A method for precise clamping and allowance coordination of 3.35m bottomless integral box bottom

Abstract

The application provides a 3.35m bottomless whole box bottom precision clamping and allowance coordination method, and the precision clamping method based on a general tool comprises the following steps: AS1, welding a pressing plate; AS2, aligning a reference; AS3, removing allowance; AS4, turning an auxiliary support ring; AS5, product and support ring cooperation; AS6, reference line leveling; AS7, flexible clamping; AS8, turning and spinning the bottom; AS9, arranging an inner support block; the allowance coordination method based on blank detection and reverse modeling technology comprises the following steps: BS1, forming reference transmission; BS2, alignment; BS3, blank detection. The application provides a precision clamping method and an accurate allowance coordination method, solves the product clamping problem and the allowance coordination problem, achieves the high technical index requirement of the product, and fills the blank in the field of 3.35m diameter whole spinning bottom part manufacturing.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of rocket box bottom processing, and particularly relates to a 3.35m bottom hole-free integral box bottom precision clamping and allowance coordination method. BACKGROUND

[0002] A new generation of medium-sized carrier rocket storage tank box bottom adopts an integral spinning bottom structure, has a diameter of about 3.35m, is free of a central hole, has a height of about 1.1m, and has an ellipsoidal surface structure. The part is manufactured by using an integral forming manufacturing scheme. The blank after integral forming has a certain allowance in the inner and outer and height directions, needs to be cut and removed by mechanical processing, and finally the shape and position precision control of the product is completed.

[0003] Due to the complex product structure, extremely poor structural rigidity, high dimensional precision requirement, and extremely small allowance of the blank envelope product, there is great technical difficulty in processing.

[0004] The part has the following processing difficulties: 1) clamping difficulty, the part is an ellipsoidal surface without a clamping point; 2) due to the influence of factors such as the thickness reduction in the spinning forming process and the precision control after forming, the allowance of the blank envelope product is often very tight; there is no processing case of the same type and size of integral part in the field of Chinese aerospace manufacturing. SUMMARY

[0005] Therefore, the application aims to provide a 3.35m bottom hole-free integral box bottom precision clamping and allowance coordination method, a precision clamping method and an accurate allowance coordination method, solve the product clamping problem and the allowance coordination problem, meet the high technical index requirement of the product, and make up for the blank in the field of 3.35m diameter integral spinning bottom part manufacturing.

[0006] To achieve the above purpose, the technical scheme of the application is as follows:

[0007] A 3.35m bottom hole-free integral box bottom precision clamping and allowance coordination method based on a general tool precision clamping method includes the following steps:

[0008] AS1, welding pressure plate; welding pressure plates are uniformly distributed in the circumferential direction of the spinning bottom outer surface large end allowance area;

[0009] AS2, find the reference; hoist the ellipsoidal spinning bottom large end to be placed on the lathe bed in the state of the small end up; measure the forming reference line by using the lathe dial gauge, adjust the reference line to be flat by increasing the gasket at the lower end of the spinning bottom product; adjust the roundness to be minimum by using the lever to pry the product by using the lathe dial gauge to measure the spinning bottom roundness;

[0010] AS3, remove the excess; after the bottom of the spinning alignment, turning processing self-centering ring belt, remove the excess, so that the ring belt area of the rough light;

[0011] AS4, turning auxiliary support ring; after the auxiliary support ring is clamped and aligned on the lathe bed, the groove is turned, and the groove diameter needs to be consistent with the size of the small end ring belt of the spinning bottom;

[0012] AS5, product and support ring cooperation; the spinning bottom product is hung on the auxiliary support ring, and during the adjustment process, the upper surface of the support ring is pried with a lever to contact the area of the spinning bottom, which realizes the small range rotation of the spinning bottom, ensures the contact between the small end light ring belt area of the spinning bottom and the auxiliary support ring groove area, and realizes the fast and accurate alignment of the spinning bottom product by using the self-centering principle of the ring area cooperation;

[0013] AS6, reference line leveling; on the lathe bed, use the lathe dial gauge to measure the forming reference line, pry the upper surface of the support ring with a lever to contact the area of the spinning bottom, realize the small range rotation of the spinning bottom, and adjust the forming reference line;

[0014] AS7, flexible clamping; 8 groups of flexible support devices are used to fit the part support station cross section with 8 support points; the flexible support device is completely attached to the lower end surface of the 8 process pressure plates to achieve the purpose of flexible support;

[0015] AS8, turning spinning bottom; turning the inner shape of the spinning bottom product, and turning the ring groove in the outer shape excess area;

[0016] AS9, matching the inner support block; 16 inner support blocks are evenly fixed on the lathe bed, the spinning bottom product is pressed down tightly, and the gap between the spinning bottom product and the 16 inner support blocks is controlled to be less than 0.1mm, so that the spinning bottom product can be automatically aligned; the large end of the spinning bottom is clamped and pressed tightly by 16 pressure plates, screws and nuts, and the pressing position is the ring groove of S8 turning, so as to realize the precise clamping of the spinning bottom turning outer shape;

[0017] The pressing mechanism used is a conventional part, which echoes the theme based on general tools;

[0018] The excess coordination method based on roughness detection and reverse modeling technology includes the following steps:

[0019] BS1, forming reference line transmission; a continuous line is engraved on the large end of the roughness to transmit the reference line of the forming process

[0020] BS2, alignment; according to the steps of AS1-AS7, the clamping and alignment before turning the inner shape of the spinning bottom are completed;

[0021] BS3, roughness detection; use the dial gauge to measure the specified points of the inner shape of the roughness, measure the radius size and height size of the inner shape of the roughness, and cooperate with the lathe rotation.

[0022] BS31, set the inner surface of the spinning bottom blank, 16 bus lines are evenly distributed in the circumferential direction of the spinning bottom, and one measuring point is arranged on each bus line at intervals of 100 mm, 22 measuring points are arranged on each bus line, and a total of 352 measuring points are arranged, the horizontal axis is the X radius value of the corresponding measuring point of each bus line, and the vertical axis is the Z height value; the inner surface coordinate point set Q of the blank is obtained a , denoted as {X (u.v) , Z (u)}, wherein u=1, 2,..., 22, and v=1, 2,..., 16.

[0023] BS32, the measuring points in BS31 are processed by a computer in a reverse process, and the blank measurement is completed. First, the maximum and minimum values of the X coordinates of the 16 measuring points on the same latitude are obtained from the dot measurement table, and the inner surface envelope point set Q of the spinning bottom is obtained min , Q max , denoted as {X min(u) , Z (u)}, {X max(u) , Z (u)}, wherein u=1, 2,..., 22; the inner surface envelope point set is used to process the inner surface envelope point set by a computer, and the inner surface envelope contour surface of the spinning bottom is generated in a reverse manner, as shown in the figure;

[0024] The inner contour surface is outwardly and uniformly offset by the thickness of the actual blank to obtain the outer contour surface of the blank. The generation of the inner and outer blank contour surfaces completes the measurement of the blank. The area between the maximum envelope of the inner shape and the minimum envelope of the outer shape is the area that can be used for product processing.

[0025] BS33, the relative optimal position of the blank and the theoretical model is obtained, and the spinning bottom forming allowance is maximized.

[0026] Firstly, the rotation center of the blank is determined, and the rotation center is located at the large end face of the blank;

[0027] Secondly, the rotation center of the theoretical model is adjusted to coincide with the rotation center of the large end of the spinning bottom blank;

[0028] Then, the theoretical model is translated up and down along the vertical direction. In the process of translation, the allowance of each position of the spinning bottom theoretical model is constantly changing. Taking an arbitrary cross section as an example, when the inner and outer envelope allowances of the blank are maximum, the point is the optimal point, and the best position of the product in the blank envelope is found;

[0029] Further, in AS1, 8 pressing plates are arranged in the allowance area in the circumferential direction; the pressing plates are welded to the spinning bottom by means of angle welding and four-axis full welding.

[0030] Furthermore, the diameter of the ring area ranges from Φ1000 to Φ1130, and the width is approximately 155-165 mm; the allowance to be removed is 3-5 mm.

[0031] Furthermore, the flexible support device includes a square box, a first jack, a second jack, and a compaction plate; the compaction plate is installed to the top of the square box by bolts, and the connection point between the bolts and the compaction plate is in the middle of the compaction plate; the first jack and the second jack are also installed to the top of the square box, the first jack acts on the first end of the compaction plate, and the pressure plate with the bottom welded by spinning is set between the second jack and the second end of the compaction plate.

[0032] Furthermore, the No. 1 jack is a jack with independently adjustable Z-axis stroke.

[0033] Furthermore, the clearance between the spun bottom and the inner support block is <0.1mm.

[0034] Compared with existing technologies, the precision clamping and allowance coordination method for a 3.35m bottomless integral box bottom described in this invention has the following advantages:

[0035] This invention addresses the challenges of clamping and margin coordination in the machining process of a 3.35m diameter integral spun base part. It designs a precision clamping and alignment method based on general-purpose tools and a margin coordination method based on reverse modeling technology. Based on the above invention, precision clamping and maximum utilization of margin can be achieved for 3.35m diameter integral spun base parts, filling a gap in the field of 3.35m diameter integral spun base part manufacturing. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 This is a schematic diagram of the circumferential mounting pressure plate of the spun bottom as described in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the auxiliary support ring according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the spinning bottom placed on the auxiliary support ring according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the flexible support device described in an embodiment of the present invention acting on the spinning bottom;

[0041] Figure 5 This is an enlarged schematic diagram of the flexible support device described in an embodiment of the present invention;

[0042] Figure 6 The ring groove pressing schematic diagram for the embodiment of the present application;

[0043] Figure 7 The spinning bottom rough blank busbar and measuring point schematic diagram for the embodiment of the present application;

[0044] Figure 8 The theoretical model schematic diagram for the embodiment of the present application;

[0045] Figure 9 The spinning bottom inner shape envelope profile schematic diagram for the embodiment of the present application;

[0046] Figure 10 The area schematic diagram for the embodiment of the present application which can be used for product processing.

[0047] Explanation of reference signs:

[0048] 1, spinning bottom; 11, ring belt; 2, pressing plate; 3, auxiliary support ring; 4, flexible support device; 41, square box; 42, No. 1 jack; 43, No. 2 jack; 44, compaction plate; 5, inner support block. DETAILED DESCRIPTION

[0049] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0050] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features limited by "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0051] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0052] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0053] A 3.35m bottomless whole box bottom precision clamping and excess coordination method, based on the precision clamping method of general tool, comprises the following steps:

[0054] AS1, welding pressure plate 2; as shown in the figure, welding pressure plate 2 is evenly distributed in the circumferential direction of the large end excess area of the spinning bottom 1 contour surface; Figure 1

[0055] AS2, alignment reference; hoist the ellipsoid spinning bottom 1 in the state of large end down and small end up and place it on the lathe bed; measure the forming reference line by using the lathe dial gauge, adjust the reference line by increasing the gasket at the lower end of the spinning bottom 1 product; adjust the roundness to the minimum by using the lever to pry the product, using the lathe dial gauge to measure the contour roundness of the spinning bottom 1;

[0056] AS3, remove excess; after the spinning bottom 1 is aligned, the self-centering clamping alignment ring 11 is processed by turning, and the excess is removed, so that the ring 11 area is visible;

[0057] AS4, turning auxiliary support ring 3; as shown in the figure, after the auxiliary support ring 3 is clamped and aligned on the lathe bed, the groove is turned, and the groove diameter needs to be consistent with the size of the small end ring 11 of the spinning bottom 1; the inner diameter of the auxiliary support ring 3 is Φ1065, which is convenient for subsequent cooperation. Figure 2

[0058] AS5, product and support ring cooperation; as shown in the figure, the spinning bottom 1 product is hoisted and placed on the auxiliary support ring 3, and during the adjustment process, the lever is used to pry the contact area between the upper surface of the support ring and the spinning bottom 1, to realize the small range rotation of the spinning bottom 1, to ensure that the small end visible ring 11 area of the spinning bottom 1 is in contact with the groove area of the auxiliary support ring 3, and to realize the fast and accurate roundness of the spinning bottom 1 product by using the self-centering principle of the ring area cooperation; when turning the inner shape of the spinning bottom 1, the existence of the auxiliary support ring 3 makes the turning more stable. Figure 3

[0059] ​​​AS6, Baseline Leveling: On the lathe table, use a dial indicator to measure the forming baseline, and use a lever to pry the upper surface of the support ring in contact with the spinning base 1 to achieve a small range of rotation of the spinning base 1 and level the forming baseline.

[0060] AS7, flexible clamping; such as Figure 4 Figure 5 As shown, eight sets of flexible support devices 4, with a total of eight support points, are used to fit the cross section of the part support station; so that the flexible support devices 4 are completely in contact with the lower end face of the eight process pressure plates 2 to achieve the purpose of flexible support.

[0061] AS8, Turning the spinning base 1; Turning the inner shape of the spinning base 1 product, and turning the annular groove in the outer allowance area;

[0062] AS9, equipped with vehicle interior support block 5; such as Figure 6 As shown, 16 inner support blocks 5 are evenly distributed and fixed on the lathe worktable. The spinning base 1 product is pressed down and tightly fitted with the 16 inner support blocks 5. The fit clearance is controlled to be <0.1mm, so that the spinning base 1 product can automatically find its roundness. The large end of the spinning base 1 is clamped and pressed by a combination of 16 pressure plates 2, screws and nuts. The clamping position is the annular groove machined by S8, so as to achieve precision clamping of the machined shape of the spinning base 1.

[0063] The clamping mechanism used is a standard part, echoing the theme of being based on general-purpose tools;

[0064] The margin coordination method based on blank inspection and reverse modeling technology includes the following steps:

[0065] BS1, Forming reference transfer; A continuous engraving line is made at the large end of the blank by the forming process to transfer the reference of the forming process.

[0066] BS2, Alignment; Follow steps AS1 to AS7 to complete the clamping and alignment before turning the inner shape of the spinning base 1;

[0067] BS3, Blank Inspection: Using a dial indicator and lathe rotation, measure the specified measuring points of the blank's internal shape, including the radius and height of the measuring points.

[0068] BS31, Set the measuring points on the inner surface of the spinning bottom blank; such as Figure 7 As shown, 16 generatrices are evenly distributed around the circumference of the spinning base, with 22 measuring points on each generatrice, totaling 352 measuring points, as shown in the table below. The horizontal axis represents the X-radius value of each measuring point on each generatrice, and the vertical axis represents the Z-axis height value. The coordinate point set Qa of the inner surface of the blank is obtained, denoted as {X... (u.v) Z (u)}, where u = 1, 2, ... 22, v = 1, 2, ... 16.

[0069]

[0070] BS32, the BS31 in the measuring point by computer reverse process, complete the blank measurement. First from the dot measurement table to obtain the same latitude on the 16 measuring point X coordinate maximum and minimum value, get spinning bottom 1 inner surface envelope point set Q min 、Q max , recorded as {X min(u) , Z (u)}、{X max(u) , Z (u)}, wherein u = 1, 2,... 22; using the inner surface envelope point set, by computer to the inner surface envelope point set reverse processing, reverse generation spinning bottom 1 inner shape envelope contour surface, as Figure 9 Indicated;

[0071] The inner contour surface is outwardly offset by the actual blank thickness to obtain the blank outer shape contour surface, the generation of the inner and outer blank contour surface completes the measurement of the blank, wherein the area between the inner maximum envelope and the outer minimum envelope is the area available for product processing, as shown in Figure 10 Indicated.

[0072] BS33, obtain the relative optimal position of the blank and the theoretical model, and maximize the spinning bottom 1 forming allowance.

[0073] First, determine the center of rotation of the blank, the center of rotation is located in the large end face of the blank;

[0074] Second, adjust the center of rotation of the theoretical model to coincide with the center of rotation of the large end of the spinning bottom 1 blank;

[0075] Then, the theoretical model is translated up and down along the vertical direction, and in the process of translation, the allowance of each position of the spinning bottom 1 theoretical model is constantly changing. Taking an arbitrary cross section as an example, when the inner and outer envelope allowance of the blank is maximum, the point is the optimal point, at this time the best position of the product in the blank envelope is found; as shown in Figure 8 Indicated.

[0076] Preferably, in AS1, 8 pressing plates 2 are arranged circumferentially in the allowance area; the pressing plates 2 are welded to the spinning bottom 1 by fillet welding of the four shafts and full welding; the size of the process pressing plate 2 is 100mm×100mm×20mm; the size of the pressing plate 2 can meet the clamping size requirement and reduce the welding workload.

[0077] Preferably, the diameter range of the ring belt 11 area is Φ1000-Φ1130, and the width is about 160mm; the ring belt 11 area blank is exposed to light, and the allowance removal size is 4mm.

[0078] Preferably, the flexible support device 4 comprises a square box 41, a first jack 42, a second jack 43 and a compaction plate 44; the compaction plate 44 is bolted to the top of the square box 41, and the connecting point of the bolt and the compaction plate 44 is in the middle of the compaction plate 44; the first jack 42 and the second jack 43 are also mounted to the top of the square box 41, and the first jack 42 acts on the first end of the compaction plate 44, and the pressing plate 2 welded to the spinning bottom 1 is arranged between the second end of the compaction plate 44 and the second jack 43.

[0079] Preferably, the first jack 42 is a Z-direction stroke independently adjustable jack, and by adjusting the vertical spatial position of the first jack 42, the flexible support device 4 is completely matched with the lower end surface of the process pressing plate 2 at each position 8, so as to achieve the purpose of flexible support; in order to limit the upward freedom of the part, the compaction plate 44 is used in cooperation with the second jack 43 to press the part from above; during the application of pressure, the clamping force is transmitted to the support point along the normal direction of the contact point (or surface) as much as possible, and a micrometer gauge is used to be on the lower side of the process pressing plate 2 to monitor the deformation amount during the pressing process of the part; considering the accuracy requirement of the part in the free state, the deformation amount is controlled to be within 0.2mm, so as to reduce the accuracy loss caused by the rebound deformation after the conventional clamping, loosening and unloading, and once the range is exceeded, the part should be loosened again, and then pressed again until the micro-deformation index is met.

[0080] Preferably, the gap between the spinning bottom 1 and the inner support block 5 is less than 0.1mm; the outer diameter of the inner support block 5 is Φ3336.6, and the fixing mode of the inner support block 5 is that a Φ24 process hole is used, and a screw rod and a nut are used to be tightened and fixed.

[0081] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for precision clamping and allowance coordination of a 3.35m bottomless integral box bottom, characterized in that: The precision clamping method based on general-purpose tools includes the following steps: AS1, Welded pressure plate; Welded pressure plates are evenly distributed circumferentially in the large end allowance area of ​​the spun bottom surface; AS2, Alignment of the reference; The elliptical spun bottom is placed on the lathe table with the large end at the bottom and the small end at the top; The forming reference line is measured using a dial indicator on the lathe, and the reference line is leveled by adding shims to the lower end of the spun bottom product; The roundness of the spun bottom is measured using a dial indicator on the machine tool, and the roundness is adjusted to the minimum by using a lever to pry the product. AS3, Remove excess material; After spinning and aligning the bottom, machine the self-centering clamping alignment ring belt by turning, remove excess material, and expose the blank in the ring belt area to light; AS4, Turning auxiliary support ring; After the auxiliary support ring is clamped and aligned on the lathe table, turn the bevel. The bevel diameter must be consistent with the size of the small end ring of the spinning bottom. AS5. Product and support ring fit: The spun bottom product is suspended on the auxiliary support ring. During the adjustment process, the upper surface of the support ring is pried and the contact area between the spun bottom is moved by levers to achieve a small range of rotation of the spun bottom. This ensures that the visible ring area at the small end of the spun bottom contacts the bevel area of ​​the auxiliary support ring. By utilizing the self-centering principle of the ring area fit, the spun bottom product can be quickly and accurately rounded. AS6, Baseline Leveling: On the lathe table, use a dial indicator to measure the forming baseline, and use a lever to pry the upper surface of the support ring in contact with the spinning bottom to achieve a small range of rotation of the spinning bottom and level the forming baseline. AS7, Flexible clamping; Eight sets of flexible support devices are used, with a total of eight support points to fit the cross section of the part support station; the flexible support devices are completely fitted with the lower end face of the eight process pressure plates to achieve the purpose of flexible support. AS8, Turning the spinning bottom; Turning the inner shape of the spinning bottom product and turning the annular groove in the outer allowance area; AS9, equipped with internal support blocks; 16 internal support blocks are evenly distributed and fixed on the lathe worktable. The spun bottom product is pressed downwards and tightly fitted with the 16 internal support blocks. The large end of the spun bottom is clamped and pressed using a combination of 16 pressure plates, screws, and nuts. The clamping position is the annular groove machined by AS8, achieving precise clamping of the machined shape of the spun bottom. The margin coordination method based on blank inspection and reverse modeling technology includes the following steps: BS1, Forming reference transfer; A continuous engraving line is made at the large end of the blank by the forming process to transfer the reference of the forming process. BS2, Alignment; Follow steps AS1~AS7 to complete the clamping and alignment before turning the inner shape of the spinning bottom; BS3, Blank Inspection: Using a dial indicator and lathe rotation, measure the specified measuring points of the blank's internal shape, including the radius and height of the measuring points. BS31, Set the measuring points on the inner surface of the spun bottom blank; BS32. Perform reverse processing on the measuring points in BS31 to complete the blank measurement; BS33. Obtain the relative optimal position between the blank and the theoretical model, and retain the forming allowance of the spinning bottom to the maximum extent.

2. The method for precision clamping and allowance coordination of a 3.35m bottomless integral box bottom according to claim 1, characterized in that: In AS1, eight pressure plates are arranged circumferentially in the margin area; the pressure plates are welded to the spinning base by fillet welding and full welding.

3. The method for precision clamping and allowance coordination of a 3.35m bottomless integral box bottom according to claim 1, characterized in that: The diameter of the ring area ranges from Φ1000mm to Φ1130mm, and the width is 155-165mm; the allowance to be removed is 3-5mm.

4. The method for precision clamping and allowance coordination of a 3.35m bottomless integral box bottom according to claim 1, characterized in that: The flexible support device includes a square box, a first jack, a second jack, and a compaction plate. The compaction plate is bolted to the top of the square box, and the connection point between the bolt and the compaction plate is in the middle of the compaction plate. The first jack and the second jack are also installed on the top of the square box. The first jack acts on the first end of the compaction plate, and the pressure plate with the bottom welded by the spin forming is set between the second jack and the second end of the compaction plate.

5. The method for precision clamping and allowance coordination of a 3.35m bottomless integral box bottom according to claim 4, characterized in that: The No. 1 jack is a jack with independently adjustable Z-axis stroke.

6. The method for precision clamping and allowance coordination of a 3.35m bottomless integral box bottom according to claim 1, characterized in that: The clearance between the spun bottom and the inner support block is less than 0.1mm, enabling the spun bottom product to automatically find its roundness.

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