Overall box bottom allowance coordination, clamping alignment and deformation control thinning machining method

Abstract

The invention provides an overall box bottom allowance coordination, clamping alignment and deformation control thinning machining method which comprises the following steps that S1, a blank is clamped according to a spinning forming transfer datum line, and rough alignment is conducted; s2, performing metering detection on the blank to obtain detection data; s3, carrying out reverse modeling on the blank according to the measurement data obtained in the step S2; s4, according to the theoretical model reference mapping coordination allowance, determining the maximum allowance of the blank enveloping product by adjusting the model position in the step S3; s5, turning and clamping the process edge; s6, rough turning of the appearance; s7, turning over, clamping and aligning are carried out, and rapid clamping and positioning during turning of the inner shape are completed through a clamping process edge and a clamping tool; s8, the inner shape is subjected to finish turning according to the product coordination allowance and inner shape theoretical surface data; s9, turning over, clamping and aligning are conducted again, and quick clamping and positioning are conducted when the appearance is subjected to finish turning; and S10, the product appearance metal allowance is machined in a layered mode till the design model requirement is met. By means of the method, precise machining of ultra-large diameter-thickness ratio overall box bottom thinning deformation control can be achieved, and machined products can meet the design requirement.

Description

Technical Field

[0001] The invention belongs to the field of box body processing, and in particular relates to a method for thinning processing of overall box bottom margin coordination, clamping alignment and deformation control. Background Art

[0002] The tank bottom is an important part of the launch vehicle propellant tank. Traditional rocket tanks are made using the "fragmented milling + welding" process. Figure 1 As shown. This process has a series of problems such as poor surface consistency, difficult thickness control, many welds, low reliability of bottom quality, and environmental pollution. With the continuous improvement of scientific and technological manufacturing level, the overall manufacturing of the bottom has become the development direction of bottom tank processing in the future.

[0003] The integrally formed box bottom has the advantages of short manufacturing cycle, high reliability, no welds, no pollution, etc. The box bottom profile is mostly ellipsoidal or spherical structure, with a maximum diameter of Φ3800mm. The profile has thin and thick area characteristics, the thickness of the thin area is 3.6mm, and the wall thickness accuracy needs to reach ±0.25mm. Figure 2 As shown. According to the design weight reduction requirements and precision requirements, the internal and external surface features need to be thinned on a large scale after the overall forming process to ensure the wall thickness design size requirements. CNC cutting is a green and feasible solution to ensure the theoretical thickness of the box bottom after the overall box bottom is formed, but it is restricted by factors such as the box bottom's large diameter-to-thickness ratio, poor rigidity, large random deformation, and high precision, and has always lacked a mature and reliable process method.

[0004] According to the product structure and blank characteristics of the box bottom parts, the "turning first, then milling" process is adopted during mechanical processing. Turning completes the inner and outer contour processing of the overall box parts, and milling completes the box opening processing. Before processing, the blank needs to be clamped, aligned, and the allowance coordinated, that is, the process of finding the optimal position for the part placement in the blank and making the machining coordinate system of the CNC machine tool match the optimal position.

[0005] Affected by factors such as the thickness of the spun bottom blank, the roundness control and the overall processing of the fork-shaped ring, the product allowance data enclosed by the blank cannot be determined and the allowance is small. This puts forward high technical requirements for the alignment accuracy and allowance coordination level of such parts. Traditional machining alignment methods often cannot meet the processing requirements of such products. In addition, during the processing, the uneven release of residual stress of the material causes large deformation of the workpiece during processing, and the thickness accuracy is difficult to guarantee. Therefore, it is urgent to propose a processing method for allowance coordination, clamping alignment and deformation control for integral box bottom parts.

[0006] The existing solution for the overall box bottom is to first carve the inner shape and then the outer shape, and finally perform milling. Due to the large diameter-to-thickness ratio of the product, poor structural rigidity, high dimensional accuracy requirements, and the small margin of the blank enveloping the product, there are great technical difficulties in processing, and the processed product cannot meet the design requirements. The main processing problems are as follows:

[0007] (1) The allowance of the incoming material is unknown and small: Due to the product characteristics (the fork-shaped ring and the bottom of the thin and thick area are processed in one piece) and the poor roundness of the incoming material, it is impossible to confirm whether there is a processing allowance that meets the use requirements before processing, and after confirmation, the product can have a small coordinated allowance, which leads to a high quality risk;

[0008] (2) Difficulty in clamping. The product has an ellipsoidal surface and no clamping points. During the processing, the clamping angle pieces need to be welded twice. The clamping process is cumbersome and the cycle is long.

[0009] (3) Excessive wall thickness: Due to the uneven release of residual stress in the material during the processing, the workpiece undergoes large random deformation, the processing thickness cannot meet the design requirements, and accurate processing of the overall box bottom cannot be achieved. Invention content

[0010] In view of this, the present invention aims to propose a method for overall box bottom margin coordination, clamping alignment and deformation control thinning processing to solve at least one technical problem in the background technology.

[0011] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0012] A method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation, comprising the following steps:

[0013] S1: Clamp the blank according to the spinning transfer reference line and perform rough alignment;

[0014] S2: Perform meter testing on the blank to obtain measurement data;

[0015] S3: reverse modeling the blank according to the measurement data obtained in step S2;

[0016] S4: According to the theoretical model benchmark mapping coordination margin, the maximum margin of the blank envelope product is determined by adjusting the model position of step S4;

[0017] S5: The clamping process edge is turned with a safety margin on the outer circle of the theoretical large end of the product, which is used to complete the precise and fast clamping process when turning the inner and outer shapes;

[0018] S6: Perform a rough turning process of the product shape according to the maximum margin obtained in step S5;

[0019] S7: Turn over and clamp for alignment, and use the clamping process edge and clamping tools to quickly clamp when finishing the inner shape;

[0020] S8: Refine the inner shape according to the product coordination allowance and the inner shape theoretical surface data;

[0021] S9: Turn over and clamp again for alignment, and quickly clamp when finishing the shape;

[0022] S10: Process the product shape allowance in layers until it meets the design requirements.

[0023] Furthermore, in step S2, the ellipsoidal spun product is placed on the lathe table with the large end of the pressed bottom facing downward and the small end facing upward. The forming process baseline obtained in step S1 is used as a reference to use the lathe dial indicator to mark the base line, and the base line is leveled by adding a gasket to the lower end of the spun bottom. The machine tool dial indicator is used to measure the roundness of the spun bottom shape. The roundness is adjusted to the minimum by prying the product. The first pressing plate is used to press the large end of the bottom of the spun bottom to complete the clamping and alignment of the blank.

[0024] Furthermore, in step S3, a dial indicator is used to measure designated measuring points of the blank shape in coordination with the rotation of the lathe, and the radius and height dimensions of the measuring points of the blank shape are measured.

[0025] The maximum and minimum values ​​of the roundness of the blank alignment reference line are found by using a table, and set as the measuring points of the outer surface of the spun bottom blank. 16 busbars are evenly distributed around the spun bottom, two of which involve the maximum and minimum values ​​of the roundness. A measuring point is set on each busbar at an interval of 100mm, and there are 23 measuring points on each busbar, a total of 368 measuring points, to obtain the measurement data.

[0026] Furthermore, in step S3, the 368 points measured above are processed in reverse process. First, 16 generatrix spline curves are generated using the coordinates of the 23 measuring points of each generatrix; secondly, 23 circumferential spline curves are generated using the coordinates of the 16 measuring points at the same latitude, and the inner contour surface of the spinning bottom is reversely generated using the generatrix curve and the circumferential curve. The inner contour surface is offset outward with equal thickness to the minimum thickness of the actual blank to obtain the blank limit inner contour surface. The generation of the inner and outer blank surfaces completes the reverse modeling of the blank.

[0027] Furthermore, the coordination margin in step S4 includes

[0028] A1: Determine the rotation center of the blank, which is located at the large end face of the blank;

[0029] A2: Adjust the rotation center of the theoretical model to coincide with the rotation center of the large end of the spun bottom blank;

[0030] A3: The theoretical model is translated vertically up and down. During the translation process, the margins at each position of the spinning bottom theoretical model are constantly changing. Taking any cross section as an example, when the margins of the inner and outer envelopes of the blank are the largest, this point is the optimal point. At this time, the best position of the product in the blank envelope is found.

[0031] Furthermore, in step S5, a precise and rapid clamping scheme for turning the inner and outer shapes of the overall box bottom is designed according to the optimal position of the parts after the allowance is coordinated, and the turning and clamping process edge is performed with a safety margin left on the outer circle of the large end of the theoretical product, so as to realize precise and rapid clamping of turning the inner and outer shapes.

[0032] Furthermore, in step S6, the product shape rough turning process is performed according to the maximum margin obtained in step S5. During rough turning, the residual stress existing in the part itself should be released to the maximum extent while leaving a safe shape margin. The processing deformation caused by rough turning of the shape is turned off through the subsequent inner shape turning process. During shape finishing, the amount of cutting is turned in layers according to the margin situation to reduce the wall thickness tolerance, thereby achieving processing deformation control. In addition, according to the maximum margin obtained in step S4, the clamping process edge is turned while leaving a safe margin on the outer circle of the large end of the product.

[0033] Furthermore, the method for using the turning inner-shaped clamping structure in step S7 is as follows:

[0034] B1: Place the product's rotating bottom hanger in the box processing auxiliary support ring;

[0035] B2: Use the lathe dial indicator to measure the reference line to level the bottom of the box;

[0036] B3: Use the clamping assembly to clamp and fix the product, use several jacks with adjustable stroke to support the lower end of the clamping process edge, and then use additional jacks to press down and fix the upper end of the process edge, so as to achieve accurate and fast clamping of the product at the bottom of the box.

[0037] Furthermore, in step S9, the product is turned over again, clamped and aligned. The product is quickly clamped, including evenly distributing a number of inner support blocks arranged along the circumference on the lathe worktable. According to the diameter of the inner shape of the large end of the spun bottom, the clearance between the inner support block and the product is strictly controlled to be within 0.1mm, and the outer diameter of the inner support block is matched to make it correspond to the inner diameter of the large end of the product.

[0038] The inner support block is fixed on the lathe workbench by using a fixing screw and a fixing nut to press the spun bottom product downward, tightly fitting with the 16 inner support blocks, and controlling the matching clearance to be less than 0.1mm, so that the spun bottom product can automatically find the roundness.

[0039] The large end of the spun bottom shape is fixed by a third pressure plate, nut, screw and other tools to clamp the edge of the product.

[0040] Compared with the prior art, the overall box bottom margin coordination, clamping alignment and deformation control thinning processing method created by the present invention has the following advantages:

[0041] Aiming at the problems of small allowance, difficult clamping and large deformation in the machining process of a 3.8m diameter integral spun bottom part, a method of allowance coordination based on blank detection, reverse modeling and datum mapping, a precise and fast clamping scheme based on datum mapping optimization and a full-process turning process scheme based on cyclic stress release method were designed. Based on the above invention, the precise clamping, coordinated utilization of allowance and deformation control of the 3.8m diameter integral spun bottom can be achieved, which can effectively avoid the occurrence of 90% of quality problems, reduce product circulation and waiting time, and reduce the processing cycle from the original 21-22 days to the current 14-15 days (the processing cycle is reduced by 7 days), which improves the processing efficiency and benefits. The product processing quality has been effectively improved, and the wall thickness difference has been reduced from the original 5.5-6.5mm to the current 2.5-3.5mm. It fills the gap in the manufacturing field of 3.8m diameter integral spun bottom parts, realizes the comprehensive improvement of the machining wall thickness accuracy, carrying efficiency, product reliability, etc. of the ultra-large diameter-to-thickness ratio thin curved bottom, and provides theoretical and technical reference for the national pre-research and future liquid rocket model tank bottom high-efficiency, high-quality, and high-efficiency design and manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0043] Figure 1 It is a schematic diagram of a welded box bottom in the prior art;

[0044] Figure 2 This is a schematic diagram of the overall box bottom of the present invention;

[0045] Figure 3 This is a schematic diagram of the measuring points of the present invention;

[0046] Figure 4 This is a schematic diagram of data reverse modeling according to the present invention;

[0047] Figure 5 This is a schematic diagram of optimizing the position of a product model according to the present invention;

[0048] Figure 6 It is a schematic diagram of the clamping process edge of the present invention;

[0049] Figure 7 It is the cyclic stress release process of the rough turning process described in the present invention;

[0050] Figure 8 This is a schematic diagram of the coordination between the product of the present invention and the support ring;

[0051] Fig. 9 This is the overall diagram of the in-vehicle clamping according to the present invention;

[0052] Fig.10 This is a partial enlarged view of the edge clamping of the fine turning inner shape process described in the present invention

[0053] Fig.11 This is a schematic diagram of the clamping of the inner support block described in the present invention.

[0054] Description of reference numerals:

[0055] 1. Auxiliary support ring; 2. Square box; 3. Jack one; 4. Jack two; 5. Adjusting screw; 6. Second pressure plate; 7. Fixing screw; 8. Fixing nut; 9. Inner support block. DETAILED DESCRIPTION

[0056] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0057] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0058] Affected by factors such as the thickness limit of the spinning bottom of the forming process, the precision control after forming and the characteristics of the product itself, the margin of the blank enveloping the product is often tight, and the minimum margin on one side is sometimes only about 0.5 to 1 mm. Through the margin coordination method based on blank detection, reverse modeling, and reference mapping, the product's coordinated margin can be accurately determined, and the optimal position for part placement can be quickly located in the blank to minimize margin loss. It mainly includes the following steps:

[0059] S1 Forming datum transfer: In the spinning process, a continuous forming process datum line is engraved on the large end of the blank according to the large end allowance of the product.

[0060] S2 Clamping and rough alignment. Place the ellipsoidal spinning bottom on the lathe table with the large end facing down and the small end facing up. Use the lathe dial indicator to level the datum line with the forming datum line as a reference, and add a shim to the lower end of the spinning bottom. Use the machine tool dial indicator to measure the roundness of the spinning bottom, and adjust the roundness to the minimum by prying the product. Use the first pressing plate to press the large end of the bottom of the spinning bottom to complete the blank clamping and alignment.

[0061] S3 Blank inspection. Use a dial indicator to measure the specified measuring points of the blank shape in conjunction with the rotation of the lathe, and measure the radius and height dimensions of the blank shape measuring points.

[0062] The maximum and minimum values ​​of the roundness of the blank alignment reference line are found by using a table, and set as the measuring points of the outer surface of the spun bottom blank. There are 16 busbars evenly distributed around the spun bottom, two of which involve the maximum and minimum values ​​of the roundness. A measuring point is set at an interval of 100mm on each busbar, and there are 23 measuring points on each busbar, for a total of 368 measuring points. Figure 3 As shown. The point set of each busbar is set to Q t , denoted as [R t (i), Z t (i)], where t = 1, 2, ... 16 represents the measurement position of the busbar, a total of 16. i = 1, 2, ... 23, represents 23 measurement points with an interval of 100 mm in the busbar direction.

[0063] S4 reverse modeling. The 368 points measured above are processed in reverse process. First, 16 generatrix spline curves are generated using the coordinates of the 23 measuring points of each generatrix; secondly, 23 circumferential spline curves are generated using the coordinates of the 16 measuring points at the same latitude. The inner contour surface of the spun bottom is reversely generated using the generatrix curve and the circumferential curve. The inner contour surface is offset outward with equal thickness to the minimum thickness of the actual blank to obtain the blank limit inner surface. The generation of the inner and outer blank surfaces completes the reverse modeling of the blank, such as Figure 4 shown.

[0064] S5 theoretical model benchmark mapping coordinates the allowance. By adjusting the model position, the maximum allowance of the blank enveloping the product is determined, and the optimal position of the part in the blank is quickly determined to minimize the allowance loss. The specific steps are as follows:

[0065] 1) Determine the center of rotation of the blank, which is located at the large end face of the blank.

[0066] 2) Adjust the rotation center of the theoretical model to coincide with the rotation center of the large end of the spun bottom blank.

[0067] 3) The theoretical model is translated vertically up and down. During the translation process, the margins of each position of the spinning bottom theoretical model are constantly changing. Taking any cross section as an example, when the margins of the inner and outer envelopes of the blank are the largest, this point is the optimal point. At this time, the best position of the product in the blank envelope is found, such as Figure 5 shown.

[0068] S6 designs the precise and fast clamping scheme for turning the inner and outer shapes of the overall box bottom according to the optimal position of the parts after the allowance coordination. The turning and clamping process edge is used to realize the precise and fast clamping of turning the inner and outer shapes, such as Figure 6 shown.

[0069] S7 rough turning of the shape. Before turning the shape, the process edge is fixed and clamped by using tools such as pressure plates, nuts, screws, etc., and the shape rough turning process is carried out according to the shape allowance coordinated by the product.

[0070] Due to the thickness of the fork ring tip and the overall forming manufacturing accuracy, the outer spherical surface needs to remove a large amount of allowance, which is generally dozens of times the final thickness. The product deformation caused by a large amount of turning of the outer spherical surface must be considered, so a rough turning process is used. During rough turning, the residual stress in the part itself should be released as much as possible while leaving a safe outer shape allowance. The deformation of the workpiece caused by outer shape turning can be removed through the subsequent inner turning process. Cyclic stress release methods such as Figure 7 During the turning process of the outer surface, 2-3 times of turning and cutting are performed according to the excess, and the second pressure plate is released to release the processing deformation. However, a certain degree of limitation is required based on the deformation of the previous times to avoid the situation where the product excess is insufficient and cannot be processed due to processing deformation.

[0071] The turning of the overall box bottom with a super large diameter-to-thickness ratio is a key process in the overall plan. This process removes the largest amount of excess and forms an inner surface reference and a fork-shaped ring structure. The main problems that need to be solved in the turning process of the overall box bottom with a super large diameter-to-thickness ratio, such as the coordination of excess, clamping methods, turning stress release, and product deformation control, are all major problems that need to be solved. This patent provides a full-process turning process solution based on the cyclic stress release method. It releases some residual stress by rough turning part of the outer shape excess in advance, and turns away the workpiece deformation caused by outer shape turning during the inner shape turning process. Finally, the outer shape is finely turned to improve the problems of large workpiece processing deformation and excessive wall thickness.

[0072] S8 is turned over and clamped for alignment. The specific steps are as follows:

[0073] (1) The bottom of the box is hoisted with the support ring. The box product is hoisted into the auxiliary support ring of the box processing, such as Figure 8 During the adjustment process, a lever is used to pry the contact area between the upper surface of the support ring and the spun bottom to achieve a small range of rotation of the spun bottom to ensure that the outer shape area of ​​the spun bottom is in contact with the groove area of ​​the support ring.

[0074] (2) Benchmark leveling: Use the lathe dial indicator to measure the benchmark line to level the bottom of the box.

[0075] (3) Support and fixation. Use 8 sets of support devices for fixation, such as Fig. 9 , Fig.10 Each group uses a 1-meter-high square box and a pair of jacks with adjustable stroke to support the lower end face of the clamping process side, and then uses the second jack with adjustable stroke, a pressure plate, an adjusting screw, and a nut to press down the upper end face of the process side to fix the bottom of the box, so as to achieve accurate and rapid clamping of the box bottom products.

[0076] The device used for the precise and rapid clamping of the turning internal shape includes several clamping components;

[0077] A plurality of supporting components are arranged around the auxiliary support ring along the circumference;

[0078] The supporting assembly includes a square box 2, a second pressing plate 6, a jack 1 3, a jack 2 4, and an adjusting screw 5;

[0079] The jack 1 3 and the jack 2 4 are arranged on the square box 2, and the jack 1 3 and the second pressing plate 6 support the workpiece, and the stroke of the jack 2 4 is adjustable; the vertical distance between the supporting platforms of the jack 1 3 and the jack 2 4 corresponds to the product;

[0080] One end of the second pressing plate 6 is connected to the top of the second jack 4. An adjustment hole is provided on the second pressing plate 6. The adjustment screw is arranged on the second pressing plate 6 through an adjustment nut. The second jack 4 can drive the second pressing plate 6 to move up and down.

[0081] S9 internal turning. Internal turning is performed according to the internal shape allowance and internal shape theoretical surface data coordinated with the product.

[0082] S10 is turned over again for clamping and alignment. The specific steps are as follows:

[0083] In step S10, the product is turned over again for clamping and alignment. The product is quickly clamped, including evenly distributing a plurality of inner support blocks arranged along the circumference on the lathe worktable, and the outer diameter of the inner support blocks corresponds to the inner diameter of the product;

[0084] According to the inner shape of the large end of the spinning bottom, the diameter after fine turning is strictly controlled to be within 0.1mm between the matching inner support block and the product, and the outer diameter of the inner support block is turned;

[0085] The inner support block is fixed on the lathe workbench by using a fixing screw and a fixing nut to press the spun bottom product downward, tightly fitting with the 16 inner support blocks, and controlling the matching clearance to be less than 0.1mm, so that the spun bottom product can automatically find the roundness.

[0086] The large end of the spun bottom shape is fixed by using tools such as pressure plates, nuts, screws, etc. to clamp the edge of the product to complete the clamping and fixing process.

[0087] S11 Turning shape. Remove the excess metal of the box shape in layers until it meets the design requirements.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation, characterized in that: The steps include: S1: Clamp the blank according to the spinning transfer reference line and perform rough alignment; S2: Perform meter testing on the blank to obtain measurement data; S3: reverse modeling the blank according to the measurement data obtained in step S2; S4: According to the theoretical model benchmark mapping coordination margin, the maximum margin of the blank envelope product is determined by adjusting the model position of step S4; S5: The clamping process edge is turned with a safety margin on the outer circle of the theoretical large end of the product, which is used to complete the precise and fast clamping process when turning the inner and outer shapes; S6: Perform a rough turning process of the product shape according to the maximum margin obtained in step S5; S7: Turn over and clamp for alignment, and use the clamping process edge and clamping tools to quickly clamp when finishing the inner shape; S8: Refine the inner shape according to the product coordination allowance and the inner shape theoretical surface data; S9: Turn over and clamp again for alignment, and quickly clamp when finishing the shape; S10: Process the product shape allowance in layers until it meets the design requirements.

2. According to claim 1, a method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation, characterized in that: In step S2, the ellipsoidal spun product is placed on the lathe table with the large end of the pressed bottom facing downward and the small end facing upward. The forming process baseline obtained in step S1 is used as a reference to use the lathe dial indicator to mark the base line, and the base line is leveled by adding a gasket to the lower end of the spun bottom. The machine tool dial indicator is used to measure the roundness of the spun bottom shape. The roundness is adjusted to the minimum by prying the product. The first pressing plate is used to press the large end of the bottom of the spun bottom to complete the clamping and alignment of the blank.

3. The method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation according to claim 1 is characterized in that: In step S3, a dial indicator is used to measure the specified measuring points of the blank shape in coordination with the rotation of the lathe, and the radius and height dimensions of the measuring points of the blank shape are measured; Find the maximum and minimum values ​​of the roundness of the blank alignment reference line by using a table, and set them as the measuring points of the spinning bottom blank outer surface; 16 busbars are evenly distributed around the circumference of the spun bottom, two of which involve the maximum and minimum values ​​of roundness. A measuring point is set on each busbar at an interval of 100 mm. There are 23 measuring points on each busbar, a total of 368 measuring points, and measurement data is obtained.

4. The method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation according to claim 3 is characterized in that: In step S3, the 368 points measured above are processed in reverse process; First, 16 generatrix spline curves are generated using the coordinates of the 23 measuring points of each generatrix. Secondly, 23 circumferential spline curves are generated using the coordinates of the 16 measuring points at the same latitude. The inner contour surface of the spun bottom is reversely generated using the generatrix curves and circumferential curves. The inner contour surface is offset outward with equal thickness to the minimum thickness of the actual blank to obtain the blank's limit inner surface. The generation of the inner and outer blank surfaces completes the reverse modeling of the blank.

5. The method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation according to claim 1 is characterized in that: The coordination margin in step S4 includes A1: Determine the rotation center of the blank, which is located at the large end face of the blank; A2: Adjust the rotation center of the theoretical model to coincide with the rotation center of the large end of the spinning bottom blank; A3; translate the theoretical model vertically up and down. During the translation process, the margins at each position of the spinning bottom theoretical model are constantly changing. Taking any cross-section as an example, when the margins of the inner and outer envelopes of the blank are the largest, this point is the optimal point. At this time, the best position of the product in the blank envelope is found.

6. The method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation according to claim 1, characterized in that: Step S5 designs a precise and rapid clamping scheme for turning the inner and outer shapes of the overall box bottom according to the optimal position of the parts after the allowance is coordinated, and the turning and clamping process edge is left with a safety margin on the outer circle of the large end of the theoretical product to achieve precise and rapid clamping of the inner and outer shapes.

7. The method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation according to claim 1, characterized in that: In step S6, the product shape rough turning process is performed according to the maximum allowance obtained in step S5. During rough turning, the residual stress in the part itself should be released to the maximum extent while leaving a safe shape allowance. The machining deformation caused by rough turning of the shape is turned off through the subsequent inner shape turning process. During shape fine turning, the cutting amount is turned in layers according to the allowance situation to reduce the wall thickness tolerance, thereby realizing machining deformation control. In addition, according to the maximum allowance obtained in step S4, the clamping process edge is turned while leaving a safe allowance for the outer circle of the large end of the product.

8. The method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation according to claim 1, characterized in that: Method for using the turning inner-shaped clamping structure in step S7: B1: Place the product's rotating bottom hanger in the box processing auxiliary support ring; B2: Use the lathe dial indicator to measure the reference line to level the bottom of the box; B3: Use the clamping assembly to clamp and fix the product, use several jacks with adjustable stroke to support the lower end of the clamping process edge, and then use additional jacks to press down and fix the upper end of the process edge, so as to achieve accurate and fast clamping of the product at the bottom of the box.

9. The method for thinning the overall bottom of a box by adjusting the allowance, aligning the clamping, and controlling the deformation according to claim 1, characterized in that: In step S9, the product is turned over again for clamping and alignment. The product is quickly clamped, including evenly distributing a number of inner support blocks arranged along the circumference on the lathe worktable, and the diameter after fine turning according to the inner shape of the large end of the spun bottom is strictly controlled to have a clearance between the inner support block and the product within 0.1mm, and the outer diameter of the inner support block is matched to make the outer diameter of the inner support block correspond to the inner diameter of the large end of the product; The inner support block is fixed on the lathe workbench by using a fixing screw and a fixing nut to press the spun bottom product downward, tightly fitting with the 16 inner support blocks, and controlling the matching clearance to be less than 0.1mm, so that the spun bottom product can automatically find the roundness.

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