A workpiece grinding method and system

Abstract

Embodiments of the present disclosure generally relate to the field of computer numerical control (CNC) precision machining equipment, and in particular to a grinding method and system for circumferential chamfering of high-hardness, brittle materials. The grinding method is used for circumferential chamfering of a workpiece, the material of the workpiece being one or more of silicon carbide, sapphire and ceramic. The method comprises controlling the workpiece and the grinding wheel to rotate in opposite directions, and the rotational speed ratio of the workpiece and the grinding wheel being less than 1:1000, and the feed speed of the grinding wheel being greater than 0.02 mm / r. In this way, the chamfer or edge obtained is more uniform and smooth, has higher dimensional consistency, and allows a more aggressive feed speed, thereby improving machining efficiency.

Description

Technical Field

[0001] The embodiments disclosed herein generally relate to the field of computer numerical control (CNC) precision machining equipment, and specifically to a grinding method and system for chamfering high-hardness, brittle materials. Background Technology

[0002] In existing technologies, when a general-purpose CNC (Computer Numerical Control) grinding machine performs chamfering on a workpiece, the workpiece is fixed to the machining table by a fixture, and the grinding wheel travels along the workpiece edge in an arc trajectory via the CNC path. During the grinding process, the grinding wheel continuously cuts into and out of each grinding point on the workpiece edge, resulting in significant stress concentration. This is especially true at the edges of thin-walled or brittle materials (such as silicon carbide, sapphire, and ceramics), where chipping and breakage are prone to occur, affecting product yield and machining accuracy. Summary of the Invention

[0003] Embodiments of this disclosure provide a workpiece grinding method and system aimed at solving one or more of the above-mentioned problems and other potential problems.

[0004] According to a first aspect of this disclosure, a workpiece grinding method is provided for performing circumferential chamfering on a workpiece, the workpiece being made of one or more of silicon carbide, sapphire, and ceramic. The method includes controlling the workpiece and a grinding wheel to rotate in opposite directions, wherein the rotational speed ratio between the workpiece and the grinding wheel is less than 1:1000, and the feed rate of the grinding wheel is greater than 0.02 mm / r.

[0005] In some embodiments, the workpiece is a silicon carbide wafer, and the method further includes identifying the crystal orientation of the wafer edge to determine one or more highly fragile crystal orientation regions at the wafer edge. Furthermore, the method includes injecting pulsed microjets into the highly fragile crystal orientation regions of the wafer when they come into contact with a grinding wheel.

[0006] In some embodiments, the microjets include deionized water, nanodiamond particles, fluorinated surfactants, corrosion inhibitors, and dispersants.

[0007] In some embodiments, the single pulse volume of the microjets is 0.5-2 nL, the jet pressure is 3-8 MPa, and the jet direction of the microjets is upstream of the contact point between the highly fragile crystal orientation region of the wafer and the grinding wheel, inclined at 15-30°.

[0008] In some embodiments, the workpiece rotates at a speed of 200-400 rpm, the grinding wheel rotates at a speed of 12000-18000 rpm, and the relative linear velocity between the grinding wheel and the wafer is not less than 65 m / s.

[0009] In some embodiments, the microjet is triggered by a CNC system based on the real-time angular position of the wafer, and a pulse jet is performed on the highly vulnerable crystal orientation region once every time the wafer rotates.

[0010] In some embodiments, the method further includes detecting microcrack initiation characteristics of the wafer during the grinding process using an acoustic emission sensor. Additionally, the method includes increasing the jet pressure of the microjets during the next pulse jet in response to the detection of microcrack initiation characteristics.

[0011] In some embodiments, the acoustic emission sensor is a resonant piezoelectric sensor with a frequency response range of 100-400kHz and signal characteristics including a signal center frequency greater than 220kHz, a signal amplitude greater than 68dB, and a ratio of the signal rise angle to the signal average frequency less than 0.2.

[0012] According to a second aspect of this disclosure, a grinding system is provided, including a workpiece spindle configured to clamp a workpiece and provide feedback on its rotation angle; a grinding wheel spindle configured to mount a grinding wheel and rotate in the opposite direction to the workpiece spindle; a microjet module including a plurality of piezoelectrically driven micronozzles distributed circumferentially along the grinding wheel; a coolant supply unit connected to the microjet module and supplying a coolant containing nanodiamonds to the microjet module; a crystal orientation recognition unit for acquiring crystal orientation information of the wafer edge; and a central controller communicatively connected to the workpiece spindle, the grinding wheel spindle, the microjet module, and the crystal orientation recognition unit, and configured to perform the grinding method of the first aspect.

[0013] In some embodiments, the system further includes a resonant piezoelectric sensor mounted on the workpiece spindle, and the central controller is communicatively connected to the resonant piezoelectric sensor. Attached Figure Description

[0014] The above and other objects, features, and advantages of embodiments of the present disclosure will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated in the drawings by way of example and not limitation.

[0015] Figure 1 A schematic diagram illustrating an exemplary grinding process according to one or more embodiments of the present disclosure is shown.

[0016] Figure 2 A schematic diagram illustrating exemplary highly fragile crystal orientation regions according to one or more embodiments of the present disclosure is shown. Figure 3 A schematic diagram showing the jet direction of an exemplary microjets according to an embodiment of the present disclosure is provided.

[0017] In the various figures, the same or corresponding reference numerals indicate the same or corresponding parts. Detailed Implementation

[0018] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0019] The term "comprising" and its variations as used herein signify an open-ended inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". Terms such as "upper", "lower", "front", and "rear", indicating placement or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are used only for the purpose of describing the principles of this disclosure, and are not intended to indicate or imply that the elements referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as limiting this disclosure.

[0020] As mentioned earlier, general-purpose CNC (Computer Numerical Control) grinding machines are used for precision edge grinding and chamfering of high-hardness, brittle materials (such as SiC, sapphire, and ceramics), especially for large-diameter, ultra-thin wafers or substrates widely used in the semiconductor, optics, and microelectronics fields. During circumferential chamfering, the workpiece is fixed to the machining table by a fixture, and the grinding wheel follows a CNC path along an arc trajectory around the workpiece edge. During this grinding process, the grinding wheel continuously enters and exits each grinding point on the workpiece edge, resulting in significant stress concentration. This easily leads to machining defects such as edge chipping and breakage at the workpiece edge, affecting product yield and machining accuracy. In existing technologies, to avoid edge chipping, very conservative feed rates are typically used, such as 0.01 mm / r, which prolongs the machining time for a single workpiece.

[0021] To address this, according to embodiments of this disclosure, a workpiece grinding method is provided for chamfering a workpiece made of one or more of silicon carbide, sapphire, and ceramic. The method includes controlling the workpiece and grinding wheel to rotate in opposite directions, with the workpiece-to-grind wheel speed ratio less than 1:1000, and the grinding wheel feed rate greater than 0.02 mm / r. In this manner, the workpiece's rotation causes the cutting force application point to continuously change, avoiding edge chipping caused by continuous force at a fixed point. This results in a more uniform and smooth chamfer or edge with higher dimensional consistency, while allowing for a more aggressive feed rate, thereby improving processing efficiency. The working principle of a workpiece grinding method according to embodiments of this disclosure will be described in detail below with reference to the accompanying drawings.

[0022] The following explanation will focus on the circumferential chamfering process of a silicon carbide wafer with a diameter of 200 mm and a thickness of 0.5 mm. Figure 1 A schematic diagram illustrating an exemplary grinding process according to one or more embodiments of the present disclosure is shown, such as... Figure 1 As shown, in one or more embodiments of this disclosure, wafer processing can be performed on a CNC machine tool. A silicon carbide wafer 100 can be fixed to a workpiece spindle 101 using a vacuum chuck or other fixture. A grinding wheel 200 is mounted on a grinding wheel spindle 201. The CNC control system controls the wafer (i.e., the workpiece) and the grinding wheel to rotate in opposite directions, with the speed ratio between the wafer and the grinding wheel being less than 1:1000. For example, the grinding wheel spindle can be set to rotate clockwise at 13000 rpm, and the workpiece spindle can be set to rotate counterclockwise at 10 rpm. When the machine tool is started, driven by the grinding wheel spindle and the workpiece spindle, the grinding wheel and the wafer begin to rotate in opposite directions according to the set parameters. The relative linear velocity at the contact point P is the sum of the linear velocity of the grinding wheel at the contact point |Vs| and the velocity of the wafer at the contact point |Vw|. This motion method allows the chipping force to be more evenly distributed across the entire circumference of the wafer edge, avoiding stress concentration. Simultaneously, due to the wafer's own rotation, the point of application of the chipping force constantly changes, preventing the wafer from being continuously stressed at a fixed point and reducing edge chipping. In one or more embodiments of this disclosure, the grinding wheel can also be fed at a more aggressive speed (e.g., 0.05 mm / r) greater than 0.02 mm / r by a CNC control system. This can improve processing efficiency while achieving more uniform, smoother chamfers or edges with higher dimensional consistency.

[0023] Silicon carbide wafers are single-crystal materials. In single-crystal materials, the atomic arrangement varies significantly across different crystal orientations, leading to a high orientation-dependent mechanical response (such as fracture susceptibility, cleavage, and slip system density). This inhomogeneity causes certain crystal orientations to undergo brittle fracture under mechanical stress, resulting in edge chipping. For example, silicon carbide wafers... <0001> This crystal orientation exhibits low slip system density and high cleavage tendency, making it the orientation with the highest risk of edge chipping in semiconductor wafer processing, with an average edge chipping size that can reach [missing information]. <100> 5-8 times the direction. In one or more embodiments of this disclosure, to avoid the highly fragile crystal orientation of the wafer (e.g., <0001> To address edge chipping issues (in the direction of grinding), a micro-piezoelectric driven nozzle array can be integrated into the CNC machine tool. For example, the micro-piezoelectric driven nozzle array can be integrated into the grinding wheel along its circumference or positioned independently of the grinding wheel towards the contact area between the grinding wheel and the workpiece. Before grinding, the crystal orientation of the wafer edge is identified to determine one or more highly vulnerable crystal orientation regions on the edge of the wafer to be processed. Based on the identified highly vulnerable crystal orientation regions, during grinding, when the highly vulnerable crystal orientation region of the wafer contacts the grinding wheel (i.e., the contact point P is located in the highly vulnerable crystal orientation region of the wafer), the micro-piezoelectric driven nozzle array is triggered to inject pulsed microjets into the highly vulnerable crystal orientation region. When the grinding wheel and workpiece rotate in the same direction or one of them is stationary, droplets during microjet injection tend to accumulate locally in the contact area between the grinding wheel and the workpiece, causing watermarks, uneven cooling, and slow cooling rates. In one or more embodiments of this disclosure, a strong shear flow field can be formed in the grinding gap between the grinding wheel and the wafer through the high-speed counter-rotation of the grinding wheel and the wafer. When the injected microjets are stretched into a thin film by the high-speed strong shear flow field, they can quickly and uniformly cover the contact area between the wafer and the grinding wheel, forming transient enhanced cooling and micro-lubrication, which can reduce the friction coefficient between the wafer and the grinding wheel (more than 30%), thereby suppressing the initiation of microcracks in the wafer.

[0024] In one or more embodiments of this disclosure, the highly fragile crystal orientation region may be a wafer detected by polarization imaging or XRD techniques. <0001> The angular region corresponding to the orientation. In one or more embodiments of this disclosure, the highly vulnerable crystal orientation region may also be the angular region corresponding to the region with the fastest temperature rise and the greatest thermal stress during wafer grinding, as predicted by thermal simulation technology. Figure 2 A schematic diagram of a highly fragile crystal orientation region 110 according to one or more embodiments of the present disclosure is shown. Figure 2As shown, in one or more embodiments of this disclosure, the wafer 100 can be clamped and fixed on the workpiece spindle and then identified by polarization imaging. <0001> The highly fragile crystal orientation region 110 is located within the rotation plane XOY of the workpiece spindle. Taking the current rotation angle of the workpiece spindle motor as the starting angle 0°, when the workpiece spindle motor rotates clockwise to the position corresponding to angle θ1, point Q1 on the wafer edge rotates to position P in contact with the grinding wheel 200, and the highly fragile crystal orientation region 110 begins to contact the grinding wheel. The workpiece spindle motor continues to rotate clockwise until it reaches the position corresponding to angle θ2, at which point Q2 on the wafer edge rotates to position P in contact with the grinding wheel 200, and the highly fragile crystal orientation region 110 is about to leave contact with the grinding wheel. In one or more embodiments of this disclosure, the angle region corresponding to the rotation angle of the workpiece spindle motor from θ1 to θ2 can be recorded as the angle region corresponding to the highly fragile crystal orientation region. During subsequent grinding, the angle position of the workpiece spindle motor can be monitored in real time by the CNC control system. When the workpiece spindle motor rotates to the corresponding angle region, a micro-piezoelectric driven nozzle array is triggered to spray pulsed microjets towards the highly fragile crystal orientation region. In this way, the highly vulnerable crystal orientation region of the wafer can be bound to the rotation angle of the drive motor of the workpiece shaft, which facilitates the control of the micro piezoelectric drive nozzle array.

[0025] The microjets can be high-pressure coolants comprising deionized water and nanodiamond suspensions. In one or more embodiments of this disclosure, the microjets may comprise 94% deionized water by mass, 3% nanodiamond particles by mass, 0.5% fluorinated surfactant by mass, 0.1% corrosion inhibitor by mass, and 2.4% dispersant by mass. Deionized water has a high specific heat capacity, making it suitable as the primary cooling medium. Nanodiamond particles (20-50 nm in diameter) can embed into subsurface micropores under high pressure, filling microcracks generated during grinding and improving the surface integrity and edge strength of the wafer. Fluorinated surfactants, such as Zonyl FSN, are used to reduce the surface tension of the coolant (e.g., below 25 mN / m), facilitating its spread in strong shear flow fields. Corrosion inhibitors, such as benzotriazole, prevent oxidation of the wafer (i.e., silicon carbide). Dispersants, such as sodium citrate, prevent the agglomeration of diamond nanoparticles in the coolant, ensuring their uniform distribution within the coolant.

[0026] In one or more embodiments of this disclosure, the single pulse volume of the microjets is 0.5-2 nL, corresponding to an injection time of 0.2-0.8 ms. The injection pressure is 3-8 MPa, resulting in an instantaneous flow velocity of 10-30 m / s. Furthermore, the injection direction of the microjets is upstream of the contact point between the highly fragile crystal orientation region of the wafer and the grinding wheel, at an angle of 15°-30° to the normal. Here, "upstream direction" refers to the direction opposite to the direction of the relative motion V at the contact point P between the wafer and the grinding wheel. If the relative motion V sweeps across the contact area from top to bottom, then the upstream direction is above, and the microjets should be injected from the upstream side to be captured by the flow field and carried into the grinding zone. Figure 3 A schematic diagram of the jet direction of an exemplary microjets according to an embodiment of the present disclosure is shown. Figure 3 As shown, in one or more embodiments of this disclosure, the wafer 100 rotates counterclockwise with the workpiece spindle, and the grinding wheel 200 rotates clockwise with the grinding wheel spindle. The direction of the relative motion V at the contact point P between the wafer and the grinding wheel is vertically downward, and the upstream direction is opposite to this direction, i.e., upward. Therefore, the direction of the microjets 303 is tilted at an angle a (20°) relative to the normal direction 302 at position P and faces upward. In this way, the microjets can be pulled towards the center of the contact area between the grinding wheel and the wafer by the shear force flow field at that position after injection. In one or more embodiments of this disclosure, the micro-piezoelectric driven nozzle array can be mounted on a bracket facing the contact area between the grinding wheel and the wafer, and at a distance of 0.5-1.0 mm from the contact area, to ensure that the microjets can be pre-stretched by the shear flow field generated by the high-speed rotation between the grinding wheel and the wafer before entering the grinding zone.

[0027] In one or more embodiments of this disclosure, the microjets can be ejected through an array of miniature piezoelectric-driven nozzles with an aperture of 50-100 μm and a response time of less than or equal to 1 ms. In one or more embodiments of this disclosure, the coolant can be provided by a high-pressure micropump with an adjustable pressure of 0-10 MPa and a filtration accuracy of 0.1 μm. In one or more embodiments of this disclosure, the wafer rotation speed can be 200-400 rpm to ensure sufficient phase resolution for highly fragile crystalline phase regions. The grinding wheel rotation speed can be 12000-18000 rpm, a range that balances efficiency with the risk of burn-in. The relative linear velocity between the grinding wheel and the wafer is greater than or equal to 65 m / s to ensure the formation of a shear flow field sufficient for stretching microjets to form a film.

[0028] In one or more embodiments of this disclosure, the microjets can be triggered by a CNC system based on the real-time angular position of the wafer, with each highly fragile crystalline region receiving only one pulse jet per revolution of the wafer. In one or more embodiments of this disclosure, the real-time angular position of the wafer can be determined by detecting the rotation angle of the workpiece spindle motor. In one or more embodiments of this disclosure, the microjets can be triggered as soon as the highly fragile crystalline region enters the contact area between the grinding wheel and the workpiece. In one or more embodiments of this disclosure, the duration of each microjet jet can also be determined based on the width of the highly fragile crystalline region. For example, the greater the width of the highly fragile crystalline region at the wafer edge, the longer the duration of the microjets' jetting window, allowing the amount of cooling water carried by the microjets to precisely match the size of the highly fragile crystalline region, reducing coolant consumption.

[0029] In one or more embodiments of this disclosure, the microcrack initiation characteristics of the wafer during the grinding process can also be detected by an acoustic emission sensor. If microcrack initiation characteristics are detected, the injection pressure of the microjets pulsed into the highly fragile crystal orientation region is increased. After acoustic emission absorption, the injection parameters can be adjusted in real time, forming a "sensing-response" closed loop. In one or more embodiments of this disclosure, the acoustic emission sensor can be installed on the bearing seat of the workpiece spindle, the grinding wheel spindle seat, or the housing, at a position less than or equal to 100 mm from the contact point between the wafer and the grinding wheel. In one or more embodiments of this disclosure, the acoustic emission (AE) sensor can be a resonant piezoelectric AE sensor, a broadband MEMS AE sensor, or a fiber optic acoustic emission sensor. Among them, the resonant piezoelectric AE sensor has a high signal-to-noise ratio and strong electromagnetic interference resistance, making it suitable for industrial grinding machines. When a microcrack occurs, a sudden energy release occurs within the material, thereby generating a specific AE signal. In one or more embodiments of this disclosure, the acoustic emission sensor can be a resonant piezoelectric sensor with a frequency response range of 100-400 kHz. Microcrack initiation characteristics include a signal center frequency greater than 220 kHz, a signal amplitude greater than 68 dB, and a ratio of the signal rise angle to the average signal frequency less than 0.2. Here, the rise angle RA is the ratio of the rise time to the peak amplitude of the acoustic emission signal, in microseconds (μs). The average signal frequency AF is the average frequency calculated from the number of zero-crossings and the duration of the signal, in kilohertz (kHz). The microcrack initiation characteristic RA / AF ratio is less than 0.2, meaning RA is less than 50 microseconds and AF is greater than 250 kilohertz. In one or more embodiments of this disclosure, in the next cycle after detecting a microcrack initiation signal, the injection pressure of the microjets in the same highly fragile crystal orientation region can be increased by 1.0 MPa from the reference pressure. Subsequently, monitoring of the microcrack initiation signal continues: in the next cycle after two consecutive cycles without detecting a microcrack initiation signal, the injection pressure of the microjets in the same highly fragile crystal orientation region is adjusted back to the reference pressure. If microcrack initiation signals are detected for three consecutive cycles, an alarm can be triggered and the machine can be stopped.

[0030] According to embodiments of this disclosure, a workpiece grinding system is also provided, including a workpiece spindle configured to clamp a workpiece and provide feedback on its rotation angle. A grinding wheel spindle configured to mount a grinding wheel and rotate in the opposite direction to the workpiece spindle. A microjet module including a plurality of piezoelectrically driven micronozzles distributed circumferentially along the grinding wheel. A coolant supply unit connected to the microjet module and providing coolant containing nanodiamonds to the microjet module. A crystal orientation recognition unit for acquiring crystal orientation information of the wafer edge. The system further includes a central controller communicatively connected to the workpiece spindle, the grinding wheel spindle, the microjet module, and the crystal orientation recognition unit, and configured to perform the grinding method described in any one of the above embodiments. In one or more embodiments of this disclosure, the system may further include a resonant piezoelectric sensor mounted on the workpiece spindle, and the central controller communicatively connected to the resonant piezoelectric sensor, thereby enabling the central controller to dynamically trigger the opening and closing of the piezoelectrically driven micronozzles according to the rotation angle of the workpiece spindle (i.e., the rotation angle of the workpiece).

[0031] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A workpiece grinding method for performing circumferential chamfering on a workpiece, wherein the workpiece is made of one or more of silicon carbide, sapphire, and ceramic, characterized in that... include: The workpiece and the grinding wheel are controlled to rotate in opposite directions, and the speed ratio between the workpiece and the grinding wheel is less than 1:1000, while the feed speed of the grinding wheel is greater than 0.02 mm / r.

2. The method according to claim 1, characterized in that, The workpiece is a silicon carbide wafer, and the method further includes: Identify the crystal orientation of the wafer edge to determine one or more highly fragile crystal orientation regions at the wafer edge; and When the highly fragile crystal orientation region of the wafer comes into contact with the grinding wheel, a pulsed microjet is injected into the highly fragile crystal orientation region.

3. The method according to claim 2, characterized in that, The microjets include deionized water, nanodiamond particles, fluorinated surfactants, corrosion inhibitors, and dispersants.

4. The method according to claim 3, characterized in that, The single pulse volume of the microjets is 0.5-2 nL, the injection pressure is 3-8 MPa, and the injection direction of the microjets is upstream of the contact point between the highly fragile crystal orientation region of the wafer and the grinding wheel, inclined at 15°-30°.

5. The method according to any one of claims 2-4, characterized in that, The workpiece rotates at a speed of 200-400 rpm, the grinding wheel rotates at a speed of 12000-18000 rpm, and the relative linear velocity between the grinding wheel and the wafer is not less than 65 m / s.

6. The method according to any one of claims 2-4, characterized in that, The microjet is triggered by the CNC system according to the real-time angular position of the wafer, and a pulse jet is executed on the highly vulnerable crystal orientation region once for each revolution of the wafer.

7. The method according to claim 6, characterized in that, Also includes: The microcrack initiation characteristics of the wafer during the grinding process were detected using an acoustic emission sensor. as well as In response to the detection of the microcrack initiation characteristics, the injection pressure of the microjet is increased when the next pulse injection is performed.

8. The method according to claim 7, characterized in that, The acoustic emission sensor is a resonant piezoelectric sensor with a frequency response range of 100-400kHz. The signal characteristics include a signal center frequency greater than 220kHz, a signal amplitude greater than 68dB, and a ratio of the signal rise angle to the signal average frequency less than 0.

2.

9. A grinding system, characterized in that, include: The workpiece spindle is configured to clamp the workpiece and provide feedback on its rotation angle. A grinding wheel spindle is configured to mount the grinding wheel and rotate in the opposite direction to the workpiece spindle. The microjet module includes a plurality of piezoelectrically driven micronozzles distributed circumferentially along the grinding wheel; A coolant supply unit is connected to the microjet module and provides the microjet module with coolant containing nanodiamonds; A crystal orientation identification unit is used to acquire crystal orientation information at the edge of the wafer; as well as A central controller is communicatively connected to the workpiece spindle, the grinding wheel spindle, the microjet module, and the crystal orientation identification unit, and is configured to perform the grinding method according to any one of claims 1-8.

10. The system according to claim 9, characterized in that, It also includes a resonant piezoelectric sensor mounted on the workpiece spindle, and the central controller is communicatively connected to the resonant piezoelectric sensor.

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