Machine tool

Abstract

To provide a machine tool that is configured so that presence / absence of abnormalities such as abrasion of a plurality of tools can be monitored, so as to reduce frequencies at which the tools are replaced.SOLUTION: A machine tool 1 is provided with: a first headstock 12 having a first spindle 11 for holding a work-piece W; a first tool unit 45 having a plurality of tools 45a, 45b and 45c for machining the work-piece W; an AE sensor part 50, mounted on the first headstock 12, which detects AE (Acoustic Emission) waves generated during machining of the work-piece W; and a control part 300 that compares an AE wave parameter of the AE waves with a preset threshold, so as to determine whether the tools 45a, 45b and 45c have reached service lives before the tools are broken.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a machine tool. [Background technology]

[0002] Countermeasures against tool wear in a moving-spindle type automatic lathe include periodic tool replacement using a tool counter as disclosed in Patent Document 1, and tool breakage detection by current value monitoring as disclosed in Patent Document 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-133482 A [Patent Document 2] Patent No. 5394093 Summary of the Invention [Problem to be solved by the invention]

[0004] In periodic tool replacement using a tool counter, tools are replaced when the number of times a workpiece is processed or the processing time reaches a specified value, and the condition of the tools is not checked individually. However, since tool life varies depending on the processing conditions or environment, tools are replaced before their lifespan is reached or after their lifespan has expired. This raises the risk that the tools cannot be used to their limit.

[0005] When detecting tool breakage by monitoring the current value of the spindle, etc., the change in current value due to tool wear is very small, so the detection is only possible after the tool breaks. This can lead to continued machining with a tool that is already worn out before it breaks, which can lead to poor quality of the machined surface of the workpiece. For this reason, it was necessary to check for problems with the workpiece in the post-process and select it.

[0006] In addition, the method of checking the wear condition of the cutting edge of each tool using a microscope or the like requires the tool to be removed for inspection, which necessitates stopping the machine and places a heavy burden on the worker.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a machine tool that can monitor abnormalities such as wear of multiple tools and reduce the number of times tools need to be replaced. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, a machine tool according to a first aspect of the present invention comprises a headstock having a spindle for holding a workpiece, a tool unit having a plurality of tools for machining the workpiece, an AE sensor attached to the headstock for detecting AE (Acoustic Emission) waves while the workpiece is being machined, and a control unit for comparing AE wave parameters of the AE waves with a preset threshold value to determine whether the tool has reached the end of its life before breaking.

[0009] In order to achieve the above-mentioned object, a machine tool according to a second aspect of the present invention comprises a tool unit having a plurality of tools for machining a workpiece, an AE sensor that detects AE waves while the workpiece is being machined, a control unit that compares AE wave parameters of the AE waves with a preset threshold value and determines whether the tool has reached the end of its life before breakage, and a spare tool that is used in place of the tool when it is determined that the tool has reached the end of its life before breakage. Effect of the Invention

[0010] According to the present invention, it is possible to monitor abnormalities such as wear of a plurality of tools of a machine tool, thereby reducing the number of times tools need to be replaced. [Brief description of the drawings]

[0011] [Figure 1] 1 is a front view of a machine tool according to an embodiment of the present invention; [Diagram 2]1 is a plan view of a machine tool according to an embodiment of the present invention; [Diagram 3] 2 is a view taken along the arrow A1 in FIG. 1 and is a side view of a machine tool according to one embodiment of the present invention. [Figure 4] 2 showing the AE sensor unit, (b) is a view taken along the line A2 in (a), and (c) is a view taken along the line A3 in (a). [Diagram 5] 4 is a graph showing an example of an AE wave detected by an AE sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a machine tool according to an embodiment of the present invention will be described with reference to the drawings. In the following, the axial direction along which the rotation axes of the first main shaft 11 and the second main shaft 21 extend is defined as the Z-axis direction, the height direction perpendicular to the Z-axis direction is defined as the Y-axis direction, and the direction perpendicular to the Y-axis and Z-axis directions is defined as the X-axis direction.

[0013] As shown in Figures 1 to 3, machine tool 1, which is a movable spindle type automatic lathe, includes a bed S which is a base of machine tool 1, a first spindle unit 10 having a first spindle 11, a second spindle unit 20 having a second spindle 21, a first spindle moving mechanism 13Z, second spindle moving mechanisms 25X, 25Z, first tool moving mechanisms 42X, 42Y, a first tool unit 45, a guide bush device 90, a second tool moving mechanism 27Y, a second tool unit 26, an AE sensor unit 50, and a control unit 300.

[0014] The first spindle unit 10 holds and rotates a workpiece W. The first spindle moving mechanism 13Z moves the first spindle unit 10 in the Z-axis direction. The second spindle unit 20 is provided at a position facing the first spindle unit 10 in the Z-axis direction, and holds and rotates the workpiece W received from the first spindle unit 10. The second spindle moving mechanism 25X moves the second spindle unit 20 in the X-axis direction so that the second spindle unit 20 faces both the first spindle 11 and the second tool unit 26. The second spindle moving mechanism 25Z moves the second spindle unit 20 in the Z-axis direction. The first tool unit 45 machines the workpiece W held by the first spindle 11 and the second spindle 21. The first tool moving mechanism 42X moves the first tool unit 45 in the X-axis direction. The first tool moving mechanism 42Y moves the first tool unit 45 in the Y-axis direction. The guide bush device 90 is located on the tip side of the first spindle unit 10 (the side closer to the second spindle unit 20), and supports the outer periphery of the workpiece W held by the first spindle unit 10. The second tool unit 26 machines the workpiece W held by the second spindle 21 . The second tool moving mechanism 27Y moves the second tool unit 26 in the Y-axis direction. The AE sensor unit 50 detects AE waves during machining of the workpiece W, as will be described later. The control unit 300 controls the overall operation of the machine tool 1 including the above-mentioned components.

[0015] The first spindle unit 10 includes a first spindle 11 and a first spindle stock 12 that rotatably supports the first spindle 11. The first spindle 11 grips one end of a workpiece W. A workpiece rotating motor (not shown) that rotates the first spindle 11 is built into the first spindle stock 12.

[0016] The second spindle unit 20 includes a second spindle 21 that grips the other end of the workpiece W, and a second spindle stock 22 that rotatably supports the second spindle 21. A workpiece rotating motor (not shown) that rotates the second spindle 21 is built into the second spindle stock 22.

[0017] A fixed base 15 is fixedly installed on the bed S. A first tool moving mechanism 42X and a guide bush device 90 are attached to the fixed base 15. A first tool moving mechanism 42Y is attached to the first tool moving mechanism 42X.

[0018] The first tool unit 45 includes a plurality of tools 45a, 45b, and 45c, a tool holder 45d for holding the plurality of tools 45a, a tool holder 45e for holding the plurality of tools 45b, and a tool holder 45f for holding the plurality of tools 45c. The tool 45a is, for example, a cutting tool or a drill, extending in the X-axis direction. Six tools 45a are attached to the tool holder 45d in a line in the Y-axis direction. The tool 45b is, for example, a cutting tool or a drill, extending in the X-axis direction. As shown in FIG. 3, when the machine tool 1 is viewed from the Z-axis direction, the tool 45b is provided at a position facing the tool 45a across the workpiece W. The three tools 45b are attached to the tool holder 45e in a line in the Y-axis direction. The tool 45c is, for example, a cutting tool or a drill, extending parallel to the Z-axis toward the first spindle unit 10 side (FIG. 1) and the second spindle unit 20 side (FIG. 1). When the machine tool 1 is viewed from the Z-axis direction, the tool 45c is provided above the tool 45b. The tool holder 45f is a member for attaching a round shank tool. The tools 45c are attached to the tool holder 45f in four rows aligned in the Y-axis direction.

[0019] The guide bush device 90 is fastened to the fixed base 15 by fastening members such as bolts. A portion of the workpiece W protruding from the guide bush device 90 to the opposite side of the first spindle 11 is machined by the tools 45a, 45b, and 45c of the first tool unit 45. Since the guide bush device 90 supports the workpiece W, deflection or vibration of the workpiece W during machining is suppressed even for a long workpiece W.

[0020] The guide bush device 90 can be selectively attached to and detached from the fixed table 15. For example, when machining a short workpiece W, the operator selects a state in which the guide bush device 90 is not attached to the fixed table 15. On the other hand, when machining a long workpiece W, the operator selects a state in which the guide bush device 90 is attached to the fixed table 15. The guide bushing device 90 may be of any type, such as a direct drive guide bushing device, a stationary guide bushing device, a Kelle type rotating guide bushing device, or a belt drive guide bushing device.

[0021] 2 and 3, the second tool moving mechanism 27Y is installed on a base 28 provided on a bed S. The second tool moving mechanism 27Y is provided at a position farther in the X-axis direction from the first spindle 11 than the second tool unit 26. In addition, the second tool moving mechanism 27Y is located between the motor 25M of the second spindle moving mechanism 25X and the motor 42M of the first tool moving mechanism 42X in the Z-axis direction.

[0022] The second tool unit 26 is configured to be movable in the Y-axis direction by the second tool moving mechanism 27Y. The second tool unit 26 includes a plurality of tools 26a, 26c, and a tool holding unit 26b that holds the tools 26a, 26c. The tools 26a, 26c are, for example, a cutting tool or a drill. The tools 26a each extend in the Z-axis direction and are arranged in the X-axis direction. As shown in FIG. 3, three tools 26a arranged in the X-axis direction are also attached to the lower side of the three tools 26a arranged in the X-axis direction. That is, a total of six tools 26a are attached to the tool holding unit 26b, three in the X-axis direction and two in the Y-axis direction. The tools 26c each extend in the X-axis direction and are arranged in the Y-axis direction. That is, two tools 26c are attached to the tool holding unit 26b so as to be arranged in the Y-axis direction.

[0023] The above-mentioned first spindle moving mechanism 13Z, second spindle moving mechanism 25X, 25Z, first tool moving mechanism 42X, 42Y, and second tool moving mechanism 27Y each have a motor, a ball screw, a nut, etc., and move the above-mentioned parts by a feeding operation using these.

[0024] The control unit 300 includes, for example, a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores a program that defines the procedure of processing by the CPU, and the like.

[0025] Next, a description will be given of an example of processing executed by the control unit 300. The control unit 300 executes this processing in accordance with an NC (Numerical Control) program created in advance.

[0026] The control unit 300 performs the first machining of the workpiece W held by the first spindle 11 using the first tool unit 45. For example, when cutting the outer diameter of the workpiece W as the first machining, the control unit 300 moves the cutting edges of the bites of the tools 45a and 45b via the first tool moving mechanisms 42X and 42Y to a position in contact with the outer circumferential surface of the workpiece W held by the first spindle 11, and while rotating the first spindle 11 together with the workpiece W, feeds the cutting edges of the bites of the tools 45a and 45b in the X-axis direction via the first tool moving mechanism 42X, and feeds the workpiece W in the Z-axis direction via the first spindle moving mechanism 13Z. The first machining may also be a drilling process on the workpiece W using the tool 45c.

[0027] When the first machining is completed, the control unit 300 moves the second spindle unit 20 in the X-axis direction and the Z-axis direction via the second spindle moving mechanisms 25X, 25Z so that the second spindle 21 faces the first spindle 11. Then, the control unit 300 transfers the workpiece W that has been subjected to the first machining from the first spindle 11 to the second spindle 21.

[0028] Next, the control unit 300 performs the second machining of the workpiece W held by the second spindle 21 while using the second tool unit 26 and the like. For example, when performing the second machining with the second tool unit 26, the control unit 300 adjusts the relative positions of the tools 26a, 26c and the workpiece W via the second spindle moving mechanism 25X, the second spindle moving mechanism 25Z, and the second tool moving mechanism 27Y. It is sufficient to operate the necessary moving mechanism depending on the machining. For example, when performing the second machining by drilling the workpiece W, the control unit 300 moves the workpiece W in the X-axis direction and the Z-axis direction relative to the tools 26a, 26c via the second spindle moving mechanisms 25X and 25Z.

[0029] The second machining is not limited to drilling holes in the workpiece W using the tools 26a and 26c, and may be machining such as cutting the outer diameter of the workpiece W using the tools 26a and 26c. The second machining may also be drilling holes in the workpiece W using the tool 45c.

[0030] When the second machining is completed, the control unit 300 discharges the workpiece W that has been subjected to the second machining from the second spindle 21 to a workpiece catcher (not shown). The workpiece W discharged to the workpiece catcher is transported to the outside of the machine by a workpiece conveyor (not shown). This completes the machining process. This machining process is performed for each workpiece W to be machined.

[0031] Next, the AE sensor section 50 in this embodiment will be described. 1 and 2, the AE sensor unit 50 is installed on the upper surface of the first headstock 12. The position of the AE sensor unit 50 and the periphery of the processing portion of the workpiece W are separated by a cover (not shown). 4(a) to 4(c), AE sensor section 50 includes AE sensor 51, AE sensor fixing holder 52, presser plate 53, and amplifier 54. Machine tool 1 also includes display section 400 as an example of a notification section that notifies information related to operation.

[0032] The AE sensor 51 is a sensor that detects AE waves. AE is a phenomenon in which elastic energy stored inside a material is released as an elastic wave having a high frequency when the material is deformed, cracked, or worn.

[0033] By using the AE sensor 51 to detect and evaluate the AE waves (elastic waves), it is possible to non-destructively grasp the occurrence and progression of defects or wear. In addition, since it can capture elastic waves of primary phenomena caused by the occurrence of cracks or wear, it can detect changes in condition earlier than other sensors that capture secondary phenomena, such as vibration sensors and temperature sensors. Note that, since the AE frequency of AE waves during plastic deformation differs for each material, it is possible to detect AE waves more accurately by selecting an AE sensor that is suitable for the measurement target.

[0034] The AE sensor 51 includes a cylindrical sensor body 51a that is installed on the upper surface of the first headstock 12, and a cable 51b that extends radially from one point on the circumferential side surface of the sensor body 51a.

[0035] The sensor main body 51a converts the detected AE waves into a voltage signal. The cable 51b transmits the voltage signal from the sensor main body 51a to the amplifier .

[0036] The AE sensor fixing holder 52 is a member that holds the sensor main body 51a of the AE sensor 51 on the first headstock 12. The AE sensor fixing holder 52 includes a holder mounting base 55 that is attached to the first headstock 12, a holder 56 that holds the sensor main body 51a, and a sensor fixing spring 57. The holder 56 is movable up and down relative to the holder mounting base 55.

[0037] The holder mounting base 55 is a component that suspends and supports the sensor fixing spring 57 and the holder 56. The holder mounting base 55 includes mounting portions 55a and 55b, side walls 55c, 55d, and 55e, and an upper wall 55f. The mounting parts 55a, 55b are located at the bottom of the holder mounting base 55. Magnets are provided on the edges of the mounting parts 55a, 55b, and are attached by magnetic force to the first headstock 12. When Fig. 4(c) is the front view of the AE sensor unit 50, side walls 55c, 55d, and 55e are provided except for the front surface, and a top wall 55f is disposed on top of these. The holder 56 is a member that holds the sensor main body 51a of the AE sensor 51 by pressing it downward from the lower surface of the holder mounting base 55 using a sensor fixing spring 57. The holder 56 is formed by bending a plate material, and has side walls 56a and 56b and an upper wall 56c. The side walls 56a, 56b are arranged side by side at a distance slightly larger than the diameter of the sensor main body 51a. The lower sides of the side walls 56a, 56b are arranged to float above the upper surface of the first headstock 12 when the AE sensor unit 50 is assembled. In addition, the side wall 56a is provided with a notch for pulling out the cable 51b of the AE sensor 51. The upper wall 56c connects the upper edges of the side walls 56a, 56b, and presses the sensor body 51a of the AE sensor 51 against the first headstock 12 for tight contact. 4(c), the sensor fixing springs 57 are coil springs arranged side by side when viewed from the front of the AE sensor unit 50. The tension of the sensor fixing springs 57 presses the sensor main body 51a downward against the first headstock 12 via the holder 56. The pressing plate 53 is a member bent in a stepped manner from a flat plate, and is provided with an attachment portion 53a, a side wall 53b, and an upper wall 53c in this order from the bottom. The mounting portion 53a is fastened to the first headstock 12 with a screw 58. In addition, the upper wall 53c is located on the upper surface of the upper wall 55f of the AE sensor fixing holder 52, and presses down on the upper surface of the upper wall 55f to prevent the AE sensor fixing holder 52 from moving.

[0038] The amplifier 54 amplifies the voltage signal transmitted from the cable 51b of the AE sensor 51. In addition, the AE waves extracted by a filter such as a band-pass filter that performs noise removal processing on the signal, an A / D converter that converts the signal into a digital signal, and the like are transmitted to the control unit 300.

[0039] The display unit 400 displays necessary information regarding the operation of the machine tool 1 based on commands from the control unit 300 .

[0040] Next, the procedure from mounting the AE sensor 51 to changing the tool based on the detection of the AE wave will be described below. In the following example, the AE sensor 51 is mounted on the first headstock 12. In this embodiment, a narrow band AE sensor that matches the AE frequency of the tool material is used.

[0041] First, the AE sensor 51 is attached to the AE sensor fixing holder 52. For example, the sensor body 51a of the AE sensor 51 is attached to an AE sensor body holding portion (not shown) in the holder 56. Next, a contact catalyst such as Vaseline or grease is applied to the lower surface of the sensor body 51a, which is the wave-receiving surface of the AE sensor. Next, the AE sensor fixing holder 52 is attached to the first headstock 12 by the magnetic force of the mounting portions 55 a and 55 b of the holder mounting base 55 . Finally, the presser plate 53 is attached to the first headstock 12 with the screws 58, and the AE sensor fixing holder 52 is pressed down from above.

[0042] Following the attachment of the AE sensor 51, a threshold value for the energy of the AE wave is preset before use. The energy value of the AE wave will be described later. If the energy value exceeds the threshold value during detection by the AE sensor, it is determined that the tool has reached the end of its life. The threshold value is determined in advance by conducting a test or the like. For example, the energy of the AE wave is measured when the coating on the cutting edge has completely peeled off, and the threshold value is determined based on the measured value. A lower limit may be set in addition to an upper limit for the threshold value. After that, the determined threshold value is set in the control unit 300 by the operator.

[0043] After setting the threshold value, the operator operates the machine tool 1 to machine the workpiece W. While the workpiece W is being machined, the AE sensor 51 detects AE waves from the tools 45a, 45b, 45c being machined. The AE waves emitted from the tools 45a, 45b, 45c propagate through the workpiece W, the first spindle 11, and the first headstock 12, and are detected by the AE sensor 51. When the workpiece W is not being machined with the tools 45a, 45b, 45c, such as when the tool is indexed or the workpiece W is discharged, detection by the AE sensor 51 is not performed to prevent erroneous detection.

[0044] The AE wave detected by the AE sensor 51 is amplified and noise is removed, and the signal is measured as an AE waveform. The control unit 300 converts the measured AE waveform into an energy value and monitors whether the energy exceeds a threshold value due to tool wear or the like.

[0045] If the energy value does not exceed the threshold value, it is determined that the tool life has not been reached, and machining is continued. If the energy value exceeds a threshold value during measurement, it is determined that the tool currently performing machining has reached the end of its tool life. After the control unit 300 determines that the tool has reached the end of its tool life, if a spare tool is provided to replace the tool that has reached the end of its tool life, the machine tool 1 positions the spare tool based on a command from the control unit 300 and performs machining. If there is no spare tool, machining is stopped and operation is halted. Furthermore, when control unit 300 determines that the tool life has been reached, it causes display unit 400 to display a message indicating that the tool life has been reached on the operation screen of machine tool 1. Control unit 300 may also determine the presence or absence of a spare tool, and cause display unit 400 to display a message indicating the presence or absence of a spare tool.

[0046] A tool that has reached the end of its life is replaced with a new tool by an operator while the machine tool 1 is stopped.

[0047] Next, the evaluation parameters of the measured AE waveform will be described with reference to Figure 5. By comparing the values ​​of the evaluation parameters with the normal values, it is possible to detect and predict abnormalities.

[0048] The AE waveform is, for example, the waveform shown in Fig. 5. The evaluation parameters for this waveform are as follows: In this embodiment, wear is monitored using (2) the energy value among the following: (1) Maximum amplitude The maximum amplitude of the waveform correlates with the progress of the crack and the amount of wear. (2) Energy value The energy value is the area (integral value) of the AE waveform within the measurement time, and is correlated with the amount of wear and the crack area. (3) RMS value (effective value) The RMS value shown by the dashed line is the square root of the average of the squared values ​​of the AE wave amplitude values, and is the effective value of the AE signal acquired per measurement unit time. The RMS value is correlated with the friction coefficient.

[0049] (effect) According to the embodiment described above, the following effects are achieved. (1) In the above embodiment, the machine tool 1 includes a first headstock 12 having a first spindle 11 that holds a workpiece W, a first tool unit 45 having a plurality of tools 45a, 45b, 45c for machining the workpiece W, an AE sensor unit 50 attached to the first headstock 12 and configured to detect AE waves during machining of the workpiece W, and a control unit 300 that compares an AE wave parameter, which is an evaluation parameter for the AE wave, with a preset threshold value to determine whether or not the tools 45a, 45b, 45c have reached the end of their lives before breaking. This makes it possible to monitor wear and other abnormalities in multiple tools using a single sensor. Furthermore, since the measurement by the AE sensor unit 50 is performed while the workpiece is being machined, the wear of the tools 45a, 45b, and 45c can be monitored without extending the cycle time. In addition, since the wear state of the multiple tools 45a, 45b, and 45c can be monitored in real time, all of the tools 45a, 45b, and 45c can be used to the limit of their lifespan without breakage. This reduces the number of tool replacements to the minimum necessary, and the number of replacement tools can be reduced. In addition, since the AE wave, which is a primary phenomenon occurring when cracks or wear occur in the tools 45a, 45b, and 45c, is detected, changes in the tool condition can be detected at an earlier stage, and abnormalities such as tool breakage can be predicted. In addition, since the AE sensor unit 50 is attached to the first headstock 12, there is no need to install a sensor around the machining area. Because the first headstock 12 and the machining area are separated by a cover, the sensor is not directly affected by coolant or cutting chips during machining, so detection accuracy is stable and the sensor is less susceptible to breakdown and deterioration. In addition, since the AE waves emitted by the tool during machining propagate through the workpiece W, the first spindle 11, and the first spindle stock 12 and reach the AE sensor 51 of the AE sensor section 50, wear monitoring can be performed even with the guide bush device 90 installed.

[0050] (2) In the above embodiment, when the control unit 300 determines, based on the AE wave parameters, that the tools 45a, 45b, 45c have reached the end of their lives before being broken, the machine tool 1 stops operation of the machine tool 1. As a result, by stopping the operation of the machine tool 1, machining is not continued with the tools 45a, 45b, and 45c that have reached the end of their tool life, so that the quality of the machined surface of the workpiece W can be maintained at a good level. In addition, when machining is performed using tools 45a, 45b, and 45c that have reached the end of their tool life, there is no need to check the condition of the machined surface of the workpiece W or to sort it in the subsequent process, which contributes to reducing the burden on the worker and the number of steps. Furthermore, the yield rate is improved because the number of defective works is reduced.

[0051] (3) In the above embodiment, the machine tool 1 includes a first tool unit 45 having a plurality of tools 45a, 45b, 45c for machining the workpiece W, an AE sensor 51 for detecting AE waves during machining of the workpiece W, a control unit 300 for comparing AE wave parameters of the AE waves with a preset threshold value to determine whether the tools 45a, 45b, 45c have reached the end of their lives before breaking, and spare tools for use in place of the tools 45a, 45b, 45c when it is determined that the tools 45a, 45b, 45c have reached the end of their lives before breaking. As a result, if a spare tool is used, there is no need to stop the operation of the machine tool 1, reducing the number of times the machine tool 1 is stopped for tool replacement and enabling automatic operation for long periods of time.

[0052] (4) In the above embodiment, when control unit 300 of machine tool 1 determines that tools 45a, 45b, 45c have reached the end of their life before breaking, if there is a spare tool, it positions the spare tool in place of tools 45a, 45b, 45c and performs machining. As a result, when the control unit 300 determines that the tool has reached the end of its life, a spare tool is used, thereby making it possible to prevent machining from being continued with a tool that has reached the end of its life. Furthermore, by using a spare tool, the downtime of the machine tool 1 can be reduced.

[0053] (5) In the above embodiment, the machine tool 1 is provided with a display unit 400 that displays information regarding the operation of the machine tool 1, and the control unit 300 causes the display unit 400 to display information regarding the life of tools 45a, 45b, 45c when the AE wave parameter reaches a threshold value. This allows the display unit 400 to display information such as which of the tools 45a, 45b, and 45c has reached the end of its life, thereby notifying the worker that the tool needs to be replaced.

[0054] (Modification) The present invention is not limited to the above-described embodiment and drawings. Modifications (including the deletion of components) can be made as appropriate within the scope of the present invention. An example of a modification will be described below.

[0055] In the above embodiment, the AE sensor unit 50 is attached to the upper surface of the first headstock 12, but the AE sensor unit 50 may be attached anywhere as long as it can detect AE waves and the sensor can be fixed. For example, by attaching the AE sensor part 50 to the tool holding parts 45d and 45e, which are tool rests of the first tool unit 45, the AE sensor 51 is brought closer to the tools 45a, 45b, and 45c to be measured. This improves the detection sensitivity of the AE sensor 51, making it easier to detect AE waves. Also, the AE sensor may be attached to the tool holding portion 45f. This allows the AE sensor to be closer to the tool 45c to be measured that is attached to the tool holding portion 45f. Also, the AE sensor may be attached to each of the tool holding portions 45d, 45e, and 45f.

[0056] The method of fixing the AE sensor 51 is not limited to the method in the above embodiment, and other fixing methods may be used. Furthermore, the configuration of the AE sensor section 50 is not limited to that in the above embodiment. The above fixing method shows one example of a method by which the AE sensor 51, which has the AE sensor wave receiving surface on the underside of the sensor body 51a, can be pressed against the first headstock 12 for close contact. The fixing method for the AE sensor 51 can be selected from any method as long as it can bring the sensor body 51a into close contact with the first headstock 12. Even if a narrow band AE sensor is used as in the above embodiment, if an AE sensor with a different shape, size, cable extension position, or wave receiving surface position is used, the fixing method will also be different. In that case, the configurations of the AE sensor fixing holder 52 and the pressing plate 53 in the AE sensor unit 50 are appropriately changed. Furthermore, as will be described later, by employing a different type of AE sensor 51, the configuration of the entire AE sensor section can be changed. Furthermore, the method of fixing the AE sensor 51 can be changed as appropriate depending on the size and shape of the location where the AE sensor 51 is attached. As described above, the AE sensor section 50 of the embodiment is merely an example, and by selecting an AE sensor suited to the object to be measured, the AE sensor section 50 can be modified in various ways, such as by adding, changing or deleting components.

[0057] In the above embodiment, the AE waves emitted by the tools 45a, 45b, 45c are detected. However, other than that, for example, the AE waves emitted by the workpiece W being machined may be detected.

[0058] In the above embodiment, the number of the AE sensor 51 is one, but a plurality of the AE sensors 51 may be installed. For example, an AE sensor 51 may be added to the second tool unit 26 or the second spindle unit 20 so that wear of the tools 26a, 26c of the second tool unit 26 can be detected.

[0059] The type of the AE sensor 51 used is not limited to that in the above embodiment. For example, there are two types of AE sensors: narrowband types that react strongly in a specific narrow frequency band, and broadband types that react in a wide frequency band. It is possible to use an AE sensor of the type appropriate for the object to be measured.

[0060] In the above embodiment, the AE wave is measured by the AE sensor 51 during the processing of the workpiece W, but it may be measured only at a specific timing during the processing. This makes it possible to effectively prevent false detection of AE waves according to the object being measured.

[0061] In the above embodiment, the object to be detected by the AE sensor 51 has been described as wear of the tools 45a, 45b, and 45c. However, the AE sensor 51 can also be used to detect changes in the cutting condition, such as monitoring whether chips have become caught on the workpiece W or the tools 45a, 45b, and 45c. In addition, when changing the machining conditions, by comparing the AE waves before and after the change and changing to more appropriate machining conditions, it is possible to expect an extension of the tool life.

[0062] In the above embodiment, the energy value in FIG. 5 is used to evaluate the AE wave, but a different parameter such as a maximum amplitude value or an RMS value (root mean square value) may be used to monitor a tool abnormality.

[0063] The message to be displayed on the display unit 400 when it is determined that the tools 45a, 45b, and 45c have reached the end of their lifespan is arbitrary. For example, in addition to the information that the tools 45a, 45b, and 45c have reached the end of their life, the installation positions of the tools, a message urging the user to replace the tools, and the like may be displayed.

[0064] In the above embodiment, the display unit 400 that displays information is shown as an example of the notification unit of the machine tool 1. However, the notification unit is not limited to the display unit 400 as long as it can notify information related to the operation of the machine tool 1. The machine tool 1 may have a display unit including an audio output unit (not shown) that emits sound as an example of the notification unit, and notify the worker of various situations by images and sounds from the audio output unit. The machine tool 1 may have an independent audio output unit as an example of the notification unit, and notify the worker of various situations only by sounds from the audio output unit. The machine tool 1 may have a display unit 400 and an audio output unit that are independent of each other as a notification unit, and notify the worker of information related to the operation by images and sounds.

[0065] A plurality of types of threshold values ​​to be compared with the AE wave parameters may be set in advance according to the cutting conditions of the tools 45a, 45b, and 45c, and the threshold values ​​may be changed during measurement.

[0066] The AE sensor 51 may be used, for example, as a load monitor for detecting the load of a tool.

[0067] Additionally, the first spindle unit 10, the second spindle unit 20, etc. may have any configuration. [Explanation of symbols]

[0068] 1...machine tool, 10...first spindle unit, 11...first spindle, 12...first spindle stock, 13Z...first spindle movement mechanism, 15...fixed base, 20...second spindle unit, 21...second spindle, 22...second spindle stock, 25M...motor, 25X...second spindle movement mechanism, 25Z...second spindle movement mechanism, 26...second tool unit, 26a...tool, 26b...tool holder, 26c...tool, 27Y...second tool movement mechanism, 28...base, 42M...motor, 42X...first tool movement mechanism, 42Y...first tool movement mechanism, 45...first tool unit, 45a...tool, 45b...tool, 45c...tool, 45d...tool holder portion, 45e...tool holding portion, 45f...tool holding portion, 50...AE sensor portion, 51...AE sensor, 51a...sensor main body portion, 51b...cable, 52...AE sensor fixing holder, 53...pressing plate, 53a...mounting portion, 53b...side wall, 53c...upper wall, 54...amplifier, 55...holder mounting base, 55a...mounting portion, 55b...mounting portion, 55c...side wall, 55d...side wall, 55e...side wall, 55f...upper wall, 56...holder, 56a...side wall, 56b...side wall, 56c...upper wall, 57...sensor fixing spring, 58...screw, 90...guide bush device, 300...control portion, 400...display portion, S...bed, W...work

Claims

1. A headstock having a spindle for holding a workpiece; A tool unit having a plurality of tools for machining the workpiece; An AE sensor attached to the headstock for detecting an AE (Acoustic Emission) wave during machining of the workpiece; a control unit that compares an AE wave parameter of the AE wave with a preset threshold value and determines whether the tool has reached the end of its life before being broken; A machine tool comprising:

2. When the control unit determines that the tool has reached the end of its life before being broken based on the AE wave parameters, the operation of the machine tool is stopped. The machine tool according to claim 1.

3. a tool unit having a plurality of tools for machining a workpiece; An AE sensor that detects AE waves during processing of the workpiece; a control unit that compares an AE wave parameter of the AE wave with a preset threshold value and determines whether the tool has reached the end of its life before being broken; a spare tool to be used in place of the tool when it is determined that the tool has reached the end of its life before being broken; A machine tool comprising:

4. When the control unit determines that the tool has reached the end of its life before being broken, if there is a spare tool, the control unit positions the spare tool in place of the tool and performs processing. The machine tool according to claim 1.

5. a notification unit that notifies information related to the operation of the machine tool, The control unit causes the notification unit to notify information regarding the life of the tool when the AE wave parameter reaches the threshold value. The machine tool according to any one of claims 1 to 4.

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