Cutting device and condition monitoring method

Abstract

A state of a cutting device is monitored using a drive current supplied from an inverter to a spindle motor. The cutting device has a spindle motor that rotates a blade, an inverter that drives the spindle motor by vector control, and a monitoring section. The monitoring section acquires current information indicating a magnitude of a drive current including a q-axis current supplied from the inverter to the spindle motor, and monitors at least one of a state of the cutting device and a processing state of an object processed by the cutting device, based on the current information.

Description

Technical Field

[0001] The disclosed technology involves cutting devices and condition monitoring methods. Background Technology

[0002] As a technology related to cutting devices, the following technologies are known. For example, Patent Document 1 describes a cutting device that includes a workpiece worktable for holding and moving a workpiece and a frame housing a spindle capable of holding and rotating a blade.

[0003] Furthermore, the following technologies are known as related to system state monitoring. For example, Patent Document 2 describes a state monitoring device for a machine system, which includes a machine driven by a motor controlled by a motor control unit. This state monitoring device includes: a motor control internal value generation unit that generates motor control internal values ​​as state variables in the motor control unit based on current sensor information of the motor current; and a state estimation unit that calculates characteristic quantities within a predetermined time interval based on the motor control internal values ​​generated by the motor control internal value generation unit, and uses a statistical model to estimate state quantities representing the state of the machine system based on at least one of the characteristic quantities.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2023-148574 Patent Document 2: International Publication No. 2018 / 220751 The cutting device has a spindle motor that rotates the blade and an inverter that drives the spindle motor. The inverter can be controlled using either V / f control or vector control. V / f control is a method that keeps the ratio of the voltage to the frequency output from the inverter constant.

[0005] In vector control, the motor drive current is considered in terms of q-axis current and d-axis current. This method involves vector calculations to control the motor current direction. The q-axis current is the current component in the motor that contributes to torque generation, also known as torque current. The d-axis current is the current component that generates the magnetic field in the rotor, also known as magnetizing current.

[0006] In vector control, the motor speed or output torque is estimated based on the inverter's output current, thus requiring higher computational power compared to V / f control. Furthermore, the spindle motor's speed is often very high, for example, up to 60,000 rpm, requiring extremely high computational power to achieve vector control. Therefore, existing cutting devices generally employ V / f control, which can be implemented with relatively low computational power.

[0007] It was considered to use the drive current supplied from the inverter to the spindle motor to monitor the status of the cutting device or the processing status of the object being processed by the cutting device. However, through in-depth research, the inventors have realized that in the V / f control method, due to the low correlation between the motor load (torque) and the drive current, it is difficult to achieve the above-mentioned monitoring using the drive current. Summary of the Invention

[0008] The disclosed technology was developed in view of the above-mentioned problems, and its purpose is to achieve condition monitoring using the drive current supplied from the inverter to the spindle motor.

[0009] The disclosed technology involves a cutting apparatus comprising: a spindle motor that rotates a blade, an inverter that drives the spindle motor via vector control, and a monitoring unit. The monitoring unit acquires current information representing the magnitude of a drive current including a q-axis current supplied from the inverter to the spindle motor, and based on this current information, monitors at least one of the state of the cutting apparatus and the processing state of the object being processed by the cutting apparatus.

[0010] The monitoring unit can issue information based on the monitored status. The monitoring unit can also issue commands to control the operation of the cutting device based on the monitored status.

[0011] The monitoring unit can monitor the status of the spindle motor based on the current information when the object is not being processed. The monitoring unit can also monitor the installation status of the cutting tool on the spindle motor based on the current information when the object is not being processed. The monitoring unit can also monitor the water immersion status of the cutting tool caused by water sprayed onto it based on the current information when the object is not being processed. The monitoring unit can also monitor the status of the cutting tool based on the current information when processing the object.

[0012] The monitoring unit can detect the occurrence of machining abnormalities in the object based on the current information during machining. The monitoring unit can also detect damage to the cutting tool based on the current information during machining.

[0013] The disclosed technology involves a state monitoring method as follows: acquiring current information representing the magnitude of the drive current, including the q-axis current supplied to the spindle motor, when the spindle motor is driven to rotate the blade of the cutting device by vector control; and monitoring the state of the cutting device or the processing state of the object processed by the cutting device based on the current information.

[0014] Invention Effects According to the publicly available technology, status monitoring is achieved using the drive current supplied from the inverter to the spindle motor. Attached Figure Description

[0015] Figure 1 This is a diagram illustrating an example of the structure of a cutting device according to an embodiment of the disclosed technology.

[0016] Figure 2 This is a functional block diagram illustrating an example of a system architecture for implementing vector control in an inverter.

[0017] Figure 3 This is a diagram used to illustrate the q-axis and d-axis currents used in vector control.

[0018] Figure 4A This is a graph showing an example of the relationship between the spindle motor speed and the drive current value when the spindle motor is driven by V / f control.

[0019] Figure 4B This is a graph illustrating an example of the relationship between the spindle motor speed and the drive current value when the spindle motor is driven by vector control.

[0020] Figure 5 This is a diagram illustrating an example of the hardware structure of the monitoring unit involved in an embodiment of the disclosed technology.

[0021] Figure 6A This is a flowchart illustrating an example of a processing flow implemented by executing a status monitoring program via a CPU, as per an embodiment of the disclosed technology.

[0022] Figure 6B This is a flowchart illustrating another example of a processing flow implemented by executing a status monitoring program via a CPU, as per an embodiment of the disclosed technology.

[0023] Figure 7 It is a graph showing the relationship between the rotational speed of each of the multiple spindle motors and the current value of the drive current when the workpiece is not being processed.

[0024] Figure 8 This is a graph showing an example of the relationship between the spindle motor speed and the drive current value when the workpiece is not being processed.

[0025] Figure 9A This is a diagram showing a spindle motor that is not installed at all.

[0026] Figure 9B This is a diagram showing a spindle motor with an inner flange installed.

[0027] Figure 9C This is a diagram showing a spindle motor with an inner flange and blades mounted on it.

[0028] Figure 10It is a graph showing the relationship between the spindle motor speed and the drive current value when no workpiece is being machined, under various conditions where the amount of cutting water sprayed onto the cutting blade per unit time is changed.

[0029] Figure 11 This is a diagram showing the state of water being sprayed onto the cutting blade.

[0030] Figure 12 It is a graph showing the relationship between the spindle motor speed and the drive current value when no workpiece is being machined, under various conditions where the amount of cooling water sprayed onto the blade per unit time is changed.

[0031] Figure 13 This is a diagram showing the state of water being sprayed onto the cutting blade.

[0032] Figure 14 This is a waveform showing an example of the time-lapse of the current value of the drive current when processing an object.

[0033] Figure 15 This is a waveform showing an example of the time-lapse of the current value of the drive current when processing an object.

[0034] Figure 16 Is with Figure 15 The waveform shown corresponds to the image of the object being processed.

[0035] Figure 17 This is a waveform showing an example of the time-lapse of the current value of the drive current when processing an object.

[0036] Figure 18 Is with Figure 17 The waveform shown corresponds to the image of the object being processed.

[0037] Explanation of reference numerals in the attached figures 10: Monitoring Department; 20: Inverter; 21: Testing Department; 22: Speed ​​control unit; 23: Current vector control algorithm; 24: Current control unit; 25: Drive circuit; 26: Current detector; 30: Spindle motor; 31: Inner flange; 32: Blade; 40: Speed ​​detector; 100: Cutting device; 101: CPU; 102: RAM; 103: Non-volatile memory; 104: Interface; 105: Monitor; 106: Bus; 110: Status monitoring program. Detailed Implementation

[0038] Hereinafter, an example of an embodiment of the disclosed technology will be described with reference to the accompanying drawings. Furthermore, the same reference numerals will be used to assign the same or equivalent constituent elements and parts to each drawing, and repeated descriptions will be omitted.

[0039] Figure 1 This is a diagram illustrating an example of the structure of a cutting apparatus 100 according to an embodiment of the disclosed technology. The cutting apparatus 100 is a device for processing a workpiece using a rotating blade (grinding wheel). Using the cutting apparatus 100, semiconductor wafers can be cut, or grooves can be formed on the surface of a glass plate.

[0040] The cutting apparatus 100 according to this embodiment includes a spindle motor 30, an inverter 20, and a monitoring unit 10. The spindle motor 30 rotates a blade (not shown). The inverter 20 drives the spindle motor 30 via vector control. The monitoring unit 10 acquires current information indicating the magnitude of the drive current supplied from the inverter 20 to the spindle motor, and based on the current information, monitors the state of the cutting apparatus 100 and the processing state of the object being processed by the cutting apparatus.

[0041] Figure 2 This is a functional block diagram illustrating an example of a system structure for implementing vector control in inverter 20. The detection unit 21 detects the rotational angular velocity ω and rotational angle θ of the spindle motor 30 based on the output of the speed detector 40 connected to the spindle motor 30. The speed control unit 22 controls the speed command value ω using proportional-integral control or the like. The deviation from the rotational angular velocity ω is amplified to generate the q-axis current command value i. q By controlling the q-axis current command value i q The rotational angular velocity ω is input into the current vector control algorithm 23 to obtain the d-axis current command value i. d The current control unit 24 generates a q-axis current command value i based on the rotation angle θ. q and d-axis current command value i d Three-phase current command value i after three-phase conversion a i b i c Additionally, the current control unit 24 generates a value i for adjusting the three-phase current indication. a i b i c The output current i of inverter 20 obtained by current detector 26 a i b i c The control signal with a difference of zero is supplied to the drive circuit 25.

[0042] Figure 3 This diagram illustrates the q-axis and d-axis currents used in vector control. The direction of the magnetic flux formed by the magnetic poles of the motor rotor (the central axis of the permanent magnets) is defined as the d-axis, and the axis orthogonal to it electrically and magnetically (the axis between the permanent magnets) is defined as the q-axis. Of the drive current supplied from the inverter 20 to the spindle motor 30, the current component that generates magnetic flux in the q-axis direction is the q-axis current, and the current component that generates magnetic flux in the d-axis direction is the d-axis current. The q-axis current is the current component in the spindle motor 30 that contributes to generating rotational torque, also known as the torque current. The d-axis current is the current component that generates a magnetic field in the rotor, also known as the magnetizing current. In vector control, the q-axis and d-axis currents are controlled independently.

[0043] In V / f control mode, the q-axis current and d-axis current are not controlled independently, which is detrimental to the continuous flow of the d-axis current that generates rotational torque, and it is consumed by heat. On the other hand, in vector control mode, for example, it is possible to control the d-axis current, which is detrimental to generating rotational torque, to zero, thereby suppressing the heat generation of the spindle motor 30.

[0044] Figure 4A and 4B These are graphs illustrating an example of the relationship between the spindle motor's rotational speed and the current value of the drive current supplied from the inverter to the spindle motor. Figure 4A This refers to the case where the spindle motor is driven using V / f control. Figure 4B This refers to the case where the spindle motor is driven using vector control. Figure 4B The diagram shows the current values ​​for the q-axis current alone, combined with the total current including the q-axis and d-axis currents. Figure 4A and 4B The intermittent peaks that occur during this process are accompanied by the acceleration of the spindle motor, and will not be discussed here.

[0045] The motor load (torque) increases with the spindle motor speed, but in V / f control mode, such as Figure 4AAs shown, the drive current does not exhibit a monotonically increasing behavior as the spindle motor speed increases. That is, in V / f control mode, the correlation between the motor load (torque) and the drive current is low. This is because in V / f control mode, the d-axis current, which is unfavorable for generating rotational torque, continues to flow, while the q-axis current, which helps generate rotational torque, is masked by the d-axis current.

[0046] On the other hand, such as Figure 4B As shown, according to the vector control method, the spindle motor speed (load (torque)) has a high correlation with the drive current value, especially the q-axis current, which has a high correlation with the motor load (torque). This is because the q-axis current is a current component that contributes to generating rotational torque. Furthermore, according to the vector control method, since the d-axis current, which is detrimental to generating rotational torque, is suppressed, a high correlation with the motor load (torque) can be obtained even within the total current.

[0047] The state of the cutting device and the processing state of the workpiece processed by the cutting device are reflected in the motor load (torque). Therefore, the drive current in the vector control method reflects the state of the cutting device and the processing state of the workpiece. This means that the state of the cutting device and the processing state of the workpiece can be monitored using the drive current of the spindle motor driven by the vector control method. In the cutting device 100 of this embodiment, the state monitoring using the drive current of the spindle motor is achieved by the monitoring unit 10.

[0048] Figure 5 This diagram illustrates an example of the hardware structure of the monitoring unit 10. The monitoring unit 10 includes a CPU (Central Processing Unit) 101, RAM (Random Access Memory) 102, non-volatile memory 103, an interface 104, and a display 105. This hardware is connected to a bus 106. The monitoring unit 10 can also be housed inside the inverter 20 housing.

[0049] The display 105 may be a touch panel display. The monitoring unit 10 can communicate with the inverter 20 via the interface 104. The non-volatile memory 103 is a non-volatile storage medium such as a hard disk or flash memory. The status monitoring program 110 is stored in the non-volatile memory 103. The RAM 102 is the working memory for the CPU 101 to perform processing. The CPU 101 loads the status monitoring program 110 stored in the non-volatile memory 103 into the RAM 102 and performs processing according to the status monitoring program 110.

[0050] Figure 6A This is a flowchart illustrating an example of the processing flow implemented by CPU 101 through executing status monitoring program 110.

[0051] In step S1, CPU 101 acquires the current information supplied from inverter 20. The current information represents the magnitude (current value) of the drive current supplied from inverter 20 to spindle motor 30.

[0052] Inverter 20 uses the drive current I of each phase of spindle motor 30 obtained by current detector 26. a I b I c The inverter 20 calculates the magnitudes of the q-axis current and d-axis current using the magnitude of the q-axis current and the rotation angle θ of the spindle motor 30 obtained by the detection unit 21. The inverter 20 generates current information representing the calculated magnitudes of the q-axis current and d-axis current and supplies this information to the monitoring unit 10. The current information can also represent only the magnitude of the q-axis current. Alternatively, it can represent the magnitudes of both the q-axis and d-axis currents individually. Furthermore, it can also represent the combined magnitude of the q-axis and d-axis currents.

[0053] In step S2, the CPU 101 determines whether the drive current value is abnormal, for example, by comparing the drive current value represented by the current information obtained in step S1 with a threshold. As described above, the drive current in the vector control method reflects the state of the cutting device and the processing state of the workpiece. Therefore, an abnormal drive current means that the state of the cutting device or the processing state of the workpiece is abnormal. If the drive current value is determined to be abnormal, the process proceeds to step S3; if the drive current value is determined not to be abnormal, the routine ends.

[0054] In step S3, CPU 101 issues a specified message. This specified message may, for example, indicate an abnormality in the status of the cutting device 100 or the processing status of the workpiece. Alternatively, the specified message may include information indicating the content or cause of the abnormality, or a method for responding to the abnormality. Issuing the message may be done through display on monitor 105, illumination from a light, or sound output from a speaker, or a combination thereof. Furthermore, issuing the message may also be done by sending information to a terminal device (not shown) communicatively connected to the cutting device 100.

[0055] Figure 6B This is a flowchart illustrating another example of the processing flow implemented by CPU 101 through the execution of status monitoring program 110. Figure 6B In the flowchart shown, the processing in step S3 is similar to... Figure 6A The flowcharts shown are different. If the CPU101 determines that the current value of the drive current is abnormal, it can also issue a control command for controlling the operation of the cutting device in step S3.

[0056] The control command may be, for example, a command to reduce the speed of the spindle motor 30, or a command to limit the upper limit of the speed of the spindle motor 30. Alternatively, the control command may be a command to stop the rotation of the spindle motor 30. The control command is supplied to the inverter 20. The inverter 20, according to the control command, slows down, limits, or stops the rotation of the spindle motor 30.

[0057] The following describes the specific methods of status monitoring performed by the monitoring department 10.

[0058] <Monitoring the status of the spindle motor> Figure 7 It is a graph showing the relationship between the rotational speed of each of the multiple spindle motors and the current value of the drive current when the workpiece is not being processed. Figure 7 This diagram illustrates both the case of driving each of multiple spindle motors using V / f control and the case of driving each of multiple spindle motors using vector control. The current value in the vector control method is the q-axis current.

[0059] Under the V / f control method, the correlation between the spindle motor speed and the drive current is low, and the fluctuation of the current value is significant due to individual differences in the spindle motor. In the V / f control method, due to individual differences in the spindle motor (such as differences in coil performance and magnet strength), the d-axis current varies greatly, thus increasing the fluctuation of the current value.

[0060] On the other hand, according to vector control, the spindle motor speed is highly correlated with the drive current, and the fluctuations in current value caused by individual differences in the spindle motor are small. In vector control, since torque control based on q-axis current control is performed independently of the coil's performance and the magnet's magnetic force, current fluctuations caused by individual differences in the spindle motor can be suppressed. That is, according to vector control, the load state of the spindle motor is not obscured by individual differences in the spindle motor and is reflected in the drive current value.

[0061] Therefore, by using the drive current value, the spindle motor's status can be monitored regardless of individual differences, based on the vector control method. The spindle motor's status includes, for example, the integrity of the bearings or magnets. For instance, if an abnormality occurs in the spindle motor's bearings or magnets, the load on the spindle motor increases compared to normal operation. In this case, the drive current value increases at each speed compared to normal operation. Therefore, by, for example, determining a threshold value for the drive current, the integrity of the spindle motor 30's bearings or magnets can be verified.

[0062] When the status of the spindle motor 30 is monitored in the monitoring unit 10, Figure 6A and Figure 6B The details of each process in the flowchart shown are as follows.

[0063] In step S1, the CPU 101 acquires current information when no workpiece is being processed. This "current information when no workpiece is being processed" includes current information when the spindle motor 30 rotates but no workpiece is being processed, and current information when the spindle motor 30 stops but no workpiece is being processed. Furthermore, drive current continues to flow even when the spindle motor 30 is stopped. The current information may include multiple current values ​​corresponding to each of a plurality of different rotational speeds.

[0064] In step S2, the CPU 101 determines whether the drive current value is abnormal by comparing the drive current value represented by the current information obtained in step S1 with a threshold. This determination is equivalent to determining whether the spindle motor 30 is in an abnormal state. The threshold used for this determination can, for example, be set based on the drive current value of a healthy spindle motor 30. The threshold can include multiple current values ​​corresponding to each of a plurality of different rotational speeds. For example, if the drive current value represented by the current information obtained in step S1 is greater than the threshold, it is presumed that the spindle motor 30 is in an abnormal state, and the process proceeds to step S3.

[0065] In step S3, the CPU 101 issues a message indicating an abnormal state of the spindle motor 30. For example, text or icons indicating an abnormal state of the spindle motor 30 can also be displayed on the display 105. Alternatively, an abnormality can be indicated by an illuminated light or sound output from a speaker.

[0066] Additionally, in step S3, CPU 101 can issue a control command to reduce the speed of spindle motor 30, a control command to limit the upper limit of the speed of spindle motor 30, or a control command to stop the rotation of spindle motor 30. Inverter 20 reduces, limits, or stops the rotation of spindle motor 30 according to the control command.

[0067] <Monitoring of Blade Installation Status> Figure 8 This shows the case where nothing is installed on the spindle motor 30 (see reference). Figure 9A When the inner flange 31 is installed (refer to...) Figure 9B When the inner flange 31 and the blade 32 are installed (see reference) Figure 9C ) Obtain the curves showing the relationship between the spindle motor speed and the drive current (q-axis current) when the workpiece is not being processed.

[0068] In both cases, the drive current increases with the rotational speed of the spindle motor 30. This applies when nothing is installed on the spindle motor 30 (see reference). Figure 9A ) and in the case where the spindle motor 30 is equipped with an inner flange 31 (see Figure 9B The current values ​​are almost identical. On the other hand, when the spindle motor 30 is equipped with an inner flange 31 and a blade 32 (see...). Figure 9C Compared to the other two cases, the current value increases, and the higher the speed, the more significant the difference. This is because by installing the blade 32 on the spindle motor 30, the air resistance increases, and the load on the spindle motor 30 increases.

[0069] Based on the above results, it can be said that the installation status of the cutting tool on the spindle motor 30 can be monitored using the current value of the drive current. For example, by performing a threshold determination on the current value of the drive current, it is possible to determine whether a cutting tool is installed on the spindle motor 30.

[0070] While monitoring the installation status of the cutting tool on the spindle motor 30 in the monitoring unit 10. Figure 6A and Figure 6B The details of each process in the flowchart shown are as follows.

[0071] In step S1, the CPU 101 acquires current information when no workpiece is being processed. This "current information when no workpiece is being processed" includes current information when the spindle motor 30 rotates but no workpiece is being processed, and current information when the spindle motor 30 stops but no workpiece is being processed. Furthermore, drive current continues to flow even when the spindle motor 30 is stopped. The current information preferably includes current values ​​in the high-rotation region (e.g., above 50,000 rpm). The current information may include multiple current values ​​corresponding to each of a plurality of different rotational speeds.

[0072] In step S2, the CPU 101 determines whether the drive current value is abnormal by comparing the drive current value represented by the current information obtained in step S1 with a threshold. This determination is equivalent to determining whether the installation state of the blade on the spindle motor 30 is abnormal. The threshold used for this determination can, for example, be set based on the drive current value of the spindle motor 30 with the inner flange and blade installed. The threshold can include multiple current values ​​corresponding to each of a plurality of different rotational speeds. For example, if the drive current value represented by the current information obtained in step S1 is less than the threshold, it is presumed that no blade is installed on the spindle motor 30, and the process proceeds to step S3.

[0073] In step S3, CPU 101 issues a message indicating an abnormal installation status of the blade on spindle motor 30 (i.e., no blade is installed on spindle motor 30). For example, text or an icon indicating that no blade is installed on spindle motor 30 can be displayed on display 105. Alternatively, the abnormality can be indicated by an illuminated light or sound output from a speaker.

[0074] Additionally, in step S3, CPU 101 can issue a control command to reduce the speed of spindle motor 30, a control command to limit the upper limit of the speed of spindle motor 30, or a control command to stop the rotation of spindle motor 30. Inverter 20 reduces, limits, or stops the rotation of spindle motor 30 according to the control command.

[0075] <Monitoring the water immersion status of blades> Figure 10 This is a graph showing the relationship between the spindle motor speed and the drive current (q-axis current) when the amount of cutting water sprayed onto the cutting tool per unit time is varied, and the workpiece is not being machined. Figure 11 As shown, cutting water is sprayed onto the circumferential surface of the workpiece that is in contact with the cutting tool 32. Figure 10 The figures show the flow rates of cutting water per unit time as 0 L / min, 0.5 L / min, and 1.0 L / min.

[0076] When the water jet rate is 0.5 L / min, the drive current is higher at speeds below 40,000 rpm than when no water is supplied (0 L / min). Above 40,000 rpm, the drive current is approximately the same as when no water is supplied. When the water reaches the blade 32, the load on the spindle motor 30 increases, and the drive current should be higher than when no water is supplied. The fact that the drive current is approximately the same as when no water is supplied means that the water is not reaching the blade 32. With a water jet rate of 0.5 L / min, in the region above 40,000 rpm, the water is thrown away by the airflow around the rotating blade 32, presumably indicating that the water is not reaching the blade 32. Therefore, it is insufficient to say that the water jet rate is 0.5 L / min.

[0077] On the other hand, when the cutting water ejection rate is 1.0 L / min per unit time, the current value of the drive current is greater throughout the rotating region than when no cutting water is supplied. This means that the cutting water reaches the cutting tool 32 throughout the rotating region. In other words, it can be said that 1.0 L / min is sufficient as the cutting water ejection rate per unit time.

[0078] Based on the above results, it can be stated that the current value of the drive current can be used to monitor the water immersion state of the cutting tool caused by the cutting water. For example, by setting a threshold value for the drive current, it is possible to determine whether the water immersion state of the cutting tool caused by the cutting water is appropriate. Additionally, the amount of cutting water ejected can be controlled to ensure that the water immersion state of the cutting tool is appropriate.

[0079] Figure 12 This is a graph showing the relationship between the spindle motor speed and the drive current (q-axis current) when the amount of cooling water sprayed onto the cutting tool per unit time is varied, and the workpiece is not being machined. Figure 13 As shown, cooling water is sprayed onto the side of the blade 32. Figure 12 The figures show the cooling water spray rate per unit time as 0 L / min, 0.5 L / min, and 1.0 L / min.

[0080] When the cooling water ejection rate is 0.5 L / min per unit time, the drive current is greater than that when no cooling water is supplied (ejection rate 0 L / min) at speeds below 40,000 rpm. Above 40,000 rpm, the drive current is approximately the same as that when no cooling water is supplied. When cooling water reaches the blade 32, the load on the spindle motor 30 increases, and the drive current should be greater than when no cooling water is supplied to the blade 32. The fact that the drive current is approximately the same as that when no cooling water is supplied means that the cooling water has not reached the blade 32. With a cooling water discharge rate of 0.5 L / min per unit time, in the region above 40,000 rpm, the cooling water is thrown away by the airflow accompanying the rotating blade 32, presumably indicating that the cooling water has not reached the blade 32. Therefore, it is insufficient to say that the cooling water ejection rate is 0.5 L / min per unit time.

[0081] On the other hand, when the cooling water ejection rate is 1.0 L / min per unit time, the current value of the drive current is greater throughout the rotating region than when no cooling water is supplied. This means that cooling water reaches the blade 32 throughout the rotating region. In other words, it can be said that 1.0 L / min is sufficient as the cooling water ejection rate per unit time.

[0082] Based on the above results, it can be stated that the current value of the drive current can be used to monitor the blade immersion state caused by cooling water. For example, by setting a threshold value for the drive current, it is possible to determine whether the cooling water immersion state of the blade is appropriate. Additionally, the amount of cooling water sprayed can be controlled to ensure that the blade immersion state caused by cooling water is appropriate.

[0083] When monitoring the cutting tool immersion status caused by cutting water or cooling water in the monitoring unit 10, Figure 6A and Figure 6B The details of each process in the flowchart shown are as follows.

[0084] In step S1, the CPU 101 acquires current information when no workpiece is being processed. This "current information when no workpiece is being processed" includes both cases where the spindle motor 30 rotates but no workpiece is being processed, and cases where the spindle motor 30 stops but no workpiece is being processed. Furthermore, even when the spindle motor 30 stops, drive current continues to flow. The current information preferably includes current values ​​in the high-rotation region (e.g., above 50,000 rpm). The current information may include multiple current values ​​corresponding to each of a plurality of different rotational speeds.

[0085] In step S2, the CPU 101 determines whether the current value of the drive current is abnormal by comparing the current value of the drive current represented by the current information obtained in step S1 with a threshold. This determination is equivalent to determining whether the blade immersion state caused by the cutting water or cooling water is appropriate. The threshold used for this determination can, for example, be set based on the current value of the drive current when no cutting water or cooling water is supplied to the blade (ejection rate 0 L / min). The threshold can include multiple current values ​​corresponding to each of a plurality of different rotational speeds. For example, if the current value of the drive current represented by the current information obtained in step S1 is less than the threshold, it is presumed that the blade immersion state caused by the cutting water or cooling water is abnormal, and the process proceeds to step S3.

[0086] In step S3, CPU 101 issues a message indicating an abnormal blade immersion status caused by cutting water or cooling water (i.e., insufficient cutting water or cooling water output). For example, text or icons indicating insufficient cutting water or cooling water output can be displayed on display 105. Alternatively, the abnormality can be indicated by light illumination or sound output from a speaker.

[0087] Additionally, in step S3, CPU 101 can issue a control command to reduce the speed of spindle motor 30, limit the upper limit of spindle motor 30's speed, or stop the rotation of spindle motor 30. Inverter 20, based on the control command, reduces, limits, or stops the rotation of spindle motor 30. Furthermore, in step S3, CPU 101 can also issue a control command to control the amount of cutting water or cooling water to ensure the drive current reaches a target value. The target value can be set based on the drive current value when the cutting tool is normally submerged in water due to the cutting water or cooling water.

[0088] <Monitoring of Blade Wear> Figure 14 This is a waveform showing the time-lapse of the drive current (q-axis current) during machining of an object. The machining operation involves creating a 1mm deep linear groove in a glass plate. The peaks of the waveform correspond to the state of cutting the object. The troughs correspond to the state of switching the machining line, which will not be discussed here.

[0089] Focusing on the peak portion of the waveform, the drive current increases with the cumulative number of finished lines. As the cumulative number of finished lines increases, the cutting tool wear intensifies, and its cutting capability decreases. This decrease in cutting capability is compensated for by an increase in the spindle motor torque; therefore, when the cutting capability of the cutting tool decreases, the drive current increases. In other words, as the cutting tool wear intensifies, the drive current increases.

[0090] In summary, this can be described as using the current value of the drive current to monitor the wear condition of the cutting tool. For example, by determining a threshold value for the drive current, it is possible to detect whether the wear condition of the cutting tool is at or near its limit.

[0091] The conventional method for managing cutting tools is to replace or repair them when the cumulative number or length of completed machining lines reaches a predetermined upper limit. This includes tools with sufficient cutting capacity remaining, all of which are considered for replacement or repair. Because the upper limit provides a margin, it is assumed that most tools with sufficient cutting capacity are replaced or repaired. On the other hand, by monitoring the wear condition of the cutting tools using the drive current, a decrease in actual cutting capacity can be detected. Therefore, tools with sufficient cutting capacity can be avoided from being replaced or repaired, reducing the frequency of tool replacement or repair.

[0092] When monitoring the wear condition of the blades in the monitoring department Figure 6A and Figure 6BThe details of each process in the flowchart shown are as follows.

[0093] In step S1, CPU 101 acquires current information during the processing of the workpiece. Current information is continuously acquired during the processing of the workpiece.

[0094] In step S2, the CPU 101 determines whether the drive current value is abnormal by comparing the current value (peak portion) of the drive current represented by the current information obtained in step S1 with a threshold. This determination is equivalent to determining whether the wear state of the cutting tool is at or near its limit. The threshold used for this determination can be set, for example, based on the current value of the drive current when machining the same workpiece under the same machining conditions, using a cutting tool whose wear state is at or near its limit. For example, if the current value of the drive current represented by the current information obtained in step S1 reaches the threshold, it is presumed that the wear state of the cutting tool is at or near its limit, and the process proceeds to step S3.

[0095] In step S3, CPU 101 sends information indicating that the blade wear condition is at or near its limit. For example, text or icons indicating that the blade wear condition is at or near its limit can be displayed on display 105. Alternatively, an abnormality can be indicated by light illuminating the blade or by sound output from a speaker.

[0096] Additionally, in step S3, CPU 101 may also issue a control command to reduce the speed of spindle motor 30, limit the upper limit of the speed of spindle motor 30, or stop the rotation of spindle motor 30. Inverter 20, according to the control command, reduces, limits, or stops the rotation of spindle motor 30.

[0097] Alternatively, multiple thresholds can be used to determine the wear state of the cutting tool in stages. For example, when the current value of the driving current represented by the current information reaches the first threshold TH1, a prompt to confirm the cutting status can be issued; when the current value of the driving current represented by the current information reaches the second threshold TH2 (>TH1), a prompt to confirm the wear state of the cutting tool can be issued; when the current value of the driving current represented by the current information reaches the third threshold TH3 (>TH2), a prompt to perform dressing treatment can be issued; and when the current value of the driving current represented by the current information reaches the fourth threshold TH4 (>TH3), a prompt to replace the cutting tool can be issued.

[0098] Alternatively, the current value of the drive current when using a new blade that has not yet worn can be stored as an initial value. When the amount of change from the initial value of the drive current reaches a threshold, it is presumed that the wear state of the blade is at or near the limit, and a message is sent or the operation of the cutting device 100 is controlled.

[0099] Alternatively, the current value of the drive current when the trimming process is completed can be stored as an initial value during the trimming process. When the current value of the drive current when trimming the worn blade is close to the initial value, it is assumed that the trimming process is completed, and a message is sent or the operation of the cutting device 100 is controlled.

[0100] <Processing Anomaly Detection> Figure 15 This is a waveform showing the time-lapse of the drive current (q-axis current) during machining of an object. The machining operation involves creating a 1mm deep linear groove in a glass plate. The peaks of the waveform correspond to the state of cutting the object. The troughs correspond to the state of switching the machining line, which will not be discussed here.

[0101] exist Figure 15 In the waveform shown, the part where the driving current value drops sharply corresponds to the moment when a processing abnormality (defect) occurs in the workpiece. Figure 16 Is with Figure 15 The waveform shown corresponds to the image of the object being processed. Figure 16 This shows the state of damage along the groove formed on the workpiece.

[0102] As described above, as the cutting tool wears more, the drive current increases. When the tool wear reaches its limit, the cutting ability is insufficient, and the machining process becomes more of a fragmented one than a true cutting of the workpiece. In this machining mode, the quality of the workpiece is reduced. When the tool wear exceeds its limit, the workpiece experiences a machining abnormality (damage). When this abnormality (damage) occurs, the load on the spindle motor 30 is temporarily reduced, thus temporarily decreasing the drive current.

[0103] In summary, the current value of the drive current can be used to detect the occurrence of machining abnormalities in the workpiece. For example, it is possible to detect machining abnormalities based on changes in the drive current value.

[0104] In the case of detecting and handling processing abnormalities in monitoring unit 10, Figure 6A and Figure 6B The details of each process in the flowchart shown are as follows.

[0105] In step S1, CPU 101 acquires current information during the processing of the workpiece. Current information is continuously acquired during the processing of the workpiece.

[0106] In step S2, the CPU 101 determines whether the current value of the drive current is abnormal by comparing the change in the current value (peak portion) of the drive current represented by the current information obtained in step S1 with the most recent current value (peak portion) and a threshold. This determination is equivalent to determining whether a processing abnormality has occurred in the workpiece. For example, if the change in the current value (peak portion) of the drive current represented by the current information with the most recent current value (peak portion) is greater than the threshold, it is presumed that a processing abnormality has occurred, and the process proceeds to step S3.

[0107] In step S3, the CPU 101 issues a message indicating that a processing abnormality has occurred on the workpiece. For example, text or icons informing the workpiece of a processing abnormality can be displayed on the monitor 105. Alternatively, the abnormality can be indicated by a light illuminating the screen or by sound output from a speaker.

[0108] Additionally, in step S3, CPU 101 may also issue a control command to reduce the speed of spindle motor 30, limit the upper limit of the speed of spindle motor 30, or stop the rotation of spindle motor 30. Inverter 20, according to the control command, reduces, limits, or stops the rotation of spindle motor 30.

[0109] <Blade Damage Detection> Figure 17 This is a waveform showing the time-lapse of the drive current (q-axis current) during machining of an object. The machining operation involves creating a 1mm deep linear groove in a glass plate. The peaks of the waveform correspond to the state of cutting the object. The troughs correspond to the state of switching the machining line.

[0110] exist Figure 17 In the waveform shown, the part where the driving current value rises sharply corresponds to the moment when a part of the blade is damaged and missing. Figure 18 Is with Figure 17 The waveform shown corresponds to the image of the object being processed. Figure 18 This illustrates the state in which blade fragments are formed and held in the groove of the workpiece. When blade damage occurs, the cutting capability of the blade decreases instantaneously. Since the decrease in cutting capability is compensated by an increase in the torque of the spindle motor, the drive current increases instantaneously when blade damage occurs.

[0111] In summary, it can be said that the occurrence of blade damage can be detected using the current value of the driving current. For example, blade damage can be detected based on changes in the current value of the driving current. As a technique related to blade damage detection, an optical non-contact sensor called a BBD (Blade Breakage Detector) is known to be used. While BBD can detect damage of a certain scale, it is difficult to detect small-scale damage. On the other hand, blade damage detection based on the current value of the driving current can also detect small-scale damage that is difficult to detect with BBD.

[0112] In the case of blade damage detection and treatment in monitoring unit 10, Figure 6A and Figure 6B The details of each process in the flowchart shown are as follows.

[0113] In step S1, CPU 101 acquires current information during the processing of the workpiece. Current information is continuously acquired during the processing of the workpiece.

[0114] In step S2, the CPU 101 determines whether the drive current value is abnormal based on the deviation of the drive current value pattern from the standard pattern obtained in step S1. This determination is equivalent to determining whether the cutting tool has been damaged. The standard pattern can be the current value pattern of the drive current when machining the workpiece using an undamaged cutting tool. For example, if the deviation of the drive current value pattern from the standard pattern is greater than a threshold, it is presumed that cutting tool damage has occurred, and the process proceeds to step S3.

[0115] In step S3, CPU 101 issues a message indicating that the blade has been damaged. For example, text or an icon indicating blade damage can be displayed on display 105. Alternatively, an abnormality can be indicated by a light or sound output from a speaker.

[0116] Additionally, in step S3, CPU 101 can issue a control command to reduce the speed of spindle motor 30, a control command to limit the upper limit of the speed of spindle motor 30, or a control command to stop the rotation of spindle motor 30. Inverter 20, according to the control command, reduces, limits, or stops the rotation of spindle motor 30.

[0117] As described above, the cutting apparatus according to the disclosed embodiments includes: a spindle motor 30 that rotates the blade, an inverter 20 that drives the spindle motor 30 via vector control, and a monitoring unit 10. The monitoring unit 10 acquires current information indicating the magnitude of the drive current supplied from the inverter 20 to the spindle motor 30, and based on the current information, monitors at least one of the state of the cutting apparatus 100 and the processing state of the object processed by the cutting apparatus 100.

[0118] The monitoring of the cutting device 100 includes monitoring the status of the spindle motor, the installation status of the cutting blades, the water immersion status of the cutting blades, the wear status of the cutting blades, and the detection of blade damage. Monitoring the processing status of the workpiece includes detecting processing anomalies.

[0119] According to the embodiments of the disclosed technology, the cutting apparatus 100 can achieve status monitoring using the drive current supplied from the inverter 20 to the spindle motor 30.

Claims

1. A cutting device, comprising: The spindle motor rotates the blades; Inverter, driving the spindle motor via vector control; and Monitoring Department The monitoring unit acquires current information representing the magnitude of the drive current, which includes the q-axis current supplied from the inverter to the spindle motor. Based on the current information, it monitors at least one of the status of the cutting device and the processing status of the object being processed by the cutting device.

2. The cutting device according to claim 1, wherein, The monitoring unit sends out information based on the monitored status.

3. The cutting device according to claim 1, wherein, The monitoring unit issues instructions based on the monitored status, and these instructions are used to control the operation of the cutting device.

4. The cutting device according to any one of claims 1 to 3, wherein, The monitoring unit monitors the status of the spindle motor based on the current information when the object is not being processed.

5. The cutting device according to any one of claims 1 to 3, wherein, The monitoring unit monitors the installation status of the blade on the spindle motor based on the current information when the object is not being processed.

6. The cutting device according to any one of claims 1 to 3, wherein, The monitoring unit monitors the water immersion state of the blade caused by water sprayed onto the blade, based on the current information when the object is not being processed.

7. The cutting device according to any one of claims 1 to 3, wherein, The monitoring unit monitors the state of the blade based on the current information during the processing of the object.

8. The cutting device according to any one of claims 1 to 3, wherein, The monitoring unit detects the occurrence of processing abnormalities in the object based on the current information during processing.

9. The cutting device according to any one of claims 1 to 3, wherein, The monitoring unit detects damage to the blade based on the current information during the processing of the object.

10. A state monitoring method, wherein the state monitoring method acquires current information representing the magnitude of a drive current including the q-axis current supplied to the spindle motor when the spindle motor is driven to rotate the blade of the cutting device by vector control, and monitors the state of the cutting device or the processing state of an object processed by the cutting device based on the current information.

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