System for estimating vibration characteristics in machine tool, machine tool, and method for estimating vibration characteristics

Abstract

The invention provides a vibration characteristic estimation system in a machine tool, a machine tool, and a vibration characteristic estimation method, which can correct the vibration characteristic at a sensor mounting position of the machine tool and estimate the vibration characteristic at a target point where a sensor is difficult to mount with high precision. A vibration characteristic estimation system (21) acquires a first vibration characteristic in a first vibration characteristic acquisition unit (22) on the basis of the output of an acceleration sensor (9). Next, machine information is acquired by a machine information acquisition unit (23), and gripping tool information is acquired by a gripping tool information acquisition unit (24). In addition, tool information or workpiece information is acquired in a machining unit information acquisition unit (25). Next, a correction coefficient acquisition unit (27) acquires a correction coefficient on the basis of the machine information, the gripping tool information, the tool information, or the workpiece information. Then, a second vibration characteristic estimation unit (28) estimates a second vibration characteristic by correcting the first vibration characteristic using the correction coefficient.

Description

Technical Field

[0001] The present disclosure relates to a vibration characteristic estimating system for estimating vibration characteristics in a machine tool, a machine tool, and a vibration characteristic estimating method. Background Art

[0002] In order to perform efficient and high-precision cutting processing by a machine tool, it is necessary to consider the vibration characteristics of the system including the machine tool, the tool and the workpiece to select appropriate cutting conditions. For example, the applicant disclosed the following vibration characteristic estimation method in patent document 1: by using the vibration measurement results in actual processing, even if the operator does not have specialized skills and knowledge related to vibration, the vibration characteristics of the system can be estimated. The vibration characteristic estimation method disclosed in patent document 1 calculates the vibration characteristics based on the measurement results of the vibration in the processing of the object point where the vibration characteristics are to be estimated. As the object point where the vibration characteristics are to be estimated, for example, the front end of the tool can be cited. In addition, as a vibration measurement method, for example, a method of installing an accelerometer as a sensor at the object point can be cited. However, in actual sites, the tools used in most cases are different for each operator. That is to say, the installation position and installation state of the accelerometer used to estimate the vibration characteristics to the tool need to be judged by the operator. Therefore, in fact, when you want to use the method disclosed in patent document 1, in order to make an appropriate judgment of the quality, sometimes the operator is required to master the specialized skills and knowledge related to vibration.

[0003] Therefore, as another vibration characteristic estimation method that can estimate the vibration characteristics of the system even when the operator does not have specialized skills and knowledge related to vibration, the following method is considered: an accelerometer is pre-installed at a predetermined position of a machine tool where a sensor is easy to install, the vibration characteristics of the machine tool are estimated using the method of Patent Document 1, and the estimated vibration characteristics are corrected. Thus, even when the operator does not have specialized skills and knowledge related to vibration, the vibration characteristics of a desired estimation target point such as the tip of a tool, which can be arbitrarily changed by the operator and therefore difficult to install a sensor, can be estimated. As a technology for estimating the vibration characteristics of a desired estimation target point by correcting a predetermined value, Patent Document 2 discloses the following method: an analytical value (calculated value) of the natural vibration frequency of a spindle system that can be said to be a vibration characteristic of a used tool is corrected, thereby estimating the actual natural vibration frequency. In the correction of the analytical value, the difference between the analytical value and the measured value of the natural vibration frequency of the spindle system with a reference tool installed is used as a correction value. On the other hand, in a complex system such as a machine tool, there are multiple natural vibration frequencies. Therefore, the analysis values ​​and the measured values ​​of each of the plurality of natural frequencies are associated with each other in descending order of frequency, and correction values ​​corresponding to each of the plurality of natural frequencies are calculated based on the associated analysis values ​​and measured values.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-80015

[0005] Patent Document 2: Japanese Patent Application Publication No. 2012-187691

[0006] However, in the method disclosed in Patent Document 2, for example, when the tool in use is very different from the reference tool, the order of correspondence between the natural vibration frequency and the vibration behavior is different between the reference tool and the tool in use. Therefore, there is a possibility that the natural vibration frequency cannot be properly estimated even by using the correction value calculated by using the reference tool for the system equipped with the tool in use.

[0007] Therefore, a vibration characteristic estimation method is desired that can estimate the vibration characteristics of an estimation target, where it is difficult to mount a sensor, with high accuracy by correcting the vibration characteristics estimated at a predetermined portion of a machine tool where a sensor is easily mounted. Summary of the invention

[0008] Therefore, the present disclosure is completed in view of the above-mentioned problems, and its purpose is to provide a vibration characteristic estimation system, a machine tool and a vibration characteristic estimation method in a machine tool, which can correct the vibration characteristics at the sensor installation position of the machine tool and estimate the vibration characteristics of the object point where it is difficult to install the sensor with high precision.

[0009] In order to achieve the above-mentioned purpose, the first structure of the present disclosure is a vibration characteristic estimation system in a machine tool, characterized in that, in a machine tool that performs processing by relatively moving a tool and a workpiece, the system comprises: a first vibration characteristic acquisition unit that acquires a first vibration characteristic based on an output of a sensor installed on the machine tool when an excitation force is applied to a processing point, the processing point being a contact point between the tool and the workpiece being processed; a mechanical information acquisition unit that acquires mechanical information, the mechanical information including at least one of the name of the machine tool, an axis structure, component information, and installation position information of the sensor; a gripping tool information acquisition unit that acquires gripping tool information including at least one of the name, size, material, and gripping method of a gripping tool for gripping a tool or a workpiece; a processing unit information acquisition unit that acquires at least one of tool information and workpiece information, the tool information including tool information, The invention relates to a method of manufacturing a machine tool according to the present invention; a method of manufacturing a machine tool according to the present invention; a method of manufacturing a machine tool according to the present invention; and a method of estimating a second vibration characteristic of the machine tool. The method comprises: obtaining a correction coefficient based on at least one of the mechanical information, the holding device information, the tool information and the workpiece information, wherein the correction coefficient is associated with at least one of the mechanical information, the holding device information, the tool information and the workpiece information, and storing the correction coefficient representing the ratio of the first vibration characteristic to the second vibration characteristic. The second vibration characteristic is based on the vibration amount of the processing point when an exciting force is applied to the processing point. The correction coefficient acquisition unit obtains a correction coefficient based on at least one of the mechanical information, the holding device information, the tool information and the workpiece information from the correction coefficient storage unit. The method also comprises: a method of estimating a second vibration characteristic of the machine tool according to the present invention; and a method of estimating a second vibration characteristic of the machine tool according to the present invention.

[0010] Another aspect of the first structure of the present disclosure is characterized in that, in the above structure, the correction coefficient includes at least a constant associated with the tool information.

[0011] Still another aspect of the first structure of the present disclosure is characterized in that, in the above-mentioned structure, the correction coefficient is a frequency function associated with at least the mechanical information.

[0012] In order to achieve the above-mentioned object, a second structure of the present disclosure is a machine tool characterized by having the above-mentioned structure.

[0013] In order to achieve the above-mentioned purpose, the third structure of the present disclosure is a vibration characteristic estimation method, characterized in that, in a machine tool that performs processing by relatively moving a tool and a workpiece, the method includes the following steps: a first vibration characteristic acquisition step, acquiring a first vibration characteristic based on the output of a sensor installed on the machine tool when an excitation force is applied to a processing point, the processing point being the contact point between the tool and the workpiece being processed; a mechanical information acquisition step, acquiring mechanical information, the mechanical information including at least one of the name of the machine tool, the axis structure, the component information and the installation position information of the sensor; a holding tool information acquisition step, acquiring holding tool information, the holding tool information including at least one of the name, size, material and the holding method of the tool or the workpiece for holding the tool or the workpiece; a processing part information acquisition step, acquiring a first vibration characteristic based on the output of a sensor installed on the machine tool when an excitation force is applied to a processing point; the ... A step of obtaining at least one of tool information and workpiece information, wherein the tool information includes at least one of the name, size and material of the tool, and the workpiece information includes at least one of the name, size and material of the workpiece; a correction coefficient acquisition step of obtaining a correction coefficient representing the ratio of a first vibration characteristic to a second vibration characteristic based on at least one of the mechanical information, the holding device information, the tool information and the workpiece information, wherein the second vibration characteristic represents the vibration amount of the processing point when an excitation force is applied to the processing point; and a second vibration characteristic estimating step of correcting the first vibration characteristic obtained by the first vibration characteristic acquisition step using the correction coefficient obtained by the correction coefficient acquisition step to estimate the second vibration characteristic, wherein the correction coefficient is based on the mechanical information and a frequency associated with the mechanical information, and the frequency is obtained from a sensor.

[0014] According to the present disclosure, in a machine tool, by correcting the vibration characteristics of a point where a sensor can be easily installed based on at least one of mechanical information, holding tool information, tool information or workpiece information, the vibration characteristics of a desired point where a sensor is difficult to install can be estimated with high accuracy.

[0015] Furthermore, even when the correction coefficient related to the target point for estimating the vibration characteristics has not been acquired, the vibration characteristics of the target point can be estimated using the acquired correction coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a diagram schematically showing the configuration of a vibration characteristic estimation system in a machine tool.

[0017] Figure 2 : is a flowchart showing the estimation method of the second vibration characteristic.

[0018] Figure 3 : is a figure which shows the measurement example of the 1st vibration characteristic and the 2nd vibration characteristic.

[0019] Figure 4 It is a diagram showing an example of the correction coefficient.

[0020] Figure 5 This is a comparison between the direct measurement result and the estimated result of the second vibration characteristic.

[0021] Figure 6 This is a comparison between the direct measurement result and the estimated result of the second vibration characteristic.

[0022] Description of symbols

[0023] 1: bed; 2: column; 3: spindle housing; 4: spindle; 5: bracket; 6: tool; 7: worktable; 8: workpiece; 9: acceleration sensor; 11: NC device; 12: vibration analysis unit; 13: mechanical information storage unit; 14: holding tool information storage unit; 15: tool information storage unit; 21: vibration characteristic estimation system; 22: first vibration characteristic acquisition unit; 23: mechanical information acquisition unit; 24: holding tool information acquisition unit; 25: processing unit information acquisition unit; 26: correction coefficient storage unit; 27: correction coefficient acquisition unit; 28: second vibration characteristic estimation unit. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the structure of a machining center as an example of a machine tool.

[0026] A spindle 4 that can rotate with the aid of a spindle motor is provided on the spindle housing 3 of the machining center m. A tool 6 held by a bracket 5 is installed at the front end of the spindle 4. The spindle housing 3 as a movable body can move in the Z-axis direction relative to a column 2 installed on the bed 1 with the aid of a Z-axis ball screw. An acceleration sensor 9 that serves as a sensor for detecting vibrations of the machining center m is installed on the spindle housing 3. In addition, a workpiece 8 is fixed on a workbench 7 as a movable body. The workbench 7 can move on the bed 1 in X-axis directions and Y-axis directions that are perpendicular to each other. The movement of the workbench 7 in the X-axis direction is performed by the X-axis ball screw through the X-axis motor, and the movement in the Y-axis direction is performed by the Y-axis ball screw through the Y-axis motor.

[0027] The NC device 11 that controls the machining center m has a mechanical motion command unit (not shown) that controls the spindle motor and each feed axis motor according to a program input by an operator, and commands the rotation of the tool 6 and the relative movement of the tool 6 and the workpiece 8 to perform cutting. The NC device 11 includes a CPU and a memory connected to the CPU, and the operation is realized by using these.

[0028] The vibration characteristic estimation system 21 includes a first vibration characteristic acquisition unit 22, a mechanical information acquisition unit 23, a gripping tool information acquisition unit 24, and a processing unit information acquisition unit 25. The vibration characteristic estimation system 21 is configured as a computer included in the NC device 11 or as a separate computer, and is electrically connected to the machining center m. The first vibration characteristic acquisition unit 22 calculates and acquires the ratio (compliance) of the vibration amount of the spindle housing 3 to the exciting force applied to the front end of the tool 6 for machining at the machining point, which is the contact point between the tool 6 and the workpiece 8 during machining. The ratio of the vibration amount of the spindle housing 3 to the exciting force applied to the front end of the tool 6 for machining is the first vibration characteristic in this embodiment. In the calculation of the first vibration characteristic, the exciting force applied to the front end of the tool 6 is the output (detection value) of the hammer when the front end of the tool 6 is excited by a hammer with a built-in load sensor, and the vibration amount of the spindle housing 3 is the output (detection value) of the acceleration sensor 9. Alternatively, as disclosed in Patent Document 1, the first vibration characteristic may be calculated by analyzing the vibration during machining detected by the acceleration sensor 9 .

[0029] The mechanical information acquisition unit 23 acquires mechanical information from the mechanical information storage unit 13 for storing mechanical information of the NC device 11. In the present disclosure, mechanical information refers to various information for determining the transmission method of vibration from the spindle 4 of the machining center m to the acceleration sensor 9, and includes, in addition to the machine name, the shaft structure related to the machining center m, component information, component combination method, installation position of the acceleration sensor 9, and the like.

[0030] The gripping tool information acquisition unit 24 acquires the gripping tool information from the gripping tool information storage unit 14 that stores the gripping tool information of the NC device 11. In the present disclosure, the gripping tool information refers to various information including the gripping method of the holder 5 for the tool 6 and the material of the holder 5, and includes, in addition to the name of the holder 5, the size of the holder 5 such as the diameter DH and the length LH, the position, the gripping force, the gripping direction, and the like.

[0031] The processing part information acquisition unit 25 acquires the tool information from the tool information storage unit 15 for storing the tool information of the NC device 11. In the present disclosure, the tool information refers to various information including the size of the tool 6, the protruding length LT relative to the support 5, and the material of the tool 6, and includes, in addition to the name of the tool 6, the diameter DT, the total length, the blade length, the number of blades, and the like.

[0032] The vibration characteristic estimation system 21 further includes a correction coefficient storage unit 26, a correction coefficient acquisition unit 27, and a second vibration characteristic estimation unit 28. The correction coefficient storage unit 26 stores the correction coefficient C indicating the ratio of the first vibration characteristic to the second vibration characteristic in association with the machine information, the gripping tool information, and the tool information. The ratio (compliance) of the vibration amount of the tip of the tool 6 to the excitation force applied to the tip of the tool 6 for processing is the second vibration characteristic in this embodiment.

[0033] The correction coefficient acquisition unit 27 acquires the correction coefficient C from the correction coefficient storage unit 26. The second vibration characteristic estimation unit 28 corrects the first vibration characteristic using the correction coefficient C, thereby estimating the second vibration characteristic.

[0034] Hereinafter, a method for estimating the second vibration characteristic of the vibration characteristic estimating system of the present disclosure will be described.

[0035] Figure 2 : is a flowchart showing the estimation method of the second vibration characteristic.

[0036] First, as a first vibration characteristic acquisition step S1, the first vibration characteristic acquisition unit 22 acquires the first vibration characteristic. With regard to the acquisition of the first vibration characteristic, a known method that can calculate the ratio of the vibration amount of the spindle housing 3 to the exciting force applied to the front end of the tool 6 being processed can be arbitrarily set. In this embodiment, referring to the method shown in Patent Document 1, it is assumed that the vibration analysis unit 12 of the NC device 11 analyzes the output information of the acceleration sensor 9 during processing to acquire the first vibration characteristic.

[0037] Next, as a mechanical information acquisition step S2 , the mechanical information acquisition unit 23 acquires mechanical information from the mechanical information storage unit 13 .

[0038] Next, as a grasping instrument information acquisition step S3 , the grasping instrument information acquisition unit 24 acquires the grasping instrument information from the grasping instrument information storage unit 14 .

[0039] Next, as a processing part information acquisition step S4 , the processing part information acquisition unit 25 acquires tool information from the tool information storage unit 15 .

[0040] As the correction coefficient acquisition step S5 , the correction coefficient acquisition unit 27 acquires the correction coefficient C from the correction coefficient storage unit 26 based on the machine information, the gripping tool information, and the tool information acquired in the machine information acquisition step S2 , the gripping tool information acquisition step S3 , and the processing unit information acquisition step S4 .

[0041] Thereafter, as a second vibration characteristic estimating step S6, the second vibration characteristic estimating unit 28 corrects the first vibration characteristic acquired by the first vibration characteristic acquiring unit 22 using the correction coefficient C acquired by the correction coefficient acquiring unit 27, thereby estimating the second vibration characteristic of the object point for which the vibration characteristic is to be estimated.

[0042] Here, the correction coefficient C used in the vibration characteristic estimation system of the present disclosure will be described in detail based on examples.

[0043] Figure 3 : is a figure which shows the measurement example of the 1st vibration characteristic and the 2nd vibration characteristic. Figure 4 It is a diagram showing an example of the correction coefficient.

[0044] As an example, in Figure 3 , the first vibration characteristic and the second vibration characteristic obtained by a hammer test in a state where a superhard end mill (tool 6) with DT=20mm is mounted on a bracket 5 with LT=60mm. The hammer test is performed on a machining center m in a state where an acceleration sensor (not shown) is mounted on the front end of the superhard end mill using a hammer with a built-in load sensor. In the hammer test, the front end of the superhard end mill is excited with a hammer, and the output of the load sensor built into the hammer, the output of the acceleration sensor 9 mounted on the spindle housing 3, and the output of the acceleration sensor mounted on the front end of the superhard end mill are obtained. Based on the obtained outputs, the ratio of the output of the acceleration sensor 9 to the output of the hammer is calculated as the first vibration characteristic, and the ratio of the output of the acceleration sensor mounted on the front end of the superhard end mill to the output of the hammer is calculated as the second vibration characteristic. In addition, when estimating the second vibration characteristic based on the first vibration characteristic, in order to enable the operation even when the operator does not have specialized skills and knowledge related to vibration, it is preferred that the vibration characteristic estimation system 21 analyzes the vibration during processing to obtain the first vibration characteristic. However, the first vibration characteristic for calculating the correction coefficient C may be obtained by an expert performing a hammer test at an opportunity different from the estimation of the second vibration characteristic, such as before the machining center m is shipped.

[0045] When the first vibration characteristic and the second vibration characteristic obtained by the hammer test are compared, it can be seen that the second vibration characteristic is very large. This is because the first vibration characteristic and the second vibration characteristic both represent the ease of vibration, and the front end of the superhard end mill is more likely to vibrate than the spindle housing 3.

[0046] In addition, when the ratio of the first vibration characteristic to the second vibration characteristic, that is, the correction coefficient C, is calculated and plotted, as shown in FIG. Figure 4As shown, it can be seen that the correction coefficient C changes according to the frequency f. The reason why the correction coefficient C changes is that since it is a complex system in which the bracket 5 and the spindle 4 are sandwiched between the tip of the tool 6 as the estimated target point of the vibration characteristics and the acceleration sensor 9, the vibration mode, that is, the vibration state changes according to the frequency f, and the transmission method of the vibration from the tool 6 to the spindle housing 3 is different. In other words, if the frequency f and the mechanical structure of the machining center m, the bracket 5 and the tool 6 are the same, it can be said that the transmission method of the vibration from the tool 6 to the spindle housing 3 is the same.

[0047] That is, if the frequency f is clear, the second vibration characteristic can be estimated from the first vibration characteristic by using the correction coefficient C. Here, in the present embodiment, the frequency f of the vibration in the spindle housing 3 can be measured by the acceleration sensor 9. Therefore, if the first vibration characteristic of the system including the spindle housing 3 and the correction coefficient C related to the estimation target point can be obtained, the second vibration characteristic of the estimation target point can be estimated from the first vibration characteristic.

[0048] On the other hand, as described above, the first vibration characteristic is acquired by the first vibration characteristic acquisition unit 22. Furthermore, the vibration characteristic estimation system 21 stores the correction coefficient C in the correction coefficient storage unit 26 in association with the machine information, the gripping tool information, and the tool information.

[0049] However, when estimating the second vibration characteristic from the first vibration characteristic using the correction coefficient C, as described above, the mechanical structure of the machining center m, the support 5, and the tool 6 need to be the same. That is, in order to estimate the second vibration characteristic from the first vibration characteristic using the correction coefficient C, it is necessary to store a huge correction coefficient C in the correction coefficient storage unit 26 after obtaining the correction coefficient C for each of the desired machine information, the gripping tool information, and the tool information.

[0050] In contrast, the applicant has found that, as shown in Mathematical Formula 1, the correction coefficient C is represented by the product of the correction coefficient T and the correction coefficient M. In the present embodiment, the correction coefficient M is the correction coefficient C when the reference tool, i.e., the tool 6, which is the reference of the correction, is mounted on the bracket 5, and is obtained according to each combination of the mechanical structure of the machining center m and the bracket 5. In addition, the correction coefficient T is the ratio of the correction coefficient C of the reference tool to the correction coefficient C of the target tool, i.e., the tool 6, which is the estimation object.

[0051] C(f)=T×M(f) (1)

[0052] The correction coefficient T is a value that depends on the shape of the tool 6, and is therefore associated with the tool information as a constant that is independent of the frequency. For example, under the condition that LT is 60 mm, 70 mm, or 80 mm, for a tool 6 with a DT of 12 mm, 16 mm, or 20 mm mounted on the bracket 5 of the machining center m, the correction coefficient T calculated based on the correction coefficient C obtained from the direct measurement value of the hammer test is shown in Table 1. Here, the tool 6 with LT of 60 mm and DT of 20 mm is used as the reference tool. In addition, as described above, the correction coefficient M is equal to the correction coefficient C for the tool 6 serving as the reference tool. Therefore, for example, the correction coefficient T of the tool 6 with LT = 60 mm and DT = 12 mm is calculated by dividing the correction coefficient C of the tool by the correction coefficient M at each frequency and finding the average value.

[0053] The correction coefficient M is a value including a plurality of systems, namely, the support 5, the spindle 4, and the spindle housing 3, and is therefore associated with the machine information, the gripping tool information, and the reference tool information as a function of the frequency f.

[0054] By setting the correction coefficient C as a function of the frequency f in this way, even for a tool 6 for which the correction coefficient C is not obtained, the correction coefficient C can be calculated by interpolation or extrapolation of the correction coefficient T using an approximate formula based on the obtained correction coefficient C and the mathematical formula 1. Therefore, even if not all correction coefficients C are always stored in the correction coefficient storage unit 26, they can be used in the correction coefficient acquisition step S5 and the second vibration characteristic estimation step S6 by calculating and storing them in the correction coefficient storage unit 26 based on the obtained frequency, machine information, gripping tool information, and tool information. Therefore, even if the correction coefficient C related to the estimation target point of the vibration characteristic is not obtained, the vibration characteristic of the target point, that is, the second vibration characteristic, can be estimated using the correction coefficient C that has been obtained.

[0055] [Table 1]

[0056] LT\DT 12mm 16mm 20mm 60mm 4.7 1.8 1.0 70mm 5.6 2.2 1.3 80mm 7.5 2.8 1.6

[0057] Figure 5 and Figure 6 This is a comparison between the direct measurement result and the estimated result of the second vibration characteristic.

[0058] The following is based on Figure 2 In particular, the case where the correction coefficient C related to the tip of the tool 6 as the estimation target point of the vibration characteristic is not obtained was studied.

[0059] The direct measurement result and the estimated result when the tool 6 is installed on the bracket 5 according to the conditions of DT=16mm, LT=64mm are compared to study the estimation accuracy. The conditions such as DT=16mm, LT=64mm are included in the range shown in Table 1, that is, the range of the conditions such as 60mm≤LT≤80mm and 12mm≤DT≤20mm. Therefore, under the condition that DT is 16mm, based on the correction coefficient T obtained for the tool 6 with LT of 60mm, 70mm and 80mm, an approximate formula of the correction coefficient T related to LT is calculated, and the correction coefficient C is calculated by interpolating the correction coefficient T using the approximate formula, and the first vibration characteristic measured directly is corrected to estimate the second vibration characteristic. As a result, as shown in FIG. Figure 5 As shown, the second vibration characteristic can be estimated from the first vibration characteristic with high accuracy.

[0060] In addition, the direct measurement result and the estimated result when the tool 6 is installed on the bracket 5 according to the conditions of DT=20mm, LT=100mm are compared to study the estimation accuracy. The conditions such as DT=20mm, LT=100mm are not included in the range shown in Table 1, that is, the range of 60mm≤LT≤80mm and 12mm≤DT≤20mm. Therefore, under the condition that DT is 20mm, based on the correction coefficient T obtained for the tool 6 with LT of 60mm, 70mm and 80mm, an approximate formula for the correction coefficient T related to LT is calculated, and based on the extrapolation of the correction coefficient T using the approximate formula, the correction coefficient C is calculated, and the first vibration characteristic measured directly is corrected to estimate the second vibration characteristic. As a result, as shown in FIG. Figure 6 As shown, the second vibration characteristic can be estimated from the first vibration characteristic with high accuracy.

[0061] In addition, a method of obtaining the correction coefficient C for the tool 6 whose DT and LT are both the conditions shown in Table 1 is described by taking the case where the tool 6 is mounted on the holder 5 under the conditions of DT=18mm and LT=75mm as an example. First, under the condition of LT being 60mm, an approximate formula of the correction coefficient T related to DT is obtained based on the correction coefficient T obtained for the tool 6 having DT of 12mm, 16mm, and 20mm, and the correction coefficient T under the condition of LT=60mm and DT=18mm is obtained using the approximate formula. Similarly, the correction coefficient T under the conditions of LT=70mm and DT=18mm and LT=80mm and DT=18mm are obtained. Next, under the condition of DT being 18mm, an approximate formula of the correction coefficient T related to LT is obtained based on the correction coefficient T obtained for the tool 6 having LT of 60mm, 70mm, and 80mm, and the correction coefficient C is obtained by interpolation of the correction coefficient T using the approximate formula.

[0062] The vibration characteristic estimation system 21 of the above-mentioned structure has: in a machining center m that performs machining by relatively moving a tool 6 and a workpiece 8, a first vibration characteristic acquisition unit 22 is provided, which acquires a first vibration characteristic based on the output of an acceleration sensor 9 mounted on a spindle housing 3 of the machining center m when an excitation force is applied to the front end of the tool 6, which is the contact point between the tool 6 and the workpiece 8 being machined, i.e., the machining point; a mechanical information acquisition unit 23 is provided, which acquires mechanical information including the name of the machining center m, the axis structure, the component information, and the installation position information of the acceleration sensor 9; a holding device information acquisition unit 24 is provided, which acquires holding device information including the name, size, and material of the bracket 5 for holding the tool 6, and the holding method of the tool 6; a machining unit information acquisition unit 25 is provided, which acquires information including the tool information; Tool information including the name, size and material of tool 6; a correction coefficient storage unit 26, which stores a correction coefficient C representing the ratio of a first vibration characteristic to a second vibration characteristic in association with mechanical information, holding device information and tool information, wherein the second vibration characteristic is based on the vibration amount of the front end of the tool 6 when an exciting force is applied to the front end of the tool 6; a correction coefficient acquisition unit 27, which obtains the correction coefficient C based on the mechanical information, the holding device information and the tool information from the correction coefficient storage unit 26; and a second vibration characteristic estimating unit 28, which uses the correction coefficient C obtained by the correction coefficient acquisition unit 27 to correct the first vibration characteristic obtained by the first vibration characteristic acquisition unit 22, and estimates the second vibration characteristic, the correction coefficient C being constructed based on the mechanical information and a frequency associated with the mechanical information, and the frequency being obtained from the spindle housing 3.

[0063] Therefore, in the machining center m, the vibration characteristic of the spindle housing 3, which is the point where the acceleration sensor 9 can be easily installed, i.e., the first vibration characteristic, is corrected based on the mechanical information, the holding device information, and the tool information, so that the second vibration characteristic, which is the vibration characteristic of the front end of the tool 6, which is difficult to install the acceleration sensor 9, can be estimated with high precision.

[0064] In addition, the correction coefficient C of the above configuration includes a constant associated with the tool information and is a frequency function associated with the machine information.

[0065] Therefore, even when the correction coefficient C related to the tip of the tool 6 , which is the estimation target point of the vibration characteristic, is not acquired, the acquired correction coefficient C can be used to estimate the vibration characteristic of the tip of the tool 6 , which is the second vibration characteristic.

[0066] In addition, the present disclosure is described above based on the illustrated examples, and its technical scope is not limited to this. The structures involved in the vibration characteristic estimation system, machine tool and vibration characteristic estimation method in the machine tool disclosed in the present disclosure are not limited to the methods described in the above embodiments, and can be appropriately changed as needed without departing from the scope of the invention.

[0067] For example, the first vibration characteristic and the second vibration characteristic are not limited to flexibility, but may be other values ​​such as mobility or inertia. Furthermore, as long as they can be calculated by correcting the first vibration characteristic based on the correction coefficient, the first vibration characteristic and the second vibration characteristic may be a combination of different types of values.

[0068] The sensor used as the basis for obtaining the output of the first vibration characteristic is not limited to the acceleration sensor, and may be, for example, an encoder included in the spindle motor, the X-axis motor, the Y-axis motor, and the Z-axis motor. In this case, the correction coefficient M includes a component up to the installation position of the encoder.

[0069] In this embodiment, the mechanical information acquisition unit acquires mechanical information from the NC device, but it may be acquired from a device other than the NC device, such as an external information device, or directly input by separately providing an input unit, etc. The same applies to the gripper information acquisition unit and the processing unit information acquisition unit.

[0070] Furthermore, the components included in the correction coefficient T and the correction coefficient M are not limited to the combination of the tool information, the machine information, and the holding device information. For example, the correction coefficient M may be set to the correction coefficient C when the combination of the tool 6 and the bracket 5 as the reference tool is mounted on the spindle 4, and the correction coefficient T may be set to the ratio of the correction coefficient C of the reference tool bracket to the correction coefficient C of the combination of the tool 6 and the bracket 5 as the estimation object, and the holding device information may be associated with the correction coefficient T. Furthermore, by approximating the correction coefficient T with the dimensions of the tool 6 at DT and LT and the dimensions of the bracket 5 at DH and LH, the dimensions of the bracket 5 at DH' and LH' for which the correction coefficient C is not obtained can also be estimated in the same manner as in the embodiment.

[0071] In addition, in the present embodiment, the estimated object point of the vibration characteristic is set to the tool tip and the second vibration characteristic is set to the flexibility of the tool tip, but the estimated object point of the vibration characteristic can also be set to the workpiece and the second vibration characteristic can be estimated as the flexibility of the workpiece. In this case, the acceleration sensor 9 is installed on the workbench 7 on which the workpiece 8 is installed, and the frequency is obtained from the workbench 7. Then, in S3, the gripping tool information acquisition unit 24 acquires the workpiece gripping tool information including the workpiece gripping tool name, workpiece gripping tool size, position, gripping force and gripping direction, etc., and the workpiece gripping tool material from the gripping tool information storage unit 14. In addition, in S4, the processing unit information acquisition unit 25 acquires the workpiece information including the workpiece name, workpiece size and workpiece material from the workpiece information storage unit that stores the workpiece information of the NC device 11. In addition, in S5, the correction coefficient acquisition unit 27 acquires the correction coefficient C from the correction coefficient storage unit 26 based on at least one of the mechanical information, the workpiece gripping tool information and the workpiece information.

[0072] In addition, the applicable objects of the present disclosure are not limited to machining centers, as long as they are machine tools that perform machining by relatively moving a tool and a workpiece, and include, for example, a compound processing machine, in which case the acceleration sensor may be mounted on the spindle housing of a workpiece spindle that rotates the workpiece to estimate the flexibility of the workpiece. In addition, lathes are also included, in which case the acceleration sensor may be mounted on a tool holder on which a non-rotating tool is mounted to estimate the flexibility of the tool. In this case, the frequency is obtained from the tool holder.

[0073] Here, for comparison with the embodiment, the first vibration characteristic and the second vibration characteristic are defined as compliance, but as described above, the first vibration characteristic and the second vibration characteristic are not limited to compliance.

Claims

1. A vibration characteristic estimation system in a machine tool, characterized in that: In a machine tool that performs machining by moving the tool and the workpiece relative to each other, there are: a first vibration characteristic acquisition unit that acquires a first vibration characteristic based on an output of a sensor mounted on the machine tool when an exciting force is applied to a machining point that is a contact point between the tool and the workpiece during machining; a machine information acquisition unit configured to acquire machine information including at least one of a name of the machine tool, an axis structure, component information, and installation position information of the sensor; a gripping tool information acquisition unit that acquires gripping tool information, the gripping tool information including at least one of a name, size, and material of a gripping tool for gripping the tool or the workpiece, and a gripping method for the tool or the workpiece; a processing unit information acquisition unit, which acquires at least one of tool information and workpiece information, wherein the tool information includes at least one of the name, size and material of the tool, and the workpiece information includes at least one of the name, size and material of the workpiece; a correction coefficient storage unit that stores a correction coefficient indicating a ratio of the first vibration characteristic to a second vibration characteristic based on a vibration amount of the processing point when an exciting force is applied to the processing point, in association with at least one of the machine information, the gripping tool information, the tool information, and the workpiece information; a correction coefficient acquisition unit that acquires the correction coefficient based on at least one of the machine information, the gripping tool information, the tool information, and the workpiece information from the correction coefficient storage unit; as well as a second vibration characteristic estimating unit that estimates the second vibration characteristic by correcting the first vibration characteristic acquired by the first vibration characteristic acquiring unit using the correction coefficient acquired by the correction coefficient acquiring unit, The correction coefficient is formed as a function based on the mechanical information and a frequency associated with the mechanical information, The frequency is obtained from the sensor.

2. The vibration characteristic estimation system in a machine tool according to claim 1, characterized in that: The correction coefficient includes at least a constant associated with the tool information.

3. The vibration characteristic estimation system in a machine tool according to claim 1, characterized in that: The correction coefficient is a frequency function associated with at least the mechanical information.

4. A machine tool, characterized in that: This machine tool includes the vibration characteristic estimating system according to any one of claims 1 to 3.

5. A method for estimating vibration characteristics in a machine tool, characterized in that: In a machine tool that performs machining by moving the tool and the workpiece relative to each other, the following steps are included: a first vibration characteristic acquisition step of acquiring a first vibration characteristic representing an output of a sensor mounted on the machine tool when an exciting force is applied to the tool or a processing point of the workpiece, the processing point being a contact point between the tool and the workpiece during processing; A machine information acquisition step of acquiring machine information, the machine information including at least one of the name of the machine tool, the axis structure, the component information, and the installation position information of the sensor; A grasping tool information acquisition step of acquiring grasping tool information, the grasping tool information including at least one of a name, size, and material of a grasping tool for grasping the tool or the workpiece, and a grasping method of the tool or the workpiece; a processing part information acquisition step, acquiring at least one of tool information and workpiece information, wherein the tool information includes at least one of the name, size and material of the tool, and the workpiece information includes at least one of the name, size and material of the workpiece; a correction coefficient obtaining step of obtaining a correction coefficient indicating a ratio of the first vibration characteristic to a second vibration characteristic indicating a vibration amount of the processing point when an exciting force is applied to the processing point based on at least one of the machine information, the holding tool information, the tool information, and the workpiece information; and a second vibration characteristic estimating step of estimating the second vibration characteristic by correcting the first vibration characteristic acquired in the first vibration characteristic acquiring step using the correction coefficient acquired in the correction coefficient acquiring step, The correction coefficient is formed based on the mechanical information and a frequency associated with the mechanical information, The frequency is obtained from the sensor.

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