A method for constructing a large-curvature optical surface super-finishing tool path auxiliary curved surface

Abstract

The application relates to a large-curvature optical surface superfinishing tool path auxiliary curved surface construction method, which comprises the following steps: step S1, preliminary expansion: using the "expansion" instruction of UG software, uniformly expanding an original optical surface along the periphery to form an auxiliary surface consistent with the curvature of the original optical surface; step S2, lateral stretching: using the "stretching" instruction of UG software, stretching the expanded auxiliary surface on both sides; and step S3, surface rounding: using the "surface rounding" instruction of UG software, rounding all the connecting parts of the expanded surface and the lateral stretching surface of the auxiliary surface to form an integrated and curvature-continuous auxiliary curved surface. The application can realize "interference active avoidance", and completely solves the tool path disorder and collision problem in the machining of a large-curvature z free curved surface.

Description

Technical Field

[0001] This invention relates to the field of precision and ultra-precision machining technology, and in particular to a method for constructing toolpath-assisted curved surfaces for ultra-precision machining of large curvature optical surfaces. Background Technology

[0002] In single-point diamond ultra-precision machining, a spiral trajectory turning is used. When the optical surface to be machined is square or irregular (a large curvature freeform surface refers to an optical surface with a very significant degree of curvature; the greater the curvature, the smaller the radius of curvature), the scope of this invention refers to the excessive extension of the empty tool path due to the large curvature, where the deepest part of the tool path along the Z-axis is three times or more greater than the sagitta of the optical surface of the mold core itself, and the tool path is disordered. Figure 1 , Figure 2 As shown, Figure 2 The yellow area indicated by the arrow represents the toolpath for machining from the outside to the inside during the empty tool transition. The blue area indicated by the arrow represents the actual toolpath for machining the optical surface. The gray area indicated by the arrow represents the optical surface (machining is done in a spiral pattern from the outside to the inside). In this case, the software generates a toolpath that adapts to the curvature of the optical surface. When the curvature of the optical surface is large, the toolpath generated by the software will geometrically interfere with the tooling, fixture, or machine tool structure, resulting in a disordered empty toolpath. Furthermore, because the Z-axis acceleration of the generated empty toolpath is too fast, the following error is too large, which may prevent the empty toolpath area from being machined properly. Adjusting it through the software has little effect. Figure 3 As shown.

[0003] In existing technologies, the two main areas of research and optimization are: constructing auxiliary surfaces for optical surface processing and avoiding toolpath interference in ultra-precision machining. One type of technology focuses on constructing auxiliary surfaces through a single step, such as automatic software extension, surface offsetting, and point cloud fitting. Its core is only to improve the surface accuracy of the optical surface, without considering the tooling interference problem. One type of technology avoids interference by passively detecting toolpaths, reducing interfering toolpaths, and adjusting tool posture / coordinates. Although it can solve the collision problem to some extent, toolpath reduction and parameter adjustment can easily lead to unstable tool entry and exit. Summary of the Invention

[0004] The purpose of this invention is to provide a method for constructing toolpath-assisted curved surfaces for ultra-precision machining of large curvature optical surfaces, which can achieve "active interference avoidance" and completely solve the problems of toolpath disorder and collision in the machining of large curvature z-free curved surfaces.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing a toolpath-assisted curved surface for ultra-precision machining of large curvature optical surfaces, comprising the following steps: Step S1: Perform initial enlargement: Use the "enlarge" command in UG software to uniformly enlarge the original optical surface along the perimeter to form an auxiliary surface with the same curvature as the original optical surface; Step S2: Perform lateral stretching: Use the "Stretch" command in UG software to stretch the enlarged auxiliary surface laterally on both sides. Step S3: Round the surface: Use the "Surface Rounding" command in UG software to round all the connections of the enlarged surface and the lateral stretching surface of the auxiliary surface to form an integrated auxiliary surface with continuous curvature.

[0006] Furthermore, the original optical surface is uniformly expanded around its perimeter by entering a value in the pop-up window or manually adjusting the sphere in the red box to match the curvature of the original optical surface.

[0007] Furthermore, the stretching direction of the dual-lateral stretching is a horizontal direction perpendicular to the normal of the original optical surface, abandoning the extension towards the normal of the original optical surface, and the distance must exceed the maximum processing outer edge of the optical surface.

[0008] The beneficial effects of this invention are: 1. Abandoning the traditional passive mode of directly generating toolpath trajectories based on the curvature of optical surfaces, this method adopts an auxiliary surface construction approach, shifting from passive to active. The auxiliary surface is constructed through three steps: "surface enlargement + lateral stretching + smooth connection." This achieves the dual goals of "range expansion" (avoiding abrupt changes on the original optical surface that could affect the optical path) and "interference avoidance," thus realizing "active interference avoidance" and completely resolving toolpath disorder and collision problems in the machining of large-curvature z-shaped freeform surfaces. 2. At the same time, by rounding and smoothing the transition of the surface, the curvature of the free-form surface of the auxiliary surface is eliminated, the processing stability is improved, and the vibration problem caused by the existing interference avoidance technology is solved. Attached Figure Description

[0009] Figure 1 This is a schematic diagram showing that the toolpath at the deepest point of the Z-axis is more than 3 times the sagitta of the optical surface of the mold core itself. Figure 2 A schematic diagram of the toolpath for machining the spiral line of an ultra-precision optical surface from the outside in. Figure 3 This is a schematic diagram of a disordered toolpath; Figure 4 A schematic diagram for initial expansion; Figure 5 This is a schematic diagram of lateral stretching. Figure 6 This is a schematic diagram for performing surface rounding; Figure 7 To import the toolpath diagram for ultra-precision machining into CAM4 software; Figure 8 This is a preview diagram of the toolpath generated using traditional methods; Figure 9 This is a preview diagram of the toolpath generated using the auxiliary surface constructed in this invention. Detailed Implementation

[0010] The invention will now be further described with reference to the accompanying drawings.

[0011] Please see Figures 4 to 9 The present invention provides an embodiment: a method for constructing toolpath-assisted curved surfaces for ultra-precision machining of large curvature optical surfaces, comprising the following steps: Step S1: Perform initial enlargement: Use the "enlarge" command in UG software to uniformly enlarge the original optical surface around the perimeter to form an auxiliary surface with the same curvature as the original optical surface. The purpose of this operation is to reserve operating space for steps 2 and 3, and to avoid subsequent stretching and surface rounding from affecting the curvature of the normal optical surface.

[0012] Step S2: Perform lateral stretching: Use the "Stretch" command in UG software to stretch the enlarged auxiliary surface laterally on both sides. Step S3: Round the surface: Use the "Surface Rounding" command in UG software to round all the connections of the enlarged surface and the lateral stretching surface of the auxiliary surface to form an integrated auxiliary surface with continuous curvature.

[0013] Please continue reading. Figure 4 As shown, in one embodiment of the present invention, the process of uniformly expanding the original optical surface around its perimeter is further described as follows: inputting a value in the pop-up window or manually adjusting the sphere in the red box to match the curvature of the original optical surface.

[0014] Please continue reading. Figure 5 As shown, in one embodiment of the present invention, the stretching direction of the double-lateral stretching is a horizontal direction perpendicular to the normal of the original optical surface, and the extension to the normal of the original optical surface is abandoned. The distance must exceed the maximum processing outer edge of the optical surface. Specific Implementation Example 1:

[0015] Step 1: Initial Expansion Steps Using the "Enlarge" command in UG software (version 12.02), enter the value 20 in the pop-up window or manually adjust the sphere in the red box until it is suitable, uniformly enlarging the original optical surface around its perimeter to form a surface with the same curvature as the original optical surface; for example... Figure 4 As shown.

[0016] Step 2: Lateral stretching step Using the "Extrude" command in UG software, perform a double-lateral extrude on the enlarged auxiliary surface from step 1. The extrude direction is a horizontal direction perpendicular to the normal of the original optical surface, avoiding extension towards the normal of the original optical surface (i.e., the depth direction of the tooling / fixture / machine tool structure to prevent interference). The distance must exceed the maximum machining outer edge of the optical surface. Figure 5 The red line indicated by the arrow shown.

[0017] Step 3: Rounding the surface Using the "Face Rounding" command in UG software, round all connections of the laterally stretched surfaces in steps 1-2; this ensures continuous curvature at each surface connection without abrupt changes, avoiding tool runout (vibration) caused by sudden changes in surface curvature during machining, thus improving machining stability. Figure 6 As shown.

[0018] Based on the integrated, curvature-continuous auxiliary surface constructed in the above three steps, it is imported into CAM4 software to generate ultra-precision machining toolpaths, thus achieving interference-free and highly stable machining of large-curvature optical surfaces. For example... Figure 7 As shown, the gray area indicated by the arrow is the constructed auxiliary surface, and the yellow area indicated by the arrow is the anisotropic optical surface.

[0019] as follows Figure 8 and Figure 9 As shown, this invention abandons the traditional passive mode of directly generating toolpath trajectories based on the curvature of optical surfaces, and instead adds an auxiliary surface, changing from passive to active. The auxiliary surface is constructed through three steps: "expanding the surface + lateral stretching + smooth connection". This operation achieves the dual goals of "range expansion" (avoiding abrupt changes on the original optical surface that affect the optical path) and "interference avoidance". At the same time, the smooth transition process eliminates abrupt changes in surface curvature, solving the tool vibration problem caused by existing interference avoidance technologies. Ultimately, it achieves the dual technical goals of interference avoidance and improved processing stability, which is different from the single optimization and passive adjustment mode of existing technologies.

[0020] The above description is only a preferred embodiment of the present invention and should not be construed as a limitation of this application. All equivalent changes and modifications made in accordance with the scope of the patent application of the present invention should be included in the scope of the present invention.

Claims

1. A method for constructing toolpath-assisted curved surfaces for ultra-precision machining of large curvature optical surfaces, characterized in that: Includes the following steps: Step S1: Perform initial enlargement: Use the "enlarge" command in UG software to uniformly enlarge the original optical surface along the perimeter to form an auxiliary surface with the same curvature as the original optical surface; Step S2: Perform lateral stretching: Use the "Stretch" command in UG software to stretch the enlarged auxiliary surface laterally on both sides. Step S3: Round the surface: Use the "Face Rounding" command in UG software to round all the connections of the enlarged surface and the lateral stretching surface of the auxiliary surface to form an integrated auxiliary surface with continuous curvature.

2. The method for constructing toolpath-assisted curved surfaces for ultra-precision machining of large curvature optical surfaces according to claim 1, characterized in that: Further enlarging the original optical surface uniformly around its perimeter involves entering a value in the pop-up window or manually adjusting the sphere within the red box to match the curvature of the original optical surface.

3. The method for constructing toolpath-assisted curved surfaces for ultra-precision machining of large curvature optical surfaces according to claim 1, characterized in that: The stretching direction of the dual-lateral stretching is a horizontal direction perpendicular to the normal of the original optical surface, abandoning the extension to the normal of the original optical surface, and the distance must exceed the maximum processing outer edge of the optical surface.

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