JP2021107950A - Numerical control device and control method for numerical control device - Google Patents

Abstract

To provide a numerical control device which accurately detects vibrations of a tool during machining, and a control method for the numerical control device.SOLUTION: A CPU of a numerical control device detects vibrations of a main shaft head supporting a main shaft during processing of a work-piece (S9 to S13). The CPU calculates a frequency characteristic of the vibrations generated in the main shaft head during processing of the work-piece, based on detected results (S17). The CPU reads-out a vibration ratio from a storage device that stores the vibration ratio (S19). The vibration ratio is a ratio of a second characteristic to a third characteristic. The second characteristic is a frequency characteristic of a vibration generated in a tool when the processing ceases and the tool is shaken. The third characteristic is a frequency characteristic of a vibration generated in a main shaft head when the processing ceases and the tool is shaken. The vibration ratio changes according to frequencies. The CPU calculates vibrations of a tool during processing of a work-piece by multiplying a frequency characteristic of vibrations generated in a main shaft head by the read-out vibration ratio (S21).SELECTED DRAWING: Figure 3

Description

The present invention relates to a numerical control device and a control method for the numerical control device.

The machine tool of Patent Document 1 attaches an acceleration sensor to the spindle head and detects the vibration of the spindle head. The machine tool detects the chatter vibration continuously generated between the tool and the work material based on the magnitude of the vibration of the spindle head detected by the acceleration sensor and the number of times the vibration exceeding the threshold value occurs.

Japanese Unexamined Patent Publication No. 2010-23162

In the machine tool of Patent Document 1, since the acceleration pickup detects the vibration of the spindle head, the vibration of the tool is not directly detected. Since chatter vibration occurs between the tool and the work material, the machine tool cannot accurately detect chatter vibration. In a machine tool, since the tool during machining of the work material rotates at high speed, it is difficult to directly measure the vibration of the tool by attaching an acceleration sensor to the tool. When a non-contact sensor is used to detect the vibration of a tool in a non-contact state with the tool, the machine tool changes the measurement position by the non-contact sensor when a tool with different dimensions is attached to the spindle by changing the tool during machining. There is a need. Therefore, the machine tool needs to change the measurement position every time the tool is changed, and it is difficult to directly measure the vibration of the tool.

An object of the present invention is to provide a numerical control device and a control method of the numerical control device that can accurately detect the vibration of a tool during machining.

The numerical control device according to claim 1 is a numerical control device that controls the operation of a machine tool that processes a work by rotating a spindle on which a tool is mounted, and detects vibration of the machine tool during machining of the work. Based on the detection result detected by the detection unit, the calculation unit that calculates the first characteristic, which is the frequency characteristic of the vibration generated in the machine tool during the machining of the work, and the calculation unit that calculates the first characteristic when the operation is stopped. The second characteristic, which is the frequency characteristic of the vibration generated in the tool or the work when the tool or the work is vibrated, and the machine tool when the tool or the work is vibrated when the operation is stopped. The ratio to the third characteristic, which is the frequency characteristic of the generated vibration, and the reading unit that reads out the vibration ratio from the storage unit that stores different vibration ratios according to the frequency, and the first characteristic calculated by the calculation unit. On the other hand, it is characterized by including a vibration calculation unit that calculates the vibration of the tool or the work during machining of the work by multiplying the vibration ratio read by the reading unit.

The numerical control device calculates the vibration of the tool during machining of the workpiece by multiplying the calculated first characteristic by the vibration ratio read from the storage unit. Therefore, the numerical control device can accurately detect the vibration of the tool during machining.

The numerical control device according to claim 2 is based on the output result from the first detection unit that detects the vibration of the tool or the work when the tool or the work is vibrated when the rotation of the spindle is stopped. Output results from the second characteristic calculation unit that calculates the second characteristic and the second detection unit that detects the vibration of the machine tool when the tool or work is vibrated when the rotation of the spindle is stopped. Based on the third characteristic calculation unit that calculates the third characteristic, the second characteristic calculated by the second characteristic calculation unit, and the third characteristic calculated by the third characteristic calculation unit, the vibration ratio It is preferable to include a vibration ratio calculation unit for calculating the vibration ratio and a storage control unit for storing the vibration ratio calculated by the vibration ratio calculation unit in the storage unit. The numerical control device calculates the second characteristic based on the output result from the first detection unit when the rotation of the spindle is stopped. The numerical control device calculates the third characteristic based on the output result from the second detection unit when the rotation of the spindle is stopped. The numerical control device calculates the vibration ratio based on the second characteristic and the third characteristic, and stores the calculated vibration ratio in the storage unit. Therefore, the numerical control device can calculate the vibration of the tool during machining of the work by the vibration ratio stored in the storage unit in advance.

The second characteristic calculation unit and the third characteristic calculation unit of the numerical control device according to claim 3 simultaneously detect the tool or the work by the first detection unit and the second detection unit when the tool or the work is vibrated. Alternatively, the second characteristic and the third characteristic may be calculated respectively based on the output results of the vibration of the work and the vibration of the machine tool. Since the numerical control device calculates the vibration ratio from the second characteristic and the third characteristic based on the output results measured at the same time, the influence of disturbance can be reduced. Therefore, the numerical control device can calculate the vibration of the tool during machining of the workpiece while reducing the influence of disturbance.

In the numerical control device of claim 4, the first detection unit may be a displacement sensor capable of detecting vibration of the tool or the work in a state of non-contact with the tool or the work. The numerical control device can detect the vibration of the tool in a state where it is not in contact with the tool by the displacement sensor.

In the numerical control device of claim 5, the second detection unit may be an acceleration sensor provided on the machine tool and capable of detecting the vibration of the machine tool. The numerical control device can detect the vibration of the machine tool by the acceleration sensor.

In the numerical control device of claim 6, the second detection unit may be an encoder provided in a tool provided in the machine tool or a feed motor for moving the work. The numerical control device can use the detection result of the encoder as information on the vibration of the machine tool.

In the numerical control device of claim 7, it is preferable that the machine tool is provided with a spindle head that supports the spindle, and the vibration of the machine tool is the vibration of the spindle head. Since the position of the spindle head and the tool is close to each other in the numerical control device, the vibration of the tool during machining of the workpiece can be calculated more accurately.

The control method of the numerical control device according to claim 8 is a control method of a numerical control device that controls the operation of a machine tool that rotates a spindle on which a tool is mounted to machine a work. A detection step for detecting the vibration of the machine tool, a calculation step for calculating the first characteristic which is a frequency characteristic of the vibration generated in the machine tool during machining of the machine tool based on the detection result detected by the detection step, and the operation. The second characteristic, which is the frequency characteristic of the vibration generated in the tool or the work when the tool or the work is vibrated, and the tool or the work are vibrated when the operation is stopped. A read-out step of reading out the vibration ratio from a storage unit that stores different vibration ratios according to the frequency, which is a ratio to the third characteristic which is the frequency characteristic of the vibration generated in the machine tool at the time, and the calculation step are calculated. It is characterized by including a vibration calculation step for calculating the vibration of the tool or the work during machining of the work by multiplying the first characteristic obtained by the vibration ratio read by the read step. do. By executing the above steps, the numerical control device can obtain the same effect as the numerical control device according to claim 1.

Schematic side view of machine tool 1. The block diagram which shows the electrical structure of a numerical control device 30 and a machine tool 1. Flow chart of main processing. Flow chart of vibration ratio acquisition process. (A) is a diagram showing the frequency characteristic Fh of the vibration of the spindle head 7, (b) is a diagram showing the frequency characteristic Ft of the vibration of the tool 6, and (c) is a diagram showing the frequency characteristic Fh and the vibration ratio Rx based on the frequency characteristic Ft. Also shows information about vibration in the X-axis direction. (A) shows the frequency characteristic Fhm of the vibration of the spindle head 7 during machining, and (b) is a diagram showing the vibration Vx of the tool 6 during machining, both of which show information on vibration in the X-axis direction. Flow chart of the main processing of the modified example. The flow chart of the vibration ratio calculation process of the modification. (A) is a diagram showing the frequency characteristic Fh of the vibration of the encoder information, (b) is a diagram showing the frequency characteristic Ft of the vibration of the tool 6, and (c) is a diagram showing the frequency characteristic Fh and the vibration ratio Rz based on the frequency characteristic Ft. Both show information vibration information regarding vibration in the Z-axis direction. (A) shows the frequency characteristic Fhm of the vibration of the encoder information at the time of machining, and (b) is the figure which shows the vibration Vz of the tool 6 at the time of machining, both of which show the information about the vibration in the Z-axis direction.

Hereinafter, embodiments of the present invention will be described. In the machine tool 1 shown in FIG. 1, a tool 6 mounted on a spindle 8 performs cutting or the like on a work W fixed with a jig (not shown) on a workbench 50. The horizontal direction, the front-rear direction, and the vertical direction of the machine tool 1 are the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively.

The configuration of the machine tool 1 will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the machine tool 1 includes a base 2, a vertical column 5, a spindle head 7, a spindle 8, a work table 50, an acceleration pickup 18, a tool changing device 9, an operation panel 15 (see FIG. 2), and the like. The base 2 is provided below the machine tool 1. The base 2 is provided with a pedestal portion 3 and a carrier 4 at the rear portion of the upper surface. The pedestal portion 3 is provided with an X-axis moving mechanism (not shown) on the upper surface. The X-axis moving mechanism uses the X-axis motor 53 (see FIG. 2) as a drive source and supports the carrier 4 so as to be movable in the X-axis direction. The carrier 4 includes a Y-axis moving mechanism (not shown) inside. The Y-axis moving mechanism uses the Y-axis motor 54 (see FIG. 2) as a drive source and supports the vertical column 5 so as to be movable in the Y-axis direction. Therefore, the vertical column 5 can move in the biaxial directions of the X-axis and the Y-axis.

The spindle head 7 can move in the Z-axis direction along the front surface of the vertical column 5. The vertical column 5 is provided with a Z-axis moving mechanism (not shown) on the front surface. The Z-axis moving mechanism uses the Z-axis motor 51 (see FIG. 2) as a drive source and supports the spindle head 7 so as to be movable in the Z-axis direction. The spindle 8 extends inside the spindle head 7 in the Z-axis direction. A tool mounting hole (not shown) is provided in the lower part of the spindle 8.

The tool holder (not shown) holds the tool 6. The tool holder (not shown) is mounted in the tool mounting hole while holding the tool 6. The acceleration pickup 18 is attached to the right side of the spindle head 7 and near the tool 6. The acceleration pickup 18 detects the acceleration of the spindle head 7 and converts it into an electric signal. The workbench 50 is provided on the upper surface of the base 2 and below the spindle head 7, and the work W is fixed by a jig fixed to the upper surface.

The tool changing device 9 includes a tool magazine 91 and a magazine motor 55 (see FIG. 2). The tool magazine 91 is arranged in front of the spindle head 7, and is supported on the vertical column 5 by a pair of left and right support members 92 (only the right support member 92 is shown in FIG. 1). The tool magazine 91 holds a plurality of tools (not shown) and positions the tool specified by the NC program at the tool change position. The magazine motor 55 drives the tool magazine 91. The machine tool 1 exchanges the current tool at the tool exchange position with the next tool mounted on the spindle 8 by raising and lowering the spindle head 7.

The operation panel 15 (see FIG. 2) is provided on the outer wall of a cover (not shown) that covers the machine tool 1. The operation panel 15 includes an input unit 16 and a display unit 17. The input unit 16 receives inputs such as various information and operation instructions, and outputs them to the numerical control device 30 described later. The display unit 17 displays various screens based on a command from the numerical control device 30 described later.

The electrical configuration of the numerical control device 30 and the machine tool 1 will be described with reference to FIG. The numerical control device 30 and the machine tool 1 include a CPU 31, a ROM 32, a RAM 33, a storage device 34, an input / output unit 35, drive circuits 51A to 55A, and the like. The CPU 31 controls the numerical control device 30 in an integrated manner. The ROM 32 stores various programs including the main program. The main program executes the main processing described later. The RAM 33 temporarily stores various types of information. The storage device 34 is non-volatile and stores various information including an NC program and vibration ratios Rx, Ry, Rz and the like described later. In addition to the NC program input by the operator in the input unit 16 of the operation panel 15, the CPU 31 can store the NC program or the like read by the external input in the storage device 34.

The drive circuit 51A is connected to the Z-axis motor 51 and the encoder 51B. The drive circuit 52A is connected to the spindle motor 52 and the encoder 52B. The drive circuit 53A is connected to the X-axis motor 53 and the encoder 53B. The drive circuit 54A is connected to the Y-axis motor 54 and the encoder 54B. The drive circuit 55A is connected to the magazine motor 55 and the encoder 55B. The Z-axis motor 51, the spindle motor 52, the X-axis motor 53, the Y-axis motor 54, and the magazine motor 55 are all servo motors. The drive circuits 51A to 55A receive commands from the CPU 31 and output drive currents to the corresponding motors 51 to 55, respectively. The drive circuits 51A to 55A receive encoder information from the encoders 51B to 55B and control the position and speed.

The operation panel 15, the acceleration pickup 18, the impulse hammer 11, and the displacement sensor 29 are connected to the input / output unit 35. The acceleration pickup 18 outputs the output result of the measured acceleration to the CPU 31 via the input / output unit 35. The impulse hammer 11 is used when the tool 6 is vibrated in the vibration ratio acquisition process described later. The impulse hammer 11 has a built-in force sensor that detects the applied force, converts the force applied to the tool 6 into an electric signal, and outputs the force to the CPU 31. The output value of the force sensor is used in the calculation of the frequency characteristics Fh and Ft shown in FIGS. 5A and 5B, which will be described later. The displacement sensor 29 is arranged on the workbench 50 in the vibration ratio acquisition process described later. The displacement sensor 29 is a well-known laser displacement meter, and can detect the vibration Vx of the tool 6 in a state of non-contact with the tool 6. The displacement sensor 29 outputs information regarding the vibration of the tool 6 to the CPU 31 via the input / output unit 35.

The main processing will be described with reference to FIGS. 3 to 6. When the power of the machine tool 1 is turned on, the CPU 31 reads the main program stored in the ROM 32 and executes the main process (see FIG. 3). The CPU 31 determines whether or not the NC program has been accepted (S1). When the NC program is not accepted (S1: NO), the CPU 31 returns to S1 and waits.

The operator operates the operation panel 15 and inputs the program number of the NC program that executes the machining of the work W. The CPU 31 reads the NC program corresponding to the input program number from the storage device 34 and displays it on the display unit 17. The NC program is executed by the operation of the input unit 16 of the operator. At this time, the CPU 31 determines that the NC program has been accepted (S1: YES), and determines whether the vibration ratios Rx, Ry, and Rz, which will be described later, are stored in the storage device 34 (S3). When the vibration ratios Rx, Ry, and Rz are not stored in the storage device 34 (S3: NO), the CPU 31 executes the vibration ratio acquisition process (S5).

The vibration ratio acquisition process will be described with reference to FIG. The CPU 31 stops the rotation of the spindle 8 (S101). A guidance screen for encouraging the operator to vibrate the tool 6 is displayed (S103). For example, the CPU 31 displays a guidance screen on the display unit 17 with a message such as "Please hit the tool in the X-axis direction with an impulse hammer". The operator hits the tool 6 in the X-axis direction with the impulse hammer 11 (not shown) according to the guidance screen.

The CPU 31 determines whether the tool 6 has been vibrated (S105). The CPU 31 detects the electric signal of the force output by the impulse hammer 11, and determines that the tool 6 has been vibrated when the magnitude of the electric signal exceeds a predetermined threshold value. When there is no vibration in the tool 6 (S105: NO), the CPU 31 returns to S103 and stands by with the guidance screen displayed. When the tool 6 is vibrated (S105: YES), the CPU 31 acquires an input waveform (not shown) of the force applied to the tool 6 from the impulse hammer 11 (S107). The CPU 31 stores the acquired input waveform in the storage device 34.

The CPU 31 acquires an output result (not shown) when the tool 6 is hit with the impulse hammer 11 from the acceleration pickup 18 (S109). The CPU 31 stores the output result from the acceleration pickup 18 in the storage device 34 as information regarding the vibration of the spindle head 7. The CPU 31 acquires an output result (not shown) when the tool 6 is hit with the impulse hammer 11 from the displacement sensor 29 (S111). The CPU 31 stores the output result from the displacement sensor 29 in the storage device 34 as information regarding the vibration of the tool 6.

The CPU 31 calculates the frequency characteristic Fh related to the vibration of the spindle head 7 (S113). The frequency characteristic Fh is a frequency characteristic of vibration generated in the spindle head 7 when the tool 6 is vibrated when the rotation of the spindle 8 is stopped, and is a response function indicating the magnitude of vibration for each frequency. The frequency characteristic Fh is calculated based on the input waveform of the vibration applied to the tool 6 by the impulse hammer 11 acquired in the process of S107 and the output result regarding the vibration of the spindle head 7 acquired in the process of S109. FIG. 5A shows the frequency characteristic Fh of the vibration of the spindle head 7 when the tool 6 is vibrated. The horizontal axis represents frequency (Hz), and the vertical axis represents spindle head compliance (μm / N). The spindle head compliance indicates the magnitude of vibration of the spindle head 7 when a force of 1N is applied. The vibrated tool 6 is a φ63 five-flute face mill. Regarding the frequency characteristic Fh of the vibration generated in the spindle head 7, for example, vibration peaks occur in the vicinity of 0 to 200 Hz, 480 Hz, and 1000 Hz.

The CPU 31 calculates the frequency characteristic Ft related to the vibration of the tool 6 (S115). The frequency characteristic Ft is the frequency characteristic of the vibration generated in the tool 6 when the tool 6 is vibrated when the rotation of the spindle 8 is stopped, and is a response function indicating the magnitude of the vibration for each frequency. The frequency characteristic Ft is calculated based on the input waveform of the vibration applied to the tool 6 by the impulse hammer 11 acquired in the process of S107 and the output result of the vibration of the tool 6 acquired in the process of S111. FIG. 5B shows the frequency characteristic Fh of the vibration of the tool 6 when the tool 6 is vibrated. The horizontal axis represents frequency (Hz) and the vertical axis represents tool compliance (μm / N). Tool compliance indicates the magnitude of vibration of the tool 6 when a force of 1N is applied. As shown in FIG. 5 (b), it can be seen that the vibration peak occurs in the vicinity of, for example, 480 Hz, 1000 Hz, 1200 Hz, and 1500 Hz.

The CPU 31 calculates a different vibration ratio Rx depending on the frequency (S117). The vibration ratio Rx is the ratio of the frequency characteristic Fh to the frequency characteristic Ft in the X-axis direction for each frequency. FIG. 5C shows the frequency characteristics of the vibration ratio Rx. The horizontal axis shows the frequency (Hz), and the vertical axis shows the vibration ratio. As shown in FIG. 5C, the vibration ratio Rx is high in the vicinity of 50 Hz, 250 Hz, 300 Hz, 750 Hz, 900 Hz, 1100 Hz, 1600 Hz to 2000 Hz. The vibration ratio Rx changes for each frequency.

The CPU 31 stores the vibration ratio Rx calculated in S117 in the storage device 34 (S119). The CPU 31 determines whether the vibration ratios Rx, Ry, and Rz are all stored in the storage device 34 (S121). The vibration ratio Ry is the ratio of the frequency characteristic Fh to the frequency characteristic Ft in the Y-axis direction for each frequency. The vibration ratio Rz is the ratio of the frequency characteristic Fh to the frequency characteristic Ft in the Z-axis direction for each frequency. Since the storage device 34 does not store the vibration ratios Ry and Rz (S121: NO), the CPU 31 returns to S103 and displays a guidance screen prompting vibration in the Y-axis direction on the display unit 17. The operator vibrates the tool 6 in the Y-axis direction with the impulse hammer 11. The CPU 31 executes the above processes S105 to S119, calculates the vibration ratio Ry, and stores it in the storage device 34.

Since the vibration ratio Rz is not stored in the storage device 34 (S121: NO), the CPU 31 returns to S103 and displays a guidance screen prompting vibration in the Z-axis direction on the display unit 17. The operator vibrates the tool 6 in the Z-axis direction with the impulse hammer 11. The CPU 31 executes the above processes S105 to S119, calculates the vibration ratio Rz, and stores it in the storage device 34. When the storage device 34 stores all the vibration ratios Rx, Ry, and Rz (S121: YES), the CPU 31 returns the process to the main process S7.

The CPU 31 starts machining of the work W based on the NC program (S7). In this embodiment, for example, processing is executed under the following conditions.
-Material of work W: JIS S50C
-Spindle rotation speed: 800min-1
・ Feed speed: 400 mm / min

The CPU 31 starts the vibration measurement of the spindle head 7 by the acceleration pickup 18 during the machining of the work W (S9). The start time of vibration measurement by the acceleration pickup 18 is specified in advance by the operator. The CPU 31 determines whether a predetermined time has elapsed since the vibration measurement of the spindle head 7 was started (S11). When the predetermined time has not elapsed (S11: NO), the CPU 31 returns to S11 and continues to acquire the output result from the acceleration pickup 18.

When the predetermined time has elapsed (S11: YES), the CPU 31 stops the vibration measurement of the spindle head 7 (S13). The CPU 31 finishes processing the work W (S15). The CPU 31 calculates the frequency characteristic Fhm of the vibration generated in the spindle head 7 during the machining of the work W based on the output result detected by the acceleration pickup 18 in the processes of S9 to 13 (S17). The frequency characteristic Fhm is a Fourier transform of the output result from the acceleration pickup 18.

FIG. 6A shows the frequency characteristic Fhm of the vibration generated in the spindle head 7 during the machining of the work W. The horizontal axis represents the frequency, and the vertical axis represents the displacement (μm) of the spindle head 7. The displacement of the spindle head 7 indicates the magnitude of vibration of the spindle head 7. In the frequency characteristic Fhm, vibration peaks occur in the vicinity of 90 Hz and 180 Hz, and the spindle head 7 does not appear to vibrate in the region of 500 Hz to 1000 Hz.

The CPU 31 reads out the vibration ratios Rx, Ry, and Rz from the storage device 34 (S19). The CPU 31 calculates the vibrations Vx, Vy, and Vz of the tool 6 during machining of the work W, respectively (S21). Vibration Vx is vibration in the X-axis direction, vibration Vy is vibration in the Y-axis direction, and vibration Vz is vibration in the Z-axis direction. The CPU 31 calculates the vibration Vx of the tool 6 by multiplying the frequency characteristic Fhm by the vibration ratio Rx. The CPU 31 calculates the vibration Vy and the vibration Vz of the tool 6 in the same manner as the vibration Vx of the tool 6.

The CPU 31 displays, for example, the calculated vibration Vx of the tool 6 on the display unit 17 (S23). Regarding the display of the vibration Vy and Vz on the display unit 17, the CPU 31 can switch the display screen of the display unit 17 by operating the operation panel 15 of the operator.

FIG. 6B shows the frequency characteristics of the vibration Vx generated in the tool 6 during the machining of the work W. The horizontal axis represents the frequency, and the vertical axis represents the displacement (μm) of the tool 6. The displacement of the tool 6 indicates the magnitude of the vibration of the tool 6. As shown in FIG. 6B, it can be seen that the vibration Vx of the tool 6 has vibration peaks at 90 Hz and 180 Hz, similar to the frequency characteristic Fhm of the vibration of the spindle head 7. Further, it can be seen that the vibration Vx of the tool 6 has a vibration peak in the region of 250 Hz and 320 Hz to 450 Hz. Therefore, in FIG. 6A, it can be seen that a vibration peak that could not be observed occurs in the tool 6 near 400 Hz. Further, it can be seen that the vibration Vx can observe the vibration peaks in the vicinity of 780 Hz and 950 Hz. That is, it can be seen that vibrations that could not be observed in the frequency range of 500 to 1000 Hz in FIG. 6A are generated in the tool 6. Therefore, the CPU 31 can more accurately detect the vibration of the tool 6 that could not be observed only by the vibration of the spindle head 7. Therefore, the operator can recognize the generated vibration and can take measures such as changing the rotation frequency of the spindle 8 when a high-intensity vibration peak is generated. The CPU 31 can specify a vibration mode such as a reproduction chatter vibration by calculating the vibration Vx in the X-axis, Y-axis, and Z-axis directions. The CPU 31 ends this process.

As described above, the CPU 31 of the numerical control device 30 detects the vibration of the spindle head 7 that supports the spindle 8 during the machining of the work W. The CPU 31 calculates the frequency characteristic Fhm of the vibration generated in the spindle head 7 during the machining of the work W based on the output results detected in the processes of S9 to S13. The CPU 31 reads, for example, the vibration ratio Rx from the storage device 34 that stores the vibration ratios Rx, Ry, and Rz. The CPU 31 calculates the vibration Vx of the tool 6 during machining of the work W by multiplying the frequency characteristic Fhm calculated in the process of S17 by the vibration ratio Rx read in the process of S19. Therefore, the CPU 31 can accurately detect the vibration Vx of the tool 6 during machining, and can more accurately detect the vibration of the tool 6 which could not be observed only by the vibration of the spindle head 7.

The CPU 31 calculates the frequency characteristic Fh based on the output result from the acceleration pickup 18 that detects the vibration of the spindle head 7 when the tool 6 is vibrated when the rotation of the spindle 8 is stopped, for example. The CPU 31 calculates the frequency characteristic Ft based on the output result from the displacement sensor 29 that detects the vibration of the tool 6 when the tool 6 is vibrated when the rotation of the spindle 8 is stopped. The CPU 31 calculates the vibration ratio Rx based on the frequency characteristic Fh calculated by the processing of S113 and the frequency characteristic Ft calculated by the processing of S115. The CPU 31 stores the vibration ratio Rx calculated by the process of S117 in the storage device 34. Therefore, the CPU 31 can calculate the vibration Vx of the tool 6 during the machining of the work W by the vibration ratio Rx stored in the storage device 34 in advance.

The CPU 31 calculates the frequency characteristic Fh and the frequency characteristic Ft based on the output results of the vibration of the tool 6 and the vibration of the spindle head 7 simultaneously detected by the displacement sensor 29 and the acceleration pickup 18 when the tool 6 is vibrated. do. Since the CPU 31 calculates the vibration ratio Rx from the frequency characteristic Fh and the frequency characteristic Ft based on the output results measured at the same time, the influence of disturbance can be reduced. Therefore, the CPU 31 can calculate, for example, the vibration Vx of the tool 6 during machining of the work W while reducing the influence of disturbance.

The displacement sensor 29 is a sensor capable of detecting the vibration of the tool 6 in a state of non-contact with the tool 6. The displacement sensor 29 allows the CPU 31 to detect the vibration of the tool 6 in a state of non-contact with the tool 6.

The acceleration pickup 18 is provided on the spindle head 7 and can detect the vibration of the spindle head 7. The CPU 31 can directly detect the vibration of the spindle head 7 by the acceleration pickup 18.

The spindle head 7 rotatably supports the spindle 8. Since the CPU 31 has the spindle head 7 and the tool 6 held by the spindle 8 close to each other, the vibration Vx of the tool 6 at the time of machining the work W can be calculated more accurately.

The present invention is not limited to the above embodiment and can be modified in various ways. The machine tool 1 of the above embodiment detects the vibration of the spindle head 7 by the acceleration pickup 18, but the machine tool 1 in the modified example uses the encoder information of the encoders 51B, 53B, 54B to detect the vibration of the spindle head 7. To detect. Therefore, the machine tool 1 of the modified example does not need to be provided with the acceleration pickup 18. Hereinafter, the calculation of the vibration Vx of the tool 6 of the machine tool 1 using the encoders 51B, 53B, and 54B in the modified example will be described with reference to FIGS. 7 to 10. The description of the same configuration as that of the above embodiment will be omitted, and the different configuration will be described in detail. The main process of the modified example (see FIG. 7) is different in that the CPU 31 executes the processes of S10, S14, and S18 instead of the processes of S9, S13, and S17. Further, in the vibration ratio acquisition process (see FIG. 8) of the modified example, the CPU 31 executes the processes of S110 and S114 instead of the processes of S109 and S113.

The main processing of the modified example will be described with reference to FIGS. 7 to 10. When the power of the machine tool 1 is turned on, the CPU 31 executes the main process shown in FIG. 7 (see FIG. 7). When the CPU 31 accepts the NC program (S1: YES) and determines that the vibration ratios Rx, Ry, and Rz are not stored in the storage device 34 (S3: NO), the CPU 31 executes the vibration ratio acquisition process of the modified example (S3: NO). S5).

In the vibration ratio acquisition process of the modified example, the operator hits the tool 6 from the X-axis direction with the impulse hammer 11 according to the display on the guidance screen. When the tool 6 is vibrated in the X-axis direction by the impulse hammer 11, the CPU 31 vibrates the X-axis motor 53, the Y-axis motor 54, and the Z-axis so that the position of the spindle 8 vibrating due to the vibration returns to the position before the vibration. Drives the motor 51. Therefore, when the tool 6 is hit in the X-axis direction with the impulse hammer 11, the encoder information output by the encoders 51B, 53B, and 54B changes. At this time, the CPU 31 acquires the encoder information of the encoders 51B, 53B, 54B (S110). At this time, the CPU 31 stores the acquired encoder information in the storage device 34 as vibration information of the spindle head 7.

The CPU 31 calculates the frequency characteristic Fh based on the input waveform acquired in S107 and the encoder information acquired in S110 in the same manner as in the above embodiment (S114). The CPU 31 acquires the vibration ratio Rx of the frequency characteristic Fh calculated based on the encoder information and the frequency characteristic Ft calculated in the same manner as in the above embodiment (S117). The CPU 31 stores the calculated vibration ratio Rx in the storage device 34 (S119). When the vibration ratio Ry is not stored in the storage device 34 (S121: NO), the CPU 31 returns to the process of S103, displays a guidance screen, and prompts the operator to vibrate the tool 6 in the Y-axis direction. .. The CPU 31 repeats the processes of S103 to S119 to calculate the vibration ratio Ry (not shown) and stores it in the storage device 34. When the vibration ratio Rz is not stored in the storage device 34 (S121: NO), the CPU 31 returns to the process of S103, displays a guidance screen, and prompts the operator to vibrate the tool 6 in the Z-axis direction. .. The CPU 31 repeats the processes of S103 to S119 to calculate the frequency characteristic Fh (see FIG. 9A), the frequency characteristic Ft (see FIG. 9B), and the vibration ratio Rz (see FIG. 9C). , Stored in the storage device 34.

As shown in FIG. 9A, the frequency characteristic Fh is the frequency characteristic of the vibration of the encoder information of the encoder 51B when the tool 6 is vibrated in the Z-axis direction when the rotation of the spindle 8 is stopped, and is for each frequency. It is a response function that indicates the magnitude of the vibration of. FIG. 9A shows the frequency characteristic Fh when the tool 6 is vibrated in the Z-axis direction. The horizontal axis represents frequency (Hz) and the vertical axis represents motor compliance (μm / N). Motor compliance indicates the magnitude of vibration of encoder information when a force of 1N is applied. The frequency characteristic Fh of the vibration generated in the spindle head 7 vibrates in the region of 0 to 150 Hz, for example. The frequency characteristic Ft shown in FIG. 9B and the vibration ratio Rz in FIG. 9C are the results of calculations in the same manner as in the above embodiment.

Since all the vibration ratios Rx, Ry, and Rz are stored (S121: YES), the CPU 31 returns the process to the main process (see FIG. 7) and executes the process of S7.

The CPU 31 acquires the encoder information of the encoders 51B, 53B, 54B during the processing of the work W (S10). At this time, the CPU 31 stores the encoder information in the storage device 34 as information regarding the vibration of the spindle head 7. The CPU 31 acquires the frequency characteristic Fhm by Fourier transforming the encoder information of the encoder 51B, for example (S18). The frequency characteristics Fhm of the vibrations Vx and Vy in the X-axis direction and the Y-axis direction are also calculated based on the encoder information of the encoders 53B and 54B, respectively.

FIG. 10A shows the frequency characteristic Fhm of the vibration of the encoder information of the Z-axis motor 51 during the machining of the work W. The horizontal axis represents the frequency, and the vertical axis represents the displacement (μm) of the encoder information of the Z-axis motor 51. The displacement of the Z-axis motor 51 indicates the magnitude of vibration of the encoder information of the encoder 51b. In the frequency characteristic Fhm, vibration peaks occur in the vicinity of 15 Hz, 65 Hz, 135 Hz, 175 Hz, 200 Hz, and 240 Hz.

The CPU 31 calculates the vibration Vx of the tool 6 by multiplying the calculated frequency characteristic Fhm by the read vibration ratio Rx for each frequency (S21) and displays it on the display unit 17 (S23). At this time, the CPU 31 also calculates the vibrations Vy and Vz of the tool 6 in the Y-axis direction and the Z-axis direction in the same manner (S21) and displays them on the display unit 17 (S23).

FIG. 10B shows the frequency characteristic Fhm of the vibration Vz in the Z-axis direction generated in the tool 6 during the machining of the work W. The horizontal axis represents the frequency, and the vertical axis represents the displacement (μm) of the tool 6. The displacement of the tool 6 indicates the magnitude of the vibration of the tool 6. As shown in FIG. 10B, the vibration Vz of the tool 6 in the Z-axis direction is 30 Hz, 55 Hz, 110, 120 Hz, 145 Hz, 175 Hz, 230 in addition to the vibration peaks near 15 Hz, 65 Hz, 135, 175 Hz, and 200 Hz. It can be seen that vibration is also occurring in the vicinity. The CPU 31 ends the main processing of the modified example.

The machine tool 1 can be further changed as follows. The machine tool 1 is a vertical machine tool in which the spindle 8 is parallel to the Z-axis direction, but it may be a horizontal machine tool in which the spindle extends in the horizontal direction. In the machine tool 1, the spindle 8 on which the tool 6 is mounted is movable in the Z-axis direction, and the vertical column 5 is movable in the X-axis and Y-axis directions (hereinafter, referred to as a column traverse type machine tool). The spindle 8 is driven in the Z-axis direction, and the workbench 50 may be movable in the X-axis and the Y-axis (hereinafter, referred to as a table traverse type machine tool). Further, in the machine tool 1, although the tool 6 is vibrated, the work W may be vibrated to calculate the vibrations Vx, Vy, and Vz of the work W. As for the calculation of the vibration of the tool 6 and the calculation of the vibration of the work W, only one may be calculated or both may be calculated as necessary. Hereinafter, the calculation of the vibration of the tool 6 or the work W in the table traverse type machine tool will be described in detail.

In a table traverse type machine tool, it is assumed that the acceleration pickup 18 is attached to the work table 50 and the vibration of the work W is calculated. At this time, in the vibration ratio acquisition process, the displacement sensor 29 is arranged on the spindle head 7 to measure the vibration of the work W. That is, the displacement sensor 29 is arranged at a place different from the part where the vibration is to be calculated. Therefore, the machine tool 1 improves the accuracy of the detection results of the acceleration pickup 18 and the displacement sensor 29.

The machine tool 1 of the above modification is a column traverse type, and when the vibration of the tool 6 is calculated from the encoder information of the X-axis motor 53, the Y-axis motor 54, and the Z-axis motor 51, the column traverse type machine tool 1 is , X, Y, Z-axis direction vibration Vx, Vy, Vz could be calculated. On the other hand, when the machine tool 1 is a table traverse type and the vibration of the tool 6 is calculated from the encoder information of the X-axis motor 53, the Y-axis motor 54, and the Z-axis motor 51, the vibration Vz in the Z-axis direction is calculated accurately. can. It should be noted that the calculation of the vibration Vx and Vy in the X-axis direction and the Y-axis direction can be performed although the accuracy is slightly reduced.

The machine tool 1 detects the vibration of the spindle head 7 by the acceleration pickup 18, but the present invention is not limited to this, and other sensors may be used. For example, the machine tool 1 may use a displacement sensor instead of the acceleration pickup 18. The machine tool 1 detects the vibration of the tool 6 by the displacement sensor 29 when the tool 6 is vibrated, but another sensor may be used. For example, the machine tool 1 may use an acceleration pickup instead of the displacement sensor 29. The displacement sensor 29 is a laser displacement sensor, but the displacement sensor 29 is not limited to this, and a capacitance type displacement sensor, an eddy current type displacement sensor, or the like may be used. The acceleration pickup 18 is provided on the spindle head 7, but is not limited to this, and may be provided on any part of the machine tool 1 that vibrates when the tool 6 is vibrated. Even in such a case, the numerical control device 30 can accurately calculate the vibrations Vx, Vy, and Vz of the tool 6.

The CPU 31 of the machine tool 1 simultaneously detects the output results from the displacement sensor 29 and the acceleration pickup 18 in the vibration ratio acquisition process, but it is not necessary to detect them at the same time. For example, when the tool 6 is vibrated by the impulse hammer 11, only the output result of the displacement sensor 29 may be acquired first, and then when the tool 6 is vibrated again by the impulse hammer 11, the output result of the acceleration pickup 18 may be acquired. .. Even in such a case, the frequency characteristic Fh is a response function indicating the input / output relationship between the input waveform by the impulse hammer 11 and the vibration output result of the acceleration pickup 18, and the frequency characteristic Ft is the input waveform by the impulse hammer 11. It is a response function showing the relationship between the input and output with the output result of the vibration of the displacement sensor 29. Therefore, the CPU 31 can acquire the same frequency characteristics as the frequency characteristics Fh and Ft when the output results are acquired at the same time, respectively. The CPU 31 calculated a response function based on the detection results of the impulse hammer 11 and the acceleration pickup 18 and a response function based on the detection results of the impulse hammer 11 and the displacement sensor 29, but calculated each response function by an external device. May be good.

In the processing of S9, S11, S13 and the processing of S10, S11, S14, the CPU 31 acquired the vibration output result for a predetermined time, but is not limited to this, and for example, the vibration output result from the cutting start to the cutting end is acquired. You may. At this time, the CPU 31 may specify a section of the vibration output result specified by the operator. Therefore, the CPU 31 may execute the calculation of the vibration Vx, Vy, Vz based on the output result of the vibration in the section specified by the operator. The CPU 31 waits for the completion of machining of the work W and calculates and displays the vibrations Vx, Vy, and Vz of the tool 6. For example, the CPU 31 calculates and displays the vibrations Vx, Vy, and Vz of the tool 6 during machining of the work W. May be displayed.

The machine tool has executed the calculation of the vibration ratios Rx, Ry, and Rz using the tool 6, but the present invention is not limited to this, and the vibration ratios Rx, Ry, and Rz may be acquired for each of the other different tools. As a result, the CPU 31 can more accurately calculate the vibration of the tool during machining of the work W in accordance with the tool for changing the tool. Although the CPU 31 has acquired all the data, it suffices to acquire at least one of the vibration ratios Rx, Ry, and Rz in the X-axis, Y-axis, and Z-axis directions. At this time, the CPU 31 may calculate the vibration of the tool 6 only in the acquired direction.

The CPU 31 that executes the processes of S9 to S13 and S10 to S14 of FIGS. 3 and 7 is an example of the detection unit of the present invention. The CPU 31 that executes the processes of S17 and S18 is an example of the arithmetic unit of the present invention. The CPU 31 that executes the process of S19 is an example of the reading unit of the present invention. The CPU 31 that executes the process of S21 is an example of the vibration calculation unit of the present invention. The CPU 31 that executes the processes of S113 and S114 of FIGS. 4 and 8 is an example of the third characteristic calculation unit of the present invention. The CPU 31 that executes the process of S115 is an example of the second characteristic calculation unit of the present invention. The CPU 31 that executes the process of S117 is an example of the vibration ratio calculation unit of the present invention. The CPU 31 that executes the process of S119 is an example of the storage control unit of the present invention.

The frequency characteristic Fhm is an example of the first characteristic of the present invention. The frequency characteristic Fh is an example of the second characteristic of the present invention. The frequency characteristic Ft is an example of the third characteristic of the present invention. The acceleration pickup 18 is an example of the acceleration sensor of the present invention. The storage device 34 is an example of the storage unit of the present invention. The displacement sensor 29 is an example of the first detection unit of the present invention. The acceleration pickup 18, encoders 51B, 53B, and 54B are examples of the second detection unit of the present invention. The X-axis motor 53, the Y-axis motor 54, and the Z-axis motor 51 are examples of the feed motor of the present invention.

1 Machine tool 6 Tools 7 Spindle head 8 Spindle 18 Acceleration pickup 29 Displacement sensor 30 Numerical control device 31 CPU
34 Storage device 51 Z-axis motor 53 X-axis motor 54 Y-axis motor W work 51B, 53B, 54B Encoder Fh, Ft, Fhm Frequency characteristics Rx, Ry, Rz Vibration ratio Vx, Vy, Vz Vibration

Claims (8)

In a numerical control device that controls the operation of a machine tool that processes a workpiece by rotating the spindle on which a tool is mounted.
A detection unit that detects vibration of the machine tool during machining of the work, and
Based on the detection result detected by the detection unit, a calculation unit that calculates the first characteristic, which is the frequency characteristic of the vibration generated in the machine tool during machining of the work, and the calculation unit.
When the operation is stopped, the second characteristic which is the frequency characteristic of the vibration generated in the tool or the work when the tool or the work is vibrated, and when the operation is stopped, the tool or the work is added. A reading unit that reads out the vibration ratio from a storage unit that stores different vibration ratios according to the frequency, which is a ratio to the third characteristic that is the frequency characteristic of the vibration generated in the machine tool when shaken.
A vibration calculation unit that calculates the vibration of the tool or the work during machining of the work is provided by multiplying the first characteristic calculated by the calculation unit by the vibration ratio read by the reading unit. A numerical control device characterized by the fact that. The second characteristic is calculated based on the output result from the first detection unit that detects the vibration of the tool or the work when the tool or the work is vibrated when the rotation of the spindle is stopped. Characteristic calculation unit and
Third characteristic calculation for calculating the third characteristic based on the output result from the second detection unit that detects the vibration of the machine tool when the tool or the work is vibrated when the rotation of the spindle is stopped. Department and
A vibration ratio calculation unit that calculates the vibration ratio based on the second characteristic calculated by the second characteristic calculation unit and the third characteristic calculated by the third characteristic calculation unit.
The numerical control device according to claim 1, further comprising a storage control unit that stores the vibration ratio calculated by the vibration ratio calculation unit in the storage unit. When the tool or the work is vibrated, the second characteristic calculation unit and the third characteristic calculation unit simultaneously detect the vibration of the tool or the work by the first detection unit and the second detection unit, and the vibration of the work. The numerical control device according to claim 2, wherein the second characteristic and the third characteristic are calculated based on the output results of the vibration of the machine tool, respectively. The numerical control according to claim 2 or 3, wherein the first detection unit is a displacement sensor capable of detecting vibration of the tool or the work in a state of non-contact with the tool or the work. Device. The numerical control device according to any one of claims 2 to 4, wherein the second detection unit is an acceleration sensor provided on the machine tool and capable of detecting vibration of the machine tool. The numerical control device according to any one of claims 2 to 4, wherein the second detection unit is an encoder provided in the tool provided in the machine tool or a feed motor for moving the work. The numerical control device according to any one of claims 1 to 6, wherein the machine tool is provided with a spindle head that supports the spindle, and the vibration of the machine tool is the vibration of the spindle head. In the control method of the numerical control device that controls the operation of the machine tool that processes the workpiece by rotating the spindle on which the tool is mounted.
A detection step for detecting vibration of the machine tool during machining of the work, and
Based on the detection result detected by the detection step, the calculation step of calculating the first characteristic which is the frequency characteristic of the vibration generated in the machine tool during the machining of the work, and the calculation step.
When the operation is stopped, the second characteristic which is the frequency characteristic of the vibration generated in the tool or the work when the tool or the work is vibrated, and when the operation is stopped, the tool or the work is added. A read-out step of reading out the vibration ratio from a storage unit that stores different vibration ratios according to the frequency, which is a ratio to the third characteristic which is the frequency characteristic of the vibration generated in the machine tool when shaken.
A vibration calculation step for calculating the vibration of the tool or the work during machining of the work is provided by multiplying the first characteristic calculated by the calculation step by the vibration ratio read by the read step. A control method for a numerical control device, which is characterized in that.

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