JP2024013720A - Machining condition setting method and machine tool - Google Patents

Abstract

To suppress chatter vibrations while cutting.SOLUTION: A machining condition setting method setting a machining condition for cutting has: a measuring step which measures a cutting force added to a workpiece from a cutting tool and vibrations at a plurality of measurement points of the workpiece while applying first trial machining to the workpiece with the cutting tool; a vibration estimation step which uses a measurement result of vibrations during the first trial machining at the plurality of measurement points to estimate vibrations of the workpiece at the cutting point; a frequency analysis step which performs a frequency analysis of the measurement result of the cutting force during the first trial machining and vibrations estimation result; a machining condition selection map creating step which uses a result of frequency analysis of the cutting force and a frequency analysis result of vibrations to create a machining condition selection map showing a relation between the cutting position on the workpiece when applying major machining to the workpiece with the cutting tool and prediction values of the machining condition and the vibration amplitude; and a setting step which uses the machining condition selection map to set the machining condition during the major machining so that the vibration amplitude is predetermined value or smaller.SELECTED DRAWING: Figure 7

Description

The present disclosure relates to a machining condition setting method and a machine tool.

Patent Document 1 discloses an apparatus that supports the design of a jig installed to suppress chatter vibration of a workpiece to be cut. This device uses CAE (Computer Aided Engineering) analysis results to predict the machining accuracy of the workpiece, and if it is predicted that the desired machining accuracy will not be achieved, it will change the design data of the jig, etc. Let the user do it.

JP 2019-118973 Publication

When chatter vibration occurs during cutting, machining accuracy decreases. Therefore, it is required to suppress chatter vibration during cutting. In Patent Document 1, chatter vibration during cutting is suppressed by changing the design of the jig. However, there are cases where it is difficult to change the design of the jig, or it is difficult to install the jig itself. Therefore, there is a need for a technique for suppressing chatter vibration without changing the design of the jig.

The present disclosure can be realized as the following forms.

(1) According to the first aspect of the present disclosure, a processing condition setting method for setting processing conditions for cutting is provided. This machining condition setting method involves measuring the cutting force applied to the workpiece by the cutting tool and vibrations at a plurality of measurement points of the workpiece while performing a first trial machining on the workpiece using the cutting tool. a vibration estimation step of estimating the vibration of the workpiece at the cutting position using the measurement results of the vibration during the first trial machining at the plurality of measurement points; a frequency analysis step of frequency-analyzing the measurement result of the cutting force and the estimation result of the vibration; and performing main processing on the workpiece with a cutting tool using the frequency analysis result of the cutting force and the frequency analysis result of the vibration. a machining condition selection map creation step of creating a machining condition selection map that represents the relationship between the cutting position on the workpiece, the machining conditions, and the predicted value of vibration amplitude; and a setting step of setting the machining conditions during the main machining so that the vibration amplitude is equal to or less than a predetermined value.
According to this method of setting machining conditions, machining conditions are set using a machining condition selection map that represents the relationship between cutting positions, machining conditions, and predicted values of vibration amplitude. Therefore, practical machining conditions suitable for suppressing chatter vibration can be set without trial and error. Therefore, even if it is difficult to install the jig or change the design of the jig, chatter vibration can be suppressed by changing the machining conditions.
(2) In the machining condition setting method of the above embodiment, prior to the machining condition selection map creation step, the frequency analysis result at the cutting position is calculated using the frequency analysis result of the cutting force and the frequency analysis result of the vibration. Determine whether the maximum value of compliance of the workpiece exceeds a predetermined threshold, and if it is determined that the maximum value of compliance of the workpiece does not exceed the threshold, perform the process of creating the machining condition selection map. May be executed.
According to this method of setting machining conditions, machining conditions can be set while the rigidity of the workpiece is ensured. Therefore, chatter vibration can be effectively suppressed.
(3) In the machining condition setting method of the above form, if it is determined that the maximum compliance value of the workpiece exceeds the threshold value, is it possible to take measures to improve the rigidity of the workpiece? If a determination result indicating that the countermeasure is not possible is obtained, then after the countermeasure is executed, the process returns to the measurement step and a determination is made that the countermeasure is not possible. If the determination result is obtained, the processing condition selection map creation step may be executed.
According to this method of setting machining conditions, machining conditions can be set while the lack of rigidity of the workpiece is resolved as much as possible. Therefore, chatter vibration can be effectively suppressed.
(4) In the machining condition setting method of the above embodiment, a second trial machining is performed on the workpiece using the cutting tool according to the machining conditions set using the machining condition selection map, and forced chatter vibration of the workpiece is If a determination result is obtained as to whether the forced chatter vibration of the workpiece occurred during the second trial machining, and if a determination result is obtained that the forced chatter vibration of the workpiece occurred during the second trial machining, the forced chatter vibration Countermeasures may be implemented to suppress the occurrence of
According to this method of setting machining conditions, by implementing a countermeasure for suppressing the occurrence of forced chatter vibration prior to the main machining, it is possible to suppress the occurrence of forced chatter vibration in the main machining.
(5) In the machining condition setting method of the above embodiment, a second trial machining is performed on the workpiece using the cutting tool according to the machining conditions set using the machining condition selection map, and self-excited chatter vibration of the workpiece is generated. If a determination result is obtained as to whether or not self-excited chatter vibration of the workpiece occurred during the second trial machining, and a determination result is obtained that self-excited chatter vibration of the workpiece occurred during the second trial machining, the automatic Countermeasures may be implemented to suppress the occurrence of chatter vibrations.
According to this method of setting machining conditions, by implementing a countermeasure for suppressing the occurrence of self-excited chatter vibration prior to main machining, it is possible to suppress the occurrence of self-excited chatter vibration during main machining.
(6) In the machining condition setting method of the above embodiment, the machining condition is the feed amount per tooth of the cutting tool, and in the setting step, the first and a second condition in which the feed amount per tooth is changed during machining so that the machining time is shorter than the first condition, and the machining conditions during the main machining are set. May be set.
According to this method of setting machining conditions, by selecting the first condition, predetermined machining accuracy can be satisfied, and by selecting the second condition, the machining time can be further shortened. The machining conditions to be set include the feed amount per cutting tool, the rotational speed of the cutting tool TL, and the axial direction (Z-axis in Fig. 1) or radial direction (Y-axis in Fig. 1) of the cutting tool TL. It may also be the depth of cut of the shaft.
(7) According to the second aspect of the present disclosure, a machine tool that performs cutting on a workpiece using a cutting tool is provided. This machine tool includes a machining condition setting section that sets machining conditions for the cutting process. The machining condition setting unit is configured to control a cutting force applied to the workpiece from the cutting tool and vibrations at a plurality of measurement points of the workpiece while performing a first trial machining on the workpiece with the cutting tool. and estimate the vibration of the workpiece at the cutting position using the measurement results of the vibration during the first trial machining at the plurality of measurement points, and the measurement result of the cutting force during the first trial machining. and the estimation result of the vibration, and using the frequency analysis result of the cutting force and the frequency analysis result of the vibration, determine the cutting position on the workpiece when main machining is performed on the workpiece with a cutting tool. A machining condition selection map is created that represents the relationship between the machining conditions and the predicted value of vibration amplitude, and using the machining condition selection map, the main machining is performed so that the vibration amplitude is equal to or less than a predetermined value. Set the processing conditions at the time.
According to this type of machine tool, the machining condition setting section sets machining conditions using a machining condition selection map that represents the relationship between cutting positions, machining conditions, and predicted values of vibration amplitude. Therefore, the operator can set practical machining conditions suitable for suppressing chatter vibration without trial and error. Therefore, even if it is difficult to install the jig or change the design of the jig, chatter vibration can be suppressed by changing the machining conditions.
The present disclosure can also be realized in various forms other than a machining condition setting method and a machine tool. For example, it can be realized in the form of a machining condition setting device, a machining condition selection map creation method, a machining condition selection map creation device, etc.

FIG. 1 is a perspective view showing a schematic configuration of a machine tool. FIG. 3 is a side view showing an example of the layout of a support member. FIG. 3 is a rear view showing an example of the layout of the support member. The first flowchart showing the contents of processing condition setting processing. The second flowchart showing the contents of processing condition setting processing. An explanatory diagram showing an example of a compliance map. An explanatory diagram showing an example of a processing condition selection map. An explanatory diagram showing the surface roughness of the machined surface after main processing.

A. First embodiment:
FIG. 1 is a perspective view showing a schematic configuration of a machine tool 11 in the first embodiment. In this embodiment, the machine tool 11 is configured as a vertical machining center. The machine tool 11 has three coordinate axes, X, Y, and Z axes, which are orthogonal to each other. In this embodiment, the X-axis is a coordinate axis along the left-right direction of the machine tool 11, the Y-axis is a coordinate axis along the front-back direction of the machine tool 11, and the Z-axis is a coordinate axis along the up-down direction of the machine tool 11. It is.

The machine tool 11 includes a bed 20, a saddle 30, a table 40, a column 50, a spindle device 60, a cutting force sensor 70, three vibration sensors 80A to 80C, and a control device 100.

Saddle 30 is supported by bed 20. The saddle 30 moves along the Y axis while being guided by the bed 20. The table 40 is supported by the saddle 30. The table 40 moves along the X-axis while being guided by the saddle 30. A workpiece WK is fixed to the table 40. In this embodiment, the workpiece WK is fixed to the table 40 by clamping the lower end of the workpiece WK by a clamp 45 fixed to the table 40. Column 50 is fixed to bed 20. The main shaft device 60 is supported by the column 50. The main shaft device 60 moves along the Z-axis while being guided by the column 50.

The main shaft device 60 includes a main shaft 65, a main shaft motor 67, and a rotation angle sensor 69. A cutting tool TL for cutting the workpiece WK is attached to the main shaft 65. The main shaft motor 67 rotates the main shaft 65 and the cutting tool TL around a rotation axis parallel to the Z-axis. For example, a servo motor can be used as the main shaft motor 67. The cutting tool TL has a substantially cylindrical shape centered on a central axis, and has at least one blade on a side surface. In this embodiment, the cutting tool TL is an end mill, and has two blades arranged at equal intervals along the circumferential direction around the central axis. In addition, in other embodiments, the number of blades of the cutting tool TL may be one, or may be three or more. The cutting tool TL may be a milling tool other than an end mill, such as a flat milling cutter, for example. The rotation angle sensor 69 detects the rotation angle of the main shaft 65, in other words, the rotation angle of the cutting tool TL. Information regarding the rotation angle detected by the rotation angle sensor 69 is transmitted to the control device 100. For example, a rotary encoder can be used as the rotation angle sensor 69.

The cutting force sensor 70 is provided on the main shaft 65. The cutting force sensor 70 detects the cutting force applied from the cutting tool TL to the workpiece WK. Information regarding the cutting force detected by the cutting force sensor 70 is transmitted to the control device 100. For example, a cutting dynamometer can be used as the cutting force sensor 70.

Three vibration sensors 80A to 80C are installed on the workpiece WK. Each vibration sensor 80A to 80C detects a physical quantity representing the vibration state of the workpiece WK. Information regarding the physical quantity representing the vibration state detected by each of the vibration sensors 80A to 80C is transmitted to the control device 100. Physical quantities representing the vibration state include acceleration, velocity, and displacement. In this embodiment, each of the vibration sensors 80A to 80C is an acceleration sensor that detects the acceleration of the workpiece WK. In the following description, the points on the workpiece WK where the vibration sensors 80A to 80C are installed may be referred to as measurement points MP1 to MP3. Note that the number of vibration sensors 80A to 80C may be the minimum number necessary to estimate the vibration of the workpiece WK at the cutting position during cutting. In other embodiments, each of the vibration sensors 80A to 80C may be a displacement sensor that detects the displacement of the workpiece WK or a speed sensor that detects the speed of the workpiece WK instead of an acceleration sensor. Further, in this embodiment, contact type vibration sensors are used as the vibration sensors 80A to 80C, but in other embodiments, non-contact type vibration sensors may be used.

The control device 100 is configured as a computer including a CPU 101, a memory 102, an input/output interface 103, and an internal bus 104. The CPU 101 functions as the NC control section 110 and the processing condition setting section 120 by executing a computer program stored in the memory 102.

The NC control unit 110 controls each motor of the machine tool 11 such as the spindle motor 67 according to predetermined machining conditions, brings the rotating cutting tool TL into contact with the workpiece WK, and performs cutting on the workpiece WK. Execute. In the following description, the cutting process for manufacturing a product will be referred to as main processing, and the cutting process performed prior to main processing will be referred to as trial processing.

The machining condition setting unit 120 sets machining conditions for cutting. The machining conditions include the rotational speed of the cutting tool TL, the feed rate per blade of the cutting tool TL, and the depth of cut in the radial and axial directions of the cutting tool TL into the workpiece WK. The machining condition setting unit 120 sets machining conditions used in the main machining by executing a machining condition setting process to be described later.

An input device 105 and a display device 106 are connected to the control device 100 . The input device 105 includes, for example, a plurality of operation buttons. The display device 106 is composed of, for example, a liquid crystal display. Input device 105 and display device 106 may be integrated as a touch panel.

FIG. 2 is a side view showing an example of the layout of the support member 48. FIG. 3 is a rear view showing an example of the layout of the support member 48. As shown in FIG. 2, in addition to the clamp 45 for fixing the workpiece WK to the table 40, a support member 48 for suppressing chatter vibration of the workpiece WK during cutting may be used. In this embodiment, the support member 48 is formed into a rod shape with a circular cross section. One end of the support member 48 contacts a part of the workpiece WK that is different from the part held by the clamp 45, and the other end of the support member 48 is fixed to the table 40 via a fixing member 49. . As shown in FIG. 3, the workpiece WK is supported by one support member 48, for example. Cutting is performed on the surface of the workpiece WK opposite to the surface supported by the support member 48 using the cutting tool TL. Vibration sensors 80A to 80C are installed on the surface of the workpiece WK that is supported by the support member 48. Note that in other embodiments, the support member 48 may be formed not in a rod shape but in a plate shape, a block shape, or a spherical shape, for example. The number of support members 48 is not limited to one, and may be two or more. If the rigidity of the workpiece WK is sufficiently high, the support member 48 may not be provided.

4 and 5 are flowcharts showing the contents of the machining condition setting process. FIG. 6 is an explanatory diagram showing an example of a compliance map created in the processing condition setting process. FIG. 7 is an explanatory diagram showing an example of a machining condition selection map created in the machining condition setting process. The machining condition setting process shown in FIGS. 4 and 5 is executed by the machining condition setting unit 120 in order to set machining conditions for main machining. The machining condition setting process is started, for example, by pressing a start button provided on the input device 105 prior to the main machining. Note that the method executed in the machining condition setting process may be referred to as a machining condition setting method.

First, in step S110 in FIG. 4, the machining condition setting unit 120 causes the NC control unit 110 to perform trial machining, and uses the cutting force sensor 70 to transfer the power from the cutting tool TL to the workpiece WK at each time during the trial machining. The applied cutting force is measured, and the acceleration generated at each measurement point MP1 to MP3 on the workpiece WK at each time during trial machining is measured using the vibration sensors 80A to 80C. In this embodiment, as shown in FIG. 3, the NC control unit 110 runs a machining path from a machining start point SP to a machining end point that passes behind each measurement point MP1 to MP3 where each vibration sensor 80A to 80C is installed. Trial machining is performed on the workpiece WK up to point EP. Note that the trial machining performed in step S110 may be referred to as a first trial machining. Step S110 may be called a measurement process.

In step S115, the machining condition setting unit 120 calculates the vibration between the machining start point SP and the machining end point EP at each time during trial machining using the acceleration measurement results at each measurement point MP1 to MP3. presume. In this embodiment, the machining condition setting unit 120 determines the machining start point by linear extrapolation using the acceleration of the measurement point MP1 closest to the machining start point SP and the acceleration of the measurement point MP2 second closest to the machining start point SP. The acceleration between SP and the measurement point MP1 closest to the machining start point SP is estimated. The processing condition setting unit 120 estimates the acceleration between adjacent measurement points by linear interpolation using the accelerations of two adjacent measurement points. The machining condition setting unit 120 determines the machining end point EP and the machining end by linear extrapolation using the acceleration of the measurement point MP3 closest to the machining end point EP and the acceleration of the measurement point MP2 second closest to the machining end point EP. The acceleration between the point EP and the closest measurement point MP3 is estimated. Note that in other embodiments, the machining condition setting unit 120 estimates the vibration between the machining start point SP and the machining end point EP by, for example, the Lagrangian method or the spline method instead of linear interpolation or linear extrapolation. It's okay. Note that step S115 may be referred to as a vibration estimation step.

In step S120, the machining condition setting unit 120 performs frequency analysis on the cutting force measurement results and the acceleration estimation results. In this embodiment, the machining condition setting unit 120 extracts the results for one blade from each of the measurement results of cutting force and the estimation results of acceleration, and then quickly converts the results for one blade expressed in the time domain. By performing Fourier transformation, the results are converted into results for one blade expressed in the frequency domain. The result for one blade means the measurement result or estimated result of the period from when the blade of the cutting tool TL cuts into the workpiece WK to when the blade of the cutting tool TL next cuts into the workpiece WK. The time from when the blade of the cutting tool TL contacts the workpiece WK to when the blade of the cutting tool TL next contacts the workpiece WK is sometimes referred to as a cutting edge passing period. When a cutting tool TL having a plurality of blades arranged at equal intervals is used, the cutting edge passing period is, for example, the rotation period of the cutting tool TL measured using the rotation angle sensor 69, or the number of blades of the cutting tool TL. It can be calculated by dividing by Note that, prior to the fast Fourier transform, the machining condition setting unit 120 adds a predetermined number of zero data to the end of each result for one blade so that the number of data for each result for one blade becomes a power of two. Fast Fourier transform may be performed after addition. Zero data is data indicating that the value of cutting force or the value of acceleration is zero. By adding zero data to each result for one blade, it is possible to increase the frequency resolution of each result after fast Fourier transform. Note that step S120 may be referred to as a frequency analysis step.

In step S125, the machining condition setting unit 120 uses the cutting force frequency analysis results and the displacement frequency analysis results to determine the relationship between the frequency at the cutting position on the workpiece WK and the compliance height of the workpiece WK. Create a compliance map that represents the distribution. FIG. 6 shows an example of a compliance map. In FIG. 6, the horizontal axis represents the cutting position on the workpiece WK, the vertical axis represents the frequency, and the shade of color represents the height of compliance of the workpiece WK. In FIG. 6, the lighter the color, the higher the compliance. Compliance is the reciprocal of stiffness, so the higher the compliance, the lower the stiffness. The processing condition setting unit 120 calculates the compliance at each cutting position and each frequency, and creates a compliance map by aggregating the compliance calculation results. In this embodiment, the machining condition setting unit 120 calculates the displacement by dividing the acceleration by (2π×frequency) ² , and calculates the compliance by dividing the displacement by the cutting force. Note that step S125 may be referred to as a compliance map creation step.

In step S130, processing condition setting unit 120 determines whether the maximum value of compliance in the compliance map exceeds a predetermined threshold. In this embodiment, the predetermined threshold is 1.0×10 ⁻⁶ m/N.

If it is determined in step S130 that the maximum value of compliance in the compliance map exceeds a predetermined threshold value, the machining condition setting unit 120 sets a workpiece WK in order to improve the rigidity of the workpiece WK in step S140. Obtain the determination result as to whether or not it is possible to implement measures to improve rigidity. In the present embodiment, the machining condition setting unit 120 displays on the display device 106 a request for determining whether or not the workpiece rigidity improvement measures are possible, thereby determining whether or not the workpiece rigidity improvement measures are possible. Have the worker input the determination result. Measures to improve the workpiece rigidity in this embodiment include installing a support member 48 that supports a portion of the workpiece WK where the rigidity is insufficient or a peripheral portion of the portion where the rigidity is insufficient. The worker inputs the determination result into the input device 105, and the processing condition setting unit 120 acquires the determination result input into the input device 105.

If a determination result indicating that it is possible to take measures to improve workpiece rigidity is obtained in step S140, the machining condition setting unit 120 causes the display device 106 to display a compliance map in step S145. The worker refers to the compliance map displayed on the display device 106 and executes measures to improve the workpiece rigidity. After completing the measures to improve the workpiece rigidity, the machining condition setting unit 120 sets the machining conditions from step S110. Redo the process.

If it is determined in step S130 that the maximum value of compliance in the compliance map does not exceed the predetermined threshold, processing condition setting unit 120 advances the process to step S150 in FIG. 5. Even when the determination result that the workpiece rigidity improvement measures are not possible is acquired in step S140, the processing condition setting unit 120 advances the process to step S150. In other words, when the desired rigidity of the workpiece WK is ensured or when the rigidity is increased as much as possible, the machining condition setting unit 120 advances the process to step S150.

In step S150, the machining condition setting unit 120 creates a machining condition selection map that represents the relationship between the magnitude of the predicted value of the vibration amplitude of the workpiece WK at each cutting position on the workpiece WK, and displays it on the display device 106. Display. The machining condition selection map is used to select machining conditions such as the rotational speed of the cutting tool TL, the feed amount per tooth of the cutting tool TL, and the depth of cut of the cutting tool TL into the workpiece WK, in order to improve machining efficiency and machining accuracy. This is a map used for selection according to the purpose of the worker. FIG. 7 shows an example of a machining condition selection map. In Fig. 7, the horizontal axis represents the cutting position on the workpiece WK, the vertical axis represents the feed amount per tooth, and the shade of color represents the magnitude of the predicted value of vibration amplitude. ing. In FIG. 7, the darker the color, the larger the predicted value of the vibration amplitude. In this embodiment, in step S150, the machining condition setting unit 120 first specifies modal parameters such as the mass M, the damping coefficient C, and the spring constant K from the vibration mode at the cutting position. For example, the machining condition setting unit 120 creates a graph representing the relationship between frequency and compliance for each cutting position, and identifies the frequency at which the compliance peak exceeds a predetermined threshold. A plurality of frequencies may be specified at this time. By deriving a transfer function that matches the peak shape for each specified frequency by curve fitting processing, it is possible to specify modal parameters such as the mass M, damping coefficient C, and spring constant K of each vibration mode. Next, the machining condition setting unit 120 calculates a predicted value of vibration amplitude during machining from the modal parameters for each cutting position and arbitrarily set machining condition parameters. The machining condition setting unit 120 may be configured, for example, by Takaaki Hashimoto, Daisuke Kono, Masataka Furusawa, and Atsushi Matsubara, "Influence of anisotropy of dynamic characteristics of cutting system on vibration stability," Journal of the Japan Society for Precision Engineering, Vol. 87 No. 2, 2021, p. A predicted value of the vibration amplitude during machining can be calculated by following the method of determining the vibration amplitude during machining as shown in 238 to 244. Then, the machining condition setting unit 120 creates a machining condition selection map that represents the distribution of predicted vibration amplitude values for each cutting position. FIG. 7 shows an example of a machining condition selection map when it is determined in step S140 that measures to improve workpiece rigidity are not possible. In this embodiment, the machining condition parameters include the outer diameter of the cutting tool TL, the number of teeth, the helix angle, the rotational speed, the depth of cut in the radial direction and the axial direction, and the component force ratio (normal resistance and tangential resistance acting on the cutting tool TL). (resistance ratio) and the specific cutting resistance of the workpiece WK, and determine the feed amount per tooth of the cutting tool TL so that the magnitude of the predicted value of vibration amplitude is equal to or less than a predetermined value. can do. In addition to this, the machining condition setting unit 120 may determine machining conditions such as the depth of cut in the radial direction or the axial direction of the cutting tool TL so that the magnitude of the predicted value of the vibration amplitude is equal to or less than a predetermined value. good. Note that step S150 may be referred to as a machining condition selection map creation step.

In step S155, the machining condition setting unit 120 sets a first condition F1 that prioritizes high machining accuracy over short machining time, and a second condition F2 that prioritizes short machining time over high machining accuracy. A screen for selecting the first condition F1 and the second condition F2 is displayed on the display device 106, and the worker is made to select one of the first condition F1 and the second condition F2. The machining condition setting unit 120 generates the first condition and the second condition using the machining condition selection map. Under the first condition F1, the feed amount per blade is kept constant so that the predicted value of vibration amplitude is equal to or less than a predetermined value at all cutting positions from the machining start point SP to the machining end point EP. In the second condition F2, the predicted value of vibration amplitude is equal to or less than a predetermined value at all cutting positions from the machining start point SP to the machining end point EP, and the machining time is shorter than in the first condition. The feed amount per tooth is changed between the machining start point SP and the machining end point EP. Note that step S155 may be referred to as a setting step.

In step S160, the machining condition setting unit 120 causes the NC control unit 110 to perform a second trial machining using the machining conditions selected in step S155.

In step S170, the machining condition setting unit 120 obtains a determination result as to whether or not forced chatter vibration occurred in the workpiece WK during the second trial machining. In the present embodiment, the machining condition setting unit 120 displays on the display device 106 a determination request as to whether or not forced chatter vibration has occurred in the workpiece WK during the second trial machining. The operator is made to input the determination result as to whether or not forced chatter vibration has occurred in the workpiece WK. The worker inputs the determination result of whether forced chatter vibration has occurred into the input device 105, and the machining condition setting unit 120 inputs the determination result of whether forced chatter vibration has occurred, which is input into the input device 105. get.

If a determination result indicating that forced chatter vibration has occurred in the workpiece WK during the second trial machining is obtained in step S170, the machining condition setting unit 120 determines that the vibration is pre-stored in the memory 102 in step S175. While displaying the forced chatter vibration countermeasure plan KT on the display device 106, the system waits until execution of the forced chatter vibration countermeasure is completed. The forced chatter vibration countermeasure plans KT include, for example, a plan to reduce the feed amount per blade, a plan to reduce the depth of cut in at least one of the radial direction and the axial direction. The worker refers to the forced chatter vibration countermeasure plan KT displayed on the display device 106 and executes the forced chatter vibration countermeasure. After the forced chatter vibration countermeasures are completed, the worker inputs into the input device 105 that the forced chatter vibration countermeasures have been completed. When the completion of the forced chatter vibration countermeasure is input to the input device 105, the machining condition setting unit 120 redoes the machining condition setting process from step S150. If a determination result indicating that forced chatter vibration did not occur during the second trial machining is obtained in step S170, the machining condition setting unit 120 advances the process to step S180.

In step S180, the machining condition setting unit 120 obtains a determination result as to whether self-excited chatter vibration has occurred in the workpiece WK during the second trial machining. In the present embodiment, the machining condition setting unit 120 displays on the display device 106 a determination request as to whether or not self-excited chatter vibration has occurred in the workpiece WK during the second trial machining. The operator is asked to input the determination result as to whether or not self-excited chatter vibration has occurred in the workpiece WK. The worker inputs the determination result of whether self-excited chatter vibration has occurred into the input device 105, and the machining condition setting unit 120 inputs the determination result of whether self-excited chatter vibration has occurred, which is input into the input device 105. Obtain the judgment result.

If the determination result that self-excited chatter vibration has occurred in the workpiece WK during the second trial machining is obtained in step S180, the machining condition setting unit 120 determines that the self-excited chatter vibration has occurred in the memory 102 in step S185. While displaying the self-excited chatter vibration countermeasure plan JT on the display device 106, the system waits until the execution of the self-excited chatter vibration countermeasure is completed. The self-excited chatter vibration countermeasure plan JT includes, for example, a plan to change the spindle rotational speed, a plan to reduce the depth of cut in at least one of the radial direction and the axial direction. The worker refers to the self-excited chatter vibration countermeasure plan JT displayed on the display device 106 and executes the self-excited chatter vibration countermeasure. After the self-excited chatter vibration countermeasures are completed, the worker inputs into the input device 105 that the self-excited chatter vibration countermeasures have been completed. When the completion of the self-excited chatter vibration countermeasure is input to the input device 105, the machining condition setting unit 120 redoes the machining condition setting process from step S150. Note that by implementing measures to suppress the occurrence of one of forced chatter vibration and self-excited chatter vibration, chatter vibration of the other may occur. In this embodiment, when forced chatter vibration countermeasures are executed in step S175, the machining condition setting process is redone from step S150, so it is possible to confirm that both forced chatter vibration and self-excited chatter vibration do not occur. can. Further, even when the self-excited chatter vibration countermeasure is executed in step S185, the machining condition setting process is redone from step S150, so it can be confirmed that both forced chatter vibration and self-excited chatter vibration do not occur.

If a determination result that self-excited chatter vibration did not occur during the second trial machining is obtained in step S180, or if either forced chatter vibration or self-excited chatter vibration occurs during the second trial machining. If a determination result is obtained that no chatter vibration occurred in the second trial machining performed again after taking measures against chatter vibration, the machining condition setting unit 120 ends the machining condition setting process. . Thereafter, the main machining is performed according to the machining conditions set in step S155 of the machining condition setting process. Note that during the main processing, the vibration sensors 80A to 80C may be removed from the workpiece WK.

FIG. 8 is an explanatory diagram showing the surface roughness of the machined surface after main processing. In FIG. 8, the horizontal axis represents the cutting position, and the vertical axis represents the surface roughness of the machined surface of the workpiece WK. FIG. 8 shows the surface roughness when machining is performed under the first condition F1 with a small feed amount per tooth, and the surface roughness when machining is performed under the second condition F2 where the feed amount per tooth is variable. The surface roughness obtained when machining is performed under the third condition F3 in which the feed amount per tooth is large is shown. The third condition F3 is shown as a comparative example. The feed amount under the third condition F3 is the same as the maximum feed amount under the second condition F2, and is kept constant from the machining start point SP to the machining end point EP. If the surface roughness of the machined surface is less than or equal to the threshold value S shown by the broken line in FIG. 8, the workpiece WK is determined to be a good product, and if it exceeds the threshold value S, the workpiece WK is determined to be a defective product. Ru. When processed under the first condition F1 or when processed under the second condition F2, the surface roughness is equal to or less than the threshold value S in all sections. When processed under the third condition F3, there is a section where the surface roughness exceeds the threshold value.

In the machine tool 11 of the present embodiment described above, the machining condition setting unit 120 performs machining using a machining condition selection map that represents the relationship between the cutting conditions at the cutting position and the predicted value of vibration amplitude in the machining condition setting process. Set conditions. Therefore, the operator can set practical machining conditions suitable for suppressing chatter vibration without trial and error. Therefore, even if it is difficult to install or change the support member 48, chatter vibration can be suppressed depending on the processing conditions.

In the present embodiment, the machining condition setting unit 120 also sets a first condition in which the feed amount per tooth is kept constant and a per-tooth feed amount during machining so that the machining time is shortened compared to the first condition. One of the second conditions for changing the feed amount selected by the operator is set as the machining condition during the main machining. Therefore, when the first condition is selected, the machining accuracy can be increased, and when the second condition is selected, the machining time can be shortened.

In the present embodiment, the machining condition setting unit 120 also sets the maximum compliance of the workpiece WK calculated using the cutting force frequency analysis results and the vibration frequency analysis results before creating the machining condition selection map. It is determined whether the value exceeds a predetermined threshold, and if it is determined that the maximum compliance value of the workpiece WK does not exceed the predetermined threshold, a machining condition selection map is created. Therefore, machining conditions can be set while the rigidity of the workpiece WK is ensured. Furthermore, when it is determined that the maximum compliance value of the workpiece WK exceeds a predetermined threshold value, the machining condition setting unit 120 obtains a determination result as to whether or not it is possible to take measures to improve workpiece rigidity. , if a determination result is obtained that it is possible to implement measures to improve workpiece rigidity, the measures to improve workpiece rigidity are executed, and then the process returns to the measurement process and it is determined that it is not possible to implement measures to improve workpiece rigidity. If a judgment result is obtained, a machining condition selection map is created as is. Therefore, machining conditions can be set while the lack of rigidity of the workpiece WK is resolved as much as possible. Therefore, chatter vibration can be effectively suppressed.

Further, in the present embodiment, when it is determined that forced chatter vibration has occurred during the second trial machining, the machining condition setting unit 120 displays the forced chatter vibration countermeasure plan KT stored in advance in the memory 102. Display on the device 106. Therefore, by implementing the forced chatter vibration countermeasure plan KT, forced chatter vibration in this machining can be suppressed. Further, even an operator with a low level of skill can easily implement measures against forced chatter vibration by referring to the forced chatter vibration countermeasure plan KT prepared in advance.

In the present embodiment, when it is determined that self-excited chatter vibration has occurred during the second trial machining, the machining condition setting unit 120 selects the self-excited chatter vibration countermeasure plan JT stored in advance in the memory 102. is displayed on the display device 106. Therefore, by implementing the self-excited chatter vibration countermeasure plan JT, self-excited chatter vibration in this machining can be suppressed. Further, even an unskilled worker can easily implement self-excited chatter vibration countermeasures by referring to the self-excited chatter vibration countermeasure plan JT prepared in advance.

B. Other embodiments:
(B1) In the machine tool 11 of the embodiment described above, the machining condition setting unit 120 performs machining that represents the relationship between the cutting position on the workpiece WK, the feed amount per tooth, and the predicted value of the vibration amplitude of the workpiece WK. Create a condition selection map. In contrast, the machining condition setting unit 120 creates, for example, a machining condition selection map that represents the relationship between the cutting position on the workpiece WK, the rotational speed of the cutting tool TL, and the predicted value of the vibration amplitude of the workpiece WK. Alternatively, a machining condition selection map may be created that represents the relationship between the cutting position on the workpiece WK, the depth of cut in the Z-axis direction, and the predicted value of the vibration amplitude of the workpiece WK. A machining condition selection map may be created that represents the relationship between the cutting position, the depth of cut in the radial direction of the cutting tool TL, and the predicted value of the vibration amplitude of the workpiece WK.

(B2) In the machine tool 11 of the embodiment described above, the machining condition setting unit 120 sets the first condition in which the feed rate per tooth is kept constant and the machining time to be shorter than the first condition. A second condition under which the feed amount per tooth is changed during machining is displayed on the display device 106, the operator is made to select one of the first condition and the second condition, and the first condition and the second condition are changed. One of the two conditions selected by the operator is set as the processing condition. In contrast, the machining condition setting unit 120 sets one of the first condition and the second condition as the machining condition without allowing the worker to select either the first condition or the second condition. You may.

(B3) In the machine tool 11 of the embodiment described above, the machining condition setting unit 120 calculates the machining condition using the cutting force frequency analysis results and the vibration frequency analysis results before creating the machining condition selection map. It is determined whether the maximum compliance value of the workpiece WK exceeds a predetermined threshold, and if it is determined that the maximum compliance value of the workpiece WK does not exceed the predetermined threshold, a machining condition selection map is created. . On the other hand, the machining condition setting unit 120 may create the machining condition selection map without determining whether the maximum compliance value of the workpiece WK exceeds a predetermined threshold value.

(B4) In the machine tool 11 of the embodiment described above, the machining condition setting unit 120 obtains the determination result as to whether or not forced chatter vibration has occurred in the second trial machining, and determines whether or not forced chatter vibration has occurred in the second trial machining. If a determination result indicating that the forced chatter vibration has occurred is obtained, the forced chatter vibration countermeasure plan KT is displayed on the display device 106. Further, the machining condition setting unit 120 obtains a determination result as to whether self-excited chatter vibration has occurred in the second trial machining, and has acquired a determination result that self-excited chatter vibration has occurred in the second trial machining. In this case, the self-excited chatter vibration countermeasure plan JT is displayed on the display device 106. On the other hand, the machining condition setting unit 120 compares the determination result of whether or not forced chatter vibration occurred in the second trial machining with the determination result of whether or not self-excited chatter vibration occurred in the second trial machining. It is not necessary to obtain the determination result of at least one of them. Further, the forced chatter vibration countermeasure plan KT and the self-excited chatter vibration countermeasure plan JT do not need to be prepared in advance. In this case, when the machining condition setting unit 120 obtains a determination result that forced chatter vibration or self-excited chatter vibration has occurred in the second trial machining, the machining condition setting unit 120 displays the determination result on the display device 106 and may take measures against forced chatter vibration or self-excited chatter vibration based on its own know-how, for example.

(B5) In the machine tool 11 of the embodiment described above, the machining condition setting unit 120 may determine whether or not it is possible to implement measures to improve workpiece rigidity. For example, the machine tool 11 is provided with a camera that captures images of the workpiece WK and the table 40, and the processing condition setting unit 120 can implement measures to improve workpiece rigidity by analyzing images acquired using the camera. It may be determined whether or not. In this case, it is possible to automate the determination as to whether or not it is possible to take measures to improve the workpiece rigidity, thereby reducing the burden on the worker.

(B6) In the machine tool 11 of the embodiment described above, the machining condition setting unit 120 may determine whether forced chatter vibration or self-excited chatter vibration occurs during the second trial machining. For example, the machine tool 11 is provided with a camera that images the machined surface or a probe that measures the surface roughness of the machined surface, and the processing condition setting unit 120 analyzes the image obtained using the camera. Alternatively, it may be determined whether forced chatter vibration or self-excited chatter vibration has occurred during the second trial machining based on the surface roughness measurement result using the probe.

(B7) In the embodiment described above, the machine tool 11 is a vertical machining center. On the other hand, the machine tool 11 does not have to be a vertical machining center. The machine tool 11 may be, for example, a horizontal machining center or an NC milling machine.

(B8) In the embodiment described above, the machining condition setting section 120 is provided in the control device 100 of the machine tool 11. On the other hand, the processing condition setting unit 120 may be provided on a computer connected to the control device 100 by wired communication or wireless communication, for example. In this case, the computer provided with the machining condition setting section 120 may be referred to as a machining condition setting device.

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary column of the invention may be used to solve some or all of the above-mentioned problems, or to achieve one of the above-mentioned effects. In order to achieve some or all of the above, it is possible to replace or combine them as appropriate. Further, unless the technical feature is described as essential in this specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 11...Machine tool, 20...Bed, 30...Saddle, 40...Table, 45...Clamp, 48...Support member, 49...Fixing member, 50...Column, 60...Spindle device, 65...Spindle, 67...Spindle motor, 69 ...Rotation angle sensor, 70...Cutting force sensor, 80A-80C...Vibration sensor, 100...Control device, 101...CPU, 102...Memory, 103...I/O interface, 104...Internal bus, 105...Input device, 106...Display Apparatus, 110...NC control section, 120...machining condition setting section, EP...machining end point, MP1 to MP3...measuring point, SP...machining start point, TL...cutting tool, WK...workpiece

Claims (7)

A machining condition setting method for setting machining conditions for cutting,
A measurement step of measuring a cutting force applied to the workpiece from the cutting tool and vibrations at a plurality of measurement points of the workpiece while performing a first trial machining on the workpiece with the cutting tool;
a vibration estimation step of estimating the vibration of the workpiece at the cutting position using the measurement results of vibration during the first trial machining at the plurality of measurement points;
a frequency analysis step of performing frequency analysis on the measurement results of the cutting force and the estimation results of the vibration during the first trial processing;
Using the frequency analysis results of the cutting force and the frequency analysis results of the vibration, the relationship between the cutting position on the workpiece, the machining conditions, and the predicted value of the vibration amplitude when performing main machining on the workpiece with a cutting tool. a process of creating a machining condition selection map that represents the machining conditions;
a setting step of setting the machining conditions during the main machining using the machining condition selection map so that the vibration amplitude is equal to or less than a predetermined value;
A processing condition setting method having the following. The processing condition setting method according to claim 1,
Prior to the machining condition selection map creation step, a maximum value of the compliance of the workpiece at the cutting position is determined in advance, which is calculated using the frequency analysis results of the cutting force and the frequency analysis results of the vibration. A machining condition setting method that determines whether or not a threshold value is exceeded, and executes the machining condition selection map creation step when it is determined that the maximum value of compliance of the workpiece does not exceed the threshold value. The processing condition setting method according to claim 2,
If it is determined that the maximum compliance value of the workpiece exceeds the threshold value, obtaining a determination result as to whether it is possible to take measures to improve the rigidity of the workpiece;
If a determination result is obtained that it is possible to execute the countermeasure, after the countermeasure is executed, return to the measurement step,
A machining condition setting method, in which when a determination result indicating that the countermeasure cannot be implemented is obtained, the machining condition selection map creation step is executed. The processing condition setting method according to claim 1,
performing a second trial machining on the workpiece using the cutting tool according to the machining conditions set using the machining condition selection map;
obtaining a determination result as to whether forced chatter vibration of the workpiece occurred during the second trial machining;
A machining condition setting method for implementing a countermeasure plan for suppressing the occurrence of forced chatter vibration when a determination result is obtained that forced chatter vibration of the workpiece has occurred during the second trial machining. The processing condition setting method according to claim 1,
performing a second trial machining on the workpiece using the cutting tool according to the machining conditions set using the machining condition selection map;
obtaining a determination result as to whether self-excited chatter vibration of the workpiece occurred during the second trial machining;
A machining condition setting method that executes a countermeasure plan for suppressing the occurrence of self-excited chatter vibration when a determination result is obtained that self-excited chatter vibration of the workpiece has occurred during the second trial machining. . The processing condition setting method according to claim 1,
The processing conditions are the feed amount per blade of the cutting tool,
In the setting step, a first condition in which the feed amount per tooth is kept constant, and a change in the feed amount per tooth during machining so that the machining time is shorter than in the first condition. A method for setting machining conditions in which the machining conditions for the main machining are set by selecting one of the second conditions. A machine tool that performs cutting on a workpiece using a cutting tool,
comprising a machining condition setting section that sets machining conditions for the cutting process,
The processing condition setting section includes:
While performing a first trial machining on the workpiece with the cutting tool, measuring the cutting force applied to the workpiece from the cutting tool and vibrations at a plurality of measurement points of the workpiece,
Estimating the vibration of the workpiece at the cutting position using the measurement results of vibration during the first trial machining at the plurality of measurement points,
Frequency analysis is performed on the measurement results of the cutting force and the estimation results of the vibration during the first trial processing,
Using the frequency analysis results of the cutting force and the frequency analysis results of the vibration, the relationship between the cutting position on the workpiece, the machining conditions, and the predicted value of the vibration amplitude when performing main machining on the workpiece with a cutting tool. Create a machining condition selection map that shows
using the machining condition selection map to set the machining conditions during the main machining so that the vibration amplitude is equal to or less than a predetermined value;
Machine Tools.

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