CN116572077B - Method for normal measurement of large-curvature free-form surface - Google Patents
Method for normal measurement of large-curvature free-form surface Download PDFInfo
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- 238000004441 surface measurement Methods 0.000 abstract description 3
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- 238000012625 in-situ measurement Methods 0.000 description 9
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P90/02—Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]
Abstract
The invention belongs to the field of curved surface measurement, and particularly discloses a large-curvature free-form surface normal measurement method, wherein a measurement device is arranged on a B axis of a five-axis machining center, so that a laser point of a measuring head of the measurement device is focused at the position of the rotation center of the B axis; installing a workpiece on a C shaft of a five-shaft machining center; determining origin coordinates of a measuring head origin of a measuring device at the center of a workpiece; acquiring real-time position coordinates of a measuring head on a machine tool; generating a normal swing grating type measuring path of the free curved surface according to an origin coordinate of the origin of the measuring head at the center of the workpiece, discrete point cloud data of the free curved surface and accurate control of a B-axis normal swing angle; in the path, the measuring head is driven by X/Z/B three-axis linkage to scan the outline along the free curved surface, and the distance between the measuring head and the free curved surface in the normal vector direction is always the focal length of the measuring head in the scanning process; and (3) feeding the measuring head in the Y-axis direction according to a given step length every time one line of scanning is completed, and completing the contour scanning of the next line.
Description
Technical Field
The invention belongs to the field of curved surface measurement, and particularly discloses a large-curvature free-form surface normal measurement method.
Background
With the progress of precision processing technology and optical design level, the requirements on functions and performances of optical free-form surface elements are increasingly diversified, the product structure is also increasingly complex, the complex free-form surfaces are combined into an optical system, the structure and performances of the product are optimized, various high-added-value photoelectric products are changed to complex free-form surface optical elements with microstructure characteristics and non-rotational symmetry, and the complex free-form surface optical elements are indispensable key elements in photoelectric information technology and optical communication technology. In recent years, optical freeform surface elements are widely used in national defense and civil photoelectric products, such as laser devices, digital camera lenses, laser printer scanner lenses, fiber optic connectors, LED lighting systems, and the like. The free curved surface is introduced into the optical imaging system, so that the number of lens sheets can be reduced, the size and weight of the system are reduced, and the imaging quality and energy transmission efficiency of the system are improved. The development of the universal reality technologies such as VR, AR, MR and the like is further promoted by the proposal of the metauniverse concept, and the optical free-form surface is taken as a necessary component of the virtual wearable device, so that the market demand is huge and in rapid growth.
Because of the high surface shape precision requirement of the optical free-form surface, the processing surface often needs to carry out the production flow of forming, measuring and compensating for a plurality of times, so that the ultra-precise measurement is also a key link of the optical free-form surface processing, and has important significance for the ultra-precise processing of the free-form surface. Current measurement systems mainly include off-line and on-line measurement systems. The commercial measuring equipment which should be relatively wide belongs to off-line measurement, namely, the workpiece is taken off from the machine tool after being processed, the measurement is carried out on an off-line measuring instrument, the workpiece is clamped on the machine tool again after the measurement is finished, and the workpiece is processed again according to the measurement result. This inevitably increases many non-machining times and introduces secondary clamping errors. The problems can be effectively solved by online measurement, the convenience is provided for subsequent error compensation, but along with the continuous upgrading and updating of optical devices, the precision and the installation requirement of optical lenses are continuously improved, the optical elements are slowly developed from an integrated single lens to an integrated multi-lens and large-curvature optical free-form surface, the measurement requirement of the large-curvature optical free-form surface is difficult to be realized by the traditional online measurement method, and the measurement precision is greatly influenced by the measurement angle.
The patent CN115540730A discloses a coordinate measuring system and a method for a high-steepness or deep-concave complex curved surface, which are characterized in that an inductive measuring head is arranged on a B axis of an ultra-precise machine tool, the outline of the high-steepness and deep-concave curved surface is detected in a side-triggered mode based on the good detection performance of the inductive measuring head, and the acquisition of the surface shape can be completed only by moving an X/Z/C axis of the machine tool. However, the measurement method is still based on a three-coordinate measurement system, and a certain speed is needed to be respectively close to a measurement point from the Z direction and the X direction in the measurement process, so that the measurement speed is low, the number of measurement points is limited, and the measurement efficiency is greatly limited. Meanwhile, the surface shape error of each point cannot be directly obtained in the measuring process, the measured data is required to be processed again in the later period, and the data analysis process is complex.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a large-curvature free-form surface normal measurement method.
In order to achieve the above object, the present invention is realized by the following technical scheme:
in a first aspect, an embodiment of the present invention provides a method for normal measurement of a free-form surface with a large curvature, as follows:
step 1, mounting a measuring device on a B axis of a five-axis machining center so that a measuring head of the measuring device
Focusing a laser spot at the position of the rotation center of the B axis;
step 2, installing a workpiece on a C shaft of a five-shaft machining center;
step 3, determining origin coordinates of a measuring head origin of a measuring device at the center of a workpiece;
step 4, the data acquisition device, the measuring device and the X/Y/Z/B/C shaft of the five-shaft machining center are combined
The output interface of the grating signal is connected;
step 5, generating a free-form surface normal swing grating type measuring path according to the origin coordinates of the origin of the measuring head, which are determined in the step 3, at the center of the workpiece, the position coordinates of the discrete points of the free-form surface and the B-axis normal swing angle; the measuring head in the path is driven by X/Z/B three-axis linkage to scan the outline along the free curved surface, and the distance between the measuring head and the spherical surface in the normal vector direction is the focal length of the measuring head in the scanning process; every time one line of scanning is completed, the measuring head is fed in the Y-axis direction according to a given step length, and then the contour scanning of the next line is completed.
As a further technical scheme, the measuring device is arranged on the B shaft through a clamp.
As a further technical scheme, anchor clamps include base, lower base and clamping device, lower base top installation be equipped with the location ball post, last base install the location ball post on, clamping device fix on last base.
As a further technical scheme, the measuring device is a spectral copolymer Jiao Weiyi sensor.
As a further technical scheme, the data acquisition device is an FPGA board card controller.
As a further technical scheme, the FPGA board card controller is respectively designed with X/Y/Z/B/C ports; the X/Y/Z/B/C port is connected with an output interface of a grating signal subdivision box of an X/Y/Z/B/C axis of the five-axis machining center; and a sensor trigger port on the FPGA board controller is connected with a controller port of the measuring device.
As a further technical scheme, in the step 1, an optical tool setting gauge and a rotary gauge rod are utilized to adjust the focusing position of the laser point of the measuring head.
As a further technical scheme, the specific process of step 3 is as follows:
moving an X axis and a Y axis of the machine tool, adjusting the laser origin of the measuring head to the central position of the workpiece, and calibrating the coordinates of the central position; taking the central position coordinate as the origin of coordinatesTwo symmetrical points are respectively taken in the X direction and the Y direction of the free curved surface>、/>And->、/>The method comprises the steps of carrying out a first treatment on the surface of the When the X-direction measurement origin is calibrated, two symmetrical points are respectively measured by using the measuring head>And->Calculating the origin offset in the X direction according to the error valueCorrecting the origin of the measuring center to be +.>According to the corrected measurement origin coordinates +.>Recalculating the position coordinates of two symmetrical points at the same position of the free curved surface>、Re-measuring the two symmetrical points, calculating the origin offset in the X direction>Correcting the origin of the measuring center again to obtain +.>The calibration process is iterated a plurality of times until the origin offset in the X direction is less than 1 μm, at which point the origin coordinates are +.>；
Repeating the steps, calibrating the origin of the Y-axis direction until the offset of the origin of the Y-axis direction is smaller than 1 mu m, and finally obtaining the origin coordinate measured by the measuring head as follows。
As a further technical proposal, the B-axis normal swinging angleThe following are provided:
(1)
in the method, in the process of the invention,and->Is the normal vector of the discrete points of the free curved surface in the X and Z directions.
As a further technical scheme, the method for obtaining the three-dimensional discrete point cloud represented by the curved surface comprises the following steps: and vertically projecting the free curved surface to an XY plane, forming a rectangular area by a maximum value and a minimum value, dividing the rectangular area into grids to obtain (X, Y) coordinates, and determining the precision delta X and delta Y of the grid treatment of the X axis and the Y axis according to the requirements of processing precision and the degree of density of point cloud. For each grid coordinate point (x, y) there is a corresponding Z-axis coordinate value, i.e. there is a one-to-one single-valued functional relationship for points on the XY plane and Z-axis height values, the free-form surface can be represented as a three-dimensional discrete point cloud (x, y, Z).
The beneficial effects of the embodiment of the invention are as follows:
the invention develops a non-contact in-situ normal measurement method and related system components aiming at an integrated multi-lens large-curvature optical free-form surface element. By means of an ultra-precise five-axis linkage processing machine tool, a spectrum copolymerization Jiao Weiyi sensor and a high-precision detachable in-situ measurement clamp, the shape error of each measurement point of a measured workpiece is directly obtained by precisely controlling and feeding back the rotation angle of the B axis and controlling the linkage of the X\Y\Z\B four axes to ensure that the measuring head always performs raster scanning along the normal direction of the workpiece according to a designed measurement path in the measurement process. Meanwhile, the FPGA board card controller is developed and connected with a machine tool data output interface to acquire coordinate information of a machine tool PMAC control card, and signal output is realized through software, so that real-time acquisition of coordinate positions is realized, and all acquisition and motion control are synchronously performed. The in-situ measurement method and the in-situ measurement system can directly acquire the surface shape error of the measured surface, thereby realizing large-range high-precision measurement of the small-range sensor, avoiding the influence of the measurement angle on the measurement precision in the non-contact measurement process in a normal measurement mode, avoiding the later-stage surface shape matching processing and error analysis of the measurement data, and simultaneously improving the measurement efficiency while ensuring the measurement precision because a traditional active detection measurement mode of a coordinate measuring instrument is not adopted; and the measurement data can be controlled by the density degree of the design of the measurement path, so that the measurement is flexible.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a schematic diagram of an in-situ measurement system of the present disclosure;
FIG. 2 is a schematic illustration of an in-situ measurement fixture of the present disclosure;
FIG. 3 is a schematic diagram of the calibration of the measuring focus of the measuring head to the center of rotation of the B axis;
FIG. 4 is a schematic illustration of an in-situ measurement path planning in accordance with the present invention;
in the figure: 1-a machine tool body; 2-X axis; 3-Y axis; a 4-Z axis; a 5-C axis; a 6-B axis; 7-an optical tool setting gauge; 8-a workpiece; 9-diamond turning tool; 10-knife rest; 11-measuring a clamp; 12 measuring head; 13-FPGA board card; 14-a computer; 15-a lower base; 16-upper base; 17-positioning ball posts; 18-connecting seats; 19-a clamping device; 20 dipsticks.
Detailed Description
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular forms also are intended to include the plural forms unless the present invention clearly dictates otherwise, and furthermore, it should be understood that when the terms "comprise" and/or "include" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof;
the terms "mounted," "connected," "secured," and the like are to be construed broadly and refer to either a fixed connection, a removable connection, or an integral body, for example; the terms are used herein as specific meanings as understood by those of ordinary skill in the art, and are not limited to the following terms.
As described in the background art, the present invention provides a method for measuring a normal direction of a free-form surface with a large curvature in order to solve the above technical problems.
In a typical embodiment of the invention, as shown in fig. 1, the method for measuring the normal direction of the large curvature free-form surface is realized based on an ultra-precise five-axis machining center, and specifically, a measuring system corresponding to the method comprises the ultra-precise five-axis machining center, an FPGA board card controller, a spectrum confocal displacement sensor and a high-precision detachable in-situ measuring clamp 11;
the ultra-precise five-axis machining center comprises a machine tool body 1, wherein an X axis 2, a Y axis 3, a Z axis 4, a C axis 5 and a B axis 6 are arranged on the machine tool body 1; a measuring clamp 11 and a tool rest 10 are arranged on the B shaft 6, and a diamond turning tool 9 is arranged on the tool rest 10, wherein the measuring clamp 11 is used for clamping a measuring head 12; the workpiece is arranged on the C shaft 5; the FPGA board card controller can acquire displacement signals of all coordinate axes of the machine tool, so that real-time position coordinates of all measurement points are obtained; the FPGA board 13 is connected with a computer 14.
According to the free-form surface parameter equation or the discrete point cloud data, a numerical control program of a measuring head normal measurement motion track is calculated, an ultra-precise machining center is used as a working platform for in-situ measurement, and the free-form surface in-situ normal measurement is realized through accurate control and feedback of a B-axis rotation angle and linkage control of an X\Y\Z\B four axis.
The high-precision detachable measuring clamp 11 can realize free detachment of the measuring device and prevent mutual interference between measurement and processing.
Further, the FPGA board 13 is respectively provided with an X/Y/Z/B/C port, and is respectively connected with an output interface of a grating signal subdivision box of an X/Y/Z/B/C shaft of an ultra-precise five-shaft machining center, so that motion signals of all coordinate axes of a machine tool are collected, a sensor trigger port on the board is connected with a controller port of a spectral copolymerization Jiao Weiyi sensor, and finally synchronous collection of measurement data and position coordinates is realized through developed unified measurement software, the one-to-one correspondence of shape errors of measurement points and surface position coordinates is ensured, and the collection frequency is consistent;
after the measurement system is connected, the measuring head needs to be fixed on a high-precision detachable measurement clamp; as shown in fig. 2, the measuring fixture mainly comprises an upper base 16, a lower base 15 and a lens clamping device 19. Wherein the lower base 15 is fixed on the table top of the B axis of the machine tool through bolts. Three precise positioning ball columns 17 are fixed on the upper part of the lower base 15 and used for high-precision positioning of the upper base 16. The spectrum copolymer Jiao Weiyi sensor probe is fixed on the upper base 16 through the lens clamping device 19 and the connecting seat 18. When free-form surface measurement is carried out, the upper base 16 is only required to be placed on the three positioning ball columns 17 of the lower base 15, after measurement is finished, the upper base 16, the lens clamping device 19 and the displacement sensor measuring head are only required to be taken down together, and interference between the displacement sensor measuring head and a workpiece is avoided when free-form surface machining is carried out.
The normal measurement needs to strictly control the angle change of the spectrum copolymerization Jiao Weiyi sensor measuring head, so after the measuring head is fixed, the measuring head position of the spectrum confocal displacement sensor needs to be adjusted to ensure that the laser spot of the spectrum copolymerization Jiao Weiyi sensor measuring head is focused on the central line of the rotation center of the B axis. As shown in fig. 3, the laser spot focusing position of the probe is adjusted by the optical tool setting gauge 7 and the precision rotary inspection bar 20 (radius R). The position of the B-axis center of rotation is determined by first adjusting the center of rotation of the dipstick to coincide with the B-axis center of rotation using the precision rotation dipstick 20 and then determining the position coordinates of the center of rotation of the dipstick using the optical tool setting gauge. And then the spectrum copolymerization Jiao Weiyi sensor measuring head is adjusted to be vertical to an XY plane where the machine tool is located, the position of the measuring head is adjusted by utilizing a two-axis precise displacement platform, the laser spot of the spectrum copolymerization Jiao Weiyi sensor measuring head is focused to the highest point of the bus of the detecting rod 20, and at the moment, the precise displacement platform is adjusted to enable the spectrum copolymerization Jiao Weiyi sensor measuring head to move a distance R along the negative direction of the Z axis, so that the laser spot of the spectrum confocal displacement sensor measuring head can be focused to the central line of the rotation center of the B axis for normal measurement.
After the position of the measuring head of the spectrum confocal displacement sensor is determined, the workpiece is fixed on a main shaft of a machine tool, and light needs to be ensured before the ultra-precise normal measurement of the free curved surface is startedThe accurate alignment of the spectral copolymer Jiao Weiyi sensor probe, i.e., the position coordinates of the measurement origin of the spectral copolymer Jiao Weiyi sensor probe at the center of the workpiece, were determined. The invention realizes automatic matching of the measuring center by using the calibration module arranged in the measuring software. First, the X axis and the Y axis of the machine tool are manually moved, the laser origin of the measuring head of the spectral copolymer Jiao Weiyi sensor is adjusted to the central position of the workpiece, and then the coordinates of the central position are calibrated. Taking the central position coordinate as the origin of coordinatesTwo symmetrical points are respectively taken in the X direction and the Y direction of the free curved surface、/>And->、/>. When the X-direction measurement origin is calibrated, two symmetrical points are respectively measured by using the measuring head>And->Calculating the X-direction origin offset from the error value>Correcting the origin of the measuring center to be +.>According to the corrected measurement origin coordinates +.>Recalculating the position coordinates of two symmetrical points at the same position of the free curved surface>、/>Re-measuring the two symmetrical points, calculating the origin offset in the X direction>Correcting the origin of the measuring center again to obtainThe calibration process is iterated a plurality of times until the origin offset in the X direction is less than 1 μm, at which point the origin coordinates are +.>. Repeating the steps, calibrating the origin of the Y-axis direction until the offset of the origin of the Y-axis direction is smaller than 1 mu m, and finally obtaining the origin coordinate measured by the measuring head as +.>。
After the measurement origin is determined, planning a normal scanning path of the measuring point according to the surface profile shape of the free curved surface. The path is designed as a space normal swinging raster scanning path formed by the linkage of three linear axes of an X axis, a Y axis and a Z axis and a B axis rotation axis. In the path, the measuring head is driven by X/Z/B three-axis linkage to scan the contour along the free curved surface, and the distance between the measuring head and the spherical surface in the normal vector direction is the focal length of the measuring head in the scanning process. Every time one line of scanning is completed, the measuring head is fed in the Y-axis direction according to a given step length, and then the contour scanning of the next line is completed.
Angle of B-axis normal swingCan be obtained from the formula (1).
(1)
In the method, in the process of the invention,and->Is the normal vector of the discrete points of the free curved surface in the X and Z directions.
Through the path planning, a free-form surface normal swing grating type measuring path is generated according to the measuring head measuring origin position coordinates, free-form surface discrete point cloud data and the B-axis normal swing angle, as shown in fig. 4.
The invention ensures that the measuring head always carries out raster scanning along the normal direction of a workpiece according to a designed measuring path in the measuring process by means of an ultra-precise five-axis linkage processing machine tool, a spectrum copolymerization Jiao Weiyi sensor and a high-precision detachable in-situ measuring clamp and by precisely controlling and feeding back the rotation angle of the B axis and controlling the linkage of the X\Y\Z\B four axes, thereby directly obtaining the shape error of each measuring point of the measured workpiece. Meanwhile, the FPGA board card controller is developed and connected with a machine tool data output interface to acquire coordinate information of a machine tool PMAC control card, and signal output is realized through software, so that real-time acquisition of coordinate positions is realized, and all acquisition and motion control are synchronously performed. The in-situ measurement method and the in-situ measurement system can directly acquire the surface shape error of the measured surface, thereby realizing large-range high-precision measurement of the small-range sensor, avoiding the influence of the measurement angle on the measurement precision in the non-contact measurement process in a normal measurement mode, avoiding the later-stage surface shape matching processing and error analysis of the measurement data, and simultaneously improving the measurement efficiency while ensuring the measurement precision because a traditional active detection measurement mode of a coordinate measuring instrument is not adopted; and the measurement data can be controlled by the density degree of the design of the measurement path, so that the measurement is flexible.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A normal measurement method of a large-curvature free-form surface is characterized by comprising the following steps:
step 1, mounting a measuring device on a B axis of a five-axis machining center so that a measuring head of the measuring device
Focusing a laser spot at the position of the rotation center of the B axis;
step 2, installing a workpiece on a C shaft of a five-shaft machining center;
step 3, determining origin coordinates of a measuring head origin of a measuring device at the center of a workpiece;
step 4, the data acquisition device, the measuring device and the X/Y/Z/B/C shaft of the five-shaft machining center are combined
The output interface of the grating signal is connected;
step 5, generating a free-form surface normal swing grating type measuring path according to the origin coordinates of the origin of the measuring head, which are determined in the step 3, at the center of the workpiece, the position coordinates of the discrete points of the free-form surface and the B-axis normal swing angle; the measuring head in the path is driven by X/Z/B three-axis linkage to scan the outline along the free curved surface, and the distance between the measuring head and the free curved surface in the normal vector direction is always the focal length of the measuring head in the scanning process; every time one line of scanning is completed, the measuring head is fed in the Y-axis direction according to a given step length, and then the contour scanning of the next line is completed;
the B-axis normal swing angleThe following are provided:
(1)
in the method, in the process of the invention,and->Is normal direction of discrete points of free curved surface in X and Z directionsAmount of the components.
2. The method of claim 1, wherein the measuring device is mounted on the B-axis by a fixture.
3. The method of claim 2, wherein the fixture comprises an upper base, a lower base and a clamping device, wherein a positioning ball column is arranged on the top of the lower base, the upper base is arranged on the positioning ball column, and the clamping device is fixed on the upper base.
4. The method of claim 1, wherein the measuring device is a spectral copolymer Jiao Weiyi sensor.
5. The method for normal measurement of a large curvature free-form surface according to claim 1, wherein the data acquisition device is an FPGA board controller.
6. The method for measuring the normal direction of the large-curvature free-form surface according to claim 5, wherein the FPGA board card controller is respectively provided with X/Y/Z/B/C ports; the X/Y/Z/B/C port is connected with an output interface of a grating signal subdivision box of an X/Y/Z/B/C axis of the five-axis machining center; and a sensor trigger port on the FPGA board controller is connected with a controller port of the measuring device.
7. A method of measuring a large curvature free-form surface normal direction according to claim 1, wherein the laser spot focusing position of the probe is adjusted in step 1 using an optical tool setting gauge and a rotary dipstick.
8. The method of claim 1, wherein the specific process of step 3 is as follows:
moving X-axis and Y-axis of machine tool to excite measuring headThe light origin is adjusted to the central position of the workpiece, and then the coordinates of the central position are calibrated; taking the central position coordinate as the origin of coordinatesTwo symmetrical points are respectively taken in the X direction and the Y direction of the free curved surface>、 />And->、 />The method comprises the steps of carrying out a first treatment on the surface of the When the X-direction measurement origin is calibrated, two symmetrical points are respectively measured by using the measuring head>And->Calculating the X-direction origin offset from the error value>Correcting the origin of the measuring center to be +.>According to the corrected measurement origin coordinates +.>Recalculating the position coordinates of two symmetrical points at the same position of the free curved surface>、 />Re-measuring the two symmetrical points, calculating the origin offset in the X direction>Correcting the origin of the measuring center again to obtain +.>The calibration process is iterated a plurality of times until the origin offset in the X direction is less than 1 μm, at which point the origin coordinates are +.>；
Repeating the steps, calibrating the origin of the Y-axis direction until the offset of the origin of the Y-axis direction is smaller than 1 mu m, and finally obtaining the origin coordinate measured by the measuring head as follows。
9. The method for measuring the normal direction of the free-form surface with large curvature according to claim 1, wherein the position coordinates of the discrete points of the free-form surface are obtained by the following steps: and vertically projecting the free-form surface onto an XY plane, forming a rectangular area by the maximum value and the minimum value, carrying out grid division on the rectangular area to obtain (x, y) coordinates, and obtaining corresponding Z-axis coordinate values for each grid coordinate point (x, y), namely obtaining a one-to-one single-value function relation for points on the XY plane and Z-axis height values, wherein the free-form surface is expressed as a three-dimensional discrete point cloud (x, y, Z).
Priority Applications (1)
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