by the vibration sensors 2a to 2c, and a stable rotation speed based on the value calculated by the FFT operation device 11. Is provided with an arithmetic device 12 that calculates the above, an NC device (rotational speed control means) 13 that controls machining in the rotary shaft housing 1, and a storage device 14 that stores various numerical values calculated by the arithmetic device 12. ing. The NC device 13 monitors the rotational speed of the rotary shaft 3. In addition, the storage device 14 stores an initial value (ε0 = 1) of the phase ε0.

Here, a vibration suppressing method of “chatter vibration” by the vibration suppressing apparatus 10 as described above will be described based on the flowchart of FIG.
At the beginning of machining, the control device 5 controls the rotation operation of the rotary shaft 3 based on the flowchart of FIG.
First, the FFT arithmetic unit 11 performs Fourier analysis on the vibration acceleration in the time domain that is constantly detected by the vibration sensors 2a to 2c during the rotation of the rotating shaft 3 (S1), and the maximum acceleration (frequency domain) as shown in FIG. Vibration acceleration) and its frequency 4 (chatter frequency) are constantly calculated (S2). When Fourier analysis is performed on the vibration acceleration in the time domain, a plurality of patterns as shown in FIG. 4 showing the relationship between the frequency and the vibration acceleration in the frequency domain are acquired. Here, the vibration acceleration in the frequency domain is maximum. Is used.

  Next, the arithmetic device 12 compares the vibration acceleration in the frequency domain calculated by the FFT arithmetic device 11 with a predetermined threshold value (S3), and the vibration acceleration in the frequency region exceeds the 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 is expressed by the following equation (1). The phase ε1 is calculated (S4).

ε1 = {60 × chat frequency / (number of tool blades × rotational speed)} decimal part (1)
Here, it is assumed that the “number of tool blades” in the calculation formula (1) is set in the calculation device 12 in advance. The “rotation speed” in the calculation formula (1) is the current rotation speed. Furthermore, the chatter frequency is a frequency 4 when “chatter vibration” occurs.

Then, the calculated phase ε1 is compared with the phase ε0 stored in the storage device 14 (S5). When “chat vibration” is detected for the first time after the rotation of the rotating shaft 3, the phase ε0 is an initial value (that is, ε0 = 1), so that ε1 <ε0 (determination in S5 is YES). When the calculated phase ε1 is smaller than the phase ε0 stored in the storage device 14, the storage device 14 updates and stores the value of the phase ε1 calculated this time as the phase ε0, and the NC device 13 rotates. The speed is increased by a predetermined change amount ( S6 ). This change amount is stored in advance, and is, for example, a value of several percent (for example, 3%) of the rotational speed set at the start of machining.

  Then, after changing the rotational speed as described above, the process returns to S1, and the FFT arithmetic unit 11 performs a Fourier analysis on the vibration acceleration in the time domain that is always detected in the rotating shaft 3 rotating at the changed rotational speed, and The calculation of the maximum acceleration and its frequency 4 (chatter frequency) is continued, and the calculation device 12 compares the vibration acceleration in the frequency domain calculated by the FFT calculation device 11 with a predetermined threshold value set in advance. Perform (S3). Here, when vibration acceleration exceeding a predetermined threshold is detected again (determined as YES in S3), the phase ε1 is calculated again by the above equation (1) (S4), and the previously updated phase ε0 and this time The calculated phase ε1 is compared (S5), and if the currently calculated phase ε1 is smaller than the previously updated phase ε0, the phase ε0 in the storage device 14 is updated (that is, to the value of the currently calculated phase ε1). Update) and increase control of the rotation speed in the NC device 13 (S6). The steps from S1 to S6 are repeated until the determination in S6 is NO, that is, the phase ε1 is equal to or greater than the phase ε0. As a result of increasing the rotation speed in S6, when “chatter vibration” is not detected (that is, when the determination in S3 does not become YES), the increased rotation speed is increased until the end of machining. It will be maintained as a stable rotation speed.

On the other hand, when the chatter vibration is generated at the increased rotational speed and the phase ε1 calculated at that time becomes equal to or larger than the phase ε0, that is, the determination in S6 is NO, the NC device 13 reduces the rotational speed. Decrease by the amount of change increased last time (S7). That is, the fact that the phase ε1 calculated this time is equal to or larger than the phase ε0 stored in the storage device 14 (that is, the previously calculated phase ε1) means that the phase ε0 is the smallest as the phase value. The rotational speed of the rotating shaft 3 is returned to the rotational speed one stage before the smallest (the rotational speed immediately before). Then, the reduced rotation speed is set as a stable rotation speed, and the rotation speed is maintained until the end of machining ( S8 ).

Here, the suppression results of “chatter vibration” in the case where the rotational speed of the rotating shaft 3 is increased or decreased as described above and the rotational speed is changed only once as in the past will be described with reference to FIGS. 5 and 6. To consider.
Even if the rotation speed of the rotary shaft 3 is changed to the ideal rotation speed as a theoretical value based on the detection result (or the previous experimental result) after detecting “chatter vibration” as in the past. The vibration acceleration 7 at the chatter frequency (frequency 4) is reduced by only about 10% due to an error in the vibration detection value, a control error in the rotation speed, and the like (FIG. 5). In other words, even after the rotational speed is changed, “chat vibration” may occur intermittently.
On the other hand, when the control is executed to change the rotation speed every time the “chatter vibration” is detected as described above and maintain the rotation speed at which the phase finally becomes the minimum value as the stable rotation speed, FIG. As shown, the vibration acceleration 7 at the chatter frequency can be reduced by about 40%. 5 and 6, 6 indicates a change in rotational speed, 7 indicates a change in vibration acceleration at a chatter frequency, and 8 indicates a change in phase.

According to the vibration suppressing device 10 and the vibration suppressing method using the vibration suppressing device 10 as described above, when “chatter vibration” occurs, the phase ε1 at the rotational speed is calculated, and the phase ε1 and the previous rotational speed are calculated. The phase ε0 is compared and the rotational speed of the rotary shaft is changed according to the result, so that it is possible to cope with the situation and the influence of “regenerative chatter vibration” can be suppressed more than before. .
In particular, the phase ε1 at the current rotational speed is compared with the phase ε0 at the previous rotational speed, and when the phase ε1 becomes equal to or greater than the phase ε0, the rotational speed is converted to the previous rotational speed (that is, the rotation at the time when the phase ε0 is calculated). By changing to (speed), it becomes possible to perform processing at a rotational speed at which the phase value is minimized. Therefore, the occurrence of “regenerative chatter vibration” can be more effectively suppressed, and as a result, the quality of the machined surface can be improved, and tool wear can be suppressed.

  The configuration related to the vibration suppression method and apparatus of the present invention is not limited to the aspect described in the above embodiment, and the configuration related to the detection of chatter frequency and the control of vibration suppression is the gist of the present invention. As long as it does not deviate, it can change suitably as needed.

For example, in the above embodiment, the rotational speed of the rotary shaft 3 is changed according to the value of the phase ε1 to be calculated. The rate of change of the rotational speed at this time depends on the magnitude of the preset rotational speed or the tool blade. It is better to change it according to the number, dynamic characteristics, etc. That is, when the rotational speed is low, a change amount of about 10 min ⁻¹ is effective, but the higher the rotational speed, the wider the stable / unstable region. If it is not changed by about%, the vibration suppression effect may not be sufficiently obtained. Therefore, it is better to change appropriately according to the above conditions.

  In the above embodiment, when the calculated phase ε1 does not exceed the phase ε0, the rotational speed is increased. However, depending on the initially set rotational speed and various conditions, the determination in S6 is YES. In addition, the rotational speed may be decreased by a predetermined change amount. In this control, when the phase ε1 finally becomes equal to or greater than the phase ε0, the rotational speed is increased by a predetermined change amount, and the rotational speed is maintained as a stable rotational speed.

Furthermore, although the phase is 2π as described in the background art documents, etc., the rotational speed at which the “regenerative chatter vibration” is minimized is reduced, but the process of deriving the theoretical formula includes a calculation error. Therefore, when the rotational speed having a phase of 2π is obtained, the value does not necessarily become a stable rotational speed. Therefore, it is possible to obtain a more optimal stable rotational speed by using the following arithmetic expression (2) instead of the arithmetic expression (1) and correcting the phase for calculation.
ε1 = {60 × chat frequency / (number of tool blades × rotational speed) + A} decimal part (2)
Here, A in the arithmetic expression (2) is a predetermined constant, and a value close to 0 (for example, 0.1) is used.

Furthermore, in the above embodiment, vibration suppression control is performed using a waveform in which the vibration acceleration in the frequency domain is the maximum among the waveforms acquired by the Fourier analysis of the vibration acceleration in the time domain. The predicted stable rotational speed may be calculated using a plurality of (for example, three) waveforms having higher vibration acceleration values in the frequency domain, and the effect of suppressing “chatter vibration” may be further improved.
In the above embodiment, the detection means is a vibration sensor, but instead of this, a detection means capable of detecting the displacement of the rotating shaft and the sound pressure due to vibration may be employed. Furthermore, even when a vibration sensor is used, the vibration on the rotating side (that is, the rotating shaft) is not detected as in the above-described embodiment, but the vibration on the non-rotating side is detected, and the expected stable rotational speed is set. You may make it ask.
In addition, the vibration suppressing device according to the present invention is not limited to a machining center that rotates a tool and can also suppress vibrations of a machine tool such as a lathe that rotates a workpiece, and the installation position of the detection means Needless to say, the number and the like can be appropriately changed according to the type and size of the machine tool.

It is block block explanatory drawing of a vibration suppression apparatus. It is explanatory drawing which showed the rotating shaft housing from the side. It is explanatory drawing which showed the rotating shaft housing from the axial direction. It is explanatory drawing which showed an example of the Fourier-analysis result of the vibration acceleration of a time domain. It is explanatory drawing which showed the change of the vibration acceleration in the chatter frequency in the conventional vibration suppression control. It is explanatory drawing which showed the change of the vibration acceleration in the chatter frequency in the vibration suppression control of a present Example. It is a flowchart figure which concerns on the vibration suppression control of a present Example.

Explanation of symbols

  Rotating shaft housing, 2a, 2b, 2c, vibration sensor, 3 rotating shaft, 5 control unit, 10 vibration suppression device, 11 FFT processing device, 12 computing device, 13 ..NC device, 14 ..Storage device.

Claims (2)

In a machine tool provided with a rotating shaft for rotating a tool or a workpiece, when chatter vibration occurs on the rotating shaft that is rotating, a vibration suppression method that changes the rotation speed of the rotating shaft and suppresses chatter vibration. There,
A first step of detecting time domain vibration by the rotating shaft during rotation;
A second step of calculating a chatter frequency and a vibration acceleration in the frequency domain at the chatter frequency based on the detected vibration in the time domain;
A third step of calculating the phase ε1 by the following equation (1) when the calculated vibration acceleration in the frequency domain exceeds a predetermined threshold;
A fourth step of comparing the calculated phase ε1 with the phase ε0 calculated and stored in the same equation (1) as the phase ε1 when the previous vibration acceleration exceeds a predetermined threshold;
If the calculated phase ε1 is smaller than the previously calculated phase ε0 as a result of the comparison in the fourth step, the currently calculated phase ε1 is updated and stored as the phase ε0, and the rotational speed of the rotating shaft is changed by a predetermined change amount. On the other hand, if the calculated phase ε1 is greater than or equal to the previously calculated phase ε0 as a result of the comparison in the fourth step, the rotation speed of the rotating shaft is changed to the rotation speed at the time of calculating the phase ε0 . And a step of executing the vibration.
Arithmetic Formula (1): Phase ε1 = {60 × chatter frequency / (number of tool blades × rotational speed)} decimal part In a machine tool having a rotating shaft for rotating a tool or a workpiece, when chatter vibration occurs on the rotating shaft during rotation, vibration suppression is performed to change the rotation speed of the rotating shaft and suppress the chatter vibration. A device,
Detecting means for detecting vibration in the time domain of the rotating shaft during rotation;
First operation means for calculating a chatter frequency and vibration acceleration in the frequency domain at the chatter frequency based on the detected vibration in the time domain;
A second calculation means for calculating the phase ε1 by the following calculation formula (1) when the calculated vibration acceleration in the frequency domain exceeds a predetermined threshold;
Storage means for storing the phase ε0 calculated by the same calculation equation (1) as the phase ε1 when the previous vibration acceleration exceeds a predetermined threshold;
When the second calculation means calculates the phase ε1, the calculated phase ε1 is compared with the phase ε0 stored in the storage means. If the calculated phase ε1 is smaller than the previously calculated phase ε0, this time The calculated phase ε1 is updated and stored as the phase ε0, and the rotational speed of the rotating shaft is changed by a predetermined change amount. On the other hand, when the calculated phase ε1 is equal to or larger than the previously calculated phase ε0, Control means for instructing to change the rotation speed to the rotation speed at the time of phase ε0 calculation ;
A vibration suppression apparatus comprising: a rotation speed control means for controlling the rotation speed of the rotation shaft.
Arithmetic Formula (1): Phase ε1 = {60 × chatter frequency / (number of tool blades × rotational speed)} decimal part

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