Modular design laser welding end effector suitable for connection of large thermoplastic composite material and metal structure

Abstract

The invention belongs to the field of dissimilar material connection, and discloses a modular design laser welding end effector suitable for connection of a large thermoplastic composite and a metal structure, which comprises a pressurization module, a heating module and a compression roller module. The pressurizing module adopts a floating joint and a linear guide rail to transmit the contraction force of an air cylinder, so that the driving, guiding and counter-force of pressure in the connecting process all act on the pressurizing module, and the rigidity requirement of the whole welding tail end is reduced; the compression roller module can be rapidly switched between a single shape follow-up compression roller pressurization mode and a multi-plane compression roller pressurization mode, and a stable normal load is provided for curved surface structure welding. The device has high adaptability to the size and shape of the thermoplastic composite and metal connecting component, stable and uniform follow-up pressure and heating effect can be provided in the connecting process, and the requirements for the pressure and temperature in the laser connecting process of the large-size complex thermoplastic composite and metal component in the fields of aerospace and the like are met; and meanwhile, the connection quality is high.

Description

Technical Field

[0001] This invention belongs to the field of dissimilar material joining, and relates to a modular laser welding end effector suitable for joining large thermoplastic composites with metal structures. Background Technology

[0002] Thermoplastic composites and lightweight alloys (hereinafter referred to as composites and metals) possess excellent properties and are widely used in aerospace, high-speed rail, and automotive equipment in the form of laminated structures. However, the connection method for dissimilar material laminated structures has long been a research challenge. Existing connection methods are mostly mechanical connections such as screwing and riveting, which require drilling. These methods can compromise surface integrity, affecting functions such as wave absorption and stealth, and also increase structural weight due to the large number of fasteners introduced. Compared to mechanical connections, fusion welding technology, which utilizes the multiple melting and solidification characteristics of thermoplastic resins to achieve connection under temperature and pressure, has advantages such as intact component surfaces and effective weight reduction. It has become the preferred technology for connecting thermoplastic composites with dissimilar materials. Among these technologies, laser welding technology, with its high degree of automation and adaptability to curved structures, is attracting the attention of scholars both domestically and internationally.

[0003] The principle of laser joining between thermoplastic composites and metal laminates involves focusing a laser beam onto the metal surface to generate the temperature field required for welding. Utilizing the high thermal conductivity of the metal, heat is conducted to the interface between the two materials, melting the resin at the metal-thermoplastic composite interface. Under appropriate pressure, the molten resin fully wets the metal surface, producing mechanical anchoring and chemical bonding effects, thus achieving the connection between the composite and the metal laminate. The uniform and stable temperature and pressure during laser joining effectively suppresses deformation of the joint and the generation of internal defects, improving the connection quality. With the widespread application of thermoplastic composites in high-end aerospace equipment such as fighter jets, laser joining technology between thermoplastic composites and metals will be applied in the assembly of large components such as wings and fuselage sections. This includes the connection of numerous large curved surface components such as metal stringers and thermoplastic composite skins. This requires actuators to provide uniform and stable follow-up pressure and heating effects during the connection of large curved surface components. Furthermore, due to the variety and variability of connection structures, the actuators must possess high adaptability to meet the connection requirements of different sizes and structures. In summary, to provide uniform and stable follow-up pressure and heating effect during the laser bonding process of large-size thermoplastic composites and metal structures, and to improve the adaptability of laser welding equipment to different sizes and structures, it is urgent to develop a laser welding end effector suitable for bonding various large-size thermoplastic composites and metal structures.

[0004] Chinese patent CN 110789131A discloses a controllable progressive loading clamping device and method for laser joining thermoplastic composite materials and lightweight alloys. This invention adds pressure points around the laser scanning area outside the area to be joined and adjusts the pressure through pressure acquisition and feedback, achieving a joining size of only 120mm × 40mm. While this device and method can provide relatively stable welding pressure to the joining area through real-time pressure detection and feedback adjustment, it is only suitable for laser joining of small, simple-shaped components and has poor adaptability to joining samples of different sizes and curved surfaces. Chinese patent CN 119368926A invented a laser welding device for producing metal matrix composite materials. It uses slide rails and a sliding table to adjust the focusing distance to meet the welding temperature conditions. Different sizes and structural components are fixedly installed by adjusting movable blocks and other parts on the worktable to achieve laser welding of components. However, limited by the size of the worktable, the above invention is limited to welding small and medium-sized structural components; although it can ensure stable welding temperature, it does not provide uniform and stable pressure to the joining area, failing to meet the pressure requirements in the laser welding process of large-sized heterogeneous material laminated structures. Therefore, based on the above analysis, current laser welding devices cannot meet the temperature and pressure requirements for laser connection of large thermoplastic composites and metal laminated structures. At the same time, they have poor adaptability to the size and shape of the connection structure. It is necessary to invent a modular laser welding end effector suitable for connecting large thermoplastic composites and metal structures to solve the above problems. Summary of the Invention

[0005] To address the aforementioned issues, a modular laser welding end effector suitable for connecting large thermoplastic composites with metal structures has been invented. To achieve continuous laser connection of large, complex components, this invention integrates a pressurizing module, a heating module, and a pressure roller module, designing a laser welding end effector with "pre-pressurization-laser heating-follow-up pressure holding" functions. Pre-pressurization eliminates gaps at the connection interface, promoting uniform temperature distribution; follow-up pressure promotes resin bonding, ensuring joint accuracy and consistency. To prevent variations in laser spot size due to changes in sample thickness and structural curvature during the connection of large curved components, thus affecting metal heating, this invention adds a slide table to the heating module to control laser displacement and adjust the laser spot size, ensuring stable heating. To prevent insufficient rigidity of the equipment carrying the welding end effector from causing uneven pressure distribution and reducing connection quality during connection, this invention employs a floating joint and linear guide rail in the pressurizing module to transmit cylinder contraction force. This ensures a stable pressure source for the connection structure while simultaneously ensuring that the driving, guiding, and reaction forces of pressure during connection all act within the pressurizing module, reducing the overall rigidity requirement of the welding end. The pressure roller module adopts an asymmetrical design, with the left and right modules respectively implementing pre-compression and follow-up pressure holding. The left module has reserved rotational degrees of freedom to bring the pressure roller closer to the heating position, reducing the loss of pre-compression force. To improve the actuator's adaptability to curved surfaces and other structures, the right module incorporates a quick-release structure design, allowing for rapid switching between single conformal pressure roller and multi-planar pressure roller pressing modes, providing stable normal loads during the welding of curved structures. This invention possesses high adaptability to the size and shape of thermoplastic composites and metal connecting components, providing stable and uniform follow-up pressure and heating effects during the connection process. It meets the pressure and temperature requirements of aerospace and other fields for laser joining large-sized complex thermoplastic composites and metal components, while also achieving high connection quality.

[0006] The technical solution of the present invention:

[0007] A modular laser welding end effector suitable for connecting large thermoplastic composites with metal structures includes a pneumatic pressurization module A, a heating module B, a pressure roller module C, a rear wall plate D, and a front wall plate E; the pressurization module A is installed between the rear wall plate D and the front wall plate E, the heating module B is installed on the rear wall plate D, and the pressure roller module C is installed on the pressurization module A;

[0008] The pressurizing module A includes a floating joint a1, a cylinder a2, a left wall plate a3, a pneumatic joint a4, a slider a5, a guide rail a6, and a slide block a7. The modular laser welding end effector includes two sets of pressurizing modules A, arranged in a symmetrical and compact manner. The cylinder a2 is mounted on the outside of the left wall plate a3 via a cylinder mounting block. The cylinder a2 contracts to provide clamping force, which is then converted into a power source for applying pressure. The floating joint a1 is connected to the cylinder a2 to eliminate axial and radial errors and force components, preventing damage to the cylinder a2 from eccentric torque. The slide block a7 is connected to the floating joint a1 via the pneumatic joint a4 and is mounted on the inside of the left wall plate a3. The guide rails a6 and sliders a5 are mounted on the left wall plate a3. The use of two guide rails a6 and four sliders a5 further enhances the force source direction constraint of the pressure module A and improves the stability of the pressure application and reaction force bearing capacity. The slide block a7 is connected to the floating joint a1 by the pneumatic joint a4, thereby converting the contraction force of the cylinder a2 into the clamping force applied to the workpiece by the pressure roller. The pressure module A adopts a left-right symmetrical compact design to improve space utilization. The pressure module A uses the floating joint a1 and the linear guide rail a6 to transmit the contraction force of the cylinder a2. While ensuring a stable pressure source for the workpiece, the driving, guiding and reaction forces of the pressure during the connection process are all applied in the pressure module A, reducing the stiffness requirements of the entire welding end.

[0009] Heating module B includes a laser displacement sensor b1, a laser welding joint b2, and a linear module b3. The laser welding joint b2 is mounted on the linear module b3 via a fixing plate. The linear module b3 is bolted to the rear wall panel D. The laser welding joint b2 provides the laser beam for connection. The laser displacement sensor b1 monitors and provides feedback data. The linear module b3 drives the laser welding joint b2 to move, ensuring the stability of the laser heating effect during the connection process. It can also be used with a robotic arm to achieve curved surface connection.

[0010] The pressure roller module C includes a left pressure roller adapter block c1, a left pressure roller bracket c2, a left pressure roller connecting rod c3, a left pressure roller c4, a right pressure roller adapter block c5, a right pressure roller connecting rod c6, a right pressure roller mounting base c7, and a right pressure roller assembly c8. The left pressure roller c4 is mounted on the left pressure roller bracket c2 via the left pressure roller connecting rod c3. The left pressure roller bracket c2 is connected to a slide a7 of a pressure module A via the left pressure roller adapter block c1. The left pressure roller adapter block c1 is connected to the left pressure roller bracket c2 and the slide a7 via bolts. The main function of the left-side pressure application is to pre-clamp the workpiece. To ensure that the clamping force on both sides of the workpiece weld seam remains as uniform as possible during laser joining, the left-side pressure roller mechanism needs to bring the force application point as close as possible to the laser beam after clamping. Therefore, the design... The left pressure roller connecting rod c3 has one degree of rotational freedom, which can deflect nearly 35° counterclockwise after clamping, bringing the left pressure roller closer to the weld and reducing pre-clamping pressure loss. The right pressure roller group c8 is connected to the right pressure roller mounting seat c7, the right pressure roller mounting seat c7 is connected to the right pressure roller connecting rod c6, the right pressure roller connecting rod c6 is connected to the right pressure roller adapter block c5, and the right pressure roller adapter block c5 is bolted to the slide a7 of another pressure module A. The main function of the pressure applied on the right side is to maintain pressure during the cooling process after laser heating. Therefore, when laser connection is required for simple structures such as planes, the right pressure roller group c8 is used to apply follow-up pressure, resulting in higher structural rigidity and more uniform pressure distribution, which is beneficial to improving the contact state of the joint during cooling in the laser connection process. Meanwhile, the right-side pressure application incorporates a quick-release structure design, allowing for rapid switching between single-roller and multi-roller pressure modes. When dealing with the connection needs of complex structures such as curved surfaces, the right-side pressure roller mounting base c7 can be quickly removed and replaced with the conformal pressure roller c9, providing a stable normal load during the welding of curved structures.

[0011] The beneficial effects of this invention are as follows: A modular laser welding end effector suitable for connecting large thermoplastic composites and metal structures is invented. It provides stable temperature and pressure to the connection area during the connection process of large components through a "pre-compression pressure application - laser heating - follow-up pressure holding" method, enabling continuous laser welding of large components. The heating module allows for spot size adjustment during heating, improving the stability of the heating effect during connection. The pressure drive, guide, and reaction forces of the pressure module all act within the pressure module, reducing the stiffness requirement of the entire welding end and providing a stable pressure source during connection. To improve the actuator's adaptability to complex structures such as curved surfaces, the pressure roller module can quickly switch between single conformal pressure roller and multi-plane pressure roller pressing modes, providing a stable normal load for welding curved structures. This invention, when used in conjunction with robots, can provide stable temperature and pressure during the laser bonding process of large thermoplastic composites and metal components. At the same time, by switching the pressure roller mode, it can be applied to the laser bonding of complex structures such as curved surfaces. It has high dimensional and structural adaptability, high application value, and can meet the laser bonding needs of thermoplastic composites and metals in aerospace and other fields. Attached Figure Description

[0012] Figure 1 A simplified diagram of the actuator structure;

[0013] Figure 2 A simplified structural diagram of the pressurization module;

[0014] Figure 3 Here is a simplified structural diagram of the pressure roller module;

[0015] Figure 4 This is a simplified structural diagram of the heating module.

[0016] In the diagram: A - Pressurization module, B - Heating module, C - Pressure roller module, D - Rear wall panel, E - Front wall panel, a1 - Floating joint, a2 - Cylinder, a3 - Left wall panel, a4 - Pneumatic joint, a5 - Slider, a6 - Guide rail, a7 - Slide seat, b1 - Laser displacement sensor, b2 - Welding laser head, b3 - Linear module, c1 - Left pressure roller adapter block, c2 - Left pressure roller bracket, c3 - Left pressure roller connecting rod, c4 - Left pressure roller, c5 - Right pressure roller adapter block, c6 - Right pressure roller connecting rod, c7 - Right pressure roller mounting seat, c8 - Right pressure roller group, c9 - Conformal pressure roller. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0018] The pneumatic pressurization module generates a follow-up pressure clamping force ranging from 0-1500N; the welding laser is a YLR-2000-MM-WC-Y18 manufactured by IPG Industries, Inc., which can provide a rectangular spot with a laser power of 0-2000W; the laser displacement sensor is a Panasonic HG-C1200 model, with a measurement distance of 200mm±80mm; the robotic arm is a KUKA KR210R2700 model, with an effective load capacity of 210kg; the connecting materials are CF / PEEK thermoplastic composite material and aluminum alloy 6061, and the dimensions of the sample connection part are 600mm×40mm.

[0019] A laser welding end effector suitable for joining large thermoplastic composite materials with metals includes a pneumatic pressurization module A, a heating module B, a pressure roller module C, a rear wall plate D, and a front wall plate E. In the actuator, the pressurization module A is bolted between the rear wall plate D and the front wall plate E, and the heating module B is bolted to the rear wall plate D.

[0020] Furthermore, in the pressurizing module A, the cylinder a2 in the pressurizing structure is fixedly connected to the left wall plate a3 through the cylinder mounting block. The cylinder a2 contracts to provide clamping force. The design mechanism converts the cylinder contraction force into a pressure power source. The floating joint a1 is selected to eliminate the radial direction error and component force of the cylinder shaft, and to prevent the cylinder from being damaged by eccentric torque. The slide a7 is installed on the left wall plate a3 through the guide rail a6 and the slider a5. The double slide rail plus four sliders are used to further enhance the force source direction constraint of the pressurizing module A and improve the stability of the pressure application and reaction force bearing capacity. Finally, the pneumatic joint a4 is used to connect the slide a7 and the floating joint a1, thereby converting the cylinder contraction force into the clamping force applied to the workpiece by the pressure roller. The pressurization module A in the actuator adopts a symmetrical and compact design to improve space utilization. The entire module uses a floating joint and linear guide rail to transmit the cylinder contraction force. While ensuring that a stable pressure source can be provided for the curved structure, the driving, guiding and reaction forces of the pressure during the connection process are all applied to the pressurization module A, reducing the stiffness requirements of the entire welding end.

[0021] Furthermore, in the heating module B, the laser welding joint b2 is mounted on the linear module b3 via a fixing plate. The linear module b3 is bolted to the rear wall plate D. The laser welding joint b2 provides the laser connection laser beam, and the laser displacement sensor b1 monitors and provides feedback data. The linear module b3 drives the laser welding joint b2 to move, ensuring the stability of the laser heating effect during the connection process. It can also be used in conjunction with a robotic arm to achieve curved surface connection.

[0022] Furthermore, in the pressure roller module C, the left pressure roller c4 is mounted on the left pressure roller bracket c2 via the left pressure roller connecting rod c3. The left pressure roller bracket c2 is connected to the slide a7 via the left pressure roller adapter block c1. The left pressure roller adapter block c1 is connected to the left pressure roller bracket c2 and the slide a7 in a pressure module A via bolts. The main function of the left pressure application is to pre-clamp the workpiece. To ensure that the clamping force on both sides of the workpiece weld is as uniform as possible during the laser connection process, the left pressure roller mechanism needs to bring the force application point as close as possible to the laser beam after clamping. Therefore, the left pressure roller connecting rod c3 is designed to have one degree of rotational freedom, allowing it to deflect nearly counterclockwise after clamping. The 35° angle brings the left pressure roller closer to the weld, reducing pre-clamping pressure loss. In the right pressure roller mechanism, the right pressure roller group c8 is connected to the right pressure roller mounting seat c7, the right pressure roller mounting seat c7 is connected to the right pressure roller connecting rod c6, the right pressure roller connecting rod c6 is connected to the right pressure roller adapter block c5, and the right pressure roller adapter block c5 is bolted to the slide a7 in another pressurizing module A. The main function of the right pressure application is to maintain pressure during the cooling process after laser heating. Therefore, when facing the laser connection requirements of simple structures such as planes, the right pressure roller group c8 is used to apply follow-up pressure, which results in higher structural rigidity and more uniform pressure distribution, which is beneficial to improving the contact state of the joint during cooling in the laser connection process. Meanwhile, the right-side pressure application incorporates a quick-release structure design, allowing for rapid switching between single-roller and multi-roller pressure modes. When dealing with connection requirements for complex structures such as curved surfaces, the right-side pressure roller mounting base c7 can be quickly removed and replaced with the conformal pressure roller c9, providing a stable normal load during the welding of curved surfaces. The left and right pressure roller structures contact the workpiece, respectively providing pre-pressing and follow-up pressure holding pressure during the connection process.

Claims

1. A modular laser welding end effector suitable for connecting large thermoplastic composites to metal structures, characterized in that, The modular laser welding end effector includes a pressure module (A), a heating module (B), a pressure roller module (C), a rear wall plate (D), and a front wall plate (E); the pressure module (A) is installed between the rear wall plate (D) and the front wall plate (E), the heating module (B) is installed on the rear wall plate (D), and the pressure roller module (C) is installed on the pressure module (A); The pressurization module (A) includes a floating joint (a1), a cylinder (a2), a left wall plate (a3), a pneumatic joint (a4), a slider (a5), a guide rail (a6), and a slide block (a7). The modular design of the laser welding end effector includes two sets of pressurization modules (A), which are arranged in a symmetrical and compact manner. The cylinder (a2) is mounted on the outside of the left wall plate (a3) ​​via a cylinder mounting block, and the floating joint (a1) is connected to the cylinder (a2). The slide block (a7) is connected to the floating joint (a1) via the pneumatic joint (a4), and the slide block (a7) is mounted on the left wall plate (a3) ​​via the guide rail (a6) mounted on the inside of the left wall plate (a3) ​​and the slider (a5). The heating module (B) includes a laser displacement sensor (b1), a laser welding joint (b2), and a linear module (b3). The laser welding joint (b2) is mounted on the linear module (b3) via a fixing plate. The linear module (b3) is connected to the rear wall panel (D). The laser welding joint (b2) provides the laser connection laser beam, the laser displacement sensor (b1) monitors and provides feedback data, and the linear module (b3) drives the laser welding joint (b2) to move. The pressure roller module (C) includes a left pressure roller adapter block (c1), a left pressure roller bracket (c2), a left pressure roller connecting rod (c3), a left pressure roller (c4), a right pressure roller adapter block (c5), a right pressure roller connecting rod (c6), a right pressure roller mounting seat (c7), and a right pressure roller assembly (c8). The left pressure roller (c4) is mounted on the left pressure roller bracket (c2) via the left pressure roller connecting rod (c3). The left pressure roller bracket (c2) is connected to the slide (a7) of a pressure module (A) via the left pressure roller adapter block (c1). The right pressure roller assembly (c8) is connected to the right pressure roller mounting seat (c7). The right pressure roller mounting seat (c7) is connected to the right pressure roller connecting rod (c6). The right pressure roller connecting rod (c6) is connected to the right pressure roller adapter block (c5). The right pressure roller adapter block (c5) is bolted to the slide (a7) of another pressure module (A).

2. The modular laser welding end effector according to claim 1, characterized in that, Remove the right pressure roller mounting base (c7) and replace it with the conformal pressure roller (c9).

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