Cutting system and method for determining state of milling tool

Abstract

The cutting system includes a management device, a milling cutter, and a plurality of sensors attached to a shaft portion of the milling cutter. The management device determines the state of the milling cutter on the basis of the sensor information from the plurality of sensors. The plurality of sensors include at least one acceleration sensor and at least one strain sensor. The management device determines whether or not the milling cutter rotates on the basis of sensor information from the at least one acceleration sensor, and determines whether or not the milling cutter is in contact with the object to be cut on the basis of sensor information from the at least one strain sensor.

Description

Technical Field

[0001] The invention relates to a cutting system and a method for determining the state of a milling tool. Background Art

[0002] International Publication No. 2021 / 029099 (Patent Document 1) discloses a milling tool having a plurality of sensors including an acceleration sensor and a strain sensor in a tool holder.

[0003] Patent Document 1: International Publication No. 2021 / 029099 Summary of the invention

[0004] The cutting system involved in the present invention comprises a management device, a milling tool and a plurality of sensors mounted on the milling tool. The management device determines the state of the milling tool based on sensor information from the plurality of sensors. The plurality of sensors include at least one acceleration sensor and at least one strain sensor. The management device determines whether the milling tool is rotating based on sensor information from at least one acceleration sensor, and determines whether the milling tool is in contact with a workpiece based on sensor information from at least one strain sensor.

[0005] The method involved in the present invention is a method for determining the state of a milling tool. The milling tool is provided with at least one acceleration sensor and at least one strain sensor. The method comprises the following steps: a step of obtaining sensor information from at least one acceleration sensor and at least one strain sensor; a step of determining whether the milling tool has no rotation based on the sensor information from at least one acceleration sensor; and a step of determining whether the milling tool is in contact with a workpiece based on the sensor information from at least one strain sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a diagram showing the outline of the cutting system according to the present embodiment.

[0007] Figure 2 This is a diagram showing a milling cutter with a shaft portion mounted on a tool holder.

[0008] Figure 3 This is a diagram showing the arrangement of sensors when the milling tool is viewed from the positive direction of the Z axis.

[0009] Figure 4 This is a diagram showing an example of detection signals of each sensor when the rotation speed of the milling cutter is changed in a no-load state.

[0010] Figure 5 This is a diagram for explaining the state of the milling tool based on the detection signals of each sensor.

[0011] Figure 6 This is a flowchart for explaining the state determination process of the milling tool executed by the management device.

[0012] Figure 7 It is a figure which shows the milling cutter of a modification. DETAILED DESCRIPTION

[0013] [Problems to be Solved by the Invention]

[0014] An object of the present invention is to provide a cutting system and method capable of determining the state of a milling tool based on information from a plurality of sensors attached to the milling tool.

[0015] [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a cutting system and method capable of determining the state of a milling tool based on information from a plurality of sensors attached to the milling tool.

[0017] [Description of Embodiments of the Invention]

[0018] First, embodiments of the present invention will be described by way of examples.

[0019] (1) The cutting system 50 according to the present invention includes a milling tool 100, a plurality of sensors 120, 130, and a management device 200. The milling tool 100 includes a shaft 106 having a first end 107 provided with a blade for cutting a workpiece 18, and a second end 108 mounted on a tool holder 105. The plurality of sensors 120, 130 are mounted on the shaft 106 of the milling tool 100. The management device 200 determines the state of the milling tool 100 based on sensor information from the plurality of sensors 120, 130. The plurality of sensors include at least one acceleration sensor 120 and at least one strain sensor 130. The management device 200 determines whether the milling tool 100 is rotating based on sensor information from at least one acceleration sensor 120, and determines whether the milling tool 100 is in contact with the workpiece based on sensor information from at least one strain sensor 130.

[0020] (2) In the cutting system 50 according to (1) above, the tool holder 105 rotates the milling tool 100 about the axial direction of the shaft portion 106 . At least one acceleration sensor 120 is disposed to detect centrifugal acceleration of the milling tool 100 .

[0021] (3) In the cutting system 50 according to (2) above, the plurality of sensors include a plurality of acceleration sensors 120. The plurality of acceleration sensors 120 are arranged on concentric circles centered on the rotation axis of the shaft 106 in the same plane with the rotation axis as the normal line.

[0022] (4) In the cutting system 50 according to (3) above, the plurality of acceleration sensors 120 include four acceleration sensors 120 disposed at a center portion of the acceleration sensor 120 at intervals of 90° in the circumferential direction of the shaft 106 .

[0023] (5) In the cutting system 50 according to any one of (1) to (3) above, the management device 200 determines that the milling tool 100 is rotating when the acceleration detected by at least one acceleration sensor 120 is greater than the first threshold value. Alternatively, the management device 200 determines that the milling tool 100 is stopped when the acceleration detected by at least one acceleration sensor 120 is less than the first threshold value.

[0024] (6) In the cutting system 50 according to (1) above, the milling cutter 100 rotates about the axial direction of the shaft 106 . In addition, at least one strain sensor 130D is disposed to detect the strain of the shaft 106 in the circumferential direction.

[0025] (7) In the cutting system 50 according to (1) above, the plurality of sensors include a plurality of strain sensors 130. The plurality of strain sensors 130 are arranged on concentric circles centered on the rotation axis of the shaft 106 in the same plane with the rotation axis as the normal line.

[0026] (8) In the cutting system 50 according to (7) above, the plurality of strain sensors 130 include four strain sensors 130A to 130D, and the four strain sensors 130A to 130D are arranged at the center of the strain sensor at intervals of 90° in the circumferential direction of the shaft 106 .

[0027] (9) In the cutting system 50 according to any one of (6) to (8) above, the management device 200 determines that the milling tool 100 is in contact with the workpiece 18 when the strain in the circumferential direction of the shaft portion 106 detected by at least one strain sensor 130D is greater than the second threshold value. Alternatively, the management device 200 determines that the milling tool 100 is not in contact with the workpiece 18 when the strain in the circumferential direction of the shaft portion 106 detected by at least one strain sensor 130D is less than the second threshold value.

[0028] (10) In the cutting system 50 according to (1) above, the milling cutter 100 rotates about the axial direction of the shaft 106 . At least one acceleration sensor 120 and at least one strain sensor 130 are alternately arranged in the circumferential direction of the shaft 106 .

[0029] (11) In the cutting system 50 according to (1) above, the management device 200 determines whether the milling tool 100 is in cutting based on sensor information from at least one acceleration sensor 120 and sensor information from at least one strain sensor 130 .

[0030] (12) In the cutting system 50 involved in the above (11), the management device 200 determines that the milling tool 100 is in cutting when the acceleration detected by at least one acceleration sensor 120 is greater than the first threshold value and the strain in the circumferential direction of the shaft 106 detected by at least one strain sensor 130 is greater than the second threshold value.

[0031] (13) In the cutting system 50 involved in the above (11), the management device 200 determines that the milling tool 100 is in an abnormal state when the acceleration detected by at least one acceleration sensor 120 is less than the first threshold value and the strain in the circumferential direction of the shaft 106 detected by at least one strain sensor 130 is greater than the second threshold value.

[0032] (14) In the cutting system 50 according to (13) above, when the management device 200 determines that the milling tool 100 is in an abnormal state, the management device 200 notifies the user of the abnormal state.

[0033] (15) In the cutting system 50 involved in the above (11), the management device 200 determines that the milling tool 100 is rotating without cutting when the acceleration detected by at least one acceleration sensor 120 is greater than the first threshold value and the strain in the circumferential direction of the shaft 106 detected by at least one strain sensor 130 is less than the second threshold value.

[0034] (16) In the cutting system 50 according to (1) above, the milling tool 100 includes a shaft portion 106 having a first end portion 107 provided with a cutting edge portion for cutting a workpiece 18, and a second end portion 108 mounted on the tool holder 105. The management device 200 corrects the measurement value of the at least one strain sensor 130 to zero when the axial strain of the shaft portion 106 detected by the at least one strain sensor 130 is smaller than the second threshold value.

[0035] (17) The cutting system 50 according to any one of (1) to (16) above further includes a wireless communication device 140 which is mounted on the tool holder 105 and is used to send sensor information from the plurality of sensors 120 , 130 to the management device 200 .

[0036] (18) The cutting system 50 according to any one of (1) to (17) above further includes a power storage device 150 that is mounted on the tool holder 105 and supplies electric power for driving the plurality of sensors 120 and 130 .

[0037] (19) In the cutting system 50 according to any one of (1) to (18) above, the management device 200 further includes a storage device 230 for storing sensor information from the plurality of sensors 120 and 130 .

[0038] (20) In the cutting system 50 according to (19) above, the management device 200 adds tag information corresponding to the state of the milling tool 100 to the sensor information from the plurality of sensors 120 and 130 and stores the tag information in the storage device 230 .

[0039] (21) In the cutting system 50 involved in (20) above, the management device 200 pre-stores the state transition of the milling tool 100 from the start of machining to the completion of machining of the workpiece 18. The management device 200 classifies the sensor information stored in the storage device 230 into a machining data group for each workpiece 18 based on the state transition and the tag information.

[0040] (22) In the cutting system 50 involved in (20) above, the management device 200 pre-stores the state transition of the milling tool 100 from the start of machining to the completion of machining of the workpiece 18 as the first data. When the second data indicating the state transition of the milling tool 100 obtained based on the sensor information obtained from the start of machining to the completion of machining of the workpiece 18 is inconsistent with the first data, the management device 200 notifies the user of the machining abnormality of the workpiece 18.

[0041] (23) The method involved in the present invention is a method for determining the state of a milling tool 100 including a shaft portion 106, wherein the shaft portion 106 has: a first end portion provided with a blade portion for cutting a workpiece; and a second end portion mounted on a machine tool. At least one acceleration sensor 120 and at least one strain sensor 130 are arranged on the shaft portion 106. The above method includes the following steps: a step of obtaining sensor information from at least one acceleration sensor 120 and at least one strain sensor 130; a step of determining whether the milling tool 100 is rotating based on the sensor information from at least one acceleration sensor 120; and a step of determining whether the milling tool 100 is in contact with the workpiece 18 based on the sensor information from at least one strain sensor 130.

[0042] [Details of the embodiments of the present invention]

[0043] Next, with reference to the accompanying drawings, Figure 1 In addition, the same or corresponding parts are marked with the same reference numerals in the drawings without repeating their description. In addition, at least a part of the embodiments described below can also be arbitrarily combined.

[0044] (Overview of cutting system)

[0045] Figure 1 2 is a diagram showing an overview of a cutting system 50 according to the present embodiment. Figure 1 The cutting system 50 includes a milling cutter 100 and a management device 200. The milling cutter 100 is mounted on a machine tool 10 such as a machining center or a milling machine, and is used to perform cutting processing on a workpiece 18 as a cutting target.

[0046] Figure 1 The machine tool 10 of the example is a vertical machining center, and a milling tool 100 is mounted on a spindle 14, and the spindle 14 is provided with a machining head 12 that moves in the vertical direction (Z-axis direction). Figure 1 In the embodiment, the milling tool 100 includes a shaft portion 106 having a blade portion and a tool holder 105 for holding the shaft portion 106, and a portion of the tool holder 105 is mounted on the machine tool 10. In addition, the tool holder 105 may be omitted, and a Figure 7 As in the modified example described later, the cutting insert 160 (see Figure 7 ) is directly mounted on the machine tool 10. The milling cutter 100 is rotated with the Z-axis direction as the rotation axis by a motor (not shown) disposed on the spindle 14.

[0047] The workpiece 18 is arranged on a worktable 16 provided on a base 20. The worktable 16 is configured to be movable in the XY plane. By moving the worktable 16 and the processing head 12, the relative position of the milling tool 100 and the workpiece 18 is changed, and the rotating milling tool 100 is brought into contact with the workpiece 18, thereby cutting the workpiece 18.

[0048] In addition, Figure 1 In the description, a three-axis vertical machining center is used as an example of the machine tool 10, but the machine tool 10 may be a horizontal machining center in which a main axis is arranged in a horizontal direction, or may be a machine tool having four or more motion axes.

[0049] If through Figure 2 As will be described later, a plurality of sensors are mounted on the milling cutter 100. The force applied to the milling cutter 100 can be detected by the sensors.

[0050] The management device 200 uses the detection value of the sensor installed on the milling tool 100 to determine and manage the state of the milling tool 100. The management device 200 includes a communication device 210, a CPU (Central Processing Unit) 220 as a control device, a storage device 230, an input / output interface (I / F) 240, a display device 260, and an input device 270.

[0051] The communication device 210, the CPU 220, the storage device 230, and the input / output I / F 240 are connected to a common bus 250 and can transmit and receive signals to each other. The display device 260 and the input device 270 are connected to the input / output I / F 240 by wire or wirelessly.

[0052] The communication device 210 is a wireless communication device that wirelessly acquires detection values ​​of sensors mounted on the tool holder 105. The CPU 220 processes the detection values ​​of the sensors acquired by the communication device 210 by executing a program stored in the storage device 230, thereby determining the state of the milling tool 100.

[0053] The storage device 230 includes a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and a large-capacity storage device such as an HDD (Hard Disc Drive) or an SSD (Solid State Disk). The storage device 230 is used as a buffer when the CPU 220 performs processing, and is used to store programs executed by the CPU 220, detection values ​​of sensors, and / or calculation results obtained by the CPU 220.

[0054] The input device 270 is a pointing device such as a keyboard, a mouse, a trackball or a touch panel, and receives operation signals from the user. The display device 260 is typically a liquid crystal panel or an organic EL (ElectroLuminescence) panel, and displays the calculation results of the CPU 220 and the information stored in the storage device 230 to the user.

[0055] The input / output I / F 240 is an interface for connecting the display device 260 and the input device 270. A user operation signal is received from the input device 270 via the input / output I / F 240, and information for notifying the user is output to the display device 260.

[0056] (Purpose of this embodiment)

[0057] The milling cutters used in such working machines as mentioned above may sometimes experience abnormalities such as wear or damage to the cutting edge during use. If an abnormality occurs in the milling cutter, it may not be possible to properly cut the workpiece serving as the cutting object, resulting in reduced machining accuracy or damage to the workpiece or the cutter itself. In response to the above-mentioned issues, as shown in International Publication No. 2021 / 029099 (Patent Document 1), the following structure is known, namely, a plurality of sensors including acceleration sensors and strain sensors are provided in a tool holder for holding the milling cutter, and based on the data of physical quantities detected by the sensors, it is judged whether the cause of the cutting problem is caused by the milling cutter or the working machine.

[0058] In the system of Patent Document 1, the cause of the problem is determined by accumulating the measured data during the cutting process of the target machine tool for a predetermined period and analyzing the accumulated data. In this data analysis, it is useful to use information on the state of the milling tool (i.e., whether the tool is rotating or processing the workpiece) with respect to the accumulated continuous data of the sensor in order to accurately perform the analysis.

[0059] Therefore, in this embodiment, a method of determining the state of the milling tool based on data from an acceleration sensor and a strain sensor disposed on a tool holder will be described.

[0060] (Milling tool details)

[0061] Next, use Figure 2 and Figure 3 , details of the milling cutter 100 will be described. Figure 2 1 is a diagram showing a milling cutter 100 in which a shaft portion 106 is mounted on a cutter holder 105. Figure 3The diagram shows the arrangement of the sensors when the milling tool 100 is viewed from the positive direction of the Z axis.

[0062] The tool holder 105 includes a main body 110 mounted on the spindle 14 of the machine tool 10. One end of the main body 110 is mounted on the spindle 14. A shaft portion 106 is mounted on the other end of the main body 110.

[0063] The milling tool 100 is, for example, an end mill, a milling cutter, a drill, a reamer, a tap, etc., and cuts the workpiece 18 by rotating the tool itself. Figure 2 In the figure, the milling tool 100 is an end mill, and a blade is provided at a first end 107 of a substantially cylindrical shaft 106, and a second end 108 of the shaft 106 is mounted on a tool holder 105. The blade may be formed on the shaft 106, or a detachable blade tip may be mounted on the shaft 106. By driving a motor (not shown) provided on the spindle 14, the milling tool 100 rotates in a clockwise (CW: ClockWise) direction around the rotation axis CL when viewed from the positive direction of the Z axis, and the workpiece 18 is cut by bringing the blade into contact with the workpiece 18.

[0064] like Figure 3 As shown, a plurality of sensors 120 and 130 are installed around the shaft 106 on the tool holder 105. In this embodiment, the plurality of sensors include four acceleration sensors 120 and four strain sensors 130. In addition, a communication device 140 and a battery 150 are arranged on a substrate not shown in the figure on the tool holder 105. The communication device 140 is a wireless communication device driven by the battery 150. The communication device 140 can communicate with the communication device 210 of the management device 200 by wireless, and transmit the detection values ​​detected by the sensors 120 and 130 to the management device 200 by wireless.

[0065] In addition, the sensors 120 and 130 may be directly mounted on the shaft portion 106, or may be arranged on the tool holder 105 that can measure the deformation state of the milling tool 100. Figure 3 In the figure, for the sake of convenience, the state where the sensors 120 and 130 are directly mounted on the shaft portion 106 is described.

[0066] The four acceleration sensors 120 are arranged on the surface of the shaft 106 at positions at which the intervals in the circumferential direction are 90° in the central part of the acceleration sensor 120. That is, the four acceleration sensors 120 are arranged on concentric circles centered on the rotation axis CL of the shaft 106 in the same plane with the rotation axis CL of the shaft 106 as the normal line. When viewed from above in the Z-axis direction, two of the four acceleration sensors 120 are arranged point-symmetrically with respect to the rotation axis CL of the milling tool 100. In addition, the remaining two of the four acceleration sensors 120 are also arranged point-symmetrically with respect to the rotation axis CL of the milling tool 100. Each acceleration sensor 120 has a measurement sensitivity at least in the radial direction, and can detect the centrifugal acceleration when the milling tool 100 rotates.

[0067] The four strain sensors 130 include strain sensors 130A to 130D. The strain sensors 130A to 130D are arranged on concentric circles centered on the rotation axis CL of the shaft 106 in the same plane as the acceleration sensor 120, with the rotation axis CL of the shaft 106 as the normal line. In addition, the strain sensors 130A to 130D are arranged on the surface of the shaft 106 at positions where the intervals in the circumferential direction are 90° in the center of the strain sensors. Figure 3 In the example, the strain sensors 130A to 130D are each respectively arranged between two adjacent acceleration sensors. In addition, when the acceleration sensor 120 and the strain sensor 130 are not arranged on the same plane, they can also be arranged so that the acceleration sensor 120 and the strain sensor 130 are at the same position when viewed from the Z-axis direction. The strain sensor 130A and the strain sensor 130C are arranged point-symmetrically with respect to the rotation axis CL of the milling tool 100. In addition, the strain sensor 130B and the strain sensor 130D are also arranged point-symmetrically with respect to the rotation axis CL of the milling tool 100.

[0068] The strain sensors 130A to 130C are configured to have measurement sensitivity in the vertical direction (Z-axis direction). Therefore, the strain sensors 130A to 130C can detect the deflection of the shaft 106 when a force perpendicular to the Z-axis direction acts on the milling tool 100. On the other hand, the strain sensor 130D is configured to have measurement sensitivity in the circumferential direction (shear direction). Therefore, the force acting on the milling tool 100 in the circumferential direction, that is, the rotational torque, can be detected by the strain sensor 130D.

[0069] (Determination of the status of the milling tool)

[0070] Figure 41 is a diagram showing an example of detection signals of the sensors 120 and 130 when the rotation speed of the milling cutter 100 is changed in a no-load state. Figure 4 The upper part of FIG. 1 shows the strain detected by the strain sensor 130 (lines LN10, LN20). Figure 4 The lower part of shows the acceleration (line LN30) detected by the acceleration sensor 120. The horizontal axis shows time. At time t1 to t5, the rotation speed of the milling tool 100 increases step by step with time, and at time t6 to t11, the rotation speed of the milling tool 100 decreases step by step with time. Figure 4 In the upper part of FIG. 1 , line LN10 shows the vertical strain in the vertical direction (Z-axis direction) obtained by the strain sensors 130A to 130C. In addition, line LN20 shows the circumferential strain obtained by the strain sensor 130D.

[0071] according to Figure 4 The vertical strain detected by the strain sensors 130A to 130C changes in accordance with the rotation speed. If the rotation speed increases, the vertical strain also increases, and if the rotation speed decreases, the vertical strain also decreases. This is because the milling tool 100 (and / or the tool holder 105) expands in the vertical direction as the milling tool 100 rotates, resulting in strain. On the other hand, the circumferential shear strain detected by the strain sensor 130D hardly changes with respect to the rotation speed.

[0072] In addition, regarding the centrifugal acceleration detected by the acceleration sensor 120, due to the centrifugal force generated by the rotation of the milling tool 100, if the rotation speed increases, the centrifugal acceleration also increases, and if the rotation speed decreases, the centrifugal acceleration also decreases.

[0073] As can be seen from the above characteristics, it is possible to determine whether the milling tool 100 is rotating based on the vertical strain obtained by the strain sensors 130A to 130C and the centrifugal acceleration data obtained by the acceleration sensor 120. However, since the vertical strain can be detected even when the milling tool 100 is deformed due to external force acting on it during cutting, it can be said that it is appropriate to use the centrifugal acceleration data detected by the acceleration sensor 120 when determining whether the milling tool 100 is rotating.

[0074] On the other hand, when the milling cutter 100 is in the process of machining, due to the contact between the blade and the workpiece 18, an external force is applied in at least one of the rotation axis direction and the direction orthogonal to the rotation axis of the milling cutter 100. Therefore, when machining is in progress, strain can be detected by any one of the strain sensors 130A to 130D. Here, as shown in FIG. Figure 4As shown, regarding the strain sensors 130A to 130C for detecting the vertical strain in the Z-axis direction, even when there is no reaction force from the workpiece 18, if the milling tool 100 is rotating, the strain will be detected, so it is impossible to use this sensor to determine whether the milling tool 100 is in processing. Therefore, by using the shear strain (i.e., rotational torque) detected by the strain sensor 130D, it is possible to determine whether the milling tool 100 is in contact with the workpiece 18, that is, whether the milling tool 100 is in processing, without being affected by the rotation of the milling tool 100.

[0075] As described above, in order to determine the state (rotating / machining) of the milling cutter 100 , it is necessary to arrange at least one strain sensor for detecting shear strain and one acceleration sensor for detecting centrifugal acceleration.

[0076] Figure 5 1 is a diagram for explaining the state of the milling cutter 100 based on the detection signals of each sensor. Figure 4 As described above, whether the milling cutter 100 is rotating can be determined by using the centrifugal acceleration detected by the acceleration sensor 120. Also, whether cutting is performed can be determined by using the shear strain detected by the strain sensor 130D.

[0077] By combining these detection data, the state of the milling tool 100 can be detected as follows. First, when both the centrifugal acceleration obtained by the acceleration sensor 120 and the shear strain obtained by the strain sensor 130D are detected, it can be determined that the workpiece 18 is actually being cut by the milling tool 100.

[0078] Next, when the centrifugal acceleration obtained by the acceleration sensor 120 is detected but the shear strain obtained by the strain sensor 130D is not detected, it can be determined that the milling cutter 100 is in a state of only rotating in a no-load state (idle state). In addition, when both the centrifugal acceleration obtained by the acceleration sensor 120 and the shear strain obtained by the strain sensor 130D are not detected, it can be determined that the milling cutter 100 is stopped.

[0079] In addition, when the centrifugal acceleration obtained by the acceleration sensor 120 is not detected, but the shear strain obtained by the strain sensor 130D is detected, since the milling tool 100 is in a stopped state and an external force is applied, it is a state that does not actually occur in normal operation. Such a state is, for example, an abnormal state such as a jamming of the milling tool 100 due to an excessive feed amount, or a collision between the milling tool 100 and the workpiece 18 when the tool is stopped, or a state in which an abnormality occurs in the sensor. Therefore, when the centrifugal acceleration is not detected but the shear strain is detected, it can be determined that an abnormal state has occurred.

[0080] Furthermore, when the tool holder 105 is equipped with a sensor, when the shaft 106 as the tool body is replaced, it is possible that the centrifugal acceleration is not detected but the shear strain is detected. In addition, when the shaft 106 is equipped with a sensor and the front end of the shaft 106 is a milling tool with a blade replacement type, when the blade is replaced, it is possible that the centrifugal acceleration is not detected but the shear strain is detected. That is, in addition to recording the abnormal state of the tool, the timing of replacing the tool can also be recorded.

[0081] Furthermore, the state of the milling tool 100 determined using the centrifugal acceleration obtained by the acceleration sensor 120 and the shear strain obtained by the strain sensor 130D can also be applied to the following processing.

[0082] (1) Zero point correction of strain sensor.

[0083] As described above, when the shear strain obtained by the strain sensor 130D is not detected, that is, when the milling cutter 100 is in "only rotational motion" or "stopped" with no external force acting on it, the strain sensors 130A to 130C should not detect vertical strain. However, due to the occurrence of thermal strain caused by the ambient temperature or the temperature distribution of the cutting fluid, or due to Figure 4 Since the centrifugal force generated by the rotation shown causes expansion strain, the values ​​of the strain sensors 130A to 130C may be detected.

[0084] Therefore, when it is determined that the state is “only rotating” or “stopped”, the deviation of the vertical strain data can be eliminated by performing zero point correction processing on the measurement values ​​of the strain sensors 130A to 130C.

[0085] (2) Additional label processing for accumulated data.

[0086] The determination of a problem of the milling tool 100 is performed by accumulating continuous measurement data and analyzing the accumulated data as shown in Patent Document 1. However, it is difficult to grasp the relationship between changes in sensor data and changes in tool status based on the measurement data as they are.

[0087] Therefore, the Figure 5 The information on the tool status determined according to the classification criteria shown is stored by adding label information on the tool status to the measurement data, thereby making it easy to understand the relationship between changes in sensor data and changes in the tool status in subsequent analysis, and facilitating data organization.

[0088] (3) Data classification and processing for each product.

[0089] In the machine tool 10, processing is performed in a pre-programmed sequence, and generally, the processing of the same product is performed continuously. Therefore, when processing one product (cutting object), it is possible to know in advance how the tool state changes from the start of processing to the completion of processing based on the predetermined processing sequence. In other words, if the labeling processing of the measurement data described in (2) can be performed, it is possible to classify which range of data groups of continuous measurement data corresponds to one product based on the state change of the milling tool.

[0090] On the contrary, for example, when the range of a data group from the start of processing to the completion of processing for each product can be identified in advance by a signal indicating a product change adjustment of the workpiece 18, and when there is a difference between the state transition of the milling tool determined in the data group based on the measurement data (the second data) and the state transition pattern of the milling tool (the first data) pre-stored for the product, it can be determined that the corresponding product may have a processing abnormality and the user can be notified of the abnormality.

[0091] Figure 6 This is a flowchart for explaining the state determination process of the milling tool 100 executed by the management device 200 of the cutting system 50 according to the present embodiment. Figure 6 The processing shown is realized by the CPU 220 executing a program read from the storage device 230 in the management device 200 . Figure 6 The processing may be performed offline on measurement data accumulated in advance, or may be performed online on data measured during actual machining of the workpiece 18 .

[0092] In addition, you can also Figure 6Part or all of the described processing is implemented by hardware such as a semiconductor integrated circuit. In addition, the program executed by the CPU 220 can be installed from an external server device or the like. Alternatively, the program can also be circulated in a state stored in a storage medium such as a CD-ROM or a semiconductor memory.

[0093] Reference Figure 6 , the management device 200 obtains the sensor data sent from the tool holder 105 or the sensor data accumulated in the storage device 230 in step (hereinafter, the step is abbreviated as "S") 100. Moreover, the management device 200 determines whether the centrifugal acceleration is detected, that is, whether the milling tool 100 is "rotating" based on the measurement data of the acceleration sensor 120 in S110. Specifically, the management device 200 determines that the milling tool 100 is "rotating" when the centrifugal acceleration detected by the acceleration sensor 120 is greater than the first threshold value, and determines that the milling tool 100 is "stopped" when the centrifugal acceleration detected by the acceleration sensor 120 is less than the first threshold value.

[0094] When centrifugal acceleration is detected and the milling cutter 100 is "rotating" (S110 is YES), the process proceeds to S120. In S120, the management device 200 determines whether shear strain is detected, that is, whether an external force acts on the milling cutter 100 and a torque is generated, based on the measurement data of the strain sensor 130D. Specifically, when the shear strain detected by the strain sensor 130D is greater than the second threshold, the management device 200 determines that the milling cutter 100 is in contact with the workpiece 18 and a torque is generated, and when the detected shear strain is less than the second threshold, it is determined that the milling cutter 100 is not in contact with the workpiece 18 and no torque is generated.

[0095] When shear strain is detected and the milling cutter 100 generates torque (S120 is YES), the process proceeds to S130 and the management device 200 determines that the tool state is “cutting.” Furthermore, the management device 200 adds a label indicating “cutting” to the target data and stores it in the storage device 230 in S140.

[0096] On the other hand, when the milling cutter 100 does not generate torque (S120 is NO), the process proceeds to S135, and the management device 200 determines that the milling cutter 100 is in "idle rotation" where only the rotation action is performed. When the process is performed online, the management device 200 can then perform zero point correction processing related to the strain sensors 130A to 130D that measure the vertical strain in S136. In addition, when the process is performed offline, the process of S136 is skipped. Then, the management device 200 assigns a label indicating "idle rotation" to the object data in S140 and stores it in the storage device 230.

[0097] On the other hand, when the centrifugal acceleration is not detected and the milling cutter 100 is not "rotating" (S110 is NO), the process proceeds to S170, and the management device 200 determines whether torque is generated in the milling cutter 100 based on the measurement data of the strain sensor 130D. When the milling cutter 100 does not generate torque (S170 is NO), the process proceeds to S180, and the management device 200 determines that the milling cutter 100 is "stopped". In addition, the management device 200 assigns a label indicating "stopped" to the target data in S140 and stores it in the storage device 230.

[0098] On the other hand, when the milling cutter 100 generates torque even though the centrifugal acceleration is not detected (S170 is YES), the process proceeds to S185, and the management device 200 determines that the milling cutter 100 is in an "abnormal state" and outputs an alarm to the user. Then, the management device 200 assigns a label indicating "abnormal state" to the target data in S140 and stores it in the storage device 230.

[0099] If data is stored in S140, the process proceeds to S150, and the management device 200 determines whether the processing using the milling cutter 100 is completed. If the processing is not completed (S150 is NO), the process returns to S100, and the management device 200 repeats the above-mentioned processing from S100 to S140. On the other hand, if the processing is completed (S150 is YES), the management device 200 ends the status determination process.

[0100] In addition, although Figure 6Although not shown, when the processing is performed in an offline manner, in S150, the management device 200 determines whether the processing related to all sensor data to be processed in the storage device 230 is completed. And, when there is data to be processed (S150 is NO), the processing returns to S100. On the other hand, when the processing related to all data is completed (S150 is YES), the management device 200 ends the status determination processing.

[0101] By performing control according to the above-described processing, the state of the milling tool attached to the tool holder can be determined based on the data of the acceleration sensor and the strain sensor attached to the tool holder.

[0102] (Variation example of milling cutter)

[0103] Figure 7 1 is a diagram showing a milling cutter 100A according to a modified example. The milling cutter 100A does not include a tool holder like the milling cutter 100 according to the first embodiment, but is configured such that a shaft portion is attached to a main shaft of a machine tool including a tool holder.

[0104] Reference Figure 7 The milling tool 100A includes a shaft 106A and an acceleration sensor 120 and a strain sensor 130 installed around the shaft 106A. The acceleration sensor 120 and the strain sensor 130 are housed in a housing 170 provided on the shaft 106A. The acceleration sensor 120 and the strain sensor 130 are arranged at equal intervals in the circumferential direction of the shaft 106A, similarly to the milling tool 100 of the first embodiment. Figure 7 Although not shown, there is also a Figure 2 A communication device 140 and a battery 150 are shown.

[0105] A replaceable cutting insert (a throwaway insert) 160 is mounted on a first end portion 107 of the shaft portion 106A. A second end portion 108 of the shaft portion 106A is mounted on a spindle 14 of the machine tool 10 having a tool holder.

[0106] As described above, even in a milling tool mounted on a spindle including a tool holder, by disposing an acceleration sensor and a strain sensor on the shaft portion of the milling tool, the state of the milling tool can be determined based on the data of the sensors.

[0107] The embodiments disclosed this time should be considered in all respects as illustrative rather than restrictive. The scope of the present invention is indicated not by the description of the above embodiments but by the claims, and includes all modifications within the meaning and scope equivalent to the claims.

[0108] Description of the label

[0109] 10 working machine, 12 processing head, 14 main shaft, 16 worktable, 18 workpiece, 20 base, 50 cutting system, 100, 100A milling tool, 105 tool holder, 106, 106A shaft, 107 first end, 108 second end, 110 main body, 120 acceleration sensor, 130, 130A~130D strain sensor, 140, 210 communication device, 150 battery, 160 cutting blade, 170 housing, 200 management device, 220 CPU, 230 storage device, 240 input and output interface, 250 bus, 260 display device, 270 input device, CL rotating axis.

Claims

1. A cutting system comprising: A milling tool, comprising a shaft portion having a first end portion and a second end portion, wherein a blade portion for cutting a workpiece is provided at the first end portion, and the second end portion is mounted on a machine tool; a plurality of sensors mounted on the shaft; as well as a management device for determining the state of the milling tool based on sensor information from the plurality of sensors, The plurality of sensors include: At least 1 accelerometer; and At least 1 strain sensor, The management device, Based on the sensor information from the at least one acceleration sensor, determining whether the milling cutter is rotating or not, Based on the sensor information from the at least one strain sensor, it is determined whether the milling tool is in contact with the workpiece.

2. The cutting system according to claim 1, wherein: The milling cutter rotates with the axial direction of the shaft portion as a rotation axis. The at least one acceleration sensor is configured to detect the centrifugal acceleration of the milling tool.

3. The cutting system according to claim 2, wherein: The multiple sensors include multiple acceleration sensors, The plurality of acceleration sensors are arranged on concentric circles centered on the rotation axis in the same plane with the rotation axis of the shaft portion as a normal line.

4. The cutting system according to claim 3, wherein: The plurality of acceleration sensors include four acceleration sensors, and the four acceleration sensors are disposed at a central portion of the acceleration sensor at intervals of 90° in the circumferential direction of the shaft portion.

5. The cutting system according to any one of claims 1 to 4, wherein: The management device, When the acceleration detected by the at least one acceleration sensor is greater than a first threshold value, it is determined that the milling tool is rotating. When the acceleration detected by the at least one acceleration sensor is smaller than the first threshold value, it is determined that the milling tool is stopped.

6. The cutting system according to claim 1, wherein: The milling cutter rotates with the axial direction of the shaft portion as a rotation axis. The at least one strain sensor is configured to detect a strain in a circumferential direction of the shaft portion.

7. The cutting system according to claim 6, wherein: The plurality of sensors include a plurality of strain sensors, The plurality of strain sensors are arranged on concentric circles centered on the rotation axis in the same plane having the rotation axis of the shaft portion as a normal line.

8. The cutting system according to claim 7, wherein: The plurality of strain sensors include four strain sensors, and the four strain sensors are disposed at positions at which intervals of 90° are formed in the central portion of the strain sensor in the circumferential direction of the shaft portion.

9. The cutting system according to any one of claims 6 to 8, wherein: The management device, When the strain in the circumferential direction of the shaft portion detected by the at least one strain sensor is greater than a second threshold value, it is determined that the milling tool is in contact with the workpiece, When the strain in the circumferential direction of the shaft portion detected by the at least one strain sensor is smaller than the second threshold value, it is determined that the milling tool is not in contact with the workpiece.

10. The cutting system according to claim 1, wherein: The milling cutter rotates with the axial direction of the shaft portion as a rotation axis. The at least one acceleration sensor and the at least one strain sensor are alternately arranged in the circumferential direction of the shaft portion.

11. The cutting system according to claim 1, wherein: The management device determines whether the milling tool is in cutting based on sensor information from the at least one acceleration sensor and sensor information from the at least one strain sensor.

12. The cutting system according to claim 11, wherein: The management device determines that the milling tool is cutting when the acceleration detected by the at least one acceleration sensor is greater than a first threshold value and the strain in the circumferential direction of the shaft portion detected by the at least one strain sensor is greater than a second threshold value.

13. The cutting system according to claim 11, wherein: The management device determines that the milling tool is in an abnormal state when the acceleration detected by the at least one acceleration sensor is smaller than a first threshold value and the circumferential strain of the shaft portion detected by the at least one strain sensor is larger than a second threshold value.

14. The cutting system according to claim 13, wherein: When determining that the milling tool is in an abnormal state, the management device notifies a user of the abnormal state.

15. The cutting system according to claim 11, wherein: The management device determines that the milling tool is rotating without cutting when the acceleration detected by the at least one acceleration sensor is greater than a first threshold and the strain in the circumferential direction of the shaft portion detected by the at least one strain sensor is less than a second threshold.

16. The cutting system of claim 1, wherein: The at least one strain sensor includes a first sensor for detecting a strain in a circumferential direction of the shaft portion, and a second sensor for detecting a strain in an axial direction of the shaft portion. The management device corrects the measurement value of the second sensor to zero when the strain in the circumferential direction of the shaft portion detected by the first sensor becomes smaller than a second threshold value.

17. The cutting system according to any one of claims 1 to 16, wherein: The management device further comprises a storage device, wherein the storage device is used to store sensor information from the plurality of sensors. The management device adds tag information corresponding to the state of the milling tool to the sensor information from the plurality of sensors and stores the tag information in the storage device.

18. The cutting system of claim 17, wherein: The management device pre-stores the state transition of the milling tool from the start of machining to the completion of machining of the workpiece, and classifies the sensor information stored in the storage device into machining data groups for each workpiece based on the state transition and the tag information.

19. A method for determining the state of a milling tool, The milling tool is equipped with at least one acceleration sensor and at least one strain sensor. The method comprises the following steps: The step of acquiring sensor information from the at least one acceleration sensor and the at least one strain sensor; A step of determining whether the milling cutter is not rotating based on sensor information from the at least one acceleration sensor; and A step of determining whether or not the milling tool is in contact with a workpiece based on sensor information from the at least one strain sensor.

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