A hierarchical material removal manufacturing method for high-aspect-ratio thin-walled optical elements

Abstract

The application discloses a kind of high ratio of height to thickness thin-walled optical element's hierarchical material removal manufacturing method, belongs to the field of precision optical element manufacturing.For the problem that high ratio of height to thickness thin-walled optical element wall is thin and fragile and difficult to process, a new type of thin-walled bevel hierarchical material removal model is constructed, the material removal efficiency and depth of the grinding removal process of the machined element can be quantitatively calculated, and the material processing process parameter planning is accurately guided;Through kinematic modeling of the grinding disc, tooling fixture and workpiece, the motion trajectory of the workpiece relative to the grinding disc is calculated;Combined with the material contact removal characteristics and process parameter removal process theoretical calculation, the material removal rate is obtained.The application is suitable for calculating the material removal rate under different processing parameters when the bevel part is ground on the grinding machine after machining, and is also suitable for calculating the processing parameters according to the material removal rate, to complete the accurate control of the manufacturing process of high ratio of height to thickness thin-walled optical element.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of precision optical element manufacturing, and particularly relates to a hierarchical material removal manufacturing method for high-diameter-thickness-ratio thin-wall optical elements. BACKGROUND

[0002] Plane grinding and polishing is an important way to obtain high-precision optical elements, and has a wide application in the fields of electronic information, laser and aerospace. The plane grinding and polishing of materials is a complex and precise multi-input and multi-output system, and the material removal rate and surface precision of the output are restricted by multiple input factors, and numerous factors jointly affect the processing process and result. Especially for high-diameter-thickness-ratio thin-wall optical elements, they have difficult-to-machine characteristics such as easy damage and uncontrollability. At present, few people have proposed accurate digital modeling methods for them and used them for processing parameter planning. SUMMARY

[0003] In order to solve the machining problem of thin-wall optical elements in the existing industry, the present application provides a hierarchical material removal manufacturing method for high-diameter-thickness-ratio thin-wall optical elements. The method regards the cross section of the machined element as an inclined plane, establishes a hierarchical machining removal model and a relative motion trajectory kinematics model, deduces a material removal rate model, guides the machining process planning and accurate manufacturing of the element, and solves the problem of calculating the grinding removal rate of high-diameter-thickness-ratio thin-wall optical elements.

[0004] To achieve the above object, the present application adopts the following technical scheme:

[0005] A hierarchical material removal manufacturing method for high-diameter-thickness-ratio thin-wall optical elements, comprising the following steps:

[0006] 1) An inclined plane hierarchical model is proposed for the grinding process of the workpiece;

[0007] 2) The kinematics modeling of the inclined plane workpiece relative to the grinding disc on the grinding machine is completed;

[0008] 3) A relationship between the grinding process parameters of the new type of optical element and the material removal efficiency is constructed;

[0009] 4) Forward process planning and reverse process planning of specific material specific removal process are guided.

[0010] The further improvement of the present application is that step 1) establishes a grinding removal model for high-diameter-thickness-ratio thin-wall optical elements, establishes a kinematics model of the workpiece-grinding machine relative motion trajectory for the planetary grinding machine, and combines the material contact removal characteristics and process parameter removal process theory to calculate the material removal rate under the corresponding machining parameters.

[0011] The further improvement of the present application is that the specific implementation method of step 1) is to regard the ground surface of the thin-wall optical element with high aspect ratio as an inclined plane, and according to the clamping mode during the element grinding, the element surface actually participating in the grinding is derived as a hierarchical plane varying with time.

[0012] The further improvement of the present application is that step 2) completes the kinematic modeling of the motion trajectory of the inclined plane workpiece on the grinding machine relative to the grinding disc, and the relative motion speed of the workpiece and the grinding machine is obtained through coordinate transformation, and the calculation modeling of the inclined plane hierarchical grinding relative motion trajectory is completed.

[0013] The further improvement of the present application is that the coordinate transformation is to transform the workpiece coordinate system to the grinding machine coordinate system, and considering the inclined plane hierarchical model of the workpiece in the grinding process, the points on the workpiece coordinate system correspondingly have different value ranges with different grinding times.

[0014] The further improvement of the present application is that the specific implementation method of step 2) is to establish a coordinate system A for the grinding disc, and a coordinate system B for the workpiece, to transform the workpiece coordinate system B to the grinding disc coordinate system A through coordinate transformation, the obtained coordinates are the motion trajectory of any point on the workpiece relative to the grinding disc with time, and the value range thereof is listed in combination with the hierarchical material removal model, and the relative motion speed of the two is obtained by derivation of time t.

[0015] The further improvement of the present application is that step 3) considers the material contact removal characteristics and the process parameter removal process theory for the high aspect ratio thin-wall optical element, and models and constructs the relationship formula of the process parameter input and the material removal efficiency of the optical element grinding process.

[0016] The further improvement of the present application is that the specific implementation method of step 3) is:

[0017] (301) The material grinding removal process is modeled in two aspects of macroscopic contact surface and microscopic grinding removal; macroscopically, the actual contact area on the macroscopic surface is obtained through the grinding inclined plane model of the workpiece, and is used to solve the material removal thickness; microscopically, based on the inter-particle force, it is considered that the material removal rate is related to the micro-particles, and the contact between the grinding disc and the element is considered as elastic-plastic contact, and the actual contact area of the micro-particles is obtained by using the contact characteristics of the workpiece and grinding disc materials, and is used to solve the actual number of abrasive particles;

[0018] (302) The relative motion speed v of the workpiece and the grinding disc, the grinding liquid particle diameter and concentration, the grinding disc rotating speed and the above-mentioned macroscopic and microscopic contact areas are taken as input parameters, and the volume relationship of the material removal is used to solve the output parameter-material removal rate.

[0019] The further improvement of the present application is that step 4) proposes to complete the forward process planning and reverse process planning of the specific material specific removal process based on the established removal model, that is, to accurately calculate the material removal efficiency and depth with process parameter input, or to complete the reverse calculation of the process parameter with the determined material removal efficiency and depth.

[0020] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0021] The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which models the grinding surface of the high aspect ratio optical thin-walled element after cutting processing, proposes a grinding "bevel body" model, and models the hierarchical material removal distribution of the bevel body.

[0022] The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which solves the grinding process parameter control problem of the high aspect ratio optical thin-walled element after cutting processing, and can complete the accurate manufacturing of the high aspect ratio optical thin-walled element through process parameter input based on the bevel body hierarchical material removal model and the relative motion trajectory model. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which models the grinding surface of the high aspect ratio optical thin-walled element after cutting processing, proposes a grinding "bevel body" model, and models the hierarchical material removal distribution of the bevel body.

[0024] Figure 2 The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which models the grinding surface of the high aspect ratio optical thin-walled element after cutting processing, proposes a grinding "bevel body" model, and models the hierarchical material removal distribution of the bevel body.

[0025] Figure 3 The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which models the grinding surface of the high aspect ratio optical thin-walled element after cutting processing, proposes a grinding "bevel body" model, and models the hierarchical material removal distribution of the bevel body.

[0026] Figure 4 The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which models the grinding surface of the high aspect ratio optical thin-walled element after cutting processing, proposes a grinding "bevel body" model, and models the hierarchical material removal distribution of the bevel body.

[0027] Figure 5 The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which models the grinding surface of the high aspect ratio optical thin-walled element after cutting processing, proposes a grinding "bevel body" model, and models the hierarchical material removal distribution of the bevel body.

[0028] Figure 6 The present application provides a hierarchical material removal manufacturing method for high aspect ratio thin-walled optical elements, which models the grinding surface of the high aspect ratio optical thin-walled element after cutting processing, proposes a grinding "bevel body" model, and models the hierarchical material removal distribution of the bevel body.

[0029] DETAILED DESCRIPTION

[0030] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] This invention provides a method for manufacturing layered material removal for thin-walled optical elements with high aspect ratios, including the following input parameters: polishing slurry volume concentration. Abrasive grain diameter D, grinding disc rotation speed, and the tilt angle and diameter of the cutting surface of optical elements, etc.

[0032] A method for manufacturing a high aspect ratio thin-walled optical element by removing layers of material, comprising the following steps:

[0033] (1) Establish a grinding model of thin-walled optical elements obtained after cutting process. It is assumed that the grinding part is a sloping body and the processing surface is a sloping surface. The law of the change of the contact area between the element and the grinding disc with time is studied. At the same time, the change of the contact area will also affect the material removal rate.

[0034] (2) Establish coordinate system A for the grinding disc and coordinate system B for the workpiece. The coordinates of points in the two coordinate systems are functions of time. Transform the coordinates of point P(x2, y2) on the workpiece coordinate system B to the grinding disc coordinate system A. The resulting coordinates P'(x1, y1) are the trajectory of any point on the workpiece relative to the grinding disc over time. The relative velocity v between the two can be obtained by differentiating the parameter time t in the coordinate system.

[0035] (3) The material grinding and removal process is modeled from two aspects: macroscopic contact surface and microscopic particle grinding. A macroscopic grinding "inclined surface" model of the workpiece is proposed. This model assumes that the cutting surfaces of the optical elements obtained by cutting all exhibit a certain inclination angle. As the grinding process progresses, the inclination height gradually decreases, while the contact area between the workpiece and the grinding disc gradually increases. (See reference for details.) Figure 1 The calculations are based on interparticle forces at the microscopic level, assuming that the grinding particles are embedded in the workpiece surface and that the grinding process takes place during grinding. The contact between the grinding disc and the component is considered to be elastoplastic, with the actual microscopic roughness of the contact surface defined as 'a'. Additionally, a density correction factor is added for the workpiece and grinding disc to account for the influence of the oxide film. .

[0036] (4) Calculate the material removal efficiency. The input parameters include the contact area of ​​the grinding disc on the part. , micro material actual contact area a, relative motion speed v, polishing liquid parameters, polishing disc motion parameters, etc., and finally according to the volume removal principle of the polishing particles, the material removal rate formula of the optical element on the polishing machine is calculated. Finally, the material removal rate solving formula of the specific optical element is proposed:

[0037]

[0038] wherein D is the diameter of the polishing liquid abrasive particle, is the coefficient factor of the oxide film, is the volume concentration of the polishing liquid, is the embedding depth of the abrasive particle into the element, and a is the micro actual contact area when the number of abrasive particles is calculated, is the theoretical contact area when the material removal thickness is calculated.

[0039] Further, step (1) is to remove the model of the thin-walled optical element polishing surface obtained after the cutting process, and the overall modeling is as shown in the accompanying Figure 2 The model believes that the element after cutting processing is mostly in the form of an inclined body, and the element is clamped with the axis as the reference in the polishing process. The polishing process is from top to bottom, so the polishing contact surface gradually increases with time;

[0040] Further, step (1) is to the contact area change model of the element inclined surface in the polishing process, as shown in the accompanying Figure 3 For any time t in the polishing process, the contact area of the element and the grinding disc can be regarded as a part of a whole circle. Assuming that the processed thickness h and the element surface inclination angle α are known, the cross-sectional area A can be obtained by geometric relationship: and the relationship between the processed thickness h and the cross-sectional area A is:

[0041] Further, step (2) is to model the polishing machine, as shown in the accompanying Figure 4 The modeling object is the spatial geometric motion position of the workpiece and the grinding disc. The grinding disc is used to establish the coordinate system A, and the workpiece is used to establish the coordinate system B. The intermediate parameter, i.e., the relative motion speed v of the workpiece and the grinding disc, is calculated. Considering the inclined body level model of the workpiece in the polishing process, the points on the workpiece coordinate system have different value ranges corresponding to different polishing times.

[0042] The coordinate system B is established for the workpiece, and the coordinates of the points on the coordinate system are

[0043]

[0044] wherein,

[0045]

[0046] Where a coordinate system A is established for the grinding disc, and the transformation of (x1, y1) in the coordinate system A to the coordinate system B is

[0047]

[0048]

[0049] Where s, b are the horizontal and vertical distances of the workpiece center relative to the grinding disc center, as shown in the attached Figure 4 Therefore, the relative motion velocity is

[0050]

[0051] Further, step (2) is for the material grinding removal model, the surface obtained by the previous step of cutting processing of the workpiece is regarded as an inclined surface as the grinding initial surface, which is used to study the contact with the grinding disc, and the inclined angle of the inclined surface produced under different processing conditions is different. The grinding model is used to calculate the accurate equation coefficients. Macroscopically, the surface obtained by the previous step of cutting processing of the workpiece is regarded as an inclined surface as the grinding initial surface, and the actual contact area of the workpiece and the grinding disc can be obtained by modeling calculation , which changes with time and is also a function of the processed thickness h;

[0052] Further, step (3) of the calculation of the micro actual contact area a adopts a rough surface contact theory model, which combines the mechanical characteristics of the material and considers that the contact between the grinding disc and the element is elastic-plastic, thereby relating the actual contact area of the two to the surface characteristics; the material removal rate of a single abrasive grain adopts a material embedding model, which considers that the direct contact between the abrasive grain and the element is plastic, thereby obtaining the embedding area of the abrasive grain as ; the calculation of the relative motion velocity v adopts a coordinate transformation analysis, as described above; and the equation coefficient affected by the density is quantitatively calculated for a specific material.

[0053] The material removal rate expression is obtained by integrating the above formula:

[0054]

[0055] where D is the abrasive grain diameter of the grinding fluid, is the coefficient factor of the oxide film, is the volume concentration of the grinding fluid, is the embedding depth of the abrasive grain into the element, a is the micro actual contact area when calculating the number of abrasive grains on the contact surface, is the theoretical contact area when calculating the material removal thickness.

[0056] Embodiment

[0057] The embodiment of a high aspect ratio thin-walled optical element of hierarchical material removal manufacturing method, the use of equipment and materials as follows:

[0058] Corundum powder w20 grinding fluid concentration 10%, k9 glass optical element (diameter d = 50 mm, thickness H = 5 mm, cutting surface angle = 4.6 °), UNIPOL-1203 chemical mechanical polishing machine, three coordinate measuring instrument.

[0059] Where the processing parameters are as follows: grinding disc speed 100 r / min, workpiece speed for 0, pressure 14 N, workpiece coordinate system relative to the grinding disc coordinate system position (s, b) is approximately (75, 75).

[0060] The above-mentioned high aspect ratio thin-walled optical element of hierarchical material removal manufacturing method, comprising the following steps:

[0061] (1) to establish a coordinate system B for the workpiece, the coordinates of the point on the coordinate system is

[0062]

[0063]

[0064] The grinding disc of UNIPOL-1203 chemical mechanical polishing machine to establish a coordinate system A, the (x1, y1) in the coordinate system A is transformed into the coordinate system B, namely

[0065]

[0066]

[0067] Relative motion velocity .

[0068] (2) the workpiece grinding surface is regarded as an inclined surface, then the actual processing cross-sectional area is

[0069]

[0070] The analysis of the micro-abrasive grinding, taking the appropriate oxide film coefficient , the former formula into the material removal rate:

[0071]

[0072] (3) the experimental data and calculate the theoretical material removal amount data.

[0073] The two data plot as Figure 6It can be seen from the chart that the calculation of the polishing removal amount of the present application for specific high aspect ratio material has certain accuracy, the error range is ±0.005mm, and has certain reference effect and certain practical benefit for parameter selection in actual polishing processing.

[0074] The above is only an embodiment of the present application, and does not limit the protection scope of the present application, and any equivalent structure or equivalent process transformation made by using the content of the present application specification and drawings, or direct or indirect application in other related system fields, are also included in the protection scope of the present application.

Claims

1. A method for manufacturing a high aspect ratio thin-walled optical element by removing layers of material, characterized in that, Includes the following steps: 1) A slope-body hierarchical model is proposed for the grinding process of the workpiece; A grinding removal model for thin-walled optical elements with high aspect ratios is established. A kinematic model of the relative motion trajectory between the workpiece and the grinding machine is established for a planetary grinding machine. The material removal rate under the corresponding processing parameters is calculated by combining the material contact removal characteristics and the theoretical process of the removal process with process parameters. The specific implementation method is to regard the grinding surface of the thin-walled optical element with high aspect ratio as an inclined plane. Based on the clamping method of the element during grinding, it is derived that the actual element surface participating in the grinding is a hierarchical plane that changes with time. 2) Complete the kinematic modeling of the motion trajectory of the inclined workpiece relative to the grinding disc on the grinding machine; 3) Construct a new relationship between process parameters and material removal efficiency in the grinding and processing of optical components; for thin-walled optical components with high aspect ratios, considering the material contact removal characteristics and process parameter removal theory, a model is constructed to establish the relationship between the input process parameters and material removal efficiency in the grinding and processing of optical components; the specific implementation method is as follows: (301) The material grinding process is modeled in terms of both macroscopic contact surface and microscopic grinding removal. On the macroscopic level, the actual contact area is obtained through the grinding inclined plane layer model of the workpiece, which is used to solve the material removal thickness. On the microscopic level, based on the interparticle force, it is assumed that the material removal rate is related to the microparticles. At the same time, it is assumed that the contact between the grinding disc and the component is an elastoplastic contact. The actual contact area of ​​the material on the microscopic level is obtained by using the contact characteristics of the workpiece grinding disc material, which is used to solve the number of abrasive grains in actual action. (302) By utilizing the volume relationship of material removal, and combining various parameters, the output parameter—material removal rate—is obtained. The calculation formula is: In the formula, D is the diameter of the grinding fluid abrasive particles. It is the coefficient factor of the oxide film. It is the volume concentration of the grinding fluid. 'a' represents the depth of abrasive grain embedding in the component, and 'a' represents the actual microscopic contact area when calculating the number of abrasive grains on the contact surface. It is the theoretical contact area when the material thickness is removed. It is the workpiece radius. The thickness is the processed thickness, and α is the workpiece surface tilt angle. and t is a point on the grinding disc relative to the workpiece coordinate system, and t is time. 4) Guide forward and reverse process planning for specific removal processes of specific materials.

2. The method for manufacturing a high aspect ratio thin-walled optical element by removing layers of material according to claim 1, characterized in that, Step 2) Complete the kinematic modeling of the motion trajectory of the inclined workpiece relative to the grinding disc on the grinding machine, obtain the relative motion speed between the workpiece and the grinding machine through coordinate transformation, and complete the calculation modeling of the relative motion trajectory of the inclined layer grinding.

3. The method for manufacturing a high aspect ratio thin-walled optical element by removing layers of material according to claim 2, characterized in that, Coordinate transformation is the process of transforming the workpiece coordinate system to the grinding machine coordinate system. Considering the inclined plane hierarchical model of the workpiece during the grinding process, the points on the workpiece coordinate system have different value ranges depending on the grinding time.

4. The method for manufacturing a high aspect ratio thin-walled optical element by removing layers of material according to claim 2, characterized in that, The specific implementation method of step 2) is as follows: establish coordinate system A for the grinding disk and coordinate system B for the workpiece. Transform the workpiece coordinate system B to the grinding disk coordinate system A through coordinate transformation. The resulting coordinates are the motion trajectory of any point on the workpiece relative to the grinding disk over time. Combine the layered material removal model to list its value range and obtain the relative motion speed of the two by taking the derivative with respect to time t.

5. The method for manufacturing a high aspect ratio thin-walled optical element by removing layers of material according to claim 1, characterized in that, Step 4) Propose forward and reverse process planning for a specific material and a specific removal process based on the established removal model. That is, to accurately calculate the material removal efficiency and depth with the input of process parameters, or to reverse the process parameters with a determined material removal efficiency and depth.

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