An overall machining method for a large-sized continuous grid rib sealed cabin structure

Abstract

An overall machining method for a large-sized continuous grid rib sealed cabin structure. In the state of the sub-cabin structure blank, machining allowances with machining process design features meeting process requirements are processed in the weld area and the cabin interface, and continuous grid rib structural features meeting dimensional requirements are processed in the remaining parts of the sub-cabin. Then, multiple sub-cabin structures are welded by electron beam to form the cabin structure. Finally, overall machining of all features is carried out on the weld area and the cabin interface of the whole cabin. The machining method of the present invention decomposes the overall machining process of the cabin structure into parallel overall machining in the state of multiple sub-cabin structures, improves the overall machining efficiency of the cabin structure, reduces the single-point equipment occupancy rate, ensures the dimensional accuracy after the overall machining of the continuous grid rib sealed cabin structure, has strong practicability and is easy to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of machining, and particularly to an integral machining method for a large-sized continuous grid rib sealed cabin structure, which is applied to the integral machining of a large-sized continuous grid rib sealed cabin to ensure the grid skin thickness, grid rib width and cabin interface accuracy of the sealed cabin. Background Art

[0002] In order to meet higher requirements such as exploring other planets and constructing and maintaining near-earth orbit space stations, higher requirements are put forward for the sealed cabin structure of spacecraft in terms of performance such as structural lightweight, structural load ratio, safety and reusability.

[0003] At present, an integral machining method is adopted for a large-sized continuous grid rib sealed cabin structure. The envelope size of this sealed cabin structure is about Φ4000mm×2500mm. The minimum thickness of the cabin skin is 1.5mm±0.1mm. The flatness of the upper and lower end sealing surfaces of the cabin is 0.15mm, and the parallelism is 0.2mm. The position tolerance of the cabin connection holes is Φ0.2mm. Different from the manufacturing mode of the traditional panel-end frame welded cabin structure, which first processes the flat grid, then forms and welds, this sealed cabin structure directly forms multiple (≥2) sub-cabin structure blanks from thick aluminum alloy plates and then performs electron beam welding to form the sealed cabin structure blank, and then performs full-feature integral machining, as Figures 1 to 2 shown. This manufacturing mode can realize the continuous design of the through-cabin grid ribs in the weld area of the sealed cabin structure, greatly improving the load-bearing performance of the sealed cabin. At the same time, on the premise of meeting the load-bearing performance requirements, the skin thickness in the weld area can be thinned to achieve lightweight manufacturing of the sealed cabin structure. The following problems exist in the integral machining process of this large-sized continuous grid rib sealed cabin structure:

[0004] (1) The internal stress of the formed sub-cabin structure blank is large, and the overall machining stiffness of the cabin structure formed after welding is poor. During the overall machining process, the deformation is large, and it is not easy to achieve high-precision manufacturing;

[0005] (2) The overall machining material removal rate of the cabin structure blank is high, the overall machining cycle is long, and the single-point equipment occupancy rate is high, making it difficult to achieve efficient manufacturing. Summary of the Invention

[0006] The present invention proposes an integral machining method for a large-sized continuous grid rib sealed cabin structure, which solves the technical problem that it is not easy to ensure the integral machining accuracy of the cabin structure.

[0007] The present invention proposes an integral machining method for a large-sized continuous grid rib sealed cabin structure, including:

[0008] Step 1: Turn the sub-cabin structure blank to obtain the inner and outer profiles of the sub-cabin structure;

[0009] Step 2: Milling the outer surface of the sub-cabin structure to form an outer surface grid cavity, which is formed by longitudinally and transversely arranged grid ribs. The machining allowance is reserved for the outer surface of the sub-cabin, the thickness of the grid ribs, and the thickness of the bottom skin of the grid cavity. The surfaces of the weld areas to be welded at the upper and lower openings of the sub-cabin structure are machined to form specified process design features as the circumferential weld areas.

[0010] Step 3: Performing stress relief heat treatment on the sub-cabin structure.

[0011] Step 4: Rigidly supporting the upper and lower openings of the sub-cabin structure, and turning the inner surface of the sub-cabin structure to the specified size.

[0012] Step 5: Flexibly supporting the inner surface of the sub-cabin structure, rigidly supporting the upper and lower openings of the cabin structure, and machining the outer surface and grid cavity of the sub-cabin structure to obtain a grid skin that meets the requirements.

[0013] Step 6: Turning the inner and outer surfaces within the circumferential weld area of the sub-cabin structure to the specified size; among them, a ramp platform allowance area is machined on the inner surface corresponding to the circumferential weld area.

[0014] Step 7: First, cleaning the sub-cabin structure and performing pre-welding assembly to ensure the assembly error of the sub-cabin. Then, the upper and lower openings of the sub-cabin structure and the corresponding ports of other sub-cabin structures are welded by electron beam to form the cabin structure, and the ramp platform allowance area on the inner surface of the circumferential weld area of the cabin structure is removed by turning.

[0015] Step 8: Rigidly supporting the inner surface of the sub-cabin structure, and machining the allowance features in the circumferential weld area to obtain the same structure as the outer surface grid cavity of the sub-cabin structure.

[0016] Step 9: Machining the upper and lower end faces of the cabin structure to obtain upper and lower end sealing surfaces and cabin connection holes, so that the upper and lower end sealing surfaces reach the specified flatness and parallelism, and the cabin connection holes reach the specified position accuracy.

[0017] Further, in Step 9, machining the upper and lower end faces of the cabin structure to obtain upper and lower end sealing surfaces and cabin connection holes specifically includes: first, placing the lower end face of the cabin structure downward for clamping, taking the lower end face as the reference, and milling the upper end to the specified flatness; flipping the cabin structure, taking the milled upper end as the reference, and machining the lower end face according to the total height dimension of the cabin structure to obtain the lower end sealing surface, and machining the cabin connection holes on the lower end sealing surface; flipping the cabin, taking the lower end sealing surface as the reference, machining the upper end face to obtain the upper end sealing surface, and machining the cabin connection holes on the upper end sealing surface.

[0018] Furthermore, in step 9, the flatness of the upper and lower sealing surfaces is 0.15 mm, the parallelism is 0.2 mm, and the specified position tolerance of the cabin connection holes is Φ0.2 mm.

[0019] Furthermore, in step 5, the outer profile surface and the grid cavity of the sub-cabin structure are machined to obtain a grid skin that meets the requirements. Specifically, during the machining of the grid skin, the thicknesses of the 4 corner points and 1 center point of each grid are measured to obtain the spatial position of the bottom skin of the grid and the corresponding deviation range of the skin thickness dimension. If the deviation range of the skin thickness within the grid is not greater than the specified deviation value, compensation machining is performed in the tool axis direction according to the average value of the deviations. During the machining process, the tool axis is kept perpendicular to the tangent plane of the machining point on the bottom skin surface of the grid; if the deviation range of the bottom skin thickness dimension of the grid is greater than the specified deviation value, the machining coordinate system is appropriately adjusted according to the deviation distribution to make the average deviation less than the specified deviation value, and then compensation machining is performed in the tool axis direction.

[0020] Furthermore, in step 6, the thickness of the ramp platform allowance of the inner profile surface corresponding to the circumferential weld area is 2 mm.

[0021] Furthermore, in step 7, the deviation of the quadrant line of the sub-cabin assembly is not greater than 0.2 mm, the assembly gap of the weld between sub-cabin is less than 0.2 mm, and the misalignment is less than 0.3 mm.

[0022] Furthermore, the sub-cabin structure is a cone, a cylinder, a cone-cylinder, a spherical cone or a spherical cylinder.

[0023] The present invention has the following advantages:

[0024] (1) By adopting a method for the overall machining of a large-size continuous grid rib sealed cabin structure, the dimensional accuracy after the overall machining of the continuous grid rib sealed cabin structure is ensured.

[0025] (2) By adopting a parallel overall machining scheme for the sub-cabin structure, the overall machining process of the cabin structure is decomposed into parallel overall machining in the state of multiple sub-cabin structures, which improves the overall machining efficiency of the cabin structure and reduces the single-point equipment occupancy rate.

[0026] (3) The present invention can be applied to the overall machining allowance feature design and cabin dimensional accuracy control of a large-size continuous grid rib sealed cabin structure, and has strong practicability and is easy to implement. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the improvement from a traditional stiffener discontinuous sealed cabin structure of panel-end frame welding to an overall continuous grid rib sealed cabin structure;

[0028] Figure 2Schematic diagram of the overall machining method for the characteristics of the entire cabin after electron beam welding between the blank parts of the sub-cabin structure;

[0029] Figure 3 Schematic diagram of the method of the present invention;

[0030] Figure 4 Schematic diagram of the process design of the margin characteristics in the circumferential weld area of the present invention;

[0031] Figure 5 Measuring characteristic position points during the overall machining of the grid skin of the present invention;

[0032] Figure 6 Overall machining process flow chart of a large-size continuous grid rib sealed cabin structure of the present invention.

[0033] Legend: 1. Schematic diagram of the weld position of the non-continuous rib sealed cabin structure with traditional panel-end frame welding; 2. Overall structure of the continuous grid rib sealed cabin; 3. Weld position of the continuous grid rib sealed cabin; a. Upper sub-cabin structure; b. Lower sub-cabin structure; 4. Blank part of the upper sub-cabin structure; 5. Blank part of the lower sub-cabin structure; 6. Cabin structure blank formed by electron beam welding between the blank parts of the sub-cabin structure; 7. Sealed cabin structure after overall machining of the cabin structure blank; 8. Continuous grid rib sealed cabin structure; 9. Margin characteristics in the circumferential weld area of the upper sub-cabin structure; 10. Margin characteristics in the circumferential weld area of the lower sub-cabin structure; 11. Margin characteristics in the circumferential weld area of the cabin structure formed by electron beam welding of the upper and lower sub-cabin structures; 12. Upper end face of the cabin structure; 13. Lower end face of the cabin structure; 14. Circumferential weld area of the upper sub-cabin structure; 15. Circumferential weld between the upper and lower sub-cabin structures; 16. Design contour of the inner surface of the sealed cabin structure; 17. Circumferential weld area of the lower sub-cabin structure; 18. Slope process design of the margin characteristics in the upper circumferential weld area of the lower sub-cabin structure; 19. Slope process design of the margin characteristics in the upper circumferential weld area of the upper sub-cabin structure; 20. Inner surface of the cabin structure. Detailed implementation mode

[0034] The present invention proposes an overall machining method for a large-size continuous grid rib sealed cabin structure. In the state of the blank parts of the sub-cabin structure, margin characteristic process design and machining are carried out on the weld area and the cabin interface (that is, on the basis of the product theoretical model, margin characteristics are added to meet the requirements of process development), all other characteristics are machined to size as a whole, then multiple (n≥2) sub-cabin structures are electron beam welded, and finally, overall machining of all characteristics is carried out on the weld area and the cabin interface of the entire cabin.

[0035] The overall machining process of a large-size continuous grid rib sealed cabin structure is as follows:

[0036] (1) Benchmark machining of the blank parts of the sub-cabin structure to establish a benchmark for subsequent turning and milling machining.

[0037] (2) For the inner and outer profile surfaces of the rough-turned cabin structure blank, machining allowances are reserved for all the features of the inner and outer profile surfaces of the sub-cabin structure.

[0038] (3) Rough-mill the outer profile surface and the grid cavity on the outer profile surface of the sub-cabin structure blank. The grid cavity on the outer profile surface is formed by grid ribs distributed in a vertical and horizontal cross pattern. Machining allowances are reserved for the outer profile surface of the sub-cabin, the thickness of the grid ribs, and the thickness of the skin at the bottom of the grid cavity. Rough-machine the surface of the weld area of the cabin to be welded at the upper and lower openings of the sub-cabin structure to form specified process design features as the circumferential weld area, so as to facilitate the welding connection of the sub-cabin structure and the machining of the inner and outer profile surfaces after welding.

[0039] (4) Heat-treat the rough-milled sub-cabin structure to eliminate or reduce the internal stress and machining stress of the blank.

[0040] (5) Rigidly support the upper and lower openings of the sub-cabin structure, and finish-turn the inner profile surface of the sub-cabin structure in multiple passes to the required size to ensure the contour accuracy of the inner profile surface of the sub-cabin structure.

[0041] (6) Flexibly support the inner profile surface of the sub-cabin structure, rigidly support the upper and lower openings, finish-mill the outer profile surface and the grid cavity of the sub-cabin structure, and adopt a control method based on detection feedback compensation machining to ensure the dimensional accuracy of the grid skin thickness of the cabin. Milling is performed on the weld area and the cabin interface according to the allowance features, leaving a finish-turning allowance.

[0042] (7) To ensure the welding and assembly accuracy between sub-cabin structures, finish-turn the circumferential weld joint allowance features of the milled sub-cabin structure to remove the finish-turning allowance in step (6). Among them, the inner profile surface corresponding to the weld grid area is designed and machined into a sloped platform allowance to ensure the continuous smoothness of the stepped surface of the inner profile surface of the cabin weld area after subsequent post-welding machining.

[0043] (8) First, clean the sub-cabin structure and perform pre-welding assembly to ensure the assembly error of the sub-cabin. Then, electron beam welding is performed on the corresponding upper and lower openings between multiple sub-cabin structures to form the cabin structure 8, and the sloped platform allowance features on the inner profile surface of the weld area of the cabin structure 8 are finish-turned off;

[0044] (9) Use a steel disc and a screw spherical head to rigidly support the inner profile surface of the circumferential weld area of the cabin structure, and finish-mill the outer profile surface of the circumferential weld area of the cabin structure to obtain the same grid structure as the grid cavity on the outer profile surface of the sub-cabin structure;

[0045] (10) Machine the cabin connection interfaces on the upper and lower end faces of the cabin structure to ensure the flatness and position accuracy of the cabin connection interfaces.

[0046] The following Figures 2 to 6 makes a further specific description of the embodiments of the present invention.

[0047] The large-sized continuous grid rib sealed cabin structure is composed of multiple (the number is greater than or equal to 2) sub-cabin structures. The continuous grid rib sealed cabin structure is formed by circumferentially welding the upper sub-cabin structure a and the lower sub-cabin structure b. The sub-cabin structure can be a rotating body such as a cone, a cylinder, a cone-cylinder, a spherical cone, a spherical cylinder, etc. The inner surface is a rotating smooth surface, and horizontal and vertical grid stiffeners are distributed on the outer surface. The bottom surface of the grid cavity is a thin skin of the cabin.

[0048] A specific implementation step of this method is as follows:

[0049] (1) Perform reference machining on the blanks 4 and 5 of the sub-cabin structures a and b to establish a machining reference for turning and milling processes, that is, accurately position the allowance dimension between the theoretical sub-cabin structure and the sub-cabin structure blank. Usually, determine the allowance dimensions in the end face height direction and circumferential direction of the sub-cabin structure.

[0050] (2) Rough turn the inner and outer surfaces of the sub-cabin structures a and b, and leave a machining allowance of 3 mm to 5 mm for all features.

[0051] (3) Rough mill the outer surfaces and the grid cavities on the outer surfaces of the sub-cabin structures a and b, and leave a machining allowance of 3 mm to 5 mm for all features. Rough mill the allowance features 9, 10, 12, and 13 in the weld area and the cabin interface.

[0052] (4) Perform stress relief heat treatment on the rough-milled sub-cabin structures a and b. The heat treatment temperature is 280 °C and the holding time is 4 h to eliminate or reduce the internal stress and machining stress in the blank.

[0053] (5) Rigidly support the upper and lower openings of the sub-cabin structures a and b, and finish turn the inner surface in multiple passes to the size. Among them, the inner and outer surfaces of the allowance features 9 and 10 in the weld area are not machined temporarily.

[0054] (6) Flexibly support the inner surfaces of the sub-cabin structures a and b with an airbag or foaming glue, etc., and rigidly support the upper and lower openings with columns, steel plates, and screw spherical heads. Finish mill the outer surface and the grid. The following processing based on detection feedback compensation is used to control the thickness dimension of the grid skin: Figure 5P1 - P5 in it are the schematic measurement points of the outer surface grid skin of the cabin before finish machining. During the machining process of the grid skin, the thickness of the 4 corner points P1 - P4 and 1 center point P5 of a single grid is measured to obtain the spatial position and thickness deviation range and average deviation within the grid. If the deviation range within the grid is not greater than 0.15 mm (the skin thickness dimension and tolerance are 1.5 ± 0.1 mm, and the theoretical allowable deviation is 0.2 mm), then the tool axis direction (during the machining process, the tool axis is perpendicular to the tangent plane of the machining point on the bottom skin surface of the grid) is compensated for machining directly according to the mean value of the deviation; if the deviation range within the grid is greater than 0.15 mm, then the machining coordinate system needs to be appropriately adjusted according to the deviation distribution to make the mean deviation less than 0.15 mm, and then the tool axis direction is compensated for machining.

[0055] (7) To ensure the welding and assembly accuracy between the sub - cabin structures, the inner and outer surfaces of the circumferential weld bead allowances 9 and 10 of the sub - cabin structure after finish milling are precision - turned to size. The inner surface 20 corresponding to the product weld grid area is designed as the ramp allowance features 18 and 19 (allowance 2 mm) to ensure that there are no stepped discontinuous surfaces after subsequent post - welding machining.

[0056] (8) After pre - welding cleaning of the sub - cabin structures a and b, pre - welding assembly is carried out. Ensure that the quadrant line deviation on the sub - cabin structures a and b is not greater than 0.2 mm, the weld bead assembly gap is less than 0.2 mm, and the misalignment is less than 0.3 mm. After assembly, spot - weld the sub - cabin structures a and b, and finally form the cabin structure 8 through electron beam welding.

[0057] (9) Precision - turn the area between the inner - surface allowance features 18 and 19 in the weld area of the cabin structure 8 to ensure smooth transition with the inner surface 20 of the cabin.

[0058] (10) Rigidly support the inner surface of the circumferential weld area 11 of the cabin structure with columns, steel discs, and screw spherical heads, and machine the outer surface of the circumferential weld area of the cabin structure. Use the method of controlling the grid skin thickness dimension based on detection and feedback compensation machining in step (6) to machine the outer - surface grid of the circumferential weld area 11.

[0059] (11) Process the upper and lower sealing surfaces 12 and 13 and the cabin connection holes of the processing cabin structure 8, ensuring that the flatness of the upper and lower sealing surfaces 12 and 13 is 0.15 mm, the parallelism is 0.2 mm, and the position tolerance of the cabin connection holes is Φ0.2 mm. First, place the lower end surface 13 of the cabin structure 8 downward for clamping. Taking the lower end surface 13 as the reference, mill the upper end surface 12 to ensure that the entire upper end surface 12 is milled to a new metal surface, which serves as the reference surface for machining after the cabin structure 8 is flipped; flip the cabin structure 8, taking the upper end surface 12 as the reference surface, and considering the overall height dimension of the cabin structure 8, process the lower end surface 13 and the cabin connection holes on the lower end surface 13 to the design dimensions; flip the cabin, taking the lower end surface 13 as the reference, and process the upper end surface 12 and the cabin connection holes on the upper end surface 12 to the design dimensions.

[0060] Compared with the process method of performing overall machining of the whole cabin characteristics after electron beam welding between the present invention and the sub-cabin structure blank, the process method of the present invention can decompose the overall machining process of the cabin structure into parallel overall machining in multiple sub-cabin structure states, which can greatly improve the machining efficiency and solve the problems of long overall machining cycle and high single-point equipment occupancy rate of the cabin structure.

Claims

1. A method for integrally machining a large-size continuous grid rib sealed cabin structure, characterized in that Including: Step 1: Turning the blank parts (4, 5) of the sub-cabin structure to obtain the inner and outer profiles of the sub-cabin structure; Step 2: Milling the outer profile of the sub-cabin structure to form an outer profile grid cavity, which is formed by longitudinally and transversely arranged grid ribs. The machining allowance is reserved for the outer profile of the sub-cabin, the thickness of the grid ribs, and the thickness of the bottom skin of the grid cavity. The surfaces of the weld areas to be welded at the upper and lower openings of the sub-cabin structure are machined to form specified process design features as circumferential weld areas (9, 10); Step 3: Conducting stress relief heat treatment on the sub-cabin structure; Step 4: Rigidly supporting the upper and lower openings of the sub-cabin structure, and turning the inner profile of the sub-cabin structure to the specified size; Step 5: Flexibly supporting the inner profile of the sub-cabin structure, rigidly supporting the upper and lower openings of the cabin structure, and machining the outer profile and grid cavity of the sub-cabin structure to obtain a grid skin that meets the requirements; Step 6: Turning the inner and outer profiles within the circumferential weld areas (9, 10) of the sub-cabin structure to the specified size; among them, slope platform allowance areas (18, 19) are machined on the inner profile (20) corresponding to the circumferential weld areas (9, 10); Step 7: First, cleaning the sub-cabin structure and assembling it before welding to ensure the assembly error of the sub-cabin. Then, electron beam welding is used to form the cabin structure (8) between the upper and lower openings of the sub-cabin structure and the corresponding ports of other sub-cabin structures. The slope platform allowance areas (18, 19) on the inner profile of the circumferential weld areas (9, 10) of the cabin structure (8) are removed by turning; Step 8: Rigidly supporting the inner profile of the sub-cabin structure, and machining the allowance feature (11) in the circumferential weld areas (9, 10) to obtain the same structure as the outer profile grid cavity of the sub-cabin structure; Step 9: Machining the upper and lower end faces of the cabin structure (8) to obtain upper and lower end sealing surfaces (12, 13) and cabin connection holes, so that the upper and lower end sealing surfaces (12, 13) reach the specified flatness and parallelism, and the cabin connection holes reach the specified position tolerance; 2. The method according to claim 1, wherein In Step 9, the machining of the upper and lower end faces of the cabin structure (8) to obtain the upper and lower end sealing surfaces (12, 13) and cabin connection holes specifically includes: First, placing the lower end face of the cabin structure (8) downward for clamping, and milling the upper end to the specified flatness with the lower end face as the reference. Then, flipping the cabin structure (8), machining the lower end face with the milled upper end as the reference according to the total height dimension of the cabin structure (8) to obtain the lower end sealing surface (13), and machining the cabin connection holes on the lower end sealing surface (13). Then, flipping the cabin and machining the upper end face with the lower end sealing surface (13) as the reference to obtain the upper end sealing surface (12), and machining the cabin connection holes on the upper end sealing surface (12).

3. The method according to claim 2, wherein In Step 9, the flatness of the upper and lower end sealing surfaces (12, 13) is 0.15 mm, the parallelism is 0.2 mm, and the specified position tolerance of the cabin connection holes is Φ0.2 mm.

4. The method according to claim 2, wherein In step 5, the outer surface and the grid cavity of the sub-cabin structure are machined to obtain a grid skin that meets the requirements, specifically including: during the machining of the grid skin, the thicknesses of the 4 corner points and 1 center point of each grid are measured to obtain the spatial position of the bottom skin of the grid and the corresponding deviation range of the skin thickness dimension. If the deviation range of the skin thickness within the grid is not greater than the specified deviation value, compensation machining is performed in the tool axis direction according to the average value of the deviation. During the machining process, the tool axis is kept perpendicular to the tangent plane of the machining point on the bottom skin surface of the grid; if the deviation range of the bottom skin thickness dimension of the grid is greater than the specified deviation value, the machining coordinate system is appropriately adjusted according to the deviation distribution to meet the condition that the average value of the deviation is less than the specified deviation value, and then compensation machining is performed in the tool axis direction.

5. The method according to claim 1, wherein In step 6, the thickness of the ramp platform allowances (18, 19) of the inner surface (20) corresponding to the circumferential weld areas (9, 10) is 2 mm.

6. The method according to claim 1, wherein In step 7, the quadrant line deviation of the sub-cabin assembly is not greater than 0.2 mm, the assembly gap of the weld between the sub-cabins is less than 0.2 mm, and the offset is less than 0.3 mm.

7. The method according to claim 1, wherein The sub-cabin structure is a cone, a cylinder, a cone-cylinder, a spherical cone or a spherical cylinder.

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