Device and method for microstructure splicing of spherical workpieces with on-machine contour measurement and compensation

Abstract

The present invention relates to a device and method for full-surface processing of a microstructure of a spherical workpiece using machine contour measurement and compensation. This device belongs to the field of ultra-precision machining. The device is equipped with a force servo system for scanning the surface contour of the spherical workpiece on the machine, thereby determining the position parameters of the tool and the spherical workpiece, and measuring the deflection angle after secondary installation. The method involved includes: determining the position parameters of the tool and ball through force servo scanning; machining the microstructure surface on a half-spherical surface through force servo machining; transferring the ball to another fixture; re-fixing the fixture containing the ball and scanning to determine the structural deflection parameters; compensating the tool motion path and reference cutting force based on the deflection parameters, and continuing to machine the microstructure on the other half of the workpiece using force servo, thereby achieving full-spherical structural splicing. By analyzing the scanned contour, the present invention can accurately locate the relative position of the tool and ball and accurately measure the deflection angle of the workpiece after secondary clamping, thereby achieving full-spherical structural precision machining.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision machining, and in particular to a device and method for machining microstructures of spherical workpieces with on-machine contour measurement and compensation. Background Art

[0002] Micro- and nanostructures are now widely used in a variety of fields, including optical devices and microfluidic chips, including experimental research on inertial confinement fusion. Targets, with radius sizes ranging from micrometers to submicrometers, are containers for encapsulating nuclear fuel and are key components in inertial confinement fusion. Some researchers have fabricated periodic arrays of structures on the surface of nuclear targets to simulate surface defects and study the impact of target surface quality on the fusion process. As nuclear energy, a clean energy source, continues to face increasing demands for precision in surface microstructure machining as research into the fusion process deepens.

[0003] Commonly used processing methods for microspheres or spherical surfaces include laser processing, atomic force microscopy, and ultra-precision cutting. Laser processing, due to the complexity of the processing mechanism, can result in low surface roughness. Atomic force microscopy has a limited processing range and low processing efficiency, making it difficult to achieve efficient structural processing. Ultra-precision cutting is a high-precision, high-efficiency processing method that can achieve nanometer-level surface roughness and is widely used to process microstructure arrays on various spherical surfaces.

[0004] However, due to the limitations of the fixture, it is difficult to complete the processing of a full global surface in one go by ultra-precision turning. It is necessary to first perform surface microstructure processing on one half of the spherical workpiece, and then perform secondary clamping on the spherical workpiece, and then perform surface microstructure processing on the other half of the spherical workpiece. After the secondary clamping, the position of the spherical workpiece often shifts, and the processing accuracy of the splicing area of ​​the two previous and subsequent processing is often difficult to guarantee. A reliable method to improve processing accuracy is to obtain the posture deviation data of the workpiece surface structure after the secondary clamping through high-precision on-machine measurement technology, and then guide the compensation processing path. However, the existing commonly used on-machine contour measurement equipment, including optical measurement equipment and contact probe scanning contour equipment, are all separated from the processing system, requiring time-consuming unification of the processing-measurement coordinate system origin. Summary of the Invention

[0005] The purpose of the present invention is to provide a microstructure splicing processing method for spherical workpieces based on on-machine contour measurement compensation, so as to solve the problems of separation of on-machine contour measurement and processing system during the micromachining process of the spherical workpiece surface, and the need for time-consuming unification of the origin of the processing-measurement coordinate system.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention relates to a spherical workpiece microstructure splicing processing device with on-machine contour measurement and compensation, which includes a spherical workpiece drive unit and a tool drive unit. The spherical workpiece drive unit includes a linked X-axis motion mechanism, a Y-axis motion mechanism, and a C-axis motion mechanism. The spherical workpiece is mounted on the C-axis motion mechanism through a fixture. The tool drive unit includes a linked Z-axis motion mechanism and a B-axis motion mechanism. The tool is mounted on the B-axis motion mechanism. A force servo system is provided on the tool and the B-axis motion mechanism for scanning the surface contour of the spherical workpiece on-machine, thereby determining the position parameters of the tool and the spherical workpiece.

[0008] Preferably, the force servo system comprises:

[0009] The force detection module is used to install the tool and detect the contact force between the tool and the ball workpiece in real time during the contour scanning process, and send the data to the control module;

[0010] A driving module is used to drive the tool and the force detection module to achieve movement in a single direction;

[0011] The control module is used to control the driving module to stop after detecting the contact force between the tool and the spherical workpiece, and to record the contour coordinates of the spherical workpiece.

[0012] Preferably, the force detection module is also used to detect the main cutting force exerted on the tool during the cutting process in real time, and send the data to the control module; the control module is also used to receive the cutting force data transmitted by the force detection module, and compare it with the ideal cutting force data, adjust and send the servo drive voltage, and control the servo drive module to move.

[0013] The present invention also relates to a method for splicing a microstructure of a spherical workpiece with on-machine contour measurement and compensation, which comprises the following steps:

[0014] S1. Scan the surface profile of the ball workpiece multiple times on the machine through the force servo system, and determine the position parameters of the tool and the ball workpiece based on the multiple scan results;

[0015] S2. Determine the tool motion path based on the position parameters and compensate for the cutting force, machining the microstructured surface on the hemisphere through force servo machining;

[0016] S3. Transfer the ball workpiece to another fixture to achieve direction change;

[0017] S4. The fixture containing the ball workpiece is re-fixed, and the position parameters of the ball tool and the ball workpiece are re-determined in accordance with S1, and the deflection angle of the surface structure of the ball workpiece is determined;

[0018] S5. Compensate the tool motion path and cutting force based on the deflection parameters, and use force servo to continue processing the microstructure on the other hemisphere of the workpiece to achieve structural splicing of the entire global surface.

[0019] Preferably, the position parameters in S1 include the X-axis coordinate of the tool tip when it contacts the spherical workpiece. , Z-axis horizontal distance between the tool tip and the center of the sphere and Y-axis vertical height The specific method is: only turn on the force detection function of the force servo system, turn off the servo function, and make the X-axis motion mechanism perform stepping motion. When the measured force signal reaches the set contact force threshold, stop the movement of the X-axis motion mechanism. At this time, the tool tip contacts the workpiece, and the X-axis coordinate at this time is recorded, which is , taking the current point as the scanning starting point, scan the sphere surface contour in the horizontal and vertical directions respectively, use the least squares method to fit the scan contour into a circle, obtain the coordinates of the circle center, and calculate the horizontal distance based on the coordinates of the starting point and the circle center and vertical height .

[0020] Preferably, the position parameters in S1 include the Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism. , Installation eccentricity distance of ball workpieces and the initial eccentricity angle The specific method is: measure the relative vertical height difference between the tool and the ball workpiece at four different rotation angles of the C-axis motion mechanism, and solve the Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism. , Installation eccentricity distance of ball workpieces and the initial eccentricity angle , the calculation formula is:

[0021] ,

[0022] in, Indicates in i The vertical height measured at each rotation angle is The Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism, is the eccentric distance of the ball, is the initial deflection angle.

[0023] Preferably, the position parameters in S1 include the Z-axis coordinates of the sphere center and the rotation parameters of the tool tip along the B-axis motion mechanism The specific method is: measure the horizontal distance between the tool tip and the center of the spherical workpiece at three different rotation angles of the B-axis motion mechanism, and solve to obtain the distance from the tool tip to the rotation center of the B-axis motion mechanism and the rotation parameters of the tool tip along the B-axis motion mechanism. The calculation formula is:

[0024] ,

[0025] in, , , , , , , and satisfied,

[0026] ,

[0027] in, is the single rotation angle, are the coordinates of the highest point of the contour obtained by three horizontal scans, is the Z-axis coordinate of the sphere center, It is the distance from the center of the tool arc to the rotation center of the B-axis motion mechanism. is the initial angle at which the tool is installed.

[0028] Preferably, the specific method of compensating the cutting force in step S2 is:

[0029] S2.1. Calculate the coordinates of the structure after cutting, which can be expressed as:

[0030] ,

[0031] in, represents the coordinates of the structure after cutting, are the coordinates of the contact point between the tool and the ball, and , ; is the rotation angle of the C-axis motion mechanism, is the installation eccentric distance and initial deflection angle of the spherical workpiece, is the ball diameter of the spherical workpiece, is the height between the tool and the center of rotation of the C-axis motion mechanism, is the ideal cutting depth, is the compensation value;

[0032] S2.2. Correspond the coordinates of the structure after cutting to the relationship between angle and radial cutting depth, expressed as:

[0033] ,

[0034] in, is the angle corresponding to the actual processing point, is the actual cutting depth corresponding to the processing, are the coordinates of the sphere center, , ;

[0035] S2.3. Compare the actual cutting depth with the ideal cutting depth and modify , traverse and solve to obtain the cutting depth corresponding to the minimum error.

[0036] Preferably, the specific method for determining the deflection angle of the surface structure of the ball workpiece in S4 is to decompose the ball workpiece into the rotation angle of the motion mechanism around the B axis. and the rotation angle of the motion mechanism around the C axis , the center of the structure is determined by vertical scanning, and the structural deflection angles at two locations are determined by two horizontal scans. The two satisfy the following relationship:

[0037] ,

[0038] in, represents the structural angle obtained by two scans, Indicates the angle between two positions. They represent the deflection angles of the ball around the B-axis motion mechanism and the C-axis motion mechanism respectively.

[0039] Preferably, in step S5, the coordinates of the tool motion path after compensation are for:

[0040] ,

[0041] in, Represents the B-axis and C-axis rotation angles respectively.

[0042] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0043] The spherical workpiece microstructure splicing processing device with on-machine contour measurement and compensation involved in the present invention is equipped with an additional force servo system for scanning the surface contour of the spherical workpiece on-machine, thereby determining the position parameters of the tool and the spherical workpiece, and measuring the deflection angle after secondary installation. The posture deviation data of the workpiece surface structure after secondary clamping is obtained through high-precision on-machine measurement technology, thereby guiding the compensation processing path, realizing the precise processing of the full global surface structure, the integrated design of contour measurement and processing, eliminating the need for time-consuming unification of the origin of the processing-measurement coordinate system, and improving the processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the processing system in the present invention;

[0045] Figure 2This is the full surface splicing process of the present invention;

[0046] Figure 3 is the horizontal scanning result of the present invention;

[0047] Figure 4 This is the vertical scanning result of the present invention;

[0048] Figure 5 The workpiece installation eccentricity measurement process and results in the present invention;

[0049] Figure 6 The B-axis rotation parameter measurement process and results of the present invention;

[0050] Figure 7 This is a schematic diagram of the effect of installation eccentricity in the present invention;

[0051] Figure 8 This is the double-sine surface deflection angle scanning result of the present invention;

[0052] Figure 9 Schematic diagram of the double-sine surface processing results in the present invention.

[0053] Figure markings: 1-X-axis motion mechanism, 2-Y-axis motion mechanism, 3-Z-axis motion mechanism, 4-C-axis motion mechanism, 5-B-axis motion mechanism, 6-tool, 7-force detection module, 8-drive module, 9-control module, 10-spherical workpiece, 11-clamp. DETAILED DESCRIPTION

[0054] In order to further understand the content of the present invention, the present invention is described in detail with reference to the examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0055] Refer to the attached Figure 1 As shown, the present invention relates to a spherical workpiece microstructure splicing processing device with on-machine contour measurement and compensation, including a spherical workpiece driving unit and a tool driving unit. The spherical workpiece driving unit includes a linked X-axis motion mechanism 1, a Y-axis motion mechanism 2 and a C-axis motion mechanism 4. The spherical workpiece is installed on the C-axis motion 3 mechanism through a fixture 11. The tool driving unit includes a linked Z-axis motion mechanism 3 and a B-axis motion mechanism 5. The tool is installed on the B-axis motion mechanism 5. The X-axis motion mechanism 1, the Y-axis motion mechanism 2, the Z-axis motion mechanism 3, the C-axis motion mechanism 4 and the B-axis motion mechanism 5 are the five motion axes of the machine tool purchased on the market. They are all equipped with grating rulers inside and can record the motion distance in real time.

[0056] The tool 6 and the B-axis motion mechanism 5 are provided with a force servo system for scanning the surface profile of the ball workpiece on the machine, thereby determining the position parameters of the tool 6 and the ball workpiece 10. The force servo system includes:

[0057] The force detection module 7 is used to install the tool 6 and detect the contact force between the tool 6 and the spherical workpiece 10 in real time during the contour scanning process, and send the data to the control module 9. The tool 6 is a diamond tool, which is used to cut the spherical workpiece 10 during the cutting process and serves as a "probe" of the force servo system during the scanning process. The tool 6 and the force detection module 7 are fixed by a threaded connection. The force detection module 7 consists of a pair of parallel leaf springs and a capacitive displacement sensor. The leaf spring stiffness is 0.0818N / μm. The capacitive displacement sensor is used to record the deformation of the leaf spring and transmit the signal to the control module 9. During the cutting process, the force detection module 7 is also used to detect the main cutting force applied to the tool in real time and send the data to the control module.

[0058] The drive module 8 is used to drive the tool 6 and the force detection module 7 to achieve movement in a single direction. The force detection module 7 and the drive module 8 are fixed by a threaded connection. The drive module 8 uses piezoelectric ceramics as a driving element, a capacitive displacement sensor to record the driving displacement, and a flexible hinge as a directional structure to limit the driving direction. The drive module 8 is fixed by a threaded connection to the B-axis motion mechanism 5. At this time, the force servo tool holder can rotate with the B-axis motion mechanism 5.

[0059] The control module 9 is used to control the drive module to stop after detecting the contact force between the tool and the spherical workpiece (that is, after receiving the signal from the force detection module 7), and record the contour coordinates of the spherical workpiece; during the cutting process, the control module 9 is also used to receive the cutting force data transmitted by the force detection module 7, and compare it with the ideal cutting force data, adjust and send the servo drive voltage, and control the servo drive module to move.

[0060] In addition, the ball workpiece 10 and the fixture 11 are connected by UV glue, which can be cured by ultraviolet light. The fixture 11 can be fixed to the C-axis motion mechanism 4 by vacuum adsorption, and the fixture 11 can rotate along with the C-axis motion mechanism.

[0061] Refer to the attached Figure 2 As shown, the present invention also relates to a method for splicing microstructures of spherical workpieces with on-machine contour measurement and compensation, which comprises the following steps:

[0062] S1. The surface profile of the ball workpiece is scanned multiple times on-machine using the force servo system. Based on the multiple scan results, the position parameters of the tool and the ball workpiece are determined. The position parameters include the horizontal distance between the tip of the diamond tool 6 and the center of the ball workpiece 10, the vertical height between the tip of the diamond tool 6 and the rotation center of the C-axis motion mechanism 4, the installation eccentricity of the ball workpiece 10, and the rotation parameters of the tip of the diamond tool 6 rotating with the B-axis motion mechanism 5. The specific measurement method is as follows:

[0063] Measure the X-axis horizontal distance between the tool tip and the center of the sphere , only the force detection function of the force servo system is turned on, the servo function is turned off, and the X-axis is made to perform a stepping motion with an interval of 2nm. When the measured force signal reaches the set contact force threshold, the X-axis motion is stopped. At this time, the tool tip contacts the workpiece, and the X-axis coordinate at this time is recorded, which is Before each scan of the contour and machining structure, you need to repeat this step and re-determine .

[0064] Measure the Z-axis horizontal distance between the tool tip and the center of the sphere and Y-axis vertical height When scanning, the tool tip is used as the starting point of the scan. The tool scans the surface contour of the sphere in the horizontal and vertical directions. The scan contour is fitted into a circle using the least squares method to obtain the coordinates of the center of the circle. The horizontal distance and vertical height are calculated based on the coordinates of the starting point and the center of the circle. For example, the Z-axis motion structure 3 drives the tool 6 to move along the Z-axis direction, and the control module 9 keeps the tool 6 in contact with the ball workpiece 10 with a very small contact force. The scanning reference force is 1.7 mN, and the surface profile of the ball workpiece can be obtained by reading the machine tool movement distance and the servo drive distance; Figure 3 The result of one horizontal scan is shown. The center position of the sphere can be obtained by fitting the scan profile into a circle using the least squares method. , which is the horizontal distance between the tip of the diamond tool 6 and the center of the spherical workpiece 10 , the formula for finding the center of the circle using the least squares method is:

[0065] ,

[0066] in, represents the coordinates of the center of the fitted circle, represents the radius of the fitted circle, , The first i coordinate points, and i ∈[0, n ], n is the total number of coordinate points for measuring the contour, X Represents the parameter vector to be solved The coefficient matrix of Y represents a constant matrix.

[0067] Measure the vertical height between the tool tip and the center of the sphere The method is similar to the method of measuring horizontal distance. The Y-axis motion structure 3 drives the ball workpiece 10 to move along the Y-axis direction. The control module 9 keeps the diamond tool 6 in contact with the ball workpiece 10 with a very small contact force. The surface profile of the ball workpiece can be obtained by reading the movement distance of the Y-axis motion structure 3 and the servo drive distance. Figure 4The results of one vertical scan are shown, and the measured profile is calculated by the least square method. The center position of the circle obtained by fitting , which is the vertical height between the tool tip and the center of the sphere .

[0068] Measure the Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism , Installation eccentricity distance of ball workpieces and eccentricity angle The process is as follows Figure 5 As shown in (a), the relative vertical height difference between the tool and the ball workpiece at four different rotation angles of the C-axis motion mechanism 4 is measured; Figure 5 (b) shows the actual measurement results. The spatial distribution of the sphere center in the four measurements should be on a circle with the rotation center of the C-axis motion mechanism 4 as the center and the radius as the eccentric distance. The four measurement results satisfy the following relationship:

[0069] ,

[0070] in, are the coordinates of the 4 measurement results, is the coordinate of the rotation center from the tool tip to the C-axis motion mechanism, is the eccentric distance, is the initial deflection angle of the ball, which can be solved as:

[0071] ,

[0072] in, Indicates in i The vertical height measured at each rotation angle is is the coordinate of the rotation center from the tool tip to the C-axis motion mechanism, is the eccentric distance of the ball, is the initial deflection angle.

[0073] Z-axis coordinate of the center of the sphere The rotation parameters of the tool tip along the B-axis motion mechanism can be obtained through the horizontal scanning results at three different B-axis rotation angle positions. Figure 6 (a) shows the experimental process, in which the horizontal distance between the tip of the diamond tool 6 and the center of the ball workpiece 10 is measured at three positions where the B-axis motion mechanism 5 rotates at 0°, 2°, and 4°. Figure 6 (b) shows the actual measurement results. The three measurement results should satisfy the following relationship:

[0074] ,

[0075] in, is the horizontal relative distance between the tool tip and the sphere center obtained by three horizontal scans, is the Z-axis coordinate of the sphere center, is the distance from the center of the tool arc to the center of rotation of the B axis, It is the initial angle when the machine tool is installed. is a single rotation angle, and the three positions are respectively rotated relative to the initial angle The position of the tool tip can be solved to get the distance from the tool tip to the rotation center of the B-axis motion mechanism and the rotation parameters of the tool tip along the B-axis motion mechanism. The calculation formula is:

[0076] ,

[0077] in, , , , , , , is the single rotation angle, These are the coordinates of the highest point of the contour obtained by three horizontal scans.

[0078] S2. Determine the tool motion path based on the position parameters and compensate the cutting force, and process on the hemisphere through force servo processing. During the processing, the C axis of the machine tool rotates continuously, and the rotation angle is ; The tool is fixed on the B axis and rotates together with the tool. The rotation angle is The Y-axis coordinate of the machine tool remains unchanged; the X-axis and Z-axis move accordingly according to the rotation angle of the tool B-axis. Tool motion path coordinates for:

[0079] ,

[0080] in, Indicates the tool motion path coordinates; Indicates the initial position of the tool; is the radius of the scan profile fitting circle; They represent the rotation angles of the B-axis motion mechanism respectively; It is the distance from the center of the tool arc to the B-axis rotation center obtained in step S1 and the initial installation angle of the tool.

[0081] Machining structure contour equation It can be expressed as a function of the B-axis and C-axis rotation angles. Taking the double-sinusoidal surface as an example, the cutting volume per unit time can be calculated based on the structural shape; the double-sinusoidal surface shape equation is:

[0082] ,

[0083] in, Indicates cutting depth; are the structural amplitudes, which are taken as 60 nm and 75 nm respectively in this embodiment; is the reference amplitude, which is taken as 50nm in this example; Indicates the C-axis rotation angle; Indicates the B-axis rotation angle; They represent the three-dimensional coordinates of the double sine surface respectively.

[0084] By calibrating the relationship between cutting force and cutting volume, the required reference cutting force can be calculated based on the cutting volume corresponding to the machined structure shape. The calibration experiment process is as follows: Sinusoidal grooves are cut on a silicon wafer, the cutting force is set to 2.84mN-8.52mN, and the cutting speed is set to 0.05mm / min. The cross-sectional area of ​​the structure can be obtained based on the white light observation results, and the cutting volume is obtained by multiplying it with the cutting speed. The cutting depth can be used to correspond the cutting force to the cutting volume. Using a quadratic polynomial, the relationship between the cutting volume and the cutting force can be obtained as follows: .

[0085] The specific way to compensate cutting force is:

[0086] S2.1. During microstructure processing, the Y axis is not moved to reduce the error caused by additional motion. The effect of eccentricity on processing is compensated by cutting force; e.g. Figure 7 As shown in the figure, under the influence of the ball installation eccentricity and tool height correction deviation, the structural coordinates after cutting can be expressed as:

[0087] ,

[0088] in, represents the coordinates of the structure after cutting, is the coordinate of the contact point between the tool and the spherical workpiece, and , ; is the rotation angle of the C-axis motion mechanism, is the installation eccentricity distance and initial deflection angle of the ball obtained in step S1, is the ball diameter of the spherical workpiece, is the height between the tool and the center of rotation of the C-axis motion mechanism, is the ideal cutting depth, is the compensation value;

[0089] S2.2. Correspond the coordinates of the structure after cutting to the relationship between angle and radial cutting depth, expressed as:

[0090] ,

[0091] in, is the angle corresponding to the actual processing point, is the actual cutting depth corresponding to the processing, are the coordinates of the sphere center, , ;

[0092] S2.3. Actual cutting depth Ideal cutting depth Compare and modify , traverse and solve to obtain the cutting depth corresponding to the minimum error.

[0093] The microstructure surface is machined on a semi-sphere through force servo machining. During the machining process, the B-axis motion mechanism 5 drives the tool 6 to rotate so that the center line of the tool 6 always passes through the center of the sphere, realizing normal follow-up machining; at the same time, the X-axis motion mechanism 1 and the Z-axis motion mechanism 3 follow the B-axis motion structure in accompanying movement; the control module controls the actual cutting force according to the set reference force to realize the machining of the required structure.

[0094] S3. Transfer the ball workpiece to another fixture to achieve orientation change: Secure two ball fixtures to a manually adjustable translation stage. One side consists of a stacked Z- and Y-axis translation stage, while the other side features an X-axis translation stage. This allows for position adjustment in the X, Y, and Z directions. UV glue is still used for securing. After UV curing, one side is immersed in cold water, while the other side is kept away from water. Wait for the UV glue to fall off, and the position change is achieved.

[0095] S4. Re-fix the fixture containing the ball workpiece, re-determine the position parameters of the ball tool and the ball workpiece in accordance with S1, and determine the deflection angle of the surface structure of the ball workpiece; Figure 8 As shown in the figure, the specific method for determining the deflection angle of the surface structure of the ball workpiece is to decompose the ball workpiece into the rotation angle of the motion mechanism around the B axis. and the rotation angle of the motion mechanism around the C axis , which can be obtained by horizontal scanning and vertical scanning profile. Before horizontal scanning and vertical scanning, the height change caused by eccentricity is compensated to eliminate its influence on scanning. According to the scanning profile information, the relationship between the cutting depth and the angle can be obtained, which is convenient for calculating the structural angle position deflection parameters. The conversion relationship is:

[0096] ,

[0097] in, are the coordinates of the scanned contour, are the angle and the cutting depth in radial direction, are the coordinates of the center of the fitted circle, is the radius of the fit.

[0098] Taking the double-sine structure deflection angle scanning as an example, the experimental process is as follows: (1) Obtain the horizontal scanning profile curve, with The first peak point of the curve is the characteristic point, and the angle corresponding to the peak point minus the angle corresponding to the structure is the deflection angle. In this example, the structural angle corresponding to the first peak point is 1°; (2) Move the tool to the location of the structure, perform vertical scanning, determine the lowest point of the structure in the vertical direction, and obtain the corresponding angle ; (3) Rotate the C-axis motion mechanism 4, the rotation angle is , so that the lowest point of the structure is located at the center of the vertical scan; (4) Repeat steps (1) (2) (3) until , at this time we get This is the final result.

[0099] Horizontal can determine the deflection angle and declination angle The geometric relationship is as follows:

[0100] ,

[0101] in, After the structure is deflected The coordinates of is the deflection angle of the ball around the B axis, is the deflection angle of the ball around the C axis, is the deflection angle of the structure obtained by scanning.

[0102] Simplifying to get:

[0103] .

[0104] The center of the structure is determined by vertical scanning, and the deflection angles of the structure at two locations are determined by two horizontal scans. The two satisfy the following relationship:

[0105] ,

[0106] in, represents the structural angle obtained by two scans, Indicates the angle between two positions. They represent the deflection angles of the ball around the B-axis motion mechanism and the C-axis motion mechanism respectively.

[0107] Calculation yields:

[0108] .

[0109] S5. Compensate the tool motion path and cutting force based on the deflection parameters, and use the force servo to continue processing the microstructure on the other hemisphere of the workpiece to achieve full-sphere structural splicing; the coordinates of the tool motion path after compensation are for:

[0110] ,

[0111] in, Represents the B-axis and C-axis rotation angles respectively.

[0112] Using the above method, we conducted double sinusoidal surface splicing experiments on a silicon ball with a diameter of 5 mm. The processing results are shown in the figure below. Figure 9 As shown, the structural positioning accuracy of the C-axis and B-axis is within ±0.05°, and the machining depth consistency is within ±20nm. This shows that the spherical workpiece microstructure splicing processing method based on on-machine contour measurement compensation of the present invention can achieve high-precision spherical microstructure splicing processing.

[0113] The present invention has been described in detail above with reference to the embodiments. However, the contents described are only preferred embodiments of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A microstructure splicing processing method for ball workpieces with on-machine contour measurement and compensation, characterized in that: It includes the following steps: S1. Use the force servo system to scan the surface profile of the ball workpiece multiple times on the machine, and determine the position parameters of the tool and the ball workpiece based on the multiple scanning results. The position parameters include the X-axis coordinate of the tool tip when it contacts the ball workpiece. , Z-axis horizontal distance between the tool tip and the center of the sphere and Y-axis vertical height , Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism , Installation eccentricity distance of ball workpieces and the initial eccentricity angle , Z-axis coordinate of the sphere center , the rotation parameters of the tool tip along the B-axis motion mechanism ; S2. Determine the tool motion path based on the position parameters and compensate for the cutting force, machining the microstructured surface on the hemisphere through force servo machining; S3. Transfer the ball workpiece to another fixture to achieve direction change; S4. Re-fix the fixture containing the ball workpiece, re-determine the position parameters of the ball tool and the ball workpiece according to the method of S1, and determine the deflection angle of the surface structure of the ball workpiece; the specific method for determining the deflection angle of the surface structure of the ball workpiece is to decompose the ball workpiece into the rotation angle of the motion mechanism around the B axis and the rotation angle of the motion mechanism around the C axis , the center of the structure is determined by vertical scanning, and the structural deflection angles at two locations are determined by two horizontal scans. The two satisfy the following relationship: ， in, represents the structural angle obtained by two scans, Indicates the angle between two positions. They represent the deflection angles of the ball around the B-axis motion mechanism and the C-axis motion mechanism respectively; S5. Compensate the tool motion path and cutting force based on the deflection parameters, and use force servo to continue processing the microstructure on the other hemisphere of the workpiece to achieve structural splicing of the entire global surface.

2. The method for microstructure splicing of spherical workpieces with on-machine contour measurement and compensation according to claim 1, characterized in that: In step S1, the X-axis coordinate of the tool tip when in contact with the spherical workpiece is determined. , Z-axis horizontal distance between the tool tip and the center of the sphere and Y-axis vertical height The specific method is: only turn on the force detection function of the force servo system, turn off the servo function, and make the X-axis motion mechanism perform stepping motion. When the measured force signal reaches the set contact force threshold, stop the movement of the X-axis motion mechanism. At this time, the tool tip contacts the workpiece, and the X-axis coordinate at this time is recorded, which is , taking the current point as the scanning starting point, scan the sphere surface contour in the horizontal and vertical directions respectively, use the least squares method to fit the scan contour into a circle, obtain the coordinates of the circle center, and calculate the horizontal distance based on the coordinates of the starting point and the circle center and vertical height .

3. The method for microstructure splicing of spherical workpieces with on-machine contour measurement and compensation according to claim 1, characterized in that: The Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism is determined in S1 , Installation eccentricity distance of ball workpieces and the initial eccentricity angle The specific method is: measure the relative vertical height difference between the tool and the ball workpiece at four different rotation angles of the C-axis motion mechanism, and solve the Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism. , Installation eccentricity distance of ball workpieces and the initial eccentricity angle , the calculation formula is: ， in, Indicates in i The vertical height measured at each rotation angle is The Y-axis distance from the tool tip to the rotation center of the C-axis motion mechanism, is the eccentric distance of the ball, is the initial deflection angle.

4. The method for microstructure splicing of spherical workpieces with on-machine contour measurement and compensation according to claim 1, characterized in that: Determine the Z-axis coordinate of the center of the sphere in S1 and the rotation parameters of the tool tip along the B-axis motion mechanism The specific method is to measure the horizontal distance between the tool tip and the center of the spherical workpiece at three different rotation angles of the B-axis motion mechanism, and solve the distance from the tool tip to the rotation center of the B-axis motion mechanism and the rotation parameters of the tool tip along the B-axis motion mechanism. The calculation formula is: ， in, , , , , , , and satisfied, ， in, is the single rotation angle, are the coordinates of the highest point of the contour obtained by three horizontal scans, is the Z-axis coordinate of the sphere center, It is the distance from the center of the tool arc to the rotation center of the B-axis motion mechanism. is the initial angle at which the tool is installed.

5. The method for microstructure splicing of spherical workpieces with on-machine contour measurement and compensation according to claim 1, characterized in that: The specific method of compensating the cutting force in step S2 is: S2.

1. Calculate the coordinates of the structure after cutting, which can be expressed as: ， in, represents the coordinates of the structure after cutting, are the coordinates of the contact point between the tool and the ball, and , ; is the rotation angle of the C-axis motion mechanism, is the installation eccentric distance and initial deflection angle of the spherical workpiece, is the ball diameter of the spherical workpiece, is the height between the tool and the center of rotation of the C-axis motion mechanism, is the ideal cutting depth, is the compensation value; S2.

2. Correspond the coordinates of the structure after cutting to the relationship between angle and radial cutting depth, expressed as: ， in, is the angle corresponding to the actual processing point, is the actual cutting depth corresponding to the processing, are the coordinates of the sphere center, , ; S2.

3. Compare the actual cutting depth with the ideal cutting depth and modify , traverse and solve to obtain the cutting depth corresponding to the minimum error.

6. The method for microstructure splicing of spherical workpieces with on-machine contour measurement and compensation according to claim 1, characterized in that: In step S5, the coordinates of the tool motion path after compensation for: ， in, Represents the B-axis and C-axis rotation angles respectively.

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