CN102607483A - Cylindrical coordinate contact measurement method for large-diameter optical aspheric element - Google Patents

Abstract

The invention discloses a cylindrical coordinate contact measurement method for a large-diameter optical aspheric element by collecting two-dimensional or three-dimensional data by using a measuring machine by adopting the cylindrical coordinate measurement method. The cylindrical coordinate contact measurement method for the large-diameter optical aspheric element comprises the following steps: S1, aligning the center of a rotating platform surface and the center of a length meter by using an inductance micrometer; S2, aligning a workpiece by using the inductance micrometer; S3, determining a reference coordinate, moving the X axis so as to move the length meter to the edge of the workpiece to determine a starting point, and comparing the movement amount with the reference coordinate to determine the measurement stroke L; and S4, establishing a workpiece coordinate system and a measurement coordinate system by using the measuring machine, determining the two-dimensional or three-dimensional measurement, and collecting data to obtain the needed coordinate point. By using the ultraprecise shape measuring machine, the measurement and the assessment after the milling and the grinding of the large-diameter aspheric element can be realized, and the two-dimensional or three-dimensional error assessment of the workpiece can be realized. The measuring process is easy to operate, the cylindrical coordinate contact measurement method has high efficiency, and the measuring path is easy to implement.

Description

Cylindrical Coordinate Contact Measurement Method for Large Aperture Optical Aspheric Components

【Technical field】

The invention belongs to the technical field of precision measurement, in particular to a contact measurement method of a large-caliber optical aspheric element.

【Background technique】

Large-scale space telescopes in space optics use secondary aspheric mirrors, high-power laser devices in laser nuclear fusion use multiple aspheric surfaces, and space cameras, aerospace remote sensing, and large-aperture night vision devices all use high-precision large-aperture aspheric elements. With the improvement of space technology and national defense technology, the demand for large-diameter aspheric components is increasing. Large-volume, high-efficiency, and high-precision manufacturing of optical aspheric components requires high-precision measurement to guide the processing process. Subsequently, the measurement process must be high in efficiency, high in precision, and the error evaluation method is reliable and fast. Aspherical surface measurement technology has always restricted the development of aspheric surface applications. Non-contact measurement methods cannot be used for milled aspheric surface components, because the surface shape accuracy cannot meet the requirements of interferometric measurement, so the measurement is all by contact measurement. method. The contact measurement of large-diameter aspheric surfaces mainly includes three-coordinate measurement and splicing measurement technology. Three-coordinate measuring instruments have many error sources, low measurement accuracy, and high-precision three-coordinate measuring instruments are expensive. Foreign countries mainly use Germany for the measurement of large-diameter aspheric surfaces. Leitz three-coordinate measuring instrument CMM; splicing measurement is measured by adding a third link, and then the measurement data is analyzed and processed, so the accuracy of the measurement results obtained is not high.

Developed an efficient and high-precision measuring method and a fast centering method for the ultra-precision shape measuring instrument-cylindrical coordinate measuring instrument, to realize the measurement and evaluation of the surface shape after milling and grinding of large-diameter aspheric surfaces, aiming to solve the problem of diameters of 500-1000mm Measurement of large aperture aspheric optical components.

【Content of invention】

The object of the present invention is to provide a cylindrical coordinate contact measurement method for large-diameter optical aspheric elements, which is used for measuring and evaluating the surface shape of large-diameter aspheric elements after milling; the cylindrical coordinate system is used to establish the workpiece coordinate system and measure Coordinate system, fast sampling of data through high-precision touch probe.

In order to achieve the above object, the present invention adopts the following technical solutions:

A cylindrical coordinate contact measurement method for a large-diameter optical aspheric element, using a measuring machine to collect two-dimensional or three-dimensional data through a cylindrical coordinate measurement method; including the following steps:

Step S1: Use an inductance micrometer to align the center of the rotating table and the center of the length gauge so that the upper and lower centers are concentric, and the concentricity accuracy is guaranteed to be 0.1 μm;

Step S2: Align the workpiece with an inductance micrometer, extend the length gauge, record the extension of the length gauge, and record the X-axis coordinate value at the same time, and use the coordinate of this point as the reference coordinate (x ₀ , z ₀ );

Step S3: After determining the reference coordinates, move the X-axis to move the length gauge to the edge of the workpiece to determine the starting point, and compare the movement amount with the reference coordinates to determine the measurement stroke L;

Step S4: Establish a workpiece coordinate system and a measurement coordinate system according to the measuring machine, determine two-dimensional measurement or three-dimensional measurement, and perform data collection to obtain required coordinate points.

The further improvement of the present invention lies in that: in step S1, the center of the rotating table and the length gauge is first found, and then the workpiece is adjusted to the center by an inductance micrometer.

The further improvement of the present invention is that step S1 specifically includes the following steps: fixing the measuring head of the inductance micrometer on the surface of the watch base, fixing the watch base to any position on the turntable surface where measurement can be realized, and turning the measuring head of the inductance micrometer Go to the end of the length gauge, adjust the centering mechanism of the rotating work through the turntable; adjust the inductance micrometer to the 0.01μm range, and adjust the error to within 0.1μm, which is alignment.

The further improvement of the present invention lies in: during the two-dimensional measurement process, the X-axis component drives the length meter to move along the X-axis direction to realize the movement of measuring the step distance, and the length meter stretches out to collect data every time a step distance is taken, and N coordinate points are obtained (x _i , z _i ), i=1...N; in the three-dimensional measurement process, the number of measurement steps per circle is n1, and the measurement step distance is n2. Starting from the first point, the turntable rotates an angle θ=360 /n1, the length gauge stretches out to sample once, after measuring a circle, find the starting position, the turntable moves a measurement step along the X-axis direction until the measurement process is completed, and n1×n2 coordinate points (x _ij , z _ij , θ _ij ), i=1...n1, j=1...n2.

The further improvement of the present invention is that: the measuring machine includes natural granite bed, X-axis parts, Z-axis parts and self-aligning and leveling device; and the first linear motor; the auxiliary gas static pressure guide rail and the main gas static pressure guide rail are clamped on both sides of the natural granite bed; the two ends of the elliptical arc gantry are welded, one end is fixed on the auxiliary gas static pressure guide rail, and the other end Fixed on the main gas static pressure guide rail; Z-axis components include octagonal granite guide column, V-shaped air bearing block, length gauge and second linear motor; two V-shaped air bearing blocks are connected by bolts on the welded elliptical arc gantry on the frame, used to adjust the verticality of the Z axis; the octagonal granite guide column 7 and the symmetrically connected double V-shaped air bearing blocks form a gas static pressure guide rail pair, which realizes the up and down movement of the Z axis; the secondary linear motor The primary coil is fixedly connected to the welded elliptical arc gantry frame, and the primary coil is connected to the granite guide column; the length gauge is fixed in the inner cavity of the granite guide column; the centering and leveling device includes the turntable surface, the universal leveling plate, and the static pressure plate under the turntable And the drive unit that drives the static pressure plate under the turntable to rotate; the static pressure plate under the turntable and the natural granite bed are supported by gas static pressure bearings.

The further improvement of the present invention is that: the auxiliary gas static pressure guide rail and the main gas static pressure guide rail are provided with an inflation interface, and when the X-axis components move, the auxiliary gas static pressure guide rail and the main gas static pressure guide rail are inflated through the inflation interface to make the auxiliary gas static pressure guide rail An air film is formed between the hydrostatic guideway, the main gas hydrostatic guideway and the top and side surfaces of the natural granite bed.

The further improvement of the present invention is that: the main gas static pressure guide rail is driven by the X-axis linear motor to drive the welded elliptical arc gantry to move along the guide rail surface of the natural granite bed.

The further improvement of the present invention is that: the centering and leveling device also includes several leveling devices and centering devices; the top of the static pressure plate under the turntable is provided with a concave spherical surface and several symmetrically arranged grooves; There is a convex spherical surface and a conical inclined surface; the universal leveling plate is installed on the top of the static pressure plate under the turntable, and the convex spherical surface of the universal leveling plate matches the concave spherical surface of the static pressure plate under the turntable; the leveling device includes a leveling positioning plate , leveling screw, leveling pulley, leveling pulley shaft and leveling support; the leveling support is installed in the corresponding groove on the static pressure plate under the turntable, and can move along the groove of the static pressure plate under the turntable The shaft of the leveling pulley connects the leveling pulley to the leveling support; the leveling screw rod is threadedly matched with the leveling support; On the leveling plate; the side of the turntable surface is symmetrically provided with several threaded through holes, and several self-aligning jackscrews are arranged in the corresponding threaded through holes and threadedly connected with the turntable surface.

The further improvement of the present invention lies in that the cross-section of the head of the leveling screw is trapezoidal, the leveling positioning plate presses the head of the leveling screw, and then is fastened to the lower static pressure plate by bolts, so that the leveling screw can only rotate, It cannot move axially; the side circumference of the universal leveling plate is provided with a circumferential surface, and the tips of several self-aligning jackscrews pass through the corresponding threaded holes to resist the circumferential surface.

The further improvement of the present invention is that: a mounting hole is provided in the center of the natural granite bed, and the hemispherical seat is fixed in the mounting hole; the hemispherical graphite tile is fixed on the hemispherical seat; On the static pressure plate under the turntable; the convex spherical surface of the hemispherical shaft matches the concave spherical surface of the hemispherical graphite tile; the bottom surface of the static pressure plate under the turntable is provided with an annular groove, and several pieces of flat supporting graphite are evenly fixed in the annular groove block; planar support graphite block and natural granite bed form an aerostatic bearing pair.

The further improvement of the present invention is that: the precision large-diameter aspheric shape measuring machine also includes a first gas path and a second gas path; the first gas path is connected to the hemispherical graphite tile, and the pressure gas is passed into the hemispherical graphite tile. A gas film is formed between the hemispherical graphite tile and the hemispherical axis; the second gas path is connected to the several plane-supported graphite blocks, and the pressure gas passes into the plane-supported graphite blocks to form a gas film between the plane-supported graphite blocks and the natural granite bed. membrane.

The further improvement of the present invention lies in: the welded elliptical arc gantry includes a front plate and a rear plate; the front plate and the rear plate are welded and fixed together by several symmetrically arranged stiffener plates; the lower edges of the front plate and the rear plate Includes semi-elliptical arc segments.

The further improvement of the present invention is that: the drive unit includes a pulley, a reducer and a servo motor; the servo motor is connected with the pulley through the reducer.

The further improvement of the present invention is that: the thickness of the gas film is 3-5 μm.

Compared with the prior art, the beneficial effect of the present invention is that: the present invention can be used for measurement and evaluation of large-diameter aspheric elements after milling and grinding through an ultra-precision measuring machine, and can realize two-dimensional and three-dimensional error evaluation of workpieces. The measurement process is easy to operate, the measurement method is efficient, and the measurement path is easy to realize.

【Description of drawings】

Fig. 1 is the front view of the ultra-precision large-caliber aspheric shape measuring machine of the present invention;

Fig. 2 is a side view of the ultra-precision large-caliber aspheric shape measuring machine shown in Fig. 1;

Fig. 3 is the schematic structural view of the self-aligning and leveling device of the present invention;

Fig. 4 is a partial enlarged view of part A in Fig. 3;

Fig. 5 is a structural schematic diagram of the hemispherical centering planar support turntable of the present invention;

Fig. 6 is the top view of the welded elliptical arc gantry of the present invention;

Fig. 7 is the front view of the welded elliptical arc gantry of the present invention;

Fig. 8 is a schematic diagram of the measuring machine of the present invention after placing the element to be measured;

Figure 9a and Figure 9b are schematic diagrams of the data acquisition path of the large-aperture aspheric element;

Figure 10 is a schematic diagram of the working principle of the alignment center;

Fig. 11 is a schematic diagram of determining the measurement reference coordinate value and the measurement stroke.

【Detailed ways】

The present invention is described in further detail below in conjunction with accompanying drawing:

Please refer to FIG. 1 to FIG. 7 , which are structural schematic diagrams of an ultra-precision large-caliber aspheric shape measuring machine used in the measuring method of the present invention.

Please refer to Fig. 1 and Fig. 2, an ultra-precision large-diameter aspheric shape measuring machine of the present invention includes a natural granite bed 1, an auxiliary gas static pressure guide rail 2, a mass balance block 3, a welded elliptical arc gantry 4, Steel belt roller 5, steel belt 6, granite guide column 7, V-shaped air bearing block 8, length gauge 9, positioning mandrel 10, turntable surface 11, universal leveling plate 12, static pressure plate under turntable 13, main Gas static pressure guide rail 14, turntable mandrel 15, pulley 16, reducer 17, servo motor 18, X-axis linear motor 19 and Z-axis linear motor 20.

The X-axis components of the ultra-precision large-diameter aspheric shape measuring machine of the present invention are mainly composed of auxiliary gas static pressure guide rail 2, welded elliptical arc gantry frame 4, main gas static pressure guide rail 14 and X-axis linear motor 19. The auxiliary gas static pressure guide rail 2 and the main gas static pressure guide rail 14 have an L-shaped cross section, and are clamped on both sides of the natural granite bed 1; the two ends of the elliptical arc gantry 4 are welded, and one end is fixed on the auxiliary gas static pressure guide rail 2 The other end is fixed on the main gas static pressure guide rail 14; the auxiliary gas static pressure guide rail 2 and the main gas static pressure guide rail 14 are provided with an inflation interface, and when the X-axis components move, the auxiliary gas static pressure guide rail 2 and the main gas static pressure guide rail 2 are fed through the inflation interface. The gas static pressure guide rail 14 is inflated, so that an air film is formed between the auxiliary gas static pressure guide rail 2, the main gas static pressure guide rail 14 and the top surface and the side of the natural granite bed 1. The main gas static pressure guide rail 14 is driven by the X-axis linear motor 19, and drives the welded elliptical arc gantry 4 to move along the guide rail surface of the natural granite bed 1. The bearing materials of the main and auxiliary gas static pressure guide rails 14 and 2 are all made of porous graphite, which has uniform pores and can form a gas film with uniform thickness and stable motion performance. The air film thickness of the ultra-precision gas static pressure is 4-5 μm, which ensures the rigidity of the air film and the stability of the guide rail. The X-axis driving unit adopts a U-shaped X-axis linear motor 19, and the closed-loop measuring element adopts a high-precision grating linear displacement sensor with a resolution of 0.1 μm.

The Z-axis components of the ultra-precision large-diameter aspheric shape measuring machine of the present invention are mainly composed of a mass balance block 3, a steel belt roller 5, a steel belt 6, a granite guide column 7, a V-shaped air bearing block 8, a length gauge 9 and a Z-axis straight line The motor 20 constitutes. Two V-shaped air bearing blocks 8 are connected to the welded elliptical arc gantry 4 by four bolts, which can be slightly adjusted in the horizontal direction to adjust the verticality of the Z axis. The octagonal granite guide column 7 and the symmetrically connected double V-shaped air bearing blocks 8 form a gas static pressure guide rail pair to realize the up and down movement of the Z axis; the angular granite guide column 7 has good torsional stability. The Z-axis drive unit adopts a U-shaped Z-axis linear motor 20, the secondary coil of the motor 20 is fixedly connected with the welded elliptical arc gantry 4, and the primary coil is connected with the granite guide post 7, and a high-precision linear grating is pasted on the granite guide post 7 ruler to realize high-precision displacement measurement of the Z-axis, and finally realize high-precision feed movement of the Z-axis through measurement feedback. The Z-axis measuring head length meter 9 is fixed in the inner cavity of the granite guide column 7, and its linear displacement resolution is 0.μm. Cooperating with the Z-axis system, the comprehensive measurement accuracy is ±0.5μm. Since the Z-axis is installed vertically, using the mass balance block 3 to balance the moving weight of the Z-axis components can reduce the load of the Z-axis linear motor 20 and improve the accuracy of the feed system. The mass balance block 3 is connected by a steel belt 6, and the other end of the steel belt 6 is fixed on the end of the granite guide column 7, and moves around two steel belt rollers 5, finally realizing the high-precision and smooth movement of the Z-axis components.

The natural granite bed 1 of the ultra-precision large-diameter aspheric shape measuring machine of the present invention is installed in a three-point support mode, and the X-axis components are supported on the natural granite bed 1 by the main gas static pressure guide rail 14 and the auxiliary gas static pressure guide rail 2, The Z-axis component is connected to the welded elliptical arc gantry 4 of the X-axis component through four adjustable bolts, so that small adjustments in the horizontal direction can be realized. The static pressure plate 13 under the turntable of the self-aligning and leveling turntable component and the natural granite bed 1 are supported by gas static pressure bearings to achieve high-precision rotation accuracy.

The main features of the self-aligning and leveling turntable of the ultra-precision large-diameter aspheric shape measuring machine of the present invention are large bearing capacity (parts mass 260Kg), high precision of the turntable, and high-precision centering and leveling functions of the turntable. The centering and leveling turntable is mainly composed of a positioning mandrel 10, a turntable surface 11, a universal leveling plate 12, a static pressure plate under the turntable 13, a turntable mandrel 15, a pulley 16, a reducer 17 and a servo motor 18. The static pressure plate 13 under the turntable and the natural granite bed 1 are supported by gas static pressure bearings to achieve high-precision rotation accuracy. When aligning, the positioning mandrel 10 is fixed at the center hole of the turntable, and the top of the positioning mandrel 10 is provided with a centering hole, which is used to assist in adjusting the concentricity between the center of the turntable and the measuring head of the length meter 9, and the positioning mandrel is removed during measurement 10. The centering and leveling function of the turntable is mainly realized by the positioning mandrel 10, the turntable surface 11, the universal leveling plate 12, and the static pressure plate 13 under the turntable. Centering and leveling, and has self-aligning, leveling and self-locking functions, which break through the traditional centering and leveling functions of large-diameter and heavy-duty turntables, and can realize the three-dimensional tilting and two-dimensional adjustable functions of the turntable, which improves the measurement accuracy. The drive unit of the turntable components adopts the combination of servo motor 18, reducer 17 and belt pulley 16 to drive the turntable mandrel 15 to rotate, thereby driving the whole turntable to realize low-speed and stable movement. The turntable is equipped with a high-precision circular grating for angle measurement feedback, which can realize the high-precision indexing function of the turntable. The self-aligning and leveling turntable part is the core part of the ultra-precision large-caliber aspheric shape measuring machine, which has the characteristics of low-speed stability, high rotation accuracy and large bearing capacity.

Please refer to Fig. 3 and shown in Fig. 4, the self-aligning and leveling device of the present invention comprises the static pressure plate 13 under the turntable, the leveling positioning plate 22, the self-aligning top screw 23, the turntable table top 11, the leveling screw rod 25, the Smooth wheel 26, leveling smooth wheel shaft 27, leveling support 28, positioning mandrel 10, universal leveling plate 12.

Four leveling supports 28 are installed in four grooves on the static pressure plate 13 under the turntable, and can move along the grooves on the static pressure plate 13 under the turntable. The leveling pulley shaft 27 connects the leveling pulley 26 to the leveling support 28, and the leveling support 28 is threadedly connected with the leveling screw rod 25, and the leveling screw rod 25 is installed on the static pressure plate 13 under the turntable, and the leveling screw rod 25 can be Rotate, and perform leveling and positioning through the leveling positioning plate 22, and the leveling positioning plate 22 is fixed on the static pressure plate 13 under the turntable by screws. The cross-section of the head of the leveling screw 25 is trapezoidal, and the leveling positioning plate 22 presses the head of the leveling screw 25, and then is fastened to the lower static pressure plate 13 by bolts to restrict the axial direction of the leveling screw 25, so that The leveling screw rod 25 can only rotate, but cannot move axially.

The bottom periphery of the universal leveling plate 12 is a spherical surface 101, which is installed on the concave spherical surface 110 of the static pressure plate 13 under the turntable; the center of the bottom of the universal leveling plate 12 is provided with a conical slope 102; the leveling pulley 26 can be Sliding on the tapered slope 102 of the universal leveling plate 12 , by adjusting the four leveling pulleys 26 , the universal leveling plate 12 can be tilted three-dimensionally. The lower mounting surface of the turntable table top 11 is directly installed on the universal leveling plate 12. The upper convex spherical surface of the universal leveling plate 12 is provided with a circumferential surface 103, and four self-aligning jackscrews 23 arranged at intervals of 90 degrees are threaded to adjust the turntable table surface. 11 connected; the self-aligning jackscrew 23 withstands the circumferential surface 103 of the universal leveling plate 12, and by adjusting the four self-aligning jacking screws 23, the turntable table top 11 can be moved two-dimensionally to realize the centering function of the turntable. The positioning mandrel 10 is matched with the center hole of the turntable table surface 11 and fixed by screws; the top of the positioning mandrel 10 is provided with a positioning hole for centering.

The universal leveling plate 12 will carry all the mass of the turntable and parts, and is structurally designed as a convex spherical surface 101, which cooperates with the concave spherical surface 110 of the static pressure plate 13 under the turntable to play a main supporting role. In order to increase the contact area, during assembly, the convex spherical surface 101 of the universal leveling plate 12 and the concave spherical surface 110 of the static pressure plate 13 under the turntable are matched and ground to obtain good contact area and surface shape accuracy. In order to realize the leveling function of the turntable, the lower end surface of the universal leveling plate 12 is designed as a slope structure, and the tilting motion of the universal leveling plate 12 is realized through the relative movement between the slope and the leveling pulley 26 .

The static pressure plate 13 under the turntable is the bearing part of the whole self-aligning and leveling device, and its upper end surface is designed with a concave spherical surface 110, which cooperates with the convex spherical surface 101 of the universal leveling plate 12 to bear the main mass. On the static pressure plate 13 under the turntable, there are 4 mutually perpendicular grooves, which can ensure that the leveling support 28 moves along a certain direction (the direction of the groove), which improves the leveling accuracy; the four grooves The slots are set at intervals of 90 degrees.

Leveling device is made up of leveling positioning plate 22, leveling screw rod 25, leveling pulley 26, leveling pulley axle 27 and leveling bearing 28. There are four leveling devices, which are evenly distributed, and the adjacent intervals are 90°. The leveling devices are installed on the static pressure plate 13 under the turntable and can move along the grooves on the static pressure plate 13 under the turntable. By rotating the adjusting screw rod 25, because the leveling positioning disc 22 is positioned in the axial direction of the adjusting screw rod 25, it cannot move, so that the leveling support 28 moves along the groove with the leveling pulley 26 and the leveling pulley shaft 27. The convex spherical surface 101 of the universal leveling plate 12 cooperates with the concave spherical surface 110 of the static pressure plate 13 under the turntable. When the leveling pulley 26 slides back and forth on the slope of the universal leveling plate 12, by adjusting a leveling support 28, The remaining three leveling supports 28 are stationary, and the universal leveling plate 12 can tilt and move to realize the leveling function of the turntable components.

The centering device is made up of centering jackscrew 23 , turntable table top 11 and positioning mandrel 10 . The lower mounting surface of the turntable table 11 is directly installed on the universal leveling plate 12, the four self-aligning jackscrews 23 are connected with the turntable table 11 through threads, the positioning mandrel 10 is matched with the center hole of the turntable table 11, and fixed by screws, The center position of the turntable table surface 11 can be obtained. By adjusting the four self-aligning jackscrews 23, the turntable surface 11 can be moved two-dimensionally. When the center hole at the end of the positioning mandrel 10 coincides with the central axis of the measuring head, the centering function of the turntable is realized.

Please refer to shown in Fig. 5, the hemispherical centering planar support turntable structure of the present invention comprises natural granite bed 1, planar support graphite block 32, static pressure plate 13 under the turntable, hemispherical seat 34, hemispherical graphite tile 35, turntable mandrel 15 and hemispherical shaft 37.

The hemispherical centering structure is made up of hemispherical seat 34, hemispherical shaft 37, turntable mandrel 15 and hemispherical graphite tile 35. The center of the natural granite bed 1 is provided with a trapezoidal mounting hole, and the hemispherical seat 34 is fixed in the trapezoidal mounting hole of the natural granite bed 1 by screws, and the hemispherical graphite tile 35 is bonded on the hemispherical seat 34 by epoxy resin. A through hole is arranged in the center of the hemispherical shaft 37, and the turntable mandrel 15 is installed in the through hole, and the hemispherical shaft 37 and the turntable mandrel 15 are fixed to the static pressure plate 13 under the turntable by screws. The servo motor 18 is connected to the turntable mandrel 15 through the reducer 17 and the pulley 16, and drives the turntable mandrel 15 to rotate, thereby driving the lower static pressure plate 13 of the turntable to rotate together. The hemispherical shaft 37 and the hemispherical graphite tile 35 are matched and ground to obtain a uniform fit gap, and the pressure gas is passed into the hemispherical graphite tile 35 to form a 3-5 μm gas film between the hemispherical graphite tile 35 and the hemispherical shaft 37. Play a reassuring role.

The planar support structure is composed of a natural granite bed 1, a static pressure plate 13 under the turntable and a planar support graphite block 32, and 12 planar support graphite blocks 32 are glued in the annular groove of the static pressure plate 13 under the turntable by epoxy resin. Evenly distribute the static pressure plate 13 under the turntable for a week, and form a gas static pressure bearing pair with the natural granite bed 1. The compressed gas communicates with the axial air hole of the static pressure plate 13 under the turntable through the air hole of the mandrel shaft 15 of the turntable, and sends the gas into the horizontal air hole of the static pressure plate 13 under the turntable, and then is the same as the vertical air hole in the center of the ring groove. After entering the ring groove, it is distributed through the air groove on the planar support graphite block 32 and then flows out from the tiny pores of the graphite. A layer of 3-5 μm gas film is formed between the plane support graphite block 32 and the joint surface of the natural granite bed 1 to realize the plane support function of the gas static pressure turntable.

The present invention is used for the hemispherical centering planar support turntable structure of large-diameter ultra-precision measuring machines. The air film gap can get the required bearing capacity, rigidity and precision. This invention combines the turntable structure with hemispherical centering and plane support with gas static pressure bearing support technology, and adopts the research technology in the assembly process, and finally realizes the functions of high precision, high rigidity and large bearing capacity of the turntable of the measuring machine.

The turntable structure of the present invention uses a small-sized hemispherical shaft for centering, a large-sized plane guide rail as a bearing plane, and an aerostatic bearing as a supporting bearing for the hemispherical shaft and the plane. The hemispherical shaft of the turntable only plays the role of centering, and bears a small load, which ensures the centering accuracy of the hemispherical shaft to the turntable; the large-size plane bearing can bear the weight of the turntable and large-sized parts, thereby ensuring the accuracy and carrying capacity of the turntable, and finally realizes Ultra-precision measuring machine for high-precision and high-rigidity measurements.

Please refer to Fig. 6 and shown in Fig. 7, welding ellipse arc gantry frame 4 of the present invention comprises ellipse arc gantry welding frame bottom plate 41,43, stiffener plate 47,49,412,414, main structure front plate 42, shape welding Reinforcement plates 44, 45, 415, 416, main structure rear plate 46, connecting plates 410, 411, shape protection plates 48, 413.

The two ends corresponding to the front plate 42 of the main structure and the rear plate 46 of the main structure are welded together through the bottom plate 41 and the bottom plate 43 respectively; the front plate 42 of the main structure and the rear plate 46 of the main structure are symmetrically welded with stiffener plates 47, 49, 412 , 414; The two ends corresponding to the main structure front plate 42 and the main structure rear plate 46 are also welded with profile welding reinforcement plates 44, 45 and profile welding reinforcement plates 415, 416 respectively; the main structure front plate 42 and the main structure rear plate 46 The upper side and the lower side of the upper and lower sides are respectively fixed with shape protection plates 48,413 by screws. A square hole for installing the measuring machine is formed between the stiffener plates 49, 412, the main structure front plate 42 and the main structure rear plate 46, and a connecting plate 410 welded on the rear plate 46 for fixing the measuring machine is arranged in the square hole , 411. The lower edges of the main structure front plate 42 and the main structure rear plate 46 include a semi-elliptical arc segment and two straight line segments tangent to the apex of the long axis of the semi-elliptical arc, where reinforcement plates 415 and 416 are respectively welded.

The invention relates to an elliptical arc gantry structure used in a measuring machine for large-diameter parts, which can be used for measuring the shape accuracy of large-diameter parts (the diameter of the parts is less than Φ900mm). Its structure is connected with the linear motion guide rail of the measuring machine through the bottom plates 41 and 43 of the elliptical arc gantry welding frame, so as to drive the gantry structure to move. The vertical axis of the measuring machine is installed on the connecting plates 410 and 411 of the elliptical arc gantry structure, and can realize small adjustments in the horizontal direction.

The thickness of the welded bottom plates 41 and 43 is 10mm, and the material is 45 steel, and the flatness is required to reach 5μm. After a certain period of aging after welding, the bottom surface should be polished to ensure the surface shape accuracy of the contact surface.

Rib plates 47, 49, 412, and 414 are 10mm thick, made of 45 steel, and have hollow circles in the middle of the sheet metal. On the one hand, the weight is reduced, and on the other hand, it is convenient to arrange the electrical circuits of the measuring machine in the middle of the sheet metal. The rib plate is welded together with the main structure of the elliptical arc gantry by welding process. Its main function is to strengthen the strength and rigidity of the elliptical arc gantry, so as to improve the precision retention and stability of the elliptical arc gantry structure.

The front plate 42 of the main structure and the rear plate 46 of the main structure are the main body of the elliptical arc gantry structure, and the strength and rigidity of the gantry structure are mainly guaranteed by the materials, dimensions and welding process of the two plates. The thickness of the front plate 42 and the rear plate 46 is 10 mm, the material is 45 steel, and aging treatment is carried out after welding. Since the measuring vertical axis is installed on the elliptical arc gantry structure, the overall performance of the gantry structure is very high, and high dimensional accuracy and welding technology are required to ensure the strength and rigidity of the main structure.

The shape welding reinforcing plates 44, 45, 415, 416 connect the front plate 42 of the main structure and the rear plate 46 of the main structure together through welding process, and play the role of supporting and fixing. Heat treatment will be carried out to the shape welding reinforcing plates 44, 45, 415, 416 after they are cut and formed.

The connecting plates 410, 411 are welded on the rear plate 46 of the main structure, and are used for installing and fixing the vertical shaft. The flatness of the two plates (410, 411) in the vertical direction is 5 μm. To ensure that the contact surfaces of the two plates and the vertical axis are on the same plane, the verticality of the vertical axis and the worktable can be ensured.

The shape protection plates 48 and 413 play a protective role in the entire elliptical gantry structure, and protect the internal structure, pipelines and electrical circuits of the elliptical gantry structure. The shape protection plates 48, 413 are fixed on the main structure of the elliptical arc gantry by small screws.

The elliptical arc gantry structure of the present invention, through its semi-elliptical arc structure, well reduces the stress concentration at the entry point of the arc and improves the stability of the gantry structure. Compared with the granite column gantry structure and semi-circular structure with the same span, the elliptical arc gantry structure has the advantages of small space occupation and light weight, and is more suitable for the gantry structure of high-precision measuring machines. Because the force of the elliptical arc gantry structure is relatively uniform, the gantry has a longer service life and accuracy retention. The elliptical arc gantry structure adopts welding technology, which makes the design of welded parts more flexible, and can be welded into more complex structures according to different needs, while also meeting the requirements of ergonomics.

In the ellipse-arc gantry structure of the present invention, the upright column and the cross beam are designed to be integrated, which reduces the transmission of errors and is beneficial to improving the measurement accuracy of the measuring machine. The gantry structure has the characteristics of uniform force, small stress concentration, high strength and rigidity, good structural stability, light moving mass, small inertia and low energy consumption of the motor, and has good precision retention.

The innovation of the elliptical arc gantry structure of the present invention is that it adopts a welded gantry structure instead of traditional cast iron or granite columns and beams, and at the same time adopts an elliptical arc gantry structure suitable for the measuring machine structure on the basis of the traditional welded structure. Half an ellipse Compared with the semi-circular arc shape, the arc shape is more suitable for the structure of the measuring machine, and there is no stress concentration at the entry point of the elliptical arc, which ensures the life and precision of the gantry structure well. It is also a good innovation to the appearance of the traditional measuring machine. It combines the function of the measuring machine with ergonomics well, so that the measuring machine can meet the human visual effect and the rationality of operation while realizing the function.

The measuring machine adopts an elliptical arc gantry structure. The major axis and minor axis of the ellipse are determined according to the size of the measuring machine to form a semi-elliptical arc. The steel plate is shaped and cut with a laser cutting machine. The main components of the gantry frame and the necessary The reinforcing ribs are welded and formed; after aging treatment, the welding stress is released, and then the gantry is trimmed to achieve the accuracy required by the measuring machine, and the processing technology of the gantry is completed.

The invention realizes the specialized detection equipment of the large-caliber aspheric element, and at the same time plays a huge role in promoting and promoting the further development and research of the detection equipment of the large-diameter optical element.

Please refer to Figure 8 and Figure 10, which are the schematic diagrams of the mechanical alignment of the measuring machine. The center of the length meter 9 and the center of the turntable surface 11 are aligned. The key is to shorten the eccentric adjustment time after the workpiece is placed on the turntable surface 11. For columns Finding a coordinate measurement system is a relatively complicated implementation process.

The specific implementation is as follows: fix the probe 100 of the inductance micrometer on the table base 200, and fix the base 200 on the turntable surface 11 at any position where measurement can be realized, and place the probe 100 of the inductance micrometer on the 9 end of the length gauge Adjust the centering mechanism of the rotating work through the turntable surface 11; adjust the inductance micrometer to the 0.01 μm range, and adjust the error to within 0.1 μm (meeting the measurement accuracy requirements), that is, it is considered to be aligned.

Fig. 9 is a schematic diagram of a measurement path, wherein Fig. 9a is a schematic diagram of a two-dimensional measurement path, and Fig. 9b is a schematic diagram of a three-dimensional measurement path. P shown in the figure is the measurement step distance, and θ is the measurement angle interval. During the two-dimensional measurement process, the X-axis drives the length meter 9 to move along the X direction to realize the movement of the measurement step. Every time a step is taken, the length meter 9 stretches out to collect data once, and N coordinate points (x _i , z _i ), i=1...N. In the three-dimensional measurement process, the number of measurement steps per circle is n1, and the measurement step distance is n2. Starting from the first point, the turntable rotates an angle θ=360/n1, and the length meter 9 is stretched out to sample once, and a circle is measured. , to find the starting position, the probe moves along the X-axis direction for a measurement step until the measurement process is completed, and n1×n2 coordinate points (x _ij , z _ij , θ _ij ), i=1...n1, j=1 are obtained ...n2.

Figure 11 shows the determination of the measurement reference coordinate value and the determination of the measurement stroke. In the figure, point A is the reference coordinate (x ₀ , z ₀ ). point, locate the coordinates of point A at the origin of the Z axis, and at point B, the X-axis coordinate is the X-axis grating reading x′, relative to the coordinate value of point A, the value is x′-x ₀ , and the Z-axis coordinate is the reading z of the protruding probe ′, relative to the coordinate value of point A is z′-z ₀ , so the coordinate value of point B is (x′-x ₀ , z′-z ₀ ), and the coordinate values of all measurement points can be obtained by analogy. Determining the measurement stroke is the absolute value subtracted from the vertex coordinate value and the most edge coordinate value. The measurement radius r=|x ₀ -x _side |, L=2r. After the measurement is confirmed, the number of measurement points can be determined by the measurement step distance.

The cylindrical coordinate contact measurement method of the large-diameter optical aspheric element of the present invention uses the ultra-precision measuring machine of the present invention for measurement, which includes the following steps:

1. Align the center of the turntable surface (11) with the center of the measuring machine length gauge (9) through alignment, set the precision level of the needle of the inductance micrometer to 0.01 μm, and set the probe of the inductance micrometer to high-precision contact The end of the length meter (9) is aligned, and the error is controlled at 0.1 μm, which is the alignment (meeting the measurement accuracy requirements), and the current X-axis coordinate value is recorded as the center value, and the coordinate of this point is used as the reference coordinate (x ₀ , z ₀ );

2. Put the workpiece on the turntable (11) of the measuring machine, place the workpiece at the center of the turntable (11) through the inductance micrometer, extend the length gauge (9) to find the highest measurement vertex of the workpiece, and then insert the The length gauge (9) moves to the workpiece edge position to determine the starting point position;

3. Determine the measurement stroke L value through the X-axis coordinate value;

4. Carry out two-dimensional surface shape measurement, set the measurement step distance after determining the L value, determine the number of steps according to the step distance, and perform measurement point scanning and data sampling at the same time;

5. Carry out three-dimensional surface shape measurement, determine the measurement angle and radial measurement step distance, determine the number of sampling points according to the angle and step distance, position and rotate the turntable and perform data sampling;

6. Establish the workpiece coordinate system and the measurement coordinate system, and convert the measurement coordinate system into workpiece coordinate coefficient values for data fitting processing.

7. Preprocess the measurement results to obtain the evaluation data suitable for the workpiece coordinates, and obtain the estimated value of the workpiece parameters through the linear least square method. After passing the estimated value, use the nonlinear least square method to obtain the fitting parameters of the workpiece, and perform contour assessment.

Claims (9)

1. A large-caliber optical aspheric element cylindrical coordinate contact measurement method is characterized in that, utilizing a measuring machine to collect two-dimensional or three-dimensional data by means of cylindrical coordinate measurement; comprises the following steps: Step S1: Use an inductance micrometer to align the center of the rotating table (11) and the center of the length gauge (9), so that the upper and lower centers are concentric, and the concentricity accuracy is guaranteed to be 0.1 μm; Step S2: Align the workpiece with an inductance micrometer, extend the length gauge (9), record the stretched amount of the length gauge (9), and record the X-axis coordinate value at the same time, and use the coordinate of this point as the reference coordinate (x ₀ , z ₀ ); Step S3: After determining the reference coordinates, move the X-axis to move the length meter (9) to the edge of the workpiece to determine the starting point, and compare the movement amount with the reference coordinates to determine the measurement stroke L; Step S4: Establish a workpiece coordinate system and a measurement coordinate system according to the measuring machine, determine two-dimensional measurement or three-dimensional measurement, and perform data collection to obtain required coordinate points. 2. A kind of cylindrical coordinate contact measuring method for large-diameter optical aspheric elements according to claim 1, characterized in that, in step S1, first find the center of the positive turn table (11) and the length gauge (9), and then pass the inductance The micrometer adjusts the workpiece to the center. 3. A kind of large-caliber optical aspheric element cylindrical coordinate contact measurement method according to claim 1, characterized in that, step S1 specifically comprises the following steps: fixing the inductance micrometer probe (100) to the table base ( 200), and fix the meter base (200) to any position on the turntable (11) where measurement can be realized, place the probe of the inductance micrometer (100) on the end of the length gauge (9), and pass the turntable ( 11) Adjust the centering mechanism of the rotating work; adjust the inductance micrometer to the 0.01 μm range, and adjust the error to within 0.1 μm, which is alignment. 4. A kind of cylindrical coordinate contact measurement method of large-diameter optical aspheric elements according to claim 1, characterized in that, in the two-dimensional measurement process, the X-axis component drives the length meter (9) to move along the X-axis direction to realize To measure the motion of the step distance, the length meter (9) stretches out to collect data every time a step distance is taken to obtain N coordinate points (xi _, z _i ), i=1...N; in the three-dimensional measurement process, the The number of measuring steps is n1, and the measuring step distance is n2. From the first point, the turntable surface (11) rotates an angle θ=360/n1, and the length meter (9) stretches out to sample once. start position, the turntable surface (11) moves one measurement step along the X-axis direction until the measurement process is completed, and n1×n2 coordinate points (x _ij , z _ij , θ _ij ), i=1...n1, j=1 are obtained ...n2. 5. A kind of large-diameter optical aspheric element cylindrical coordinate contact measuring method according to any one of claims 1 to 4, characterized in that the measuring machine comprises a natural granite bed (1), an X-axis component, a Z Shaft components and self-aligning and leveling devices; X-axis components include auxiliary gas static pressure guide rail (2), welded elliptical arc gantry (4), main gas static pressure guide rail (14) and first linear motor (19); auxiliary gas static pressure guide rail (2) and main The gas static pressure guide rail (14) is clamped on both sides of the natural granite bed (1); the two ends of the elliptical arc gantry (4) are welded, one end is fixed on the auxiliary gas static pressure guide rail (2), and the other end is fixed on the Main gas static pressure guide rail (14); The Z-axis components include octagonal granite guide columns (7), V-shaped air bearing blocks (8), length gauges (9) and second linear motors (20); two V-shaped air bearing blocks (8) pass through The bolts are connected to the welded elliptical arc gantry (4) to adjust the verticality of the Z axis; the octagonal granite guide column 7 and the symmetrically connected double V-shaped air bearing blocks (8) form a gas static pressure guide rail pair, Realize the up and down movement of the Z axis; the secondary coil of the second linear motor (20) is fixedly connected to the welded elliptical arc gantry (4), and the primary coil is connected to the granite guide post (7); the length gauge (9) is fixed on the granite guide post the inner cavity of the column (7); The self-aligning and leveling device includes a turntable surface (11), a universal leveling plate (12), a static pressure plate under the turntable (13) and a drive unit that drives the rotation of the static pressure plate (13) under the turntable; The disc (13) and the natural granite bed (1) are supported by an aerostatic bearing. 6. A cylindrical coordinate contact measurement method for large-caliber optical aspheric elements according to claim 5, characterized in that, the auxiliary gas static pressure guide rail (2) and the main gas static pressure guide rail (14) are provided with an inflatable interface , when the X-axis components move, inflate the auxiliary gas static guide rail (2) and the main gas static pressure guide rail (14) through the inflation interface, so that the auxiliary gas static pressure guide rail (2), the main gas static pressure guide rail (14) and the natural An air film is formed between the top surface and the side surface of the granite bed (1). 7. A cylindrical coordinate contact measurement method for large-diameter optical aspheric elements according to claim 5, wherein the centering and leveling device also includes several leveling devices and centering devices; The top of the static pressure plate (13) under the turntable is provided with a concave spherical surface (110) and several symmetrically arranged grooves; The lower part of the universal leveling plate (12) is provided with a convex spherical surface (101) and a conical slope (102); the universal leveling plate (12) is installed on the top of the static pressure plate (13) under the turntable, and the universal leveling plate (12 ) of the convex spherical surface (101) is matched with the concave spherical surface (110) of the static pressure plate (13) under the turntable; The leveling device comprises a leveling positioning plate (22), a leveling screw rod (25), a leveling pulley (26), a leveling pulley shaft (27) and a leveling support (28); the leveling support (28) is installed on In the corresponding groove on the static pressure plate (13) under the turntable, it can move along the groove of the static pressure plate (13) under the turntable; the leveling pulley shaft (27) connects the leveling pulley (26) to the leveling On the support (28); the leveling screw rod (25) is threadedly matched with the leveling support (28); The centering device comprises some self-aligning jackscrews (23) and the turntable (11); the lower mounting surface of the turntable (11) is directly installed on the universal leveling plate (12); the side of the turntable (11) is symmetrically provided with A plurality of threaded through holes, a plurality of self-aligning jackscrews (23) are arranged in the corresponding threaded through holes and are threadedly connected with the turntable surface (11). 8. A kind of large-caliber optical aspheric element cylindrical coordinate contact type measuring method according to claim 5, it is characterized in that, the center of natural granite bed (1) is provided with an installation hole, and hemispherical seat (34) is fixed on this In the installation hole; the hemispherical graphite tile (35) is fixed on the hemispherical seat (34); the turntable mandrel (15) is installed in the center of the hemispherical shaft (37) and is fixed on the lower static pressure plate ( 13) on; the convex spherical surface of the hemispherical axis (37) matches the concave spherical surface of the hemispherical graphite tile (35); The bottom surface of the static pressure plate (13) under the turntable is provided with an annular groove, and several flat supporting graphite blocks (32) are evenly fixed in the annular groove; the flat supporting graphite blocks (32) and the natural granite bed (1) form gas Hydrostatic bearing pair. 9. a kind of large-diameter optical aspheric element cylindrical coordinate contact type measuring method according to claim 5, is characterized in that, welding ellipse arc gantry (4) comprises front plate (42) and rear plate (46); The plate (42) and the back plate (46) are welded and fixed together by several symmetrically arranged stiffener plates; the lower edges of the front plate (42) and the back plate (46) include semi-elliptical arc segments.

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