JP5385067B2 - Rotational speed calculation device - Google Patents

Description

  The present invention relates to a rotation speed calculation device that calculates and displays a stable rotation speed capable of suppressing vibration when vibration occurs during machining in a machine tool that performs machining while rotating a tool or a workpiece.

Conventionally, the following methods are known as methods for suppressing chatter vibration that causes deterioration of finishing accuracy of a machined surface. First, the natural frequency of a system in which chatter vibration occurs such as a tool or a workpiece, or the chatter frequency during processing of the system in which chatter vibration occurs is obtained. Next, a value obtained by multiplying the natural frequency or chatter frequency by 60 and dividing by the number of tool blades and a predetermined integer is calculated as a stable rotation speed. Then, by performing processing at the stable rotational speed, chatter vibration generated during the processing is suppressed.
In addition, in the vibration suppressing device that executes the above-described conventional method, a device that includes a display unit for informing the operator of the occurrence of chatter vibration and the calculated stable rotation speed has been devised (for example, Patent Document 1).

JP-T-2001-517557

According to the above method, since the calculation such as dividing by a predetermined integer is performed when calculating the stable rotational speed, the stable rotational speed is 1/2, 1/3, 1/4 with respect to the theoretical maximum value. Can be obtained discretely. However, as the fraction becomes smaller (that is, the predetermined integer is increased), the calculated stable rotational speed interval becomes gradually smaller. Therefore, there is no difference in chatter state between the stable rotational speed and the rotational speed that is not so, and chatter vibration cannot be suppressed at such a stable rotational speed.
However, according to the vibration suppressing device described in the above-mentioned Patent Document 1, a stable rotation speed that is small in fraction and cannot be expected to suppress chatter vibration is displayed and notified to the operator. is there.

  Therefore, the present invention has been made in view of the above problem, and determines whether or not to display the calculated stable rotation speed, and does not notify the operator of the stable rotation speed at which chatter vibration cannot be suppressed. An object of the present invention is to provide a rotation speed calculation device.

In order to achieve the above object, the invention according to claim 1 of the present invention is a chatter vibration generated when a rotating shaft for rotating a tool or a workpiece is rotated in the machine tool. A rotation speed calculation device comprising: a detection means for detecting the movement; a calculation means for calculating a stable rotation speed for suppressing the chatter vibration; and a display means for displaying the stable rotation speed calculated by the calculation means. Then, the calculation means calculates the stable rotation speed in order while increasing the k value by 1 using the following calculation formula (1), and the k value used for the calculation of the stable rotation speed and a predetermined integer value: a is, compared with a predetermined set value which is set based on the difference between the calculated stable rotation speed stabilizing rotational speed calculated using the values as k value and a value less than the value as k value And before While Viewing to the display means for stabilizing the rotational speed calculated using the k value below a predetermined set value, the stable rotational speed calculated using the k value exceeding the predetermined set value to the display means A display determining means for not displaying is provided.
Formula (1): Stable rotational speed = {60 × chat frequency / (number of tool blades × (k value + 1))}
The k value is an arbitrary integer.
Moreover, in order to achieve the said objective, invention of Claim 2 among this invention arises when the said rotating shaft is rotated in the machine tool provided with the rotating shaft for rotating a tool or a workpiece | work. A rotation speed calculation device comprising: detection means for detecting chatter vibration; calculation means for calculating a stable rotation speed for suppressing chatter vibration; and display means for displaying the stable rotation speed calculated by the calculation means. In the calculation means, the following calculation formula (1) is used to calculate the stable rotation speed in order while increasing the k value by one, and the calculation means is calculated using the stable rotation speed calculated this time and the previous k value. to determine the difference between the stable rotational speed, comparing the said difference with a predetermined set value, while a stable rotational speed calculated this time table Shimesuru to the display means when the difference exceeds the predetermined set value The above Wherein the display determining means is provided which does not show a stable rotational speed calculated this time to the display means if below the constant settings.
Formula (1): Stable rotational speed = {60 × chat frequency / (number of tool blades × (k value + 1))}
The k value is an arbitrary integer.

According to the present invention, the difference between the k value used for calculating the stable rotation speed or the stable rotation speed calculated this time and the stable rotation speed calculated using the immediately preceding k value is compared with a predetermined set value. In comparison, there is provided display determination means for displaying the stable rotational speed on the display means only when the k value is lower than the predetermined set value or when the difference in the stable rotational speed is higher than the predetermined set value . For this reason, a stable rotational speed in which the k value is larger than a predetermined set value or a rotational speed at which there is almost no difference between the stable rotational speeds, that is, a stable rotational speed at which chatter vibration cannot be effectively suppressed is not displayed. Therefore, only the stable rotational speed that is relatively effective for suppressing chatter vibration is displayed on the display means, which is convenient for the operator.

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 a flowchart figure which concerns on suppression control of chatter vibration.

  Hereinafter, a rotational speed calculation device built in a vibration suppressing device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  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. The vibration sensors 2a to 2c for detecting the vibration acceleration of the region (meaning vibration acceleration on the time axis), and the control for controlling the rotation speed of the rotary shaft 3 based on the detection values by the vibration sensors 2a to 2c. Device 5.

  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. A calculation device 12 for calculating the rotation speed, an NC device 13 for controlling machining in the rotary shaft housing 1, an operation unit 14 for instructing the NC device 13 about a rotation speed, and the stable rotation calculated by the calculation device 12. And a display device 15 for displaying the speed.

Here, the vibration suppressing method of “chatter vibration” by the vibration suppressing apparatus 10 as described above will be described 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 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. Use the waveform that maximizes.

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). A stable rotation speed is calculated (S4).
Stable rotational speed = {60 × chat frequency / (number of tool blades × (k value + 1))} (1)
The “number of tool blades” is the number of blades of the tool mounted on the rotary shaft 3 and is input and set in advance in the arithmetic unit 12. The k value is an integer greater than or equal to 0, specifically 0, 1, 2, 3,..., And initially, the stable rotational speed is calculated with k = 0.

  When the stable rotation speed is calculated in S4, it is determined whether or not the k value used for the calculation is smaller than a predetermined set value (for example, 20) (S5). When the k value is 20 or less (YES in S5), the stable rotation speed calculated in S4 is displayed on the display device 15 (S6), and 1 is added to the current k value to obtain a new k value. (S7), and using this new k value, the stable rotational speed is calculated by the above equation (1). The display of the stable rotational speed (S6) and the update of the k value (S7) are repeated until the k value exceeds 20, and the display device 15 displays the stable rotational speed when k = 0, and the case where k = 1. Are displayed in this order. Stable rotational speed of k = 2, stable rotational speed when k = 2.

  Further, when the k value exceeds 20 (NO in S5), the calculation of the stable rotation speed is stopped without displaying the stable rotation speed at the k value. Then, when one of the stable rotational speeds displayed on the display device 15 is selected by the operator (S8), the NC device 13 selects the rotational speed of the rotary shaft 3. By changing to a stable rotational speed, “chatter vibration” is suppressed.

  According to the vibration suppression device 10 as described above, when the calculated stable rotation speed is displayed on the display device 15, the k value used to calculate the stable rotation speed is confirmed. The stable rotation speed at which the k value exceeds a predetermined set value, that is, the difference between the stable rotation speeds is almost eliminated, and the stable rotation speed at which chatter vibration cannot be effectively suppressed is displayed on the display device 15. do not do. Therefore, only the stable rotation speed that is relatively effective for suppressing chatter vibration is displayed on the display device 15, which is convenient for the operator.

  Note that the configuration related to the rotational speed calculation device of the present invention is not limited to the aspect of the above-described embodiment, and includes the configuration related to chatter frequency detection and vibration suppression control, as well as the display of stable rotational speed. The configuration related to the non-display control can be appropriately changed as necessary without departing from the spirit of the present invention.

For example, in the above embodiment, display / non-display of the stable rotational speed is determined based on the k value, but instead of using the k value, the difference between the calculated stable rotational speed and the previously calculated stable rotational speed. If the difference is less than a predetermined set value (for example, 30 min ⁻¹ ), the same effect can be obtained even if the stable rotational speed is not displayed.
Further, it is needless to say that the set value to be compared with the k value for determining display / non-display of the stable rotation speed or the difference between the rotation speeds is not limited to the above numerical value, and the set value to be compared with the k value is larger than 20. A numerical value or a small numerical value may be sufficient, and the setting value compared with the difference in rotational speed may be a numerical value larger or smaller than 30 min ⁻¹ .

Further, in the above embodiment, vibration suppression control is performed using a waveform having the maximum vibration acceleration in the frequency domain among waveforms acquired by Fourier analysis of vibration acceleration in the time domain. Even if the stable rotational speed is calculated by using a plurality of (for example, three) waveforms having higher vibration acceleration values in the region, the effect of suppressing “chatter vibration” by the stable rotational speed can be further improved. Good.
Furthermore, 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 can 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 to obtain a stable rotational speed. You may do it.
In addition, the rotational speed calculation device may be provided separately from the vibration suppression device (that is, separate from the NC device or the like), and is not limited to a machining center that rotates a tool to process, such as a lathe that rotates a workpiece. It can also be used to suppress vibrations of machine tools. Furthermore, it goes without saying that the installation position and number of detection means can be appropriately changed according to the type and size of the machine tool.

  1 .... Rotating shaft housing 2 .... Vibration sensor (detection means) 3 .... Rotating shaft 5 .... Control device 10 .... Vibration suppression device 11 .... FFT arithmetic unit 12, ... Means, display determination means), 13... NC device, 14... Operation unit, 15 .. display device (display means).

Claims (2)

In a machine tool having a rotating shaft for rotating a tool or a workpiece, a detecting means for detecting chatter vibration generated when the rotating shaft is rotated, and a stable rotational speed for suppressing the chatter vibration are calculated. A rotational speed computing device comprising computing means and display means for displaying the stable rotational speed calculated by the computing means,
The calculation means uses the following calculation formula (1) to calculate the stable rotation speed in order while increasing the k value by one,
The k value used for the calculation of the stable rotation speed and a predetermined integer value, the stable rotation speed calculated using the value as the k value, and the stable rotation calculated as a value less than that value by 1 comparing the predetermined set value which is set based on the difference between the speed, while the predetermined stabilizing rotational speed set value is calculated using the k values below are for Viewing to said display means, of the predetermined A rotation speed calculation device, comprising: a display determination unit that does not display a stable rotation speed calculated using a k value exceeding a set value on the display unit .
Formula (1): Stable rotational speed = {60 × chat frequency / (number of tool blades × (k value + 1))}
The k value is an arbitrary integer. In a machine tool having a rotating shaft for rotating a tool or a workpiece, a detecting means for detecting chatter vibration generated when the rotating shaft is rotated, and a stable rotational speed for suppressing the chatter vibration are calculated. A rotational speed computing device comprising computing means and display means for displaying the stable rotational speed calculated by the computing means,
The calculation means uses the following calculation formula (1) to calculate the stable rotation speed in order while increasing the k value by one,
It obtains the difference between the calculated stable rotational speed by using the k value immediately before and the currently calculated stable rotation speed, comparing the said difference with a predetermined setting value, if the difference exceeds the predetermined set value on the other hand a stable rotational speed calculated this time table Shimesuru to said display means, characterized in that the predetermined display determining means not to display a stable rotational speed calculated this time to the display means when below the set value is provided Rotational speed calculation device.
Formula (1): Stable rotational speed = {60 × chat frequency / (number of tool blades × (k value + 1))}
The k value is an arbitrary integer.

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