High-precision large-size thin-walled part machining method
By using the inner hole of the process step in the large-size thin-walled parts as the clamping and positioning reference, and using the axial pressure cover tool for axial clamping, the deformation and accuracy problems in the machining of thin-walled parts are solved, and efficient and economical high-precision machining is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHAANXI WEIHE TOOLS CO LTD
- Filing Date
- 2022-04-13
- Publication Date
- 2026-06-12
AI Technical Summary
Large-sized thin-walled parts are prone to defects such as chatter and tool deflection during machining, and existing machining methods are difficult to meet high precision requirements, especially the deformation problem of the inner hole datum.
The inner hole of the rough-machined blank is used as a clamping and positioning reference for subsequent machining. An axial pressure cover is used to clamp the part axially to avoid radial stress and ensure machining accuracy.
It enables precise machining of large-sized thin-walled parts with high precision, meeting the form and position tolerances and dimensional tolerances required by the design, avoiding defects such as internal hole deformation and vibration marks, and reducing production costs.
Smart Images
Figure CN116944802B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of clamping and machining methods and tooling technology for work transport machine tools, and specifically relates to a high-precision machining method for large-size thin-walled parts. Background Technology
[0002] In daily production, we often encounter the turning of large, thin-walled parts, such as... Figure 1 As shown: Inner hole 254H6 300h7, 4±0.025, M250×1.5-6H internal thread, coaxiality deviation between thread and reference hole ≤ The following dimensions require high machining accuracy: parallelism between the two end faces of the workpiece ≤ 0.02, and perpendicularity between the inner hole and the lower end face ≤ 0.015.
[0003] Generally, for large, thin-walled parts like those mentioned above, two machining methods are typically used: 1) Clamping the lower outer diameter and turning the upper outer diameter and inner hole; however, due to the thin hole wall, machining defects such as chatter and tool deflection are easily generated during the machining process. 2) After clamping the large upper outer diameter with allowance, finish turning each inner hole and outer diameter; the previously machined reference inner hole will generate stress as the hole wall thins during machining, resulting in deformation of the final reference inner hole. Obviously, both machining methods have certain defects and cannot meet the final design requirements of the drawings. Therefore, when machining large, thin-walled parts, the most taboo method is the use of chuck-type clamping, that is, it is taboo to subject the workpiece to radial force, which will cause three-point elliptical deformation of the workpiece's inner hole, affecting the machining of the reference hole and the realization of subsequent finishing processes. In response, the following technical solution is proposed. Summary of the Invention
[0004] The technical problem solved by this invention is to provide a high-precision, large-size, thin-walled part machining method that utilizes the rough machining blank allowance of the part itself to machine the inner hole of the process step, and uses the inner hole of the process step as the clamping and positioning reference for subsequent machining, without the need to add additional process heads and other clamping production costs; thus solving the technical problems of easy deformation and high production cost in machining high-precision, large-size, thin-walled parts.
[0005] The technical solution adopted in this invention is a high-precision large-size thin-walled part processing method. It uses the rough machining blank allowance of the part itself to finely machine the process step inner hole extending from the shaft end face inward. The process step inner hole is used as the positioning reference for subsequent processing and clamping. The part is axially clamped and processed using an axial pressure cover tool to obtain the shaped thin-walled part with the required precision.
[0006] The method for machining large-size thin-walled parts according to the claim includes the following steps:
[0007] S1. Process Step Inner Hole: Using the rough machining allowance of the part itself, the process step inner hole extending inward from the shaft end face is precision machined.
[0008] S2. Precision machining of one end: Using the inner hole of the process step as a reference, use axial pressure cover tool I to concentrically and axially press the inner hole of the process step to machine the high-precision process dimensions and structure required for the other end of the part.
[0009] S3. Precision machining of the outer contour: Using the inner hole of the process step and the outer contour of the part end machined in step S2 as a reference, use the axial pressure cover tool II to concentrically and axially press the part to machine the high-precision process dimensions and structure required for the outer contour of the part.
[0010] S4. Precision machining of the other end: Based on the high-precision process dimensions required for the other end of the part processed in step S2, use axial pressure cover tool III to concentrically and axially press the part, and process the high-precision process dimensions required for the part at the end where the inner hole of the process step is located.
[0011] In the above technical solution, the axial pressure cover fixture I, axial pressure cover fixture II, and axial pressure cover fixture III are respectively composed of a pressure cover, a pressure plate, and screws.
[0012] In the above technical solution, further: the pressure plate of the axial pressure plate fixture I is a thick-walled cylindrical structure, and the pressure plate has a central positioning countersunk hole concentrically formed in the center; the central positioning countersunk hole is concentrically matched with the outer contour of the inner hole of the process step of the part; the pressure plate of the axial pressure plate fixture I axially presses the outer shaft end face of the inner hole of the process step of the part; the pressure plate has a central through hole; the screw of the axial pressure plate fixture I passes through the central through hole of the pressure plate and is concentrically screwed to fit the central internal thread hole of the pressure plate to axially press and fix the part.
[0013] In the above technical solution, further: the pressure plate of the axial pressure plate tool II is a thick-walled cylindrical structure, and the pressure plate has a central positioning countersunk hole concentrically formed in the center; the central positioning countersunk hole is concentrically matched with the outer contour of the end of the part as processed in step S2; the pressure plate of the axial pressure plate tool II axially presses the outer shaft end face of the inner hole of the process step of the part; the pressure plate has a central through hole; the screw of the axial pressure plate tool II passes through the central through hole of the pressure plate and is screwed into the central threaded hole of the pressure plate to axially press and fix the part.
[0014] In the above technical solution, further: the pressure plate of the axial pressure plate tooling Ⅲ is a thick-walled cylindrical structure, and a central positioning countersunk hole is concentrically formed in the center of the pressure plate; the central positioning countersunk hole is concentrically adapted to the outer contour of the end of the part as processed in step S2; an axial set screw hole is formed on one side of the central positioning countersunk hole of the pressure plate; the center line of the axial set screw hole is parallel to the center line of the pressure plate; the pressure plate of the axial pressure plate tooling Ⅲ is an L-shaped structure, and the horizontal plate of the pressure plate has an axial through hole; the screw of the axial pressure plate tooling Ⅲ passes through the axial through hole of the pressure plate and then screws into the axial set screw hole of the pressure plate to axially press and fix the part.
[0015] Advantages of this invention compared to existing technologies:
[0016] 1. This invention can accurately machine the design datum of thin-walled large-size parts; it does not use a three-jaw chuck to hold the parts, but uses an axial pressure cover tool to make the workpiece axially stressed; it ensures that all other relevant dimensions in the drawing meet the design requirements of the drawing; it guarantees the form and position tolerances and dimensional tolerances in the drawing; and through the conversion of the datum, it ensures that the coaxiality deviation of the internal thread and the internal hole in subsequent machining can meet the drawing requirements.
[0017] 2. The inner hole of the process step in this invention can act as a reinforcing rib; while ensuring the size of the inner hole of the process step, the setting of the inner hole of the process step effectively increases the inner hole wall thickness and the contact area, thus acting as a reinforcing rib; avoiding the existence of adverse factors such as inner hole turning vibration, tool deflection, and untimely heat dissipation that affect the surface roughness of the inner hole, as well as the taper and cylindricity of the inner hole; ensuring the production of qualified products that meet the design requirements.
[0018] 3. This invention utilizes the tooling designed based on the original drawings, cleverly taking advantage of the blank allowance of the rough-machined parts to machine the inner hole of the process step, providing a clamping reference for subsequent finishing, without increasing manufacturing costs, making it economical, practical, efficient and reliable. Attached Figure Description
[0019] Figure 1 This is a process requirement diagram for the high-precision, large-size, thin-walled parts to be processed according to this invention;
[0020] Figure 2 This is a schematic diagram of the inner hole structure of the part's process step in step S1 of the present invention;
[0021] Figure 3 This is a schematic diagram of the structure of the axial pressure cap tooling I for clamping parts in step S2 of the present invention;
[0022] Figure 4 This is a schematic diagram of the structure of the axial pressure cap tool II for clamping parts in step S3 of the present invention;
[0023] Figure 5 This is a schematic diagram of the structure of the axial pressure cap tooling Ⅲ for clamping parts in step S4 of the present invention;
[0024] Figure 6 This is a process flow diagram of the method of the present invention;
[0025] In the figure: 1-part, 2-process step inner hole, 3-axial pressure cover fixture; 3-1 axial pressure cover fixture I, 3-2 axial pressure cover fixture II, 3-3 axial pressure cover fixture III; 301-pressure cover, 302-pressure plate, 303-screw. Detailed Implementation
[0026] The following will refer to the appendices in the embodiments of the present invention. Figure 1-6 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0027] The high-precision, large-size, thin-walled parts referred to in this invention, such as... Figure 1 As shown, the inner hole 254H6 300h7, 4±0.025, M250×1.5-6H internal thread, coaxiality deviation between thread and reference hole ≤ 0.025, parallelism of both end faces of the workpiece ≤0.02, perpendicularity of the inner hole to the lower end face ≤0.015, these are all important dimensions that need to be ensured in terms of machining accuracy.
[0028] The present invention proposes a high-precision machining method for large-size thin-walled parts. The main improvement lies in: using the rough machining allowance of the part 1 itself to finish machining the process step inner hole 2 extending inward from the shaft end face (e.g., ...). Figure 2 As shown), and using the inner hole 2 of the process step as the positioning reference for subsequent machining clamping, the part is axially clamped and machined using the axial pressure cap fixture 3 (as shown). Figure 3 , Figure 4 , Figure 5 As shown in the figure, to obtain the molded thin-walled parts with the required precision.
[0029] For high-precision, large-sized, thin-walled parts, a machining method is considered in production that utilizes the roughing allowance of the part 1 itself to finish the stepped inner hole 2. That is, during machining, a pre-machined blank is prepared as shown in the diagram. Figure 2 shown The inner hole 2 of the process step is 230×15. This inner hole 2 of the process step is used as the clamping and positioning reference for subsequent machining to complete the subsequent clamping and machining.
[0030] In the above embodiments, the following steps are further included:
[0031] (like Figure 6 (As shown) Step S1, Machining the inner hole of the process step: Using the rough machining allowance of the blank of part 1 itself, finish machining the inner hole 2 of the process step that extends from the shaft end face inward.
[0032] The inner hole 2 of the process step is used to provide a clamping reference and also serves as a reinforcing rib.
[0033] Step S2, precision machining of one end: Using the inner hole 2 of the process step as a reference, use the axial pressure cover tool I3-1 to concentrically and axially press the inner hole 2 of the process step to machine the high-precision process dimensions and structure required for the other end of part 1.
[0034] In the above embodiments, the axial pressure cap tooling Ⅰ3-1 is further composed of a pressure cap 301, a pressure plate 302, and screws 303.
[0035] As can be seen, the axial pressure cap fixture Ⅰ3-1 consists of three parts, and it is axially clamped. The fixture has a simple structure, a small number of components, accurate clamping and positioning, stable clamping, and is economical and practical.
[0036] (like Figure 3 As shown in the above embodiment, further: the pressure cap 301 of the axial pressure cap tooling Ⅰ3-1 is a thick-walled cylindrical structure, and a central positioning countersunk hole is concentrically formed in the center of the pressure cap 301. The central positioning countersunk hole is concentrically adapted to the outer contour of the inner hole 2 of the process step of part 1. During processing, the pressure cap 301 is clamped and positioned on the equipment with the aid of a three-jaw chuck, thereby realizing the clamping and positioning of the part.
[0037] The pressure plate 302 of the axial pressure cover fixture I3-1 axially presses the outer shaft end face of the inner hole 2 of the process step of the part; the pressure plate 302 has a central through hole; the screw 303 of the axial pressure cover fixture I3-1 passes through the central through hole of the pressure plate 302 and is concentrically screwed into the central internal thread hole of the pressure cover 301 to axially press and fix the part 1.
[0038] For example, in step S2: First, the clamping and positioning references are machined, i.e., the clamping... 304 stainless steel outer diameter, machined to a smooth finish on the top surface, precision machined. and The inner end face is 230mm, ensuring the parallelism between the inner and outer end faces is ≤0.015. The machined outer circle and end face are used as the positioning datum. The following dimensions are precision machined using the gland tooling Ⅰ3-1: 254H6 inner hole, 262 outer diameter, dimension 4±0.025 and The main dimensions of 300h7 and R3 are as follows. It can be observed that in the finishing step S2, the inner hole, end face, and outer diameter can be machined simultaneously, ensuring both the dimensional tolerances and the perpendicularity of the inner hole to the lower end face (≤0.015). During this machining process, a pressure plate 302 and a center screw 303 are used to fix part 1 to the pressure cover 301 fixture. In this step, the outer cylindrical end face of the inner hole 2 of the process step is used as the positioning datum, providing axial clamping and positioning for the machining of the main dimensions. Because an axial clamping installation method is used in this step, it effectively avoids adverse factors such as vibration marks, tool deflection, and workpiece deformation that occur when machining the inner hole of thin-walled parts.
[0039] (like Figure 4 (As shown) Step S3, precision machining of the outer contour: Using the inner hole 2 of the process step and the outer contour of the part end machined in step S2 as the reference, use the axial pressure cover tool II3-2 to concentrically press the part 1 in the axial direction to machine the high-precision process dimensions and structure required for the outer contour of the part 1.
[0040] In the above embodiments, the axial pressure cap tooling II 3-2 is further composed of a pressure cap 301, a pressure plate 302, and screws 303.
[0041] Similarly, the axial pressure cap fixture II3-2 consists of three parts and is axially clamped. The fixture has a simple structure, a small number of components, precise clamping and positioning, stable clamping, and is economical and practical.
[0042] In the above embodiments, further: the pressure cap 301 of the axial pressure cap tooling II 3-2 is a thick-walled cylindrical structure, and the pressure cap 301 has a central positioning countersunk hole concentrically formed in the center; the central positioning countersunk hole is concentrically adapted to the outer contour of the end of the part 1 processed in step S2.
[0043] During processing, the pressure cap 301 is clamped and positioned on the equipment using a three-jaw chuck, thus achieving the clamping and positioning of part 1.
[0044] The pressure plate 302 of the axial pressure cover fixture II 3-2 axially presses the outer shaft end face of the inner hole 2 of the process step of the part; the pressure plate 302 has a central through hole; the screw 303 of the axial pressure cover fixture II 3-2 passes through the central through hole of the pressure plate 302 and is screwed into the central internal thread hole of the pressure cover 301 to axially press and fix the part 1.
[0045] It can be seen that: Using the outer diameter and lower end face of 300h7 as a reference, the axial pressure cover tool II3-2 is used. The upper end face is fixed and pressed with the pressure plate 302 and screws 303. The outer diameter is then machined in sequence. 252. 262, 10, 25, and R5 are used to complete the finishing of the entire part's outer contour dimensions. In this step, the axial clamping and positioning clamping method is also used. The outer cylindrical end face of the outer contour of part 1 is used as the positioning reference, and the outer dimensions and the inner and outer chamfers of each end face are machined in sequence. Due to the presence of the inner hole 2 of the process step, the press-fit contact area is increased, which is equivalent to the effect of a reinforcing rib, making the clamping of part 1 more reliable and effectively avoiding the vibration marks and workpiece deformation caused by repeated turning friction between the cutting tool and the workpiece.
[0046] (like Figure 5(As shown) Step S4, precision machining of the other end: Based on the high-precision process dimensions and structure required for the other end of part 1 processed in step S2, use the axial pressure cover tool III3-3 to concentrically and axially press part 1, and process the high-precision process dimensions and structure required for the part at the end where the inner hole 2 of the process step is located.
[0047] In the above embodiments, the axial pressure cap tooling Ⅲ3-3 is further composed of a pressure cap 301, a pressure plate 302, and a screw 303.
[0048] Similarly, it can be seen that the axial pressure cap tooling Ⅲ3-3 consists of three parts and is axially clamped. The tooling structure is simple, the number of components is reduced, the clamping and positioning are accurate, the clamping is stable, and it is economical and practical.
[0049] In the above embodiments, further: the pressure cap 301 of the axial pressure cap tooling Ⅲ3-3 is a thick-walled cylindrical structure, and the pressure cap 301 has a central positioning countersunk hole concentrically formed in the center; the central positioning countersunk hole is concentrically adapted to the outer contour of the end of the part 1 processed in step S2.
[0050] During processing, the pressure cap 301 is clamped and positioned on the equipment using a three-jaw chuck, thus achieving the clamping and positioning of part 1.
[0051] An axial set screw hole is formed on one side of the central positioning countersunk hole of the pressure cap 301; the center line of the axial set screw hole is parallel to the center line of the pressure cap 301; the pressure plate 302 of the axial pressure cap tooling Ⅲ3-3 has an L-shaped structure, and the horizontal plate of the pressure plate 302 has an axial through hole; the screw 303 of the axial pressure cap tooling Ⅲ3-3 passes through the axial through hole of the pressure plate 302 and then screws into the axial set screw hole of the pressure cap 301 to axially press and fix the part 1.
[0052] In step S4, when machining the internal thread, the axial pressure cap fixture Ⅲ3-3 is used, employing three pressure plates 302 and three screws 303, so that... Part 1 is fixed circumferentially around the upper end face of 300h7 to prevent radial stress on part 1. In this process, the following is adopted: 300h7 outer circle positioning or alignment For the outer diameter of 300h7, use the method of replacing the pressure plate 302 to machine an M250×1.5-6H thread. It should be noted that if the outer diameter of 300h7 fits properly with the center positioning countersunk hole of the pressure plate 301, then there is no need to align the outer diameter of 300h7 during subsequent machining.
[0053] It should also be noted that: although the machining datum for the internal thread here is... 300h7, but in the finishing step S2, 254H6 inner hole and The 300h7 outer circle is machined in one operation. The coaxiality deviation between the datum inner hole and the threaded hole required in the drawing is fully met in this operation. The machining process is only a conversion of the datum.
[0054] The present invention also includes a high-precision machining fixture for large-size thin-walled parts, including axial pressure cover fixture I3-1, axial pressure cover fixture II3-2, and axial pressure cover fixture III3-3.
[0055] Part 1 has a process step inner hole 2 that extends inward from the shaft end by being precision machined using the rough machining allowance of the blank itself.
[0056] The axial pressure cap fixture I3-1 has a pressure cap 301 with a thick-walled cylindrical structure, and the pressure cap 301 has a concentric countersunk hole at its center. The concentric countersunk hole is concentrically fitted to the outer contour of the inner hole 2 of the process step. The part 1 is positioned and clamped using the machined countersunk hole 2 of the process step as a reference. That is, the pressure plate 302 of the axial pressure cap fixture I3-1 axially presses the outer shaft end face of the inner hole 2 of the process step of the part; the pressure plate 302 has a central through hole; the screw 303 of the axial pressure cap fixture I3-1 passes through the central through hole of the pressure plate 302 and is concentrically screwed into the central internal thread hole of the pressure cap 301 to axially press and fix the part 1.
[0057] The axial pressure cap fixture II 3-2 has a pressure cap 301 with a thick-walled cylindrical structure, and the pressure cap 301 has a concentric countersunk hole at its center; the concentric countersunk hole is concentrically fitted to the outer contour of the finished end of part 1. The finished outer contour of part 1 is used as a reference for clamping and positioning the part. That is, the pressure plate 302 of the axial pressure cap fixture II 3-2 axially presses the outer shaft end face of the inner hole 2 of the process step of the part; the pressure plate 302 has a central through hole; the screw 303 of the axial pressure cap fixture II 3-2 passes through the central through hole of the pressure plate 302 and is screwed into the central internal thread hole of the pressure cap 301 to axially press and fix part 1.
[0058] The axial pressure cap fixture III3-3 has a pressure cap 301 with a thick-walled cylindrical structure, and a central positioning countersunk hole is concentrically formed in the center of the pressure cap 301. The central positioning countersunk hole is concentrically fitted to the outer contour of the machined end of part 1. The part is clamped and positioned using the machined outer contour of one end of part 1 as a reference. That is, an axial set screw hole is formed on one side of the central positioning countersunk hole of the pressure cap 301; the center line of the axial set screw hole is parallel to the center line of the pressure cap 301; the pressure plate 302 of the axial pressure cap fixture III3-3 has an L-shaped structure, and an axial through hole is formed in the middle of the horizontal plate of the pressure plate 302; the screw 303 of the axial pressure cap fixture III3-3 passes through the axial through hole formed in the pressure plate 302 of the axial pressure cap fixture III3-3 and is screwed to fit and connect to the axial set screw hole of the pressure cap 301 to axially press and fix part 1.
[0059] As can be seen, this invention can accurately machine the design datum for thin-walled, large-sized parts; and when machining the datum hole, a three-jaw chuck is not used to hold the part, avoiding radial force on the part, but axial force is applied to the workpiece through an axial pressure cap tooling; and only by accurately machining the inner hole of the process step as the datum hole can it be ensured that all other relevant dimensions in the drawing meet the design requirements; such as Figures 3 to 5 The machining process is shown; the geometric tolerances and dimensional tolerances in the drawings are guaranteed; and by converting different positioning datums in different machining steps, the coaxiality deviation between the internal thread and the internal hole in subsequent machining is ensured to meet the requirements of the drawings.
[0060] Meanwhile, the inner hole of the process step in this invention can act as a reinforcing rib. That is, the inner hole of the part... This involves high-precision, large-size internal holes. While ensuring the dimensions of the process step internal hole, its ellipticity and roughness are also important factors affecting product accuracy. During boring, multiple small feeds are required. The process step internal hole, i.e., the process head, increases the wall thickness of the internal hole, increases the contact area, and acts as a reinforcing rib. This effectively avoids adverse factors during machining, such as chatter marks, tool deflection, and insufficient heat dissipation, which affect the surface roughness, taper, and cylindricity of the internal hole. It solves the common problems encountered in machining large, thin-walled workpieces, ensuring the production of qualified products that meet design requirements.
[0061] Furthermore, this invention utilizes the original drawings to design the tooling, eliminating the need for additional manufacturing costs. In machining processes, it's common to encounter examples where additional clamping heads are needed to meet design requirements, only to be removed after machining. While this method produces qualified products, it significantly increases production costs for manufacturers in mass production. The process head design in this invention, using the inner hole of the process step, breaks with conventional machining methods, providing manufacturers with a new machining approach. It cleverly utilizes the roughing allowance of the rough-machined part to provide a clamping reference for subsequent finishing, without incurring additional production costs.
[0062] As can be seen from the above description, this invention proposes a novel processing approach, cleverly utilizing the blank allowance of the rough-machined part to provide a clamping and positioning reference for subsequent finish machining. No additional production costs are required. It is economical and practical, with stable and reliable clamping, high precision, and no part deformation.
[0063] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.
[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.
Claims
1. A method for machining large-size thin-walled parts with high precision, characterized in that: Using the roughing allowance of the part (1) itself, the inner hole (2) of the process step extending inward from the shaft end is finished, and the inner hole (2) of the process step is used as the positioning reference for subsequent machining. The part is axially clamped and machined using an axial pressure cover fixture (3) to obtain a shaped thin-walled part with the required accuracy; including the following steps: S1. Processing of the inner hole of the step: Using the rough machining allowance of the part (1), the inner hole of the process step (2) extending from the shaft end face to the center is finished. S2. Precision machining of one end: Using the inner hole (2) of the process step as a reference, use the axial pressure cover tool I (3-1) to concentrically and axially press the inner hole (2) of the process step, and process the high-precision process dimension structure required for the other end of the part (1); S3, precision machining of the outer contour: using the inner hole (2) of the process step and the outer contour of the end of the part processed in step S2 as a reference, use the axial pressure cover tool II (3-2) to concentrically press the part (1) in the axial direction, and process the high-precision process dimensions and structure required for the outer contour of the part (1); S4. Precision machining of the other end: Based on the high-precision process dimensions required for the other end of the part (1) processed in step S2, use the axial pressure cover tool III (3-3) to concentrically press the part (1) and process the high-precision process dimensions required for the part at the end where the inner hole (2) of the process step is located. The axial pressure cover fixture I (3-1), axial pressure cover fixture II (3-2), and axial pressure cover fixture III (3-3) are respectively composed of a pressure cover (301), a pressure plate (302), and a screw (303); The axial pressure cover fixture I (3-1) has a pressure cover (301) with a thick-walled cylindrical structure, and the pressure cover (301) has a concentric center positioning countersunk hole. The center positioning countersunk hole is concentrically matched with the outer contour of the inner hole (2) of the process step of the part (1). The pressure plate (302) of the axial pressure cover fixture I (3-1) axially presses the outer shaft end face of the inner hole (2) of the process step of the part. The pressure plate (302) has a center through hole. The screw (303) of the axial pressure cover fixture I (3-1) passes through the center through hole of the pressure plate (302) and is concentrically screwed to match the center internal thread hole of the pressure cover (301) to axially press and fix the part (1).
2. The high-precision large-size thin-walled part machining method according to claim 1, characterized in that: The axial pressure cover fixture II (3-2) has a pressure cover (301) with a thick-walled cylindrical structure, and the pressure cover (301) has a central positioning countersunk hole at its center. The central positioning countersunk hole is concentrically matched with the outer contour of the end of the part (1) as processed in step S2. The pressure plate (302) of the axial pressure cover fixture II (3-2) axially presses the outer shaft end face of the inner hole (2) of the process step of the part. The pressure plate (302) has a central through hole. The screw (303) of the axial pressure cover fixture II (3-2) passes through the central through hole of the pressure plate (302) and is screwed to fit the central internal thread hole of the pressure cover (301) to axially press and fix the part (1).
3. The high-precision large-size thin-walled part machining method according to claim 1, characterized in that: The axial pressure cover fixture III (3-3) has a thick-walled cylindrical structure for its pressure cover (301), and a central positioning countersunk hole is concentrically formed in the center of the pressure cover (301). The central positioning countersunk hole is concentrically adapted to the outer contour of the end of the part (1) as processed in step S2. An axial tightening screw hole is formed on one side of the central positioning countersunk hole of the pressure cover (301). The center line of the axial tightening screw hole is parallel to the center line of the pressure cover (301). The pressure plate (302) of the axial pressure cover fixture III (3-3) has an L-shaped structure, and the horizontal plate of the pressure plate (302) has an axial through hole. The screw (303) of the axial pressure cover fixture III (3-3) passes through the axial through hole of the pressure plate (302) and then screws into the axial tightening screw hole of the pressure cover (301) to axially press and fix the part (1).