A dry-wet dual working condition integrated flow type grinding and polishing machine and a control method thereof

Abstract

The present application relates to precision machining equipment technical field, specifically to a kind of dry and wet double working condition integrated flow type lapping and polishing machine and control method thereof, comprising: a lapping chuck, the lapping chuck is formed by the lamination connection of upper work disc and lower base disc;The lower base disc is processed with mutually independent liquid cooling flow channel and heating module embedding cavity inside, the liquid cooling flow channel is used to flow cooling medium, PTC heating element is arranged in the heating module embedding cavity;The lower base disc is also provided with a blind hole mounting cavity, a high-temperature-resistant waterproof acoustic emission sensor is embedded and potted in the blind hole mounting cavity, the vertical distance between the bottom of the blind hole mounting cavity and the upper surface of the upper work disc is 2mm to 5mm;The present application embeds acoustic emission sensor in lapping chuck inside and sets annular air vibration isolation groove, to realize three functions that existing technology cannot achieve simultaneously with single sensor.

Description

Technical Field

[0001] This invention relates to the field of precision machining equipment technology, specifically to an integrated dry and wet dual-condition flow grinding and polishing machine and its control method. Background Technology

[0002] Grinding and polishing are crucial processes in the machining of hard and brittle materials such as optical glass, sapphire, silicon carbide, and engineering ceramics. Depending on the machining stage and material properties, grinding and polishing are generally divided into dry grinding and wet grinding. Dry grinding is suitable for rough grinding or machining water-sensitive materials, offering high material removal rates, but it easily generates a large amount of dust and can cause thermal damage to the workpiece surface. Wet grinding is suitable for fine grinding and polishing, utilizing grinding fluid for cooling and lubrication, which reduces the risk of thermal damage; however, the grinding fluid requires precise temperature and viscosity control to ensure consistent machining quality.

[0003] To achieve both dry and wet grinding functions on a single machine, the industry has proposed a dual-mode dry and wet grinding and polishing machine. However, existing such equipment faces two technical challenges in practical applications that are both "thin and long" and permeate the entire process of structural design and control strategy.

[0004] First, there is the issue of lag and imperceptibility in temperature field control. In dry grinding, existing equipment relies on resistance temperature detectors (RTDs) or thermocouples to monitor the grinding disc temperature. However, due to thermal resistance and capacity issues in heat conduction from the grinding interface to the sensor mounting point, the temperature sensor response exhibits significant lag. When the temperature sensor detects an over-temperature alarm, the workpiece surface may have already experienced a peak temperature exceeding the material's phase transition point hundreds of milliseconds prior, leading to subsurface microcracks and thermal damage invisible to the naked eye. In wet grinding, the processing quality is determined by the true viscosity of the grinding fluid in the micrometer-level gap between the grinding disc and the workpiece. This region has an extremely high shear rate, concentrated heat generation, and a viscosity far lower than that at the center of the pipeline. Existing in-line viscometers can only measure the viscosity at the center of the pipeline, failing to perceive the true rheological state of this microscopic region, resulting in inaccurate temperature control.

[0005] Secondly, there are issues with the reliability and verifiability of pipeline cleaning during the switch between wet and dry grinding conditions. After wet grinding, a large amount of abrasive slurry adheres to the inner wall of the grinding fluid supply pipeline. When switching to dry grinding, if the pipeline is not thoroughly cleaned, the residual slurry will harden and detach, scratching the workpiece surface in the next processing round and causing the entire batch of workpieces to be scrapped. Existing cleaning methods are mostly manual rinsing or timed air blowing, and the cleaning effect cannot be quantified. Workers are often hesitant to frequently switch between operating conditions during the processing due to fear of cross-contamination, rendering the equipment's advertised "dual wet and dry operating condition" function useless in actual use.

[0006] In the field of grinding and polishing technology, acoustic emission (AE) sensors have been used to monitor the processing status. For example, Chinese invention patent application publication CN116847949A discloses a grinding device that uses an AE sensor to detect the contact state between the grinding material and the workpiece. The signal output from the AE sensor is combined with the motor current signal to control the cutting speed of the grinding material in two stages, thereby shortening processing time while avoiding grinding burns. In this solution, the core function of the AE sensor is to perform a binary judgment of "contact / non-contact," without addressing closed-loop control of the temperature field, switching between dry and wet conditions, or pipeline cleaning.

[0007] For example, Chinese invention patent application publication CN119317512A discloses a chemical mechanical polishing device that uses an in-situ acoustic monitoring system to receive acoustic signals from a regulator disk. Through frequency domain analysis and other methods, it determines the wear state, installation status, or whether the downward pressure on the regulator disk is abnormal, thus achieving maintenance and diagnosis of this consumable material. In this scheme, the acoustic sensor monitors the regulator disk itself, which is used to trim the polishing pad, and its purpose is to determine when the regulator disk needs to be replaced or reinstalled. It does not use the acoustic signals for closed-loop control of process parameters in the grinding and polishing process, nor does it address the switching between dry and wet operating conditions or pipeline cleaning acceptance.

[0008] In summary, while both of the aforementioned existing technologies involve the application of acoustic emission or acoustic sensors in grinding / polishing equipment, their sensor functions are respectively "contact detection for motion control" and "consumable condition monitoring for maintenance and diagnosis." This aligns with two core challenges in the field: overcoming subsurface thermal damage to the workpiece caused by temperature sensor response lag, accurately sensing the true viscosity of the grinding fluid at the grinding interface without relying on contact viscometers, and achieving reliable digital determination of pipeline cleanliness during operating condition switching. Therefore, systematically solving these challenges and transforming dry / wet dual-condition switching from a manual, high-risk special operation into an automated, reliable routine function remains a technological bottleneck that has yet to be overcome in this field. Summary of the Invention

[0009] This invention aims to solve the aforementioned technical problems by providing an integrated dry and wet dual-condition flow-type grinding and polishing machine and its control method. By embedding an acoustic emission sensor inside the grinding disc and setting an annular air vibration isolation groove to attenuate fluid background noise, this invention enables the simultaneous use of a single sensor to perform thermal damage early warning in dry grinding conditions, interfacial viscosity calculation in wet grinding conditions, and reliable acceptance of pipeline cleanliness during condition switching. This transforms the dry-wet dual-condition switching from a manual, high-risk special operation into an automated, reliable, and routine function.

[0010] To achieve the above objectives, the present invention adopts the following technical solution.

[0011] A dry and wet dual-condition integrated flow grinding and polishing machine includes: A grinding disc, wherein the grinding disc is composed of an upper working disc and a lower base disc stacked and connected together; The lower base plate is internally machined with independent liquid cooling channels and heating module embedding cavities. The liquid cooling channels are used to circulate cooling medium, and the heating module embedding cavity is equipped with a PTC heating element. The lower base plate also has a blind hole mounting cavity, in which a high-temperature resistant and waterproof acoustic emission sensor is embedded and sealed. The vertical distance between the bottom of the blind hole mounting cavity and the upper surface of the upper working plate is 2mm to 5mm. An annular air vibration isolation groove is machined between the liquid cooling channel and the blind hole mounting cavity. The annular air vibration isolation groove is arranged around the blind hole mounting cavity to attenuate the interference of background noise generated by the fluid flow in the liquid cooling channel on the acoustic emission sensor. A controller is electrically connected to the acoustic emission sensor, the cooling medium supply device of the liquid-cooled channel, and the PTC heating element. The controller is configured to: predict the risk of thermal damage during dry grinding based on the changing trend of the high-frequency event count rate in the frequency domain characteristic parameters of the acoustic emission signal collected by the acoustic emission sensor, and initiate cooling action in advance; and calculate the viscosity change trend of the grinding fluid at the grinding interface based on the center frequency offset or power spectral density change in the frequency domain characteristic parameters of the acoustic emission signal, and adjust the temperature and / or flow rate of the cooling medium in the liquid-cooled channel accordingly.

[0012] In the aforementioned structural design, a significant synergistic effect is achieved between the "embedded acoustic emission sensor" and the "annular air vibration isolation groove." The acoustic emission sensor, closely attached to the grinding interface, enables high-sensitivity in-situ acoustic signal acquisition. Meanwhile, the annular air vibration isolation groove utilizes the significant acoustic impedance difference between air and metal to strongly reflect and attenuate background noise generated by fluid flow within the liquid-cooled channel at the groove interface, preventing it from effectively transmitting to the acoustic emission sensor. This combination overcomes the common technical bias in the field that "acoustic emission sensors cannot function effectively in environments with fluid flow," allowing the sensor to clearly distinguish between the acoustic signals of the grinding particles and the characteristic signals of the grinding fluid even under wet grinding conditions. This unlocks two core functions that traditional sensor solutions cannot achieve: "wet grinding interface viscosity sensing" and "pipeline cleaning acceptance." Furthermore, under the unified control of the controller, the liquid-cooled channel and PTC heating element achieve rapid preheating of the grinding disc, steady-state temperature control, thermal shock buffering during wet-dry transitions, and anti-condensation protection after wet grinding, covering the precise temperature control requirements throughout the entire equipment lifecycle.

[0013] Furthermore, the dry-wet dual-condition integrated flow grinding and polishing machine also includes a dry-wet switching pipeline system, which includes: Grinding fluid supply main pipeline; A high-pressure pulsed airflow branch connected in parallel with the main supply line for the polishing fluid; A venturi nozzle is installed at the end of the main grinding fluid supply line, near the inlet of the grinding disc; Upon receiving a working condition switching command, the controller controls the high-pressure pulse airflow branch to supply pulse airflow to the grinding fluid supply main pipeline. The Venturi nozzle generates local negative pressure when the airflow passes through, so as to entrain and peel off residual abrasive particles adhering to the inner wall of the pipeline.

[0014] The aforementioned pipeline system uses a Venturi nozzle to simultaneously convert a pulsed airflow into three cleaning forces: the "pull-out force" (suction) generated by negative pressure, the repeated "pulling force" (tearing) generated by the pulse, and the "pushing force" (blowing) of the high-speed airflow itself. This achieves a highly efficient self-cleaning of the pipeline by combining the three effects of "suction, tearing, and blowing," solving the problem that traditional direct airflow cannot remove mud adhering to dead corners of the pipeline.

[0015] Furthermore, during the purging process of the high-pressure pulsed airflow branch, the controller acquires the acoustic emission signal collected by the acoustic emission sensor; when the peak count of acoustic emission events detected within a preset time window is lower than a preset cleaning threshold, and the proportion of high-frequency energy in the frequency domain characteristic parameters of the acoustic emission signal is lower than a preset cleaning energy threshold, it is determined that the residual abrasive particles in the pipeline have been removed, and a safety interlock signal that allows the switching of operating conditions is output.

[0016] The above solution organically couples Venturi pulse cleaning (execution end) with acoustic emission cleaning acceptance (sensing end), forming a complete "sensing-execution-verification" closed loop. Venturi pulses provide efficient physical cleaning capabilities, while acoustic emission sensors provide quantitative cleaning judgment capabilities. When residual abrasive particles are still blown out from the inner wall of the pipeline, the impact of these particles on the pipe wall and the surface of the grinding disc generates measurable high-frequency acoustic emission signals; these signals disappear when cleaning is completely complete. Based on this, the controller outputs a safety interlock signal, achieving for the first time digital judgment of cleanliness and safe switching assurance in a dry-wet dual-condition grinding and polishing equipment. This transforms the condition switching from "manual cleaning + manual judgment" to "automatic cleaning + automatic acceptance," truly achieving unmanned and reliable dry-wet alternating operation. This application of acoustic emission sensors to "accept cleaning effects" is a unique approach that crosses the traditional field of "process monitoring" to the field of "equipment self-cleaning acceptance," producing unexpected technical effects.

[0017] Furthermore, the cross-sectional shape of the annular air vibration isolation groove is rectangular, trapezoidal, or V-shaped, and the groove depth is 30% to 80% of the depth of the blind hole mounting cavity.

[0018] Furthermore, the space between the inner wall of the blind hole mounting cavity and the acoustic emission sensor is filled with thermally conductive potting compound, so that the acoustic emission sensor can achieve acoustic and thermal coupling with the lower surface of the upper working plate through the potting compound.

[0019] Furthermore, at least one backup temperature sensor is also embedded in the lower base plate. Under dry grinding conditions, when the high-frequency event count rate detected by the acoustic emission sensor increases by more than 200% within 1 second, but the real-time temperature detected by the backup temperature sensor has not yet reached the preset temperature warning line, the controller will start the semiconductor cooling chip and / or fan in advance to force cooling of the grinding plate.

[0020] The aforementioned solution utilizes the high sensitivity of acoustic emission sensors to precursor signals of microcrack propagation in materials, triggering cooling actions before a backup temperature sensor (such as a resistance temperature detector) detects an anomaly. This reduces the response time of temperature control from the second-level lag of traditional resistance temperature detectors to the millisecond-level real-time response of acoustic emission, achieving a leap from "passive feedback cooling" to "predictive thermal protection." This approach of using acoustic emission sensors for "thermodynamic state prediction" breaks through the conventional application scope of acoustic emission sensors in this field, which is limited to "flaw detection" or "contact detection," producing unexpected technical effects.

[0021] A control method for a wet / dry dual-condition integrated flow grinding and polishing machine, applied to any of the above-mentioned wet / dry dual-condition integrated flow grinding and polishing machines, includes the following steps: Step S1: Acquire the real-time acoustic emission signal collected by the acoustic emission sensor; Step S2: Extract time-domain features and frequency-domain features from the real-time acoustic emission signal to obtain time-domain feature parameters and frequency-domain feature parameters; Step S3: Determine the current working mode of the grinding and polishing machine based on the time-domain feature parameters. The working mode includes dry grinding mode and wet grinding mode. Step S4: When it is determined to be a dry grinding condition, execute the dry grinding temperature control subroutine: monitor the acoustic emission event count rate in the frequency range of 50kHz to 200kHz. When the growth rate of the acoustic emission event count rate in this range exceeds a preset multiple in the first preset time window, it is determined that there is a risk of dry grinding thermal damage, and the cooling action associated with the liquid cooling channel is started in advance. Step S5: When the condition is determined to be wet grinding, execute the wet grinding temperature control subroutine: based on the center frequency offset or power spectral density change in the frequency domain characteristic parameters, calculate the viscosity change trend of the grinding fluid at the grinding interface, and adjust the temperature and / or flow rate of the cooling medium passing through the liquid cooling channel in reverse according to the viscosity change trend.

[0022] The aforementioned control method enables the use of a single acoustic emission sensor and a single set of signal acquisition hardware to monitor two completely different physical quantities with entirely different physical mechanisms under two distinct working conditions: dry grinding and wet grinding. In dry grinding, it monitors the precursors of solid microcrack propagation, falling under the category of solid fracture mechanics; in wet grinding, it monitors changes in the acoustic characteristics of the grinding fluid flow and solid-state coupling, falling under the category of hydrodynamic noise, and forms closed-loop control for each. This "one sensor, two perceptions" capability significantly simplifies the equipment structure, reduces hardware costs, and provides an integration and reliability unmatched by traditional multi-sensor solutions. In particular, step S5, which uses the center frequency shift or power spectral density change in the frequency domain characteristics of the acoustic emission signal to infer the viscosity of the grinding fluid at the grinding interface, achieves non-contact in-situ sensing of fluid rheological properties within a micrometer-level gap without relying on any contact viscometer. This breaks through the conventional technical path in this field where viscosity measurement must rely on a viscometer, producing unexpected technical effects.

[0023] Furthermore, the specific method for determining the working condition mode in step S3 is as follows: when the root mean square value of the signal in the time domain feature parameter remains stable and the proportion of high-frequency energy in the frequency domain feature parameter is lower than the first set threshold, it is determined to be a wet grinding condition; when the fluctuation amplitude of the root mean square value of the signal in the time domain feature parameter exceeds the second set threshold and the count rate of sudden high-frequency events in the frequency domain feature parameter exceeds the third set threshold, it is determined to be a dry grinding condition.

[0024] Furthermore, it also includes step S6: self-cleaning judgment and control of operating condition switching, specifically including: receiving an operating condition switching command; after cutting off the supply of polishing fluid, starting a high-pressure pulse airflow branch connected in parallel with the main supply pipeline of polishing fluid, and performing pulse purging on the pipeline through a Venturi nozzle; acquiring the acoustic emission signal collected by the acoustic emission sensor during the purging process; extracting the attenuated burst signal characteristics of the acoustic emission signal; when the peak count of the detected acoustic emission event is lower than the preset cleaning threshold and the proportion of high-frequency energy in the frequency domain characteristic parameters is lower than the preset cleaning energy threshold within the second preset time window, it is determined that the residual abrasive particles in the pipeline have been removed, and a safety interlock signal allowing the operating condition switching is output.

[0025] Further, step S5, "calculating the viscosity change trend of the polishing fluid at the polishing interface based on the center frequency offset or power spectral density change in the frequency domain characteristic parameters," specifically includes: establishing a calibration mathematical model of the coupling relationship between the center frequency of the acoustic emission signal and the viscosity-temperature of the polishing fluid and storing it in the controller; monitoring the center frequency of the acoustic emission signal in real time; when the amplitude of the center frequency shifting to a lower frequency direction exceeds a preset frequency offset threshold, it is determined that the viscosity of the polishing fluid at the polishing interface has decreased to a preset lower limit threshold due to the increase in temperature; the reverse adjustment specifically involves: increasing the flow rate of the cooling medium in the liquid cooling channel or reducing its temperature to suppress the temperature rise of the polishing fluid body until the center frequency recovers to the preset target frequency range.

[0026] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves three functions simultaneously, unattainable by existing technologies, through embedding an acoustic emission sensor within the grinding disc and setting up an annular air vibration isolation groove: First, by utilizing the abrupt change trend of the high-frequency event count rate of acoustic emission, cooling is triggered in advance before the temperature sensor alarms, achieving a leap from "feedback cooling" to "predictive thermal protection"; Second, by using the frequency domain characteristic shift of the acoustic emission signal to infer the true viscosity of the grinding fluid at the grinding interface, non-contact in-situ sensing of rheological properties within micron-level gaps is achieved without relying on any contact viscometer; Third, by combining the self-cleaning of the Venturi pulse pipeline with acoustic emission residual monitoring, an automated process of "quantitative determination of cleanliness - safety interlock switching" is established for the first time. These functions are not simply a superposition of technical features, but rather, through deep coupling of structure and method, the switching between dry and wet operating conditions is transformed from manual operation into a reliable automated routine function, significantly improving the actual uptime of the equipment and the process coverage. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure in an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the overall structure of the lower base plate in an embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the transverse cross-sectional structure of the lower base plate in an embodiment of the present invention.

[0030] Figure 4 for Figure 3 Enlarged view of part A.

[0031] Figure 5 This is a schematic diagram of the bottom structure of the lower base plate in an embodiment of the present invention.

[0032] Figure 6This is a schematic diagram of the dry / wet switching pipeline system in an embodiment of the present invention.

[0033] Figure 7 for Figure 6 Enlarged view of part B.

[0034] Figure 8 This is a schematic diagram of the internal channel configuration and airflow state of the Venturi nozzle in an embodiment of the present invention.

[0035] Figure 9 This is an overall flowchart of the control method in an embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures: 1-Grinding plate; 11-Upper working plate; 12-Lower base plate; 121-Liquid cooling channel; 122-Heating module embedded cavity; 123-PTC heating element; 124-Blind hole mounting cavity; 125-Acoustic emission sensor; 126-Annular air vibration isolation groove; 2-Controller; 3-Dry / wet switching pipeline system; 31-Grinding fluid supply main pipeline; 32-High pressure pulse airflow branch pipeline; 33-Venturi nozzle. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0038] Example 1: Overall Structure and Working Principle of the Equipment Please see Figures 1 to 5 This embodiment provides an integrated wet and dry dual-condition flow grinding and polishing machine, the core component of which is a grinding disc 1. The grinding disc 1 is formed by stacking and connecting an upper working disc 11 and a lower base disc 12 through a vacuum brazing process. The upper surface of the upper working disc 11 is the grinding surface, which is used to support the workpiece and apply grinding pressure.

[0039] The lower base plate 12 has a liquid cooling channel 121 and a heating module embedding cavity 122 machined inside. The two are independent and not spatially connected. The liquid cooling channel 121 is arranged in a serpentine or spiral shape inside the lower base plate 12 for the flow of cooling medium, such as cooling water or an aqueous ethylene glycol solution. A PTC ceramic heating element 123 is fixed inside the heating module embedding cavity 122. The liquid cooling channel 121 and the PTC heating element 123 together constitute the precision temperature control system of the grinding plate 1.

[0040] A blind hole mounting cavity 124 is also formed on the lower base plate 12. This blind hole mounting cavity 124 does not penetrate the upper surface of the upper working plate 11, and the vertical distance H between its bottom and the upper surface of the upper working plate 11 is controlled within the range of 2mm to 5mm, preferably 3mm, to ensure sensor sensitivity while avoiding damage from processing stress due to excessive distance. A high-temperature resistant and waterproof acoustic emission sensor 125 is embedded in the blind hole mounting cavity 124. Thermally conductive potting compound is filled between the acoustic emission sensor 125 and the inner wall of the blind hole mounting cavity 124. After the potting compound cures, it can simultaneously achieve acoustic coupling and thermal coupling between the acoustic emission sensor 125 and the lower surface of the upper working plate 11, and provides waterproof sealing and vibration protection for the sensor.

[0041] An annular air vibration isolation groove 126 is machined into the solid material of the lower base plate 12 between the liquid cooling channel 121 and the blind hole mounting cavity 124. This annular air vibration isolation groove 126 surrounds the blind hole mounting cavity 124, has a rectangular cross-section, and a groove depth of 50% of the depth of the blind hole mounting cavity 124. A depth within the range of 30% to 80% can achieve the desired effect. The annular air vibration isolation groove 126 contains air. Due to the significant acoustic impedance difference between the air and the metal material of the lower base plate 12 (acoustic impedance ratio approximately 1:100000), fluid flow noise propagating from the liquid cooling channel 121 is strongly reflected and attenuated at the air-metal interface, failing to effectively transmit to the acoustic emission sensor 125. This structural feature solves the technical problem of fluid background noise submerging the effective acoustic signal under wet grinding conditions, enabling the acoustic emission sensor 125 to capture abrasive acoustic events and grinding fluid characteristic signals with a signal-to-noise ratio higher than 12dB even in a continuously flowing fluid environment.

[0042] In addition, at least one spare temperature sensor (not shown in the figure) is embedded in the lower base plate 12, preferably a PT100 platinum resistance thermometer, to provide auxiliary monitoring and comparative verification of the temperature of the grinding disc substrate.

[0043] The controller 2 is installed in the equipment's electrical control cabinet and is electrically connected to components such as the acoustic emission sensor 125, the cooling medium supply device (including a cooling water pump and a temperature regulating valve) of the liquid-cooled flow channel 121, the PTC heating element 123, the backup temperature sensor, and the pulse solenoid valve in the dry / wet switching pipeline system 3 (described later). The controller 2 has built-in all the algorithm programs for executing the control method of this invention, including a time-domain / frequency-domain feature extraction module, an automatic operating condition identification module, a dry grinding predictive thermal protection decision module, a wet grinding viscosity calculation and temperature control module, and a pipeline cleaning acceptance and safety interlock module.

[0044] The working principle of the equipment is briefly described as follows: During the processing, the acoustic emission sensor 125 acts as an "in-situ solid-state acoustic monitoring point," continuously receiving acoustic emission signals from the upper surface of the upper working disc 11. The physical source of this signal varies fundamentally depending on the working conditions: under dry grinding conditions, the signal mainly originates from the propagation of microcracks in the workpiece material under grinding pressure, abrasive particle breakage, and elastic wave release at the friction interface, with high-frequency components in the range of 50kHz to 200kHz being particularly sensitive to microcrack propagation; under wet grinding conditions, the signal mainly originates from the fluid-structure interaction between the grinding disc, grinding fluid, and workpiece, specifically manifested as a composite signal of grinding fluid dynamic noise and solid contact friction sound; during the pipeline purging and cleaning stage, the signal originates from the sudden high-frequency impact generated by abrasive residue striking the inner wall of the pipeline and the surface of the grinding disc.

[0045] The acoustic emission sensor 125 converts the elastic waves generated by these physical processes into electrical signals, which are then transmitted to the controller 2 after being conditioned by an amplifier. The controller 2 extracts time-domain features such as root mean square (RMS) and event count rate, and frequency-domain features such as energy proportion of each frequency band, center frequency, and power spectral density, based on a preset signal processing algorithm. It then automatically determines the current operating mode, assesses the risk of thermal damage, or calculates the viscosity of the grinding interface based on the combination of feature parameters, and outputs corresponding control commands to drive the cooling medium supply device of the liquid cooling channel 121 or the PTC heating element 123 to perform temperature control actions, or to drive the dry-wet switching pipeline system 3 to perform pipeline self-cleaning and operating mode switching.

[0046] Example 2: Dry / Wet Switching Piping System Please see Figures 6 to 8 The dry / wet switching piping system 3 is installed above the grinding plate 1, and its structure is as follows.

[0047] The piping system includes a main grinding fluid supply line 31, one end of which is connected to the grinding fluid storage tank via a supply pump, and the other end extends to the upper surface near the grinding plate 1. A high-pressure pulsed airflow branch line 32 is connected in parallel to the side of the main grinding fluid supply line 31. The air source is a compressed air source provided by the equipment, and the on / off state of the airflow and the pulse frequency are controlled by a pulse solenoid valve, preferably between 1Hz and 5Hz. The two lines converge through an integrated module containing a mixing chamber and a Venturi nozzle 33. The Venturi nozzle 33 also serves as a drip nozzle for the grinding fluid, and its internal channel has a constriction-expansion configuration, with the diameter of the constriction point approximately 40% to 60% of the inlet diameter.

[0048] During normal wet grinding operations, the grinding fluid supply pump is turned on and the pulse solenoid valve is closed. The grinding fluid flows smoothly through the Venturi nozzle 33 and drips onto the surface of the grinding disc. At this time, the Venturi effect is not significant.

[0049] Upon receiving the operating condition switching command, controller 2 first cuts off the grinding fluid supply pump, then opens the pulse solenoid valve to introduce compressed air pulses into the grinding fluid supply main pipeline 31. When the high-pressure airflow passes through the Venturi nozzle 33, the velocity increases sharply at the constriction, reaching over 100 m / s. According to Bernoulli's principle, the static pressure at this point decreases significantly, forming a local negative pressure zone. This negative pressure zone generates a suction force that pulls out the abrasive slurry adhering to the inner wall of the pipeline. Combined with the periodic pulling action of the pulsed airflow, the adhesion interface between the slurry and the pipe wall is gradually destroyed. Finally, the high-speed airflow carries the stripped residue out of the pipeline. This process decomposes the single purging force into a synergistic combination of negative pressure adsorption force, pulse tearing force, and airflow pushing force, effectively solving the problem of blind spots in cleaning pipe bends, joints, and other dead angles caused by traditional direct airflow.

[0050] During the purging process, the acoustic emission sensor 125 operates continuously. The acoustic emission signals generated by the impact of abrasive residue on the inner wall of the pipeline and the surface of the grinding disc are transmitted to the acoustic emission sensor 125 embedded inside the grinding disc 1 via a solid-state sound transmission path composed of the pipeline itself, the equipment frame, and the grinding spindle. The controller 2 extracts the attenuated burst characteristics in the signal: in the early stage of purging, due to the removal of a large number of residual abrasive particles, the peak count of acoustic emission events and the proportion of high-frequency energy in the signal are relatively high; as the cleaning process progresses, the number of residual abrasive particles on the inner wall of the pipeline gradually decreases, and the above two parameters gradually attenuate.

[0051] When, within a preset second time window, for example, for three consecutive minutes, the peak count of detected acoustic emission events remains consistently below a preset cleaning threshold, and the energy proportion of the signal in the high-frequency band above 10kHz is also below a preset cleaning energy threshold, controller 2 determines that the abrasive particles adhering to the inner wall of the pipeline have been removed to an acceptable level. At this time, controller 2 outputs a safety interlock signal allowing the switching of operating conditions, and the equipment can then perform subsequent operating condition switching actions, such as adjusting the grinding disc speed or switching process parameter settings. This process transforms the pipeline cleaning effect from relying on human experience to closed-loop acceptance based on quantitative acoustic indicators, filling the technological gap in self-cleaning reliability of dry and wet dual-condition equipment.

[0052] Example 3: Specific steps of the control method Please see Figure 9 This embodiment describes in detail the specific execution steps of the control method.

[0053] Step S1: The controller 2 continuously acquires the real-time acoustic emission waveform signal output by the acoustic emission sensor 125 at a sampling frequency of 1MHz.

[0054] Step S2: Controller 2 preprocesses the real-time signal, including bandpass filtering and noise reduction from 10kHz to 1MHz. Then, it calculates the root mean square (RMS) value of the signal in the time domain and calculates the event count rate using a set fixed threshold voltage as the event trigger threshold. In the frequency domain, it calculates the energy proportion, center frequency, and power spectral density of each specified frequency band using Fast Fourier Transform (FFT).

[0055] Step S3: Controller 2 automatically determines the current operating mode based on time-domain and frequency-domain characteristic parameters. Specific determination rules are as follows: when the ratio of the standard deviation to the average value of the signal RMS value within a 30-second sliding window is, for example, less than 0.2, and the proportion of high-frequency energy above 10kHz to the total energy is, for example, less than 10%, it is determined to be a wet grinding condition; when the ratio of the standard deviation to the average value of the RMS value exceeds, for example, 0.5, and the number of burst-type high-frequency events per second exceeds, for example, more than 50, it is determined to be a dry grinding condition.

[0056] Step S4: After entering the dry grinding mode, controller 2 executes the dry grinding temperature control subroutine. This subroutine continuously monitors the acoustic emission event count rate in the 50kHz to 200kHz frequency band. Experimental calibration data shows that during the dry grinding of hard and brittle materials, taking sapphire wafers as an example, when the subsurface microcracks of the workpiece are in a stable propagation stage, the event count rate in this frequency band is usually maintained at 100 to 200 times / second; once the workpiece enters the critical state where thermal damage is about to occur, the microcracks exhibit unstable propagation, and the event count rate in this frequency band will rise sharply within 1 second, with the growth rate significantly exceeding 200%, reaching 400 to 600 times / second or even higher. Once controller 2 detects this sudden change in growth rate, regardless of whether the reading of the backup temperature sensor (PT100) has reached the preset temperature warning line, it immediately triggers the liquid cooling channel 121 to introduce cooling medium and starts the external semiconductor cooling chip and fan to force-cool the grinding plate 1, pulling the grinding interface temperature back from the critical state to the safe range. Comparative tests show that, after adopting this predictive protection strategy, the subsurface damage layer depth of sapphire wafers after dry grinding is reduced from 8μm to 12μm under the traditional temperature feedback control mode to 3μm to 5μm, a reduction of more than 50%.

[0057] Step S5: After entering the wet grinding condition, controller 2 executes the wet grinding temperature control subroutine. This subroutine operates based on a mathematical model that has been experimentally calibrated and stored in controller 2. The calibration method is as follows: under well-controlled constant temperature conditions, acoustic emission signals are collected using a standard viscosity liquid under simulated grinding conditions. The center frequencies of the acoustic emission signals under different viscosity and temperature combinations are recorded, and a three-dimensional mapping relationship table of center frequency-viscosity-temperature is established. During the real-time control phase, controller 2 continuously monitors the center frequency of the acoustic emission signal. When the center frequency shifts to a lower frequency direction by more than a preset threshold, for example, if the shift exceeds 5% of the initial center frequency, it is determined that the viscosity of the grinding fluid at the grinding interface has dropped to the lower limit of the critical rupture value of the lubricating film due to local frictional temperature rise. At this time, controller 2 outputs control commands to increase the flow rate of the cooling medium in the liquid cooling channel 121 or reduce the inlet temperature of the cooling medium to suppress the temperature rise of the grinding fluid body and promote its viscosity to return to the process window range until the center frequency returns to the preset target frequency range. During this process, the PTC heating element 123 performs auxiliary fine-tuning heating as needed to prevent excessive cooling that could lead to excessively high viscosity of the grinding slurry.

[0058] Step S6: When controller 2 receives a dry / wet condition switching command input by the operator or automatically triggered by the process formula, it executes the condition switching self-cleaning judgment and control process. The specific steps have been detailed in Example 2 and will not be repeated here.

[0059] Example 4: Industrial Application Verification The apparatus and method of this embodiment are applied to a continuous thinning-polishing process for silicon carbide substrates, with the workpiece being a 6-inch silicon carbide wafer.

[0060] The process flow is set as follows: first, dry diamond rough grinding is performed to thin the surface, with an abrasive particle size D50 of 15μm, a grinding pressure of 0.3MPa, and a grinding disc speed of 60rpm. Then, it automatically switches to wet chemical mechanical polishing for finishing, with an abrasive particle size D50 of 0.5μm, using an oxidizing agent-containing polishing fluid, a grinding pressure of 0.1MPa, and a grinding disc speed of 80rpm.

[0061] Setting up a comparison example: The traditional control mode, which uses the same host platform but does not enable acoustic emission predictive thermal protection and Venturi self-cleaning acceptance function, relies on thermal resistance feedback for temperature control, manual timed purging of pipelines, and manual switching of operating conditions after judging the cleaning effect.

[0062] Two methods were used to continuously process 20 silicon carbide wafers respectively. The test results showed that: Table 1: Comparison of Silicon Carbide Wafer Processing Effects In this embodiment, the subsurface damage depth during the dry grinding stage is reduced from 10.5 μm to 4.2 μm through acoustic emission predictive thermal protection, providing a better surface condition foundation for subsequent wet grinding finishing. During the wet grinding stage, the surface roughness Ra is improved from 0.8 nm to 0.3 nm through interfacial viscosity closed-loop control. The pipeline self-cleaning acceptance mechanism reduces the dry-wet switching time from 15 minutes to 3 minutes, and no scrap products caused by pipeline cross-contamination occur during the entire batch processing.

[0063] Variations In the above embodiment, the annular air vibration isolation groove 126 adopts a rectangular cross-section, but depending on the convenience of the processing technology and the stress distribution requirements, its cross-sectional shape can also be trapezoidal or V-shaped. In the above embodiment, the Venturi nozzle 33 and the end of the grinding fluid supply main pipeline 31 are manufactured as an integrated unit, but it can also be used as an independent replaceable standard part, connected to the end of the pipeline by means of threads or bayonet, so as to facilitate the replacement of different specifications of Venturi nozzles according to different abrasive types and purging processes. In the above embodiment, the sampling frequency of the acoustic emission sensor 125 is 1MHz, but depending on the difference in processing materials and monitoring frequency bands, this frequency can be adjusted between 500kHz and 5MHz.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any equivalent substitutions, partial modifications, and optimized combinations made to the specific structures, parameters, and algorithms in the above embodiments within the spirit and principles of the present invention, without departing from the technical mechanism of the present invention, should be included within the protection scope of the present invention.

Claims

1. A dry and wet dual-condition integrated flow grinding and polishing machine, characterized in that, include: A grinding disc (1), wherein the grinding disc is composed of an upper working disc (11) and a lower base disc (12) stacked and connected; The lower base plate (12) has an independent liquid cooling channel (121) and a heating module embedding cavity (122) inside. The liquid cooling channel (121) is used to circulate the cooling medium, and the heating module embedding cavity (122) is provided with a PTC heating element (123). The lower base plate (12) also has a blind hole mounting cavity (124), in which a high temperature resistant and waterproof acoustic emission sensor (125) is embedded and sealed. The vertical distance between the bottom of the blind hole mounting cavity (124) and the upper surface of the upper working plate (11) is 2mm to 5mm. An annular air vibration isolation groove (126) is machined between the liquid cooling channel (121) and the blind hole mounting cavity. The annular air vibration isolation groove (126) is arranged around the blind hole mounting cavity (124) to attenuate the interference of background noise generated by the fluid flow in the liquid cooling channel (121) on the acoustic emission sensor. A controller (2) is electrically connected to the acoustic emission sensor (125), the cooling medium supply device of the liquid cooling channel (121), and the PTC heating element (123). The controller (2) is configured to: predict the risk of dry grinding thermal damage and initiate cooling action in advance based on the change trend of the high-frequency event count rate in the frequency range of the acoustic emission signal collected by the acoustic emission sensor (125) in the frequency domain characteristic parameters between 50kHz and 200kHz; and calculate the viscosity change trend of the grinding fluid at the grinding interface based on the center frequency offset or power spectral density change in the frequency domain characteristic parameters of the acoustic emission signal, and adjust the temperature and / or flow rate of the cooling medium in the liquid cooling channel (121) in the opposite direction.

2. The integrated wet and dry dual-condition flow grinding and polishing machine according to claim 1, characterized in that, It also includes a dry-wet switching piping system (3), which includes: Grinding fluid supply main line (31); A high-pressure pulsed airflow branch (32) is connected in parallel with the main grinding fluid supply line (31). A Venturi nozzle (33) is located at the end of the grinding fluid supply main pipeline (31) and near the inlet of the grinding plate (1). Upon receiving the working condition switching command, the controller (2) controls the high-pressure pulse airflow branch (32) to supply pulse airflow to the grinding fluid supply main pipeline (31). The venturi nozzle (33) generates local negative pressure when the airflow passes through, so as to entrain and peel off the residual abrasive particles attached to the inner wall of the pipeline.

3. The integrated wet and dry dual-condition flow grinding and polishing machine according to claim 2, characterized in that, The controller (2) is further configured as follows: During the purging process of the high-pressure pulsed airflow branch (32), the acoustic emission signal collected by the acoustic emission sensor (125) is acquired; When the peak count of acoustic emission events detected within a preset time window is lower than a preset cleaning threshold, and the proportion of high-frequency energy in the frequency domain characteristic parameters of the acoustic emission signal is lower than a preset cleaning energy threshold, it is determined that the residual abrasive particles in the pipeline have been removed, and a safety interlock signal that allows the switching of operating conditions is output.

4. The integrated wet and dry dual-condition flow grinding and polishing machine according to claim 1, characterized in that, The cross-sectional shape of the annular air vibration isolation groove (126) is rectangular, trapezoidal or V-shaped, and the groove depth is 30% to 80% of the depth of the blind hole mounting cavity.

5. The integrated wet and dry dual-condition flow grinding and polishing machine according to claim 1, characterized in that, The inner wall of the blind hole mounting cavity (124) and the acoustic emission sensor (125) are filled with thermally conductive potting compound so that the acoustic emission sensor (125) can achieve acoustic and thermal coupling with the lower surface of the upper working disk (11) through the potting compound.

6. The integrated wet and dry dual-condition flow grinding and polishing machine according to claim 1, characterized in that, At least one backup temperature sensor is also embedded in the lower base plate (12). When the high-frequency event count rate detected by the acoustic emission sensor (125) increases by more than 200% within 1 second under dry grinding conditions, but the real-time temperature detected by the backup temperature sensor has not yet reached the preset temperature warning line, the controller (2) starts the cooling action of the liquid cooling channel in advance and simultaneously starts the semiconductor cooling chip and / or fan to force cooling of the grinding plate (1).

7. A control method for a wet / dry dual-condition integrated flow grinding and polishing machine, applied to the wet / dry dual-condition integrated flow grinding and polishing machine as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Acquire the real-time acoustic emission signal collected by the acoustic emission sensor (125); Step S2: Extract time-domain features and frequency-domain features from the real-time acoustic emission signal to obtain time-domain feature parameters and frequency-domain feature parameters; Step S3: Determine the current working mode of the grinding and polishing machine based on the time-domain feature parameters. The working mode includes dry grinding mode and wet grinding mode. Step S4: When it is determined to be a dry grinding condition, execute the dry grinding temperature control subroutine: monitor the acoustic emission event count rate in the frequency range of 50kHz to 200kHz. When the growth rate of the acoustic emission event count rate in this range exceeds the preset multiple in the first preset time window, it is determined that there is a risk of dry grinding thermal damage, and the cooling action of the liquid cooling channel (121) is started in advance. Step S5: When it is determined to be a wet grinding condition, execute the wet grinding temperature control subroutine: based on the center frequency offset or power spectral density change in the frequency domain characteristic parameters, calculate the viscosity change trend of the grinding fluid at the grinding interface, and adjust the temperature and / or flow rate of the cooling medium through the liquid cooling channel (121) in reverse according to the viscosity change trend.

8. The control method according to claim 7, characterized in that, The specific method for determining the operating mode in step S3 is as follows: When the root mean square value of the signal in the time domain characteristic parameters remains stable and the proportion of high-frequency energy in the frequency domain characteristic parameters is lower than the first set threshold, it is determined to be a wet grinding condition. When the fluctuation amplitude of the root mean square value of the signal in the time domain characteristic parameters exceeds the second set threshold, and the count rate of burst-type high-frequency events in the frequency domain characteristic parameters exceeds the third set threshold, it is determined to be a dry grinding condition.

9. The control method according to claim 7, characterized in that, It also includes step S6: self-cleaning judgment and control during operating condition switching, specifically including: Receive operating condition switching instructions; After the grinding fluid supply is cut off, the high-pressure pulse airflow branch (32) connected in parallel with the grinding fluid supply main line (31) is started, and the pipeline is pulse-purged through the Venturi nozzle (33); Acquire the acoustic emission signal collected by the acoustic emission sensor (125) during the purging process; Extract the attenuated burst signal characteristics of the acoustic emission signal; When the peak count of detected acoustic emission events is lower than the preset cleaning threshold and the proportion of high-frequency energy in the frequency domain characteristic parameters is lower than the preset cleaning energy threshold within the second preset time window, it is determined that the residual abrasive particles in the pipeline have been removed, and a safety interlock signal that allows the switching of operating conditions is output.

10. The control method according to claim 7, characterized in that, The step S5, "calculating the viscosity change trend of the grinding fluid at the grinding interface based on the center frequency offset or power spectral density change in the frequency domain characteristic parameters," specifically includes: A calibration mathematical model of the coupling relationship between the center frequency of the acoustic emission signal and the viscosity-temperature of the grinding fluid is established and pre-stored in the controller (2); Real-time monitoring of the center frequency of the acoustic emission signal; When the detected center frequency shifts to a lower frequency direction by more than the preset frequency shift threshold, it is determined that the viscosity of the grinding fluid at the grinding interface has decreased to the preset lower limit threshold due to the increase in temperature. The reverse adjustment specifically involves increasing the flow rate of the cooling medium in the liquid cooling channel or reducing its temperature to suppress the temperature rise of the grinding fluid body until the center frequency returns to the preset target frequency range.

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