A fixture and method for clamping thin-walled welded parts

Abstract

This application provides a fixture and method for clamping and machining thin-walled welded parts, relating to the field of fixture and tooling technology. The fixture includes a base mechanism, a central positioning mechanism, an angular positioning structure, an auxiliary support mechanism, and a clamping mechanism. The base mechanism uses a disc and multiple circumferentially arranged elongated plates to form a support surface; the central positioning mechanism mates with the positioning inner hole of the part to achieve central positioning; the angular positioning structure mates with the angular hole of the part to achieve angular positioning; the auxiliary support mechanism is set for each lug to be machined, using V-shaped supports and lateral limiting components to provide auxiliary support and limit the lugs to be machined; the clamping mechanism clamps the part to the clamping reference surface. This solution can improve the clamping stability, positioning accuracy, and local rigidity during machining of thin-walled welded parts, reduce vibration and lateral displacement of the lugs to be machined, and reduce the risk of cracking at the weld joint.

Description

Technical Field

[0001] This application relates to the field of fixture and tooling technology, and more specifically, to a fixture and method for clamping and machining thin-walled welded parts. Background Technology

[0002] Thin-walled welded parts are widely used in combustion chamber casings and similar shell structures. These parts are typically formed by welding multiple thin-walled components, and are characterized by large overall dimensions, complex structures, thin walls, high residual stress after welding, and insufficient local rigidity. Subsequent machining processes usually require end-face machining and threading of the lugs, bosses, and related connecting parts on the outer wall of the part to meet assembly dimensional accuracy, positional accuracy, and geometrical accuracy requirements. Due to the poor rigidity of these parts and the fact that many machined areas are overhanging or weak points, they are prone to vibration and deformation under the combined action of clamping and cutting forces during clamping and cutting. In severe cases, this can even lead to cracking at the weld joints, thus affecting the final machining quality of the part.

[0003] In the prior art, there are already publicly available solutions that use tooling fixtures to constrain thin-walled welded parts. For example, Chinese patent document CN2019110340495A discloses an integrated tooling fixture and its assembly method for the welding and heat treatment of thin-walled casings. This solution mainly uses a dedicated tooling fixture to continuously constrain the thin-walled casing throughout the welding and heat treatment process, keeping the casing's profile under control at all times. This controls the deformation trend during welding and heat treatment and ensures the final dimensional accuracy of the parts.

[0004] However, the aforementioned prior art has at least the following shortcomings: On the one hand, the existing technology is mainly geared towards welding and heat treatment processes. Its tooling design focuses on overall shape control during the welding and heat treatment stages. However, it does not provide targeted solutions for issues such as clamping stability, local rigidity improvement, and machining interference avoidance during the subsequent machining stages of thin-walled welded parts, especially when machining local areas such as lugs and bosses. Therefore, when the parts enter the milling and other machining stages, problems such as vibration, deformation, and difficulty in ensuring dimensional accuracy in local machined areas still easily occur.

[0005] On the other hand, the existing technology uses a dedicated fixture structure, some of which requires special design for specific parts. While this can meet the usage requirements of specific thin-walled casings in welding and heat treatment processes, it suffers from poor versatility and insufficient reusability. When the part structure or machining area changes, the fixture often needs to be redesigned, which is not conducive to the flexible clamping and rapid adjustment of similar thin-walled welded parts during the machining stage.

[0006] Furthermore, since the tooling of this existing technology mainly emphasizes the constraint of the overall surface of the part, its technical solution does not highlight rigid reinforcement measures for locally weak machining areas. For machining areas such as lugs on thin-walled welded parts, when the machining allowance is large or the cutting force is concentrated, if there is a lack of effective local auxiliary support and clamping structure, local areas are prone to vibration and elastic displacement, which will affect the consistency of machining dimensions, end face perpendicularity and related machining quality. In severe cases, it may even cause cracks at the welded joint of the lug.

[0007] Therefore, existing technologies still have the following problems: existing tooling is mainly suitable for overall deformation control during the welding and heat treatment stages, and it is difficult to take into account the requirements of overall clamping stability, rigidity improvement of local weak points, and machine tool adaptability for thin-walled welded parts during the machining stage. Based on this, there is an urgent need to provide a clamping method and corresponding fixture structure suitable for the machining stage of thin-walled welded parts, so as to improve clamping stability, local rigidity, and machining accuracy during the machining process. Summary of the Invention

[0008] The purpose of this application is to provide a fixture and method for machining and clamping thin-walled welded parts, in order to address the shortcomings of the above-mentioned technology.

[0009] To achieve the above objectives, the technical solution adopted in this application is as follows: One aspect of this application provides a fixture for machining and clamping thin-walled welded parts, including a base mechanism, a center positioning mechanism, an angular positioning structure, an auxiliary support mechanism, and a clamping mechanism; The base mechanism includes a disk and multiple extension plates fixedly mounted along the circumference of the disk, the upper end surfaces of the multiple extension plates forming a support surface for supporting the mounting reference surface of the parts; There are multiple center positioning mechanisms, which are spaced apart along the circumference of the disk and located on the same positioning circle. Each of the multiple center positioning mechanisms is used to cooperate with the inner circumferential wall of the positioning inner hole of the part, so that the center of the positioning circle coincides with the center of the positioning inner hole of the part, thereby achieving center positioning. An angular positioning structure is set on one of the extension plates and is used to mate with the inner peripheral wall of the angular hole of the part to restrict the rotation of the part around the center of the positioning inner hole of the part, thereby achieving angular positioning. The auxiliary support mechanism is installed on the extension plate and is arranged to correspond to each lug to be processed in the part. Each auxiliary support mechanism includes a support installed on the extension plate, a V-shaped support installed on the support, and lateral limiting members installed on both sides of the support. The V-shaped support is used to support the bottom of the corresponding lug to be processed, and the lateral limiting members are used to clamp the two sides of the corresponding lug to be processed. The clamping mechanism is mounted on the extension plate and is used to press against the clamping reference surface on the outer periphery of the part mounting reference surface.

[0010] Furthermore, multiple extension plates are distributed circumferentially along the disk, and reserved positions for machine tool clamping fixtures are formed between adjacent extension plates.

[0011] Furthermore, each center positioning mechanism includes a step plate and a positioning pin. The step plate is mounted on the disc, and the positioning pin is mounted on the step plate. The positioning pins of multiple center positioning mechanisms are located on the same positioning circle and respectively cooperate with the inner peripheral wall of the positioning inner hole of the part to achieve center positioning.

[0012] Furthermore, the angular positioning structure includes a mounting groove disposed on one of the extension plates and an angular pin installed in the mounting groove, the angular pin being used to engage with the inner peripheral wall of the angular hole of the part to achieve angular positioning.

[0013] Furthermore, the V-shaped support is movably mounted on the top of the support along the radial direction of the disk to accommodate the lugs to be processed with different degrees of outward protrusion.

[0014] Furthermore, the lateral limiting component is a knurled screw.

[0015] Furthermore, the auxiliary support mechanism also includes connecting plates installed on both sides of the support, and lateral limiting members are movably installed on the connecting plates along the width direction of the lug to be processed, so as to accommodate lugs of different widths to be processed.

[0016] Furthermore, the number of auxiliary support mechanisms corresponds to the number of lugs to be processed, with one auxiliary support mechanism provided for each lug to be processed; The support heights of each auxiliary support mechanism are different to correspond to the lugs to be processed at different height positions.

[0017] Furthermore, the clamping mechanism includes multiple pressure plates distributed along the circumference of the part, which are used to press against the clamping reference surface of the part from different directions.

[0018] Another aspect of this application provides a method for machining and clamping thin-walled welded parts, comprising: Based on the maximum rotation diameter and height of the part, as well as the distribution of the structure to be processed on the outer wall of the part, determine the size of the disk, the number and arrangement of the extension plates, and fix multiple extension plates circumferentially on the disk to form a base mechanism. The upper end surfaces of the multiple extension plates form a support surface for supporting the mounting reference surface of the part. A fixture is formed by mounting a central positioning mechanism, an angular positioning structure, an auxiliary support mechanism, and a clamping mechanism on a base mechanism. The central positioning mechanism consists of multiple mechanisms, which are spaced apart along the circumference of the disc and located on the same positioning circle. Each of the multiple central positioning mechanisms is used to cooperate with the inner circumferential wall of the positioning inner hole of the part, so that the center of the positioning circle coincides with the center of the positioning inner hole of the part, thereby achieving central positioning. The angular positioning structure is set on one of the extension plates and is used to cooperate with the inner circumferential wall of the angular hole of the part to achieve angular positioning. The auxiliary support mechanism is set on the extension plate and is arranged corresponding to the lugs to be processed in the structure to be processed on the outer wall of the part. The clamping mechanism is set on the extension plate and is used to press against the clamping reference surface of the part. The part is clamped on the fixture so that the mounting reference surface of the part is in contact with the support surface. The positioning inner hole of the part cooperates with the center positioning mechanism to achieve center positioning. The corner hole of the part cooperates with the corner positioning structure to achieve corner positioning. The clamping reference surface of the part is pressed against by the clamping mechanism. Adjust each auxiliary support mechanism so that the V-shaped support in each auxiliary support mechanism cooperates with the corresponding lug to be processed to form an auxiliary support, and the lateral limiting component cooperates with both sides of the corresponding lug to be processed to limit the lateral displacement of the lug to be processed during the processing. After fixing the fixture on the machine tool worktable and correcting the relative relationship between the clamping datum determined by the part's positioning inner hole, angular hole and mounting datum surface and the machine tool datum, the outer wall structure to be machined is machined.

[0019] The beneficial effects of this application include: This application provides a fixture and method for clamping thin-walled welded parts during machining. Compared with the closest prior art, this application is not only applicable to clamping thin-walled welded parts during the machining stage, but also establishes a stable support, centering, orientation, and clamping relationship through the cooperation of a base mechanism, a center positioning mechanism, an angular positioning structure, an auxiliary support mechanism, and a clamping mechanism, enabling the parts to maintain a clear and stable clamping datum during machining. By using a disc adapted to the part size and an extension plate that meets the layout and quantity requirements, the overall structure of the fixture is simplified, the number of components is reduced, and the assembly difficulty and assembly time are significantly reduced. At the same time, the reserved space formed between adjacent extension plates provides sufficient installation space for the machine tool clamping fixture, improving the problems of compact clamping positions and inconvenient clamping and operation in the original solution.

[0020] Furthermore, this application improves the overall rigidity of the fixture by optimizing the arrangement and structural design of the extension plates, reducing vibration and deformation of thin-walled welded parts during processing. Simultaneously, by using a reinforced connection structure that avoids adverse effects on the flatness of the extension plate support surface, the support surface maintains good flatness, facilitating precise measurement and adjustment. For the lugs to be processed on the outer wall, this application sets up an auxiliary support mechanism. The V-shaped support provides auxiliary support for the lugs, and the lateral limiting components cooperate with both sides of the lugs to provide targeted reinforcement to locally weak processing areas. This significantly improves the local rigidity of the lugs and other processing parts, reduces lateral displacement, vibration, and deformation during processing, lowers the risk of cracks at welded joints, and ensures the dimensional accuracy, positional accuracy, and processing quality of the outer wall structure to be processed. Therefore, this application not only solves the problems of complex structure, insufficient rigidity, compact clamping position, and inconvenience in measurement and operation of the original combined fixture scheme, but also provides a more effective way to achieve high-precision, high-stability machining clamping for thin-walled welded parts. Attached Figure Description

[0021] Figure 1 This is one of the structural schematic diagrams of a thin-walled weldable part provided in this application; Figure 2 This is the second structural schematic diagram of a thin-walled weldable part provided in this application; Figure 3 A schematic diagram of the structure of a fixture for machining and clamping thin-walled welded parts provided in this application; Figure 4 A schematic diagram of the base mechanism of a clamp provided in this application; Figure 5 This application provides a schematic diagram of the structure of a center positioning mechanism for a clamp. Figure 6 A schematic diagram of the auxiliary support mechanism for a clamp provided in this application; Figure 7 This is a schematic diagram of the structure of a thin-walled welded part and fixture after assembly, as provided in this application.

[0022] Icons: 11-Part; 12-Lumber; 13-Boss; 14-Mounting reference surface; 15-Clamping reference surface; 16-Positioning inner hole; 17-Angular hole; 2-Clamp; 21-Base mechanism; 211-Disc; 212-Extension plate; 22-Center positioning mechanism; 221-Step plate; 222-Positioning pin; 23-Angular pin; 24-Auxiliary support mechanism; 241-Support; 242-V-shaped support; 243-Connecting plate; 244-Lateral limiting component; 25-Pressure plate; 26-Reserved position. Detailed Implementation

[0023] One aspect of this application provides a fixture 2 for clamping and machining thin-walled welded parts 11, particularly suitable for large-sized thin-walled welded components with multiple lugs 12 and bosses 13 distributed on the outer wall, requiring end-face machining and thread machining. These parts 11 typically have large overall dimensions, thin walls, weak rigidity after welding, and numerous localized external wall machining structures. After the part 11 enters the machining stage, it is necessary to ensure accurate overall clamping position while preventing vibration, displacement, and cracking of the welded joints in the lugs 12 under cutting forces. Therefore, the fixture 2 not only needs to solve the overall support and positioning problems of the part 11 but also needs to consider the rigidity enhancement and stress stability of the locally weak machining areas.

[0024] like Figures 1 to 7 As shown, to meet the aforementioned processing requirements, the fixture 2 first establishes a base mechanism 21. The base mechanism 21 includes a disc 211 and multiple extension plates 212 fixedly mounted circumferentially along the disc 211. The upper surfaces of the extension plates 212 form a support surface for the mounting reference surface 14 that supports the part 11. The disc 211 provides an overall load-bearing base and mounting base. The extension plates 212 are mounted on the disc 211 to form distributed support in the circumferential direction, allowing the part 11 to receive support over a larger range during clamping. Preferably, the bottom of the extension plate 212 is provided with a locating key, and the disc 211 is provided with a locating groove that mates with the locating key. The locating key is fixed in the locating groove by a threaded connection, thereby allowing the extension plate 212 to be mounted on the disc 211. By combining the maximum rotation diameter and height of part 11 with the distribution of the structure to be machined on the outer wall of part 11, the size of disk 211, the number of extension plates 212, and their arrangement can be determined to match the support range with the shape characteristics of part 11, the distribution of the area to be machined, and the machine tool installation conditions. In this application, the size of disk 211 is close to the maximum rotation diameter of part 11. The base mechanism 21 formed in this way can provide a mounting foundation for subsequent positioning, clamping, and local reinforcement while ensuring support stability, and shorten the overhang of extension plates 212 to reduce the vibration of fixture 2 during machining.

[0025] After the base mechanism 21 is formed, a central positioning mechanism 22, an angular positioning structure, an auxiliary support mechanism 24, and a clamping mechanism are further installed on it. Multiple central positioning mechanisms 22 are arranged at intervals along the circumference of the disk 211 and located on the same positioning circle. Each of the multiple central positioning mechanisms 22 engages with the inner circumferential wall of the positioning inner hole 16 of the part 11, ensuring that the center of the positioning circle, the center of the disk 211, and the center of the positioning inner hole 16 of the part 11 coincide, thus achieving central positioning. This central positioning is one of the core elements of establishing the entire clamping datum. By establishing the central datum through the positioning inner hole 16 of the part 11, which has high machining accuracy and good positional consistency, it is possible to ensure that the part 11 has a clear central position relative to the fixture 2 and the machine tool. The angular positioning structure is installed on one of the extension plates 212 and engages with the inner circumferential wall of the angular hole 17 of the part 11 to restrict the rotation of the part 11 around the center of the positioning inner hole 16, thus achieving angular positioning. The center positioning addresses the limitation of the center position of part 11, while the angular positioning addresses the limitation of the rotation angle of part 11 around the central axis. When the two work together, the position and orientation of part 11 in the plane are clearly established. The clamping mechanism is mounted on the extension plate 212 and is used to press against the clamping reference surface 15 on the outer periphery of the mounting reference surface 14 of part 11, ensuring that part 11 remains stably fitted within the position defined by the supporting surface, the center positioning mechanism 22, and the angular positioning structure.

[0026] When clamping part 11, the mounting reference surface 14 of part 11 is first brought into contact with the support surface to establish a basic support relationship. After the mounting reference surface 14 is in contact with the support surface, the posture of part 11 in the axial direction and the support direction is initially stabilized. Subsequently, the positioning inner hole 16 of part 11 cooperates with the center positioning mechanism 22 to achieve center positioning; the angular hole 17 of part 11 cooperates with the angular positioning structure to achieve angular positioning. After these two positioning operations, the state of part 11 in the center position and the angular position is defined. Then, the clamping mechanism applies a clamping action to the clamping reference surface 15 on the outer periphery of the mounting reference surface 14 of part 11, so that part 11 is stably held on the established clamping reference. In this way, the support surface is responsible for supporting part 11, the center positioning mechanism 22 is responsible for centering, the angular positioning structure is responsible for orientation, and the clamping mechanism is responsible for maintaining a stable contact relationship between part 11 and the fixture 2, forming a continuous and complete clamping logic.

[0027] The auxiliary support mechanism 24 is arranged to support each lug 12 to be processed on the part 11. The lugs 12 on thin-walled welded parts 11 are typically weak areas that are locally protruding and welded to the main body. During processing, they are easily subjected to cutting forces, resulting in lateral displacement and local vibration. The auxiliary support mechanism 24 is mounted on the extension plate 212. Its function is not to replace the overall support, but rather to provide targeted local reinforcement to the lugs 12 to be processed, based on the overall clamping of the part 11. The V-shaped support member 242 in the auxiliary support mechanism 24 supports the bottom of the lug 12 to be processed, and the lateral limiting member 244 clamps the two sides of the lug 12 to be processed, forming lateral limits. The V-shaped support member 242 provides bottom support for the lug 12, giving it a clear stress support point during processing; the lateral limiting member 244 restricts the two sides of the lug 12, keeping it within a predetermined position range during cutting and reducing lateral displacement. Through the combined effect of auxiliary support and lateral restraint, the local vibration and displacement of the lug 12 during the processing are suppressed, and the additional load borne by the welded connection area at the root of the lug 12 is also reduced.

[0028] After fixture 2 is installed on the machine tool table, it is necessary to correct the relative relationship between the clamping datum and the machine tool datum, which is determined by the positioning inner hole 16, the angular hole 17, and the mounting datum surface 14 of part 11. The positioning inner hole 16 of part 11 reflects the center position of part 11, the angular hole 17 reflects the angular position of part 11 around the central axis, and the mounting datum surface 14 reflects the planar datum state of part 11 in fixture 2. The three together constitute the clamping datum of part 11 in fixture 2. After the correction between the clamping datum and the machine tool datum is completed, a stable correspondence is formed between the machining trajectory of the machine tool and the actual clamping state of part 11. The machining position of the structure to be machined on the outer wall of part 11 can be accurately unfolded around the center of part 11 and the datum surface. Thus, the dimensional relationship, angular relationship, and spatial position relationship of the structure to be machined on the outer wall can remain consistent during machining.

[0029] This solution is applicable to thin-walled welded parts 11, such as combustion chamber casings, whose outer walls have multiple lugs 12 and bosses 13. For these parts 11, the number of structures to be machined on the outer wall is usually large, with complex circumferential distribution and varying local heights. Conventional clamping methods struggle to simultaneously meet both overall clamping accuracy and the rigidity requirements of the lugs 12 to be machined. Using the above clamping solution, the base mechanism 21 provides overall stable support, the center positioning mechanism 22 and the angular positioning structure establish accurate center and angular references, the clamping mechanism maintains a stable fit between the part 11 and the fixture 2, and the auxiliary support mechanism 24 provides localized reinforcement support and lateral restraint for the lugs 12 to be machined. This allows for the balance of overall stability and local machining stability of the part 11 in a single clamping operation, improving the dimensional and positional accuracy of the structures to be machined on the outer wall, reducing vibration and deformation during machining, and lowering the risk of cracks at the welded joints of the lugs 12.

[0030] Furthermore, such as Figure 4 As shown, in the overall arrangement of the fixture 2, multiple extension plates 212 are distributed circumferentially along the disk 211, and reserved positions 26 for machine tool clamping of the fixture 2 are formed between adjacent extension plates 212. These reserved positions 26 are not simply structural gaps, but rather installation spaces determined during the fixture 2 layout stage in conjunction with the clamping requirements of the machine tool worktable, the external dimensions of the part 11, and the machining path. For large-sized, thin-walled welded parts 11, the fixture 2 must provide sufficient support range without overcrowding the effective area of ​​the worktable due to excessively dense support elements; otherwise, it will be difficult to arrange the machine tool clamping elements, and the installation relationship between the fixture 2 and the machine tool will be difficult to establish. By distributing multiple extension plates 212 around the disk 211 and forming reserved positions 26 for the machine tool clamping fixture 2 between adjacent extension plates 212, sufficient space can be provided for the machine tool clamping plate, clamping block or other worktable clamping components while supporting the mounting reference surface 14 of the supporting part 11. This makes the fixing operation of the fixture 2 smoother and makes it easier to obtain a stable machine tool connection state after the fixture 2 is installed.

[0031] Furthermore, the circumferential distribution of multiple extension plates 212 along the disk 211 has a direct effect: it helps to form a more balanced circumferential force state with the disk 211 body. After the part 11 is installed, the mounting reference surface 14 is supported by multiple extension plates 212, and the supporting force is no longer concentrated in a few local positions. The weight of the part 11, the clamping force, and the processing load can be distributed and transferred to the disk 211. For welded parts 11 with thin walls and weak overall rigidity, this distributed support method helps to reduce the additional deformation caused by local force concentration. At the same time, the reserved positions 26 formed between the extension plates 212 allow the mounting points of the fixture 2 and the support points of the part 11 to be reasonably staggered in space, avoiding interference between the machine tool clamping area and the processing area and measurement area of ​​the part 11, thus taking into account the needs of fixture 2 support, fixture 2 fixation, and actual processing.

[0032] Furthermore, such as Figure 5 As shown, each center positioning mechanism 22 includes a step plate 221 and a positioning pin 222. The step plate 221 serves for installation and position adjustment, while the positioning pin 222 engages with the inner circumferential wall of the positioning inner hole 16 of the part 11 to establish a center reference. For this type of thin-walled welded part 11, the contact between the mounting reference surface 14 and the support surface alone is insufficient to accurately define the center position of the part 11. Therefore, it is necessary to utilize the positioning inner hole 16 on the part 11, which has high precision and good positional consistency, to establish a center positioning relationship. The positioning pins 222 in the multiple center positioning mechanisms 22 are located on the same positioning circle and engage with the inner circumferential wall of the positioning inner hole 16 respectively, so that the center of the positioning circle, the center of the disk 211, and the center of the positioning inner hole 16 coincide, thereby ensuring that the center position of the part 11 on the fixture 2 is accurate and stable.

[0033] The stepped plate 221 is mounted on the disc 211. Preferably, the bottom of the stepped plate 221 is provided with a locating key, and the disc 211 is provided with a locating groove that mates with the locating key. The locating key is fixed in the locating groove by a threaded connection, thereby allowing the stepped plate 221 to be mounted on the disc 211. After the locating pin 222 is installed on the stepped plate 221, it can form a clear correspondence between the center of the part 11 and the center of the fixture 2 by mates with the inner peripheral wall of the locating inner hole 16 of the part 11. This arrangement enables the part 11 to quickly establish a stable central reference after clamping, providing a basis for subsequent angular positioning and machine tool alignment.

[0034] The step plate 221 here serves more than just a simple connecting function. Since the disc 211 bears the overall load and serves as the installation foundation, and the locating pin 222 needs to form a precise fit with the locating inner hole 16 of the part 11, a structure is needed between the disc 211 and the locating pin 222 to determine the position and support the installation. After the step plate 221 is installed on the disc 211, it makes the installation position of the locating pin 222 clearer and facilitates dimensional verification and position adjustment of the central positioning mechanism 22 during the assembly stage. For thin-walled welded parts 11 that are large in size and have high positioning requirements, this "disc 211—step plate 221—locating pin 222" installation relationship helps ensure the installation accuracy and repeatability of the central positioning mechanism 22, allowing the part 11 to return to the same central position relatively stably each time it is clamped.

[0035] In practical applications, after part 11 is clamped onto fixture 2, multiple locating pins 222 engage with the inner peripheral wall of the locating inner hole 16 of part 11, thereby determining the center position of part 11. The mounting reference surface 14 and the support surface provide planar support, and the engagement of multiple locating pins 222 with the inner peripheral wall of the locating inner hole 16 provides center positioning. With these two combined, the spatial position of part 11 in fixture 2 is no longer simply maintained by clamping force, but is established on a clear reference relationship. Subsequently, with the cooperation of angular positioning structure and clamping mechanism, part 11 can complete angular positioning and reliable clamping while maintaining a stable center position. For applications requiring high dimensional accuracy from the machining part to the center of part 11, the setting of the center positioning mechanism 22 is directly related to the accuracy of the final dimensional reference. Therefore, the engagement structure of the step plate 221 and the locating pins 222 plays a crucial role in establishing the reference throughout fixture 2.

[0036] Furthermore, an angular positioning structure is provided on one of the extension plates 212, and includes a mounting groove on the extension plate 212 and an angular pin 23 installed in the mounting groove. The mounting groove provides the mounting position and direction of the angular pin 23, which engages with the inner circumferential wall of the angular hole 17 of the part 11 to establish an angular reference for the part 11 about the center of the positioning inner hole 16. For a thin-walled welded part 11 that is approximately a body of revolution, center positioning can only determine "where the part 11 is located," but cannot limit "what angle the part 11 rotates around the central axis." Without the angular positioning structure, even if the center position of the part 11 is correct, the specific positions of the outer wall lug 12 and the boss 13 in the circumferential direction may still deviate, thus affecting the angular relationship between each machined part and the center and end face of the part 11. Therefore, by providing a mounting groove on one of the extension plates 212 and installing an angular pin 23 in the mounting groove, so that the angular pin 23 engages with the inner peripheral wall of the angular hole 17 of the part 11, the angular position of the part 11 can be clearly defined.

[0037] Setting the mounting slot on the extension plate 212 instead of adding a separate large additional structure helps maintain the compact overall layout of the fixture 2. The extension plate 212 itself already participates in forming the support surface of the mounting reference surface 14 of the part 11 and is located at a predetermined position in the circumference of the disk 211. Further setting the angular positioning structure at this location can directly utilize the existing space and mounting foundation of the base mechanism 21 without adding a complex large connection structure. This facilitates assembly and allows for unified consideration of the support, angular positioning, and machine tool mounting relationships in the overall layout of the fixture 2. The mounting slot provides a clear mounting position for the angular pin 23, enabling the angular pin 23 to be stably positioned in the direction and position that mates with the angular hole 17 of the part 11. After the angular pin 23 enters the angular hole 17 of the part 11, the rotational freedom of the part 11 around the center of the positioning inner hole 16 is restricted, thereby forming a stable angular positioning relationship.

[0038] In practice, when clamping part 11, the center position is first established by the center positioning mechanism 22, and then the angular positioning relationship is established by the engagement of the angular pin 23 with the inner circumferential wall of the angular hole 17. After the center positioning and angular positioning are combined, the planar position and circumferential posture of part 11 in the fixture 2 are simultaneously defined, and then this positioning state is maintained by the clamping mechanism. This ensures that the circumferential positions of the multiple lugs 12 and bosses 13 on the outer wall remain consistent in the machine tool coordinate system, so that the spatial relationship of each machining part relative to the center and reference plane of part 11 is accurate and reliable during subsequent machining. For part 11, which has many machining structures on the outer wall and a complex circumferential distribution, the introduction of the angular positioning structure makes the entire fixture 2 no longer just a support and clamping platform, but a complete clamping system with support, centering and orientation capabilities.

[0039] Furthermore, to ensure the local stability of the lugs 12 on the outer wall of the thin-walled welded part 11 during processing, auxiliary support mechanisms 24 are provided on the extension plate 212 corresponding to each lug 12. The auxiliary support mechanisms 24 do not re-clamp the part 11 as a whole, but rather establish auxiliary support and lateral limiting relationships for the locally weak area of ​​the lug 12, ensuring that the lug 12 remains stable under cutting loads. For combustion chamber casing-type parts 11 with multiple lugs 12 distributed on the outer wall, the number of auxiliary support mechanisms 24 corresponds one-to-one with the number of lugs 12, with one auxiliary support mechanism 24 configured for each lug 12, ensuring that each lug 12 has independent local reinforcement support during processing. This arrangement ensures that the local support corresponds one-to-one with each lug 12, avoiding the problem of inconsistent rigidity conditions at different processing positions caused by only reinforcing a portion of the lugs 12.

[0040] like Figure 6As shown, the auxiliary support mechanism 24 is mounted on the extension plate 212. Its basic mounting unit includes a support 241, a V-shaped support member 242, a lateral limiting member 244, and a connecting plate 243 that cooperates with the lateral limiting member 244. The support 241 is mounted on the extension plate 212, serving as the load-bearing foundation of the auxiliary support mechanism 24. The V-shaped support member 242 is mounted on the top of the support 241 to support the bottom of the corresponding lug 12 to be processed and form an auxiliary support. The connecting plate 243 is mounted on both sides of the support 241. The lateral limiting member 244 is movably mounted on the connecting plate 243 along the width direction of the lug 12 to be processed and clamps the two sides of the corresponding lug 12 to be processed, thereby forming a lateral limiting relationship. This arrangement enables the auxiliary support mechanism 24 to form a locally reinforced pattern of "central support and lateral limiting" in structure. The V-shaped support 242 in the middle provides support and force fulcrum for the bottom of the lug 12 to be processed, and the lateral limiting members 244 on both sides restrict the position of the lug 12 to be processed in the width direction. With the two working together, the swinging, offset and local displacement of the lug 12 to be processed during processing are effectively suppressed.

[0041] Support 241 is mounted on extension plate 212. Preferably, support 241 has a locating key at its bottom, and extension plate 212 has a locating groove at its top that mates with the locating key. The locating key is fixed in the locating groove by a threaded connection, thereby allowing support 241 to be mounted on extension plate 212. V-shaped support 242 is mounted on top of support 241. Preferably, V-shaped support 242 has a locating key at its bottom, and support 241 has a locating groove at its top that mates with the locating key. The locating key is fixed in the locating groove by a threaded connection, thereby allowing V-shaped support 242 to be mounted on top of support 241. Further, V-shaped support 242 is radially movably mounted on top of support 241 along disk 211 to accommodate lugs 12 with different degrees of protrusion. Lugs 12 at different locations on different parts 11, or at different positions on the same part 11, often differ in terms of protrusion amount, distance from the outer wall of the main body, and tool approach path during machining. If the position of the V-shaped support 242 remains fixed, it is difficult to meet the support requirements of lugs 12 with different degrees of protrusion, and machining interference may easily occur in local locations. By allowing the V-shaped support 242 to be radially movable on top of the support 241 along the disk 211, the V-shaped support 242 can be adjusted to a suitable position according to the degree of protrusion of the lug 12 to be machined, so that it can form a stable contact with the lug 12 to be machined, while avoiding the machining area and the tool running path. This ensures the effectiveness of the auxiliary support while also taking into account the machining operation space.

[0042] Connecting plates 243 are installed on both sides of support 241. Preferably, connecting plates 243 are installed on both sides of support 241 by threaded connection. Lateral limiting members 244 are movably installed on connecting plates 243 along the width direction of the lug 12 to be processed, so as to accommodate lugs 12 of different widths. Lateral limiting members 244 are preferably knurled screws. The reasons for using knurled screws are that, firstly, knurled screws are easy to adjust quickly by hand, and can be easily fine-tuned for lugs 12 at different positions during clamping; secondly, knurled screws can provide stable lateral limiting effect in a small installation space; and thirdly, by being movable along the width direction of the lug 12 to be processed, it can accommodate the size differences of lugs 12 of different widths. For lugs 12 at different positions of different parts 11 or the same part 11, their width may vary, and it is difficult to simultaneously adapt to all lugs 12 using only a fixed-interval lateral limiting structure. After setting the knurled screws to be movable along the width direction, the relative position between the knurled screws on both sides can be adjusted according to the width of the lug 12 to form a suitable clamping relationship with both sides of the lug 12. This can reliably limit the movement of narrower lugs 12, and also meet the processing requirements of wider lugs 12.

[0043] Besides radial and width adjustments, the heights of the supports 241 of each auxiliary support mechanism 24 are not entirely the same, but are set according to the distribution of the lugs 12 to be processed at different height positions. For parts 11 such as combustion chamber casings, although multiple lugs 12 are distributed circumferentially, their height positions are not completely consistent. If all supports 241 are the same height, some auxiliary support mechanisms 24 may not be in a reasonable support height relationship with the corresponding lugs 12 to be processed, resulting in support points that are too high or too low, thus affecting the local strengthening effect. By setting the supports 241 of different auxiliary support mechanisms 24 to different heights, the V-shaped support members 242 can correspond to the lugs 12 to be processed at different height positions, ensuring that each lug 12 can obtain support conditions that match its own position during processing. This ensures that the local strengthening state of the lugs 12 in all circumferential directions of the entire part 11 remains consistent, which is beneficial to improving the consistency of processing accuracy of each processing part.

[0044] The working process of the auxiliary support mechanism 24 in actual clamping is as follows: After the part 11 has completed overall support, center positioning, angular positioning and preliminary clamping, the auxiliary support mechanisms 24 corresponding to each lug 12 to be processed are adjusted respectively. First, the position of the V-shaped support 242 is adjusted so that it moves radially along the disk 211 to a position that matches the lug 12 to be processed, and forms an auxiliary support relationship with the lug 12 to be processed; then the knurled screws on both sides are adjusted so that the knurled screws move along the width direction of the lug 12 to be processed and clamp the corresponding sides of the lug 12 to be processed, thereby forming a limiting fit. In this way, the bottom of the lug 12 to be processed is supported by the V-shaped support 242, and the sides are restricted by the knurled screws, and its local degree of freedom is effectively converged. When the tool performs end face machining, local shape trimming or thread-related machining on the lug 12 to be processed, the lug 12 to be processed is not prone to significant lateral swing or root vibration due to the cutting force, which is conducive to maintaining stable machining dimensions, accurate end face position and local structural integrity.

[0045] Furthermore, after arranging the base mechanism 21, the center positioning mechanism 22, the angular positioning structure, and the auxiliary support mechanism 24, a clamping mechanism is needed to stably clamp the part 11. The clamping mechanism includes multiple pressure plates 25 distributed circumferentially around the part 11. These pressure plates 25 act on the clamping reference surface 15 of the part 11, applying clamping force from different directions. The clamping reference surface 15 is the reference area used by the part 11 to withstand the clamping force in its clamped state. This reference surface cooperates with the mounting reference surface 14; one is responsible for establishing a contact relationship with the support surface, and the other is responsible for bearing the clamping force applied by the clamping mechanism. By setting pressure plates 25 at multiple locations circumferentially around the part 11, the clamping force can be distributed circumferentially rather than concentrated on a single local location, thereby helping to reduce additional deformation of the thin-walled welded part 11 due to excessive local pressure.

[0046] The pressure plate 25 is mounted on the extension plate 212. Preferably, the pressure plate 25 is mounted on the extension plate 212 by a threaded connection. The clamping mechanism is set on the extension plate 212, indicating that the clamping mechanism does not exist independently of the base mechanism 21, but directly relies on the base mechanism 21 to form a force closed loop. The disc 211 and multiple extension plates 212 constitute the overall bearing base of the clamp 2. The mounting reference surface 14 of the part 11 is supported by the support surface formed by the upper end surface of the extension plate 212. The pressure plate 25 then applies a clamping action from the clamping reference surface 15 of the part 11. The part 11 is thus stably held on the clamping reference established by the support surface, the central positioning mechanism 22 and the angular positioning structure. The resulting force relationship is as follows: the support surface provides basic support, the central positioning mechanism 22 and the angular positioning structure determine the spatial position, and the pressure plate 25 is responsible for pressing the part 11 toward the predetermined reference state, so that the part 11 remains stably fitted during the processing and does not leave the original clamping position due to cutting force, vibration or local reinforcement mechanism adjustment.

[0047] The arrangement of multiple pressure plates 25 distributed circumferentially along the part 11 is suitable for the stress characteristics of large-sized, thin-walled welded parts 11. These parts 11 are relatively large and have weak overall rigidity. If clamping force is applied only at a few locations, the clamping effect is easily concentrated in a few localized areas, causing warping, localized gaps, or uneven stress in other areas. When multiple pressure plates 25 jointly clamp the clamping reference surface 15 of the part 11 from different directions, the clamping force forms a mutually coordinating distribution in the circumferential direction, resulting in a more stable fit between the part 11 and the supporting surface. For combustion chamber casing-type parts 11 with multiple lugs 12 and bosses 13 distributed on the outer wall, this multi-point circumferential clamping method not only helps maintain overall clamping stability but also provides more consistent overall boundary conditions for subsequent machining positions, thus allowing different parts to exhibit more similar stress states during machining.

[0048] In the actual clamping process, part 11 first comes into contact with the support surface via the mounting reference surface 14, and is positioned and oriented by the central positioning mechanism 22 and the angular positioning structure. Then, multiple pressure plates 25 press against the clamping reference surface 15. The pressing action of the pressure plates 25 is not to replace the positioning function, but rather to apply a holding force to part 11 after the existing positioning relationship is established, ensuring that part 11 remains in its predetermined position and orientation. Thus, the central positioning mechanism 22 and the angular positioning structure determine "where part 11 is," while the pressure plates 25 maintain part 11 in that position. Their clear division of labor and mutual cooperation avoid the problem of unstable positioning caused by relying solely on clamping force, and also prevent the problem of part 11 loosening during processing due to a lack of stable clamping while only having positioning.

[0049] The circumferential distribution of multiple pressure plates 25 is also directly related to the machine tool's machining adaptability. During the design phase, the fixture 2 has provided installation space for the machine tool clamping fixture 2 by distributing multiple extension plates 212 circumferentially and creating reserved positions 26 between adjacent extension plates 212. As the main actuator of the clamping mechanism, the pressure plates 25 need to be coordinated with the overall installation relationship of the fixture 2, the machine tool worktable space, and the machining path of the outer wall of the part 11. By arranging multiple pressure plates 25 circumferentially, the clamping points can be reasonably staggered spatially from the center positioning point, the angular positioning point, and the reinforcement points of each lug 12 to be machined. This ensures that the clamping action covers the clamping reference surface 15 of the part 11, avoids interference with the center positioning mechanism 22, the angular positioning structure, and the auxiliary support mechanism 24, and also helps to leave necessary space for the tool to enter the machining area.

[0050] In a specific implementation scenario, the part 11 to be processed is a combustion chamber casing. This combustion chamber casing has a maximum rotation diameter of 600mm and a height of 380mm, with 7 lugs 12 and 12 bosses 13 distributed on its outer wall. Considering the large size, thin wall thickness, and relatively weak rigidity of some of the lugs 12, the base mechanism 21 is formed by a disc 211 and multiple extension plates 212. The disc 211 is 600mm in size and 40mm thick, and 12 extension plates 212, each 180mm × 10mm × 10mm, are arranged circumferentially around the disc 211. The multiple extension plates 212 can be evenly distributed along the circumference of the disc 211, or arranged according to the actual needs of the structure to be processed and the machine tool installation space. Each extension plate 212 has a locating key at its bottom, and a locating groove is provided on the disc 211 to mate with the locating key. The locating key is fixed in the locating groove by a threaded connection, thereby allowing the extension plate 212 to be mounted on the disc 211. The upper end faces of the multiple extension plates 212 together form a support surface for the mounting reference surface 14 that supports the part 11. The positioning accuracy of the fixture 2 is 0.01 mm, and the flatness / installation accuracy of the support surface is 0.005 mm.

[0051] A central positioning mechanism 22 is located on the inner ring of the disc 211, and an extension plate 212 is arranged on the outer ring of the disc 211, with the two not interfering with each other in space. In this embodiment, three central positioning mechanisms 22 are arranged circumferentially along the disc 211, and the three central positioning mechanisms 22 are located on the same positioning circle. Each central positioning mechanism 22 includes a stepped plate 221 and a positioning pin 222. A positioning key is provided at the bottom of the stepped plate 221, and a positioning groove is provided on the disc 211 to cooperate with the positioning key. The positioning key is fixed in the positioning groove by a threaded connection, so that the stepped plate 221 is installed on the disc 211, and the positioning pin 222 is installed on the stepped plate 221. The positioning pins 222 of the three central positioning mechanisms 22 respectively cooperate with the inner peripheral wall of the positioning inner hole 16 of the combustion chamber casing, so that the center of the positioning circle coincides with the center of the positioning inner hole 16, thereby achieving central positioning. An angular positioning structure is mounted on one of the extension plates 212 and engages with the inner peripheral wall of the angular hole 17 of part 11 to restrict the rotation of part 11 around the center of the positioning inner hole 16, thereby achieving angular positioning. In this embodiment, the angular positioning structure includes a mounting groove on the extension plate 212 and an angular pin 23 installed in the mounting groove. The angular pin 23 engages with the inner peripheral wall of the angular hole 17 (Φ5.5 hole) to achieve angular positioning. This establishes a central reference and an angular reference for part 11, ensuring the stability of the position and orientation of part 11 after clamping.

[0052] Seven auxiliary support mechanisms 24 are respectively mounted on seven extension plates 212, and each corresponds one-to-one with one of the seven lugs 12 to be processed. Each auxiliary support mechanism 24 includes a support 241, a V-shaped support member 242, a connecting plate 243, and a lateral limiting member 244. A positioning key is provided at the bottom of the support 241, and a positioning groove that mates with the positioning key is provided at the top of the extension plate 212. The positioning key is fixed in the positioning groove by a threaded connection, thereby allowing the support 241 to be mounted on the extension plate 212. The V-shaped support member 242 is mounted on the top of the support 241. A positioning key is provided at the bottom of the V-shaped support member 242, and a positioning groove that mates with the positioning key is provided at the top of the support 241. The positioning key is fixed in the positioning groove by a threaded connection, thereby allowing the V-shaped support member 242 to be mounted on the top of the support 241. The connecting plate 243 is mounted on both sides of the support 241, and the lateral limiting member 244 is mounted on the connecting plate 243 and is movably arranged along the width direction of the lug 12 to be processed. In this implementation scenario, the lateral limiting member 244 is a knurled screw. The V-shaped support member 242 is used to support the bottom of the corresponding lug 12 to be processed, and the lateral limiting member 244 is used to clamp the two sides of the corresponding lug 12 to be processed and form a lateral limit. In this way, each lug 12 to be processed can obtain corresponding local support and limitation before processing, which helps to reduce vibration and lateral displacement during processing.

[0053] The clamping mechanism includes pressure plates 25 mounted on the remaining five extension plates 212, which are connected by threads. During clamping, the mounting reference surface 14 of the combustion chamber casing is first aligned with the support surface. Then, the three center positioning mechanisms 22 engage with the inner circumferential wall of the positioning inner hole 16 to achieve center positioning, and the angular positioning structure engages with the inner circumferential wall of the angular hole 17 of the part 11 to achieve angular positioning. Subsequently, the auxiliary support mechanisms 24 are adjusted so that the V-shaped support 242 supports the bottom of the corresponding lug 12 to be processed, and the lateral limiting members 244 clamp the two sides of the corresponding lug 12 to be processed, forming a lateral limiting relationship. Finally, by tightening the pressure plates 25, the pressure plates 25 apply a clamping action to the clamping reference surface 15 on the outer periphery of the mounting reference surface 14 of the part 11, thus stably fixing the combustion chamber casing on the fixture 2.

[0054] After clamping, fixture 2 is fixed on the machine tool worktable, and a dial indicator is used to calibrate the relative relationship between the clamping datum determined by the positioning inner hole 16, the angular hole 17, and the mounting datum surface 14 and the machine tool datum. After calibration, the structure to be machined on the outer wall of the combustion chamber casing can be machined, including 7 lugs 12 to be machined, 12 bosses 13 to be machined, and the threads on the lugs 12 and bosses 13, ensuring the dimension from the bosses 13 to the center of part 11, and ensuring the dimension from the end face of the lugs 12 to the center of part 11 and the perpendicularity of the end face of the lugs 12. Through the above arrangement and clamping method, the base mechanism 21 provides overall support, the center positioning mechanism 22 and the angular positioning structure ensure the clamping accuracy of part 11, the auxiliary support mechanism 24 ensures the local stability of the lugs 12 to be machined, and the clamping mechanism ensures the overall fixed state of part 11, thereby meeting the requirements for overall stability, positioning accuracy, and local rigidity during the machining of the combustion chamber casing.

[0055] Another aspect of this application provides a method for machining and clamping a thin-walled weldable part 11, comprising: determining the size of a disk 211, the number and arrangement of extension plates 212 according to the maximum rotation diameter, height and distribution of the structure to be machined on the outer wall of the part 11; fixing multiple extension plates 212 circumferentially on the disk 211 to form a base mechanism 21; and forming a support surface for supporting the mounting reference surface 14 of the part 11 by the upper end surface of the multiple extension plates 212.

[0056] Subsequently, the central positioning mechanism 22, the angular positioning structure, the auxiliary support mechanism 24, and the clamping mechanism are installed on the base mechanism 21 to form the clamp 2. Multiple central positioning mechanisms 22 are arranged circumferentially around the disk 211 and located on the same positioning circle. Each central positioning mechanism 22 engages with the inner circumferential wall of the positioning inner hole 16 of the part 11, aligning the center of the positioning circle with the center of the positioning inner hole 16 of the part 11, thus achieving central positioning. The angular positioning structure is mounted on one of the extension plates and engages with the inner circumferential wall of the angular hole of the part to achieve angular positioning. The auxiliary support mechanism is mounted on the extension plate and corresponds to the outer wall of the part. The lugs to be processed in the processing structure are arranged, and the clamping mechanism is set on the extension plate and used to press against the clamping reference surface of the part; thereby achieving center positioning; the angular positioning structure is set on one of the extension plates 212 and is used to cooperate with the inner peripheral wall of the angular hole 17 of the part 11 to achieve angular positioning; the auxiliary support mechanism 24 is set on the extension plate 212 and corresponds to the arrangement of the lugs 12 to be processed in the processing structure of the outer wall of the part 11; the clamping mechanism is set on the extension plate 212 and is used to press against the clamping reference surface 15 of the part 11.

[0057] During clamping, the mounting reference surface 14 of part 11 is aligned with the support surface. The positioning inner hole 16 of part 11 cooperates with the center positioning mechanism 22 to achieve center positioning, and the angular hole 17 of part 11 cooperates with the angular positioning structure to achieve angular positioning. The clamping mechanism presses against the clamping reference surface 15 of part 11. Then, each auxiliary support mechanism 24 is adjusted so that the V-shaped support 242 in each auxiliary support mechanism 24 cooperates with the corresponding lug 12 to be processed to form auxiliary support, and the lateral limiting member 244 clamps the two sides of the corresponding lug 12 to be processed and forms lateral limiting to restrict the lateral displacement of the lug 12 to be processed during the processing.

[0058] After completing the above clamping, fix fixture 2 on the machine tool worktable, and correct the relative relationship between the clamping datum determined by the positioning inner hole 16, angular hole 17, and mounting datum surface 14 of part 11 and the machine tool datum. Then, process the outer wall structure of part 11. This method can balance the overall clamping stability of part 11 and the processing stability of the local lug 12 in the same clamping, thereby improving the dimensional and positional accuracy of the outer wall structure of part 11.

[0059] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A fixture for clamping and machining thin-walled welded parts, characterized in that, It includes a base mechanism, a central positioning mechanism, an angular positioning structure, an auxiliary support mechanism, and a clamping mechanism; The base mechanism includes a disk and multiple extension plates fixedly mounted along the circumference of the disk, the upper end surfaces of the multiple extension plates forming a support surface for supporting the mounting reference surface of the parts; There are multiple center positioning mechanisms, which are spaced apart along the circumference of the disk and located on the same positioning circle. Each of the multiple center positioning mechanisms is used to cooperate with the inner circumferential wall of the positioning inner hole of the part, so that the center of the positioning circle coincides with the center of the positioning inner hole of the part, thereby achieving center positioning. An angular positioning structure is set on one of the extension plates and is used to mate with the inner peripheral wall of the angular hole of the part to restrict the rotation of the part around the center of the positioning inner hole of the part, thereby achieving angular positioning. The auxiliary support mechanism is installed on the extension plate and is arranged to correspond to each lug to be processed in the part. Each auxiliary support mechanism includes a support installed on the extension plate, a V-shaped support installed on the support, and lateral limiting members installed on both sides of the support. The V-shaped support is used to support the bottom of the corresponding lug to be processed, and the lateral limiting members are used to clamp the two sides of the corresponding lug to be processed. The clamping mechanism is mounted on the extension plate and is used to press against the clamping reference surface on the outer periphery of the part mounting reference surface.

2. The clamp according to claim 1, characterized in that, Multiple extension plates are distributed circumferentially along the disk, and reserved positions for machine tool clamping fixtures are formed between adjacent extension plates.

3. The clamp according to claim 1 or 2, characterized in that, Each center positioning mechanism includes a step plate and a positioning pin. The step plate is mounted on a disc, and the positioning pin is mounted on the step plate. The positioning pins of multiple center positioning mechanisms are located on the same positioning circle and respectively cooperate with the inner peripheral wall of the positioning inner hole of the part to achieve center positioning.

4. The clamp according to claim 1 or 2, characterized in that, The angular positioning structure includes a mounting groove on one of the extension plates and an angular pin installed in the mounting groove. The angular pin is used to engage with the inner peripheral wall of the angular hole of the part to achieve angular positioning.

5. The clamp according to claim 1 or 2, characterized in that, The V-shaped support is mounted radially on the top of the support to accommodate lugs of varying degrees of protrusion.

6. The clamp according to claim 1 or 2, characterized in that, The lateral limiting component is a knurled screw.

7. The clamp according to claim 1 or 2, characterized in that, The auxiliary support mechanism also includes connecting plates installed on both sides of the support. Lateral limiting members are movably installed on the connecting plates along the width direction of the lug to be processed, so as to accommodate lugs of different widths to be processed.

8. The clamp according to claim 1 or 2, characterized in that, The number of auxiliary support mechanisms corresponds to the number of lugs to be processed, with one auxiliary support mechanism provided for each lug to be processed. The support heights of each auxiliary support mechanism are different to correspond to the lugs to be processed at different height positions.

9. The clamp according to claim 1 or 2, characterized in that, The clamping mechanism includes multiple pressure plates distributed along the circumference of the part, which are used to press against the clamping reference surface of the part from different directions.

10. A method for machining and clamping thin-walled welded parts, characterized in that, include: Based on the maximum rotation diameter and height of the part, as well as the distribution of the structure to be processed on the outer wall of the part, determine the size of the disk, the number and arrangement of the extension plates, and fix multiple extension plates circumferentially on the disk to form a base mechanism. The upper end surfaces of the multiple extension plates form a support surface for supporting the mounting reference surface of the part. A fixture is formed by mounting a central positioning mechanism, an angular positioning structure, an auxiliary support mechanism, and a clamping mechanism on a base mechanism. The central positioning mechanism consists of multiple mechanisms, which are spaced apart along the circumference of the disc and located on the same positioning circle. Each of the multiple central positioning mechanisms is used to cooperate with the inner circumferential wall of the positioning inner hole of the part, so that the center of the positioning circle coincides with the center of the positioning inner hole of the part, thereby achieving central positioning. The angular positioning structure is set on one of the extension plates and is used to cooperate with the inner circumferential wall of the angular hole of the part to achieve angular positioning. The auxiliary support mechanism is set on the extension plate and is arranged corresponding to the lugs to be processed in the structure to be processed on the outer wall of the part. The clamping mechanism is set on the extension plate and is used to press against the clamping reference surface of the part. The part is clamped on the fixture so that the mounting reference surface of the part is in contact with the support surface. The positioning inner hole of the part cooperates with the center positioning mechanism to achieve center positioning. The corner hole of the part cooperates with the corner positioning structure to achieve corner positioning. The clamping reference surface of the part is pressed against by the clamping mechanism. Adjust each auxiliary support mechanism so that the V-shaped support in each auxiliary support mechanism cooperates with the corresponding lug to be processed to form an auxiliary support, and the lateral limiting component cooperates with both sides of the corresponding lug to be processed to limit the lateral displacement of the lug to be processed during the processing. After fixing the fixture on the machine tool worktable and correcting the relative relationship between the clamping datum determined by the part's positioning inner hole, angular hole and mounting datum surface and the machine tool datum, the outer wall structure to be machined is machined.

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