阅读说明：本技术 一种高陡度大偏离量非球面元件主动平滑方法及工具 (Active smoothing method and tool for high-gradient large-deviation aspheric element ) 是由 张穗 王佳 邓永红 王朝阳 于 2021-09-13 设计创作，主要内容包括：本发明公开了一种高陡度大偏离量非球面元件主动平滑方法及工具,所述方法包括计算出元件与磨盘加工过程中的不吻合度曲线,通过不吻合度变化曲线分析元件和磨盘加工过程中的不吻合度变化分布趋势,并根据该变化趋势设计主动平滑方案,所述工具包括磨盘基底、连接件、连接轴、主轴、驱动轴、驱动电机,通过改变磨盘的面形曲率,使其实时适应被加工元件曲率半径,平滑高陡度大偏离量非球面元件表面中频误差。本发明针对高陡度大偏离量非球面元件的中频误差平滑加工提出工具设计及平滑方法,以降低在加工过程中磨盘与元件之间的不吻合度,提高加工后元件面形质量,平滑元件表面中频误差。(The invention discloses a method and a tool for actively smoothing a high-gradient large-deviation aspheric surface element, wherein the method comprises the steps of calculating a non-conformity curve in the processing process of the element and a grinding disc, analyzing the non-conformity change distribution trend in the processing process of the element and the grinding disc through the non-conformity change curve, and designing an active smoothing scheme according to the change trend, wherein the tool comprises a grinding disc substrate, a connecting piece, a connecting shaft, a main shaft, a driving shaft and a driving motor, and the tool is made to adapt to the curvature radius of the processed element in real time and smooth the intermediate frequency error on the surface of the high-gradient large-deviation aspheric surface element by changing the surface curvature of the grinding disc. The invention provides a tool design and a smoothing method for medium-frequency error smoothing of a high-gradient large-deviation aspheric element, so as to reduce the non-coincidence degree between a grinding disc and the element in the processing process, improve the surface shape quality of the processed element and smooth the medium-frequency error on the surface of the element.)

1. A high-gradient large-deviation aspheric element active smoothing method is characterized in that:

the active smoothing method comprises the following steps:

step S1, calculating the variation curve of the degree of non-conformity between the element and the grinding disc in the processing process, analyzing the distribution trend of the variation curve of the degree of non-conformity between the element and the grinding disc in the processing process through the variation curve of the degree of non-conformity, and constructing a formula which represents the variation curve of the degree of non-conformity between the element and the grinding disc in the processing process as follows:

whereinIs the curvature radius of the aspheric surface element at different positions, D is the caliber of the grinding disc, RL is the radius of the grinding disc,is the height difference between the edge point of the grinding disc and the circle center of the grinding disc,v=y(x)+RL+RL*sinθis a parametric equation expression of the grinding disc, whereinθ=-α，，Is a curve equation for the aspheric element,is the vertex curvature, R₀The vertex curvature radius is defined as k, which is a quadratic coefficient or a conic coefficient, x represents the position of the corresponding caliber in a coordinate system, and y represents the rise of the element at the corresponding caliber;

drawing a curve of the degree of non-conformity according to the formula to obtain the distribution condition of the degree of non-conformity between the element and the grinding disc in the processing process;

step S2, setting a fixed numerical value g along the rise direction with the top point of the element as the center of a circle, and establishing a plurality of circular ring zones with the distance of g on the surface of the element from the center of the circle at the top point of the element to the edge of the element around each center of the circle in the rise direction as a smooth processing path;

step S3, calculating the curvature radius R of the element at the current position at each ring zone;

step S4, deforming the grinding disc, and further transforming the surface shape of the grinding disc to have the corresponding curvature radius R in the step S3;

and step S5, the grinding disc after the machine tool is driven to deform is used for carrying out smooth machining on the current annular belt of the element surface, the machine tool drives the grinding disc to rotate around the circle center on the annular belt and simultaneously carry out translation from the top point of the element to the edge of the element, and therefore the medium-frequency error on the element surface is smoothly restrained.

2. A high-gradient large-deviation aspheric element active smoothing tool is characterized in that:

the active smoothing tool comprises a connecting piece (1), a grinding disc (2), a connecting shaft (3), a driving motor (4) and a driving shaft (5);

the grinding disc (2) is a deformable grinding disc capable of being stressed, a grinding disc main shaft (6) is arranged in the center of the upper surface of the grinding disc (2), holes are formed in the edge part of the upper surface of the grinding disc main shaft, and the connecting piece (1) is assembled on the grinding disc (2) through the holes; the connecting shaft (3) is a cylinder with a side wall punch and upper and lower bottom surface punches, is assembled with the connecting piece (1) through the side wall punch, is nested on the grinding disc main shaft (6) through the upper and lower bottom surface punches, and can move up and down along the grinding disc main shaft (6); drive shaft (5) are connected mill (2) and driving motor (4), and driving motor (4) inner wall winding has electrical coil (8), and permanent-magnet (7) set up inside electrical coil (8), and its both ends are fixed with motor shaft (9), both ends are connected with motor shaft (9) and connecting axle (3) respectively about drive shaft (5), and when electrical coil (8) circular telegram, permanent-magnet (7) drive motor shaft (9) motion, and motor shaft (9) motion drives drive shaft (5) displacement, and then will drive power transmission through connecting axle (3) reach connecting piece (1), from this connecting piece (1) exert force and make its shape of face to take place deformation mill (2).

3. A high steepness large offset aspheric element active smoothing tool as claimed in claim 2,

twelve connecting pieces (1) are arranged on the grinding disc (2) at equal intervals and are rigid connecting pieces made of metal.

4. A high steepness large offset aspheric element active smoothing tool as claimed in claim 2,

the driving shaft (5) has two parts, one part is connected with the connecting shaft (3) for transmitting driving force, and the other part is connected with the motor shaft (9).

5. A high steepness large offset aspheric element active smoothing tool as claimed in claim 2,

the deformation of the surface shape of the grinding disc (2) is realized by applying force to a connecting piece (1) on the grinding disc through a driving motor (4), wherein the surface shape of the grinding disc is changed by changing the size of the edge moment of the grinding disc (2) according to the calculated curvature parameter of the processing position of the element, so that the lower surface of the grinding disc is always matched with the surface of the element.

6. A high steepness large offset aspheric element active smoothing tool as claimed in claim 2,

the driving motor is a moving magnet type voice coil motor, and the permanent magnet is a movable permanent magnet.

Technical Field

The invention belongs to the field of advanced optical manufacturing, and particularly relates to an active smoothing method and tool for a high-gradient large-deviation aspheric element.

Background

Modern optical systems put extremely high requirements on the surface quality of optical elements, so that the manufacturing of high-precision aspheric optical element parts is a bottleneck technology recognized in the industry as a class of aspheric surface because of the difficulty and hot spots of current optical manufacturing. The rigid small grinding head adopted by the computer-controlled optical surface forming technology (CCOS) for processing the optical element at present can cause obvious medium-frequency error on the surface of the processed optical element due to the fact that the rigid small grinding head is not matched with the surface of a processed part when the optical element is processed, and the error can cause small-angle scattering of light rays and seriously affect the optical property of an optical system, so that the research on a method for inhibiting the medium-frequency and high-frequency errors generated in the processing process is an important problem in the field of optical processing.

At present, a passive smoothing technology is generally adopted for smoothing the intermediate frequency error, and a material with certain flexibility is selected as a supporting layer to design a passive smoothing grinding disc, so that the grinding disc can adapt to the surface of an element according to the change of the surface shape. The passive smoothing technology has a certain degree of goodness of fit for the aspheric surface element, but the passive deformation amount of the aspheric surface element is limited by the material of the grinding disc, the surface shape of the surface of the element is easily damaged when the rigidity of the material is too high, the processing efficiency is low when the flexibility is too high, and the rigidity and the flexibility of the material are difficult to balance. Meanwhile, when the aspheric surface element with high gradient and large deviation is used, the passive smoothing technology inhibits the low efficiency of the medium-high frequency error, and even destroys the low-frequency surface shape of the workpiece. The invention designs an active smoothing tool for smoothing a large-deviation aspheric element and a smoothing method thereof aiming at the problem of smoothing of medium-frequency errors on the surface of the high-gradient large-deviation aspheric element.

Disclosure of Invention

Aiming at the problems, the invention provides an active smoothing method and tool for a high-gradient large-deviation aspheric element, aiming at solving the problems that a small grinding head is not matched with the surface of an optical element during processing and the passive smoothing technology is difficult to process and process the intermediate frequency error of the large-deviation aspheric element.

In order to solve the problems in the prior art, the invention aims to describe the variation trend of the degree of dissonance in the machining process by calculating a function model of the degree of dissonance in the machining process of a construction element and a grinding disc, provide theoretical support for an active smoothing technology, make a smoothing scheme design aiming at the variation condition of the degree of dissonance, make a deformation control strategy of an active smoothing tool and design a corresponding active smoothing tool structure.

To achieve the above object, the first aspect of the present invention provides an active smoothing method for high-gradient and large-deviation aspheric elements,

the active smoothing method comprises the following steps:

step S1, calculating the variation curve of the degree of non-conformity between the element and the grinding disc in the processing process, analyzing the distribution trend of the variation curve of the degree of non-conformity between the element and the grinding disc in the processing process through the variation curve of the degree of non-conformity, and constructing a formula which represents the variation curve of the degree of non-conformity between the element and the grinding disc in the processing process as follows:

whereinIs the curvature radius of the aspheric surface element at different positions, D is the caliber of the grinding disc, RL is the radius of the grinding disc,is the height difference between the edge point of the grinding disc and the circle center of the grinding disc,v=y(x)+RL+RL*sinθis a parametric equation expression of the grinding disc, whereinθ=-α，，Is a curve equation for the aspheric element,is the vertex curvature, R₀The vertex curvature radius is defined as k, which is a quadratic coefficient or a conic coefficient, x represents the position of the corresponding caliber in a coordinate system, and y represents the rise of the element at the corresponding caliber;

calculating the inconsistency of the grinding disc and the element according to the equation system. The contact relation is expressed in the form of a piecewise function because the surface curvature of the aspheric element is different from place to place and the contact mode with the grinding disc is different from point to point.

Drawing a curve of the degree of non-conformity according to the formula to obtain the distribution condition of the degree of non-conformity between the element and the grinding disc in the processing process;

step S2, setting a fixed numerical value g along the rise direction with the top point of the element as the center of a circle, and establishing a plurality of circular ring zones with the distance of g on the surface of the element from the center of the circle at the top point of the element to the edge of the element around each center of the circle in the rise direction as a smooth processing path;

step S3, calculating the curvature radius R of the element at the current position at each ring zone;

step S4, deforming the grinding disc, and further transforming the surface shape of the grinding disc to have the corresponding curvature radius R in the step S3;

and step S5, the grinding disc after the machine tool is driven to deform is used for carrying out smooth machining on the current annular belt of the element surface, the machine tool drives the grinding disc to rotate around the circle center on the annular belt and simultaneously carry out translation from the top point of the element to the edge of the element, and therefore the medium-frequency error on the element surface is smoothly restrained.

In order to achieve the purpose, the invention provides an active smoothing tool for a high-gradient large-deviation aspheric element, which comprises a connecting piece 1, a grinding disc 2, a connecting shaft 3, a driving motor 4 and a driving shaft 5; the grinding disc 2 is a deformable grinding disc capable of being stressed, a grinding disc main shaft 6 is arranged at the center of the upper surface of the grinding disc 2, a perforation is arranged at the edge part of the upper surface of the grinding disc, and the connecting piece 1 is assembled on the grinding disc 2 through the perforation; the connecting shaft 3 is a cylinder with side wall punching holes and upper and lower bottom surface punching holes, is assembled with the connecting piece 1 through the side wall punching holes, is nested on the grinding disc main shaft 6 through the upper and lower bottom surface punching holes, and can move up and down along the grinding disc main shaft 6; drive shaft 5 is connected mill 2 with driving motor 4, and the winding of 4 inner walls of driving motor has electrical coil 8, and permanent-magnet 7 sets up inside electrical coil 8, and its both ends are fixed with motor shaft 9, both ends are connected with motor shaft 9 and connecting axle 3 respectively about 5 drive shaft, and when electrical coil 8 circular telegram, permanent-magnet 7 drives the motion of motor shaft 9, and the motion of motor shaft 9 drives drive shaft 5 displacement, and then will drive power transmission through connecting axle 3 arrives connecting piece 1, from this connecting piece 1 exerts force and makes its shape of face to mill 2 take place deformation. The curvature of the surface shape of the grinding disc is changed to adapt to the surface shape of the element to be processed in real time. The grinding disc is a circular disc.

The invention provides an active deformation structure design aiming at the processing of a large-deviation aspheric element so as to reduce the non-inosculation degree between the grinding disc and the element in the processing process and improve the surface shape quality of the processed element.

Furthermore, twelve connecting pieces 1 are arranged on the grinding disc 2 at equal intervals, and the connecting pieces are rigid connecting pieces made of metal materials.

Further, the driving shaft 5 has two parts, one part is connected with the connecting shaft 3 for transmitting a driving force, and the other part is connected with the motor shaft 9.

Further, the shape of the surface of the grinding disc 2 is deformed by applying force to the connecting piece 1 on the grinding disc through the driving motor 4, wherein the shape of the surface of the grinding disc is changed by changing the size of the moment of the edge of the grinding disc 2 according to the calculated curvature parameter at the processing position of the element, so that the lower surface of the grinding disc is always matched with the surface of the element.

The driving motor is a moving magnet type voice coil motor, an energizable coil is wound on the inner wall of the driving motor, and a movable permanent magnet fixed on a motor shaft is arranged inside the driving motor.

The invention has the advantages that:

1) a non-conformity degree change model of the element and the grinding disc in the machining process is constructed, and the change trend of the non-conformity degree on the surface of the element in the machining process is reflected.

2) It is designed to create zones at equal intervals from the apex to the edge of the element, and to actively change the disc profile according to the curvature of the element at the zone location to accommodate the smoothing of the element surface.

3) Through twelve connecting pieces, the surface shape change of the grinding disc can be accurately controlled in a mode of changing the magnitude of the edge moment, so that the surface shape is converted to the corresponding curvature.

4) Adopt voice coil motor as the drive, can be accurate carry out small accurate transform control to the mill.

5) By means of the active smoothing scheme, aspheric elements with high steepness and large deviation can be machined.

6) The active smoothing is carried out by adopting a computer numerical control mode, and compared with a passive smoothing technology, the active smoothing method has a more definite smoothing effect and a more surface shape matching effect.

Drawings

FIG. 1 is a graph illustrating the trend of non-compliance of a high steepness and large offset aspheric element with a grinding disc during processing in an example of the present invention; in the figure, the origin is the vertex of the element, the ordinate is the non-inosculation value, and the abscissa is the radius direction of the element;

FIG. 2 is a graph of the non-compliance trend of a high steepness and large offset aspheric element over the entire plane during the disc machining process in an example of the present invention;

FIG. 3 is a graph of the contact of a high steepness and large offset aspheric element with a grinding disc during machining with a spherical model abstracted from the grinding disc as the curvature of the surface changes;

FIG. 4 is a comparison of the curvature profile of a high steepness large offset aspheric component of an example of the present invention plotted in the same graph as the trend graph of the mismatch of FIG. 1;

FIGS. 5-1 and 5-2 are an isometric and elevational view, respectively, of the general structure of the present invention;

FIG. 6 is an isometric view of a grinding disc configuration of the present invention;

FIG. 7 is a front view of the abrasive disc construction of the present invention;

FIG. 8 is a top schematic view of the abrasive disc construction of the present invention;

fig. 9-1, 9-2 and 9-3 are respectively an isometric view, a front view and a sectional internal structure view of a driving motor structure of the present invention.

Reference numerals:

1. a connecting member; 2. a grinding disc; 3. a connecting shaft; 4. a drive motor; 5. a drive shaft; 6. a main shaft; 7. a permanent magnet; 8. an electrified coil; 9. a motor shaft.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings in conjunction with specific embodiments.

Parameters of the aspheric element with high gradient and large deviation to be processed in the example are the caliber phi =240mm, the vertex curvature R0=629.33mm and the quadric surface constant K = -33.1; the grinding disc is provided with a caliber D =30mm and a radius RL =800 mm.

Fig. 1 is a graph showing a trend of a variation of a mismatch between a high-steepness large-deviation aspheric element and a grinding disc in a processing process of the high-steepness large-deviation aspheric element according to an embodiment of the present invention, where the model reflects that when a curvature of the grinding disc is fixed, when the high-steepness large-deviation aspheric element is processed, since a surface curvature of the aspheric element varies at a moment and a contact condition between the grinding disc and the element is different at different curvature radii, a function of the mismatch is a piecewise function, and it can be seen from the curve that the mismatch is a critical point when the mismatch is first reduced until the high-steepness large-deviation aspheric element R and the grinding disc RL are equal, and a minimum mismatch value approaches to 0.

Fig. 2 is a graph showing the distribution of the non-conformity between the high-gradient large-deviation aspheric element and the grinding disc in the whole surface of the element in the example of the invention, and the graph shows a distribution trend model of the non-conformity between the high-gradient large-deviation aspheric element and the grinding disc in the processing process from the plane dimension.

As shown in fig. 3, the grinding disc is abstracted into a spherical model, and when the grinding disc processes the aspheric surface element with high gradient and large deviation, the contact conditions at different curvature positions are different, and the calculation method of the non-conformity degree is also different; when RL is more than R, the grinding disc is in edge contact with the element, and the non-fit area is from the bottom of the grinding disc to the surface of the element; when RL = R, the curve is a non-inosculation critical point, the non-inosculation degree is 0 theoretically at the moment, and the grinding disc is completely matched with the surface shape; when RL < R, the bottom of the grinding disc is in contact with the surface of the element, and the non-fit area is from the edge of the grinding disc to the surface of the element.

As shown in fig. 4, when the curvature-radius correspondence graph of the aspheric element with high steepness and large deviation in the present example is plotted with the trend curve of the non-compliance of the manufacturing process, it can be seen that the critical point of the non-compliance value close to 0 is close to the point of the aspheric element R = RL.

According to the analysis, the degree of non-conformity between the large-deviation aspheric element and the grinding disc in the processing process is a sectional function, and the critical point of the degree of non-conformity is that when the curvature of the grinding disc is consistent with that of the element, the degree of surface shape matching between the grinding disc and the element is the highest, and the degree of non-conformity is the lowest, so that the high-gradient large-deviation aspheric element active smoothing tool and the method are designed according to the analysis. The method mainly comprises the following steps:

step S1, calculating a curve of the degree of non-conformity in the processing process of the element and the grinding disc, analyzing the distribution trend of the degree of non-conformity in the processing process of the element and the grinding disc through the curve of the degree of non-conformity, and constructing a curve formula of the degree of non-conformity under the condition of the degree of non-conformity between the grinding disc and the element in the processing process:

whereinThe curvature of the aspheric surface element at different positions, D is the caliber of the grinding disc, RL is the radius of the grinding disc,is the height difference between the edge point of the grinding disc and the circle center of the grinding disc,v=y(x)+RL+RL*sinθis a parametric equation expression of the grinding disc, whereinθ=-α，，Is a curve equation for an aspheric element. Calculating the inconsistency of the grinding disc and the element according to the equation system. The contact relation is expressed in the form of a piecewise function because the surface curvature of the aspheric element is different from place to place and the contact mode with the grinding disc is different from point to point. Drawing an inequality curve according to the inequality function to obtain the distribution condition of the inequality between the element and the grinding disc in the processing process;

step S2, setting a fixed numerical value g along the rise direction with the top point of the element as the center of a circle, and establishing a plurality of circular ring zones with the distance of g on the surface of the element from the center of the circle at the top point of the element to the edge of the element around each center of the circle in the height direction to be used as a smooth processing path;

step S3, calculating the curvature radius R of the current position element at each zone;

step S4, the grinding disc surface shape of the active smoothing tool is transformed to a corresponding curvature R;

step S5, the grinding disc after the machine tool drive deformation is used for smooth processing on the current ring belt of the element surface, the machine tool drive grinding disc rotates around the circle center on the ring belt, the grinding disc moves horizontally from the top to the edge when the circle center revolves on the ring belt, and the medium frequency error on the element surface is smoothly inhibited;

as shown in fig. 5-1 to 9-3, the invention provides an active smoothing tool for high-gradient large-deviation aspheric elements, which comprises a connecting piece 1, a grinding disc 2, a connecting shaft 3, a driving motor 4, a driving shaft 5, a main shaft 6, a permanent magnet 7, an energizing coil 8 and a motor shaft 9; the grinding disc substrate 2 can be deformed under stress and assembled with twelve connecting pieces 1; the connecting piece 1 is installed with a connecting shaft 3, and the connecting shaft 3 moves up and down on a grinding disc main shaft 6 under the drive of a drive motor 4; the connecting shaft 3 is assembled with a driving shaft 5; the driving shaft 5 is connected with the driving motor 4 to obtain driving force. Under the drive of a drive motor, the drive force is transmitted to the grinding disc 2 through the connecting piece 1, the change of the surface shape of the grinding disc is realized, and the surface shape curvature of the grinding disc is changed to adapt to the surface shape of the element to be processed in real time.

The grinding disc 2 can be stressed to change the surface shape. Twelve connecting pieces 1 are arranged on the grinding disc 2 at equal intervals, and the connecting pieces 1 are rigid connecting pieces made of metal. The connecting shaft 3 is nested on the grinding disc main shaft 6 and can move up and down. The driving shaft 5 has two parts, one part connected to the connecting shaft 3 for transmitting a driving force and the other part connected to the motor shaft 9. The driving motor 4 is a moving magnet type voice coil motor, an energizable coil 8 is wound on the inner wall of the driving motor, and a movable permanent magnet 7 fixed on a motor shaft is arranged inside the driving motor.

In the embodiment of the invention, the deformation control strategy of the surface shape of the grinding disc of the high-gradient large-deviation aspheric element active smoothing tool is to apply force to a connecting piece on the grinding disc through a driving motor, send an instruction according to the calculated parameters at the processing position and change the surface shape of the grinding disc in a mode of changing the size of the edge moment, so that the surface of the grinding disc is always matched with the surface of the high-gradient large-deviation aspheric element.

The invention provides an active smoothing tool and method for a high-gradient large-deviation aspheric element, so that the non-coincidence degree between a grinding disc and the element in the machining process is reduced, and the surface shape quality of the machined element is improved.

It should be understood, however, that there is no intent to limit the invention to the particular forms or embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.