Processing equipment and cutting tools

Abstract

We provide technology for monitoring the processing status. [Solution] The rotating mechanism 11 rotates the spindle 10 to which a cutting tool 20 or workpiece 30 is attached, the cutting tool having an insulating layer on a part of its surface or having an insulating layer or high-resistance layer inside the cutting tool. The movement control unit 102 controls the relative movement of the cutting tool 20 with respect to the workpiece 30. The monitoring unit 104 monitors the machining state during machining using the thermoelectric voltage generated in the contact area where the conductive area on the surface of the cutting tool 20, where an insulating layer is not provided, comes into contact with the workpiece 30.

Description

Technical Field

[0001] The present disclosure relates to a processing apparatus and a cutting tool for monitoring a processing state.

Background Art

[0002] As a method for measuring the temperature of a tool edge during cutting, the tool-workpiece thermocouple method is known. The tool-workpiece thermocouple method utilizes the Seebeck effect in which a thermoelectromotive force is generated between the contacts of a loop made of two types of conductors when a temperature difference occurs between the contacts, causing an electric current to flow through the loop, and measures the tool edge temperature from the thermoelectromotive force generated between the tool and the workpiece. Since the thermoelectromotive force is determined by the temperatures of the two contacts and the materials of the two types of conductors, the edge temperature can be obtained from a previously created temperature calibration curve by measuring the thermoelectromotive force. Although the main component of the cutting tool material is generally non-metallic, in many cases, it contains a conductive binder or the like, so the tool-workpiece thermocouple method can be utilized.

[0003] Patent Document 1 discloses a cutting apparatus that measures the voltage between a contact structure that contacts the rotation center of a spindle and the contact point between the tool and the workpiece in order to implement the tool-workpiece thermocouple method. This contact structure has a first conductor component fixed to the end of the spindle and extending along the axis of the spindle, and a second conductor component that contacts the rotation center of the first conductor component.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The tool-workpiece thermocouple method is a practical technique that allows for relatively simple measurement of cutting edge temperature without modifying the tool or workpiece. However, conventional tool-workpiece thermocouple methods measure the average temperature of the area where the tool and workpiece are in contact, and it is difficult to say that they accurately measure the temperature of the area to be monitored.

[0006] For example, when monitoring the problem of adhesion between the tool flank and the workpiece surface causing tearing or deterioration of the surface, it is desirable to accurately measure the contact temperature between the flank and the surface, which greatly influences the adhesion phenomenon. However, conventional tool-workpiece thermocouple methods measure the average temperature of the tool rake face in contact with the chip and the tool flank face in contact with the surface, and therefore cannot be said to accurately measure the contact temperature between the flank and the surface to be monitored. For this reason, the development of a technology that can accurately measure the contact temperature of the area to be monitored (for example, the flank) is desired.

[0007] Furthermore, regarding the monitoring of the processing state, there is a high demand not only for accuracy of measurement but also for ease of measurement. This disclosure is made in view of these circumstances, and its purpose is to provide a technology for monitoring the processing state with high accuracy or ease of use. [Means for solving the problem]

[0008] A machining apparatus according to one aspect of the present disclosure includes a rotating mechanism for rotating a spindle to which a cutting tool having an insulating layer on a portion of its surface or an insulating layer or high-resistance layer inside the cutting tool, or a workpiece, is attached; a moving control unit for controlling the relative movement of the cutting tool with respect to the workpiece; and a monitoring unit for monitoring the machining state during machining using the thermoelectric voltage generated in a contact area where a conductive area on the surface of the cutting tool, where an insulating layer is not provided, comes into contact with the workpiece.

[0009] A machining apparatus in another aspect of the present disclosure includes a rotating mechanism for rotating a spindle to which a cutting tool having an insulating layer or a high-resistance layer on at least a portion of the surface of the cutting tool and / or inside the cutting tool, or a workpiece to be cut, is attached; a moving control unit for controlling the relative movement of the cutting tool with respect to the workpiece; and a monitoring unit for monitoring the machining state using the contact resistance in the contact area where the surface of the cutting tool and the workpiece come into contact during machining.

[0010] A cutting tool in another aspect of the present disclosure comprises an insulating layer or high-resistance layer provided on at least a portion of the surface of the cutting tool and / or inside it, and an electrical contact for connecting a circuit for measuring the thermoelectric power generated in the contact area between the cutting tool and the workpiece or the contact resistance in the contact area.

[0011] Furthermore, any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, etc., are also valid as aspects of this disclosure. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram showing the schematic configuration of the processing apparatus of Embodiment 1. [Figure 2] This figure shows an example of a contact structure. [Figure 3] This figure shows an example of a cutting tool used for machining monitoring in Embodiment 1. [Figure 4] This figure shows the measurement results of the thermoelectric power between the flank and the workpiece. [Figure 5] This figure shows a modified example of the cutting tool used for machining monitoring in Embodiment 1. [Figure 6] This figure shows the measurement results of the thermoelectric power between the flank and the workpiece. [Figure 7] This figure shows the measurement results of the thermoelectric power between the rake face and the workpiece. [Figure 8] This figure shows the schematic configuration of the processing apparatus according to Embodiment 2. [Figure 9] This figure shows an example of a cutting tool used for machining monitoring in Embodiment 2. [Figure 10]It is a diagram showing the measurement results of the difference in thermal power. [Figure 11] It is a diagram showing another example of the cutting tool used for the machining monitoring of Embodiment 2. [Figure 12] It is a diagram showing an example of the cutting tool used for the machining monitoring of Embodiment 3. [Figure 13] It is a diagram showing another example of the cutting tool used for the machining monitoring of Embodiment 3. [Figure 14] It is a diagram showing another example of the cutting tool used for the machining monitoring of Embodiment 3. [Figure 15] It is a diagram showing another example of the cutting tool used for the machining monitoring of Embodiment 3. [Figure 16] It is a diagram showing another example of the cutting tool used for the machining monitoring of Embodiment 3.

MODE FOR CARRYING OUT THE INVENTION

[0013] <Embodiment 1> FIG. 1 shows a schematic configuration of the machining apparatus 1a of Embodiment 1. The machining apparatus 1a of Embodiment 1 is a lathe that rotates a workpiece 30 attached to a spindle 10 via a chuck 31 and inserts a cutting edge of a cutting tool 20 into the rotating workpiece 30. The cutting edge of the cutting tool 20 and the workpiece 30 are formed of different materials and are assumed to be different types of conductors, and the cutting edge of the cutting tool 20 cuts the workpiece 30 at the cutting point 50.

[0014] The machining apparatus 1a includes a spindle housing 12 and a feed mechanism 21 that relatively moves the cutting tool 20 with respect to the workpiece 30 on a bed 2. The cutting tool 20 is fixed to a tool fixing portion 22, and the tool fixing portion 22 is movably supported by the feed mechanism 21. In the machining apparatus 1a of Embodiment 1, the feed mechanism 21 has a mechanism for moving the tool fixing portion 22 in the X-axis, Y-axis, and Z-axis directions, and relatively moves the cutting tool 20 with respect to the workpiece 30. The feed mechanism 21 may include motors and ball screws for each axis. In another example of the machining apparatus 1a, the cutting tool 20 may be fixed to the spindle 10, and the feed mechanism may move the workpiece 30 relative to the cutting tool 20.

[0015] The main shaft 10 is rotatably supported by the main shaft housing 12. Specifically, metal or ceramic bearings 13a and 13b fixed to the main shaft housing 12 rotatably support the main shaft 10. The rotation mechanism 11 includes a mechanism for rotating the main shaft 10 and has a motor and a transmission structure for transmitting the rotational power of the motor to the main shaft 10. The transmission structure may include a V-belt or gears for transmitting the rotational power of the motor to the main shaft 10. The rotation mechanism 11 may be a built-in motor incorporated in the main shaft 10 to directly drive the main shaft 10.

[0016] The machining apparatus 1a has a measurement circuit 40a for measuring the thermoelectromotive force generated between the cutting tool 20 and the workpiece 30 during cutting by the tool-workpiece thermocouple method. The cutting point 50 is a contact area where the cutting edge of the cutting tool 20, which is a different conductor, contacts the workpiece 30. During cutting, the temperature at the cutting point 50 becomes high, and a thermoelectromotive force (voltage) is generated between the cutting tool 20 and the workpiece 30. The measurement circuit 40a includes a contact structure 41 electrically connected to the rotating main shaft 10, a conducting wire 42 electrically connected to the contact structure 41, a conducting wire 43 electrically connected to the electrical contact 35 of the cutting tool 20, an electrical resistance 44 provided between the conducting wire 42 and the conducting wire 43, and a measurement unit 45 for measuring the thermoelectromotive force (voltage) between the contact structure 41 and the cutting point 50. The measurement unit 45 may be a voltmeter. In the machining apparatus 1a, when not cutting, the cutting edge of the cutting tool 20 and the workpiece 30 are separated, and the electrical circuit is open. Therefore, if the electrical resistance 44 is not provided, the measurement unit 45 will measure the ambient electromagnetic waves as noise. To suppress the measurement of this noise during non-cutting, the electrical resistance 44 is provided in the embodiment. However, if the measurement unit 45 monitors only the thermoelectromotive force between the contact structure 41 and the cutting point 50 during cutting, the electrical resistance 44 may be removed from the measurement circuit 40a so that only the thermoelectromotive force is applied to the measurement unit 45. For the same reason, the electrical resistances 44, 44a, and 44b may also be removed in FIGS. 3, 5, 8, 9, and 11 shown below.

[0017] The control unit 100 includes a rotation control unit 101 that controls the rotation of the spindle 10 by the rotation mechanism 11, a movement control unit 102 that controls the relative movement between the cutting tool 20 and the workpiece 30 by the feed mechanism 21, an acquisition unit 103 that acquires the voltage measured by the measurement unit 45, and a monitoring unit 104 that monitors the machining status using the voltage acquired by the acquisition unit 103. The monitoring unit 104 can determine the contact temperature from the voltage measured by the measurement unit 45 using a temperature calibration curve or temperature calibration table, etc., to calibrate the voltage to the contact temperature (cutting edge temperature at the cutting point 50).

[0018] Each element described as a functional block of the control unit 100 can be composed of, in hardware terms, circuit blocks, memory, other LSIs, CPUs, etc., and in software terms, it is implemented by system software, application programs loaded into memory, etc. Therefore, it will be understood by those skilled in the art that these functional blocks can be implemented in various ways by hardware alone, software alone, or a combination thereof, and are not limited to any one of these.

[0019] The contact structure 41 contacts the rotation center of the spindle 10 to extract an electrical signal. Since the peripheral speed of the rotation center is theoretically zero, the contact structure 41 contacting the rotation center of the spindle 10 suppresses wear at the contact point. In Figure 1, the workpiece 30 is attached to the tip side of the spindle 10 (right side in Figure 1) via the chuck 31, so it is preferable that the contact structure 41 contacts the rotation center of the spindle 10 at the rear end side of the spindle 10 (left side in Figure 1). By positioning the contact structure 41 on the rear end side of the spindle 10, opposite to the tip side where the workpiece 30 is attached, the contact structure 41 can stably contact the rotation center of the spindle 10 and extract an electrical signal regardless of the cutting conditions.

[0020] Figure 2 shows an example of a contact structure 41. The contact structure 41 has a first conductive component 41a fixed to the end of the main shaft 10 and extending along the axis of the main shaft 10, and a second conductive component 41b in contact with the first conductive component 41a. The end of the conductor 42 is connected to the second conductive component 41b. The first conductive component 41a may be screwed to the rear end face of the main shaft 10, or it may be fixed by another coupling means. The first conductive component 41a and the second conductive component 41b may be formed of copper-based, silver-based, gold-based, graphite-based material (or an alloy containing them).

[0021] The first conductive component 41a abuts against the second conductive component 41b on an axis passing through the rotation center of the main shaft 10. The first conductive component 41a may be a round bar member with a circular cross-section. Preferably, the first conductive component 41a has a narrow diameter portion that tapers towards the second conductive component 41b, thereby reducing the diameter of the area that abuts against the second conductive component 41b. This reduces wear on the contact area between the first conductive component 41a and the second conductive component 41b when the main shaft 10 and the first conductive component 41a rotate. For example, the diameter of the contact area is preferably 1 mm or less. The first conductive component 41a may also be a rod-shaped member with a polygonal cross-section, and preferably has an inclined portion that gradually reduces its cross-sectional area towards the second conductive component 41b.

[0022] Furthermore, the first conductive component 41a may be a conical or pyramidal member, rather than a rod-shaped member. Regardless of the shape of the first conductive component 41a, it is preferable that it contacts the second conductive component 41b on the axis passing through the rotation center of the main shaft 10, and that the area of ​​the contact region be smaller than the area connected to the main shaft 10.

[0023] In the machining apparatus 1a, the electrical signal from the workpiece 30 is taken from a contact structure 41 that contacts the rear end of the spindle 10, so the spindle 10 and the spindle housing 12 need to be electrically insulated. If the bearings 13a and 13b are made of metal, insulation between the spindle 10 and the spindle housing 12 can be achieved by interposing an insulating component between the spindle 10 and the spindle housing 12.

[0024] The Discloser has found that when the spindle 10 rotates at a predetermined rotational speed RS or higher, a fluid lubrication state is created in the metal bearings 13a and 13b by the lubricating oil, causing a phenomenon in which the spindle 10 and the spindle housing 12 no longer conduct electricity. Utilizing this phenomenon, in the machining apparatus 1a, when the rotation control unit 101 rotates the spindle 10 at a rotational speed RS or higher, the movement control unit 102 controls the feed mechanism 21 to cause the cutting edge of the cutting tool 20 to cut into the workpiece 30, and the monitoring unit 104 monitors the machining state using the thermoelectric voltage (voltage) measured by the measuring unit 45. The rotational speed RS is determined by the bearings, but is approximately several hundred revolutions per minute. Thus, in the machining apparatus 1a, when the measuring unit 45 measures the thermoelectric voltage, the spindle 10 is rotated at a rotational speed RS or higher, thereby achieving insulation between the spindle 10 and the spindle housing 12 without adding insulating components between them.

[0025] When the measuring unit 45 measures the thermoelectric voltage, the main shaft 10 and the rotating mechanism 11 also need to be electrically insulated. For example, if the rotating mechanism 11 uses a V-belt as a power transmission structure, the main shaft 10 and the rotating mechanism 11 may be electrically insulated by forming the V-belt from an insulating material such as rubber. Alternatively, if the rotating mechanism 11 uses gears as a power transmission structure, the main shaft 10 and the rotating mechanism 11 may be electrically insulated by creating a fluid lubrication state between the rotating gears and interposing lubricating oil between the meshing teeth.

[0026] In the processing apparatus 1a, the conductor 43 is connected to an electrical contact 35 provided on the cutting tool 20 to extract an electrical signal. In order to stably extract the electrical signal from the cutting tool 20, it is preferable that the cutting tool 20 be fixed to the tool fixing part 22 via an insulating component. For example, if the tool fixing part 22 clamps and fixes the cutting tool 20, the cutting tool 20 and the tool fixing part 22 may be electrically insulated by insulating the clamping surface. Alternatively, the cutting tool 20 and the tool fixing part 22 may be electrically insulated by interposing an insulating component between the clamping surface of the tool fixing part 22 and the cutting tool 20.

[0027] Figure 3 shows an example of a cutting tool 20 used for machining monitoring in Embodiment 1. For convenience of explanation, in Figure 3, the conductor 42 in the measurement circuit 40a is connected to an arbitrary position on the workpiece 30, but as shown in Figure 1, it is preferable that the conductor 42 is electrically connected to the workpiece 30 via a contact structure 41 that contacts the rotation center of the spindle 10. The cutting tool 20 has an electrical contact 35 for connecting the measurement circuit 40a that measures the thermoelectric voltage generated between the cutting tool 20 and the workpiece 30, and the conductor 43 is connected to the electrical contact 35. For example, the electrical contact 35 may have a screw fastener for fixing the conductor 43 to the cutting tool 20, and the conductor 43 may be screwed to the cutting tool 20.

[0028] The cutting tool 20 of Embodiment 1 has an insulating layer 25. During cutting, the measuring unit 45 measures the thermoelectric voltage generated in the contact region 28 where the conductive area on the surface of the cutting tool 20 where the insulating layer 25 is not provided comes into contact with the workpiece 30. The insulating layer 25 is formed on a part of the tool surface that comes into contact with the workpiece 30 during processing, and the measuring unit 45 measures the thermoelectric voltage generated in the contact region 28 where the tool surface where the insulating layer 25 is not formed comes into contact with the workpiece 30.

[0029] By forming an insulating layer 25 on a portion of the tool surface, the tool surface with the insulating layer 25 is electrically insulated from the workpiece 30 during machining, and no thermoelectric voltage is generated between the tool surface and the workpiece 30. On the other hand, there is electrical conductivity between the tool surface where the insulating layer 25 is not formed and the workpiece 30, and a thermoelectric voltage is generated there. Therefore, the measuring unit 45 measures the thermoelectric voltage generated in the contact area 28 where the tool surface without the insulating layer 25 is in contact with the workpiece 30.

[0030] The acquisition unit 103 acquires the thermoelectric voltage measured by the measurement unit 45, and the monitoring unit 104 monitors the processing status using the thermoelectric voltage acquired by the acquisition unit 103. The monitoring unit 104 may convert the thermoelectric voltage acquired by the acquisition unit 103 to the contact temperature using a temperature calibration curve or temperature calibration table or the like for calibrating the thermoelectric voltage to the contact temperature.

[0031] To monitor adhesion problems that cause tearing and deterioration of the finished surface 30b, it is preferable to accurately measure the contact temperature between the flank surface 26, which greatly influences the adhesion phenomenon at that location, and the finished surface 30b. To achieve this, it is necessary to generate a thermoelectric voltage between the flank surface 26 and the workpiece 30 (finished surface 30b), while preventing the generation of a thermoelectric voltage between the rake face 24 and the workpiece 30 (chips 30a). Therefore, in the cutting tool 20 shown in Figure 3, an insulating layer 25 is formed on the rake face 24 of the cutting tool 20 to electrically insulate the rake face 24 from the chips 30a, thereby preventing the generation of a thermoelectric voltage between the rake face 24 and the workpiece 30.

[0032] The insulating layer 25 may be formed by coating the rake face 24 with an insulating film. On the other hand, since no insulating layer is formed on the flank face 26, the contact region 28 where the flank face 26 and the workpiece 30 come into contact becomes hot, generating a thermoelectric voltage between the cutting tool 20 and the workpiece 30, and the measuring unit 45 measures the thermoelectric voltage generated in the contact region 28.

[0033] Figure 4 shows the measurement results of the thermoelectric voltage between the flank face and the workpiece. Because an insulating layer 25 is formed on the rake face 24, the measuring unit 45 can measure the thermoelectric voltage between the flank face 26 and the workpiece 30. The monitoring unit 104 can derive the cutting edge temperature (contact temperature) from the thermoelectric voltage between the flank face 26 and the workpiece 30, and monitor the wear and adhesion state of the flank face 26.

[0034] The monitoring unit 104 may periodically monitor the wear and adhesion status of the flank surface 26 using the thermoelectric voltage generated in the contact area 28. For example, the monitoring unit 104 may monitor the wear and adhesion status of the flank surface 26 every 100 cutting operations. If the monitoring unit 104 detects that the temperature of the contact area 28 exceeds a predetermined threshold, it may notify the operator to replace the cutting tool 20. Alternatively, if the monitoring unit 104 detects that the temperature of the contact area 28 is below a predetermined threshold, it may notify the operator that it is preferable to increase the cutting speed to suppress adhesion.

[0035] Figure 5 shows a modified example of the cutting tool 20 used for machining monitoring in Embodiment 1. For the sake of explanation, in Figure 5, the wire 42 in the measurement circuit 40a is connected to an arbitrary position on the workpiece 30, but as shown in Figure 1, it is preferable that the wire 42 is electrically connected to the workpiece 30 via a contact structure 41 that contacts the rotation center of the spindle 10.

[0036] In this modified example, the cutting tool 20 has an insulating layer 25 inside, and the first part 27a and the second part 27b of the cutting tool 20 are electrically insulated by the internal insulating layer 25. For example, two parts having insulating layers on their surfaces may be prepared, and the two parts may be joined by joining the insulating layers together by diffusion bonding or inorganic bonding, etc., thereby forming a cutting tool 20 having an insulating layer 25 inside. Alternatively, the cutting tool 20 may have a high-resistance layer having a high resistance value (for example, 1Ω or more) instead of the internal insulating layer 25. In this modified example, the measurement circuit 40a has the function of measuring the thermoelectric voltage generated in the contact area 28 where the first part 27a of the cutting tool 20 and the workpiece 30 come into contact, and the thermoelectric voltage generated in the contact area 29 where the second part 27b of the cutting tool 20 and the workpiece 30 come into contact.

[0037] The cutting tool 20 has an electrical contact 35a on a first part 27a for connecting a measuring circuit 40a, and an electrical contact 35b on a second part 27b for connecting a measuring circuit 40a. The measuring circuit 40a includes a conductor 42 electrically connected to a contact structure 41 (not shown in Figure 5), a conductor 43a electrically connected to the electrical contact 35a, an electrical resistance 44a provided between the conductors 42 and 43a, and a measuring unit 45a for measuring the thermoelectric voltage between the contact structure 41 and the contact area 28. Furthermore, it includes a conductor 43b electrically connected to the electrical contact 35b, an electrical resistance 44b provided between the conductors 42 and 43b, and a measuring unit 45b for measuring the thermoelectric voltage between the contact structure 41 and the contact area 29. The electrical contacts 35a and 35b have screw fasteners for fixing the conductors 43a and 43b to the cutting tool 20, and the conductors 43a and 43b may be screwed to the cutting tool 20.

[0038] During machining, the measuring unit 45a measures the thermoelectric voltage generated in the contact area 28 where the first part 27a of the cutting tool 20 and the workpiece 30 come into contact, and the measuring unit 45b measures the thermoelectric voltage generated in the contact area 29 where the second part 27b of the cutting tool 20 and the workpiece 30 come into contact. The acquisition unit 103 acquires the thermoelectric voltages measured by the measuring units 45a and 45b, and the monitoring unit 104 uses the thermoelectric voltages acquired by the acquisition unit 103 to monitor the machining status.

[0039] An insulating layer 25 is formed inside the tool, electrically insulating the first portion 27a and the second portion 27b, which allows the monitoring unit 104 to independently monitor the surface temperatures of the first portion 27a and the second portion 27b. In the example shown in Figure 5, the first portion 27a, which has a flank 26, and the second portion 27b, which has a rake face 24, are electrically insulated by the insulating layer 25. Therefore, the measuring unit 45a measures the thermoelectric voltage between the flank 26 and the workpiece 30, and the measuring unit 45b measures the thermoelectric voltage between the rake face 24 and the workpiece 30.

[0040] Figure 6 shows the measurement results of the thermoelectric voltage between the flank face and the workpiece. Because the flank face 26 and the rake face 24 are electrically insulated, the measurement unit 45a can measure the thermoelectric voltage between the flank face 26 and the workpiece 30. The monitoring unit 104 can derive the temperature of the contact area 28 from the thermoelectric voltage between the flank face 26 and the workpiece 30, and monitor the wear and adhesion state of the flank face 26.

[0041] Figure 7 shows the measurement results of the thermoelectric voltage between the rake face and the workpiece. Because the flank face 26 and the rake face 24 are electrically insulated, the measuring unit 45b can measure the thermoelectric voltage between the rake face 24 and the workpiece 30. The monitoring unit 104 can derive the temperature of the contact area 29 from the thermoelectric voltage between the rake face 24 and the workpiece 30, and monitor the state of material removal and chip outflow at the rake face 24. For example, by applying the fact that the temperature at the cutting point rises as the cutting thickness increases, the monitoring unit 104 can detect chatter vibration from fluctuations in the thermoelectric voltage.

[0042] <Embodiment 2> Figure 8 shows a schematic configuration of the machining apparatus 1b of Embodiment 2. The machining apparatus 1b of Embodiment 2 is a lathe that, like Embodiment 1, rotates a workpiece 30 attached to the spindle 10 via a chuck 31, causing the cutting edge of the cutting tool 20 to cut into the rotating workpiece 30. In Embodiment 2, it is assumed that the cutting edge of the cutting tool 20 and the workpiece 30 are made of different materials and are different types of conductors, and the cutting edge of the cutting tool 20 cuts the workpiece 30 at the cutting point 50. In another example of the machining apparatus 1b, the cutting tool 20 may be fixed to the spindle 10, and a feed mechanism may move the workpiece 30 relative to the cutting tool 20. Components in the configuration shown in Figure 8 that have the same reference numerals as those in the configuration shown in Figure 1 have the same or similar functions and perform the same operations as those in the configuration shown in Figure 1, so their description is omitted.

[0043] The machining apparatus 1b of Embodiment 2 has a measurement circuit 40b that measures the difference in thermoelectric power generated in multiple areas where the cutting tool 20 and the workpiece 30 come into contact during machining, using the tool-workpiece thermocouple method. Unlike Embodiment 1, the measurement circuit 40b does not have a contact structure 41 that is electrically connected to the spindle 10, thus simplifying the circuit configuration.

[0044] The cutting point 50 is a contact area where the cutting tool 20 and the workpiece 30, which are dissimilar conductors, come into contact. During cutting, the temperature of the cutting point 50 becomes high, generating a thermoelectric voltage between the cutting tool 20 and the workpiece 30. In Embodiment 2, the cutting point 50 is divided into two contact areas by an insulating layer provided inside the cutting tool 20, and the measurement circuit 40b measures the difference in thermoelectric voltage generated in each contact area.

[0045] Figure 9 shows an example of a cutting tool 20 used for machining monitoring in Embodiment 2. The cutting tool 20 has an insulating layer 25 inside, and the first part 27a and the second part 27b of the cutting tool 20 are electrically insulated by the insulating layer 25 inside. For example, two parts having insulating layers on their surfaces may be prepared and the two parts joined together by joining the insulating layers, thereby forming a cutting tool 20 having an insulating layer 25 inside. Alternatively, the cutting tool 20 may have a high-resistance layer with a high resistance value (for example, 1Ω or more) instead of the insulating layer 25 inside. The measurement circuit 40b has the function of measuring the difference between the thermoelectric voltage generated in the contact area 28 where the first part 27a of the cutting tool 20 and the workpiece 30 are in contact, and the thermoelectric voltage generated in the contact area 29 where the second part 27b of the cutting tool 20 and the workpiece 30 are in contact.

[0046] The cutting tool 20 has an electrical contact 35a on its first part 27a for connecting a measuring circuit 40b, and an electrical contact 35b on its second part 27b for connecting a measuring circuit 40b. The measuring circuit 40b includes a conductor 46 electrically connected to the electrical contact 35a, a conductor 47 electrically connected to the electrical contact 35b, an electrical resistor 44 provided between the conductors 46 and 47, and a measuring unit 45 for measuring the difference between the thermoelectric voltage generated between the first part 27a and the workpiece 30 and the thermoelectric voltage generated between the second part 27b and the workpiece 30. The electrical contacts 35a and 35b have screw fasteners for fixing the conductors 46 and 47 to the cutting tool 20, and the conductors 46 and 47 may be screwed to the cutting tool 20.

[0047] During the cutting process, the measuring unit 45 measures the difference between the thermoelectric voltage generated in the contact area 28 where the first part 27a of the cutting tool 20 and the workpiece 30 come into contact, and the thermoelectric voltage generated in the contact area 29 where the second part 27b of the cutting tool 20 and the workpiece 30 come into contact. The acquisition unit 103 acquires the difference in thermoelectric voltage measured by the measuring unit 45, and the monitoring unit 104 uses the difference in thermoelectric voltage acquired by the acquisition unit 103 to monitor the state of the cutting process.

[0048] In the cutting tool 20 shown in Figure 9, the first portion 27a having a flank face 26 and the second portion 27b having a rake face 24 are electrically insulated by an insulating layer 25. Therefore, the measuring unit 45 measures the difference between the thermoelectric voltage generated between the flank face 26 and the finishing surface 30b and the thermoelectric voltage generated between the rake face 24 and the chip 30a, and the monitoring unit 104 monitors the machining state using the difference in thermoelectric voltage. Generally, on the rake face 24 side, even as tool wear progresses, the contact length (i.e., friction distance) does not change significantly and the contact temperature does not change significantly, whereas on the flank face 26 side, the contact temperature changes as the friction distance increases with the progression of tool wear. Generally, the temperature on the flank face 26 side is higher closer to the cutting edge and lower further away from the cutting edge. Therefore, an increase in friction distance causes the measurement of the average temperature up to the point farther from the cutting edge and where the temperature is lower, which is a factor in lowering the measured temperature. On the other hand, an increase in friction distance increases frictional heat generation on the flank face 26 side. These two factors have opposite tendencies and therefore cancel each other out, but generally the latter has a greater effect. As a result, the contact temperature measured on the flank surface 26 increases as tool wear increases, and the monitoring unit 104 can monitor tool wear on the flank surface 26 side from the difference in thermoelectric power.

[0049] On the other hand, if chatter vibration or eccentricity of the workpiece 30 during turning causes fluctuations in the cut thickness, the contact temperature on the rake face 24 side increases or decreases in correlation with the cut thickness. In the case of chatter vibration, on the flank face 26 side, the contact length increases or decreases in correlation with the vibration velocity in the direction of the cut thickness, and the contact temperature also increases or decreases accordingly, so fluctuations with different phases are measured. Specifically, the contact length increases when the vibration velocity increases the cut thickness, and decreases when the vibration velocity decreases the cut thickness. The monitoring unit 104 can monitor fluctuations in the cut thickness due to chatter vibration or eccentricity of the workpiece 30 during turning based on the difference in thermoelectric power.

[0050] Figure 10 shows the measurement results of the difference in thermoelectric power. Because the flank face 26 and the rake face 24 are electrically insulated, the measuring unit 45 can measure the difference in thermoelectric power between the flank face 26 and the workpiece 30 (finished surface 30b) and between the rake face 24 and the workpiece 30 (chips 30a). The monitoring unit 104 can monitor the wear and adhesion state of the flank face 26 and / or the rake face 24, as well as fluctuations in the cutting thickness, from the difference in thermoelectric power.

[0051] Figure 11 shows another example of a cutting tool 20 used for machining monitoring in Embodiment 2. The cutting tool 20 is an R-type cutting tool with an arc-shaped cutting edge and has an insulating layer 25 inside. The internal insulating layer 25 electrically insulates the first part 27a and the second part 27b of the cutting tool 20. Alternatively, the cutting tool 20 may have a high-resistance layer with a high resistance value (e.g., 1Ω or more) instead of the internal insulating layer 25. The measurement circuit 40b has the function of measuring the difference between the thermoelectric voltage generated in the contact area 28 where the first part 27a of the cutting tool 20 and the workpiece 30 are in contact, and the thermoelectric voltage generated in the contact area 29 where the second part 27b of the cutting tool 20 and the workpiece 30 are in contact.

[0052] The cutting tool 20 has an electrical contact 35a on its first part 27a for connecting a measuring circuit 40b, and an electrical contact 35b on its second part 27b for connecting a measuring circuit 40b. The measuring circuit 40b includes a conductor 46 electrically connected to the electrical contact 35a, a conductor 47 electrically connected to the electrical contact 35b, an electrical resistor 44 provided between the conductors 46 and 47, and a measuring unit 45 for measuring the difference between the thermoelectric voltage generated between the first part 27a and the workpiece 30 and the thermoelectric voltage generated between the second part 27b and the workpiece 30. The electrical contacts 35a and 35b have screw fasteners for fixing the conductors 46 and 47 to the cutting tool 20, and the conductors 46 and 47 may be screwed to the cutting tool 20.

[0053] During machining, the measuring unit 45 measures the difference between the thermoelectric voltage generated in the contact area 28 where the first part 27a of the cutting tool 20 contacts the workpiece 30, and the thermoelectric voltage generated in the contact area 29 where the second part 27b of the cutting tool 20 contacts the workpiece 30. In Figure 11, the contact-to-detachment line 30c indicates the boundary line where the chip 30a contacts / detaches from the rake face 24. The acquisition unit 103 acquires the difference in thermoelectric voltage measured by the measuring unit 45, and the monitoring unit 104 monitors the machining state using the difference in thermoelectric voltage acquired by the acquisition unit 103.

[0054] In the cutting tool 20 shown in Figure 11, when viewed from the rake face 24 side, the insulating layer 25 divides the cutting edge into a cutting edge portion that mainly generates a finished surface (front cutting edge) and a cutting edge portion that mainly removes material (side cutting edge). For this reason, the insulating layer 25 electrically insulates the first portion 27a having the front cutting edge from the second portion 27b having the side cutting edge. Therefore, the measuring unit 45 measures the difference between the thermoelectric voltage in the contact area 28 (finished surface generation area) where the cutting thickness is small and the thermoelectric voltage in the contact area 29 (main material removal area) where the cutting thickness is large, and the monitoring unit 104 monitors the state of processing using the difference in thermoelectric voltage.

[0055] <Embodiment 3> Embodiments 1 and 2 describe a method for monitoring the machining state using a tool-workpiece thermocouple method. Specifically, measurement circuits 40a and 40b measure the thermoelectric voltage, and the monitoring unit 104 monitors the machining state using the measured thermoelectric voltage. In contrast, Embodiment 3 describes a method for monitoring the machining state by measuring the contact resistance at the cutting point 50 and using the measured contact resistance. In Embodiment 3, the cutting tool 20 comprises an insulating layer or high-resistance layer provided on at least a portion of the surface of the cutting tool 20 and / or inside, and electrical contacts for connecting a circuit for measuring the contact resistance in the contact area between the cutting tool and the workpiece.

[0056] Figure 12 shows an example of a cutting tool 20 used for machining monitoring in Embodiment 3. The cutting tool 20 shown in Figure 12 is used for cutting in the machining apparatus 1a shown in Figure 1, and in Embodiment 3, instead of the measurement circuit 40a shown in Figure 1, a measurement circuit 60a for measuring contact resistance at the cutting point 50 is used.

[0057] The measurement circuit 60a includes a current circuit 70 that supplies current and a voltage measurement circuit 61 that measures voltage. The current circuit 70 includes a conductor 72 that is electrically connected to the workpiece 30, a power supply 71 for supplying current between the cutting tool 20 and the workpiece 30, a conductor 73 that is electrically connected to the electrical contact 35b of the cutting tool 20, and a current measurement unit 75 that measures the current I flowing through the current circuit 70. The electrical resistance 74 is an internal resistance parasitic to the current measurement unit 75. The current measurement unit 75 and the electrical resistance 74 may be ammeters. The voltage measurement circuit 61 includes a conductor 62 that is electrically connected to the workpiece 30, a conductor 63 that is electrically connected to the electrical contact 35a of the cutting tool 20, and a voltage measurement unit 65 that measures the voltage V applied to the electrical resistance 64. The electrical resistance 64 with resistance value Rv is an internal resistance parasitic to the voltage measurement unit 65. The voltage measurement unit 65 and the electrical resistance 64 may be voltmeters.

[0058] In Figure 12, for the sake of explanation, the wires 62 and 72 in the measurement circuit 60a are connected to arbitrary positions on the workpiece 30. However, it is preferable that the wires 62 and 72 are electrically connected to the workpiece 30 via a contact structure 41 (see Figure 1) that contacts the rotation center of the spindle 10.

[0059] The cutting tool 20 shown in Figure 12 has an insulating layer 25 on a portion of the tool surface that contacts the workpiece 30. By forming the insulating layer 25 on a portion of the tool surface, the tool surface on which the insulating layer 25 is formed is electrically insulated from the workpiece 30 during machining, while the tool surface on which the insulating layer 25 is not formed and the workpiece 30 are electrically conductive. In Embodiment 3, the current circuit 70 is connected to the cutting tool 20 and the workpiece 30, so that current flows in the contact region 28 where the conductive region on the tool surface where the insulating layer 25 is not provided comes into contact with the workpiece 30.

[0060] Alternatively, a high-resistance layer with a high resistance value may be formed on the tool surface instead of the insulating layer 25. For example, if Rs is the resistance value of the contact resistance in the contact region 28 where the conductive region of the tool surface and the workpiece 30 come into contact, it is preferable that the resistance value of the high-resistance layer be 30 times or more Rs. Typically, the resistance value Rs of the contact resistance in the contact region 28 is assumed to be several mΩ to several tens of mΩ, so a resistance value of 1 Ω or more of the high-resistance layer is sufficient. Even if a high-resistance layer is provided on the tool surface instead of the insulating layer 25, it is possible to obtain the same effect as with the insulating layer 25.

[0061] Let I be the current flowing through the current circuit 70, i1 be the current flowing through the contact area 28, and i2 be the current flowing through the voltage measurement circuit 61. I = i1 + i2 If Rs is the contact resistance value in the contact region 28, Ri is the internal resistance value of the measurement system, Rv is the electrical resistance value of 64, V is the voltage measured by the voltage measurement unit 65, and E is the thermoelectric power generated in the contact region 28, then V=i2×Rv=i1×(Rs+Ri)+E (Formula 1) therefore, Rs = (VE) / i1 - Ri =(VE) / (I-i2)-Ri =(VE)×Rv / (I×Rv-V)-Ri···(Equation 2) This is derived. Since the contact resistance Rs is minute, it is preferable that the measurement circuit 60a has a configuration that realizes the four-terminal method.

[0062] In the example shown in Figure 12, the insulating layer 25 is formed by coating the rake face 24 with an insulating film, and no insulating layer is formed on the flank face 26. Therefore, as the wear of the flank face 26 increases, the contact area 28 increases, and the contact resistance Rs decreases.

[0063] During cutting, the current measuring unit 75 measures the current I flowing through the conductor 73, and the voltage measuring unit 65 measures the voltage V across the electrical resistance 64. The acquisition unit 103 acquires the current I measured by the current measuring unit 75 and the voltage V measured by the voltage measuring unit 65. The monitoring unit 104 derives the contact resistance Rs in the contact region 28 from the current I and voltage V acquired by the acquisition unit 103 based on (Equation 2), and monitors the machining state using the derived contact resistance Rs. As described above, the contact resistance Rs changes as wear progresses on the flank surface 26, so the monitoring unit 104 may monitor the progress of wear on the flank surface 26 from the change in contact resistance Rs.

[0064] Regarding the internal resistance Ri, it can be ignored if it is sufficiently smaller than the contact resistance Rs; otherwise, it should be measured beforehand. Also, since the internal resistance Ri does not change, the monitoring unit 104 may be configured to monitor changes in (Rs + Ri). Regarding the thermoelectric power E, it can be ignored if its absolute value is sufficiently smaller than the voltage drop due to the contact resistance Rs; otherwise, it should be measured separately. By disconnecting the current circuit 70 to the state shown in Figure 3, the thermoelectric power E can be measured by the voltage measurement circuit 61.

[0065] Alternatively, since electrical resistances 74 and 64 are generally sufficiently large compared to contact resistance Rs and internal resistance Ri, I can be considered to be approximately equal to i1. Here, the measured voltage V in (Equation 1) represents the change in contact resistance Rs and thermoelectric power E. Generally, contact resistance Rs is more susceptible to tool wear, so an increase in tool wear can be determined from the decrease in the measured voltage V. Furthermore, the current circuit 70 can be connected in a direction such that the thermoelectric power E decreases the measured voltage V as tool wear progresses, thereby improving the detection sensitivity of the measured voltage V due to tool wear.

[0066] Figure 13 shows another example of a cutting tool 20 used for machining monitoring in Embodiment 3. The cutting tool 20 shown in Figure 13 is used for cutting in the machining apparatus 1b shown in Figure 8, and in Embodiment 3, instead of the measuring circuit 40b shown in Figure 8, a measuring circuit 60b is used to measure the contact resistance at the cutting point 50. The measuring circuit 60b comprises a current circuit 70 that supplies current and a voltage measuring circuit 61 that measures voltage.

[0067] The cutting tool 20 has an insulating layer 25 inside, which electrically insulates the first part 27a and the second part 27b of the cutting tool 20. The insulating layer 25 may be a high-resistance layer. The cutting tool 20 also has a coating layer over its entire surface. Here, "entire surface" means all surfaces that may come into contact with the workpiece 30 during cutting, and therefore, surfaces that do not come into contact with the workpiece 30 do not need to have a coating layer. The cutting tool 20 shown in Figure 13 has a coating layer 80a on the rake face 24 and a coating layer 80b on the flank face 26. The coating layers 80a and 80b may be high-resistance layers or insulating layers, and if they are high-resistance layers, it is preferable that they have a resistance value of 1Ω or more. As described above, if the internal layer 25 is a high-resistance layer, it is preferable that this high-resistance layer 25 has a resistance value of 1Ω or more.

[0068] The cutting tool 20 has an electrical contact 35a for connecting a voltage measuring circuit 61 and an electrical contact 35c for connecting a current circuit 70 in its first part 27a, and an electrical contact 35b for connecting a voltage measuring circuit 61 and an electrical contact 35d for connecting a current circuit 70 in its second part 27b.

[0069] The current circuit 70 includes a conductor 76 electrically connected to electrical contact 35c, a power supply 71 for supplying current between the cutting tool 20 and the workpiece 30, a conductor 77 electrically connected to electrical contact 35d, and a current measuring unit 75 for measuring the current I flowing through the current circuit 70. The electrical resistance 74 is an internal resistance parasitic to the current measuring unit 75. The current measuring unit 75 and the electrical resistance 74 may be ammeters. The voltage measuring circuit 61 includes a conductor 66 electrically connected to electrical contact 35a, a conductor 67 electrically connected to electrical contact 35b, and a voltage measuring unit 65 for measuring the voltage V applied to the electrical resistance 64. The electrical resistance 64 with resistance value Rv is an internal resistance parasitic to the voltage measuring unit 65. The voltage measuring unit 65 and the electrical resistance 64 may be voltmeters.

[0070] Let r1 be the contact resistance of the contact region 28 where the first part 27a of the cutting tool 20 contacts the workpiece 30 (finished surface 30b), and let r2 be the contact resistance of the contact region 29 where the second part 27b of the cutting tool 20 contacts the workpiece 30 (chips 30a). Let I be the current flowing through the current circuit 70, i1 be the current flowing from the contact region 29 through the workpiece 30 to the contact region 28, and i2 be the current flowing through the voltage measurement circuit 61. I = i1 + i2 Since the tool base material is assumed to have good conductivity, its internal resistance can be ignored, and the internal layer 25 is assumed to be an insulating layer. If the electrical resistance 64 is Rv, the voltage measured by the voltage measuring unit 65 is V, and the thermoelectric forces generated in the contact area 28 and contact area 29 are E1 and E2, respectively, V = i² × Rv = i₁ × (r₁ + r₂) + (E₁ - E₂) Here, the two thermoelectric forces roughly cancel each other out, and the difference is considered to be sufficiently smaller than the voltage drop due to contact resistance, (r1+r2)≒V×Rv / (I×Rv-V) (Formula 3) This is derived.

[0071] Furthermore, if the inner layer 25 is a high-resistance layer, and its resistance is Rl, then in the circuit, the electrical resistance Rv that exists when the inner layer 25 is an insulating layer is simply replaced by the electrical resistance Rv and the high-resistance layer Rl connected in parallel. Therefore, in (Equation 3), Rv should be replaced with Rv × Rl / (Rv + Rl).

[0072] During machining, the current measuring unit 75 measures the current I flowing through the conductor 77, and the voltage measuring unit 65 measures the voltage V across the electrical resistance 64. The acquisition unit 103 acquires the current I measured by the current measuring unit 75 and the voltage V measured by the voltage measuring unit 65, and the monitoring unit 104 derives the sum (r1+r2) of the contact resistance r1 of the contact region 28 and the contact resistance r2 of the contact region 29 from the current I and voltage V acquired by the acquisition unit 103, based on (Equation 3). The monitoring unit 104 uses the derived contact resistance (r1+r2) to monitor the machining state. Here, if the coating layer 80a and / or the coating layer 80b are insulating layers, the contact resistance (r1+r2) becomes infinite.

[0073] During cutting, if the coating layer 80a and / or coating layer 80b wears down or peels off, the contact resistance (r1+r2) decreases. For example, if the coating layer 80a and coating layer 80b at the cutting edge completely peel off and the conductive base material in the first part 27a and the second part 27b comes into contact with the workpiece 30, the contact resistance (r1+r2) decreases significantly. The monitoring unit 104 may monitor the wear / peeling state of the coating layer 80a and / or coating layer 80b by monitoring the change in contact resistance (r1+r2).

[0074] Figure 14 shows another example of a cutting tool 20 used for machining monitoring in Embodiment 3. The cutting tool 20 is an R-type cutting tool with an arc-shaped cutting edge. The cutting tool 20 shown in Figure 14 is used for machining in the machining apparatus 1b shown in Figure 8, and in Embodiment 3, instead of the measurement circuit 40b shown in Figure 8, a measurement circuit 60b is used to measure the contact resistance at the cutting point 50. The measurement circuit 60b comprises a current circuit 70 that supplies current and a voltage measurement circuit 61 that measures voltage.

[0075] The cutting tool 20 has an insulating layer 25 inside, which electrically insulates the first part 27a and the second part 27b of the cutting tool 20. The insulating layer 25 may also be a high-resistance layer. The cutting tool 20 has an electrical contact 35a for connecting a voltage measuring circuit 61 and an electrical contact 35c for connecting a current circuit 70 in the first part 27a, and an electrical contact 35b for connecting a voltage measuring circuit 61 and an electrical contact 35d for connecting a current circuit 70 in the second part 27b. If the internal layer 25 is a high-resistance layer, it is preferable that this high-resistance layer 25 has a resistance value of 1Ω or more.

[0076] The current circuit 70 includes a conductor 76 electrically connected to electrical contact 35c, a power supply 71 for supplying current between the cutting tool 20 and the workpiece 30, a conductor 77 electrically connected to electrical contact 35d, and a current measuring unit 75 for measuring the current I flowing through the current circuit 70. It also includes a switch 78 for turning the current circuit 70 on (conducting) or off (non-conducting). The electrical resistance 74 is an internal resistance parasitic to the current measuring unit 75. In the state shown in Figure 14, the switch 78 is closed and the current circuit 70 is on. The current measuring unit 75 and the electrical resistance 74 may be ammeters. The voltage measuring circuit 61 includes a conductor 66 electrically connected to electrical contact 35a, a conductor 67 electrically connected to electrical contact 35b, and a voltage measuring unit 65 for measuring the voltage V applied to the electrical resistance 64. The electrical resistance 64 with resistance value Rv is an internal resistance parasitic to the voltage measuring unit 65. The voltage measuring unit 65 and the electrical resistance unit 64 may be voltmeters.

[0077] In the cutting tool 20 shown in Figure 14, when viewed from the rake face 24 side, the internal layer 25, which is an insulating layer or a high-resistance layer, divides the cutting edge into a cutting edge portion that mainly generates a finished surface (front cutting edge) and a cutting edge portion that mainly removes material (side cutting edge). For this reason, the internal layer 25 makes it difficult for the first portion 27a having the front cutting edge and the second portion 27b having the side cutting edge to conduct electricity or provides insulation. In Figure 14, the contact / disconnection line 30c indicates the boundary line where the chip 30a contacts / disconnects from the tool rake face.

[0078] Let r1 be the contact resistance of the contact region 28 where the first part 27a of the cutting tool 20 and the workpiece 30 come into contact, and let r2 be the contact resistance of the contact region 29 where the second part 27b of the cutting tool 20 and the workpiece 30 come into contact. If I is the current flowing through the current circuit 70, the contact resistance (r1 + r2) is derived by the following equation (3). (r1+r2)≒V×Rv / (I×Rv-V) (Formula 3)

[0079] During the cutting process, the current measuring unit 75 measures the current I flowing through the conductor 77, and the voltage measuring unit 65 measures the voltage V across the electrical resistance 64. The acquisition unit 103 acquires the current I measured by the current measuring unit 75 and the voltage V measured by the voltage measuring unit 65. The monitoring unit 104 derives the sum (r1+r2) of the contact resistance r1 of the contact region 28 and the contact resistance r2 of the contact region 29 from the current I and voltage V acquired by the acquisition unit 103, based on (Equation 3). The monitoring unit 104 monitors the state of the machining process using the contact resistance (r1+r2).

[0080] In the cutting tool 20 shown in Figure 14, a high-resistance or insulating coating layer may be formed on the rake face, or a high-resistance or insulating coating layer may be formed on both the rake face and the flank face. This allows the monitoring unit 104 to monitor the wear / peeling state of the coating layer on the flank face or the cutting edge based on contact resistance.

[0081] The current circuit 70 is turned on and off by opening and closing the switch 78. When the switch 78 is opened and the current circuit 70 is turned off, the contact resistance (r1+r2) measurement function is stopped, and as shown in Figure 11, the voltage measurement circuit 61 begins to measure the thermoelectric power (E1-E2). This thermoelectric power value may be used for monitoring the processing state in Embodiment 2, or it may be used to correct the approximate value of (Equation 3) to derive a more accurate contact resistance value. In the latter case, (V-(E1-E2)) can be used instead of the voltage V in (Equation 3), and the contact resistance can be measured more accurately.

[0082] Figure 15 shows another example of a cutting tool 20 used for machining monitoring in Embodiment 3. The cutting tool 20 shown in Figure 15 is a rotary tool that is mounted on the spindle of a machining device such as a machining center or milling machine. The cutting tool 20 comprises a holder 85, a plurality of inserts 83a, 83b, and an insulating layer 25 that insulates between inserts 83a and 83b. The insulating layer 25 may be a high-resistance layer. The holder 85 is a component that fixes the inserts 83a, 83b, and the inserts 83a, 83b are fixed to the holder 85. The cutting tool 20 shown in Figure 15 is a boring multi-edge tool and has two inserts 83a, 83b at positions of different diameters. Insert 83a has electrical contacts 35a, 35c, and insert 83b has electrical contacts 35b, 35d.

[0083] The measurement circuit 60b includes a current circuit 70 that supplies current and a voltage measurement circuit 61 that measures voltage. The current circuit 70 includes a conductor 76 that is electrically connected to the electrical contact 35c of the insert 83a, a power supply 71 for supplying current between the insert and the workpiece 30, a conductor 77 that is electrically connected to the electrical contact 35d of the insert 83b, and a current measurement unit 75 that measures the current I flowing through the current circuit 70. The electrical resistance 74 is an internal resistance parasitic to the current measurement unit 75. The current measurement unit 75 and the electrical resistance 74 may be ammeters. The voltage measurement circuit 61 includes a conductor 66 that is electrically connected to the electrical contact 35a of the insert 83a, a conductor 67 that is electrically connected to the electrical contact 35b of the insert 83b, and a voltage measurement unit 65 that measures the voltage V applied to the electrical resistance 64. The electrical resistance 64 with resistance value Rv is an internal resistance parasitic to the voltage measurement unit 65. The voltage measuring unit 65 and the electrical resistance unit 64 may be voltmeters.

[0084] Let r1 be the contact resistance of the contact area 81 where insert 83a and workpiece 30 come into contact, and r2 be the contact resistance of the contact area 82 where insert 83b and workpiece 30 come into contact. If I is the current flowing through the current circuit 70, the contact resistance (r1 + r2) is derived by the following equation (3). (r1+r2)≒V×Rv / (I×Rv-V) (Formula 3)

[0085] During the cutting process, the current measuring unit 75 measures the current I flowing through the conductor 77, and the voltage measuring unit 65 measures the voltage V across the electrical resistance 64. The acquisition unit 103 acquires the current I measured by the current measuring unit 75 and the voltage V measured by the voltage measuring unit 65. The monitoring unit 104 derives the sum (r1+r2) of the contact resistance r1 of the contact region 28 and the contact resistance r2 of the contact region 29 from the current I and voltage V acquired by the acquisition unit 103, based on (Equation 3). The monitoring unit 104 monitors the state of the machining process using the contact resistance (r1+r2).

[0086] In the inserts 83a and 83b shown in Figure 15, a high-resistance or insulating coating layer may be formed on the rake face, or a high-resistance or insulating coating layer may be formed on both the rake face and the flank face. This allows the monitoring unit 104 to monitor the wear / peeling state of the coating layer on the flank face or cutting edge based on contact resistance.

[0087] Figure 16 shows another example of a cutting tool 20 used for machining monitoring in Embodiment 3. The cutting tool 20 shown in Figure 16 is a rotary tool attached to the spindle of a machining device such as a machining center or milling machine. The cutting tool 20 comprises a holder 85, an insert 83, a conductive guide pad 84, and an insulating layer 25 that insulates the space between the insert 83 and the guide pad 84. The insulating layer 25 may be a high-resistance layer. The holder 85 is a component that fixes the insert 83 and the guide pad 84, and the insert 83 and the guide pad 84 are fixed to the holder 85. The guide pad 84 is provided to improve the diameter accuracy and straightness during deep hole machining, and rubs against the machined surface machined by the insert 83. In this example, the insert 83 and the guide pad 84 simultaneously contact the workpiece 30 during machining. The insulating layer 25 is provided between the guide pad 84 and the holder 85 to insulate the insert 83 from the guide pad 84, but it may also be provided between the insert 83 and the holder 85. The insert 83 has electrical contacts 35a and 35c, and the guide pad 84 has electrical contacts 35b and 35d.

[0088] The measurement circuit 60b includes a current circuit 70 that supplies current and a voltage measurement circuit 61 that measures voltage. The current circuit 70 includes a conductor 76 that is electrically connected to the electrical contact 35c of the insert 83, a power supply 71 for supplying current, a conductor 77 that is electrically connected to the electrical contact 35d of the guide pad 84, and a current measurement unit 75 that measures the current I flowing through the current circuit 70. The electrical resistance 74 is an internal resistance parasitic to the current measurement unit 75. The current measurement unit 75 and the electrical resistance 74 may be ammeters. The voltage measurement circuit 61 includes a conductor 66 that is electrically connected to the electrical contact 35a of the insert 83, a conductor 67 that is electrically connected to the electrical contact 35b of the guide pad 84, and a voltage measurement unit 65 that measures the voltage V applied to the electrical resistance 64. The electrical resistance 64 with resistance value Rv is an internal resistance parasitic to the voltage measurement unit 65. The voltage measurement unit 65 and the electrical resistance 64 may be voltmeters.

[0089] Let r1 be the contact resistance of the contact area 81 where the insert 83 and the workpiece 30 come into contact, and let r2 be the contact resistance of the contact area 82 where the guide pad 84 and the workpiece 30 come into contact. If I is the current flowing through the current circuit 70, the contact resistance (r1 + r2) is derived by the following equation (3). (r1+r2)≒V×Rv / (I×Rv-V) (Formula 3)

[0090] During the cutting process, the current measuring unit 75 measures the current I flowing through the conductor 77, and the voltage measuring unit 65 measures the voltage V across the electrical resistance 64. The acquisition unit 103 acquires the current I measured by the current measuring unit 75 and the voltage V measured by the voltage measuring unit 65. The monitoring unit 104 derives the sum (r1+r2) of the contact resistance r1 of the contact region 28 and the contact resistance r2 of the contact region 29 from the current I and voltage V acquired by the acquisition unit 103, based on (Equation 3). The monitoring unit 104 monitors the state of the machining process using the contact resistance (r1+r2).

[0091] In the insert 83 shown in Figure 16, a high-resistance or insulating coating layer may be formed on the rake face, or a high-resistance or insulating coating layer may be formed on both the rake face and the flank face. This allows the monitoring unit 104 to monitor the wear / peeling state of the coating layer on the flank face or cutting edge based on contact resistance.

[0092] The present disclosure has been described above based on embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure.

[0093] In the cutting tool 20 shown in Figure 3, the insulating layer 25 is formed on the rake face 24 but not on the flank face 26. However, in a modified example, the insulating layer 25 may be formed on the flank face 26 but not on the rake face 24. Furthermore, in the cutting tool 20 shown in Figures 3, 5, 9, 11, 12, and 14, and the insert 83 and guide pad 84 shown in Figures 15 and 16, a low-resistance or highly conductive coating layer may be formed on surfaces where a high-resistance or insulating coating layer is not formed. In this case, the machining state can be monitored in the same way as when the tool base material surface with good conductivity is not coated.

[0094] The details of the nature of this disclosure are as follows: A machining apparatus according to one aspect of the present disclosure includes a rotation mechanism for rotating a spindle to which a cutting tool or workpiece is attached, the cutting tool having an insulating layer on a portion of its surface or having an insulating layer or high-resistance layer inside the cutting tool; a movement control unit for controlling the relative movement of the cutting tool with respect to the workpiece; and a monitoring unit for monitoring the machining state using the thermoelectric voltage generated in the contact area where a conductive area on the surface of the cutting tool without an insulating layer comes into contact with the workpiece during machining.

[0095] According to this embodiment of the processing apparatus, it is possible to monitor the processing state with high precision or in a simple manner using the thermoelectric voltage generated in the contact area between the conductive region where an insulating layer is not provided and the workpiece.

[0096] The monitoring unit may monitor the machining state using the thermoelectric voltage generated in the contact area where the surface of the cutting tool, which does not have an insulating layer, comes into contact with the workpiece. Alternatively, the cutting tool may have an insulating layer formed on its rake face, and the monitoring unit may monitor the machining state using the thermoelectric voltage generated in the contact area where the flank face, which does not have an insulating layer, comes into contact with the workpiece.

[0097] The cutting tool has an insulating layer or a high-resistance layer inside, and the first part and the second part of the cutting tool are electrically insulated or made to be less conductive by the insulating layer or high-resistance layer inside, and the monitoring unit may monitor the machining state using the thermoelectric voltage generated in the first region where the first part of the cutting tool and the workpiece are in contact, and the thermoelectric voltage generated in the second region where the second part of the cutting tool and the workpiece are in contact. In the cutting tool, the first part having a flank and the second part having a rake face may be electrically insulated or made to be less conductive by the insulating layer or high-resistance layer.

[0098] The monitoring unit may monitor the processing status using the difference between the thermoelectric voltage generated in the first region and the thermoelectric voltage generated in the second region.

[0099] A machining apparatus in another aspect of the present disclosure includes a rotating mechanism for rotating a spindle to which a cutting tool having an insulating layer or a high-resistance layer on at least a portion of the surface of the cutting tool and / or inside the cutting tool, or a workpiece to be cut, is attached; a moving control unit for controlling the relative movement of the cutting tool with respect to the workpiece; and a monitoring unit for monitoring the machining state using the contact resistance in the contact area where the surface of the cutting tool and the workpiece come into contact during machining.

[0100] According to this embodiment of the machining apparatus, the machining state can be easily monitored using the contact resistance in the contact area where the surface of the cutting tool and the workpiece come into contact.

[0101] The cutting tool has an insulating layer or a high-resistance layer formed on its rake face, and the monitoring unit may monitor the machining state using the contact resistance in the contact area where the flank face, which does not have an insulating layer or high-resistance layer, comes into contact with the workpiece.

[0102] The cutting tool has an insulating layer or a high-resistance layer inside, and the insulating layer electrically insulates or makes it difficult for the first and second parts of the cutting tool to conduct electricity. The monitoring unit may monitor the machining state using the sum of the contact resistance in the first region where the first part of the cutting tool contacts the workpiece and the contact resistance in the second region where the second part of the cutting tool contacts the workpiece. The insulating layer or high-resistance layer may be provided on the surfaces of the first and second parts. The monitoring unit may monitor the machining state using the thermoelectric voltage generated in the contact region instead of, or in addition to, the contact resistance.

[0103] A cutting tool in another aspect of the present disclosure comprises an insulating layer or high-resistance layer provided on at least a portion of the surface of the cutting tool and / or inside it, and an electrical contact for connecting a circuit for measuring the thermoelectric power generated in the contact area between the cutting tool and the workpiece or the contact resistance in the contact area.

[0104] Using a cutting tool of this type makes it possible to monitor the machining state with higher accuracy or in a simpler manner.

[0105] An insulating layer or high-resistance layer may be formed on the rake face of the cutting tool. The insulating layer or high-resistance layer may be provided inside the cutting tool to electrically insulate or make it difficult for the first and second parts of the cutting tool to conduct electricity. In this case, the insulating layer or high-resistance layer may electrically insulate or make it difficult for the first part having a relief face to conduct electricity to the second part having a rake face. The insulating layer or high-resistance layer may also electrically insulate or make it difficult for the cutting edge portion that generates the finished surface to conduct electricity to the cutting edge portion that removes material. [Explanation of symbols]

[0106] 1a, 1b... Machining device, 10... Spindle, 11... Rotation mechanism, 20... Cutting tool, 21... Feed mechanism, 24... Rake face, 25... Insulation layer, 26... Relief face, 27a... First part, 27b... Second part, 28, 29... Contact area, 30... Workpiece, 30a... Chips, 30b... Finished surface, 30c... Contact disconnection line, 35, 35a, 35b, 35c, 35d... Electrical contacts, 40a, 40b... Measurement circuit, 41... Contact structure, 45, 45a, 45b... Measurement Section 50...Cutting point, 60a, 60b...Measurement circuit, 61...Voltage measurement circuit, 64...Electrical resistance, 65...Voltage measurement section, 70...Current circuit, 71...Power supply, 75...Current measurement section, 78...Switch, 80a, 80b...Coating layer, 81, 82...Contact area, 83, 83a, 83b...Insert, 84...Guide pad, 85...Holder, 100...Control unit, 101...Rotation control unit, 102...Movement control unit, 103...Acquisition unit, 104...Monitoring unit.

Claims

1. A cutting tool having an insulating layer on a portion of its surface, or having an insulating layer or high-resistance layer inside the cutting tool, or a rotating mechanism for rotating a spindle to which a workpiece is attached, A movement control unit that controls the relative movement of the cutting tool with respect to the workpiece, During machining, a monitoring unit monitors the machining state using the thermoelectric voltage generated in the contact area where a conductive area without an insulating layer on the surface of the cutting tool comes into contact with the workpiece. A processing device equipped with the following features.

2. The monitoring unit monitors the machining state using the thermoelectric voltage generated in the contact area where the surface of the cutting tool, which does not have an insulating layer, comes into contact with the workpiece. The processing apparatus according to feature 1.

3. The cutting tool has an insulating layer formed on the rake face. The monitoring unit monitors the machining state using the thermoelectric voltage generated in the contact area where the flank surface, which does not have an insulating layer, comes into contact with the workpiece. The processing apparatus according to feature 2.

4. The cutting tool has an insulating layer or a high-resistance layer inside, and the first part and the second part of the cutting tool are electrically insulated or made less conductive by the internal insulating layer or high-resistance layer. The monitoring unit monitors the machining state using the thermoelectric power generated in the first region where the first part of the cutting tool and the workpiece are in contact, and the thermoelectric power generated in the second region where the second part of the cutting tool and the workpiece are in contact. The processing apparatus according to feature 1.

5. In a cutting tool, a first portion having a relief face and a second portion having a rake face are electrically insulated or made impassable by an insulating layer or a high-resistance layer. The processing apparatus according to feature 4.

6. The monitoring unit monitors the processing state using the difference between the thermoelectric voltage generated in the first region and the thermoelectric voltage generated in the second region. The processing apparatus according to feature 4.

7. A cutting tool having an insulating layer or a high-resistance layer on at least a portion of its surface and / or inside, or a rotating mechanism for rotating a spindle to which a workpiece is attached, A movement control unit that controls the relative movement of the cutting tool with respect to the workpiece, A monitoring unit monitors the machining state using the contact resistance in the contact area where the surface of the cutting tool and the workpiece come into contact during machining. A processing device equipped with the following features.

8. The cutting tool has an insulating layer or a high-resistance layer formed on its rake face. The monitoring unit monitors the machining state using the contact resistance in the contact area where the flank surface, which does not have an insulating layer or a high-resistance layer, comes into contact with the workpiece. The processing apparatus according to feature 7.

9. The cutting tool has an insulating layer or a high-resistance layer inside, and the first part and the second part of the cutting tool are electrically insulated or made less conductive by the internal insulating layer or high-resistance layer. The monitoring unit monitors the machining state using the sum of the contact resistance in a first region where the first part of the cutting tool and the workpiece are in contact, and the contact resistance in a second region where the second part of the cutting tool and the workpiece are in contact. The processing apparatus according to feature 7.

10. An insulating layer or a high-resistance layer is provided on the surfaces of the first and second parts. The processing apparatus according to feature 9.

11. The monitoring unit monitors the processing state using the thermoelectric voltage generated in the contact area instead of, or in addition to, the contact resistance. The processing apparatus according to feature 7.

12. A cutting tool, An insulating layer or high-resistance layer provided on at least a portion of the surface and / or inside the cutting tool, An electrical contact for connecting a circuit for measuring the thermoelectric power generated in the contact area between the cutting tool and the workpiece, or the contact resistance in said contact area, A cutting tool characterized by having the following features.

13. An insulating layer or high-resistance layer is formed on the rake face of the cutting tool. The cutting tool according to feature 12.

14. An insulating layer or high-resistance layer is provided inside the cutting tool to electrically insulate or make it difficult for the first and second parts of the cutting tool to conduct electricity. The cutting tool according to feature 12.

15. The insulating layer or high-resistance layer electrically insulates or makes it difficult for the first portion having a relief surface and the second portion having a scoop surface to conduct electricity. The cutting tool according to feature 12.

16. The insulating layer or high-resistance layer electrically insulates or makes electrical conductivity difficult between the cutting edge portion that generates the finished surface and the cutting edge portion that removes material. The cutting tool according to feature 12.

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