Method for reconstructing actual model of large-diameter spinning box bottom

Abstract

The invention discloses a method for reconstructing an actual model of a large-diameter spinning box bottom. The method comprises the following steps: processing the box bottom before heat treatment; measuring after heat treatment of the box bottom; model reconstruction: reconstructing the inner molded surface of the box bottom part according to the scanning data; a bridging curved surface or a multi-section curved surface is adopted to fill the space between the adjacent offset curves, and construction of the outer molded surface of the box bottom part is completed; and checking data. According to the method, measurement errors caused by model splicing can be reduced, the boundary position and actual wall thickness data of the outer molded surface of each area of the part can be reflected more accurately, the distribution of the overall machining allowance of the inner and outer molded surfaces of the spinning box bottom can be evaluated more visually and accurately, accurate data support is provided for subsequent turning, and the machining precision is improved. And the reliability of the box bottom part machining process is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of equipment manufacturing, and relates to a method for reconstructing the actual model of a large-diameter spun box bottom. Background Art

[0002] Large-diameter box bottom parts are important components of the carrier rocket box body. The traditional method uses the method of segment welding to form. With the increasing demand for integral manufacturing, the current box bottom is usually prepared by integral spinning or hydroforming. There are certain fluctuations in the surface state of the formed box bottom parts, and the parts will continue to deform after heat treatment. In order to ensure the accuracy of the final surface, it is usually necessary to turn the inner surface. Due to the lack of a reference, in the actual operation process, it is often necessary to reconstruct the actual model in 3D software, and determine the part processing state, formulate the processing plan, and adjust the processing state through a series of methods such as enveloping and measuring, and finally realize the complete turning of the inner surface. Therefore, how to accurately reconstruct the model in 3D software is the technological basis for realizing the inner surface processing.

[0003] At present, the process solution usually adopts the method of continuous scanning of the inner and outer surfaces. However, due to the large scanning area of the parts and the short transition area between the inner and outer surfaces, there are splicing errors in the scanned data, which cannot reflect the true wall thickness, surface state and other data of the parts. Especially for the spun box bottom parts, their technological characteristics determine that the wall thickness has a decreasing distribution trend along the generatrix direction. If there are deviations in the wall thickness data, it may affect the subsequent envelope state design, resulting in quality problems such as out-of-tolerance outer surface dimensions. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for reconstructing the actual model of a large-diameter spun box bottom.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A method for reconstructing the actual model of a large-diameter spun box bottom, comprising the following steps:

[0007] S1. Processing before heat treatment of the box bottom: Fix the box bottom part on the turning fixture, and level the large-end end face of the box bottom; Divide multiple parallel lines on the outer surface of the box bottom at a predetermined interval, and evenly drill round holes in the surplus part cut at the large end. The centers of the evenly distributed holes are located at the bottom scribed line; Perform pre-processing on the small end of the box bottom, cut the water outlet, and process the feature holes at one side ear.

[0008] S2. Measurement after heat treatment of the bottom of the box: After heat treatment of the bottom of the box, perform three-dimensional laser scanning on the inner surface of the bottom of the box to obtain point cloud data; number the evenly distributed holes at the large end, and draw a generatrix from the evenly distributed holes to the center of the small end, mark the intersection points of the generatrix and the scribed lines of the turning process of the bottom of the box, and measure the wall thickness of the marked points.

[0009] S3. Model reconstruction: Reconstruct the inner surface of the bottom part of the box based on the scanned data; use bridge surfaces or multi-section surfaces to fill the space between adjacent offset curves to complete the construction of the outer surface of the bottom part of the box.

[0010] S4. Data inspection: Perform surface deviation detection on the outer surface and the inner surface in regions, and compare the detection results with the wall thickness data to check if they match. If there are deviations, adjust the offset amount of the corresponding intersection points to complete surface correction until the wall thickness data meets the manufacturing requirements.

[0011] As a preferred method, in step S1, fix the bottom of the box to the turning fixture, perform circular runout detection at a predetermined interval in the height direction. If the circular runout exceeds the predetermined threshold, make adjustments. After clamping, perform turning processing on the large end.

[0012] Further preferably, in step S1, the number of evenly distributed holes is 16.

[0013] As a preferred method, in step S2, obtain the point cloud data of the evenly distributed holes at the large end and the feature holes at the small end.

[0014] As a preferred method, in step S3, determine the center positions of the evenly distributed holes based on the scanned data and fit the bottom reference plane; offset the reference plane upward at a predetermined interval to obtain the intersection lines with the reconstructed inner surface to form multiple parallel lines; determine the numbers of the evenly distributed holes according to the positions of the feature holes, establish planes through the centers and the center of the small end respectively to obtain the intersection lines with the reconstructed inner surface to form multiple generatrices; mark the intersection points of the generatrices and the parallel lines, and record the intersection points according to the numbers of the evenly distributed holes; calculate the offset amount of each point, and offset and generate offset points in the corresponding offset plane along the normal direction of the parallel lines; connect the offset points in the same plane to form offset curves.

[0015] Further preferably, the offset amount is calculated by the formula l = t / sinθ, where t is the measured wall thickness value of the corresponding marked point, and θ is the angle between the tangent of the elliptical surface at this point and the horizontal direction; the angle θ is calculated by taking the derivative of the elliptical generatrix equation. Assume the elliptical surface generatrix equation is: where R is the major axis radius, m is the modulus, and x is the radius of the corresponding marked point. Then, taking the derivative of it, we can get: We can get θ = arctan(|m 2 x / y|).

[0016] As a preferred method, in step S3, a three-dimensional modeling software is used to reconstruct the inner surface, and the three-dimensional modeling software is selected from: Creo, Catia or UG.

[0017] The present invention has the following advantages:

[0018] The present invention realizes the reconstruction of the inner and outer surfaces of the actual parts by extracting the features of the bottom box parts and combining the scanning of the inner surface and the wall thickness measurement. Compared with the traditional method of scanning the inner and outer surfaces, it can reduce the measurement error caused by model splicing, more accurately reflect the boundary positions of the outer surfaces of each region of the part and the actual wall thickness data, and more intuitively and accurately evaluate the distribution of the overall machining allowance of the inner and outer surfaces of the spinning bottom box, providing accurate data support for the subsequent turning processing and improving the reliability of the processing technology of the bottom box parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the processing of the water outlet hole before heat treatment;

[0020] Figure 2 It is a schematic diagram of the construction of the offset plane;

[0021] Figure 3 It is a schematic diagram of surface filling. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described in detail below with reference to the drawings.

[0023] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Embodiment:

[0025] A method for reconstructing the actual model of a large-diameter spinning bottom box includes the following steps:

[0026] 1. Machining of the bottom box before heat treatment

[0027] (1) Fix the bottom box part on a special turning fixture, and perform roundness measurement every 50 mm in the height direction. If the roundness exceeds 3 mm, fine-tune the part until the roundness of all points is controlled within 3 mm, which is regarded as qualified clamping, and turn the large end to remove part of the machining allowance;

[0028] (2) Taking the bottom turning plane as the reference, draw parallel lines at intervals of 50 mm in the height direction for the contour line of the outer surface of the bottom box.

[0029] (3) Taking the bottommost marked line as the reference, evenly drill 16 round holes, ensuring that the centers of the evenly distributed holes are at the bottom marked line.

[0030] (4) Preprocess the small end of the box bottom, cut the water outlet, and machine the feature round holes at one side of the hanging ear.

[0031] 2. Measurement after heat treatment of the box bottom

[0032] (1) After heat treatment of the box bottom, perform three-dimensional laser scanning on the inner surface to obtain point cloud data. Focus on scanning the position features of the uniformly distributed holes at the large end and the position features of the feature holes at the small end.

[0033] (2) Take the first uniformly distributed hole to the left of the position of the feature hole at the small end as the starting point, and number the 16 uniformly distributed holes clockwise.

[0034] (3) Take the 16 uniformly distributed hole positions as starting points respectively, and pull 16 generatrices towards the center of the small end by means of wire-pulling. Mark and number the intersection points of the generatrices and the scribed lines of the turning process of the box bottom.

[0035] (4) Use an ultrasonic thickness gauge to measure the wall thickness data of the marked points.

[0036] 3. Model reconstruction

[0037] (1) Reconstruct the inner surface according to the scanned data, especially focus on processing the 16 marked hole features, determine the center positions of the marked holes, and perform comparison measurement on the reconstruction results to ensure that the error is less than 0.1 mm.

[0038] (2) Based on the 16 center points as basic data, fit and construct the bottom reference plane, offset the reference plane upward at intervals of 50 mm, obtain the intersection lines of each plane and the reconstructed inner surface, and determine n parallel lines.

[0039] (3) Determine the numbers of the uniformly distributed holes according to the positions of the feature holes, and establish planes through the centers and the center of the small end respectively, obtain the intersection lines of the planes and the reconstructed inner surface, and determine 16 generatrices.

[0040] (4) Mark the intersection points of the generatrices and the n parallel lines respectively, and record the numbers of the intersection points according to the numbers of the uniformly distributed holes.

[0041] (5) Edit the previous formulas (1), (2) and (4) in the Matlba software, input the wall thickness data of the corresponding points, obtain the corresponding offset amounts, and offset the points in the model in the normal direction of the corresponding parallel lines within the corresponding offset planes to obtain the offset point data.

[0042] (6) In the three-dimensional software, connect the offset points in the same plane with 3D spline curves to form offset curves.

[0043] (7)Finally, the space between adjacent offset curves is filled with multi-section surfaces, etc., to complete the construction of the outer surface.

[0044] 4. Data inspection

[0045] The form deviation is detected for the outer surface and the inner surface in separate regions, and the detection results are compared with the wall thickness data. After checking, the wall thickness deviation in the corresponding region is less than 0.3 mm, meeting the determination requirements for the project, and the reconstruction of the actual model is completed.

[0046] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new combination of steps of any new method or process disclosed.

Claims

1. A method for reconstructing the actual model of the bottom of a large-diameter spinning box, characterized in that, It includes the following steps: S1. Pre - processing before heat - treatment of the bottom of the box: Fix the bottom - of - the - box parts on the turning fixture, and level the large - end end - face of the bottom of the box; Divide multiple parallel lines on the outer surface of the bottom of the box at a predetermined interval, drill equally - spaced round holes in the surplus part cut at the large end, and the centers of the equally - spaced holes are located at the scribed line at the bottom end; Pre - process the small end of the bottom of the box, cut the water outlet, and machine the feature holes at one side of the hanging ear. S2. Measurement after heat - treatment of the bottom of the box: After the heat - treatment of the bottom of the box, perform three - dimensional laser scanning on the inner surface of the bottom of the box to obtain point - cloud data; Number the equally - spaced holes at the large end, and draw generatrices from the equally - spaced holes to the center of the small end, mark the intersection points of the generatrices and the scribed line of the turning process of the bottom of the box, and measure the wall thickness of the marked points. S3. Model reconstruction: Reconstruct the inner surface of the bottom - of - the - box parts according to the scanned data; Use bridge - surface or multi - section surface to fill the space between adjacent offset curves to complete the construction of the outer surface of the bottom - of - the - box parts. S4. Data inspection: Perform surface - deviation detection on the outer surface and the inner surface in regions, and compare the detection results with the wall - thickness data to check whether they match. If there are deviations, adjust the offset amount of the corresponding intersection points to complete surface correction until the wall - thickness data meets the manufacturing requirements.

2. A method for reconstructing the actual model of the bottom of a large-diameter spinning box according to claim 1, characterized in that: In step S1, fix the bottom of the box on the turning fixture, perform circular - runout detection at a predetermined interval in the height direction. If the circular runout exceeds the predetermined threshold, make adjustments. After clamping, machine the large end.

3. A method for reconstructing the actual model of the bottom of a large-diameter spinning box according to claim 1 or 2, characterized in that: In step S1, the number of equally - spaced holes is 16.

4. A method for reconstructing an actual model of a large-diameter spun box bottom according to claim 1, characterized in that: In step S2, obtain the point - cloud data of the equally - spaced holes at the large end and the feature holes at the small end.

5. A method for reconstructing the actual model of the bottom of a large-diameter spinning box according to claim 1, characterized in that: In step S3, determine the positions of the centers of the equally - spaced holes according to the scanned data, and fit the reference plane at the bottom end; Offset the reference plane upward at a predetermined interval to obtain the intersection lines with the reconstructed inner surface to form multiple parallel lines; Determine the numbers of the equally - spaced holes according to the positions of the feature holes, establish planes respectively through the centers and the center of the small end to obtain the intersection lines with the reconstructed inner surface to form multiple generatrices; Mark the intersection points of the generatrices and the parallel lines, and record the intersection points according to the numbers of the equally - spaced holes. Calculate the offset amount of each point, offset and generate offset points in the corresponding offset plane along the normal direction of the parallel lines; Connect the offset points in the same plane to form offset curves.

6. A method for reconstructing an actual model of a large-diameter spun box bottom according to claim 5, characterized in that: The offset is calculated by the formula l = t / sinθ, where t is the actually measured wall thickness value of the corresponding marked point, and θ is the angle between the tangent line of the elliptical surface at this point and the horizontal direction; the angle θ is calculated by taking the derivative of the elliptical generatrix equation. Assuming the elliptical surface generatrix equation is: where R is the major axis radius, m is the modulus, and x is the radius of the corresponding marked point. Then, taking the derivative of it, we can get: We can get θ = arctan(|m 2 x / y|).

7. A method for reconstructing an actual model of a large-diameter spun box bottom according to claim 1, characterized in that: In step S3, use three - dimensional modeling software to reconstruct the inner surface, and the three - dimensional modeling software is selected from: Creo, Catia or UG.

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