A shear thickening polishing method based on trajectory point and dwell time optimization

Abstract

The invention discloses a shear thickening polishing method based on trajectory point and dwell time optimization, setting polishing process parameters based on a shear thickening polishing device; constructing a spatial material removal footprint prediction model for shear thickening polishing, the prediction model including an influence region size equation and a material removal amount equation; measuring the surface morphology of a workpiece to be processed to obtain a measurement point matrix, and using a trajectory point generation algorithm to obtain all trajectory points in the polishing region; using the prediction model to calculate the influence region size of each trajectory point, with the goal of adjacent trajectory points being connected and not interfering, optimizing to obtain a trajectory point feed matrix; iterating the dwell time for each trajectory point to obtain a dwell time matrix; using the trajectory point feed matrix and the dwell time matrix on the shear thickening polishing device to polish the workpiece to be processed. The invention optimizes the trajectory point and dwell time matrix, and improves polishing accuracy, quality and efficiency.

Description

Technical Field

[0001] The invention relates to the field of shear thickening polishing, and in particular to a shear thickening polishing method based on trajectory point and residence time optimization. Background Art

[0002] Shear thickening polishing is a non-contact polishing method. Compared with contact polishing methods such as polishing discs and air bags, its unique processing technology makes the surface of high-precision instruments avoid surface and sub-surface damage to a great extent. Among non-contact polishing methods, shear thickening polishing has been widely used due to its low cost and environmental friendliness. In the process of selecting and adjusting polishing parameters, shear thickening polishing cannot have a certain contact polishing area like contact polishing methods, but exists in a non-contact polishing area within a certain influence range. This influence area leads to local excessive or insufficient material removal on the workpiece surface due to unreasonable adjustment of polishing parameters during shear thickening polishing. Although operators adjust different polishing parameters based on experience, it still consumes a lot of resources and time when facing workpieces with different surface morphologies and different sizes, and it is impossible to guarantee the optimal polishing parameters. The most important basis for adjusting the shear thickening polishing parameters is the size of the influence area. After revealing this size, a complete shear thickening polishing parameter optimization strategy can be established, thereby accelerating the efficiency of finding the optimal polishing parameters and improving the processing quality of the workpiece. Summary of the invention

[0003] In view of the deficiencies of the prior art, the present invention proposes a shear thickening polishing method based on trajectory point and residence time optimization.

[0004] The specific technical solutions are as follows:

[0005] A shear thickening polishing method based on trajectory point and dwell time optimization comprises the following steps:

[0006] S1: Based on the world coordinate system, set the polishing process parameters based on the shear thickening polishing device, including: the velocity component U of the polishing tool in the x direction s , shear layer thickness h0, polishing inclination angle α; the shear layer thickness is the shortest distance from the polishing tool head to the surface of the workpiece to be processed;

[0007] S2: Construct a spatial material removal footprint prediction model for shear thickening polishing, which includes the influence zone size equation and the material removal amount equation;

[0008] S3: measuring the surface morphology of the workpiece to be processed, obtaining a measurement point matrix, and using a trajectory point generation algorithm to obtain all trajectory points in the polishing area;

[0009] S4: using the prediction model to calculate the size of the influence area of ​​each trajectory point obtained in S3, with the goal of connecting adjacent trajectory points without interference, optimizing the x and y coordinate values ​​of the trajectory points, adjusting the z coordinate value of the trajectory points with a cubic spline curve based on the adjusted x and y coordinate values ​​and the measurement point matrix, and then sorting them according to the feed route to obtain the trajectory point feed matrix;

[0010] S5: Calculate the amount of material to be removed H at each trajectory point according to the measurement point matrix and the trajectory point feed matrix, combined with the target surface function. alw ; Perform dwell time iteration for each trajectory point, calculate the iteration height DH during each iteration, and the relationship between DH and H alw If DE is less than or equal to the expected error, the next trajectory point is iterated until all trajectory points are traversed and the residence time matrix is ​​output; otherwise, it is determined whether DH is less than H alw If not, it is updated to a smaller iteration step, and the current trajectory point residence time minus the updated iteration step to start the next iteration. If so, the current trajectory point residence time increases the original iteration step to start the next iteration.

[0011] S6: Polishing the workpiece using the trajectory point feed matrix and the dwell time matrix on the shear thickening polishing device.

[0012] Furthermore, the prediction model is expressed as follows:

[0013] ;

[0014] ;

[0015] ;

[0016] In the formula, S represents the size of the affected area, is the viscosity index, x0 is the boundary value of the affected area in the x direction; H material is the material removal amount, mrr is the material removal function, T dwell is the residence time; k is the Preston coefficient, P d is the instantaneous load between the polishing liquid and the workpiece surface, u s is the instantaneous relative velocity of the polishing liquid flowing over the workpiece surface; K is the consistency coefficient, and h(x) represents the distance function from each point on the surface of the tool head immersed in the polishing liquid to the surface of the workpiece to be processed.

[0017] Furthermore, in S4, the trajectory points in the impact area are optimized with the goal of connecting adjacent trajectory points without interference, specifically: taking the first trajectory point as the reference point, traversing all trajectory points in order starting from the current trajectory point, judging whether the current trajectory point meets the screening condition, the screening condition is that the x value of the current trajectory point is less than or equal to the x value of the previous trajectory point, if so, the current trajectory point is screened out, and the x value of the next trajectory point is continuously judged until the screening condition is not met; at this time, the influence area radii of the current trajectory point and the previous trajectory point are calculated, and a trajectory point adjustment formula is constructed to obtain an offset in the x direction, which is used to update the x coordinate of the current trajectory point.

[0018] Furthermore, for the trajectory point matrix H with m rows and n columns pp , the trajectory point adjustment formula is as follows:

[0019] ;

[0020] Where i represents the row where the trajectory point is located, i=1,2,3,…,m, j represents the column where the trajectory point is located, j=1,2,3,…,n; c is the jump parameter, c=1,2,3,…,j-1; Indicates the current track point The radius of the affected area, Indicates the previous trajectory point The radius of the affected area; β is the angle between the normal vector of the trajectory point and the z direction, is the offset of the trajectory point in the x direction, Indicates H pp The value of (i,j) in the x direction, Indicates H pp The value of (i,jc) in the x direction.

[0021] Furthermore, S5 is specifically implemented through the following sub-steps:

[0022] (5.1) According to the x coordinates in the measurement point matrix and the trajectory point feed matrix and the y coordinate , fitting the z value of each x and y coordinate on the surface morphology of the workpiece to be processed, recorded as , u=1,2,3,…,l, l is the total number of trajectory points after optimization; combined with the target surface function z m =G(x,y) calculates the amount of material to be removed at each trajectory point H alw (u), the expression is as follows:

[0023] ;

[0024] At the same time, set the initial iteration parameters and initialize the number of iterations d i=1; the initial iteration parameters include: expected error E, initial iteration step length Δl, initial dwell time matrix; among which the expected error and initial iteration step length are set manually;

[0025] (5.2) Traverse all trajectory points one by one, perform iterative calculation of the residence time for the current trajectory point, and calculate the iteration height DH (d i ), number of iterations d i =1,2,3,…, and the residual error DE(d i ), the expression is as follows:

[0026] ;

[0027] ;

[0028] Where mrr is the material removal function, is the dth point of the current trajectory i The dwell time at the iteration;

[0029] (5.3) Determine the current residual error DE(d i ) is greater than the given expected error E, if so, execute step (5.4), if not, execute step (5.5);

[0030] (5.4) Determine the current iteration height DH (d i ) is less than the corresponding amount of material to be removed H alw (u), if not, set a smaller iteration step size , the dwell time of the corresponding trajectory point minus one iteration step , the number of iterations increases by 1, and returns to step (5.2); if so, the residence time of the corresponding trajectory point is increased by an iteration step length Δl, the number of iterations increases by 1, and returns to step (5.2);

[0031] (5.5) Determine whether all trajectory points have been traversed. If not, reset the number of iterations d i =1, iterate the calculation for the next trajectory point and repeat steps (5.2)-(5.3); if yes, end the iteration process and output the updated residence time matrix.

[0032] Furthermore, in S3, all trajectory points in the polishing area are obtained using a trajectory point generation algorithm, and the specific operations are as follows:

[0033] Generate the x and y coordinates of the trajectory point according to the trajectory generation function, take the maximum z value in the measurement point matrix as the calibration value, and add the calibration value to the shear layer thickness h0 to obtain the distance from the trajectory point to the workpiece surface. ,Will Add the normal vector direction of each trajectory point to the target surface function z m =G(x,y), we get , Refers to the superposition of the normal vector direction of each trajectory point The projection length in the z direction; substitute the x and y coordinates of the trajectory point into the formula to obtain the z coordinate of the trajectory point, integrate the x, y, and z coordinates of all trajectory points to obtain the trajectory point matrix, adjust the x and y coordinate values ​​according to the actual size of the polishing area, and complete the coordinate conversion.

[0034] Furthermore, in S3, a GPI XP / D laser interferometer is used to measure the surface morphology of the workpiece to be processed to obtain a measurement point matrix.

[0035] Further, the shear thickening polishing device comprises: a polishing liquid circulation component, a six-degree-of-freedom ultra-precision machining robot arm, a high-speed electric spindle, a spindle fixture, an angle measuring instrument, a polishing tool, a flexible horizontal calibration component, an optical platform, and a control terminal;

[0036] The high-speed electric spindle is fixed to the end joint of the six-degree-of-freedom ultra-precision machining robot arm through a spindle clamp, the polishing tool is coaxially fixed to the high-speed electric spindle, and the polishing tool moves to a specified position under the action of the six-degree-of-freedom ultra-precision machining robot arm; an angle measuring instrument is arranged on the high-speed electric spindle for real-time measurement of the normal angle between the high-speed electric spindle and the workpiece to be processed; the polishing pool is fixed on the optical platform, the workpiece to be processed is fixed in the polishing pool, and the flexible horizontal calibration component is controlled by the control end to keep the workpiece to be processed in a horizontal state; the polishing pool is filled with polishing liquid, and the polishing liquid circulation component is used to keep the polishing liquid in the polishing pool circulating; the control end is used to control the circulation flow rate of the polishing liquid circulation component, the rotation speed of the high-speed electric spindle, and the trajectory point feed matrix and the residence time matrix obtained according to S6 to control the operation of the six-degree-of-freedom ultra-precision machining robot arm.

[0037] Furthermore, the polishing liquid circulation component includes: a high-viscosity rotor pump, a polishing pool, a bamboo tube, and a splash shield; the bottom outlet of the polishing pool is connected to the inlet end of the high-viscosity rotor pump through a pipeline, the bamboo tube is fixed above the polishing pool through a spindle clamp, and its inlet end is connected to the outlet end of the high-viscosity rotor pump through a pipeline, and the outlet end is located above the polishing pool, and the control end adjusts the polishing liquid flow rate at the bamboo tube outlet by controlling the rotational speed of the high-viscosity rotor pump; the splash shield is fixed to the top of the polishing pool to prevent the polishing liquid from splashing outside the working area.

[0038] Furthermore, the flexible horizontal calibration component includes: a workpiece chuck, a micro cylinder, a compressed air machine, a pressure regulating valve, and a spirit level; the workpiece chuck is arranged in a polishing pool, one end of the four micro cylinders are respectively fixed to the four corners of the lower surface of the workpiece chuck, and the other ends are respectively fixed to the bottom of the polishing pool; the four micro cylinders are respectively connected to the outlet end of the compressed air machine through pipelines, and a pressure regulating valve is provided on the connecting pipeline. The control end coordinates the lifting height of the micro cylinder by controlling the output pressure of the compressed air machine and the opening of the pressure regulating valve to keep the workpiece chuck level; the workpiece to be processed is installed on the upper surface of the workpiece chuck, and the spirit level is arranged around the workpiece to be processed for feedback on the horizontality of the workpiece to be processed.

[0039] The beneficial effects of the present invention are:

[0040] Compared with the traditional experimental adjustment method, the present invention realizes automatic optimization of polishing trajectory points by constructing a spatial material removal footprint prediction model. It does not require tedious experimental verification, overcomes the limitations of traditional polishing trajectory points and dwell time adjustment, and can efficiently optimize any polishing parameters to improve the surface quality of workpieces. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the structure of the shear thickening polishing device in an embodiment of the present invention.

[0042] Figure 2 Schematic diagram of the structure of the polishing head of the shear thickening polishing device in the embodiment of the present invention.

[0043] Figure 3 Schematic diagram of the structure of the polishing liquid circulation component of the shear thickening polishing device in the embodiment of the present invention.

[0044] Figure 4 Schematic diagram of the structure of the flexible horizontal calibration component of the shear thickening polishing device in an embodiment of the present invention.

[0045] Figure 5 It is a flow chart of a shear thickening polishing method based on trajectory point and dwell time optimization proposed in an embodiment of the present invention.

[0046] Figure 6 It is a flow chart of the trajectory point optimization strategy performed in S4 in an embodiment of the present invention.

[0047] Figure 7 4 is a flow chart of iterative optimization of residence time in S5 in an embodiment of the present invention.

[0048] Figure 8 3 is a comparison diagram of the surface morphology obtained by polishing along the trajectory before and after optimization in an embodiment of the present invention, wherein (a) is a schematic diagram of the surface morphology obtained by polishing along the trajectory before optimization, and (b) is a schematic diagram of the surface morphology obtained by polishing along the trajectory after optimization.

[0049] Fig. 9 Schematic diagram of the surface roughness of the workpiece obtained by polishing along the trajectory before and after optimization in an embodiment of the present invention, wherein (a) is before optimization and (b) is after optimization.

[0050] In the figure, there are polishing liquid circulation components 1, high-viscosity rotor pump 1-1, polishing pool 1-2, bamboo tube 1-3, splash shield 1-4; six-degree-of-freedom ultra-precision machining robot 2, high-speed electric spindle 3, spindle fixture 4, angle measuring instrument 5, polishing device 6, tool head 6-1, coaxial positioning device 6-2; flexible horizontal calibration component 7, workpiece chuck 7-1, micro cylinder 7-2, compressed air machine 7-3, pressure regulating valve 7-4, level 7-5; optical platform 8, control end 9. DETAILED DESCRIPTION

[0051] The present invention will be described in detail below according to the accompanying drawings and preferred embodiments, and the purpose and effect of the present invention will become more clear. The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0052] like Figure 1 As shown, the embodiment of the present invention proposes a shear thickening polishing device, including: a polishing liquid circulation component 1, a six-degree-of-freedom ultra-precision machining robot 2, a high-speed electric spindle 3, a spindle fixture 4, an angle measuring instrument 5, a polishing tool 6, a flexible horizontal calibration component 7, an optical platform 8, and a control terminal 9. The high-speed electric spindle 3 is fixed to the end joint of the six-degree-of-freedom ultra-precision machining robot 2 through the spindle fixture 4, and the high-speed electric spindle 3 and the spindle fixture 4 are fixedly connected by positioning pins and threads, and the spindle fixture 4 is rigidly connected to the end joint of the six-degree-of-freedom ultra-precision machining robot 2. The high-speed electric spindle 3 and the polishing tool 6 are coaxially fixed, and the six-degree-of-freedom ultra-precision machining robot 2 is fixed on a flat ground by anchor bolts, which is used to move the polishing tool 6 to a specified position, and its repeated positioning error is 0.025mm. An angle measuring instrument 5 is arranged on the high-speed electric spindle 3, which is used to measure the normal angle between the high-speed electric spindle 3 and the workpiece to be processed in real time. The angle measuring instrument 5 can measure the swing angle in the range of 0~90°, and the measurement accuracy is 0.01°. The polishing liquid circulation component 1 is used to maintain the fluidity of the polishing liquid so that the abrasive particles in the polishing liquid are evenly distributed, and the flexible horizontal calibration component 7 is used to keep the workpiece to be processed in a horizontal state. The shear thickening polishing device adopts a world coordinate system, where x and y are horizontal directions and z is vertical direction.

[0053] like Figure 2As shown, the polishing tool 6 includes a tool head 6-1 and a coaxial positioning device 6-2. Among them, the tool head 6-1 is a toothed rotary file structure (that is, a plurality of axially inwardly rotating micro grooves are provided at the working end, and the groove depth is 0.5mm), and its protruding column is inserted into the cylindrical blind hole provided at one end of the coaxial positioning device, and is fixedly connected by interference fit; the other end of the coaxial positioning device 6-2 is fixedly connected to the high-speed electric spindle 3, so that the tool head 6-1 and the high-speed electric spindle 3 always remain coaxial, so as to reduce the processing error and realize synchronous rotation. The tool head 6-1 drives the polishing liquid to produce shear thickening phenomenon through the rotation of the high-speed electric spindle 3, so that a 1mm thick flexible abrasive is formed on the surface of the tool head 6-1, and the material on the surface of the workpiece to be processed is removed by the flexible abrasive, thereby realizing ultra-precision processing of the surface of the workpiece to be processed, obtaining a smooth surface morphology, and improving the performance of the workpiece. The control terminal 9 controls the rotation speed of the high-speed electric spindle 3, thereby controlling the rotation speed of the tool head 6-1; the high-speed electric spindle 3 can infinitely adjust the rotation speed within the range of 1000-9000 rpm, which is suitable for flexible selection of processing parameters.

[0054] like Figure 3 As shown, the polishing liquid circulation assembly 1 includes: a high-viscosity rotor pump 1-1, a polishing pool 1-2, a bamboo tube 1-3, and a splash shield 1-4. The optical platform 8 is fixed on the flat ground, the polishing pool 1-2 is fixed on the optical platform 8, the bottom outlet of the polishing pool 1-2 is connected to the inlet end of the high-viscosity rotor pump 1-1 through a pipeline, the high-viscosity rotor pump 1-1 is fixed on the horizontal ground through anchor bolts, the bamboo tube 1-3 is fixed above the polishing pool 1-2 through the spindle clamp 4, and its inlet end is connected to the outlet end of the high-viscosity rotor pump 1-1 through a pipeline, and the outlet end is located above the polishing pool 1-2. The control end 9 adjusts the polishing liquid flow rate at the outlet of the bamboo tube 1-3 by controlling the rotation speed of the high-viscosity rotor pump 1-1 (the range is 0~500rpm, and the adjustment accuracy is 0.01rpm). The splash shield 1-4 is threadedly connected to the top of the polishing pool 1-2 to prevent the polishing liquid from splashing outside the working area.

[0055] like Figure 4As shown, the flexible level calibration assembly 7 includes: a workpiece chuck 7-1, a micro cylinder 7-2, a compressed air machine 7-3, a pressure regulating valve 7-4, and a level 7-5. The workpiece chuck 7-1 is arranged in the polishing pool 1-1, one end of the four micro cylinders 7-2 is respectively fixed to the four corners of the lower surface of the workpiece chuck 7-1, and the other ends are respectively fixed to the bottom of the polishing pool 1-1, and the adjustment accuracy of the micro cylinder 7-2 is 0.2mm. The compressed air machine 7-3 is fixed on the ground, and the four micro cylinders 7-2 are connected to the outlet end of the compressed air machine 7-3 through pipelines. The connecting pipeline is provided with a pressure regulating valve 7-4. The control end 9 coordinates the lifting height of the micro cylinder 7-2 by controlling the output pressure of the compressed air machine 7-3 and the opening of the pressure regulating valve 7-4, so as to keep the workpiece chuck 7-1 horizontal; the adjustment range of the pressure regulating valve 7-4 is 0.005~0.2MPa, the sensitivity is 0.2%FS, and the maximum pressure value output by the compressed air machine 7-3 is 0.7MPa. The workpiece to be processed is installed at the center of the upper surface of the workpiece chuck 7-1, and the level 7-5 is also placed on the upper surface of the workpiece chuck 7-1 to feedback the horizontality of the workpiece to be processed. It should be noted that the level 7-5 is only used in the process of leveling the workpiece to be processed. After leveling, the level 7-5 is moved outside the optical platform 8.

[0056] The present invention designs a high-speed rotating tool head 6-1 with a micro-groove structure, cooperates with a shear thickening polishing liquid and a polishing liquid circulation component 1, can effectively remove the surface material of the workpiece, avoid the shortcomings of traditional polishing methods, such as sub-surface damage in contact polishing and low efficiency in jet polishing, and is also equipped with a flexible horizontal calibration component 7 to further reduce processing errors.

[0057] Based on the shear thickening polishing device, the embodiment of the present invention also proposes a shear thickening polishing method based on trajectory point and dwell time optimization, such as Figure 5 As shown, the method specifically comprises the following steps:

[0058] S1: Setting polishing process parameters, which include: velocity component of polishing tool 6 in x direction, shear layer thickness, polishing inclination angle. Shear layer thickness is the shortest distance from tool head 6-1 to the surface of the workpiece to be processed. When setting the polishing process parameters, it is necessary to satisfy the optimization range of polishing process parameters established according to elastic-plastic-brittle deformation theory, that is, to calculate the critical pressure values ​​from elasticity to plasticity and from plasticity to brittleness using Hertz contact theory and indentation experiment principle, and obtain a reasonable polishing process parameter adjustment range, which is expressed as follows:

[0059]

[0060]

[0061] Where P E-Pis the critical pressure value from elasticity to plasticity, P P-B is the critical pressure value from plasticity to brittleness, α is the polishing inclination angle, E r is the composite elastic modulus of the abrasive and the workpiece surface, E w is the effective Young's modulus of the workpiece material, K * is the elastic mismatch coefficient, H w is the workpiece hardness, R abrasive is the abrasive particle radius, K w is the fracture toughness of the workpiece, E a is the effective Young’s modulus of the abrasive.

[0062] The instantaneous load P between the polishing fluid and the workpiece surface in the area affected by shear thickening polishing according to the polishing process parameters d To calculate, the expression is as follows:

[0063]

[0064] Where K is the consistency coefficient, U s is the velocity component of the polishing tool in the x direction, is the viscosity index, h0 is the shear layer thickness, x0 is the boundary value of the affected area in the x direction, and h(x) represents the distance function from each point on the surface of the tool head 6-1 immersed in the polishing liquid to the surface of the workpiece to be processed.

[0065] S2: Construct a spatial material removal footprint prediction model for shear thickening polishing, which includes the influence zone size equation and the material removal amount equation. The influence zone size equation reveals the relationship between polishing process parameters and the influence zone size, providing a theoretical basis for accurate prediction and polishing trajectory optimization.

[0066] The expression of the influence area size equation is as follows:

[0067]

[0068] Where S represents the size of the affected area.

[0069] The material removal equation is expressed as follows:

[0070]

[0071] In the formula, H material is the material removal amount, k is the Preston coefficient, P d is the instantaneous load between the polishing liquid and the workpiece surface, u s is the instantaneous relative velocity of the polishing fluid flowing over the workpiece surface, T dwell is the dwell time and mrr is the material removal function.

[0072] After obtaining the material removal amount, the distributed material removal amount is calculated for each position within the affected area according to the Gaussian distribution function, so as to establish a spatial material removal footprint prediction model for shear thickening polishing, and the polishing result with set polishing process parameters is obtained using the prediction model.

[0073] S3: Clamp the workpiece to be processed into the workpiece chuck 7-1, place the level 7-5 on the upper surface of the workpiece chuck 7-1, and control the compressed air machine 7-3 and the pressure regulating valve 7-4 to adjust the height of the four micro cylinders 7-2 to make the workpiece to be processed in a horizontal state. Use the six-degree-of-freedom ultra-precision machining robot 2 to move the polishing tool 6-1 above the workpiece to be processed, use high-precision measuring equipment to measure the surface morphology of the workpiece to be processed, obtain the measurement point matrix, and use the existing trajectory point generation algorithm to obtain all trajectory points in the polishing area.

[0074] Specifically, the rotation speed of the tool head 6-1 is set, and the x and y coordinates of the trajectory points are generated according to the trajectory generation function (such as grating trajectory, spiral trajectory, fractal curve trajectory, etc.), and the maximum value of z in the measurement point matrix is ​​taken as the calibration value, and the calibration value is added to the shear layer thickness h0 to obtain the distance from the trajectory point to the workpiece surface. ,Will Add the normal vector direction of each trajectory point to the target surface function z m =G(x,y), we get , Refers to the superposition of the normal vector direction of each trajectory point The projection length in the z direction; Substitute the x and y coordinates of the trajectory point into Thus, the z coordinate of the trajectory point is obtained, and the x, y, and z coordinates of all trajectory points are integrated to obtain the trajectory point matrix. Finally, the x and y coordinate values ​​are adjusted according to the size of the actual polishing area to complete the coordinate conversion.

[0075] High-precision measuring equipment refers to the GPI XP / D laser interferometer, which can measure the surface topography of high-precision optical components and generate a measurement point matrix.

[0076] S4: In order to eliminate the interference of the influence area between the polishing trajectory points obtained in S3, the prediction model constructed in S2 is used to calculate the influence area size of each polishing trajectory point obtained in S3, and the polishing trajectory points are optimized according to the interference of the influence areas of adjacent polishing trajectory points to obtain reasonably distributed polishing trajectory points. Figure 6 As shown, the trajectory point matrix H with m rows and n columns is optimized row by row pp Taking the x value in as an example, the specific steps of the trajectory point optimization strategy are as follows:

[0077] (4.1) Select trajectory points As the reference point of the optimization trajectory, the optimization starts from the reference point and the current trajectory point is , i=1,2,3,…,m, j=1,2,3,…,n; initialize i=1,j=1, i,j represent the row and column of the current trajectory point in the optimization process respectively.

[0078] (4.2) For the current trajectory point During optimization, the jump parameter c is initialized to 1. When the jump parameter c is greater than 1, it means that the x value of the previous trajectory point exceeds the trajectory point to be optimized. The x value is less than or equal to the previous trajectory point If the x value is less than , it means that the trajectory point is unnecessary and should be deleted. , to improve processing efficiency; at the same time, jump parameter c=c+1, and judge the x value of the next trajectory point, that is, j=j+1, until The x value is greater than The x value of .

[0079] like The x value is greater than The x value is calculated The radius of the affected area and The radius of the affected area Specifically, the shape of the affected area in shear thickening polishing is approximately circular, so the radius of the affected area can be calculated based on the affected area size equation in S2: .

[0080] (4.3) We get and Then establish the trajectory point adjustment formula to get the offset of the trajectory point :

[0081]

[0082] Where c=1,2,3,…,j-1, β is the angle between the normal vector of the trajectory point and the z direction, is the offset of the trajectory point in the x direction, Indicates H pp The value of (i,j) in the x direction, Indicates H pp The value of (i,jc) in the x direction.

[0083] (4.4) Update the x coordinate of the current trajectory point, that is, Add to track point The x value of .

[0084] (4.5) Determine whether all trajectory points in the i-th row have been traversed. If so, execute the next step; if not, take j=j+1 and repeat steps (4.2)-(4.4).

[0085] (4.6) Determine whether all rows have been traversed. If not, take i=i+1 and repeat steps (4.2)-(4.5). Otherwise, it is considered that the optimization of the entire trajectory point matrix has been completed and proceed to the next step.

[0086] (4.7) Based on the adjusted x, y coordinate values ​​of the trajectory points and the measurement point matrix, the z value of the trajectory points is adjusted using a cubic spline curve.

[0087] (4.8) Sort the optimized trajectory point matrix according to the feed route and obtain The trajectory point feed matrix , l is the total number of trajectory points after optimization.

[0088] The trajectory point optimization strategy adopted by the present invention is evaluated using surface roughness and surface topography quality.

[0089] Specifically, the Veeco Wyko NT9100 optical profiler is used to measure and compare the surface roughness of the workpiece before and after the polishing process parameters are optimized (here specifically referring to the trajectory point optimization); if the surface roughness after optimization is lower than that before optimization, it means that the optimization effect of the polishing process parameters is good.

[0090] The GPI XP / D laser interferometer is used to measure and compare the surface morphology of the workpiece before and after the optimization of the polishing process parameters (specifically the trajectory point optimization); if the peak and valley values ​​after optimization are lower than those before optimization, it means that the optimization effect of the polishing process parameters is good. The calculation expression of the peak and valley value Rt is as follows:

[0091]

[0092] In the formula, Represents the surface profile deviation matrix of all measurement points, Rt is The difference between the maximum and minimum values ​​of .

[0093] S5: In order to improve the computational efficiency of deterministic polishing, an iterative method is used to calculate the dwell time of the polishing trajectory points to obtain a high-precision dwell time matrix. Figure 7 As shown in Figure 1, the dwell time iterative optimization is implemented through the following sub-steps:

[0094] (5.1) According to the measurement point matrix and trajectory point feed matrix The x coordinate in and the y coordinate , fitting the z value of each x and y coordinate on the surface morphology of the workpiece to be processed, recorded as . Combined with the target surface function z m =G(x,y) calculates the actual amount of material to be removed H at each trajectory point alw (u), calculated as follows:

[0095]

[0096] At the same time, the initial iteration parameters are set and the number of iterations is initialized to 1; the initial iteration parameters include: expected error E (the same for each iteration), initial iteration step size Δl, initial residence time matrix T dwell Among them, the expected error and the initial iteration step are set manually, which are determined according to the actual required calculation accuracy and calculation efficiency.

[0097] (5.2) Traverse all trajectory points one by one, perform iterative calculation of the residence time for the current trajectory point, and calculate the iteration height during this iteration , and the residual error between the iteration height and the amount of material to be removed , the expression is as follows:

[0098]

[0099]

[0100] In the formula, is the material removal function, is the dth point of the current trajectory i The dwell time at iteration.

[0101] (5.3) Determine the current residual error Is it greater than the given expected error? If yes, go to step (5.4); if no, go to step (5.5).

[0102] (5.4) Determine the current iteration height Is it less than the corresponding amount of material to be removed H? alw (u), if not, set a smaller iteration step size , the dwell time of the corresponding trajectory point minus one iteration step , the number of iterations increases by 1, and returns to step (5.2); if so, the residence time of the corresponding trajectory point increases by one iteration step , the number of iterations is increased by 1, and the process returns to step (5.2), thereby achieving dynamic change of the iteration step size.

[0103] (5.5) Determine whether all trajectory points have been traversed. If not, reset the number of iterations d i=1, iteratively calculate the next trajectory point and repeat steps (5.2)-(5.3); if so, it means that the residual height of all polishing points meets the given expected error , end the iteration process and output the updated residence time matrix.

[0104] S6: Using the trajectory point feed matrix and the dwell time matrix, the optimized results are used on the shear thickening polishing device to perform ultra-precision polishing on the workpiece. The specific polishing process is as follows:

[0105] (6.1) Prepare the polishing liquid in the proportion required by the polishing process, and pour the polishing liquid into the polishing pool 1-2, and connect the splash shield 1-4 to the top of the polishing pool 1-2; start the polishing liquid circulation system 1 and the high-speed electric spindle 3, and the control end 9 controls the rotation speed of the high-viscosity rotor pump 1-1, thereby controlling the flow rate of the polishing liquid; the control end 9 controls the high-speed electric spindle 3 to make the high-speed electric spindle 3 rotate at a fixed speed set manually.

[0106] (6.2) Execute the optimized trajectory point matrix and dwell time matrix stored in the six-degree-of-freedom ultra-precision machining robot 2 to complete deterministic material removal within the specified area.

[0107] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described are only used to explain the present invention and are not used to limit the present invention.

[0108] First, the initial polishing process parameters were set: polishing inclination angle α = 45°, shear layer thickness h0 = 0.2 mm, polishing tool head speed 3000 rpm. A shear thickening polishing fluid of a certain concentration was prepared, and the composition of the shear thickening polishing fluid is shown in Table 1.

[0109] Table 1 Shear thickening polishing fluid composition parameters

[0110]

[0111] After setting the polishing process parameters, the initial surface shape within the specified polishing area is measured, the workpiece to be processed is clamped using the workpiece chuck 7-1 with a repeatable positioning function, and the surface morphology of the workpiece to be processed is scanned using the GPI XP / D laser interferometer to obtain a measurement point matrix. The z value of the polishing trajectory is determined based on the maximum value of the z direction of the measurement point and the shear layer thickness h0. Taking the typical fifth-order Hilbert curve trajectory as an example, the Hilbert curve equation is used to calculate the x and y coordinates of the polishing trajectory points.

[0112] The spatial material removal footprint prediction model is used to calculate the size of the affected area and the material removal depth, and the polishing results of the specified polishing parameters are obtained. The size of the affected area is used as an indicator for optimizing the polishing trajectory points. The x and y coordinates of the trajectory points are adjusted using the S4 method to obtain the optimized trajectory points in the polishing area. Since the evaluation method is only used in the initial iterative parameter adjustment process, the initial iterative step size and expected error are no longer adjusted in the actual processing process. Therefore, it is only necessary to calculate the dwell time of each polishing position based on the optimized trajectory points. Table 2 compares the calculation efficiency and calculation accuracy of different iterative parameters.

[0113] Table 2 Comparison of calculation efficiency and accuracy of different iteration parameters

[0114]

[0115] As shown in Table 2, under the same iteration step size, as the expected error increases, the average calculation error will also increase, but most polishing points can converge. However, under a given expected error, as the iteration step size increases, all polishing points have different degrees of divergence. Therefore, the parameters used for iterative calculation in practice can be inferred. In this embodiment, the iteration step size is controlled at 0.0001s and the expected error is controlled at 0.0001nm, which can achieve high-precision and high-efficiency residence time calculation.

[0116] Use the workpiece chuck 7-1 to clamp the workpiece, and install the workpiece chuck 7-1 on the micro cylinder 7-2. After adjusting the pressure regulating valve 7-4 to make the workpiece level, install the splash guard 1-4 and start the polishing liquid circulation system 1.

[0117] After obtaining the trajectory point coordinates and dwell time, they are integrated into trajectory point codes and saved in the six-degree-of-freedom ultra-precision machining robot 2. The trajectory point code file is executed to complete the deterministic polishing in the specified polishing area. In order to highlight the influence of the trajectory point optimization method on the surface morphology of the workpiece before and after, Figure 8 The results of polishing along the trajectory before and after optimization using the same polishing parameters (shear layer thickness 0.2mm, polishing angle 45°, rotation speed 3000rpm) are compared. By comparison, it can be found that before the optimization of the trajectory points, the dense distribution of the trajectory points caused interference in the affected areas, resulting in excessive material removal in the polishing area. After the optimization of the trajectory points, the interference problem in the affected areas was solved, making the surface morphology of the polishing area smooth. In addition, in this embodiment, the Veeco Wyko NT9100 optical profiler was used to scan the surface morphology before and after polishing, and the following results were obtained: Fig. 9 Surface data shown. Fig. 9(a) is the surface morphology data obtained by polishing using the trajectory before optimization. The Ra value before polishing is 7.15nm, the Rq value is 8.76nm, and the Rt value is 70.72nm. The Ra value after polishing is 7.45nm, the Rq value is 9.34nm, and the Rt value is 68.56nm. Fig. 9 (b) is the surface morphology data obtained by polishing with the optimized trajectory. The Ra value before polishing is 12.26nm, the Rq value is 15.49nm, and the Rt value is 135.49nm. The Ra value after polishing is 5.22nm, the Rq value is 6.62nm, and the Rt value is 49.15nm. From the perspective of surface roughness, the optimized trajectory makes the surface morphology of the workpiece smoother, thereby significantly reducing the surface roughness. The trajectory before optimization causes excessive or insufficient material removal on the workpiece surface, which increases the surface roughness instead of decreasing it.

[0118] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A shear thickening polishing method based on trajectory point and residence time optimization, characterized in that: The following steps are involved: S1: Based on the world coordinate system, set the polishing process parameters based on the shear thickening polishing device, including: the velocity component U of the polishing tool in the x direction s , shear layer thickness h0, polishing inclination angle α; the shear layer thickness is the shortest distance from the polishing tool head to the surface of the workpiece to be processed; S2: Construct a spatial material removal footprint prediction model for shear thickening polishing, which includes the influence zone size equation and the material removal amount equation; S3: measuring the surface morphology of the workpiece to be processed, obtaining a measurement point matrix, and using a trajectory point generation algorithm to obtain all trajectory points in the polishing area; S4: using the prediction model to calculate the size of the influence area of ​​each trajectory point obtained in S3, with the goal of connecting adjacent trajectory points without interference, optimizing the x and y coordinate values ​​of the trajectory points, adjusting the z coordinate value of the trajectory points with a cubic spline curve based on the adjusted x and y coordinate values ​​and the measurement point matrix, and then sorting them according to the feed route to obtain the trajectory point feed matrix; S5: Calculate the amount of material to be removed H at each trajectory point according to the measurement point matrix and the trajectory point feed matrix, combined with the target surface function. alw ; Perform dwell time iteration for each trajectory point, calculate the iteration height DH during each iteration, and the relationship between DH and H alw If DE is less than or equal to the expected error, the next trajectory point is iterated until all trajectory points are traversed and the residence time matrix is ​​output; otherwise, it is determined whether DH is less than H alw If not, it is updated to a smaller iteration step, and the current trajectory point residence time minus the updated iteration step to start the next iteration. If so, the current trajectory point residence time increases the original iteration step to start the next iteration. S6: Polishing the workpiece using the trajectory point feed matrix and the dwell time matrix on the shear thickening polishing device.

2. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 1, characterized in that: The expression of the prediction model is as follows: ； ； ； In the formula, S represents the size of the affected area, is the viscosity index, x0 is the boundary value of the affected area in the x direction; H material is the material removal amount, mrr is the material removal function, T dwell is the residence time; k is the Preston coefficient, P d is the instantaneous load between the polishing liquid and the workpiece surface, u s is the instantaneous relative velocity of the polishing liquid flowing over the workpiece surface; K is the consistency coefficient, and h(x) represents the distance function from each point on the surface of the tool head immersed in the polishing liquid to the surface of the workpiece to be processed.

3. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 1, characterized in that: In S4, the trajectory points in the impact area are optimized with the goal of connecting adjacent trajectory points without interference. Specifically, the first trajectory point is taken as the reference point, and all trajectory points are traversed in order starting from the current trajectory point. For the current trajectory point, it is judged whether it meets the screening condition. The screening condition is that the x value of the current trajectory point is less than or equal to the x value of the previous trajectory point. If it meets the condition, the current trajectory point is screened out, and the x value of the next trajectory point is continuously judged until the screening condition is not met. At this time, the influence area radii of the current trajectory point and the previous trajectory point are calculated, and a trajectory point adjustment formula is constructed to obtain an offset in the x direction, which is used to update the x coordinate of the current trajectory point.

4. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 3, characterized in that: For the trajectory point matrix H with m rows and n columns pp , the trajectory point adjustment formula is as follows: ； Where i represents the row where the trajectory point is located, i=1,2,3,…,m, j represents the column where the trajectory point is located, j=1,2,3,…,n; c is the jump parameter, c=1,2,3,…,j-1; Indicates the current track point The radius of the affected area, Indicates the previous trajectory point The radius of the affected area; β is the angle between the normal vector of the trajectory point and the z direction, is the offset of the trajectory point in the x direction, Indicates H pp The value of (i,j) in the x direction, Indicates H pp The value of (i,jc) in the x direction.

5. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 1, characterized in that: S5 is specifically implemented through the following sub-steps: (5.1) According to the x coordinates in the measurement point matrix and the trajectory point feed matrix and the y coordinate , fitting the z value of each x and y coordinate on the surface morphology of the workpiece to be processed, recorded as , u=1,2,3,…,l, l is the total number of trajectory points after optimization; combined with the target surface function z m =G(x,y) calculates the amount of material to be removed at each trajectory point H alw (u), the expression is as follows: ； At the same time, set the initial iteration parameters and initialize the number of iterations d i =1; the initial iteration parameters include: expected error E, initial iteration step length Δl, initial dwell time matrix; among which the expected error and initial iteration step length are set manually; (5.2) Traverse all trajectory points one by one, perform iterative calculation of the residence time for the current trajectory point, and calculate the iteration height DH (d i ), number of iterations d i =1,2,3,…, and the residual error DE(d i ), the expression is as follows: ； ； Where mrr is the material removal function, is the dth point of the current trajectory i The dwell time at the iteration; (5.3) Determine the current residual error DE(d i ) is greater than the given expected error E, if so, execute step (5.4), if not, execute step (5.5); (5.4) Determine the current iteration height DH (d i ) is less than the corresponding amount of material to be removed H alw (u), if not, set a smaller iteration step size , the dwell time of the corresponding trajectory point minus one iteration step , the number of iterations increases by 1, and returns to step (5.2); if so, the residence time of the corresponding trajectory point is increased by an iteration step length Δl, the number of iterations increases by 1, and returns to step (5.2); (5.5) Determine whether all trajectory points have been traversed. If not, reset the number of iterations d i =1, iterate the calculation for the next trajectory point and repeat steps (5.2)-(5.3); if yes, end the iteration process and output the updated residence time matrix.

6. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 1, characterized in that: In S3, all trajectory points in the polishing area are obtained using a trajectory point generation algorithm, and the specific operation is as follows: Generate the x and y coordinates of the trajectory point according to the trajectory generation function, take the maximum z value in the measurement point matrix as the calibration value, and add the calibration value to the shear layer thickness h0 to obtain the distance from the trajectory point to the workpiece surface. ,Will Add the normal vector direction of each trajectory point to the target surface function z m =G(x,y), we get , Refers to the superposition of the normal vector direction of each trajectory point The projection length in the z direction; substitute the x and y coordinates of the trajectory point into the formula to obtain the z coordinate of the trajectory point, integrate the x, y, and z coordinates of all trajectory points to obtain the trajectory point matrix, adjust the x and y coordinate values ​​according to the actual size of the polishing area, and complete the coordinate conversion.

7. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 1, characterized in that: In S3, a GPI XP / D laser interferometer is used to measure the surface morphology of the workpiece to be processed to obtain a measurement point matrix.

8. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 1, characterized in that: The shear thickening polishing device comprises: a polishing liquid circulation component, a six-degree-of-freedom ultra-precision machining robot arm, a high-speed electric spindle, a spindle fixture, an angle measuring instrument, a polishing tool, a flexible horizontal calibration component, an optical platform, and a control end; The high-speed electric spindle is fixed to the end joint of the six-degree-of-freedom ultra-precision machining robot arm through a spindle clamp, the polishing tool is coaxially fixed to the high-speed electric spindle, and the polishing tool moves to a specified position under the action of the six-degree-of-freedom ultra-precision machining robot arm; an angle measuring instrument is arranged on the high-speed electric spindle for real-time measurement of the normal angle between the high-speed electric spindle and the workpiece to be processed; the polishing pool is fixed on the optical platform, the workpiece to be processed is fixed in the polishing pool, and the flexible horizontal calibration component is controlled by the control end to keep the workpiece to be processed in a horizontal state; the polishing pool is filled with polishing liquid, and the polishing liquid circulation component is used to keep the polishing liquid in the polishing pool circulating; the control end is used to control the circulation flow rate of the polishing liquid circulation component, the rotation speed of the high-speed electric spindle, and the trajectory point feed matrix and the residence time matrix obtained according to S6 to control the operation of the six-degree-of-freedom ultra-precision machining robot arm.

9. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 8, characterized in that: The polishing liquid circulation component includes: a high-viscosity rotor pump, a polishing pool, a bamboo tube, and a splash shield; the bottom outlet of the polishing pool is connected to the inlet end of the high-viscosity rotor pump through a pipeline, the bamboo tube is fixed above the polishing pool through a spindle clamp, and its inlet end is connected to the outlet end of the high-viscosity rotor pump through a pipeline, and the outlet end is located above the polishing pool. The control end adjusts the polishing liquid flow rate at the bamboo tube outlet by controlling the rotation speed of the high-viscosity rotor pump; the splash shield is fixed to the top of the polishing pool to prevent the polishing liquid from splashing outside the working area.

10. The shear thickening polishing method based on trajectory point and dwell time optimization according to claim 8, characterized in that: The flexible horizontal calibration component includes: a workpiece chuck, a micro cylinder, a compressed air machine, a pressure regulating valve, and a spirit level; the workpiece chuck is arranged in a polishing pool, one end of the four micro cylinders are respectively fixed to the four corners of the lower surface of the workpiece chuck, and the other ends are respectively fixed to the bottom of the polishing pool; the four micro cylinders are respectively connected to the outlet end of the compressed air machine through pipelines, and a pressure regulating valve is provided on the connecting pipeline. The control end coordinates the lifting height of the micro cylinder by controlling the output pressure of the compressed air machine and the opening of the pressure regulating valve to keep the workpiece chuck level; the workpiece to be processed is installed on the upper surface of the workpiece chuck, and the spirit level is arranged around the workpiece to be processed to feedback the horizontality of the workpiece to be processed.

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