Flexible fixture for machining thin-walled porous honeycomb structures and method of clamping thereof

Abstract

The present application provides a flexible clamp for machining thin-walled porous honeycomb structure and a clamping method thereof, comprising a clamp base, a clamping assembly and a pressing driving mechanism. The clamp base is provided with a guide mounting hole, and the clamping assembly is axially movable and extends into the honeycomb cell. The clamping assembly comprises a connecting piece, an upper force applying piece, a lower force applying piece and an elastic body. The pressing driving mechanism drives the connecting piece to move axially, so that the upper force applying piece moves towards the lower force applying piece and compresses the elastic body. After the elastic body expands radially, the flexible clamping is formed with the honeycomb cell hole wall. By adjusting the compression amount of the elastic body, the clamping force can be controlled, the flexible, controllable and residue-free clamping of the honeycomb structure is realized, and the damage to the honeycomb cell hole wall is reduced.

Description

Technical Field

[0001] This invention belongs to the field of honeycomb structure processing technology, specifically relating to a flexible fixture and clamping method for machining thin-walled porous honeycomb structural parts. Background Technology

[0002] In recent years, honeycomb structures have been widely used in aerospace, transportation, and other fields due to their lightweight, high strength, and excellent energy absorption properties. Among them, titanium alloy honeycomb structures, with their advantages of low density, high specific strength, corrosion resistance, and high temperature resistance, are used as core materials for wall panels in the aerospace industry. However, honeycomb structures themselves are characterized by thin walls, numerous pores, low in-plane stiffness, and weak local support. During milling, the cell walls are prone to deformation, collapse, and vibration instability. Furthermore, TC4 titanium alloy is a typical difficult-to-machine material, with high cutting forces, high cutting temperatures, and a significant tendency for work hardening, further exacerbating defects such as burrs, tearing, weld breakage, and cell deformation during honeycomb structure machining. Therefore, TC4 titanium alloy honeycomb structures face challenges in high-speed milling, including clamping difficulties, poor cutting stability, and difficulty in controlling machining defects.

[0003] Existing technologies such as adhesive clamping, electromagnetic clamping, vacuum adsorption clamping, and filling clamping can improve the stability of honeycomb processing, but they still have problems such as complex processes, difficult cleaning, residual pollution, difficulty in controlling adsorption force, insufficient adaptability to complex contours, and high cost.

[0004] In existing technologies, adhesive clamping uses double-sided adhesive or polyethylene glycol as an adhesive medium to bond the honeycomb core to the tray for clamping. This method has advantages such as simple operation and low cost. However, due to the thin wall thickness of the honeycomb core, the area that can form an effective bond is small, resulting in limited adhesive force. During processing, the honeycomb core is prone to detachment or displacement, which can cause damage to the workpiece or even scrap it. Furthermore, cleaning adhesive residue is difficult after processing. Adhesive clamping is mainly suitable for paper honeycomb cores and aluminum honeycomb cores with small material removal requirements.

[0005] The electromagnetic clamping method mentioned in the journal article "Research on Paper Honeycomb Clamping Method Based on Magnetic Field and Friction Principle" (2007) involves filling the honeycomb core with iron powder and applying a strong magnetic field to achieve clamping by utilizing the friction between the iron powder and the workpiece. However, this method is prone to problems such as increased cutting force, increased cutting temperature, aggravated processing vibration, and severe tool wear due to the iron powder inside the honeycomb core participating in milling during the processing. This affects the processing quality of the honeycomb core and the complex structure and high equipment cost make it difficult to promote and apply on a large scale.

[0006] In the existing technology, vacuum adsorption clamping is similar to adhesive clamping. It involves bonding a diaphragm to the honeycomb lattice and creating a vacuum between the diaphragm and the worktable to achieve clamping. This method requires high vacuum and sealing performance, making it difficult to achieve stable clamping over a long period of time. Furthermore, the operation process is quite cumbersome, and cleaning the diaphragm and adhesive residue after processing is also difficult.

[0007] In existing technologies, filler clamping is the most common and widely used clamping method. It involves filling the honeycomb core with liquid polyethylene glycol, gypsum, water, or water-based media, and then solidifying the liquid medium through manual operation, natural solidification, or cryogenic freezing to achieve clamping. This clamping method provides strong holding force, improves the in-plane rigidity of the honeycomb core lattice, and enhances machining quality. The ice-holding clamping method mentioned in the journal article "Modeling and Experimental Analysis of High-Temperature Alloy Honeycomb Core Milling Process under Ice-Holding Constraint" (2024) also has advantages such as readily available media and no chemical residue contamination. (US Patent US) The article 20150239208A1 (Composite foam materials and their preparation and application methods) mentions using soluble wax to fill the honeycomb pores. However, such clamping methods all face the same problem: the cutting heat generated during processing can easily cause polyethylene glycol and wax to melt or the ice to melt locally, which reduces the holding force and support stiffness. Moreover, the filling media such as polyethylene glycol, wax, and gypsum are difficult to clean after processing. Ice clamping also requires additional low-temperature freezing and heat preservation conditions. The clamping preparation, ice melting and drainage and drying processes are quite cumbersome. At the same time, due to poor economic efficiency and limited application scenarios, it is difficult to meet the requirements of long-term stable processing.

[0008] Patent CN201910735477.7 discloses a rod-type clamping system for honeycomb composite materials, which uses multiple positioning rods to correspond one-to-one with the honeycomb core cells to achieve positioning and support of the honeycomb structure. While this clamping method can improve the support stability of the honeycomb structure to some extent, the positioning rods and the honeycomb core cell walls have a clearance fit, and the positioning rods themselves do not apply an active radial clamping force to the honeycomb core cell walls. Therefore, during machining processes such as milling, the honeycomb structure is prone to relative displacement or intermittent contact and collision with the positioning rods under cutting forces and vibrations, making it difficult to effectively suppress vibration, collapse, and machining deformation of the honeycomb core cell walls. Furthermore, the rigid positioning rods may cause scratches, compression, or localized damage to the honeycomb core cell walls, failing to meet the requirements for low-damage and high-stability machining of thin-walled honeycomb structure components.

[0009] The existing technologies mentioned above cannot effectively solve the problems of insufficient clamping stability, difficulty in controlling holding force, complex auxiliary processes, and difficulty in cleaning after machining during high-speed milling of TC4 titanium alloy honeycomb structures. There is an urgent need to develop a special flexible fixture structure and clamping method suitable for thin-walled porous honeycomb structures. This method can improve machining stability and the rigidity of the honeycomb core surface while avoiding problems such as rigid crushing or residual contamination of the honeycomb core wall, thereby achieving low-damage, high-quality, and high-efficiency milling of TC4 titanium alloy honeycomb structures. Summary of the Invention

[0010] To address the problems of insufficient clamping stability, difficulty in controlling holding force, complex auxiliary processes, and difficult post-machining cleaning in the high-speed milling of honeycomb structural parts, existing technologies provide a flexible fixture and clamping method for machining thin-walled porous honeycomb structural parts.

[0011] To achieve the above objectives, the technical solution provided by this invention is:

[0012] A flexible fixture for machining thin-walled porous honeycomb structural components, comprising a fixture base, a clamping assembly, and a clamping drive mechanism;

[0013] The fixture base is used to support the thin-walled porous honeycomb structure component. It is provided with multiple guide mounting holes, which are arranged in an array on the fixture base and correspond one-to-one with multiple honeycomb cells of the thin-walled porous honeycomb structure component.

[0014] There are multiple clamping components, each corresponding to a plurality of guide mounting holes on the fixture base; each clamping component is axially movable in the guide mounting hole, and the clamping component includes a connector, an upper force-applying component, a lower force-applying component, and an elastic body disposed between the upper force-applying component and the lower force-applying component;

[0015] The connector passes through the upper force-applying member, the elastic body, and the lower force-applying member in sequence. One end of the connector has a limiting part that abuts against the upper end face of the upper force-applying member. The lower end face of the lower force-applying member abuts against the upper surface of the fixture base. The elastic body can extend into the honeycomb core of the thin-walled porous honeycomb structure when it is not compressed.

[0016] The other end of the connector passes through the guide mounting hole and extends out of the lower end of the clamp base;

[0017] The clamping drive mechanism is horizontally positioned below the fixture base, including a drive plate and an axial drive component detachably connected to the drive plate; one end of the connector extending out of the lower end of the fixture base is fixedly connected to the drive plate; the axial drive component passes through the drive plate and its upper end can abut against the fixture base.

[0018] The axial drive is configured to: drive and move axially upward while the clamp base is fixed, and force the drive plate to move axially downward relative to the clamp base when the axial drive abuts against the clamp base, thereby increasing the axial distance between the clamp base and the drive plate; the elastomer is capable of having a corresponding axial compression under the action of the axial distance; the elastomer has radial expansion deformation generated by the axial compression, the radial expansion deformation being used to form a clamping fit with the cell wall of the honeycomb core.

[0019] Furthermore, the connecting component is a plug bolt, comprising a bolt head, a smooth rod section, and a threaded section that are coaxially and fixedly connected in sequence; the lower end face of the bolt head abuts against the upper end face of the upper force-applying component; the smooth rod section passes through the upper force-applying component, the elastic body, and the lower force-applying component in sequence, and is installed in the guide mounting hole; the threaded section extends out of the lower end face of the clamp base and is threadedly engaged with the drive plate.

[0020] Furthermore, a clearance fit is used between the smooth section of the plug bolt and the guide mounting hole to ensure the axial movement of the plug bolt and limit the radial displacement of the clamping assembly.

[0021] Furthermore, the axial drive component is a reverse screw; the reverse screw is threadedly engaged with the drive plate, and the upper end of the reverse screw can abut against the fixture base after it moves upward axially into position, and the lower end of the reverse screw extends out of the lower end of the drive plate and is provided with an internal hexagonal hole for screwing; the reverse screw is configured to: by screwing the reverse screw, the upper end of the reverse screw abuts against the fixture base, and at the same time, the drive plate moves downward relative to the fixture base under the thread drive, the drive plate drives the connecting member to move downward, so that the upper force-applying component moves toward the lower force-applying component, and applies axial compression to the elastic body located between the upper force-applying component and the lower force-applying component.

[0022] Furthermore, there are multiple anti-screws, which are evenly spaced on the drive plate. By rotating each anti-screw in a cross or synchronous manner, the axial compression of the elastic body of each clamping component is kept consistent.

[0023] Furthermore, the fixture base includes an integrally formed limiting plate, guide plate, and base; the limiting plate is located at the upper part of the fixture base and is used to support the bottom surface of the thin-walled porous honeycomb structure; the limiting plate is provided with several limiting slots for the rod segments of the connecting member to pass through; and the lower force-applying member is embedded in the limiting slots to restrict the circumferential rotation of the clamping assembly.

[0024] The guide plate is parallel to the limiting plate and located below the limiting plate. The guide mounting holes are set on the guide plate and correspond one-to-one with the limiting slot holes.

[0025] The base is positioned parallel to the bottom of the guide plate to form the mounting reference for the fixture base.

[0026] Furthermore, the upper and lower force-applying components use rigid gaskets; the elastomer is a polyurethane block with a Shore hardness of 30A to 60A; the outer contours of the elastomer and the rigid gasket are adapted to the inner contours of the honeycomb core; the size of the rigid gasket is equal to the size of the elastomer.

[0027] Furthermore, the outer contours of the upper force-applying component, the lower force-applying component, and the elastic body are all regular hexagons; the limiting slot is a hexagonal slot that matches the outer contour of the lower force-applying component.

[0028] Furthermore, it also includes a compression adjustment component; the compression adjustment component is coaxially sleeved on the axial drive member and located below the drive plate; the compression adjustment component has a predetermined axial thickness, and the predetermined axial dimension is determined according to the maximum axial displacement actually required by the axial drive member.

[0029] The present invention also provides a flexible clamping method for thin-walled porous honeycomb structure components, which is implemented using the above-mentioned flexible clamp and includes the following steps:

[0030] The thin-walled porous honeycomb structure is placed horizontally on the fixture base, so that each clamping component extends into the corresponding honeycomb cell of the thin-walled porous honeycomb structure.

[0031] With the fixture base fixed, the axial drive component moves axially upward relative to the drive plate, so that the upper end of the axial drive component abuts against the fixture base.

[0032] Continue operating the axial drive component; since the fixture base remains fixed, the axial drive component no longer moves upward along the axial direction, forcing the drive plate to move downward relative to the fixture base, driving the connecting component connected to it to move downward synchronously, increasing the axial distance between the fixture base and the drive plate.

[0033] During the downward movement of the drive plate, the limiting part of the connector drives the upper force-applying part to move closer to the lower force-applying part, and the lower force-applying part is axially supported by the clamp base, so that the elastic body is axially compressed between the upper force-applying part and the lower force-applying part.

[0034] When the elastomer is compressed, it expands radially and forms a flexible clamping fit with the cell wall of the honeycomb core.

[0035] The advantages of this invention are:

[0036] 1. Addressing the problem that traditional rigid clamping methods easily cause crushing or scratching of the cell walls in thin-walled, porous honeycomb structures with weak local support, this invention provides a flexible clamp for machining thin-walled, porous honeycomb structures. This flexible clamp is a flexible expansion support clamp that utilizes the axial compression and radial expansion of an elastic body inserted into the honeycomb cell in the clamping assembly. This creates a flexible surface contact between the elastic body and the cell wall, generating a frictional clamping force. Because the elastic body and the cell wall are in elastic contact, the contact stress distribution is improved, reducing local stress concentration and the risk of damage to the honeycomb cell wall, thus achieving flexible clamping.

[0037] 2. To address the problems of low in-plane stiffness and easy deformation, collapse, vibration instability, and weld breakage of thin-walled porous honeycomb structures during milling, this invention uses multiple clamping components arranged in an array according to the honeycomb grid distribution. By employing a cross or synchronous driving method, the compression and clamping force at each clamping point are kept consistent, forming multi-point uniform support for the thin-walled porous honeycomb structure. This improves the in-plane stiffness and overall vibration resistance of the honeycomb grid, effectively reducing the risks of honeycomb grid deformation, burrs, tearing, and weld breakage during the milling process of thin-walled porous honeycomb structures.

[0038] 3. This invention employs an adjustable axial drive clamping mechanism. The operator can precisely set the axial compression amount according to the wall thickness, honeycomb core size, and processing load of the thin-walled porous honeycomb structure. Specifically, a compression adjustment component is arranged between the axial drive component (e.g., a counter-screw) and the drive plate to adjust the axial compression amount of the elastomer (e.g., a polyurethane block), thereby adjusting the clamping force. This avoids both insufficient clamping force causing displacement of the honeycomb structure and excessive clamping force causing damage to the honeycomb core wall, thus improving the stability, controllability, and repeatability of the clamping process.

[0039] 4. To address the issues of horizontal movement of honeycomb structural components on the fixture base and circumferential rotation of the clamping assembly during compression, which can lead to misalignment between the elastomer and the honeycomb lattice, this invention employs a fixture base where the top supports the bottom surface of the thin-walled porous honeycomb structural component for positioning. A limiting slot (e.g., a hexagonal slot) is provided on the fixture base to circumferentially limit the clamping assembly and prevent rotation. Simultaneously, the fixture base is an integral metal structure with high overall rigidity, ensuring high stability of the flexible fixture under milling loads.

[0040] 5. This invention uses a solid elastomer as the clamping medium, achieving clamping and detachment through mechanical drive, without requiring any filler materials, low-temperature environments, or adhesives. The clamping and disassembly process is simple and fast, with no chemical residue and no ice-melting or drainage steps, avoiding problems such as insufficient clamping force, difficult residue cleaning, complex devices, and poor long-term stability. It significantly improves the clamping efficiency and reusability of honeycomb structural components, meeting the requirements for long-term stable processing. Attached Figure Description

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0042] Figure 1 This is a three-dimensional structural diagram of the flexible clamp of the present invention; wherein, Figure 1 (a) is an overall assembly diagram of the clamping base, clamping assembly and clamping drive mechanism; (b) is a schematic diagram of the fit between the clamping drive mechanism and the clamping base.

[0043] Figure 2 This is a schematic diagram of the structure of the clamp base in the flexible clamp of the present invention; wherein, Figure 2 (a) is an overall schematic diagram of the fixture base; (b) is a sectional view of the fixture base; (c) is an exploded schematic diagram of the fixture base.

[0044] Figure 3 This is a schematic diagram of the clamping assembly in the flexible fixture of the present invention;

[0045] Figure 4 These are tensile test data of polyurethane materials in embodiments of the present invention and schematic diagrams of radial engineering strain under different axial compressions; wherein, Figure 4 (a) is a graph of tensile test data; (b) is a histogram of radial strain.

[0046] Figure 5 This is a diagram showing the connection relationship between the clamping assembly and the pressure driving mechanism in the flexible fixture of the present invention; wherein, Figure 5 (a) is a three-dimensional schematic diagram of the clamping assembly and the clamping drive mechanism; (b) is a vertical structural cross-sectional view of the clamping assembly and the clamping drive mechanism after assembly.

[0047] Figure 6 This is a schematic diagram illustrating the working principle of the hexagonal polyurethane blocks within the honeycomb core, before and after clamping the honeycomb structure component using the flexible clamping device of the present invention, from an uncompressed state to a radially expanded state driven by the clamping assembly and pressure drive mechanism; wherein... Figure 6 In the diagram, (a) indicates that the hexagonal polyurethane block is in an uncompressed state within the honeycomb core; (b) indicates that the hexagonal polyurethane block is in a radially expanded state within the honeycomb core.

[0048] Figure 7 This is a schematic diagram illustrating the working principle of the compression adjustment component located between the anti-rotating screw and the drive plate in the flexible clamp of the present invention; wherein, Figure 7 (a) indicates the normal compression state of the elastomer without the compression adjustment component; (b) indicates that with the compression adjustment component installed, the effective screw-in depth of the counterscrew is limited, causing the axial compression of the elastomer to be relative to... Figure 7 (a) is a decreasing state;

[0049] Figure 8 This is a schematic diagram showing the dimensions and structure of the honeycomb structure used in this embodiment of the invention; wherein, Figure 8 (a) is a three-dimensional schematic diagram of the honeycomb structure; (b) is a top view of the honeycomb structure.

[0050] Figure 9 This is an overall assembly diagram of the honeycomb structure component clamped by a flexible clamp in an embodiment of the present invention;

[0051] Figure 10 This refers to the clamping force along the horizontal direction of a single honeycomb lattice cell wall when it is clamped by the clamping assembly, calculated using finite element software in this embodiment of the invention; wherein, Figure 10 (a) is a finite element model and stress distribution diagram of flexible clamping of a single honeycomb lattice wall; (b) is a curve of the clamping force of a single honeycomb lattice wall on both sides along the horizontal direction as a function of time, obtained by finite element simulation.

[0052] Figure 11 This embodiment uses a custom-made, non-standard honeycomb milling tool. During milling operations in both climb milling and conventional milling, the average cutting forces and resultant forces in the X, Y, and Z directions are measured using a force gauge. Figure 11 (a) shows the average cutting force in the X, Y, and Z directions under climb milling conditions; (b) shows the average cutting force in the X, Y, and Z directions under conventional milling conditions; and (c) shows the comparison of the average resultant force under climb milling and conventional milling conditions.

[0053] Figure 12 These are comparison images of surface defect morphology after machining TC4 titanium alloy honeycomb structures using the flexible fixture of this invention and traditional clamping methods; among them, Figure 12 (a) is a schematic diagram of clamping using a conventional fixture; (b) is a schematic diagram of clamping using the flexible fixture of the present invention; (c) is a surface morphology diagram of the machined surface after clamping using a conventional fixture; and (d) is a surface morphology diagram of the machined surface after clamping using the flexible fixture of the present invention.

[0054] Reference numerals: 1-Clamp base; 101-Limiting plate; 102-Guide plate; 103-Base; 2-Clamping assembly; 201-Plug bolt; 202-Upper washer; 203-Lower washer; 204-Elastomer; 3-Pressure driving mechanism; 301-Drive plate; 302-Reverse screw; 4-Thin-walled porous honeycomb structure; 5-Compression adjustment assembly. Detailed Implementation

[0055] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0056] Reference Figure 1 This embodiment provides a flexible fixture for machining thin-walled porous honeycomb structures. The fixture includes a fixture base 1, clamping components 2, and a clamping drive mechanism 3. The fixture base 1 supports the thin-walled porous honeycomb structure and provides a mounting, guiding, limiting, and supporting foundation for the clamping components. It has multiple guide mounting holes corresponding one-to-one with multiple honeycomb cells in the thin-walled porous honeycomb structure. Multiple clamping components 2 are provided, each corresponding to one of the guide mounting holes on the fixture base. Each clamping component includes a connector, an upper force-applying component, a lower force-applying component, and an elastic body disposed between the upper and lower force-applying components. The clamping components are axially movable within the corresponding guide mounting holes, allowing them to extend into the honeycomb cells of the thin-walled porous honeycomb structure through the guide mounting holes. Flexible clamping of the honeycomb cells is achieved through the elastic deformation of the elastic body. The clamping drive mechanism 3 is located below the clamp base 1 and connected to multiple clamping components, including a drive plate 301 and an axial drive component. The two drive the clamping components 2 to generate axial displacement, converting the axial compression of the elastomer into a controllable radial expansion, thereby achieving multi-point uniform flexible clamping of the entire thin-walled porous honeycomb structure.

[0057] Reference Figure 2 The fixture base 1 is located at the top of the entire flexible fixture. The fixture base 1 is a one-piece metal structure, functionally divided into a limiting plate 101, a guide plate 102, and a base 103 arranged sequentially from top to bottom. The limiting plate 101, located at the top of the fixture base 1, supports the bottom surface of the thin-walled porous honeycomb structure. The limiting plate has multiple hexagonal limiting slots, the shape of which matches the outer contour of the lower pad 203 in the clamping assembly 2. When the clamping assembly 2 is assembled in the fixture base 1, the lower pad 203 is embedded in the corresponding hexagonal limiting slot, achieving circumferential limiting of the clamping assembly 2 and preventing circumferential rotation of the clamping assembly 2 during axial compression. If the lower pad 203 rotates, the correspondence between the outer contour of the elastic body 204 and the honeycomb lattice will be misaligned, causing the elastic body 204 to expand and fail to form a uniform surface contact with the honeycomb lattice wall. The hexagonal limiting slot is designed to constrain the rotational degree of freedom while ensuring the axial movement degree of freedom, so that the clamping assembly 2 can only move along the axial direction during compression.

[0058] The guide plate 102 is parallel to the limiting plate and located below it. Multiple guide mounting holes are provided on the guide plate. These guide mounting holes are circular and extend along the thickness direction of the guide plate 102. Each guide mounting hole corresponds vertically to each honeycomb lattice of the thin-walled porous honeycomb structure and is clearance-fitted with the smooth section of the clamping bolt 201 in the clamping assembly 2. This clearance fit ensures smooth axial movement of the clamping bolt 201 while limiting significant radial displacement of the clamping bolt 201 under milling loads. The preferred tolerance between the guide mounting holes and the smooth section of the clamping bolt 201 is H7 / g6. When a transverse cutting force is generated during milling, the hole wall of the guide mounting hole provides radial support to the smooth section of the clamping bolt 201, preventing bending deformation of the clamping bolt 201 or radial movement of the clamping assembly 2, and ensuring that the axis of each clamping assembly 2 coincides with the axis of the corresponding honeycomb lattice. The number and distribution of the guide mounting holes are determined based on the number and arrangement of the honeycomb core cells in the thin-walled porous honeycomb structure, and the two correspond one-to-one.

[0059] The base 103 is positioned below the guide plate 102, with a flat bottom surface, for horizontally mounting the flexible fixture onto the machine tool work platform. The base improves the overall rigidity of the fixture base and provides a stable mounting reference, preventing uneven movement of the drive plate 301 or uneven localized force due to unevenness of the bottom surface of the fixture base 1 during adjustment of the clamping drive mechanism 3. A positioning keyway can be provided on the lower surface of the base 103 for engagement with the T-slots on the machine tool worktable, enabling rapid positioning and fixation of the flexible fixture on the machine tool.

[0060] In this embodiment, the base 103 is a frame-type support structure with a central open space, located below the guide plate 102. It supports the limiting plate 101 and the guide plate 102, forming the bottom mounting reference for the flexible fixture. Specifically, a central open space is formed in the base 103. The lower parts of the drive plate 301 and the anti-screw 302 in the clamping drive mechanism 3 are located within this open space and can perform corresponding axial movements within it. The lower end surface of the base 103 is lower than the lowest point of the drive plate 301 and the anti-screw 302, ensuring that neither the drive plate 301 nor the anti-screw 302 protrudes from the lower mounting reference surface of the base 103. Therefore, when the flexible fixture is installed on the machine tool table, a stable support and positioning relationship is formed between the lower end surface of the base 103 and the machine tool table, preventing interference between the drive plate 301 and the anti-screw 302 and the machine tool table. The base 103 provides a reference for the installation of the clamps, while also providing necessary clearance for the movement of the drive plate 301 and the anti-screw 302.

[0061] Reference Figure 3Multiple clamping components 2 are respectively disposed in corresponding guide mounting holes and can move axially along the guide mounting holes. The connecting parts in the clamping components can be structural components that can achieve axial connection and limitation, such as stepped shafts and tie rods. The upper force-applying parts and the lower force-applying parts can be rigid components such as hard plastic gaskets or metal gaskets. In this embodiment, the connecting parts are preferably plug bolts 201, and the upper force-applying parts and the lower force-applying parts are preferably metal gaskets, defined as upper gasket 202 and lower gasket 203, respectively. The elastic body 204 is sleeved on the plug bolt and located between the upper gasket 202 and the lower gasket 203. The plug bolt 201 passes through the upper gasket 202, the elastic body 204 and the lower gasket 203 in sequence. The upper end of the plug bolt 201 is provided with a bolt head, which is pressed onto the upper surface of the upper gasket 202. The lower end of the plug bolt 201 passes through the guide mounting hole and is connected to the clamping drive mechanism 3. The lower end of the plug bolt 201 is provided with an external thread for fixed connection with the threaded hole on the drive plate 301 in the clamping drive mechanism 3. The bolt head of the plug bolt 201 is a smooth section between the bolt head and the threaded section. The smooth section passes through the upper washer 202, the elastic body 204, the lower washer 203 and the clamp base, and does not restrict the radial expansion of the elastic body 204. The elastic body 204 can freely expand in the radial direction when axially compressed.

[0062] The outer contours of the upper washer 202 and the lower washer 203 are both hexagonal, which matches the cross-sectional shape of the honeycomb core. The upper washer 202 is used to uniformly transmit the axial tensile force on the plug bolt 201 to the upper end face of the elastic body 204, and the lower washer 203 is used to uniformly transmit the axial thrust on the limiting plate 101 to the lower end face of the elastic body 204.

[0063] The elastomer 204 is a block structure made of a polymer elastic material, and its outer contour shape is adapted to the cross-sectional shape of the honeycomb lattice. In this embodiment, the cross-sectional shape of the honeycomb lattice is a regular hexagon, and the outer contour shape of the elastomer 204 is also a regular hexagon. The size of the elastomer is matched according to the size of the honeycomb lattice, so that there is an assembly gap between the elastomer and the honeycomb lattice wall in the uncompressed state, and that it can generate radial expansion after axial compression to contact the honeycomb lattice wall. Specifically, in the uncompressed state, the outer dimensions of the elastomer 204 are slightly smaller than the inner cavity size of the honeycomb lattice, allowing it to be smoothly inserted into the honeycomb lattice without jamming.

[0064] The elastomer 204 is disposed between the upper gasket 202 and the lower gasket 203. When the upper gasket 202 and the lower gasket 203 move towards each other, the elastomer 204 is first compressed, and its axial height decreases. Based on the near-incompressible volume retention characteristics of the polymer elastic material of the elastomer, the decrease in axial dimension will inevitably lead to an increase in radial dimension, that is, radial expansion occurs. When the radial dimension of the elastomer 204 increases to the point of contact with the cell wall of the honeycomb lattice, further increase will generate radial positive pressure. The elastomer and the cell wall of the honeycomb lattice form a radial interference. This positive pressure is converted into a clamping force on the cell wall of the honeycomb lattice through the friction between the outer wall of the elastomer 204 and the cell wall.

[0065] In this embodiment, the material of the elastomer 204 is preferably polyurethane rubber, with a Shore hardness preferably between 30A and 60A, specifically polyurethane rubber with a Shore hardness of 40A. Polyurethane rubber has excellent wear resistance and elastic recovery properties, maintaining good performance stability during repeated compression and rebound. The elastomer 204 can also be made of elastic materials such as silicone rubber, nitrile rubber, and neoprene rubber. The width of the opposite sides of the elastomer 204 can be set to 70% to 90% of the opposite side size of the corresponding honeycomb core, to ensure smooth insertion into the honeycomb core in the uncompressed state and to form flexible contact with the honeycomb cell wall through radial expansion after axial compression; the height of the elastomer can be determined according to the required radial expansion and axial compression. In this embodiment, for a honeycomb core with an opposite side size of 11.2mm, the width of the opposite sides of the elastomer 204 is designed to be 9mm, and the height is designed to be 6mm.

[0066] To further illustrate the deformation characteristics of elastomer 204 under axial compression and radial expansion, mechanical property tests and radial deformation analyses were performed on the polyurethane material used in this embodiment. The results are as follows: Figure 4 As shown. By Figure 4 As can be seen in (a), the stress in the polyurethane material continuously increases with increasing strain, indicating that the material can maintain continuous load-bearing capacity under large deformation conditions, making it suitable as a flexible deformation element in clamping assemblies. Figure 4 As can be seen in (b), the radial engineering strain of the elastomer increases nonlinearly with the increase of axial compression. When the axial compression is 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm, the radial engineering strain is approximately 9.54%, 22.47%, 41.42%, 73.21%, and 144.55%, respectively. Therefore, by adjusting the axial compression of the elastomer 204, its radial expansion can be effectively controlled, and the contact state and clamping degree between the elastomer and the cell wall can be further adjusted.

[0067] The elastic body 204 and the clamping bolt 201 are detachably connected. The elastic body 204 has a through hole at its center, through which the smooth section of the clamping bolt 201 passes. A clearance fit is used between the elastic body 204 and the clamping bolt 201, allowing the elastic body 204 to be freely removed from the clamping bolt 201. In this embodiment, a diameter assembly clearance of 0.2–0.5 mm is preferably used between the two. When the elastic body 204 exhibits permanent compression deformation, surface cracks, decreased elastic recovery capacity, reduced radial expansion, or decreased clamping effect, it can be removed from the clamping bolt 201 for individual replacement, improving the maintenance convenience and reusability of the fixture. The replacement cycle of the elastic body is not fixed and can be determined based on the fixture's operating conditions, clamping frequency, processing environment, and the actual condition of the elastic body.

[0068] Reference Figure 1 and Figure 5 The clamping drive mechanism 3 is located below the fixture base 1 and connected to multiple clamping assemblies 2, used to drive the clamping assemblies 2 to generate axial displacement. The clamping drive mechanism 3 includes a drive plate 301 and multiple axial drive components, preferably anti-rotating screws 302. The drive plate 301 is a flat plate structure located below the base 103 in the fixture base. The drive plate 301 has multiple threaded holes, the positions of which correspond one-to-one with the positions of the guide mounting holes on the fixture base 1. The lower ends of the plug bolts 201 of each clamping assembly 2 pass through the guide mounting holes and are screwed into the corresponding threaded holes on the drive plate 301, realizing the fixed connection between the plug bolts 201 and the drive plate 301. When the drive plate 301 moves axially, it drives all the plug bolts 201 to move synchronously.

[0069] The anti-screw 302 is disposed on the drive plate 301. Specifically, the drive plate 301 has multiple threaded through holes, and each anti-screw 302 passes through the corresponding threaded through hole. The upper end of the anti-screw 302 extends out of the upper surface of the drive plate 301 and can abut against the lower surface of the guide plate 102 of the clamp base 1 after it moves upward into position. The lower end of the anti-screw 302 extends out of the lower surface of the drive plate 301, and the lower end face of the anti-screw 302 is provided with an internal hexagonal hole for screwing. There are multiple anti-screws 302, which are evenly distributed on the drive plate 301, so that when the drive plate 301 is driven by the anti-screws 302, the force points are evenly distributed, and the drive plate 301 moves downward as a whole without tilting. If only a single anti-screw 302 is provided or the force points are not evenly distributed, the drive plate 301 may be deflected, resulting in inconsistent displacement of each clamping component 2 and uneven distribution of clamping force. The uniform distribution design of the anti-screws in this invention ensures the consistency of each clamping component 2. In this embodiment, eight anti-screws are arranged. By adjusting the screwing depth of each anti-screw 302 in a cross or synchronous manner, the axial clearance between the drive plate 301 and the fixture base 1 is increased. It should be noted that, through actual processing verification, the processing vibration force of the thin-walled porous honeycomb structure after clamping is much smaller than the thread locking force between the anti-screw 302 and the drive plate 301. Therefore, the thin-walled porous honeycomb structure can be processed after the anti-screw 302 is screwed into place, without the need for additional locking components to lock the anti-screw 302.

[0070] In its uncompressed state, the elastomer 204 has dimensions smaller than the inner cavity of the honeycomb core (the outer diameter of the elastomer is 2-3 mm smaller than the inner diameter of the honeycomb core), allowing the elastomer to be smoothly inserted into the honeycomb core without jamming. For example... Figure 6 As shown in (a), when the anti-screw 302 is turned upwards, the upper end of the anti-screw 302 applies a supporting force to the lower surface of the clamp base 1, causing the drive plate 301 to move downwards relative to the clamp base 1. The drive plate 301 drives the upper washer 202 to move downwards via the plug bolt 201, and the lower washer 203 is axially supported by the clamp base (which remains fixed), reducing the axial distance between the upper washer 202 and the lower washer 203, thereby applying axial compression to the elastic body 204 located between them. Figure 6 As shown in (b), when the upper pad moves downward to compress the elastomer 204, the lower pad is axially supported by the clamp base, which reduces the axial distance between the upper and lower pads. The elastomer 204 expands radially, and the outer wall of the elastomer forms a flexible contact with the cell wall of the honeycomb core and generates a radial contact force.

[0071] The counterscrew 302 has an adjustable screw-in depth. By adjusting its axial displacement, the axial compression of the elastomer 204 can be changed, thereby adjusting the radial expansion of the elastomer 204 and its clamping effect with the honeycomb lattice wall. The operator can adjust the axial compression of the elastomer 204 according to the wall thickness, honeycomb lattice size, and processing load of the thin-walled porous honeycomb structure to obtain a clamping degree adapted to the processing conditions. This reduces the risk of workpiece displacement or vibration due to insufficient clamping and avoids damage to the honeycomb lattice wall due to excessive compression.

[0072] like Figure 7 As shown, the clamping drive mechanism 3 adjusts the upward axial displacement of the anti-screw 302 via the compression adjustment component 5. Specifically, the compression adjustment component 5 is sleeved on the anti-screw 302 and located below the drive plate. It limits the effective screwing amount of the anti-screw 302 relative to the drive plate 301, thereby limiting the axial displacement of the drive plate 301 relative to the fixture base 1 to avoid excessive compression of the elastomer, which could cause pressure damage to the cell walls of the honeycomb lattice. In batch processing, the operator does not need to repeatedly adjust the effective screwing amount of the anti-screw 302 each time it is clamped. Simply screwing the anti-screw 302 to the limit position will achieve a consistent compression amount, improving the uniformity and consistency of clamping.

[0073] Specifically, the compression adjustment component 5 is a limiting member with a predetermined axial dimension sleeved on the anti-screw 302. The axial dimension of the limiting member is determined according to the maximum axial displacement actually required by the anti-screw. The limiting member can be a limiting washer, a limiting sleeve, or other equivalent structure that can form an axial stop. In this embodiment, the limiting member is sleeved on the threaded section of the anti-screw 302 and is located between the lower surface of the drive plate 301 and the head of the anti-screw 302, occupying part of the threaded stroke of the anti-screw, and is used to limit the maximum axial displacement of the anti-screw 302 relative to the drive plate 301. When the anti-screw 302 is screwed upwards, its head gradually approaches the lower surface of the drive plate 301. Under the action of the screw, the limiting component is ultimately clamped between the screw head and the lower surface of the drive plate, thus forming an axial stop. At this point, the anti-screw 302 will not continue to move upwards axially. The upper end (end face of the threaded section) of the anti-screw 302 applies a supporting force to the clamp base 1, causing the drive plate 301 to move downwards relative to the clamp base. The axial distance between the drive plate and the clamp base 1 gradually increases, driving the clamping assembly 2 to axially compress the elastic body 204. When the anti-screw 302 can no longer be screwed upwards, the axial distance between the drive plate 301 and the clamp base 1 reaches a preset maximum value, and the axial compression of the elastic body 204 correspondingly reaches a preset maximum value. By selecting limiting components with different axial dimensions, different maximum axial displacements can be limited, thereby adjusting the maximum axial compression of the elastic body 204. The compression adjustment component 5 can also be a limiting block fixed to the lower surface of the drive plate 301. The limiting block limits the distance between the head of the anti-screw 302 and the lower surface of the drive plate 301, which can also limit the maximum axial displacement of the anti-screw 302 and the maximum axial compression of the elastomer 204.

[0074] The following section uses a TC4 titanium alloy honeycomb structure as an example to specifically explain the clamping method of the flexible fixture of the present invention, the method of replacing the elastomer, and the effect on improving the surface quality of the honeycomb structure.

[0075] The honeycomb structure used in the embodiment is a TC4 titanium alloy honeycomb structure, such as... Figure 8 As shown, the honeycomb core has a side dimension of 11.2 mm, a single-layer wall thickness of 0.1 mm, and a height of 30 mm. This embodiment describes a flexible clamping method for machining thin-walled porous honeycomb structures, comprising the following steps:

[0076] Reference Figure 9During clamping, the thin-walled porous honeycomb structure 4 to be processed is first placed on the upper surface of the limiting plate 101, so that the bottom surface of the honeycomb structure is in contact with the upper surface of the limiting plate 101. During placement, the elastic body 204 of each clamping component 2 (at this time, the elastic body is in an uncompressed state) extends into the corresponding honeycomb core cell of the honeycomb structure, ensuring that each clamping component 2 corresponds one-to-one with the honeycomb core cell. Since the outer contour dimension of the elastic body 204 in the uncompressed state is smaller than the inner cavity dimension of the honeycomb core cell, the elastic body 204 can smoothly enter the honeycomb core cell without jamming or scratching.

[0077] After the honeycomb structure is placed in place, the operator visually inspects it for gaps or warping between the bottom surface of the honeycomb structure and the upper surface of the limiting plate 101, ensuring there is no shaking. If the honeycomb structure is not level, its position should be adjusted to ensure that each elastic element 204 is correctly inserted into its corresponding honeycomb cell, preventing the honeycomb structure from tilting or the cell walls from being damaged due to the elastic element 204 getting stuck at the edge of the honeycomb cell. Only after confirming that the bottom surface of the honeycomb structure is stably attached to the upper surface of the limiting plate 101 and that the entire honeycomb structure is level should the next step be performed.

[0078] After the honeycomb structure component is placed in place and its status is confirmed, the clamping base is kept in a fixed state, and the clamping drive mechanism 3 is adjusted. In this embodiment, a torque wrench or other tools are used to tighten multiple anti-screws 302 that are threaded into the drive plate 301 in a cross-rotation manner, so that each anti-screw 302 is screwed upward along the thread direction. The upper end of the anti-screw 302 abuts against the lower surface of the guide plate 102 of the clamping base 1. Since the clamping base remains fixed, the anti-screws cannot continue to move upward along the axial direction when they continue to rotate. The threaded pair between the anti-screws and the drive plate converts the rotational motion into a downward movement of the drive plate along the axis of the anti-screws, thereby increasing the axial distance between the drive plate and the clamping base. When the drive plate 301 moves downward, it drives each of the plug bolts 201 connected to it to move downward synchronously. Each plug bolt 201 drives the upper washer 202 to move downward through its bolt head. The lower washer 203 is axially supported by the limiting plate 101 of the clamp base 1, thereby reducing the axial distance between the upper washer 202 and the lower washer 203 and applying axial compression to the elastic body 204 located between them.

[0079] Under axial compression, the elastomer 204 expands radially, forming a flexible clamping fit with the honeycomb lattice wall. When the axial compression rate of the elastomer 204 reaches approximately 35.4%, its distance between opposite sides increases from the initial 9 mm to approximately 11.2 mm, and it begins to contact the inner wall of the honeycomb lattice. With continued axial compression, the elastomer 204 is radially constrained by the honeycomb lattice wall, generating radial contact pressure at the contact interface, thus forming a stable flexible clamping. This radial contact pressure generates axial holding capacity through the friction between the outer wall of the elastomer 204 and the honeycomb lattice wall, establishing a stable flexible contact relationship between the elastomer 204 and the honeycomb lattice wall. Therefore, each clamping component can form distributed intra-cell support and friction clamping action within the honeycomb lattice, improving the clamping stability of the thin-walled porous honeycomb structure.

[0080] After clamping the thin-walled porous honeycomb structure 4 with the flexible fixture, the flexible fixture, together with the thin-walled porous honeycomb structure 4, is installed as a whole on the machine tool worktable. In this embodiment, the flexible fixture is relatively small in size, and the base 103 of the fixture base 1 can be clamped using a machine tool vise, keeping the flexible fixture fixed relative to the machine tool worktable during processing. For larger honeycomb structures and correspondingly larger flexible fixtures, a fastening method that mates with a T-slot on the machine tool worktable can also be used to fix the fixture base 1 to the machine tool worktable. The above installation method can be selected according to the actual size of the flexible fixture, the size of the honeycomb structure, and the structure of the machine tool worktable, as long as the movement of the flexible fixture relative to the machine tool worktable can be reliably restricted during processing. After the flexible fixture is installed and fixed, end milling, side milling, or other machining operations can be performed on the thin-walled porous honeycomb structure. Each clamping component 2 forms a distributed flexible support within multiple honeycomb cells of the honeycomb structure, ensuring that the honeycomb structure is reliably clamped during processing.

[0081] After processing, firstly, the fixed connection between the flexible fixture and the machine tool worktable is released. In this embodiment, the machine tool vise is released from the clamping base 1, and the flexible fixture, along with the thin-walled porous honeycomb structure, is removed from the machine tool worktable as a whole. When a T-slot fixing method is used, the flexible fixture is released from the T-slot fastening connection with the machine tool worktable, and then the flexible fixture, along with the thin-walled porous honeycomb structure 4, is removed as a whole.

[0082] Subsequently, the clamping action of the flexible fixture on the thin-walled porous honeycomb structure 4 is released. Specifically, each anti-rotating screw 302 is loosened in the reverse direction, causing the threaded pair between the anti-rotating screw 302 and the drive plate 301 to move axially downward in the opposite direction. The drive plate 301 returns to its original position relative to the fixture base 1, and the axial compression effect of the plug bolt 201 on the elastic body 204 is reduced. Under its own elastic recovery, the elastic body 204 gradually returns to its uncompressed state, its radial expansion decreases, and the flexible contact and friction clamping action between it and the honeycomb core cell wall is released. After the clamping action between each elastic body 204 and the honeycomb core cell wall is released, the thin-walled porous honeycomb structure 4 is removed upward from the fixture base 1, thus completing one complete processing and disassembly process. This disassembly process does not require the removal of the filling medium, nor does it require de-icing, drainage, or residue cleaning. The operation is simple and can improve the efficiency of repeated clamping of the honeycomb structure.

[0083] As a variation of the above embodiments, the driving method of the clamping drive mechanism 3 is not limited to manually tightening the anti-reverse screw 302. It can also adopt equivalent driving methods known in the art, such as hydraulic drive, pneumatic drive, or electric drive. For example, the anti-reverse screw 302 can be replaced with an axially extendable drive rod at the installation position corresponding to the anti-reverse screw 302. The drive rod is driven to extend axially through a hydraulic system, pneumatic system, or electric actuator, so that the upper end of the drive rod abuts against and supports the lower surface of the clamp base 1. This causes the drive plate 301 to generate axial displacement relative to the clamp base 1, and drives the clamping assembly 2 to apply axial compression to the elastic body 204. The specific structure of the hydraulic system, pneumatic system, or electric actuator and its connection method with the drive rod are all known technologies in the art. They can drive the drive rod to extend axially and provide support to the lower surface of the clamp base 1, and will not be described in detail here.

[0084] The flexible clamp and clamping method provided by this invention do not require filling the honeycomb lattice with auxiliary media such as polyethylene glycol, gypsum, water, or iron powder, nor do they require vacuum adsorption, low-temperature freezing, or subsequent de-icing and cleaning processes. This method forms a flexible expansion support inside the honeycomb lattice through the axial compression and radial expansion of the elastomer 204, achieving in-hole support and clamping of the honeycomb structure. This improves clamping stability, repeat clamping efficiency, and machining quality, and is suitable for machining thin-walled porous honeycomb structure 4.

[0085] The specific method for replacing the elastomer is as follows:

[0086] First, release the clamping state of the flexible fixture: loosen the reverse screws 302, causing the threaded pair between the reverse screws 302 and the drive plate 301 to generate opposite axial displacement. Specifically, use a tool to reverse-tighten each reverse screw 302, causing the reverse screws 302 to disengage, the drive plate 301 to return to its upward position, the axial compressive force of the plug bolts 201 on the elastic body 204 to be released, the lower washer 203 returns to its original position along with the limiting plate 101, and the elastic body 204 returns to its uncompressed state under the action of its own elastic restoring force, releasing the contact between it and the cell wall of the honeycomb core.

[0087] Subsequently, the locking bolt 201 in the clamping assembly 2, from which the elastomer 204 needs to be replaced, is unscrewed from the drive plate 301, thus disengaging the clamping assembly 2 from the drive plate 301. Specifically, a standard M3 Allen wrench (not shown in the figure) is used to unscrew the locking bolt from the threaded hole on the drive plate 301.

[0088] After the clamping bolt 201 is disengaged from the drive plate 301, the clamping assembly 2 is pulled upward along the guide mounting hole on the guide plate 102 of the clamp base 1. After removing the clamping assembly 2, the lower washer 203 is removed, and the aged or damaged elastomer 204 is removed from the clamping bolt 201. Then, a new elastomer 204 is fitted onto the clamping bolt 201, positioning it between the upper washer 202 and the lower washer 203, and the lower washer 203 is reinstalled.

[0089] After replacement, insert the reassembled clamping assembly 2 back into the corresponding guide mounting hole of the guide plate 102, so that the lower gasket 203 is embedded in the hexagonal limiting groove on the upper surface of the limiting plate 101, and ensure that the corresponding position of the clamping assembly 2 and the honeycomb core is consistent. Finally, after passing the lower end of the plug bolt 201 through the guide mounting hole, screw it back into the threaded hole on the drive plate 301, so that the clamping assembly 2 is reconnected with the clamping drive mechanism 3, thus completing the replacement of the elastomer 204.

[0090] By using the above replacement method, one or more elastic bodies 204 can be quickly replaced without disassembling the entire fixture base 1 and clamping drive mechanism 3, thereby improving the maintenance convenience, reusability and long-term clamping stability of the fixture.

[0091] To verify the stable clamping effect of the flexible clamp of the present invention on the honeycomb lattice wall during the clamping process, this embodiment establishes a flexible clamping finite element model of a single honeycomb lattice wall and calculates the clamping force on both sides of the honeycomb lattice wall after the elastic body expands under pressure. The results are as follows. Figure 10 As shown. By Figure 10 As can be seen in (a), the elastomer undergoes radial expansion after axial compression and forms a stable flexible contact with the cell wall, allowing the clamping load to be transmitted to the cell wall through the elastomer. Figure 10As shown in Figure (b), a clamping force perpendicular to the cell wall can be generated on both sides of a single honeycomb lattice cell wall. The clamping forces on both sides are in opposite directions and their values ​​are generally similar, indicating that the flexible clamping assembly can form a relatively balanced clamping and supporting effect from both sides of the honeycomb lattice cell wall. This result verifies the feasibility of the clamping assembly generating an effective clamping force on the honeycomb lattice cell wall through the radial expansion of the elastomer.

[0092] Based on the above finite element clamping force analysis, to further verify the clamping capability of the flexible fixture of the present invention under actual machining loads, the flexible fixture of the present invention was used to perform actual milling on a TC4 titanium alloy honeycomb structure. The cutting forces in the X, Y, and Z directions during the machining process were measured using a force gauge. The results are as follows: Figure 11 As shown. It should be noted that, to verify the clamping effect of the flexible fixture of this invention when machining with different milling tools, this embodiment specifically customized a set of non-standard honeycomb-specific milling tools for TC4 titanium alloy honeycomb structures. The overall geometry and shape of each tool are similar; only some tool geometric angle parameters were adjusted. N1 to N10 are self-assigned numbers for ease of experimental recording and differentiation of different tool geometric parameter schemes, and do not belong to standard models or commercial product models.

[0093] right Figure 11 The data were statistically analyzed, and the results are shown in Table 1: Under climb milling conditions, the average cutting forces in the X, Y, and Z directions were 3.973 N, 3.568 N, and 5.899 N, respectively, with a resultant average force of 9.118 N; under conventional milling conditions, the average cutting forces in the X, Y, and Z directions were 3.097 N, 3.832 N, and 4.631 N, respectively, with a resultant average force of 7.750 N. These results indicate that under the actual clamping conditions of the flexible fixture of this invention, the honeycomb structure can maintain a stable machining state under milling loads.

[0094] Table 1. Average values ​​of cutting force and resultant force in three directions under different milling methods.

[0095]

[0096] comprehensive Figure 10 and Figure 11 It can be seen that, Figure 10 From the perspective of finite element calculation, it can be seen that a single clamping component can form a flexible clamping and local support effect on both sides of the cell wall of the honeycomb core through the radial expansion of the elastomer; Figure 11 The cutting loads in the X, Y, and Z directions, measured during actual milling using the flexible fixture of this invention, are given. Because this invention employs multiple clamping components 2 distributed in a honeycomb lattice array, each clamping component forms multi-point flexible support and friction clamping within the honeycomb lattice through radial expansion of the elastic body, and collectively bears the load generated during machining. Therefore, Figure 10The finite element clamping results and Figure 11 The actual milling load results demonstrate that the flexible fixture of the present invention has the corresponding clamping and support capabilities under the processing conditions of this embodiment, from the aspects of clamping action and processing load, and provide a basis for the comparative verification of the surface quality of subsequent processing.

[0097] To verify the effect of the flexible fixture of this invention on suppressing burrs on the honeycomb lattice wall, lattice deformation, and tool damage during feed and withdrawal, this embodiment, under the same processing conditions, clamped and milled TC4 titanium alloy honeycomb structures using both conventional clamping methods and the flexible fixture of this invention. The conventional clamping method uses double-sided adhesive to bond the bottom surface of the honeycomb structure with corner clamping blocks for secure fixing. The flexible fixture of this invention, however, extends its clamping components into the honeycomb lattice and utilizes the radial expansion of an elastomer to achieve flexible support and clamping within the holes. Except for the clamping method, all other processing conditions remained consistent: spindle speed 2000 r / min, feed rate 100 mm / min, cutting width 5.6 mm, and depth of cut 0.5 mm. After processing, the surface morphology and defect characteristics of the honeycomb structures under the two clamping methods were compared and analyzed.

[0098] Figure 12 The clamping states of honeycomb structural components under different clamping methods and the surface defect morphology after machining are presented. Figure 12 (a) is a schematic diagram of the traditional clamping method. Figure 12 (b) is a schematic diagram of the flexible clamping device of the present invention. Figure 12 Images (c) and (d) show the post-machining surface morphology for the two clamping methods, respectively. Figure 12 As can be seen in (c), after processing using the traditional clamping method, there are obvious burrs and local tears on the edges of the honeycomb lattice walls. Long strips of chips and damage to the lattice edges can be observed in some areas. The main reason is that the traditional clamping method mainly relies on double-sided adhesive on the bottom surface and four corner clamping blocks to fix the honeycomb structure, which lacks effective support inside the honeycomb lattice. At the same time, the double-sided adhesive has limited constraint on the bottom of the honeycomb structure. Under the action of periodic cutting loads and processing vibrations, local areas may experience slight detachment and vertical movement, which further aggravates the vibration, local deformation, and tool deflection of the honeycomb lattice walls, resulting in processing defects such as burrs, tears, long strips of chips, and damage to the lattice edges.

[0099] Depend on Figure 12As can be seen in (d), after machining using the flexible fixture of this invention, the surface quality of the honeycomb structure is significantly improved, the edges of the honeycomb lattice holes are more intact, and surface burrs are significantly reduced. Actual machining samples were taken and inspected using an optical digital microscope, and the length of most chips was found to be no more than 0.3 mm. Compared with traditional clamping methods, the flexible fixture of this invention forms distributed flexible support and clamping within the honeycomb lattice through multiple clamping components, improving the constraint stability of the honeycomb structure during machining and reducing local vertical movement and vibration and deformation of the honeycomb lattice holes. Therefore, long strip-shaped chips and pulling burrs caused by machining vibration are significantly reduced, chip removal is improved, and lattice damage during the feed and discharge stages is also reduced.

[0100] comprehensive Figures 10-12 The finite element clamping results, actual milling force measurement results, and comparison results of the machined surface morphology show that the flexible fixture of the present invention can provide stable flexible clamping and support for thin-walled porous honeycomb structures under the processing conditions of this embodiment, and can reduce the vibration, deformation and related processing defects of the honeycomb core cell wall during processing, thus meeting the clamping and support requirements for machining such thin-walled porous honeycomb structures.

[0101] The reason why the flexible clamp of the present invention produces the above-mentioned effect is that each clamping component 2 in the flexible clamp of the present invention extends into the honeycomb core of the honeycomb structure, and forms distributed flexible support and friction clamping inside the honeycomb core through the axial compression and radial expansion of the elastic body 204.

[0102] On the one hand, the elastomer 204 expands radially after axial compression, forming radial contact pressure between its outer wall and the cell wall of the honeycomb lattice. This creates clamping force through friction at the contact interface, thereby improving the holding capacity of the honeycomb structure in the Z-direction (perpendicular to the cell wall). During milling, when the Z-direction component of the cutting force acts on the honeycomb structure, the friction between the elastomer 204 and the cell wall constrains the load in that direction, reducing axial movement and local tool deflection. Simultaneously, the expanded elastomer 204 provides local support to the cell wall within the honeycomb lattice, reducing local deformation and springback of the cell wall under tool load, thus minimizing machining defects such as burrs caused by local tool deflection.

[0103] On the other hand, the elastomer 204 has certain elastic and damping characteristics. Under milling load, it can dissipate some vibration energy through its viscoelastic deformation, thus playing a buffering and vibration reduction role. When the tool contacts the honeycomb lattice wall, the cutting load and vibration are transmitted to the elastomer 204 through the honeycomb lattice wall. The elastomer 204 reduces the vibration response of the honeycomb lattice wall through elastic deformation and damping energy dissipation, thereby reducing machining defects such as burrs, tears and long strips of chips caused by vibration.

[0104] Meanwhile, the elastic body, after expanding under pressure, plays a local filling and supporting role inside the honeycomb lattice, which can improve the in-plane stiffness of the honeycomb structure and make the inner wall of the honeycomb lattice less prone to collapse, cell collapse and local deformation under milling load. Especially during the tool entry and exit process, the impact load of the tool on the edge of the honeycomb lattice is relatively large. The flexible expansion support of the elastic body can improve the stress state of the edge of the honeycomb lattice, disperse the impact load of the tool to the elastic body 204, and reduce the lattice damage caused by the tool entry and exit impact.

[0105] In summary, the flexible fixture of this invention employs an axial drive structure with a reverse-screw and a threaded drive plate. The drive plate transmits axial tension to the upper force-applying component via a connector, while the lower force-applying component is axially supported by the fixture base, which is in a fixed state. This forms a closed force transmission loop composed of the fixture base, reverse-screw, drive plate, and connector. This, combined with the flexible expansion support within the honeycomb lattice and the buffering and vibration reduction effect of the elastomer, ensures the stability of the clamping force. Simultaneously, the fixture base, as a pressure-bearing component, with its integrated metal structure design, effectively resists deformation caused by the top support force, ensuring the synchronicity and consistency of the displacement of each clamping component. This effectively improves the clamping stability and surface quality of the honeycomb structure, significantly reducing machining defects such as surface burrs, long strips of chips, hole wall tears, and damage to the cutting core during entry and exit. This meets the requirements for low-damage, high-stability milling of thin-walled porous honeycomb structures.

[0106] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A flexible fixture for machining thin-walled porous honeycomb structural parts, characterized in that, Includes a clamp base, clamping assembly, and clamping drive mechanism; The clamp base is used to support the thin-walled porous honeycomb structure component. It is provided with a plurality of guide mounting holes, which are arranged in an array on the clamp base and correspond one-to-one with a plurality of honeycomb cells of the thin-walled porous honeycomb structure component. The number of clamping components is multiple, and each corresponds to one of the multiple guide mounting holes on the clamp base; each clamping component is axially movable in the guide mounting hole, and the clamping component includes a connector, an upper force-applying component, a lower force-applying component, and an elastic body disposed between the upper force-applying component and the lower force-applying component; The connector passes through the upper force-applying member, the elastic body, and the lower force-applying member in sequence. One end of the connector has a limiting part, which abuts against the upper end face of the upper force-applying member. The lower end face of the lower force-applying member abuts against the upper surface of the clamp base. The elastic body can extend into the honeycomb core of the thin-walled porous honeycomb structure when it is not compressed. The other end of the connector passes through the guide mounting hole and extends out of the lower end of the clamp base; The clamping drive mechanism is horizontally disposed below the clamp base, and includes a drive plate and an axial drive component detachably connected to the drive plate; one end of the connector extending out of the lower end of the clamp base is fixedly connected to the drive plate; the axial drive component passes through the drive plate and its upper end can abut against the clamp base; The axial drive is configured to: drive and move axially upward while the clamp base is fixed, and force the drive plate to move downward relative to the clamp base when the axial drive abuts against the clamp base, thereby increasing the axial distance between the clamp base and the drive plate; the elastomer is capable of having a corresponding axial compression under the action of the axial distance; the elastomer has radial expansion deformation generated by the axial compression, the radial expansion deformation being used to form a clamping fit with the cell wall of the honeycomb core.

2. The flexible clamp according to claim 1, characterized in that, The connector is a plug bolt, comprising a bolt head, a smooth rod section, and a threaded section that are coaxially fixedly connected in sequence; the lower end face of the bolt head abuts against the upper end face of the upper force-applying member; the smooth rod section passes through the upper force-applying member, the elastic body, and the lower force-applying member in sequence, and is disposed in the guide mounting hole; the threaded section extends out of the lower end face of the clamp base and is threadedly engaged with the drive plate.

3. The flexible clamp according to claim 2, characterized in that, The smooth section of the plug bolt and the guide mounting hole are fitted with a clearance to ensure that the plug bolt moves axially and to limit the radial offset of the clamping assembly.

4. The flexible clamp according to claim 1, characterized in that, The axial drive component is a reverse screw; the reverse screw is threadedly engaged with the drive plate, and the upper end of the reverse screw can abut against the clamp base after it moves upward axially to its position. The lower end of the reverse screw extends out of the lower end of the drive plate and is provided with an internal hexagonal hole for screwing. The reverse screw is configured to: by screwing the reverse screw, the upper end of the reverse screw abuts against the clamp base, while the drive plate moves downward relative to the clamp base under threaded drive. The drive plate drives the connecting member to move downward, causing the upper force-applying component to move toward the lower force-applying component, thereby applying axial compression to the elastic body located between the upper and lower force-applying components.

5. The flexible clamp according to claim 4, characterized in that, The number of the anti-top screws is multiple, and the multiple anti-top screws are evenly spaced on the drive plate. By rotating each anti-top screw in a cross or synchronous manner, the axial compression of the elastic body of each clamping assembly is kept consistent.

6. The flexible clamp according to claim 1, characterized in that, The clamp base includes an integrally formed limiting plate, guide plate, and base; the limiting plate is located on the upper part of the clamp base and is used to support the bottom surface of the thin-walled porous honeycomb structure; the limiting plate is provided with a plurality of limiting slots for the rod segment of the connector to pass through, and the lower force-applying member is embedded in the limiting slots to restrict the circumferential rotation of the clamping assembly; The guide plate is parallel to the limiting plate and located below the limiting plate; the guide mounting holes are provided on the guide plate and correspond one-to-one with the limiting slot holes. The base is arranged parallel to the bottom of the guide plate to form the mounting reference for the fixture base.

7. The flexible clamp according to claim 6, characterized in that, The upper and lower force-applying components are made of rigid gaskets; the elastomer is a polyurethane block with a Shore hardness of 30A to 60A; the outer contours of the elastomer and the rigid gaskets are adapted to the inner contours of the honeycomb core; the size of the rigid gasket is equal to the size of the elastomer.

8. The flexible clamp according to claim 7, characterized in that, The outer contours of the upper force-applying component, the lower force-applying component, and the elastic body are all regular hexagons; the limiting slot is a hexagonal slot that matches the outer contour of the lower force-applying component.

9. The flexible clamp according to claim 4, characterized in that, It also includes a compression adjustment component; the compression adjustment component is coaxially sleeved on the axial drive member and located below the drive plate; the compression adjustment component has a predetermined axial dimension, which is determined according to the maximum axial displacement actually required by the axial drive member.

10. A flexible clamping method for a thin-walled porous honeycomb structure, characterized in that, The flexible fixture according to any one of claims 1 to 8 is used to achieve the following steps: The thin-walled porous honeycomb structure is placed horizontally on the fixture base, so that each clamping component extends into the honeycomb core of the thin-walled porous honeycomb structure. With the fixture base fixed, the axial drive member moves axially upward relative to the drive plate, so that the upper end of the axial drive member abuts against the fixture base. Continue operating the axial drive component; since the clamp base remains fixed, the axial drive component no longer moves upward along the axial direction, forcing the drive plate to move downward relative to the clamp base, driving the connecting component connected to it to move downward synchronously, increasing the axial distance between the clamp base and the drive plate; During the downward movement of the drive plate, the limiting part of the connector drives the upper force-applying member to move closer to the lower force-applying member, and the lower force-applying member is axially supported by the clamp base, so that the elastic body is axially compressed between the upper force-applying member and the lower force-applying member. When the elastomer is compressed, it expands radially and forms a flexible clamping fit with the cell wall of the honeycomb core.

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