Intelligent system and method for laser dressing of grinding wheel

Abstract

A kind of intelligent system of grinding wheel laser dressing belongs to grinding wheel dressing field, including input, processing system and output;Grinding wheel data is input to processing system by input, processing system is composed of database, CAM system and monitoring system;The product generated by processing system is obtained by output.The method for laser dressing grinding wheel includes, 1: grinding wheel data is input to system;2: monitoring system automatically generates tool setting point, allowance information;3: optimization processing process parameters;4: calculate laser beam posture adjustment mode, laser energy compensation mode, generate trajectory planning;Step 5: interpolation motion, dress grinding wheel;Step 6: monitor processing process, observe allowance change;Step 7: after allowance meets, monitoring system sends stop detection information;The present application can be according to the appearance size of sand wheel blank in the process of drawing design and dressing, carry out laser beam posture adjustment, energy compensation, also can realize the autonomous iteration of whole process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of grinding wheel dressing, and particularly relates to a grinding wheel laser dressing intelligent system and method. BACKGROUND

[0002] Current grinding wheel laser dressing highly depends on manual work, and in the aspects of laser parameter setting, grinding wheel material analysis, processing parameter determination, part dressing steps (such as tool setting), dressing automation and completion determination, feeding and discharging and the like, manual work is relied on.

[0003] The intelligent processing system focuses on manual replacement, including manual operation, process experience judgment, feeding and discharging and the like. The difference between the intelligent processing system and the traditional automation is that the automation mainly replaces manual operation, such as automatic feeding and automatic interpolation. The intelligent processing system is different, which uses database data analysis to form experience parameter selection. Visual, sound, heat, electromagnetic, force and the like are used for judgment to monitor the whole processing process. CAM core algorithm is used to plan and customize the processing grinding wheel. Therefore, the intelligent processing system is not a simple upgrade of the automation, but a comprehensive replacement of manual processing including the automation.

[0004] The forming grinding wheel laser dressing system is currently in the process test stage, and has not formed an integrated, automated and intelligent processing system. SUMMARY

[0005] The application aims to provide a grinding wheel laser dressing intelligent system and method. The intelligent system can adjust the laser beam posture and compensate the energy according to the profile requirements of the drawing design and the real-time changing shape size of the grinding wheel blank during the dressing process, and can also realize the whole-process autonomous iteration and the iteration upgrade of the whole processing system. The method realizes the automatic generation of the trajectory planning through the dressing parameter determination, the defocusing amount compensation and the avoidance of the laser interference.

[0006] The technical scheme adopted by the application is as follows:

[0007] A grinding wheel laser dressing intelligent system, comprising an input end, a processing system and an output end.

[0008] The input end inputs the grinding wheel data into the processing system according to the product demand, wherein the grinding wheel data comprises the profile requirement parameters and the model designed on the drawing, and the material information and the shape size of the grinding wheel blank; the drawing is in a digital form, and the material information and the shape size of the grinding wheel blank are obtained by using various sensors, cameras and the like hardware facilities on the machine tool.

[0009] The processing system consists of a database, a CAM system and a monitoring system; the database can realize four functions: expert prediction, parameter optimization, digital twin and machine learning; the CAM system receives the processing parameters from the database and performs two functions: laser beam posture adjustment and energy compensation based on the processing parameters; the functions of the monitoring system include judging the allowance of grinding wheel dressing, identifying tool points and judging abnormal situations. On the one hand, the monitoring system feeds back the real-time processing data to the database to help upgrade the database; on the other hand, it interacts with the CAM, outputs the real-time processing position and allowance information required by the CAM system, and accepts the follow-up control of the CAM system; during the operation of the processing system, autonomous iteration of the entire process is realized, and the entire processing system is iteratively upgraded;

[0010] The output terminal obtains the products produced by the processing system, including qualified grinding wheels and test reports, and outputs qualified grinding wheels (customers), processing test results (customers), and processing cost consumption (factory).

[0011] A method for intelligent laser dressing of a grinding wheel, comprising the following steps:

[0012] Step 1: Input the grinding wheel data into the grinding wheel laser dressing intelligent system through the input end;

[0013] Step 2: The monitoring system compares and analyzes the outer dimensions of the grinding wheel blank and the contour parameters of the drawing, and then automatically generates the tool setting point and allowance information;

[0014] The monitoring system mainly analyzes the actual dimensions of the blank and then compares the two, which is like blindly looking for differences.

[0015] Step 3: Compare the material information and dimensions of the grinding wheel blank with the dressing cases stored in the database to find similar or consistent dressing cases. Then, optimize the processing parameters through expert prediction and parameter optimization functions. If there are no similar cases, machine learning is performed on known cases to generate a set of processing parameters. The generated processing parameters are prepared for the digital twin.

[0016] Step 4: Send the processing parameters generated by the database to the CAM system. The CAM system calculates the laser beam posture adjustment method and laser energy compensation method according to the grinding wheel profile requirements and processing parameters, and generates the trajectory planning of the laser processing process.

[0017] Step 5: The machine tool performs interpolation motion according to the trajectory plan generated by the CAM system and starts dressing the grinding wheel;

[0018] Step 6: After the interpolation motion starts, the monitoring system monitors the machining process and observes the changes in the blank's allowance in real time. Then, through template matching and target recognition, it sends the real-time allowance and grinding wheel blank position information to the CAM system and database;

[0019] The CAM system uses the allowance and blank position information to compensate for abnormal processing points, and the database uses real-time position and allowance to create a digital twin representation;

[0020] Step 7: After the margin meets the processing requirements, the monitoring system sends a message, stops the machine, and performs inspection;

[0021] Step 8: Output the test results. If the product is qualified, the qualified product and test report will be output; if it is unqualified, the grinding wheel information will be re-analyzed and the next round of dressing will be planned;

[0022] Step 9: If the special grinding wheel is difficult to pass after repeated dressing, use the system iteration function to optimize the system database and find more optimized parameters.

[0023] Furthermore, in step 2, the monitoring system automatically generates tool setting points and allowance information according to the following method:

[0024] For the judgment of grinding wheel blanks: judge the size of the blank machining allowance by visual observation and inspection;

[0025] For tool point detection: a trial burn method is used, followed by visual observation to determine the position of the molten pool and the laser tool tip; when a mechanical method is used, the tool depth and position are determined through sound sensing and vision;

[0026] For monitoring of the processing process: determine whether the energy absorption of the processing points is uniform based on the energy of the laser optical spectrometer; compare the actual contour observed by visual observation with the contour required by the drawing, and determine whether the processing is completed based on the difference between the two; determine the circumference roundness, runout, and contour accuracy of the finished product based on visual observation and edge detection synthesis algorithm; determine the operating status of the entire equipment based on sound and current.

[0027] The monitoring system is a full-process monitoring system, requiring custom assembly, depending on the visual, optical, or acoustic method. Common methods include direct visual observation using a backlight. Optical methods include spectrometer detection, and acoustic vibration sensing for tool setting. These systems are used to determine grinding wheel blank allowance, tool setting point detection, abnormal machining points, shutdown determination upon completion of machining, finished product inspection, and comprehensive equipment monitoring.

[0028] Furthermore, in step 3, the particle swarm optimization (PSO) algorithm is used to optimize the machining process parameters. The algorithm includes the following steps:

[0029] S301, using a random method to initialize the position and speed of the particle swarm; including the historical optimal position of a single particle and the historical optimal position of the swarm, the historical optimal fitness value of a single particle and the historical optimal fitness value of the swarm;

[0030] S302, update the position and velocity of a single particle using formulas (1) and (2):

[0031]

[0032] The distance and direction of each particle's next step in the PSO algorithm is a position vector, called the speed of the next iteration, expressed as:

[0033]

[0034] in, represents the position vector of particle i in the dth dimension at the k+1th iteration; represents the position vector of particle i in the dth dimension at the kth iteration; represents the velocity vector of the dth dimension of particle i in the k+1th iteration; represents the velocity vector of particle i in the dth dimension at the kth iteration; ω represents the inertia weight; c1 and c2 represent learning factors; r1 and r2 represent two random numbers with a value range of 0 to 1; represents the historical optimal position of particle i in the d-th dimension at the k-th iteration, that is, the optimal solution obtained by the i-th particle (individual) in the d-th dimension after the k-th iteration; It represents the historical optimal position of the swarm (globally) in the d-th dimension at the k-th iteration, that is, the optimal solution of the entire particle swarm in the d-th dimension after the k-th iteration;

[0035] S303, calculate the fitness value of a single particle. The fitness value must meet the requirements of formula (3):

[0036]

[0037] Among them, η m Represents the fitness value of each particle; m represents the particle number; the fitness value represents the optimization target. If the fitness values ​​of each particle meet the tolerance requirements, the fitting result can be considered to have good detection credibility.

[0038] S304, updating the historical best fitting value of a single particle;

[0039] S305, updating the historical best fitting value and position of the group;

[0040] S306, update the inertia weight and number of iterations:

[0041] Using the linearly changing inertia weight strategy, the inertia weight is updated as follows (4):

[0042]

[0043] Among them, ω max and ω min They represent the maximum inertia weight and the minimum inertia weight respectively; iter represents the current number of iterations; iter max Indicates the maximum number of iterations;

[0044] S307: When the terminal condition is met, the final optimal solution is output; otherwise, steps S302 to S306 are repeated.

[0045] Furthermore, in step 5, the process of generating the trajectory plan by the CAM system includes the following steps:

[0046] The CAM trajectory planning system is used to plan and adjust the laser trajectory during dressing, including multi-pass optimization, real-time posture adjustment, energy compensation, and compensation for abnormal processing points. This system must be developed independently, as there is currently no CAM software, algorithm, or planning system available for grinding wheel laser dressing. These adjustments require a database containing data on the grinding wheel material processing process, such as single-pass ablation speed, the relationship between inclination angle and forming angle, the relationship between grinding wheel diameter, laser original cutting depth, and laser beam divergence angle, and the impact of feed rate on single-pass ablation speed. Trajectory planning is based on this data.

[0047] S501, trimming parameters are determined:

[0048] During tangential dressing, a laser spot is pulsed onto the grinding wheel surface, creating an elliptical shape. According to literature and industry consensus, laser dressing utilizes both tangential shaping and radial sharpening. For accuracy and formability, only tangential dressing is considered.

[0049] The spot overlap rate in the circumferential direction of the grinding wheel is defined as the ratio of the spot overlap area to the spot area under two pulses, expressed as Oc, which is described as:

[0050]

[0051] Among them, S overlap Indicates the area of ​​the overlapping part of the light spot; S ellipse Indicates the spot area; a e and b e Indicates the parameters of the ellipse; l c Indicates the offset of the center of the light spot in the circumferential direction;

[0052] The spot overlapping rate should be more than 85% to get better surface quality of the grinding wheel; the grinding wheel speed when the spot overlapping rate is 85% is given by formula (6):

[0053]

[0054] In the formula, D is the diameter of the grinding wheel; T represents the pulse period of the laser, which is the inverse of the repetition frequency;

[0055] The spot overlapping rate in the direction of the generatrix of the grinding wheel is defined as the ratio of the overlapping area of the spot to the area of the spot, which is denoted by O A A is described as:

[0056]

[0057] In the formula, l A is the offset of the center of the spot on the generatrix;

[0058] Then, the feed rate F of the grinding wheel at the speed n is calculated by formula (8):

[0059] F = nl A (8)

[0060] The dressing parameters can be determined by formula (5) to formula (8);

[0061] S502, defocus amount compensation:

[0062] The edge point of the grinding wheel is taken as the origin of the coordinates, the direction of the generatrix of the grinding wheel cylinder is taken as the X direction, the diameter direction is taken as the Y direction and the Z direction; before dressing, the surface of the grinding wheel cylinder is described as:

[0063]

[0064] The trajectory of the laser to be moved is described by formula (9) to construct a mathematical model of defocus amount compensation. In the formula, x, y and z are the positions of the three directions after the establishment of the coordinate system, and the coordinate origin is at the edge of the grinding wheel; B is the thickness of the grinding wheel (equivalent to the length of the generatrix of the cylinder);

[0065] When the spot is irradiated on the material surface, it is generally within the range of the Rayleigh length, at which time the laser beam can be considered as a cylinder. In the material removal process, the laser beam vertically irradiated needs to rotate around the laser beam focus O in the X-O-Z plane, and the state of rotating an angle a is described as:

[0066]

[0067] ​Where r represents the radius of the laser beam at a certain position; h represents the distance from the position to the laser focus; r0 represents the radius of the spot at the laser focus (h = 0 position). The laser beam adopts the near-field cylindrical model and r is always consistent with r0. L ray represents the Rayleigh length of the laser beam, and e0 is the initial defocus of the laser beam in the vertical state.

[0068] For vertical irradiation laser, the focus is on the XOY plane. As the laser beam rotates, the intersection of the laser beam and the grinding wheel (ie, the actual irradiation position) P T To maintain a stable defocus, compensation needs to be made in the X and Z directions. The compensation amount is:

[0069]

[0070] When defocus compensation is performed, it is assumed that the focus always remains on the XOY plane.

[0071] S503, Avoidance of laser interference:

[0072] When the point of interaction between the laser beam and the material exceeds the Rayleigh length, the laser beam is considered to be a far-field laser consisting of a hyperbola;

[0073] In the far-field model, using the asymptotic model, the radius value r at a certain height h in the beam direction is b It can be roughly described as:

[0074]

[0075] in, is the divergence angle of the laser beam; h b is the beam length;

[0076] In the vertical direction, the beam length h b The following geometric relationship is satisfied between it and the height h:

[0077] h b =h / cosα h (13)

[0078] Among them, α h Indicates the angle of rotation of the A-axis when the laser is half blocked;

[0079] The shape profile of the wafer chamfering grinding wheel is described by the following piecewise function (the contour shape of the wafer chamfering grinding wheel can be understood as a combination of straight lines and arcs):

[0080]

[0081] Among them, K srepresents the intercept of the hypotenuse, (x r ,y r ) represents the coordinates of the center of the arc, which changes with the arc number; θ represents the angle between the contour line and the horizontal direction; y represents the coordinate system position;

[0082] During the grinding wheel ablation process, the laser tip requires a certain cutting depth. Assuming that the cutting depth is fixed during processing, the actual position of the laser and the grinding wheel will be elevated by the circular effect of the grinding wheel. Therefore, the actual contour of the laser spot should be obtained by deforming the formed contour (in the actual processing process, the laser spot is not in the absolute tangential direction, but has a certain cutting depth. In previous methods, it was believed that the laser interpolation trajectory is the drawing contour trajectory. However, through theoretical calculations, the present invention found that the cutting depth causes the laser spot to be elevated on the grinding wheel surface, causing the removal point trajectory to be deformed relative to the laser interpolation trajectory). The height Δh of the elevated part is obtained by the following geometric relationship:

[0083]

[0084] in is the radius of the grinding wheel; a represents the cutting depth of the laser tool tip;

[0085] At a height of Δh, the shape profile y of the forming grinding wheel h Transformed into:

[0086]

[0087] When the laser beam deflection angle (the deflection used in this method, the laser beam deflection center, the A-axis rotation center and the laser beam focus are coincident, so the rotation angle is consistent. The laser head is on the A-axis, and the laser beam deflection angle is the angle of rotation of the A-axis) continues to increase, the laser beam will intersect with the outer circle of the grinding wheel, thereby causing the outer circle to block the laser light. At this time, the angle α h Calculated using the following formula:

[0088]

[0089] Where, α h It indicates the angle of rotation of the A axis when the laser is half blocked. Because experience tells us that when the laser beam is half blocked, the energy is insufficient to continue processing, and it is considered that the shielding effect is completely present at this time. Therefore, αh can be considered as the position of the beam centerline at the location where the shielding effect occurs. t Indicates the width of the groove, D indicates the diameter, x l Indicates the distance from a certain position to the center of the groove, mainly to facilitate mathematical calculations of the arc part. It can also be changed to x position; y is the y-axis position;

[0090] When the light blocking effect occurs, the corresponding critical angle α2 is described as:

[0091]

[0092] After the laser beam intersects the outer circle of the grinding wheel, the laser beam cannot penetrate the grinding wheel material and continue to irradiate the contour surface of the grinding wheel. Therefore, part of the laser energy is dispersed to the outer circle surface that should not be processed, and the formed contour cannot be copied.

[0093] The critical angle α2 of the grinding wheel blocking light is a series of critical values ​​that follow the change of x. For a certain point on the grinding wheel forming profile (except the outer cylindrical surface), there is always a laser blocking critical angle α2, so that when the angle of the laser beam deflection is greater than the critical angle α2, the laser is blocked by the outer cylindrical surface of the forming grinding wheel, and the dressing margin in the forming profile cannot be effectively removed; Therefore, the condition for laser dressing of the forming grinding wheel without blocking light is: the deflection angle of the laser is less than the critical angle of the light blocking at a certain point on the profile, that is:

[0094] α(x)<α2(x) (19)

[0095] In the α2 range, the laser power density drops sharply due to the laser being blocked, and the material cannot be removed. Therefore, when profiling the grinding wheel, different deflection angles α need to be used at different contours.

[0096] It can be seen that different laser deflection angles correspond to different positions on the arc of the grinding wheel. In actual processing technology, the deflection resolution M required for processing the arc is calculated using the following formula:

[0097]

[0098] Among them, K CW Is a parameter, take an integer; L g Indicates the length of the secant line of the arc contour, L α is the arc ablation length corresponding to the critical angle of bevel ablation.

[0099] Beneficial effects of the present invention:

[0100] The intelligent system for laser dressing of grinding wheels of the present invention can adjust the laser beam posture and perform energy compensation according to the contour requirements of the drawing design and the external dimensions of the grinding wheel blank that change in real time during the dressing process. It can also realize autonomous iteration of the entire process and iteratively upgrade the entire processing system. The method realizes automatic generation of trajectory planning by determining dressing parameters, compensating for defocus and avoiding laser interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 This is the overall technical solution diagram of the grinding wheel laser dressing intelligent system of the present invention;

[0102] Figure 2 It is a schematic diagram of the monitoring system monitoring the trimming process;

[0103] Figure 3 It is a schematic diagram of interference under the laser far-field model. DETAILED DESCRIPTION

[0104] like Figure 1 As shown, an intelligent system for laser dressing of grinding wheels includes an input end, a processing system and an output end;

[0105] The input end inputs the grinding wheel data into the processing system according to product requirements. The grinding wheel data includes the contour requirement parameters and model designed on the drawing, as well as the material information and external dimensions of the grinding wheel blank. The drawing is in digital form, and the material information and external dimensions of the grinding wheel blank are obtained using various sensors, cameras and other hardware facilities on the machine tool.

[0106] The processing system consists of a database, a CAM system and a monitoring system; the database can realize four functions: expert prediction, parameter optimization, digital twin and machine learning; the CAM system receives the processing parameters from the database and performs two functions: laser beam posture adjustment and energy compensation based on the processing parameters; the functions of the monitoring system include judging the allowance of grinding wheel dressing, identifying tool points and judging abnormal situations. On the one hand, the monitoring system feeds back the real-time processing data to the database to help upgrade the database; on the other hand, it interacts with the CAM, outputs the real-time processing position and allowance information required by the CAM system, and accepts the follow-up control of the CAM system; during the operation of the processing system, autonomous iteration of the entire process is realized, and the entire processing system is iteratively upgraded;

[0107] The output terminal obtains the products produced by the processing system, including qualified grinding wheels and test reports, and outputs qualified grinding wheels (customers), processing test results (customers), and processing cost consumption (factory).

[0108] A method for intelligent laser dressing of a grinding wheel, comprising the following steps:

[0109] Step 1: Input the grinding wheel data into the grinding wheel laser dressing system through the input port;

[0110] Step 2: The monitoring system compares and analyzes the outer dimensions of the grinding wheel blank and the contour parameters of the drawing, and then automatically generates the tool setting point and allowance information;

[0111] The monitoring system mainly analyzes the actual dimensions of the blank, and then compares the two. It is like blindly looking for differences. Figure 2 The monitoring system automatically generates tool setting points and allowance information according to the following methods:

[0112] For the judgment of grinding wheel blanks: judge the size of the blank machining allowance by visual observation and inspection;

[0113] For tool point detection: a trial burn method is used, followed by visual observation to determine the position of the molten pool and the laser tool tip; when a mechanical method is used, the tool depth and position are determined through sound sensing and vision;

[0114] For monitoring of the processing process: determine whether the energy absorption of the processing points is uniform based on the energy of the laser optical spectrometer; compare the actual contour observed by visual observation with the contour required by the drawing, and determine whether the processing is completed based on the difference between the two; determine the circumference roundness, runout, and contour accuracy of the finished product based on visual observation and edge detection synthesis algorithm; determine the operating status of the entire equipment based on sound and current.

[0115] The monitoring system is a full-process monitoring system, requiring custom assembly, depending on the visual, optical, or acoustic method. Common methods include direct visual observation using a backlight. Optical methods include spectrometer detection, and acoustic vibration sensing for tool setting. These systems are used to determine grinding wheel blank allowance, tool setting point detection, abnormal machining points, shutdown determination upon completion of machining, finished product inspection, and comprehensive equipment monitoring.

[0116] Step 3: Compare the material information and dimensions of the grinding wheel blank with the dressing cases stored in the database to find similar or consistent dressing cases. Then, optimize the processing parameters through expert prediction and parameter optimization functions. If there are no similar cases, machine learning is performed on known cases to generate a set of processing parameters. The generated processing parameters are prepared for the digital twin.

[0117] The particle swarm optimization (PSO) algorithm is used to optimize the machining process parameters. The algorithm includes the following steps:

[0118] The database requires a large amount of grinding wheel dressing data to determine the grinding wheel dressing process parameters. This determination utilizes predictive systems, parameter classification, parameter optimization, and machine learning to complete the three tasks of laser parameter setting, grinding wheel material analysis, and process parameter determination during the machining process. Laser parameter settings include laser power (10-200W), repetition rate (50-200kHz), pulse width (100fs-200ns), and wavelength (100-1064nm). Grinding wheel materials include metals, resins, ceramics, and their composite binders, as well as heterogeneous abrasive materials such as diamond and CBN. Machining techniques include pure laser methods such as galvanometer scanning, interpolation dressing, deflected laser, and deep-cutting; pure EDM methods such as EDM, powder-mixed EDM, and dry EDM; and mechanical methods such as mechanical profiling and forming, as well as combinations of these processes. The parameters used in all these processes are referred to as process parameters.

[0119] The database-based expert system is an independent library built by the company. The expert system's data summarization and mining needs to be based on the particle swarm optimization (PSO) algorithm, because the PSO algorithm's rapid convergence can meet the real-time and low-latency requirements of the trimming system.

[0120] S301, using a random method to initialize the position and velocity of the particle swarm; including the historical optimal position of a single particle and the historical optimal position of the swarm, the historical optimal fitness value of a single particle and the historical optimal fitness value of the swarm;

[0121] S302, update the position and velocity of a single particle using formulas (1) and (2):

[0122]

[0123] The distance and direction of each particle's next step in the PSO algorithm is a position vector, called the speed of the next iteration, expressed as:

[0124]

[0125] in, represents the position vector of particle i in the dth dimension at the k+1th iteration; represents the position vector of particle i in the dth dimension at the kth iteration; represents the velocity vector of the dth dimension of particle i in the k+1th iteration; represents the velocity vector of particle i in the dth dimension at the kth iteration; ω represents the inertia weight; c1 and c2 represent learning factors; r1 and r2 represent two random numbers with a value range of 0 to 1; represents the historical optimal position of particle i in the d-th dimension at the k-th iteration, that is, the optimal solution obtained by the i-th particle (individual) in the d-th dimension after the k-th iteration; It represents the historical optimal position of the swarm (globally) in the d-th dimension at the k-th iteration, that is, the optimal solution of the entire particle swarm in the d-th dimension after the k-th iteration;

[0126] S303, calculate the fitness value of a single particle. The fitness value must meet the requirements of formula (3):

[0127]

[0128] Among them, η m Represents the fitness value of each particle; m represents the particle number; the fitness value represents the optimization target. If the fitness values ​​of each particle meet the tolerance requirements, the fitting result can be considered to have good detection credibility.

[0129] S304, updating the historical best fitting value of a single particle;

[0130] S305, updating the historical best fitting value and position of the group;

[0131] S306, update the inertia weight and number of iterations:

[0132] Using the linearly changing inertia weight strategy, the inertia weight is updated as follows (4):

[0133]

[0134] Among them, ω max and ω min They represent the maximum inertia weight and the minimum inertia weight respectively; iter represents the current number of iterations; iter max Indicates the maximum number of iterations;

[0135] S307: When the terminal condition is met, the final optimal solution is output; otherwise, steps S302 to S306 are repeated.

[0136] Step 4: Send the processing parameters generated by the database to the CAM system. The CAM system calculates the laser beam posture adjustment method and laser energy compensation method according to the grinding wheel profile requirements and processing parameters, and generates the trajectory planning of the laser processing process.

[0137] Step 5: The machine tool performs interpolation motion according to the trajectory plan generated by the CAM system and starts dressing the grinding wheel. The process of the CAM system generating the trajectory plan includes the following steps:

[0138] The CAM trajectory planning system is used to plan and adjust the laser trajectory during dressing, including multi-pass optimization, real-time posture adjustment, energy compensation, and compensation for abnormal processing points. This system must be developed independently, as there is currently no CAM software, algorithm, or planning system available for grinding wheel laser dressing. These adjustments require a database containing data on the grinding wheel material processing process, such as single-pass ablation speed, the relationship between inclination angle and forming angle, the relationship between grinding wheel diameter, laser original cutting depth, and laser beam divergence angle, and the impact of feed rate on single-pass ablation speed. Trajectory planning is based on this data.

[0139] S501, trimming parameters are determined:

[0140] During tangential dressing, a laser spot is pulsed onto the grinding wheel surface, creating an elliptical shape. According to literature and industry consensus, laser dressing utilizes both tangential shaping and radial sharpening. For accuracy and formability, only tangential dressing is considered.

[0141] The spot overlap rate in the circumferential direction of the grinding wheel is defined as the ratio of the spot overlap area to the spot area under two pulses, expressed as Oc, which is described as:

[0142]

[0143] Among them, S overlap Indicates the area of ​​the overlapping part of the light spot; S ellipse Indicates the spot area; a e and b e Indicates the parameters of the ellipse; l c Indicates the offset of the center of the light spot in the circumferential direction;

[0144] The spot overlap rate must reach more than 85% to obtain a better grinding wheel surface quality; the grinding wheel speed when the spot overlap rate reaches 85% is given by formula (6):

[0145]

[0146] Where D is the diameter of the grinding wheel; T represents the pulse period of the laser, which is the inverse of the repetition frequency;

[0147] The light spot overlap rate in the direction of the grinding wheel generatrix is ​​defined as the ratio of the area of ​​the light spot overlap to the area of ​​the light spot, expressed as O A Indicates that O A Described as:

[0148]

[0149] Among them, l A is the offset of the center of the light spot on the busbar;

[0150] Then, at the rotation speed n, the grinding wheel feed rate F is calculated by formula (8):

[0151] F=nl A (8)

[0152] The trimming parameters can be determined by formula (5) to formula (8);

[0153] S502, defocus compensation:

[0154] The edge of the grinding wheel is taken as the origin of the coordinates, the generatrix direction of the grinding wheel cylinder is taken as the X direction, and the diameter direction is taken as the Y direction and the Z direction. Before the grinding wheel is dressed, its surface cylindrical annulus is described as:

[0155]

[0156] The mathematical model for defocus compensation is constructed by describing the trajectory of the laser using formula (9). In the formula, x, y, and z are the three directional positions after the coordinate system is established, and the origin of the coordinate is at the edge of the grinding wheel; B is the thickness of the grinding wheel (equivalent to the length of the main line of the cylinder);

[0157] The spot is irradiated on the material surface, generally within the Rayleigh length range. At this time, the laser beam can be considered cylindrical. During the material removal process, the vertically irradiated laser beam needs to rotate in the XOZ plane with the laser beam focus O as the rotation center. The state of rotation angle α is described as:

[0158]

[0159] Where r represents the radius of the laser beam at a certain position; h represents the distance from the position to the laser focus; r0 represents the radius of the spot at the laser focus (h = 0 position). The laser beam adopts the near-field cylindrical model and r is always consistent with r0. L ray represents the Rayleigh length of the laser beam, and e0 is the initial defocus of the laser beam in the vertical state.

[0160] For vertical irradiation laser, the focus is on the XOY plane. As the laser beam rotates, the intersection of the laser beam and the grinding wheel (ie, the actual irradiation position) P T To maintain a stable defocus, compensation needs to be made in the X and Z directions. The compensation amount is:

[0161]

[0162] When defocus compensation is performed, it is assumed that the focus always remains on the XOY plane.

[0163] S503, Avoidance of laser interference:

[0164] like Figure 3 As shown in Figure 2, when the point of interaction between the laser beam and the material exceeds the Rayleigh length, the laser beam is considered to be a far-field laser composed of a hyperbola.

[0165] In the far-field model, using the asymptotic model, the radius value r at a certain height h in the beam direction is b It can be roughly described as:

[0166]

[0167] in, is the divergence angle of the laser beam; h b is the beam length;

[0168] In the vertical direction, the beam length h b The following geometric relationship is satisfied between it and the height h:

[0169] h b =h / cosα h (13)

[0170] Among them, α h Indicates the angle of rotation of the A-axis when the laser is half blocked;

[0171] The shape profile of the wafer chamfering grinding wheel is described by the following piecewise function (the contour shape of the wafer chamfering grinding wheel can be understood as a combination of straight lines and arcs):

[0172]

[0173] Among them, K s represents the intercept of the hypotenuse, (x r ,y r ) represents the coordinates of the center of the arc, which changes with the arc number; θ represents the angle between the contour line and the horizontal direction; y represents the coordinate system position;

[0174] During the grinding wheel ablation process, the laser tip requires a certain cutting depth. Assuming that the cutting depth is fixed during processing, the actual position of the laser and the grinding wheel will be elevated by the circular effect of the grinding wheel. Therefore, the actual contour of the laser spot should be obtained by deforming the formed contour (in the actual processing process, the laser spot is not in the absolute tangential direction, but has a certain cutting depth. In previous methods, it was believed that the laser interpolation trajectory is the drawing contour trajectory. However, through theoretical calculations, the present invention found that the cutting depth causes the laser spot to be elevated on the grinding wheel surface, causing the removal point trajectory to be deformed relative to the laser interpolation trajectory). The height Δh of the elevated part is obtained by the following geometric relationship:

[0175]

[0176] in R is the radius of the grinding wheel; a represents the depth of laser tip;

[0177] At the height of Ah, the shape profile of the profiled grinding wheel y h Transformed as:

[0178]

[0179] When the laser beam deflection angle (the deflection used in this method, the laser beam deflection center, the A-axis rotation center and the laser beam focal point are coincident, so the angle of rotation is consistent. The laser head is on the A-axis, and the laser beam deflection angle is the angle of rotation of the A-axis) continues to increase, the laser beam will intersect with the outer circle of the grinding wheel, and thus cause the outer circle to block the light of the laser. At this time, the angle a h The following formula is used to calculate:

[0180]

[0181] In the formula, a h represents the angle of rotation of the A-axis when the laser is half blocked. Because empirically, when the laser beam is half blocked, the energy is not enough to continue processing, it is believed that at this time the blocking effect is completely present. Therefore, a can be considered as the position of the center line of the beam participating in the shielding effect. L t represents the width of the groove, D represents the diameter, x l represents the distance from the center of the groove at a certain position, mainly for mathematical calculation of the circular arc part. It can also be changed to x position; y is the y-axis position;

[0182] When the light blocking effect occurs, the corresponding critical angle a2 is described as:

[0183]

[0184] After the laser beam intersects with the outer circle of the grinding wheel, the laser beam cannot penetrate the grinding wheel material to continue to irradiate on the profile surface of the grinding wheel, so the energy of the laser is dispersed to the outer circle surface which should not be processed, and the profile cannot be profiled.

[0185] The critical angle a2 of the grinding wheel light blocking is a series of critical values that change with x. For a point on the profile of the grinding wheel (except the outer circle surface), there is always a critical angle a2 of the laser light blocking, so that when the deflection angle of the laser beam is greater than the critical angle a2, the laser beam is blocked by the outer circle surface of the profiled grinding wheel, and cannot effectively remove the trimming allowance in the profile. Therefore, the non-blocking condition of the laser trimming profiled grinding wheel is: the deflection angle of the laser is less than the critical angle of the point on the profile, that is:

[0186] a(x) < a2(x) (19)

[0187] In the α2 range, the laser power density drops sharply due to the laser being blocked, and the material cannot be removed. Therefore, when profiling the grinding wheel, different deflection angles α need to be used at different contours.

[0188] It can be seen that different laser deflection angles correspond to different positions on the arc of the grinding wheel. In actual processing technology, the deflection resolution M required for processing the arc is calculated using the following formula:

[0189]

[0190] Among them, K CW Is a parameter, take an integer; L g Indicates the length of the secant line of the arc contour, L α is the arc ablation length corresponding to the critical angle of bevel ablation.

[0191] Step 6: After the interpolation motion starts, the monitoring system monitors the machining process and observes the changes in the blank's allowance in real time. Then, through template matching and target recognition, it sends the real-time allowance and grinding wheel blank position information to the CAM system and database;

[0192] The CAM system uses the allowance and blank position information to compensate for abnormal processing points, and the database uses real-time position and allowance to create a digital twin representation;

[0193] Step 7: After the margin meets the processing requirements, the monitoring system sends a message, stops the machine, and performs inspection;

[0194] Step 8: Output the test results. If the product is qualified, the qualified product and test report will be output; if it is unqualified, the grinding wheel information will be re-analyzed and the next round of dressing will be planned;

[0195] Step 9: If the special grinding wheel is difficult to pass after repeated dressing, use the system iteration function to optimize the system database and find more optimized parameters.

Claims

1. An intelligent system for laser dressing of grinding wheels, characterized in that: Including input end, processing system and output end; The input end inputs the grinding wheel data into the processing system according to the product requirements, wherein the grinding wheel data includes the outline requirement parameters and model designed on the drawing, as well as the material information and external dimensions of the grinding wheel blank; The processing system consists of a database, a CAM system and a monitoring system; the database can realize four functions: expert prediction, parameter optimization, digital twin and machine learning; the CAM system receives the processing parameters from the database and performs two functions: laser beam posture adjustment and energy compensation based on the processing parameters; the functions of the monitoring system include judging the allowance of grinding wheel dressing, identifying tool points and judging abnormal situations. On the one hand, the monitoring system feeds back the real-time processing data to the database to help upgrade the database; on the other hand, it interacts with the CAM system, outputs the real-time processing position and allowance information required by the CAM system, and accepts the follow-up control of the CAM system; during the operation of the processing system, it realizes autonomous iteration of the entire process and iteratively upgrades the entire processing system; The output end obtains the products produced by the processing system, including qualified grinding wheels and test reports; Also includes the avoidance of laser interference: When the point of action between the laser beam and the material exceeds the Rayleigh length, the laser beam is considered to be a far-field laser composed of a hyperbola. In the far-field model, the radius r at a certain height h in the direction of the beam is calculated using the asymptotic model. b It can be roughly described as: in, is the divergence angle of the laser beam; h b is the beam length; In the vertical direction, the beam length h b The following geometric relationship is satisfied between it and the height h: h b =h / cosα h (13) Among them, α h Indicates the angle of rotation of the A-axis when the laser is half blocked; The shape profile of the wafer chamfering wheel is described by the following piecewise function: Among them, k s represents the intercept of the hypotenuse, (x r ,y r ) represents the coordinates of the center of the arc, which changes with the arc number; θ represents the angle between the contour line and the horizontal direction; y represents the coordinate system position; During the grinding wheel ablation process, the laser tip requires a certain cutting depth. Assuming that the cutting depth is fixed during processing, the actual position where the laser and the grinding wheel interact will be raised by the circular action of the grinding wheel. The height Δh of the raised part is obtained by the following geometric relationship: in is the radius of the grinding wheel; a represents the cutting depth of the laser tool tip; At a height of Δh, the shape profile y of the forming grinding wheel h Transformed into: When the laser beam deflection angle continues to increase, the laser beam will intersect with the outer circle of the grinding wheel, thereby causing the outer circle to block the laser light. At this time, the angle α h Calculated using the following formula: Where, α h Indicates the angle of rotation of the A axis when the laser is half blocked; L t Indicates the width of the groove, x l Indicates the distance from a certain position to the center of the groove; D is the diameter of the grinding wheel; When the light blocking effect occurs, the corresponding critical angle α2 is described as: For a certain point on the grinding wheel profile, there is always a laser light blocking critical angle α2, so when the laser beam deflection angle is greater than the critical angle α2, the laser is blocked by the outer cylindrical surface of the forming grinding wheel, and the dressing allowance in the forming profile cannot be effectively removed. Therefore, the condition for laser dressing of the forming grinding wheel without light blocking is: the laser deflection angle at a certain point on the profile is less than the light blocking critical angle of the point, that is: α(x)<α2(x) (19) In actual machining technology, the deflection resolution M required for machining an arc is calculated using the following formula: Among them, K CW Is a parameter, take an integer; L g Indicates the length of the secant line of the arc contour, L α is the arc ablation length corresponding to the critical angle of bevel ablation.

2. A method for dressing a grinding wheel using the intelligent grinding wheel laser dressing system according to claim 1, characterized in that: The following steps are involved: Step 1: Input the grinding wheel data into the grinding wheel laser dressing intelligent system through the input end; Step 2: The monitoring system compares and analyzes the outer dimensions of the grinding wheel blank and the contour parameters of the drawing, and then automatically generates the tool setting point and allowance information; Step 3: Compare the material information and dimensions of the grinding wheel blank with the dressing cases stored in the database to find a consistent dressing case. Then, optimize the processing parameters through expert prediction and parameter optimization functions. If there is no consistent dressing case, machine learning is performed on known cases to generate a set of processing parameters. The generated processing parameters are prepared for the digital twin. Step 4: Send the processing parameters generated by the database to the CAM system. The CAM system calculates the laser beam posture adjustment method and laser energy compensation method according to the grinding wheel profile requirements and processing parameters, and generates the trajectory planning of the laser processing process. Step 5: The machine tool performs interpolation motion according to the trajectory plan generated by the CAM system and starts dressing the grinding wheel; Step 6: After the interpolation motion starts, the monitoring system monitors the machining process and observes the changes in the blank's allowance in real time. Then, through template matching and target recognition, it sends the real-time allowance and grinding wheel blank position information to the CAM system and database; Step 7: After the margin meets the processing requirements, the monitoring system sends a message, stops the machine, and performs inspection; Step 8: Output the test results. If the product is qualified, the qualified product and test report will be output; if it is unqualified, the grinding wheel information will be re-analyzed and the next round of dressing will be planned; Step 9: If the grinding wheel is difficult to pass after repeated dressing, use the system iteration function to optimize the system database and find more optimized parameters.

3. The method for intelligent laser dressing of a grinding wheel according to claim 2, wherein: In step 2, the monitoring system automatically generates tool setting points and allowance information according to the following method: For the judgment of grinding wheel blanks: judge the size of the blank machining allowance by visual observation and inspection; For tool point detection: a trial burn method is used, followed by visual observation to determine the position of the molten pool and the laser tool tip; when a mechanical method is used, the tool depth and position are determined through sound sensing and vision; For monitoring of the processing process: determine whether the energy absorption of the processing points is uniform based on the energy of the laser optical spectrometer; compare the actual contour observed by visual observation with the contour required by the drawing, and determine whether the processing is completed based on the difference between the two; determine the circumference roundness, runout, and contour accuracy of the finished product based on visual observation and edge detection synthesis algorithm; determine the operating status of the entire equipment based on sound and current.

4. The method for intelligent laser dressing of a grinding wheel according to claim 2, wherein: In step 3, the particle swarm optimization (PSO) algorithm is used to optimize the machining parameters. The algorithm includes the following steps: S301, using a random method to initialize the position and speed of the particle swarm: including the historical optimal position of a single particle and the historical optimal position of the swarm, the historical optimal fitness value of a single particle and the historical optimal fitness value of the swarm; S302, update the position and velocity of a single particle using formulas (1) and (2): The distance and direction of each particle's next step in the PSO algorithm is a position vector, called the speed of the next iteration, expressed as: in, represents the position vector of particle i in the dth dimension at the k+1th iteration; represents the position vector of particle i in the dth dimension at the kth iteration; represents the velocity vector of the dth dimension of particle i in the k+1th iteration; represents the velocity vector of particle i in the dth dimension at the kth iteration; ω represents the inertia weight; c1 and c2 represent learning factors; r1 and r2 represent two random numbers with a value range of 0 to 1; represents the historical optimal position of particle i in the d-th dimension at the k-th iteration, that is, the optimal solution obtained by the i-th particle in the d-th dimension after the k-th iteration; It represents the historical optimal position of the swarm in the dth dimension at the kth iteration, that is, the optimal solution of the entire particle swarm in the dth dimension after the kth iteration; S303, calculate the fitness value of a single particle. The fitness value must meet the requirements of formula (3): Among them, η m represents the fitness value of each particle; m represents the particle number; S304, updating the historical best fitting value of a single particle; S305, updating the historical best fitting value and position of the group; S306, update the inertia weight and number of iterations: Using the linearly changing inertia weight strategy, the inertia weight is updated as follows (4): Among them, ω max and ω min They represent the maximum inertia weight and the minimum inertia weight respectively; iter represents the current number of iterations; iter max Indicates the maximum number of iterations; S307: When the terminal condition is met, the final optimal solution is output; otherwise, steps S302 to S306 are repeated.

5. The method for intelligent laser dressing of a grinding wheel according to claim 2, wherein: In step 5, the CAM system generates a trajectory plan, including laser interference avoidance, which includes the following steps: S501, trimming parameters are determined: During tangential dressing, the laser spot is irradiated onto the grinding wheel surface in a pulsed manner. The shape of the spot on the grinding wheel surface is considered to be an ellipse. The spot overlap rate in the circumferential direction of the grinding wheel is defined as: the ratio of the area of ​​the overlapping part of the spot to the spot area under two pulses, expressed as Oc, and Oc is described as: Among them, S overlap Indicates the area of ​​the overlapping part of the light spot; S ellipse Indicates the spot area; a e and b e Indicates the parameters of the ellipse; l c Indicates the offset of the center of the light spot in the circumferential direction; The grinding wheel speed when the spot overlap rate reaches 85% is given by formula (6): Where T represents the pulse period of the laser, which is the inverse of the repetition frequency; The light spot overlap rate in the direction of the grinding wheel generatrix is ​​defined as the ratio of the area of ​​the light spot overlap to the area of ​​the light spot, expressed as O A Indicates that O A Described as: Among them, l A is the offset of the center of the light spot on the busbar; Then, at the rotation speed n, the grinding wheel feed rate F is calculated by formula (8): F=nl A (8) The trimming parameters can be determined by formula (5) to formula (8); S502, defocus compensation: The edge of the grinding wheel is taken as the origin of the coordinates, the generatrix direction of the grinding wheel cylinder is taken as the X direction, and the diameter direction is taken as the Y direction and the Z direction. Before the grinding wheel is dressed, its surface cylindrical annulus is described as: Where x, y, and z are the three directions after the coordinate system is established, and the origin of the coordinate is at the edge of the grinding wheel; B is the thickness of the grinding wheel; During the material removal process, the vertically irradiated laser beam needs to rotate in the XOZ plane with the laser beam focus O as the rotation center. The state of rotation angle α is described as: Where r represents the radius of the laser beam at a certain position; h represents the distance from the position to the laser focus; r0 represents the radius of the spot at the laser focus; L ray represents the Rayleigh length of the laser beam, e0 is the initial defocus of the laser beam in the vertical state; For vertically irradiated laser, the focus is on the XOY plane. As the laser beam rotates, the intersection point P of the laser beam and the grinding wheel T To maintain a stable defocus, compensation needs to be made in the X and Z directions. The compensation amount is: When performing defocus compensation, it is assumed that the focus is always maintained on the XOY plane.

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