Adaptive flexible tool holder and machining method for large-size thin-wall skin profile

Abstract

The application provides a large-size thin-wall skin contour surface form following machining method based on an adaptive elastic tool holder, and particularly relates to a large-size thin-wall C / SiC, SiC / SiC composite material skin contour surface form following machining method. In view of the non-homogeneity and anisotropy of the composite material, and the problems of poor consistency, large profile deformation and local area depression of the composite material component blank, the bottleneck problems of under-cutting, over-cutting and size precision out-of-tolerance caused by uneven machining allowance and large profile deformation are easily generated in the machining of the composite material structural component. Based on this, the contour surface form following machining process scheme is provided, an adaptive elastic tool holder is introduced, the axial elastic deformation of the adaptive elastic tool holder is used to adapt to the deviation of the actual profile of the contour surface, the cutting depth of the contour surface under different elastic deformations is explored, the optimal cutting depth range is determined, and finally, the large-size thin-wall skin contour surface high surface quality form following machining is realized.

Description

Technical Field

[0001] This invention provides an adaptive elastic tool holder and a method for machining the outer surface of a large-size thin-walled skin, particularly a conformal machining method for the outer surface of a large-size thin-walled skin suitable for C / SiC and SiC / SiC ceramic matrix composites, belonging to the field of composite material processing. Background Technology

[0002] Large-size thin-walled ceramic matrix composite skins are key components of my country's aerospace equipment, and their manufacturing technology has a crucial impact on the development of aerospace equipment. Large-size ceramic matrix composite skins are characterized by their large size, easily deformable contours, and high requirements for machining accuracy and quality. Their manufacturing technology has always been one of the key challenges in aerospace equipment structural components. Due to the heterogeneous and anisotropic properties of large-size thin-walled ceramic matrix composites, as well as the potential for poor consistency and large contour deformation in the component blanks, composite structural components are prone to bottleneck problems such as undercutting and out-of-tolerance dimensional accuracy issues caused by uneven machining allowances during machining. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art. This invention proposes an adaptive elastic tool holder and a machining method for the outer surface of a large-size thin-walled skin, which effectively solves the problems of heterogeneity and anisotropy of large-size thin-walled ceramic matrix composite materials, as well as the poor consistency and large contour deformation that may exist in the blanks of their components.

[0004] The above-mentioned objectives of the present invention are mainly achieved through the following technical solutions:

[0005] This invention discloses an adaptive elastic tool holder, comprising: a tool holder body, an axial limiting groove, an elastic component, a tool clamping mechanism, and a diamond tool; wherein, a cavity is provided at the rear end of the tool holder body, one end of the elastic component is connected to the axial limiting groove and placed in the cavity, and the other end of the elastic component is connected to the tool clamping mechanism; a groove is provided in the tool clamping mechanism, and one end of the diamond tool is embedded in the groove; when the elastic component is subjected to axial force during the cutting process, it undergoes elastic deformation to generate an elastic force opposite to the direction of the axial force, and the elastic component drives the tool clamping mechanism and the diamond tool to axially extend and retract, so that the diamond tool can perform conformal machining on the outer surface of the material to be machined.

[0006] Furthermore, in the aforementioned adaptive elastic tool holder, one end of the tool clamping mechanism is placed in the cavity of the tool holder body, and the other end is provided with a limiting edge, which serves to restrict the tool clamping mechanism from entering the cavity of the tool holder body completely.

[0007] This invention discloses a method for conformal machining of large-size thin-walled skin outer surfaces based on an adaptive elastic tool holder, characterized in that:

[0008] Clamp the machining fixture for the outer surface onto the machine tool worktable and straighten and align the fixture's reference surface.

[0009] The skin is clamped onto the tooling surface, and evenly distributed pressure strips are used to press the skin and the tooling support surface firmly.

[0010] The convexity ΔH and concaveness Δh of the outer surface are determined by laser scanning of the blank digital model and comparison with the theoretical outer surface.

[0011] Based on the protrusion amount ΔH and the depression amount Δh, determine the theoretical cutting depth (a p ) theory ;

[0012] Based on the theoretical cutting depth (a) p ) theory This yields the actual cutting depth;

[0013] Based on the actual cutting depth, a machining trajectory is compiled, and a machining program is generated through machine tool post-processing.

[0014] Call the machining program to perform conformal machining of the outer surface.

[0015] Furthermore, in the above-mentioned conformal machining method, the step of determining the protrusion amount ΔH and the depression amount Δh by laser scanning the blank digital model and comparing it with the theoretical outer surface specifically involves:

[0016] Using 3D laser scanning technology, the comparison margin between the point cloud coordinates of the skin's outer surface and the theoretical digital model was obtained;

[0017] If the comparison margin Δx of the point cloud coordinates is positive, then the convexity ΔH of the point cloud coordinates is Δx.

[0018] If the comparison margin Δx of the point cloud coordinates is negative, then the concavity of the point cloud coordinates is Δh = Δx.

[0019] The magnitude and distribution area of ​​the protrusion ΔH and indentation Δh of the skin are determined using the least squares method.

[0020] Furthermore, in the above-mentioned conformal machining method, the theoretical cutting depth (a) is determined based on the protrusion amount ΔH and the depression amount Δh. p ) theory Specifically:

[0021] When the machining allowance on the outer surface is uniform, the theoretical depth of cut (a) p ) theory =h, where h is the removal depth of the outer surface;

[0022] When the machining allowance on the outer surface is uneven, when the feed reaches the raised contour of the blank's outer surface, the theoretical depth of cut (a)p ) theory =h+ΔH; When the feed reaches the locally concave region, the theoretical cutting depth (a) p ) theory =h + Δh.

[0023] Furthermore, in the above-mentioned conformal machining method, when the feed reaches the raised contour of the blank's outer surface, the elastic component undergoes adaptive compression, and the actual cutting depth (a) p ) reality =h~h+ΔH; When the feed reaches the locally concave area, the elastic component adaptively rebounds, and the actual cutting depth (a) p ) reality =h~h+Δh.

[0024] Furthermore, in the above-mentioned conformal machining method, the theoretical cutting depth (a) p ) theory Not exceeding 0.40mm.

[0025] Furthermore, in the above-mentioned conformal processing method, the light visibility rate of the conformal surface after conformal processing is ≥85%.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention proposes a method for conformal machining of large-size thin-walled skin outer surfaces based on an adaptive elastic tool holder. By introducing an adaptive elastic tool holder, different theoretical cutting depths (a) are determined. p ) theory The actual depth of cut of the material during cutting (a) p ) reality The corresponding relationship is ultimately used to achieve a light visibility rate of ≥85% on the exterior surface.

[0028] (2) The present invention proposes a method for conformal machining of the outer surface of large-size thin-walled skin based on adaptive elastic tool holder, which meets the requirements of high surface quality machining of the outer surface of large-size thin-walled ceramic matrix composite skin with near-full-area light exposure. It is simple to operate, low in cost, and suitable for widespread application.

[0029] (3) This invention introduces an adaptive elastic tool holder to explore the machinable range of cutting depth, determine the optimal cutting depth range for the outer surface, and establish a numerical correspondence between the theoretical cutting depth and the actual cutting depth of the elastic tool holder. This enables high-quality conformal machining of large-size thin-walled skin outer surfaces with near-full surface exposure. It effectively solves the problems of heterogeneity and anisotropy in large-size thin-walled ceramic matrix composites, as well as the potential for poor consistency and large contour deformation in the component blanks. Furthermore, composite material structural parts are prone to undercutting and dimensional inaccuracies due to uneven machining allowances during machining. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of an adaptive elastic tool holder for conformal machining of large-size thin-walled skin surfaces according to the present invention;

[0031] Figure 2 This is a schematic diagram of a method for conformal processing of the outer surface of large-size thin-walled skin according to the present invention;

[0032] Figure 3 This invention provides a regional tool trajectory design diagram suitable for conformal machining of large-size thin-walled skin surfaces. Detailed Implementation

[0033] Due to the heterogeneity and anisotropy of composite materials, as well as the potential for poor consistency, large contour deformation, and localized depressions in the component blanks, composite structural parts are prone to bottleneck problems in machining, such as undercutting, overcutting, and out-of-tolerance dimensional accuracy caused by uneven machining allowances and large contour deformation.

[0034] like Figure 1 As shown, this invention discloses an adaptive elastic tool holder, comprising: a tool holder body 1, an axial limiting groove 2, an elastic component 3, a tool clamping mechanism 4, and a diamond tool 5; wherein, a cavity is provided at the rear end of the tool holder body 1, one end of the elastic component 3 is connected to the axial limiting groove 2 and placed in the cavity, and the other end of the elastic component 3 is connected to the tool clamping mechanism 4; a groove is provided in the tool clamping mechanism 4, and one end of the diamond tool 5 is embedded in the groove; when the elastic component 3 is subjected to axial force during the cutting process, it undergoes elastic deformation to generate an elastic force opposite to the direction of the axial force, and the elastic component 3 drives the tool clamping mechanism 4 and the diamond tool 5 to axially extend and retract, so that the diamond tool 5 performs conformal machining on the outer surface of the material to be processed.

[0035] Preferably, one end of the tool clamping mechanism 4 is placed in the cavity of the tool holder body 1, and the other end is provided with a limiting edge, which serves to restrict the tool clamping mechanism 4 from entering the cavity of the tool holder body 1 completely.

[0036] This invention discloses a method for conformal machining of large-size thin-walled skin outer surfaces based on an adaptive elastic tool holder, characterized in that:

[0037] Clamp the machining fixture for the outer surface onto the machine tool worktable and straighten and align the fixture's reference surface.

[0038] The skin is clamped onto the tooling surface, and evenly distributed pressure strips are used to press the skin and the tooling support surface firmly.

[0039] The convexity ΔH and concaveness Δh of the outer surface are determined by laser scanning of the blank digital model and comparison with the theoretical outer surface.

[0040] The theoretical cutting depth (a) is determined based on the protrusion amount ΔH and the depression amount Δh. p ) theory ;

[0041] Based on the theoretical cutting depth (a) p ) theory This yields the actual cutting depth;

[0042] Based on the actual cutting depth, a machining trajectory is compiled, and a machining program is generated through machine tool post-processing.

[0043] Call the machining program to perform conformal machining of the outer surface.

[0044] Preferably, the protrusion amount ΔH and the depression amount Δh are determined by laser scanning of the blank digital model and comparing it with the theoretical outer surface, specifically as follows:

[0045] Using 3D laser scanning technology, the comparison margin between the point cloud coordinates of the skin's outer surface and the theoretical digital model was obtained;

[0046] If the comparison margin Δx of the point cloud coordinates is positive, then the convexity ΔH of the point cloud coordinates is Δx.

[0047] If the comparison margin Δx of the point cloud coordinates is negative, then the concavity of the point cloud coordinates is Δh = Δx.

[0048] The magnitude and distribution area of ​​the protrusion ΔH and indentation Δh of the skin are determined using the least squares method.

[0049] Preferably, the theoretical cutting depth (a) is determined based on the protrusion amount ΔH and the depression amount Δh. p ) theory Specifically:

[0050] When the machining allowance on the outer surface is uniform, the theoretical depth of cut (a) p ) theory =h, where h is the removal depth of the outer surface;

[0051] When the machining allowance on the outer surface is uneven, when the feed reaches the raised contour 6 of the blank's outer surface, the theoretical depth of cut (a) p ) theory =h+ΔH; When the feed reaches the locally concave region, the theoretical cutting depth (a) p ) theory =h + Δh.

[0052] Preferably, when the feed reaches the raised contour 6 on the outer surface of the blank, the elastic component 3 undergoes adaptive compression, and the actual cutting depth (a) p ) reality =h~h+ΔH; When the feed reaches the locally concave area, the elastic component 3 adaptively rebounds, and the actual cutting depth (ap ) reality =h~h+Δh.

[0053] Preferably, the theoretical depth of cut (a) p ) theory Not exceeding 0.40mm.

[0054] Preferably, the light visibility rate of the outer surface after conformal processing is ≥85%.

[0055] When the indentation Δh ≤ 0.40 mm, the theoretical cutting depth (a) p ) theory = The average value of the indentation amount Δh for a certain number of samples; when the indentation amount Δh > 0.40 mm, the theoretical cutting depth (a p ) theory = 0.4mm. Theoretical depth of cut (a) p ) theory This is the theoretically maximum amount that needs to be executed to achieve near-full-surface machining without causing fiber misalignment. Actual depth of cut (a) p ) reality This is the actual cutting depth set in the program to achieve the theoretical cutting depth mentioned above.

[0056] During the conformal machining of the outer surface, the tool holder will undergo axial expansion and contraction due to axial cutting, resulting in a decrease in the actual cutting depth (a) set in the programming. p ) reality This changes accordingly, and the actual cutting depth (a) p ) reality With theoretical depth of cut (a) p ) theory The range of the difference can be obtained by measuring the thickness difference ΔM at multiple target positions before and after machining, using targets attached to the outer surface. Based on this, a specific theoretical cutting depth (a) can be obtained. p ) theory The corresponding actual cutting depth (a) p ) reality The numerical range.

[0057] Example

[0058] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings.

[0059] like Figure 1 This is a schematic diagram of an adaptive elastic tool holder suitable for conformal machining of large-size thin-walled skin surfaces. As shown in the diagram, the adaptive elastic tool holder includes a tool holder body 1, an axial limiting groove 2, an elastic component 3, a tool clamping mechanism 4, and a diamond tool 5.

[0060] like Figure 2This is a schematic diagram of the actual tool path of a cutting tool suitable for conformal machining of large-size thin-walled skin outer surface according to the present invention. The diagram includes the raised contour of the blank outer surface 6, the contour of the outer surface after conformal machining 7, the theoretical digital model contour of the outer surface 8, the concave contour of the blank outer surface 9, and the contour of the outer surface after conformal machining 10.

[0061] Figure 3 This is a regional tool trajectory design diagram for conformal machining of the outer surface of a large-size thin-walled skin according to the present invention. As can be seen from the diagram, the inner surface of the skin is tightly fitted with the support fixture 12 through the evenly distributed pressure strips 11.

[0062] In this embodiment, a 1.5M-scale ceramic matrix composite thin-walled skin is selected, and its outer surface is shaped accordingly. The specific process is as follows:

[0063] To address the heterogeneity and anisotropy of composite materials, as well as the potential for poor consistency, large contour deformation, and localized depressions in the component blanks, composite structural parts are prone to bottleneck problems during machining, such as undercutting, overcutting, and out-of-tolerance dimensional accuracy due to uneven machining allowances and large contour deformations. Therefore, an adaptive elastic tool holder is introduced, comprising a tool holder body 1, an elastic component 3, an axial limiting groove 2, a tool clamping mechanism 4, and a diamond tool 5.

[0064] The elastic component 3, the axial limiting groove 2, and the tool clamping mechanism 4 are all located inside the tool holder body 1. One end of the elastic component is connected to the tool clamping mechanism 4, and the other end is connected to the axial limiting groove 2. The extension and retraction of the elastic component 3 drives the tool clamping mechanism 4 and the diamond tool 5 to move axially.

[0065] When the elastic component 3 is subjected to axial force during the cutting process, it undergoes elastic deformation. The elastic force generated by the elastic component 3 and the axial force are a pair of action and reaction forces. At this time, the elastic component 3 drives the tool clamping mechanism 4 and the diamond tool 5 at the moving end to axially extend and retract, and material removal occurs on the actual outer surface.

[0066] Diamond tool 5 performs machining along the actual contour of the outer surface, with the thickness removed from the outer surface set to h and the depth of cut set to a. p When the machining allowance on the outer surface is uniform, a p=h; In the case of uneven machining allowance on the outer surface, when the feed reaches the locally protruding area, the elastic component 3 undergoes adaptive compression. At this time, the theoretical machining allowance should be h+ΔH, but the actual machining allowance generated by the contraction of the elastic component 3 is in the range (h, h+ΔH), and the actual contour of the tool position point is between the protruding area and the theoretical model. When the feed reaches the locally concave area, the elastic component 3 adaptively rebounds. At this time, the theoretical machining allowance should be h+Δh, but the actual machining allowance generated by the rebound of the elastic component 3 is in the range (h, h+Δh), and the actual contour of the tool position point is between the concave area and the theoretical model.

[0067] The point cloud coordinates of the skin's outer surface, obtained through 3D laser scanning technology, are compared with the theoretical digital model. Regions with positive margins after comparison represent areas that bulge relative to the theoretical model, while regions with negative margins represent areas that are concave relative to the theoretical model. Using the least squares method, the magnitude and distribution area of ​​the skin's bulge ΔH and concavity Δh are determined. In this embodiment, the maximum value of Δh (Δhmax) < 0.4 mm. The average value of the concavity Δh (Δhaverage) = 0.27 mm is obtained by taking 50 samples from the concave area.

[0068] Based on the trial cutting experiment, when the actual cutting depth (a p ) reality When the thickness is 0.50 mm, the thickness difference at the target point on the outer surface ranges from 0.14 to 0.18 mm; when the actual cutting depth (a) p ) reality When the thickness is 1.0 mm, the thickness difference at the target point on the outer surface ranges from 0.24 to 0.3 mm; this embodiment uses the actual cutting depth (a). p ) reality =1.0mm, at this point the theoretical cutting depth (a) p ) theory The range is 0.24 to 0.3 mm.

[0069] Using the outer surface of the three-dimensional digital model based on the skin theory as the programming surface, the machining trajectory is compiled using a region-based approach.

[0070] Considering the cutting compatibility between the diamond tool 5 and the ceramic matrix composite material and the requirement for high machining efficiency, the type of diamond tool 5 was determined to be a spherical diamond grinding head with a diameter of D20R10 for machining arc-shaped surfaces.

[0071] Through the processing and inspection of the workpiece in this example, the final result is that the surface light visibility rate is ≥85%.

[0072] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention in order to depart from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for conformal machining of large-size thin-walled skin outer surface based on adaptive elastic tool holder, characterized in that, An adaptive elastic tool holder is adopted, comprising: The adaptive elastic tool holder includes: a tool holder body (1), an axial limiting groove (2), an elastic component (3), a tool clamping mechanism (4), and a diamond tool (5); wherein, a cavity is provided at the rear end of the tool holder body (1), one end of the elastic component (3) is connected to the axial limiting groove (2) and placed in the cavity, and the other end of the elastic component (3) is connected to the tool clamping mechanism (4); a groove is provided in the tool clamping mechanism (4), and one end of the diamond tool (5) is embedded in the groove; The processing method is as follows: Clamp the machining fixture for the outer surface onto the machine tool worktable and straighten and align the fixture's reference surface. The skin is clamped onto the tooling surface, and evenly distributed pressure strips are used to press the skin and the tooling support surface firmly. The convexity ΔH and concaveness Δh of the outer surface are determined by laser scanning of the blank digital model and comparison with the theoretical outer surface. Based on the protrusion amount ΔH and the depression amount Δh, determine the theoretical cutting depth (a p ) theory ; Based on the theoretical cutting depth (a) p ) theory This yields the actual cutting depth; Based on the actual cutting depth, a machining trajectory is compiled, and a machining program is generated through machine tool post-processing. Call the machining program to achieve conformal machining of the outer surface; The process of determining the protrusion amount ΔH and the depression amount Δh by laser scanning the blank digital model and comparing it with the theoretical external surface is as follows: Using 3D laser scanning technology, the comparison margin between the point cloud coordinates of the skin's outer surface and the theoretical digital model was obtained; If the comparison margin Δx of the point cloud coordinates is positive, then the convexity of the point cloud coordinates ΔH = Δx. If the comparison margin Δx of the point cloud coordinates is negative, then the concavity of the point cloud coordinates is Δh = Δx. The size and distribution area of ​​the skin's bulge ΔH and depression Δh are determined using the least squares method. Based on the protrusion amount ΔH and the depression amount Δh, the theoretical cutting depth (a) is determined. p ) theory Specifically: When the machining allowance on the outer surface is uniform, the theoretical depth of cut (a) p ) theory =h, where h is the removal depth of the outer surface; When the machining allowance on the outer surface is uneven, when the feed reaches the raised contour (6) of the blank outer surface, the theoretical cutting depth (a) p ) theory = h + ΔH; When the feed reaches the locally concave region, the theoretical cutting depth (a p ) theory = h + Δh; When the feed reaches the raised contour (6) of the blank outer surface, the elastic component (3) undergoes adaptive compression, and the actual cutting depth (a) p ) reality =h~h+ΔH;When the feed reaches the local concave area, the elastic component (3) adaptively rebounds, and the actual cutting depth (a p ) reality =h~h+Δh.

2. The method for conformal machining of large-size thin-walled skin outer surface based on adaptive elastic tool holder according to claim 1, characterized in that: The theoretical cutting depth (a) p ) theory Not exceeding 0.40mm.

3. The method for conformal machining of large-size thin-walled skin outer surface based on adaptive elastic tool holder according to claim 1, characterized in that: The surface of the conformal processing shape has a light visibility rate of ≥85%.

Images