Processing equipment, processing status monitoring method, and cutting tool

Abstract

To provide a technique for monitoring a processing state by utilizing a principle of a tool-material to be cut thermocouple method.SOLUTION: A rotating mechanism 11 rotates a spindle 10 mounted with a cutting tool 20 or with a material 30 to be cut. A movement control part 102 controls relative movement of the cutting tool 20 with respect to the material 30 to be cut. A monitoring part 104 monitors a processing state, while using thermoelectromotive force generated at a plurality of contact points at which the cutting tool 20 contacts the material 30 to be cut, during rotation of the spindle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a processing apparatus, a method for monitoring the processing state, and a cutting tool. [Background technology]

[0002] The tool-workpiece thermocouple method is a known technique for measuring the cutting edge temperature of a tool during machining. This method utilizes the Seebeck effect, where a temperature difference between the junctions of a loop made of two types of conductors generates a thermoelectric voltage (EMF) between the junctions, causing a current to flow through the loop. The tool cutting edge temperature (cutting temperature) is measured from the thermoelectric voltage generated between the tool and the workpiece. Since the thermoelectric voltage is determined by the temperatures of the two junctions and the materials of the two types of conductors, the cutting temperature can be determined from a pre-prepared temperature calibration curve by measuring the thermoelectric voltage. Although the main component of cutting tool materials is generally nonmetallic, they often contain conductive binders, making it possible to measure the thermoelectric voltage.

[0003] Non-Patent Document 1 discloses a structure for realizing the tool-workpiece thermocouple method, which uses mercury contacts for the electrical contacts between the rotating spindle and the fixed structure, and employs electrical insulating components to prevent short circuits between the tool and the workpiece. Non-Patent Document 2 also discloses a structure for realizing the tool-workpiece thermocouple method, which uses slip rings for the electrical contacts between the rotating spindle and the fixed structure, and employs electrical insulating components to prevent short circuits between the tool and the workpiece. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Milton C. Shaw, “Metal Cutting Principles”, Claendon Press Oxford, 1984, p.252 [Non-Patent Document 2] Itaru Yamazaki, "Machining Characteristics in Intermittent Cutting of High-Hardness Materials," Nachi Technical Report - Machining, Fujikoshi Corporation, Oct 2011, Vol.23A2 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The technologies disclosed in Non-Patent Documents 1 and 2 both require modification of the spindle because they involve installing electrical contacts on the rear end of the spindle, which is costly. Furthermore, the use of mercury poses safety concerns, and slip rings are difficult to use on high-speed rotating spindles. Therefore, there is a need for the development of a technology that can easily monitor the machining process without modifying the spindle or using mercury or slip rings.

[0006] This disclosure is made in light of these circumstances and aims to provide a technology for monitoring the state of machining using the principle of the tool-workpiece thermocouple method. [Means for solving the problem]

[0007] To solve the above problems, 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, 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 thermoelectric power generated at a plurality of contact points where the cutting tool and the workpiece come into contact during spindle rotation.

[0008] A machining state monitoring method in another aspect of the present disclosure includes the steps of measuring the difference in thermoelectric power generated at a plurality of contact points where a cutting tool and a workpiece come into contact, and monitoring the machining state using the difference in thermoelectric power generated at the plurality of contact points.

[0009] A cutting tool in yet another aspect of the present disclosure comprises a plurality of conductive contact members that come into contact with a workpiece when machining the workpiece, a fixing member to which the plurality of contact members are fixed, an insulating member that insulates the plurality of contact members from each other, and a conductive member connected to at least one of the contact members.

[0010] 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]

[0011] [Figure 1] This is a diagram showing the schematic configuration of the processing apparatus according to the embodiment. [Figure 2] This figure shows examples of cutting tools. [Figure 3] This figure shows experimental results illustrating the relationship between cutting temperature and cutting speed. [Figure 4] This figure shows experimental results illustrating the relationship between cutting temperature and feed rate. [Figure 5] This figure shows examples of cutting tools. [Figure 6] This figure shows an example of a circuit that measures voltage at multiple contact points. [Figure 7] This figure shows examples of cutting tools. [Figure 8] This figure shows examples of cutting tools. [Modes for carrying out the invention]

[0012] Figure 1 shows an example of the schematic configuration of the machining apparatus 1 of the embodiment. The machining apparatus 1 of the embodiment is a lathe that rotates a workpiece 30 attached to a spindle 10 via a chuck 31, causing the cutting edge of a cutting tool 20 to cut into the rotating workpiece 30. The cutting tool 20 comprises a plurality of conductive shanks 24a, 24b, a plurality of conductive cutting edges 23a, 23b, and an insulating member 25 that insulates between the cutting edges 23a and 23b. The shanks 24a, 24b are fixing members that fix the tip (blade portion) having the cutting edge, and the cutting edges 23a, 23b are fixed to the shanks 24a, 24b, respectively. The shanks 24a, 24b may be connected by the insulating member 25 and formed integrally, and the cutting tool 20 may have three or more cutting edges. In this embodiment, it is assumed that the cutting edges 23a and 23b of the cutting tool 20 and the workpiece 30 are made of different materials and are different types of conductors, and during cutting, the workpiece 30 is cut simultaneously by multiple cutting edges 23a and 23b.

[0013] The machining apparatus 1 comprises a spindle housing 12 and a feed mechanism 21 on a bed 2 that moves the cutting tool 20 relative to the workpiece 30. The cutting tool 20 is fixed to a tool fixing part 22, and the tool fixing part 22 is movably supported by the feed mechanism 21. In the machining apparatus 1 shown in Figure 1, the feed mechanism 21 has a mechanism that moves the tool fixing part 22 in the X, Y, and Z axis directions, thereby moving the cutting tool 20 relative to the workpiece 30. The feed mechanism 21 may be configured to include motors and ball screws for each axis. In another example of the machining apparatus 1, 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.

[0014] 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. Note that the rotation mechanism 11 may be a built-in motor incorporated in the main shaft 10 and directly drive the main shaft 10.

[0015] The machining apparatus 1 of the embodiment has a function of monitoring the machining state by using the thermoelectric power generated at a plurality of contact points where the cutting tool 20 and the workpiece 30 contact during rotation of the main shaft. In the embodiment, the plurality of cutting edges 23a and 23b are contact members that contact the workpiece 30 during machining, and simultaneously machine the workpiece 30 at the plurality of contact points 50a and 50b. At this time, as the temperatures of the contact points 50a and 50b become high, a thermoelectric power (voltage) is generated between each of the plurality of cutting edges 23a and 23b and the workpiece 30. In the cutting tool 20, the conductive member 42a electrically connects the cutting edge 23a and the measuring unit 45, and the conductive member 42b electrically connects the cutting edge 23b and the measuring unit 45. The conductive member 42a and the conductive member 42b may be wires coated with an insulator on the outside, and may be disposed inside the shanks 24a and 24b, respectively. The measuring unit 45 measures the difference between the thermoelectric power generated between the cutting edge 23a and the workpiece 30 and the thermoelectric power generated between the cutting edge 23b and the workpiece 30.

[0016] In FIG. 1, the measuring unit 45 is shown as being provided outside the cutting tool 20. However, it is preferable that the cutting tool 20 includes the measuring unit 45 and the measuring unit 45 is provided inside the cutting tool 20. In this case, the cutting tool 20 incorporates a measuring unit 45 that measures the difference in the thermoelectromotive force generated at the plurality of cutting edges 23a and 23b during machining. Note that the measuring unit 45 may be provided in the processing apparatus 1. In this case, the cutting tool 20 includes terminals that connect to the ends of the conductive members 42a and 42b. When the cutting tool 20 is attached to the processing apparatus 1, a wiring extending from the measuring unit 45 in the processing apparatus 1 is connected to the terminals, and the measuring unit 45 in the processing apparatus 1 measures the difference in the thermoelectromotive force generated at the plurality of cutting edges 23a and 23b.

[0017] The control unit 100 includes a spindle 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 measuring unit 45, and a monitoring unit 104 that monitors the machining state using the voltage acquired by the acquisition unit 103.

[0018] Generally, most rotary tools have a plurality of cutting edges (referred to as multi-edge tools), and multi-edge tools may be applied to fixed tools (typically turning tools) for the purpose of increasing efficiency, reducing static / dynamic displacement (also called balanced cutting, etc.), and stabilizing chatter vibration. In the embodiment, a method for monitoring the machining state from the difference in the thermoelectromotive force generated at a plurality of contact points (cutting points) during machining by insulating between the cutting edges of the multi-edge tool is proposed.

[0019] Each element described as a functional block of the control unit 100 can be configured hardware-wise by circuit blocks, memories, other LSIs, CPUs, etc., and software-wise by system software, application programs loaded into the memory, etc. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by only hardware, only software, or combinations thereof, and are not limited to any of them.

[0020] The measuring unit 45 measures the thermoelectric power V generated due to the cutting temperature between the cutting edge 23a and the workpiece 30. A The thermoelectric power V generated due to the cutting temperature between the cutting edge 23b and the workpiece 30. B The difference V (=V A -V B The unit 103 acquires the voltage V measured by the measurement unit 45, and the monitoring unit 104 uses the voltage V to monitor the state of the cutting process.

[0021] Figure 2(a) shows another example of a cutting tool 20. The cutting tool 20 shown in Figure 2(a) is attached to the spindle 10 and comprises a conductive holder 26, a plurality of conductive cutting edges 23a, 23b, and an insulating member 25 that insulates between the cutting edges 23a and 23b. The holder 26 is a fixing member that fixes the tip (blade portion) having the cutting edges, and the cutting edges 23a, 23b are fixed to the holder 26. The cutting tool 20 shown in Figure 2(a) is a boring multi-edge tool and has two cutting edges 23a, 23b at positions of different diameters. When the cutting tool 20 has N cutting edges 23, it is preferable that adjacent cutting edges are positioned at rotational angle positions separated by (360° / N). In this example, the insulating member 25 is provided between the cutting edge 23a and the holder 26 to insulate between the cutting edge 23a and the cutting edge 23b, but it may also be provided between the cutting edge 23b and the holder 26.

[0022] The conductive member 42a electrically connects the cutting edge 23a and the measuring section 45, and the conductive member 42b electrically connects the cutting edge 23b and the measuring section 45. The conductive members 42a and 42b may be conductors coated with an insulator on the outside, and may be arranged inside the holder 26. The measuring section 45 measures the difference between the thermoelectric voltage generated between the cutting edge 23a and the workpiece 30 and the thermoelectric voltage generated between the cutting edge 23b and the workpiece 30. The measuring section 45 may be provided inside the cutting tool 20 or outside the cutting tool 20.

[0023] Figure 2(b) shows another example of the cutting tool 20. The cutting tool 20 shown in Figure 2(b) is attached to the spindle 10 and comprises a conductive holder 26, a plurality of conductive cutting edges 23a, 23b, and an insulating member 25 that insulates between the cutting edges 23a and 23b. The holder 26 is a fixing member that fixes the tip (blade portion) having the cutting edges, and the cutting edges 23a, 23b are fixed to the holder 26. In the cutting tool 20 shown in Figure 2(b), the cutting edges 23a are countersinking edges, and the cutting edges 23b are drills, and a plurality of cutting edges 23a may be provided at different rotational angle positions. The insulating member 25 may be provided between the cutting edges 23a and the holder 26, or between the cutting edges 23b and the holder 26.

[0024] The conductive member 42a electrically connects the cutting edge 23a and the measuring section 45, and the conductive member 42b electrically connects the cutting edge 23b and the measuring section 45. The conductive members 42a and 42b may be conductors coated with an insulator on the outside, and may be arranged inside the holder 26. The measuring section 45 measures the difference between the thermoelectric voltage generated between the cutting edge 23a and the workpiece 30 and the thermoelectric voltage generated between the cutting edge 23b and the workpiece 30. The measuring section 45 may be provided inside the cutting tool 20 or outside the cutting tool 20.

[0025] Figures 3 and 4 below show experimental results measuring the effect of cutting speed and cutting thickness on cutting temperature. Figure 3(a) shows the relationship between cutting temperature and tool angle when cutting at multiple cutting speeds. The cutting conditions for this experiment were as follows: • Cutting method: Down cut, dry machining ·Work material: S45C ·Tool material: Cemented carbide • Twist angle: 0 degrees ·Tool diameter: 20mm Feed rate: 0.1 mm / blade • Axial cut: 6mm Radial cut depth Rd: 0.5 mm When the angle at which the cutting edge is closest to the workpiece during a down cut is defined as 360 degrees, the angle range in which the cutting edge processes the workpiece (tool angle range) was approximately 340 degrees to approximately 360 degrees. The experimental results in Figure 3(a) show that the cutting temperature increases with increasing cutting speed.

[0026] Figure 3(b) shows the relationship between cutting temperature and cutting speed when cutting with multiple radial cuts. As shown in Figure 3(b), the relationship between cutting temperature and cutting speed follows a power law.

[0027] Figure 4(a) shows the relationship between cutting temperature and tool angle when cutting with multiple feed rates. The feed rate correlates with the cutting thickness; as the feed rate increases, the cutting thickness increases, and as the feed rate decreases, the cutting thickness also decreases. The cutting conditions for this experiment were as follows: • Cutting method: Down cut, dry machining ·Work material: S45C ·Tool material: Cemented carbide • Twist angle: 0 degrees ·Tool diameter: 20mm ·Cutting speed: 314.2m / min • Axial cut: 6mm Radial cut depth Rd: 0.5 mm The experimental results in Figure 4(a) show that the larger the feed rate, which is correlated with the cutting thickness, the higher the cutting temperature.

[0028] Figure 4(b) shows the relationship between cutting temperature and feed rate. As shown in Figure 4(b), the relationship between cutting temperature and feed rate follows a power law, and it can be seen that the relationship between cutting temperature and cut thickness also follows a power law.

[0029] From the experimental results shown in Figures 3 and 4, it is confirmed that the cutting temperature is proportional to a power of the cutting speed and also to a power of the cut thickness. In the machining process shown in Figure 1, comparing the cutting speeds at contact point 50a and contact point 50b, since contact point 50a is located radially outward from contact point 50b, the cutting speed at contact point 50a is faster. Also, since the cut thickness depends on the cutting edge shape and radial depth of cut, the cut thickness at contact point 50a and contact point 50b is generally different. Therefore, in the machining process shown in Figure 1, the cutting temperature at contact point 50a and the cutting temperature at contact point 50b are different, and the measuring unit 45 measures this temperature difference.

[0030] In the cutting tool 20 shown in Figure 1, when the cutting edge 23b vibrates and the cutting thickness increases or decreases, the cutting temperature also increases or decreases accordingly. The measuring unit 45 measures the difference between the thermoelectric power caused by the cutting temperature between the cutting edge 23a and the workpiece 30 and the thermoelectric power caused by the cutting temperature between the cutting edge 23b and the workpiece 30, so its measured voltage V vibrates with the increase or decrease in the cutting temperature between the cutting edge 23b and the workpiece 30. The monitoring unit 104 detects that the measured voltage V is vibrating based on the time change of the measured voltage V and determines that at least one of the cutting edge 23a or the cutting edge 23b is vibrating.

[0031] Furthermore, in the cutting tool 20 shown in Figure 2(a), when vibration occurs between the holder 26 and the workpiece 30, the cutting thickness by the cutting edge 23a and the cutting edge 23b increase or decrease. At this time, because the rotational angle positions on which the cutting edges 23a and 23b are mounted are different, the phases of the variation in cutting thickness by the cutting edge 23a and the variation in cutting thickness by the cutting edge 23b are different, and as a result, the amplitude of the difference in cutting temperature at the contact point 50a and the contact point 50b increases. The monitoring unit 104 determines from the vibrating voltage V that at least one of the cutting edges 23a or 23b is vibrating relative to the workpiece 30. Alternatively, a predetermined threshold Ath may be set for the vibration amplitude of the voltage V (the absolute value of the difference between the maximum and minimum values), and if the vibration amplitude of the voltage V is greater than or equal to the predetermined threshold Ath, the monitoring unit 104 may determine that the cutting edges 23a and 23b are vibrating relative to the workpiece 30, that is, a vibration problem is occurring. As described above, the monitoring unit 104 can determine that at least one of the multiple cutting edges 23 is vibrating relative to the workpiece 30 based on the time change of the difference in thermoelectric power (measured voltage V) generated at multiple contact points.

[0032] In the cutting tool 20 shown in Figure 1, if the cutting edge 23a is an R-type bit, the average thickness of the material cut decreases as the depth of cut decreases. Therefore, if the outer diameter of the workpiece 30 is smaller than the ideal value (planned value), the cutting temperature at the cutting edge 23a (the thermoelectric voltage between the tool and the workpiece corresponds to the average temperature of the contact area between them) will be lower than the originally planned temperature. The monitoring unit 104 holds a reference value Vref that should be measured when cutting is performed on a workpiece 30 with an ideal shape, and if the absolute value of (measured voltage V - reference value Vref) exceeds a predetermined value, it may be determined that the error in the outer diameter of the workpiece 30 is greater than the allowable value. Alternatively, the monitoring unit 104 may determine that the outer diameter of the workpiece 30 is greater than the upper limit of the allowable range if (measured voltage V - reference value Vref) exceeds a first predetermined value, and that the outer diameter of the workpiece 30 is smaller than the lower limit of the allowable range if it falls below a second predetermined value (in this case, the reference value Vref > 0, the first predetermined value is a positive threshold, and the second predetermined value is a negative threshold). Note that if the outer diameter of the workpiece 30 is eccentric, the cutting thickness, which is correlated with the depth of cut of the cutting edge 23a, increases or decreases in synchronization with the spindle rotation, so the monitoring unit 104 may determine that the outer diameter is eccentric from the vibration component of the measured voltage V that is synchronized with the rotation.

[0033] In the cutting tool 20 shown in Figure 2(b), if a chip occurs on the cutting edge 23a, or if wear greater than that on the cutting edge 23b occurs, the cutting temperature at the cutting edge 23a rises due to the deterioration of the sharpness of the cutting edge 23a. In this case, the monitoring unit 104 can determine that there is an abnormality in the cutting edge 23a by detecting that the measured voltage V has increased. In particular, regarding chipping, the monitoring unit 104 may estimate that a chip has occurred in the cutting edge 23a by detecting that the measured voltage V during monitoring momentarily drops (due to a temporary decrease in cutting thickness due to chipping) and then increases immediately afterward.

[0034] Figure 5 shows another example of a cutting tool 20. The cutting tool 20 shown in Figure 5 is attached to the spindle 10 and comprises a conductive holder 26, a plurality of conductive cutting edges 23a, 23b, 23c, and insulating members 25a, 25b that insulate the cutting edges 23a, 23b, 23c from each other. The holder 26 is a fixing member that fixes the tip (blade portion) having the cutting edges, and the cutting edges 23a, 23b, 23c are fixed to the holder 26. The cutting tool 20 shown in Figure 5 is a face milling tool, and the plurality of cutting edges 23a, 23b, 23c are provided at the same radial position and at different rotational angle positions. In this example, the insulating member 25a is provided between the cutting edge 23a and the holder 26, and the insulating member 25b is provided between the cutting edge 23b and the holder 26, but the insulating part may be provided between the cutting edge 23c and the holder 26.

[0035] Conductive member 42a electrically connects the cutting edge 23a and the measuring section 45a, and conductive member 42b electrically connects the cutting edge 23c and the measuring section 45a. The measuring section 45a measures the difference between the thermoelectric power generated between the cutting edge 23a and the workpiece 30 and the thermoelectric power generated between the cutting edge 23c and the workpiece 30. Conductive member 42c electrically connects the cutting edge 23c and the measuring section 45b, and conductive member 42d electrically connects the cutting edge 23b and the measuring section 45b. The measuring section 45b measures the difference between the thermoelectric power generated between the cutting edge 23c and the workpiece 30 and the thermoelectric power generated between the cutting edge 23b and the workpiece 30. Conductive members 42a, 42b, 42c, and 42d may be conductors covered with an insulator on the outside, and each may be arranged inside the holder 26. Alternatively, another measuring unit 45 may measure the difference between the thermoelectric power generated between the cutting edge 23a and the workpiece 30 and the thermoelectric power generated between the cutting edge 23b and the workpiece 30. Another cutting edge 23 may be provided at a position offset by 180 degrees from the cutting edge 23c.

[0036] The monitoring unit 104 monitors the machining state based on the measured voltage Va measured by the measuring unit 45a and the measured voltage Vb measured by the measuring unit 45b. In the cutting tool 20 shown in Figure 5, if the shapes of the multiple cutting edges 23a, 23b, and 23c are the same and the radial positions of the multiple cutting edges 23a, 23b, and 23c are the same, then each cutting edge will be machined under the same conditions, and therefore the cutting temperature will be the same. For this reason, the monitoring unit 104 may determine that an abnormality has occurred in either the cutting edge 23a or the cutting edge 23c if the measured voltage Va is not approximately zero, and that an abnormality has occurred in either the cutting edge 23c or the cutting edge 23b if the measured voltage Vb is not approximately zero. In this way, the monitoring unit 104 may monitor the machining state based on the magnitude of the difference in thermoelectric power generated at multiple contact points.

[0037] In the milling process shown in Figure 5, the actual cutting thickness will differ due to mounting errors and shape errors of each cutting edge, resulting in temperature differences between contact points. Therefore, the monitoring unit 104 may monitor the measured voltages Va and Vb to determine if the cutting edge is eccentric. In this case, the monitoring unit 104 may estimate the difference in cutting thickness from the difference in thermoelectric power of adjacent cutting edges, and estimate the inward / outward movement (each eccentricity) of each cutting edge arranged in the circumferential direction by accumulating the estimated differences in cutting thickness between cutting edges arranged in the circumferential direction.

[0038] The boring tool shown in Figure 2(a) may have cutting edges 23 at three or more different radial positions. The monitoring unit 104 may use one cutting edge 23 as a reference edge and monitor the difference in thermoelectric power between it and the other cutting edges 23, or it may monitor the difference in thermoelectric power between any two cutting edges 23. The monitoring unit 104 may simultaneously monitor the difference in thermoelectric power of different combinations of cutting edges 23, or it may monitor them one by one by switching between them over time using a multiplexer or the like.

[0039] FIG. 6 shows an example of a circuit for measuring voltages at five contact points. Note that the number of contact points is for illustration and may be other than five. In this example, series circuits of thermoelectric powers and resistances generated at each contact point are connected in parallel, and the five contact points are divided into two groups, and the difference between the weighted averages V1 and V2 of the thermoelectric powers in each group is measured. In the example shown in FIG. 6, voltage E A is the thermoelectric power at contact point A, voltage E B is the thermoelectric power at contact point B, voltage E C is the thermoelectric power at contact point C, voltage E M is the thermoelectric power at contact point M, voltage E N is the thermoelectric power at contact point N, and contact points A, B, and C are classified into the first group, and contact points M and N are classified into the second group.

[0040] The weighted average V1 of the thermoelectric powers in the first group is derived by the following formula 1.

Equation

Equation

[0041] For example, when there is one cutting edge with high importance in processing among a plurality of cutting edges, by configuring the first group with only the cutting edge and the second group with the other plurality of cutting edges, the monitoring unit 104 can monitor the occurrence of abnormalities in the important cutting edge with high accuracy.

[0042] Figure 7 shows another example of a cutting tool 20. The cutting tool 20 shown in Figure 7 is attached to the spindle 10 and comprises a conductive holder 26, a conductive cutting edge 23a, a conductive guide pad 27, and an insulating member 25 that insulates the space between the cutting edge 23a and the guide pad 27. The holder 26 is a fixing member that fixes the tip (blade portion) having a cutting edge, and the cutting edge 23a is fixed to the holder 26. The guide pad 27 is provided to improve straightness during deep hole machining and rubs against the machined surface processed by the cutting edge 23a. In this example, the cutting edge 23a and the guide pad 27 are contact members that come into contact with the workpiece 30 during machining and come into contact with the workpiece 30 simultaneously. The insulating member 25 is provided between the guide pad 27 and the holder 26 to insulate the space between the cutting edge 23a and the guide pad 27, but it may also be provided between the cutting edge 23a and the holder 26.

[0043] The conductive member 42a electrically connects the cutting edge 23a and the measuring section 45, and the conductive member 42b electrically connects the guide pad 27 and the measuring section 45. The conductive members 42a and 42b may be conductors coated with an insulator on the outside and may be arranged inside the holder 26. The measuring section 45 measures the difference between the thermoelectric power caused by the cutting temperature at the cutting point where the cutting edge 23a cuts the workpiece 30 and the thermoelectric power caused by the friction temperature at the friction point where the guide pad 27 rubs against the workpiece 30. The measuring section 45 may be provided inside the cutting tool 20 or outside the cutting tool 20.

[0044] Figure 8 shows another example of a cutting tool 20. The cutting tool 20 shown in Figure 8 is attached to the spindle 10 and comprises a conductive holder 26, a conductive cutting edge 23a, a conductive brush 28, and an insulating member 25 that insulates the space between the cutting edge 23a and the brush 28. The holder 26 is a fixing member that secures the tip (blade portion) having the cutting edge, and the cutting edge 23a is fixed to the holder 26. The brush 28 rubs against the machined surface processed by the cutting edge 23a. In this example, the cutting edge 23a and the brush 28 are contact members that come into contact with the workpiece 30 during machining, and they come into contact with the workpiece 30 simultaneously. The insulating member 25 is provided between the brush 28 and the holder 26 to insulate the space between the cutting edge 23a and the brush 28, but it may also be provided between the cutting edge 23a and the holder 26.

[0045] The conductive member 42a electrically connects the cutting edge 23a and the measuring unit 45, and the conductive member 42b electrically connects the brush 28 and the measuring unit 45. The conductive members 42a and 42b may be conductors coated with an insulator on the outside, and may be arranged inside the holder 26. The measuring unit 45 measures the difference between the thermoelectric power caused by the cutting temperature at the cutting point where the cutting edge 23a cuts the workpiece 30 and the thermoelectric power caused by the friction temperature at the friction point where the brush 28 rubs against the workpiece 30. It is known that the friction temperature is mainly determined by the friction speed and the width in the friction direction, does not change much during cutting, and is generally much lower than the cutting temperature. Therefore, the measuring unit 45 can substantially measure the cutting temperature at the cutting edge 23a by measuring the difference between the thermoelectric power caused by the cutting temperature and the thermoelectric power caused by the friction temperature.

[0046] In the embodiment, when the holder 26 that fixes the cutting edge 23 rotates, the holder 26 may include a transmitting unit that transmits the voltage measured by the measuring unit 45 to the processing device 1. The transmitting unit may have a wireless communication function using a communication protocol such as Bluetooth® protocol or IEEE802.11 protocol, and may perform AD conversion on the voltage measured by the measuring unit 45 and transmit it to the processing device 1 in real time. It may also have an amplification unit and an anti-aliasing filter unit before AD conversion, and may have a power supply unit (e.g., battery, wireless power supply device) for them. The holder 26 may also have a memory that stores the voltage measured by the measuring unit 45 along with time information, and the voltage and time information may be read from the memory after the processing is completed.

[0047] 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.

[0048] 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, 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 thermoelectric power generated at a plurality of contact points where the cutting tool and the workpiece come into contact during spindle rotation.

[0049] According to this embodiment, it becomes possible to monitor the machining state without providing a contact structure on the spindle.

[0050] The monitoring unit may monitor the machining state using the difference in thermoelectric power generated at multiple contact points. In this case, the monitoring unit may monitor the machining state based on the time change of the difference in thermoelectric power generated at multiple contact points. Alternatively, the monitoring unit may monitor the machining state based on the magnitude of the difference in thermoelectric power generated at multiple contact points.

[0051] A machining state monitoring method in another aspect of the present disclosure includes the steps of measuring the difference in thermoelectric power generated at a plurality of contact points where a cutting tool and a workpiece come into contact, and monitoring the machining state using the difference in thermoelectric power generated at the plurality of contact points.

[0052] According to this embodiment, it becomes possible to monitor the state of processing by utilizing the thermoelectric voltage generated at multiple contact points.

[0053] A cutting tool in another aspect of the present disclosure comprises a plurality of conductive contact members that come into contact with a workpiece when machining the workpiece, a fixing member to which the plurality of contact members are fixed, an insulating member that insulates the plurality of contact members from each other, and a conductive member connected to at least one of the contact members.

[0054] By using a cutting tool of this type, the processing apparatus can easily monitor the processing state using the thermoelectric power generated at multiple contact points where the cutting tool contacts the workpiece.

[0055] The cutting tool may be equipped with a measuring unit connected to a conductive member to measure the difference in thermoelectric power generated at multiple contact members during machining. The cutting tool may also be equipped with a transmitting unit to transmit the measured difference in thermoelectric power. The measuring unit and / or transmitting unit may be provided on the holder or shank of the cutting tool.

[0056] The cutting tool may have terminals that connect to a conductive member, and when the cutting tool is attached to the processing device, the terminals may be connected to a voltage measuring unit in the processing device. The conductive member may also be provided inside the fixed member. [Explanation of Symbols]

[0057] 1... Machining device, 10... Spindle, 11... Rotation mechanism, 20... Cutting tool, 21... Feed mechanism, 23a, 23b, 23c... Cutting edge, 24a, 24b... Shank, 25, 25a, 25b... Insulating member, 26... Holder, 27... Guide pad, 28... Brush, 30... Workpiece, 31... Chuck, 42a, 42b, 42c, 42d... Conductive member, 45, 45a, 45b... Measurement unit, 50a, 50b... Contact point, 100... Control unit, 101... Spindle control unit, 102... Movement control unit, 103... Acquisition unit, 104... Monitoring unit.

Claims

1. A rotating mechanism that rotates the spindle to which a cutting tool or 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 based on the time variation of the difference in thermoelectric power generated at multiple contact points where the cutting tool simultaneously contacts the workpiece during spindle rotation, A processing device equipped with the following features.

2. A rotating mechanism that rotates the spindle to which a cutting tool or 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 difference in thermoelectric power generated at multiple contact points where multiple conductive contact members of the cutting tool simultaneously contact the workpiece during spindle rotation. A processing device equipped with the following features.

3. The monitoring unit estimates the difference in cutting thickness at multiple contact points using the difference in thermoelectric power generated at multiple contact points. The processing apparatus according to feature 2.

4. The monitoring unit estimates the difference in cutting thickness at multiple contact points based on the magnitude of the difference in thermoelectric power generated at multiple contact points. The processing apparatus according to feature 3.

5. A method for monitoring the state of processing, A step of measuring the difference in thermoelectric power generated at multiple contact points where a cutting tool simultaneously contacts the workpiece, A step of monitoring the processing state based on the time change of the difference in thermoelectric power generated at multiple contact points, A method for monitoring the processing state, characterized by having the following features.

6. A method for monitoring the state of processing, A step of measuring the difference in thermoelectric power generated at multiple contact points where multiple conductive contact members of a cutting tool simultaneously contact the workpiece, A step of monitoring the processing state using the difference in thermoelectric power generated at multiple contact points, A method for monitoring the processing state, characterized by having the following features.

7. The monitoring step involves estimating the difference in cut thickness at multiple contact points using the difference in thermoelectric power generated at multiple contact points. The processing state monitoring method according to feature 6.

8. A cutting tool, When machining a workpiece, multiple conductive contact members are used, each simultaneously in contact with the workpiece and generating a thermoelectric voltage. A fixing member to which multiple contact members are fixed, An insulating member that insulates between multiple contact members, It comprises multiple conductive members connected to multiple contact members, and a measuring unit for measuring the difference in thermoelectric power generated at multiple contact points where the multiple contact members simultaneously contact the workpiece, A cutting tool that uses the time variation of the difference in thermoelectric power generated at multiple contact points to monitor the state of machining.

9. A cutting tool, When machining a workpiece, a plurality of conductive contact members that simultaneously contact the workpiece, wherein each contact member generates a thermoelectric voltage at each contact point when it comes into contact with the workpiece, A fixing member to which multiple contact members are fixed, An insulating member that insulates between multiple contact members, Multiple conductive members connected to multiple contact members, and connected to a measuring unit that measures the difference in thermoelectric power generated at multiple contact points where the multiple contact members simultaneously contact the workpiece, A cutting tool characterized by having the following features.

10. A measuring unit connected to multiple conductive members to measure the difference in thermoelectric power generated at multiple contact points where multiple contact members simultaneously contact the workpiece during processing, A monitoring unit monitors the processing state based on the time variation of the difference in thermoelectric power generated at multiple contact points, and a transmitting unit transmits the measured difference in thermoelectric power to the monitoring unit. The cutting tool according to claim 9, characterized by comprising the following features.

11. The cutting tool according to claim 8 or 9, characterized in that it includes a terminal for connecting to the conductive member, to which a voltage measuring unit in the processing device is connected when the cutting tool is attached to the processing device.

12. The conductive member is provided inside the fixing member. The cutting tool according to feature 8 or 9.

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