Machine tool and shaft alignment method of machine tool

Abstract

Axis alignment of a machine tool is performed more simply. Provided is a machine tool. A second spindle that holds the other end side of the workpiece; and a sensor that detects a physical quantity related to vibration when the first spindle and the second spindle rotate synchronously in a state in which the first spindle and the second spindle hold the workpiece. And a control unit that performs axis alignment of the first main axis and the second main axis in accordance with the physical quantity.

Description

Technical Field

[0001] The present disclosure relates to a machine tool and an axis alignment method of the machine tool. Background Art

[0002] Machine tools for machining workpieces (workpieces) by tools are known, such as CNC milling machines, machining centers, etc. Such machine tools may have jaws that can perform a tightening action to mount the workpiece or tool, or may have a spindle that can rotate while the workpiece or tool is mounted using the jaws, etc. If an abnormality such as chip jamming occurs in the mounting portion of such a workpiece or tool, the machining accuracy of the workpiece may be adversely affected.

[0003] As a conventional technology for solving such a problem, for example, there is known a technology described in Patent Document 1. Patent Document 1 describes a machine tool that detects abnormality based on data related to vibration of a jaw that can perform a tightening operation to attach a workpiece or a tool.

[0004] In addition, a machine tool is known that has a main spindle and a back spindle on the same axis, and uses claws of the main spindle and claws of the back spindle to grip one end and the other end of a workpiece. In such a machine tool, there may be an axis offset (also called axis offset or eccentricity) between the main spindle and the back spindle.

[0005] As a prior art for dealing with this problem, there is known a technique described in, for example, Patent Document 2. Patent Document 2 describes using an outer diameter measuring instrument to measure the axis of a bar held by a spindle and the axis of a bar held on a back spindle in a state facing the spindle, and correcting the offset of the axis of the back spindle relative to the axis of the spindle based on the measurement data of the two measurements.

[0006] (Prior art literature)

[0007] (Patent Document)

[0008] Patent Document 1: Japanese Patent Application Publication No. 2020-55051

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 11-309647 Summary of the invention

[0010] (Problems to be solved by the invention)

[0011] However, it would be desirable to make the axis alignment between the main axis and the back axis easier.

[0012] An object of the present disclosure is to make axis alignment of a machine tool easier.

[0013] (Measures taken to solve the problem)

[0014] One aspect of the present disclosure is a machine tool having:

[0015] A first spindle that holds one end side of the workpiece;

[0016] a second spindle that holds the other end side of the workpiece;

[0017] a sensor that detects a physical quantity related to vibration when the first spindle and the second spindle rotate synchronously in a state where the first spindle and the second spindle hold the workpiece; and

[0018] A control unit performs axis alignment of the first main axis and the second main axis based on the physical quantity.

[0019] Another aspect of the present disclosure is a method for aligning an axis of a machine tool, comprising:

[0020] A first spindle that holds one end side of the workpiece;

[0021] a second spindle that holds the other end side of the workpiece;

[0022] a sensor that detects a physical quantity related to vibration when the first spindle and the second spindle rotate synchronously in a state where the first spindle and the second spindle hold the workpiece; and

[0023] A control unit performs axis alignment of the first main axis and the second main axis based on the physical quantity.

[0024] Furthermore, another aspect of the present disclosure is a program for causing a computer to execute the above-mentioned axis alignment method for a machine tool, or a storage medium storing the program non-temporarily.

[0025] (Effects of the Invention)

[0026] According to the present disclosure, it is possible to more easily perform axis alignment of a machine tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a figure which shows an example of the machine tool which concerns on embodiment.

[0028] Figure 2 It is a block diagram schematically showing an example of the structure of the machine tool according to the embodiment.

[0029] Figure 3 A diagram showing an example of the functional structure of the control unit.

[0030] Figure 4 It is a timing chart showing the detection value of the vibration sensor before and after the workpiece is tightened.

[0031] Figure 5This is a diagram showing experimentally obtained variance values ​​of detection values ​​of the vibration sensor when the second principal axis is intentionally offset with respect to the first principal axis.

[0032] Figure 6 A diagram showing an example of a locus along which the second spindle is moved when the axis alignment between the first spindle and the second spindle is performed.

[0033] Figure 7 To show the second principal axis according to Figure 6 A diagram showing an example of a variance value of a detection value of a vibration sensor when a trajectory moves.

[0034] Figure 8 A diagram showing an example of a locus for moving the second main shaft in the direction of the first phase when the axis alignment of the first main shaft and the second main shaft is performed.

[0035] Fig. 9 To show the second principal axis according to Figure 8 A diagram showing an example of a variance value of a detection value of a vibration sensor when a trajectory moves.

[0036] Fig.10 This is a diagram showing an example of a locus along which the second spindle moves starting from (X1, Y1) when the axis alignment between the first spindle and the second spindle is performed.

[0037] Fig.11 To show the second principal axis according to Fig.10 A diagram showing an example of a variance value of a detection value of a vibration sensor when a trajectory moves.

[0038] Fig.12 1 is a flowchart showing a flow when the axis alignment of the first spindle and the second spindle is performed.

[0039] Fig.13 : is a flowchart showing the flow of the circle movement process.

[0040] Fig.14 This is a flowchart showing the flow of the linear movement process.

[0041] Fig.15 This is a diagram showing an experimentally determined range of detection values ​​of the vibration sensor when the second main axis is intentionally offset with respect to the first main axis. DETAILED DESCRIPTION

[0042] A machine tool according to one aspect of the present invention comprises a first spindle for gripping one end of a workpiece, a second spindle for gripping the other end of the workpiece, a sensor for detecting physical quantities related to vibrations when the first spindle and the second spindle rotate synchronously while the first spindle and the second spindle grip the workpiece, and a control unit for performing axial alignment of the first spindle and the second spindle based on the physical quantities.

[0043] When the first spindle and the second spindle hold a workpiece and rotate synchronously, it is desirable that the axes of the first spindle and the second spindle are aligned. Therefore, axis alignment is performed when the machine tool is manufactured. In addition, even if axis alignment is performed when the machine tool is manufactured, there is a risk of axis deviation over time or due to usage conditions. Therefore, there is also a case where axis alignment is performed before the machine tool is used. Therefore, the control unit performs axis alignment when the machine tool is manufactured or before use.

[0044] The axis alignment of the first spindle and the second spindle is performed when the first spindle and the second spindle rotate synchronously in a state where the first spindle and the second spindle hold the same workpiece. In addition, "when rotating synchronously" only means when the first spindle and the second spindle rotate synchronously in result, for example, including when the first spindle and the second spindle are controlled to rotate synchronously, or when the first spindle and the second spindle rotate when the first spindle and the second spindle have a unit for synchronous rotation. When the first spindle and the second spindle rotate synchronously in this way, if an axis offset occurs between the first spindle and the second spindle, vibration is generated in the first spindle or the second spindle. Therefore, it is possible to determine whether the axes of the first spindle and the second spindle are aligned based on the vibration. Accordingly, the control unit performs axis alignment based on the vibration.

[0045] The sensor may be any sensor that can detect a physical quantity related to the vibration generated in the first spindle or the second spindle, and may be, for example, a vibration sensor (including an acceleration sensor) or a position sensor.

[0046] The following describes an embodiment of the present disclosure with reference to the accompanying drawings. However, unless otherwise specified, the scope of the present disclosure is not limited to the size, material, shape, relative arrangement, etc. of the components described in the embodiment.

[0047] <First Embodiment>

[0048] Figure 1 FIG. 1 is a diagram showing an example of a machine tool 1 according to the present embodiment. Figure 1As shown, the machine tool 1 of this embodiment has a first spindle 11 and a first spindle frame 12 that rotatably supports the first spindle 11. The first spindle 11 has a first clamping claw 13, and the first clamping claw 13 can perform a tightening action to install one end side of the workpiece W. In addition, the machine tool 1 also has a second spindle 21 and a second spindle frame 22 that rotatably supports the second spindle 21 on an axis substantially the same as the first spindle 11. The second spindle 21 can be a back spindle. The second spindle 21 has a second clamping claw 23, and the second clamping claw 23 can perform a tightening action to install the other end side of the workpiece W. In addition, an adjustment unit 24 that moves the second spindle 21 relative to the second spindle frame 22 is provided between the second spindle 21 and the second spindle frame 22. The adjustment unit 24 can make the second spindle 21 relatively move in two axial directions, such as the X-axis and the Y-axis. The adjustment unit 24 is configured to include, for example, a gear and an actuator that operates the gear. The first spindle frame 12 and the second spindle frame 22 are fixed to a base 100, which is, for example, the same structure, in such a manner that their relative positions do not change. Figure 1 In the embodiment, the axial direction of the first main axis 11 and the second main axis ( Figure 1 The left and right directions in the figure are set as the Z-axis direction, and the direction perpendicular to the Z-axis and parallel to the top surface of the base 100 ( Figure 1 The vertical direction in the figure is set as the Y-axis direction, and the direction perpendicular to the top surface of the base 100 ( Figure 1 The front-to-back direction in the figure is set as the X-axis direction.

[0049] The tightening action of the first jaw 13 and the second jaw 23 on the workpiece W can be achieved by a clamping actuator (not shown) composed of, for example, a cylinder, a piston, etc. When the workpiece W is tightened by the first jaw 13 and the second jaw 23, the first spindle 11 and the second spindle 21 rotate synchronously, for example, the workpiece W is cut by a tool. In addition, hereinafter, when the workpiece W is clamped by the first jaw 13, it is also referred to as the workpiece W being clamped by the first spindle 11. Similarly, when the workpiece is clamped by the second jaw 23, it is also referred to as the workpiece W being clamped by the second spindle 21.

[0050] A vibration sensor 25 for measuring the vibration of the second spindle 21 is installed on the second spindle 21. For example, the vibration sensor 25 can measure the vibration of the second spindle 21 only when the axis alignment of the first spindle 11 and the second spindle 21 is performed, or it can always measure the vibration of the second spindle 21 when the machine tool 1 is working. The timing of the measurement performed by the vibration sensor 25 can be appropriately changed. In addition, the vibration sensor 25 only needs to be arranged in a position where it can measure the vibration of the second jaw 23. The vibration sensor 25 can also be arranged as close to the second jaw 23 as possible. In the present embodiment, an acceleration sensor is used as the vibration sensor 25. The acceleration sensor is a sensor that can measure, for example Figure 1The sensor for measuring acceleration in one of the X-axis direction or the Y-axis direction shown in the figure may be another method, but as another method, it may be a sensor capable of measuring acceleration in two or more directions. In addition, the vibration sensor 25 is not limited to an acceleration sensor, and may be a distance sensor or the like. In addition, a plurality of sensors may be used. In addition, in the following, when the detection value of the vibration sensor 25 is mentioned, it may be a voltage as an output value of the vibration sensor 25, or it may be a value obtained by converting the voltage into acceleration or vibration. This conversion is performed by the axis alignment unit 402 described below.

[0051] The machine tool 1 includes a control unit 40 . The control unit 40 is a computer for controlling the machine tool 1 . Figure 2 1 is a block diagram schematically showing an example of the structure of the machine tool 1 .

[0052] The control unit 40 has a general computer structure. The control unit 40 has a processor 41, a main storage unit 42, an auxiliary storage unit 43, an input unit 44, and an output unit 45. These components are connected to each other through a bus. Sensors such as the vibration sensor 25 are connected to the bus through an interface, and signals from these sensors are input to the control unit 40. On the other hand, an actuator for rotating the first spindle 11, an actuator for rotating the second spindle 21, an actuator for performing the tightening and loosening actions of the first claw 13, an actuator for performing the tightening and loosening actions of the second claw 23, an adjustment unit 24, etc. are connected to the bus through an interface, and control signals are sent from the control unit 40 to these components.

[0053] The processor 41 is a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc. The processor 41 controls the machine tool 1 and performs various information processing operations. The main storage unit 42 is a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The auxiliary storage unit 43 is an EPROM (Erasable Programmable ROM), a hard disk drive (HDD), a removable media, etc. The auxiliary storage unit 43 stores an operating system (OS), various programs, various tables, etc. The program stored in the auxiliary storage unit 43 is loaded by the processor 41 into the working area of ​​the main storage unit 42 and executed, and the execution of the program controls each component, etc. Based on this, the control unit 40 realizes the function that meets the specified target. The main storage unit 42 and the auxiliary storage unit 43 are computer-readable storage media. In addition, the control unit 40 can be a single computer or a structure in which multiple computers work together. In addition, the information stored in the auxiliary storage unit 43 may be stored in the main storage unit 42. In addition, the information stored in the main storage unit 42 may be stored in the auxiliary storage unit 43.

[0054] The input unit 44 is a device for receiving input operations performed by the user, and includes, for example, a touch panel, a mouse, a keyboard, or a microphone. The output unit 45 is a device for presenting information to the user, and may include, for example, an LCD (Liquid Crystal Display), an EL (Electroluminescence) panel, a speaker, a lamp, etc. In addition, the input unit 44 and the output unit 45 may be configured as a touch panel display.

[0055] Figure 3 1 is a diagram showing an example of the functional structure of the control unit 40. The control unit 40 includes a processing control unit 401 and an axis alignment unit 402 as functional structural elements. The processing control unit 401 and the axis alignment unit 402 are functional structural elements provided when the processor 41 of the control unit 40 executes various programs stored in the auxiliary storage unit 43, for example.

[0056] The machining control unit 401 controls the machine tool 1 when machining the workpiece W. The machining control unit 401 uses the first jaw 13 and the second jaw 23 to clamp the workpiece W, rotates the first spindle 11 and the second spindle 21 synchronously, and controls the movement of the tool, thereby, for example, cutting the workpiece W. The machining control unit 401 can use known techniques to control the machining of the workpiece W.

[0057] The axis alignment unit 402 performs axis alignment (axis center alignment) of the first spindle 11 and the second spindle 21 based on the detection value of the vibration sensor 25. The axis alignment unit 402 performs axis alignment before the machining control unit 401 performs machining control on the workpiece W. Figure 4 and Figure 5 The relationship between the detection value of the vibration sensor 25 and the axis deviation between the first spindle 11 and the second spindle 21 will be described.

[0058] Figure 4 1 is a timing chart showing the detection value of the vibration sensor 25 before and after the workpiece W is tightened. Figure 4 The horizontal axis represents time, and the vertical axis represents the voltage as the output of the vibration sensor 25. Figure 4 In the embodiment, when the time is 0, one end of the workpiece W is clamped by the first clamping jaw 13 only, and the first spindle 11, the workpiece W and the second spindle 21 rotate synchronously. Then, the other end of the workpiece W is clamped by the second clamping jaw 23. When the second spindle 21 clamps the workpiece W, the vibration sensor 25 detects the vibration generated at this time. Figure 4 Here, "clamping" indicates the vibration caused by the clamping. Thereafter, in a state where the first spindle 11 and the second spindle 21 hold both ends of the workpiece W, the first spindle 11 and the second spindle 21 rotate synchronously.

[0059] After the vibration generated by the clamping becomes sufficiently small, the variance value of the value detected by the vibration sensor 25 is correlated with the degree of axis deviation between the first spindle 11 and the second spindle 21. Figure 5 This is a diagram showing experimentally obtained variance values ​​of detection values ​​of the vibration sensor 25 when the second main axis 21 is intentionally offset with respect to the first main axis 11 . Figure 5 The horizontal axis in φ represents the relative offset of the second main axis 21 with respect to the first main axis 11 in the X-axis direction. Figure 5 The X-axis involved corresponds to Figure 1 In addition, there is no offset in the Y-axis direction. Figure 5 In , the variance values ​​are obtained and plotted multiple times with the same offset. Figure 5 The variance value in is Figure 4 The variance value of the value detected by the vibration sensor 25 during the period shown in the "measurement period" of FIG. Figure 4The measurement period is a period after the vibration generated by the clamping described above becomes sufficiently small, and is a sufficient period for calculating the variance value. In addition, hereinafter, when the variance is mentioned, it means the variance of the detection value of the vibration sensor 25.

[0060] like Figure 5 As shown in FIG. 1 , there is a correlation between the offset in the X-axis direction and the variance value. The larger the absolute value of the offset in the X-axis direction, the larger the variance value. The present disclosure utilizes this phenomenon to perform the axis alignment of the first spindle 11 and the second spindle 21. That is, the axis alignment of the first spindle 11 and the second spindle 21 is performed by moving the second spindle 21 in a direction in which the variance value of the detection value of the vibration sensor 25 becomes smaller.

[0061] Next, the control when the axis alignment of the first spindle 11 and the second spindle 21 is performed according to the present embodiment will be described. The axis alignment unit 402 performs the axis alignment of the first spindle 11 and the second spindle 21 in a state where the first spindle 11 and the second spindle 21 hold the same workpiece W and the first spindle 11 and the second spindle 21 rotate in a predetermined direction at a predetermined speed (i.e., in a synchronously rotating state). In addition, the axis alignment unit 402 performs the axis alignment after the vibration generated by the tightening of the workpiece W becomes sufficiently small so as not to be affected by such vibration. In addition, the axis alignment may be performed only once when the machine tool 1 is manufactured, may be performed each time the machine tool 1 is started, or may be performed each time the workpiece W is tightened.

[0062] Figure 6 One example of a locus along which the second spindle 21 is moved when the axis alignment of the first spindle 11 and the second spindle 21 is performed is shown. Figure 6 The X-axis and Y-axis in Figure 1 The X-axis and Y-axis correspond to each other. Figure 6 , the coordinates of the origin, which is the starting point of the second spindle 21, are expressed as (X0, Y0). The origin is the position of the center axis of the second spindle 21 when the second spindle 21 performs a tightening operation on the workpiece W. The axis alignment portion 402 moves the second spindle 21 along a circle S1 centered at the origin (X0, Y0). The diameter of the circle S1 can be set to an arbitrary value below the maximum value of the axis offset between the first spindle 11 and the second spindle 21 caused by the manufacturing tolerance, for example. That is, even if an axis offset between the first spindle 11 and the second spindle 21 occurs, it is considered that the axis offset occurs within the range of the manufacturing tolerance, so the second spindle 21 is moved within this range and the axis alignment position is obtained.

[0063] The axis alignment unit 402 performs the following processing in the axis alignment. The following (1) to (3) are Figure 6 The arrows (1)-(3) shown correspond.

[0064] (1) First, the axis alignment unit 402 generates a command to move the second spindle 21 to (XA, Y0) in the X-axis direction. The detection value of the vibration sensor 25 is not used at this time. The position (XA, Y0) is the intersection of the X-axis and the circle S1. In addition, the position (XA, Y0) or the straight radius of the circle S1 is pre-stored in the auxiliary storage unit 43. The axis alignment unit 402 sends the generated command to the adjustment unit 24, and the adjustment unit 24 moves the second spindle 21 according to the command. When the current position of the second spindle 21 reaches the position (XA, Y0), the axis alignment unit 402 stops the second spindle 21. The current position of the second spindle 21 can be detected by a sensor, for example, or can be calculated based on the movement amount of the adjustment unit 24.

[0065] (2) Next, the axis alignment unit 402 generates a command to move the second main axis 21 along the circle S1. Figure 6 In the embodiment, the second spindle 21 is moved counterclockwise, but the present invention is not limited thereto and the second spindle 21 may be moved clockwise. For example, the detection value of the vibration sensor 25 is acquired at every predetermined phase with the origin (X0, Y0) as the center. In this case, the axis alignment unit 402 stops the second spindle 21 at every predetermined phase during the measurement period and acquires the detection value of the vibration sensor 25 during the measurement period. To this end, the axis alignment unit 402 generates a command to move the second spindle 21 along the circle S1 and a command to stop the second spindle 21 at every predetermined phase during the measurement period and sends them to the adjustment unit 24. In addition, the adjustment unit 24 moves the second spindle 21 according to the command.

[0066] The measurement period is pre-set to a period in which the variance value corresponding to the axis offset can be calculated with good accuracy. The axis alignment unit 402 associates the detection value of the vibration sensor 25 obtained during the measurement period at each specified phase with the phase centered on the origin (X0, Y0) and stores it in the auxiliary storage unit 43. Furthermore, based on the detection value of the vibration sensor 25 obtained during the measurement period, the variance value of the detection value of the vibration sensor 25 is calculated, and the variance value is associated with the phase centered on the origin (X0, Y0) and stored in the auxiliary storage unit 43. For example, the specified phase can be set according to the time required for axis alignment and the accuracy of axis alignment. The smaller the specified phase, the higher the accuracy of axis alignment, but the longer the time required for axis alignment, so the user can set it according to whether time priority or accuracy priority. For example, the specified phase can be input from the input unit 44.

[0067] (3) Furthermore, when the second spindle 21 returns to the position (XA, Y0), the axis alignment unit 402 stops the detection of vibration by the vibration sensor 25 and generates a command to move the second spindle 21 to the origin (X0, Y0). The axis alignment unit 402 sends the generated command to the adjustment unit 24, and the adjustment unit 24 moves the second spindle 21 to the origin (X0, Y0) according to the command.

[0068] Figure 7 To illustrate the second main axis 21 according to Figure 6 The diagram shows an example of the variance value of the detection value of the vibration sensor 25 when the trajectory moves. The phase on the horizontal axis represents the phase when the second main axis 21 is at the position (XA, Y0) with the origin (X0, Y0) as the center, and is set to 0. Figure 7 In the example shown, as the phase increases from 0, the variance value decreases. For example, at the phase shown by A1, the variance value becomes the minimum value shown by B1. In addition, the larger the phase is compared with A1, the larger the variance value is. In addition, the phase shown by A1 is also referred to as the first phase A1 hereinafter. The position with the smallest variance value on circle S1 is equivalent to the first target position of the present disclosure.

[0069] exist Figure 7 In the example shown, the variance value is the smallest at the first phase A1. Thus, by moving the second main axis 21 from the origin (X0, Y0) toward the first phase A1, the variance value can be reduced. In other words, it is considered that the offset between the first main axis 11 and the second main axis 21 becomes smaller.

[0070] Therefore, the axis alignment unit 402 searches for a position where the variance value becomes smaller while moving the second principal axis 21 in the direction of the first phase A1. Figure 8 1 is a diagram showing an example of a locus along which the second spindle 21 is moved in the direction of the first phase A1 when the axis alignment between the first spindle 11 and the second spindle 21 is performed. Figure 8 The origin (X0, Y0) in Figure 6 The origin (X0, Y0) in is the same position.

[0071] The axis alignment unit 402 moves the second main axis 21 on a straight line L1 extending from the origin (X0, Y0) in the direction of the first phase A1. To this end, the axis alignment unit 402 performs the following processing. The following (4)-(5) and Figure 8 The arrows (4)-(5) in FIG.

[0072] (4) The axis alignment unit 402 generates a command to move the second spindle 21 along the straight line L1 in a direction away from the origin (X0, Y0). For example, the detection value of the vibration sensor 25 is acquired at a predetermined distance from the origin (X0, Y0). In this case, the axis alignment unit 402 stops the second spindle 21 at a predetermined distance during a measurement period, and acquires the detection value of the vibration sensor 25 during the measurement period. To this end, the axis alignment unit 402 generates a command to move the second spindle 21 along the straight line L1 and a command to stop the second spindle 21 at a predetermined distance during a measurement period, and sends them to the adjustment unit 24. In addition, the adjustment unit 24 moves the second spindle 21 according to the command.

[0073] The axis alignment unit 402 associates the detection value of the vibration sensor 25 obtained during the measurement period with the distance from the origin (X0, Y0) at every predetermined distance and stores it in the auxiliary storage unit 43. Furthermore, the variance value of the detection value of the vibration sensor 25 is calculated based on the detection value of the vibration sensor 25 obtained during the measurement period, and the variance value is associated with the distance from the origin (X0, Y0) and stored in the auxiliary storage unit 43. For example, the predetermined distance can be set according to the time required for the axis alignment and the accuracy of the axis alignment. The smaller the predetermined distance, the higher the accuracy of the axis alignment, but the longer the time required for the axis alignment, so the user can set it according to whether to prioritize time or accuracy. For example, the predetermined distance can be input from the input unit 44.

[0074] (5) The axis alignment unit 402 finds the second origin (X1, Y1) where the variance value becomes the minimum when the variance value changes from a decreasing trend to an increasing trend, and generates a command to move the second main axis 21 to the second origin (X1, Y1). The axis alignment unit 402 compares the variance value stored in the auxiliary storage unit 43 with the variance values ​​before and after it, thereby finding the variance value B2 when the trend changes from a decreasing trend to an increasing trend, and finds the distance A2 from the origin (X0, Y0) corresponding to the variance value B2. The position (X1, Y1) of the second main axis 21 after moving the distance A2 is obtained by calculating X1=A2·cosA1 and Y1=A2·sinA1. This position (X1, Y1) is also referred to as the second origin (X1, Y1) hereinafter. The second origin (X1, Y1) is the position when the distance A2 is moved relative to the origin (X0, Y0) in the direction of the first phase A1. The axis alignment unit 402 sends the generated command to the adjustment unit 24, and the adjustment unit 24 moves the second main axis 21 to the second origin (X1, Y1) according to the command. In addition, the position with the smallest difference on the straight line L1 corresponds to the second target position of the present disclosure.

[0075] Fig. 9 To illustrate the second main axis 21 according to Figure 8FIG. 2 is a diagram showing an example of a variance value of the detection value of the vibration sensor 25 when the trajectory moves. The distance on the horizontal axis is the distance from the origin (X0, Y0). Fig. 9 (4)-(5) shown and Figure 8 The (4)-(5) shown above correspond to each other. Fig. 9 In the example shown, as the distance increases from 0, the variance value decreases, and when the distance is A2, the variance value is the minimum value shown by B2. Furthermore, the larger the distance is compared with A2, the larger the variance value is. In this way, when the distance is A2, the variance value becomes the minimum at B2.

[0076] The second origin (X1, Y1) is a position that is moved relative to the origin (X0, Y0) by a distance that minimizes the variance value in the direction of the phase where the variance value of the detection value of the vibration sensor 25 becomes the minimum. The second origin (X1, Y1) has a smaller variance value of the detection value of the vibration sensor 25 than the origin (X0, Y0). In this way, a position where the variance value of the detection value of the vibration sensor 25 is smaller can be found.

[0077] Here, when the axes of the first spindle 11 and the second spindle 21 are aligned, the variance value B2 of the detection value of the vibration sensor 25 at the second origin (X1, Y1) becomes sufficiently small. On the other hand, there may be a case where there is still an axis offset between the first spindle 11 and the second spindle 21. In this case, there is a position where the variance value of the detection value of the vibration sensor 25 is smaller. Therefore, the axis alignment unit 402 performs the control of (1) to (5) again with the second origin (X1, Y1) as the starting point. In this way, by repeatedly performing the above control, the position of the second spindle 21 where the variance value of the detection value of the vibration sensor 25 becomes smaller can be obtained.

[0078] Here, Fig.10 This is a diagram showing an example of a trajectory of the second spindle 21 moving from (X1, Y1) as a starting point when the axis alignment of the first spindle 11 and the second spindle 21 is performed. Fig.10 In the figure, the coordinates of the starting point of the second main axis 21 are the second origin (X1, Y1). The second definition (X1, Y1) is the origin of the X'Y' coordinate system. Fig.10 The second origin (X1, Y1) as the starting point in Figure 8 The axis alignment unit 402 moves the second principal axis 21 along a circle S2 centered at the second origin (X1, Y1). The circle S2 has a Figure 6 The circle S1 shown has the same diameter as that of the circle S2. In addition, as another method, the diameter of the circle S2 may also be smaller than the diameter of the circle S1.

[0079] and Figure 6The axis alignment unit 402 performs the following processing in the same manner as described in Fig.10 The arrows (6)-(8) shown correspond.

[0080] (6) First, the axis alignment unit 402 generates a command to move the second spindle 21 to the position (X1+XA, Y1) in the X'-axis direction. The detection value of the vibration sensor 25 is not used at this time. The axis alignment unit 402 sends the generated command to the adjustment unit 24, and the adjustment unit 24 moves the second spindle 21 according to the command.

[0081] (7) Next, the axis alignment unit 402 generates a command to move the second main shaft 21 along the circle S2. For example, the detection value of the vibration sensor 25 is acquired at every predetermined phase with the second origin (X1, Y1) as the center. In this case, the axis alignment unit 402 stops the second main shaft 21 at every predetermined phase during the measurement period, and acquires the detection value of the vibration sensor 25 during the measurement period. To this end, the axis alignment unit 402 generates a command to move the second main shaft 21 along the circle S2 and a command to stop the second main shaft 21 at every predetermined phase during the measurement period, and sends them to the adjustment unit 24. Then, the adjustment unit 24 moves the second main shaft 21 according to the command.

[0082] The measurement period is the same as in Figure 6 The axis alignment unit 402 associates the detection value of the vibration sensor 25 obtained at each specified phase during the measurement period with the phase centered on the second origin (X1, Y1) and stores it in the auxiliary storage unit 43. Furthermore, based on the detection value of the vibration sensor 25 obtained during the measurement period, the variance value of the detection value of the vibration sensor 25 is calculated, and the variance value is associated with the phase centered on the second origin (X1, Y1) and stored in the auxiliary storage unit 43. The specified phase is associated with the phase centered on the second origin (X1, Y1). Figure 6 However, as another method, it is also possible to adopt Figure 6 The specified phase shown is different from the phase.

[0083] (8) Furthermore, when the second spindle 21 returns to the position (X1+XA, Y1), the axis alignment unit 402 stops the vibration detection by the vibration sensor 25 and generates a command to move the second spindle 21 to the second origin (X1, Y1). The axis alignment unit 402 sends the generated command to the adjustment unit 24, and the adjustment unit 24 moves the second spindle 21 to the second origin (X1, Y1) according to the command.

[0084] Fig.11 To show the second main axis 21 along Fig.10The diagram shows an example of the variance value of the detection value of the vibration sensor 25 when the trajectory moves. The phase on the horizontal axis represents the phase when the second main axis 21 is at the position (X1+XA, Y1) with the second origin (X1, Y1) as the center, and is set to 0. Fig.11 In the example shown, as the phase increases from 0, the variance value decreases. For example, at the phase shown by A3, the variance value is the minimum value shown by B3. In addition, the larger the phase is compared to A3, the larger the variance value is. In addition, the phase shown by A3 is also referred to as the second phase A3 hereinafter. The position on the circle S2 where the variance value is the smallest is also equivalent to the first target position of the present invention.

[0085] exist Fig.11 In the example shown, the variance value becomes minimum at the second phase A3. Thus, by moving the second spindle 21 from the second origin (X1, Y1) in the direction of the second phase A3, the variance value can be reduced. In other words, the axis offset between the first spindle 11 and the second spindle 21 can be reduced. In this case, by performing the same Figure 8 and Fig. 9 The same process as described in , can find the position where the variance value is further reduced. In this case, the X'Y' axis is replaced with the XY axis and the same process is repeatedly performed.

[0086] On the other hand, when the first spindle 11 and the second spindle 21 are aligned near the second origin (X1, Y1), when the second spindle 21 is moved from the second origin (X1, Y1), the axis offset may increase and the variance value may increase. In this case, Fig.11 The minimum value of the variance value B3 shown is greater than or equal to Fig. 9 The minimum variance value B2 is shown. Therefore, it is considered that if Fig.11 The minimum value of the variance value B3 shown is greater than or equal to Fig. 9 If the variance value shown is the minimum value B2, there is no need to further move the position of the second main axis 21. Fig.11 The minimum value of the variance value B3 shown is greater than or equal to Fig. 9 When the variance value has the minimum value B2, it is determined that the axis alignment between the first main axis 11 and the second main axis 21 is completed at the second origin (X1, Y1) at this time.

[0087] According to the above description, by alternately and repeatedly performing the process of moving the second main axis 21 along the circle S1 to find the phase where the variance value becomes the minimum, and the process of moving the second main axis 21 along the straight line L1 to find the position where the variance value becomes the minimum, the position where the variance value becomes further reduced can be obtained. In this way, the axis alignment of the first main axis 11 and the second main axis 21 can be achieved.

[0088] When the axis alignment between the first spindle 11 and the second spindle 21 is completed, the axis alignment unit 402 updates the second origin (X1, Y1) to the origin of the second spindle 21. In addition, at this time, the second spindle 21 is located at the second origin (X1, Y1), so the machining control by the machining control unit 401 starts while maintaining the position of the second spindle 21.

[0089] Next, a flow when the axis alignment of the first main spindle 11 and the second main spindle 21 in the present embodiment is performed will be described. Fig.12 This is a flowchart showing the process when the axis alignment between the first spindle 11 and the second spindle 21 is performed. This routine is executed before the machining control performed by the machining control unit 401 is performed in the machine tool 1. For example, the execution can be triggered by the input of the user to the input unit 44 for executing the machining control. In addition, as another method, it can also be executed according to the input of the user to the input unit 44 when the machine tool 1 is manufactured or when the user starts the machine tool 1. In addition, as another method, it can also be executed every specified time or every specified number of starts of the machine tool 1.

[0090] In step S101, the axis alignment unit 402 performs a tightening process. The tightening process is a process in which one end side of the workpiece W is gripped by the first spindle 11, and the other end side of the workpiece W is gripped by the second spindle 21, and the workpiece W is rotated synchronously. In addition, in the present embodiment, the first spindle 11 is rotated at a predetermined rotation speed in a state in which one end side of the workpiece W is clamped by the first spindle 11. In addition, the second spindle 21 clamps the other end side of the workpiece W in a state in which the second spindle 21 is rotated synchronously with the first spindle 11.

[0091] In step S102, the axis alignment unit 402 determines whether a predetermined time has passed after the second spindle 21 and the workpiece W are fastened. The predetermined time here refers to, for example, the time until the vibration generated by the fastening of the workpiece W becomes sufficiently small. If an affirmative determination is made in step S102, the process proceeds to step S103, and if a negative determination is made, the process of step S102 is executed again.

[0092] In step S103, the axis alignment section 402 acquires the origin of the second spindle 21. The origin here is the position of the second spindle 21 at the time point when the tightening is completed in step S101, the origin (X0, Y0) set in step S310 described below, or the origin (X0, Y0) updated in step S106 in the previous routine.

[0093] In step S104, the axis alignment unit 402 performs a circular movement process. Figure 6As described in , the circular movement process is a process of acquiring the variance value of the detection value of the vibration sensor 25 at a plurality of positions while moving the second spindle 21 along the circle S1. Fig.13 : is a flowchart showing the flow of the circle movement process. Fig.13 The process shown is a subroutine executed in step S104. The first circular movement process is used to obtain Figure 7 The processing of B1 as the minimum value of the variance value shown, the second and subsequent circular movement processing is equivalent to the processing for obtaining Fig.11 The process of B3 as the minimum value of the variance value is shown.

[0094] In step S201, the axis alignment unit 402 moves the second spindle 21 to the circle S1. The axis alignment unit 402 generates a command to move the second spindle 21 to the circle S1, and sends it to the adjustment unit 24. In step S202, the axis alignment unit 402 moves the second spindle 21 by a predetermined phase on the circle S1. The axis alignment unit 402 generates a command to move the second spindle 21 by a predetermined phase on the circle S1 relative to the second spindle frame 22, and sends it to the adjustment unit 24.

[0095] In step S203, the axis alignment unit 402 detects vibration by acquiring the detection value of the vibration sensor 25 during the measurement period. The detection value of the vibration sensor 25 is associated with the phase at that time and stored in the auxiliary storage unit 43. In step S204, the axis alignment unit 402 calculates a variance value based on the detection value acquired in step S203. In addition, in step S205, the axis alignment unit 402 associates the calculated variance value with the phase at that time and stores it in the auxiliary storage unit 43.

[0096] In step S206, the axis alignment unit 402 determines whether the second main shaft 21 has completed one rotation of the circle S1. The axis alignment unit 402 determines whether the current position of the second main shaft 21 is the same as the position after the movement in step S201. If a positive determination is made in step S206, the process proceeds to step S207, and if a negative determination is made, the process returns to step S202.

[0097] In step S207, the axis alignment section 402 extracts the minimum value B1 from the variance values ​​stored in step S205. Furthermore, in step S208, the axis alignment section 402 acquires the phase A1 corresponding to the minimum value B1 of the variance value extracted in step S207 from the data stored in step S205.

[0098] In step S209, the axis alignment unit 402 moves the second spindle 21 to the origin (X0, Y0) as the starting point. The axis alignment unit 402 generates a command to move the second spindle 21 to the origin (X0, Y0) and sends it to the adjustment unit 24. In addition, as another method, the processing of step S209 may be performed in parallel with the processing of step S207 and step S208, or the processing of step S209 may be performed before the processing of step S207 and step S208. If the processing of step S209 is completed, the process returns to Fig.12 The routine shown goes to step S105.

[0099] Back to Fig.12 In step S105, the axis alignment unit 402 determines whether the minimum value B1 of the variance value obtained in step S104 is greater than or equal to the minimum value B2 of the variance value obtained in the previous step S108. In addition, when this routine is executed for the first time, B2 has not yet been obtained. Therefore, the value that makes a positive determination in step S105 during axis alignment is used as the initial value of B2 and is pre-stored in the auxiliary storage unit 43. As another method, the initial value of B2 can also be set to a sufficiently large value so that a negative determination is definitely made in step S105. As another method, a step of calculating the variance value at the origin can be added between step S102 and step S103, and the variance value at the origin is used as the initial value of B2. In the case of a positive determination in step S105, the process proceeds to step S106, and in the case of a negative determination, the process proceeds to step S108 to perform linear movement processing.

[0100] Here, Fig.14 This is a flowchart showing the flow of the linear movement process. Fig.14 The processing shown is a subroutine executed in step S108. Fig. 9 The processing of B2 shown as the minimum variance value is equivalent.

[0101] In step S301, the axis alignment unit 402 moves the second spindle 21 by a predetermined distance in the phase A1 direction corresponding to the closest minimum value B1 of the variance value obtained in the previous step S208. The axis alignment unit 402 generates a command and sends it to the adjustment unit 24 to move the second spindle 21 by a predetermined distance from the origin in the phase A1 direction relative to the second spindle frame 22.

[0102] In step S302, the axis alignment unit 402 detects vibration by acquiring the detection value of the vibration sensor 25 during the measurement. The detection value of the vibration sensor 25 is associated with the distance from the origin at that time and stored in the auxiliary storage unit 43. In step S303, the axis alignment unit 402 calculates a variance value based on the detection value acquired in step S302. In addition, in step S304, the axis alignment unit 402 associates the calculated variance value with the distance from the origin at that time and stores it in the auxiliary storage unit 43.

[0103] In step S305, the axis alignment unit 402 determines whether the variance value has changed from a decreasing trend to an increasing trend. For example, when the variance value stored in the previous step S304 is smaller than the variance value stored in the previous step S304, and the variance value stored in the current step S304 is larger than the variance value stored in the previous step S304, the axis alignment unit 402 determines that the variance value has changed from a decreasing trend to an increasing trend. As another method, when there is no change or a very small change compared to the variance value stored in the previous step S304, it can be determined that the variance value has changed from a decreasing trend to an increasing trend. In addition, it is not limited to this, as long as the minimum value of the variance value can be obtained. In the case of a positive determination in step S305, the process proceeds to step S306, and in the case of a negative determination, the process returns to step S301.

[0104] In step S306, the axis alignment unit 402 extracts the minimum value B2 from the variance values ​​stored in step S304. Then, in step S307, the axis alignment unit 402 obtains the distance A2 corresponding to the minimum value B1 of the variance value extracted in step S306 from the data stored in step S304. Furthermore, in step S308, the axis alignment unit 402 calculates the coordinates corresponding to the distance A2, that is, the second origin (X1, Y1), based on the distance A2 obtained in step S307. For example, the axis alignment unit 402 calculates X1 and Y1 using the calculation formulas X1=A2·cosA1 and Y1=A2·sinA1.

[0105] In step S309, the axis alignment unit 402 moves the second spindle 21 to the second origin (X1, Y1). The axis alignment unit 402 generates a command and sends it to the adjustment unit 24 to move the second spindle 21 to the second origin (X1, Y1). In step S310, the axis alignment unit 402 updates the origin so that the second origin (X1, Y1) becomes the new origin (X0, Y0) of the second spindle 21. If the processing of step S310 is completed, the command returns to Fig.12That is, the process of moving the second main axis 21 along the circle S1 to obtain the phase A1 where the variance value becomes minimum and the process of moving the second main axis 21 in the direction where the variance value becomes minimum to obtain the position (X1, Y1) where the variance value of the detection value of the vibration sensor 25 becomes minimum are repeatedly performed alternately until an affirmative determination is made in step S105.

[0106] Back to Fig.12 In step S106, the axis alignment unit 402 updates the position of the second spindle 21 at this time to the origin of the second spindle 21 when machining the workpiece W. The origin of the second spindle 21 is stored in the auxiliary storage unit 43. In addition, in step S107, the axis alignment unit 402 resets the minimum value B2 of the variance value. Accordingly, the minimum value B2 of the variance value is restored to the initial value.

[0107] According to the present embodiment as described above, the axis alignment of the first spindle 11 and the second spindle 21 can be performed based on the variance value of the detection value of the vibration sensor 25. That is, by adjusting the relative position of the first spindle 11 and the second spindle 21 to a position where the variance value of the detection value of the vibration sensor 25 becomes smaller, the axis alignment can be performed faster and more accurately.

[0108] <Second Embodiment>

[0109] In the first embodiment, the variance value of the detection value of the vibration sensor 25 is obtained while the second main axis 21 is moved along the circle S1 and the straight line L1. On the other hand, in the second embodiment, a grid is generated around the second main axis 21, the variance value of the detection value of the vibration sensor 25 is obtained at each intersection of the grid, and the position where the variance value is the smallest is determined as the axis alignment position of the first main axis 11 and the second main axis 21.

[0110] In addition, the size of the grid is related to the accuracy of axis alignment. The smaller the grid, the higher the accuracy of axis alignment. However, the smaller the grid, the more locations to obtain variance values, so the longer the time required for axis alignment. Therefore, the size of the grid can be determined based on whether to prioritize the accuracy of axis alignment or the time required for axis alignment.

[0111] In addition, the grid may be initially set large to move the second principal axis 21 to the position where the variance value is the smallest, and then a smaller grid may be generated around the position to find the position where the variance value is the smallest. In this way, the process of gradually reducing the grid and calculating the variance value may be repeatedly performed to narrow the range of the axis alignment position of the first principal axis 11 and the second principal axis 21.

[0112] In this way, by generating a grid and calculating the variance value of the detection value of the vibration sensor 25 at each intersection of the grid, the axis alignment of the first and second main axes 11 and 21 can also be performed.

[0113] <Other Implementation Methods>

[0114] In the first and second embodiments, the axis alignment is performed using the variance value of the detection value of the vibration sensor 25, but the sensor is not limited thereto, and any sensor that can detect a physical quantity related to vibration may be used. For example, a displacement meter, an ammeter, an AE (Acoustic Emission) sensor, or a microphone may be used.

[0115] In the first embodiment, the second main axis 21 is moved along the circle S1, but may be moved along the side of a polygon centered at the origin instead. In addition, the vibration sensor 25 may detect vibration at each vertex of the polygon and further calculate a variance value.

[0116] In the first and second embodiments, the variance (i.e., the average value of the square of the deviation from the average value) is used, but the present invention is not limited thereto, and other values ​​indicating the degree of dispersion may be used. For example, the standard deviation, the root mean square, the range (the difference between the maximum value and the minimum value), or the amplitude of the vibration may be used instead of the variance.

[0117] Fig.15 This is a diagram showing an experimentally obtained range of the detection value (the difference between the maximum value and the minimum value) of the vibration sensor 25 when the second main axis 21 is intentionally offset with respect to the first main axis 11 . Fig.15 The horizontal axis in φ represents the relative offset of the second main axis 21 with respect to the first main axis 11 in the X-axis direction. Fig.15 The X-axis involved is Figure 1 In addition, there is no offset in the Y-axis direction. Fig.15 In the example, the range of the detection value is obtained multiple times under the same offset and plotted. Fig.15 The range of the detection value in is the range of the vibration sensor 25 in Figure 4 The "measurement period" in the graph shows the difference between the maximum and minimum values ​​detected during the period.

[0118] like Fig.15 As shown in FIG. 1 , there is a correlation between the offset in the X-axis direction and the range of the detection value. The larger the absolute value of the offset in the X-axis direction, the larger the range of the detection value. Therefore, similar to the variance value described in the first embodiment, the axis alignment of the first spindle 11 and the second spindle 21 can be performed using the range of the detection value. That is, the axis alignment of the first spindle 11 and the second spindle 21 can be performed by moving the second spindle 21 in a direction in which the range of the detection value of the vibration sensor 25 becomes smaller.

[0119] (Explanation of Reference Numerals)

[0120] 1: machine tool; 11: first spindle; 12: first spindle frame; 13: first clamping claw; 21: second spindle;

[0121] 22: second spindle frame; 23: second clamping claw; 24: adjustment unit; 25: vibration sensor;

[0122] 40: control unit; 41: processor; 42: main storage unit; 43: auxiliary storage unit; 44: input unit;

[0123] 45: Output unit.

Claims

1. A machine tool, wherein: It has: A first spindle that holds one end side of the workpiece; a second spindle that holds the other end side of the workpiece; a sensor that detects a physical quantity related to vibration when the first spindle and the second spindle rotate synchronously in a state where the first spindle and the second spindle hold the workpiece; as well as A control unit performs axis alignment of the first main axis and the second main axis based on the physical quantity.

2. The machine tool according to claim 1, wherein: The control unit detects the physical quantity by the sensor at each of the first plurality of positions where the relative positions of the first spindle and the second spindle are offset. The position where the physical quantity is the smallest among the first plurality of positions is set as a first target position of the first spindle and the second spindle.

3. The machine tool according to claim 2, wherein: The first plurality of positions are set as positions that are staggered on the same circle.

4. The machine tool according to claim 3, wherein: the control unit detects the physical quantity by the sensor at each of a second plurality of positions where the relative positions of the first main axis and the second main axis are offset from the center of the circle in the direction of the first target position, The position where the physical quantity is the smallest among the second plurality of positions is set as the second target position of the first spindle and the second spindle.

5. The machine tool according to claim 4, wherein: The control unit repeatedly detects the physical quantity at each of the first plurality of positions using the sensor with the second target position as the center of the circle, and obtains the position where the physical quantity is the smallest among the first plurality of positions, thereby updating the first target position. The second target position is updated by detecting the physical quantity by the sensor at each of the second plurality of positions in the direction of the updated first target position and acquiring the position where the physical quantity is the smallest among the second plurality of positions.

6. The machine tool according to claim 5, wherein: The control unit determines that the latest second target position is an axis-aligned position of the first main axis and the second main axis when the physical quantity of the first target position is greater than or equal to the physical quantity of the latest second target position.

7. The machine tool according to any one of claims 2 to 6, wherein: The physical quantity is a variance value of a detection value of the sensor.

8. The machine tool according to any one of claims 2 to 7, wherein: The control portion sets the first plurality of positions within a tolerance range of an axis offset between the first spindle and the second spindle.

9. A method for aligning the axes of a machine tool, wherein: have: A first spindle that holds one end side of the workpiece; a second spindle that holds the other end side of the workpiece; a sensor that detects a physical quantity related to vibration when the first spindle and the second spindle rotate synchronously in a state where the first spindle and the second spindle hold the workpiece; as well as A control unit performs axis alignment of the first main axis and the second main axis based on the physical quantity.

Images