JP6302794B2 - Rotation speed display method - Google Patents

Description

  The present invention relates to a rotation speed display method for displaying an optimum rotation speed capable of suppressing chatter vibration generated during machining in a machine tool.

  Conventionally, for example, there is a machine tool that supports a tool on a rotating shaft, moves the tool and / or the workpiece relative to each other while feeding the workpiece, and processes the workpiece with the rotating tool. In the machine tool, so-called chatter vibration is generated during machining due to an excessive increase in the amount of cutting during the cutting process, resulting in problems such as deterioration in finishing accuracy of the machined surface and rapid wear and chipping of the tool. As one of the techniques for suppressing the chatter vibration, the technique described in Non-Patent Document 1 is known, and as a vibration suppressing method using this technique, for example, it is described in Patent Document 1. In addition, the natural frequency of chatter vibration generating systems such as tools and workpieces is obtained by impulse excitation of the tools and workpieces, multiplied by 60 and divided by the number of tool blades and a predetermined integer. The chatter vibration is suppressed by rotating the rotation shaft at the stable rotation speed.

  Further, as another technique for suppressing chatter vibration, the technique described in Non-Patent Document 2 is publicly known. As a vibration suppressing method using this technique, for example, it is described in Patent Document 2. In addition, the vibration frequency is measured by attaching vibration detection means in the vicinity of the rotation axis of the machine tool, the stable rotation speed is obtained using the parameter calculated from the chatter frequency, and the rotation axis is rotated at the stable rotation speed. By suppressing the vibration, chatter vibration is suppressed.

JP 2003-340627 A JP 2008-290188 A

CIRP, Vol. 44/1 (1995) Analytical Prediction of Stability Loves in Milling 2001 Japan Society of Mechanical Engineers workshop materials "Basic knowledge of cutting and chatter vibration"

  Regarding the chatter vibration generated, for example, in machining using a tool T as shown in FIG. 8, chatter vibrations having different chatter frequencies are simultaneously generated at a relatively thin portion T1 and a relatively thick portion T2. Sometimes. When such chatter vibrations having different chatter frequencies occur (chatter vibrations occur in a plurality of chatter modes), the method described in Patent Documents 1 and 2 as described above can be used in any chatter mode. Even if it is chatter vibration, the optimum rotation speed that can be effectively suppressed cannot be obtained. Therefore, there is a problem that such an optimum rotation speed cannot be suitably displayed in order to prompt the operator to change the rotation speed.

  Therefore, the present invention has been made in view of the above-described problem, and is an optimum rotation speed that can effectively suppress the occurrence of chatter vibration even in a situation where chatter vibration occurs in a plurality of chatter modes. It is an object of the present invention to provide a rotation speed display method capable of suitably displaying.

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 display method for displaying an optimum rotation speed for suppressing vibrations, the first step of detecting chatter vibration by the vibration detection means, and when chatter vibration is detected, the chatter vibration causes the chatter to detect the chatter vibration. A second step of calculating a stable rotational speed for suppressing vibrations, and a set rotational speed set for each predetermined unit rotational speed in the storage means by the computing means, which is equal to or most equal to the stable rotational speed A specific set rotational speed that is close to the value is obtained, and a predetermined set rotational speed, a set rotational speed that is slower than the specific set rotational speed, and a set rotational speed that is faster than the specific set rotational speed are predetermined. According to the row, the evaluation value consisting of any one of the letters, symbols and numbers indicating the level of the chatter vibration suppression effect is given according to a predetermined pattern in which the evaluation value of the specific set rotational speed is the highest. A third step of weighting the set rotational speed, a fourth step of displaying the optimum rotational speed by displaying the result of the weighting of the set rotational speed on the display means by the computing means, and the optimum When a chatter vibration is newly detected after the rotation speed is changed to the rotation speed, a fifth step of calculating a new stable rotation speed for suppressing the new chatter vibration detected this time by the calculating means; The calculation means obtains a specific set rotational speed that is equal to or closest to the new stable rotational speed calculated this time among the set rotational speeds, A new set rotational speed is obtained by assigning the evaluation value to the specific set rotational speed, the set rotational speed slower than the specific set rotational speed, and the fast set rotational speed, respectively, according to the predetermined pattern. A new optimum rotational speed by displaying the result of the previous weighting of the set rotational speed and the result of the weighting of the current set rotational speed on the display means by the calculating means. And a seventh step of displaying.
The invention according to claim 2 is the invention according to claim 1, wherein, in the seventh step, as a result of the weighting of the previous set rotational speed, the evaluation value is equal to or higher than a predetermined rank, and the current time As a result of the weighting of the set rotation speed, a set rotation speed at which the evaluation value is equal to or higher than a predetermined rank is displayed as the new optimum rotation speed.

  According to the present invention, when chatter vibration is newly detected after the rotation speed is changed to the optimum rotation speed, a new stable rotation speed for suppressing the new chatter vibration detected this time is calculated and set. Among the rotational speeds, a set rotational speed that is equal to or closest to the new stable rotational speed calculated this time is obtained as a specific set rotational speed, and is slower than the specific set rotational speed and the specific set rotational speed. By assigning evaluation values to the set rotational speed and the fast set rotational speed according to a predetermined pattern, the set rotational speed is newly weighted. Then, the new optimum rotational speed is displayed by displaying the result of the weighting of the previous set rotational speed and the result of the weighting of the current set rotational speed on the display means. Therefore, even in a situation where chatter vibrations occur in a plurality of chatter modes, it is possible to suitably display the optimum rotation speed at which chatter vibrations can be effectively suppressed.

It is explanatory drawing which showed the block structure of the vibration suppression apparatus. It is explanatory drawing which showed the rotating shaft housing used as the object of vibration suppression from the side. It is explanatory drawing which showed the rotating shaft housing from the axial direction. It is a flowchart figure of vibration suppression control of chatter vibration including the display of the optimal rotational speed by a vibration suppression device. It is explanatory drawing which concerns on weighting of setting rotational speed. It is explanatory drawing which showed the specific example at the time of calculating | requiring an optimal rotational speed. It is explanatory drawing which showed the example of a display of the optimal rotational speed in a display apparatus. It is explanatory drawing which showed an example of the tool to be used.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a vibration suppression device that is an embodiment of the present invention and that executes a rotation speed display method for displaying an optimum rotation speed will be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing a block configuration of 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 has characteristics associated with vibration generated in the rotating rotating shaft 3. Vibration sensors 2a to 2c for detecting vibration acceleration in the time domain (meaning vibration acceleration on the time axis), and the presence or absence of chatter vibration by analyzing the detection values by the vibration sensors 2a to 2c And a control device 5 that controls the rotational speed of the rotary shaft 3 based on the determination result.

  The vibration sensors 2a to 2c are attached to the rotary shaft housing 1 as shown in FIGS. 2 and 3, and one vibration sensor detects vibration acceleration in the time domain in a direction perpendicular to the other vibration sensors. (For example, the vibration sensors 2a to 2c are attached so as to detect vibration acceleration in the time domain in the X-axis, Y-axis, and Z-axis directions orthogonal to each other).

  On the other hand, the control device 5 operates the FFT calculation device 11 that performs analysis based on the vibration acceleration in the time domain detected by the vibration sensors 2a to 2c, and the threshold value related to the detection of the machining conditions and the occurrence of chatter vibration. The presence or absence of chatter vibration from the input device 12 for input by the operator, the storage device 13 for storing data input by the operator via the input device 12, and the value analyzed by the FFT operation device 11 In addition to the detection, the calculation device 14 that calculates a stable rotation speed from the value and various values stored in the storage device 13 and weights the set rotation speed, and controls the machining in the rotary shaft housing 1. The NC device 16 is provided with a display device 15 such as a monitor for displaying a stable rotational speed in a manner as will be described later.

Here, the vibration suppression control of chatter vibration including the display of the optimum rotation speed by the vibration suppression device 10 will be described according to the flowchart of FIG.
First, before starting machining, a storage program or the like for performing weighting as described later is stored in advance in the storage device 13 via the input device 12, and the threshold value and tool type for detecting occurrence of chatter vibration are stored. Also, tool information such as the number of tool blades, machining conditions, and the like are stored in the storage device 13. Thereafter, when the machining is started by rotating the rotation shaft 3 at an arbitrary rotation speed (S1), Fourier analysis of vibration acceleration in the time domain in the vibration sensors 2a to 2c that are constantly detected during the rotation is performed, and the rotation shaft is used. Whether or not chatter vibration is occurring is constantly monitored (S2). Note that the chatter vibration detection method using the vibration sensors 2a to 2c is performed by the same known method as the method detailed in Japanese Patent Application Laid-Open No. 2010-17783 previously filed by the present applicant.

Then, when occurrence of chatter vibration is detected (YES in S2), a stable rotational speed is calculated by the following arithmetic expressions (1) to (3) (S3).
k ′ value = 60 × chat frequency / (number of tool blades × rotational speed) (1)
k value = integer part of k ′ value (2)
Stable rotation speed = 60 x chatter frequency / (number of tool blades x k value) (3)
The “number of tool blades” is the number of blades of the tool mounted on the rotating shaft. The “chatter frequency” is a frequency at which the vibration acceleration in the frequency domain takes a maximum value as a result of Fourier analysis of the vibration acceleration in the time domain.

  Further, the set rotational speed is weighted based on the calculated stable rotational speed (S4), and the result is displayed on the display device 15 (S5). Therefore, the worker changes the rotation speed of the rotating shaft 3 to an optimum rotation speed effective for suppressing chatter vibration based on the result displayed on the display device 15 (S6). The vibration suppressing device 10 continues to monitor the occurrence of chatter vibration until the machining is completed (YES in S7), and the occurrence of chatter vibration is detected again even though the rotation speed is changed to the optimum rotation speed. Then, a process of calculating a new stable rotational speed, weighting the set rotational speed based on the new stable rotational speed, and displaying the result on the display device 15 together with the previous weighting result is repeated.

Here, the weighting of the set rotation speed based on the stable rotation speed will be described.
If a stability limit diagram is created for processing using a predetermined tool, a curve in which repeated local maximum values appear as shown in FIG. 5 is obtained. Therefore, in this embodiment, to set the set rotation speed for each 20min ^-1 to 20min ^-1 as unit rotation speed. Then, a set rotational speed that is equal to or closest to the calculated stable rotational speed is obtained as a specific set rotational speed, and the rotational speed that is most effective in suppressing chatter vibration with respect to the specific set rotational speed is “5”. Is set in such a manner that evaluation values “1” to “4” are respectively given according to a predetermined pattern with respect to a set rotational speed slower than a specific set rotational speed and a fast set rotational speed. Rotation speed is weighted. That is, the evaluation value “4” is evaluated for the set rotational speed that is slower by one unit rotational speed than the specific set rotational speed to which the evaluation value of “5” is given. A value “3” is assigned to an evaluation value “2” for a setting rotational speed that is slow by 3 unit rotational speed, and an evaluation value “1” is assigned to a setting rotational speed that is slow by 4 unit rotational speed, respectively, while 1 unit rotational speed An evaluation value “2” is assigned to the fast set rotational speed, and an evaluation value “1” is assigned to the fast set rotational speed of 2 units. The set rotational speed weighted in this way is displayed on the display device 15 in a manner as shown in FIG. Moreover, you may take the view that the evaluation value "0" was provided about the setting rotational speed which does not provide an evaluation value.

A specific example of how the vibration suppression control as described above is actually performed will be described with reference to FIGS. 6 and 7.
First, it is assumed that processing is started at a rotational speed of 4160 min ⁻¹ and a cutting depth of 26 mm. Since the machining condition is in the unstable region in the stability limit diagram of chatter mode 1 as indicated by P1 in FIG. 6, chatter vibration in chatter mode 1 occurs during machining. Naturally, the chatter vibration is detected by the vibration suppression device 10, and the stable rotation speed is calculated. The stable rotation speed is assumed to be 3860 min ⁻¹ . Then, the calculation device 14 obtains a set rotation speed 3860min ⁻¹ that is a set rotation speed equal to the stable rotation speed as a specific set rotation speed, and an evaluation value “5” for the specific set rotation speed 3860min ⁻¹ . , And evaluation values “1” to “4” are assigned to the set rotational speed that is slower than the set rotational speed 3860 min ⁻¹ and the fast set rotational speed according to the above pattern, and the results are displayed on the display device 15. (FIG. 7A). Therefore, the worker assumes that the set rotational speed with the highest evaluation value (here, 3860 min ⁻¹ equal to the stable rotational speed) is the optimal rotational speed, changes the rotational speed to the optimal rotational speed, and continues the machining. It will be.

However, since the machining conditions after changing to P2 in FIG. 6 are in the stable region in the chatter mode 1 stability limit diagram, they are in the unstable region in the chatter mode 2 stability limit diagram. Chatter vibration in chatter mode 2 occurs during machining. Naturally, the chatter vibration is also detected by the vibration suppressing device 10 and the stable rotation speed is calculated again. This stable rotation speed is assumed to be 3740 min ⁻¹ . Then, similarly to the above, the calculation device 14 obtains a set rotation speed 3740 min ⁻¹ that is a set rotation speed equal to the stable rotation speed as a specific set rotation speed, and evaluates the specific set rotation speed 3740 min ⁻¹ . The value “5” is given, and the evaluation values “1” to “4” are given to the set rotational speed slower than the set rotational speed 3740 min ⁻¹ and the fast set rotational speed according to the above pattern, respectively. Is displayed on the display device 15 together with the previous result (FIG. 7B). Therefore, the operator finds the optimum rotation speed from the previous weighting result and the current weighting result (here, 3780 min ⁻¹ ), changes the rotation speed to the optimum rotation speed, and continues the machining. That is, when the vibration speed is changed to a specific set rotational speed 3740 min ⁻¹ calculated as a stable rotational speed as indicated by P3 in FIG. 6, chatter vibration in chatter mode 2 is suppressed, but chatter mode 1 again. Only chatter vibration occurs. Therefore, the set rotational speed that is effective for chatter vibration in both chatter mode 1 and chatter mode 2 as shown by P4 in FIG. 6 (that is, an evaluation value is assigned) is selected as the optimum rotational speed. By doing so, the occurrence of chatter vibration can be effectively suppressed in the subsequent processing. There may be a case where there is no set rotational speed that is effective for chatter vibration in both chatter mode 1 and chatter mode 2. In such a case, since there is no optimum rotation speed, a message such as “there is no optimum rotation speed” may be displayed. Further, there may be a case where there is no set rotational speed equal to the calculated stable rotational speed. In such a case, the set rotational speed that is closest to the stable rotational speed may be set as the specific set rotational speed.

  According to the vibration suppression device 10 as described above, when the calculation device 14 calculates a stable rotation speed for suppressing chatter vibration, the set rotation speed equal to or closest to the stable rotation speed is set to a specific set rotation speed. And an evaluation value of “5” is given to the specific set rotational speed as the rotational speed most effective in suppressing chatter vibration, and a set rotational speed that is slower than the specific set rotational speed and a fast set rotational speed. In accordance with the above pattern, the set rotation speeds are weighted in such a manner that the evaluation values “1” to “4” are assigned, and the result is displayed on the display device 15 to display the optimum rotation speed. In addition, if chatter vibration occurs again even if the optimal rotation speed is displayed and the rotation speed is changed, a new set rotation speed is weighted, and the previous weighting result and the current weighting result are combined. By displaying on the display device 15, a new optimum rotational speed capable of suppressing both chatter vibration generated last time and chatter vibration generated this time is displayed. Therefore, even in a situation where chatter vibrations occur in a plurality of chatter modes, it is possible to suitably display the optimum rotation speed at which chatter vibrations can be effectively suppressed.

  The rotational speed display method according to the present invention is not limited to the aspect of the above embodiment, and the weighting aspect, the aspect related to the display of the weighting result, and the like are within the scope of the present invention. These can be changed as necessary.

  For example, in the above embodiment, only the result of weighting the set rotational speed is displayed. However, as shown in FIG. 7C, the optimum rotational speed is judged from the weighted result, and the optimum rotational speed is directly suggested. Such a display may be performed. In other words, the evaluation value is “1” or more in the weighting result in the chatter mode 1 and the set rotation speed in which the evaluation value is “1” or more in the weighting result in the chatter mode 2 is directly set as the optimum rotation speed. Display. It should be noted that there is no problem even if the display is displayed together with the display of the result of the above weighting, and an appropriate design is made as to what value the evaluation value is to be the condition for the optimum rotational speed. It can be changed. Further, when there are a plurality of set rotational speeds that satisfy the above condition, the set rotational speed having the highest evaluation value may be displayed as the optimum rotational speed. Further, when chatter vibration is generated in chatter mode 1, only the optimum rotational speed is displayed, and weighting and display thereof are omitted, and weighting is also displayed when chatter vibration is generated in chatter mode 2.

Also, what value the unit rotational speed is set to can be changed as appropriate, and the pattern for assigning the evaluation value is not limited to the pattern of the above embodiment. Furthermore, as long as it represents the level of the suppression effect of chatter vibration according to a predetermined order, it is also possible to employ letters such as alphabets and symbols such as ○ ○ instead of numerical values.
Furthermore, in the above embodiment, the operator is configured to change the rotation speed, but when the optimum rotation speed is obtained, the NC device is configured to automatically change the rotation speed to the optimum rotation speed. It is also possible. In this case, instead of changing everything automatically, only the optimum rotational speed for chatter vibration in chatter mode 1 is automatically changed. For chatter vibration in chatter mode 2, the weighted result is used. It may be displayed to prompt the operator to change the rotation speed.

In the above embodiment, the vibration acceleration of the rotating shaft is detected by the vibration sensor. However, the displacement and sound pressure of the rotating shaft due to vibration are detected, and the stable rotational speed is determined based on the displacement and sound pressure. It is also possible to configure so as to calculate.
In addition, in the above-described embodiment, the vibration at the rotating shaft of the machine tool is detected. However, the vibration at the non-rotating side (fixed side) may be detected and the stable rotation speed may be calculated. The present invention is not limited to a machining center for rotating a tool, and can be suitably used for a machine tool such as a lathe for rotating a workpiece. Needless to say, the installation position, the number of installations, and the like of the detection means may be appropriately changed according to the type and size of the machine tool.

  Rotating shaft housing, 2a, 2b, 2c, vibration sensor (vibration detecting means), 3, rotating shaft, 5 ... control device, 10 ... vibration suppression device, 11 ... FFT calculation device, 12 ...・ Input device, 13... Storage device (storage means), 14 ..Calculation device (calculation means), 15 ..Display device (display means), 16.

Claims (2)

In a machine tool having a rotating shaft for rotating a tool or a workpiece, a rotational speed display method for displaying an optimum rotational speed for suppressing chatter vibration generated when the rotating shaft is rotated,
A first step of detecting chatter vibration by the vibration detection means;
When chatter vibration is detected, a second step of calculating a stable rotational speed for suppressing the chatter vibration by a calculation means;
Among the set rotational speeds set for each predetermined unit rotational speed in the storage means by the calculating means, a specific set rotational speed that is equal to or closest to the stable rotational speed is obtained, and the specific set rotational speed is obtained. From any one of letters, symbols, and numbers indicating the level of the chatter vibration suppression effect according to a predetermined order with respect to the speed, a set rotational speed that is slower than the specific set rotational speed, and a fast set rotational speed. A third step of weighting the set rotational speed by assigning each evaluation value according to a predetermined pattern such that the evaluation value of the specific set rotational speed is the highest,
A fourth step of displaying the optimum rotational speed by displaying the result of weighting of the set rotational speed on the display means by the computing means;
When chatter vibration is newly detected after the rotation speed is changed to the optimum rotation speed, the calculation means calculates a new stable rotation speed for suppressing the new chatter vibration detected this time. Process,
The calculation means obtains a specific set rotation speed that is equal to or closest to the new stable rotation speed calculated this time among the set rotation speeds, and the specific set rotation speed and the specific set rotation speed. A sixth step of newly weighting the set rotational speed by assigning the evaluation value to the set rotational speed that is slower than the speed and the fast set rotational speed, respectively, according to the predetermined pattern;
A seventh step of displaying a new optimum rotational speed by displaying the result of the weighting of the previously set rotational speed and the result of the weighting of the currently set rotational speed on the display means by the calculating means. A rotational speed display method characterized by:   In the seventh step, as a result of the weighting of the previous set rotational speed, the evaluation value is equal to or higher than a predetermined rank, and as a result of the weighting of the current setting rotational speed, the evaluation value is equal to or higher than a predetermined rank. The rotation speed display method according to claim 1, wherein a set rotation speed is displayed as the new optimum rotation speed.

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