Laser cladding system and control method for Babbitt alloys for sliding bearings having free-form surfaces

Abstract

The present invention provides a laser cladding system for Babbitt alloys for sliding bearings having free-form surfaces and a control method therefor. [Solution] The laser cladding system comprises a robotic arm, a laser cladding device, a parallel connection platform, a femtosecond laser microfabrication module, a molten pool monitoring camera, a contour scanning device, and an X-ray defect detector. The present invention maintains the laser cladding device at an optimal angle through the cooperation of the robotic arm and the parallel connection platform, avoiding non-uniformity of the cladding layer caused by the inclination of the curved surface, and optimizing the molten pool shape by adjusting the angle of the parallel connection platform when lateral displacement occurs in the molten pool. By integrating multimode sensing and monitoring, a fully closed-loop control system is established from the identification of the molten pool shape to the adjustment of process parameters, significantly suppressing defects such as depression or bulging of the cladding layer.

Description

Technical Field

[0001] The present invention relates to the field of laser additive manufacturing technology, and particularly to a laser cladding system for a sliding bearing babbitt alloy having a free-form surface and a control method thereof.

Background Art

[0002] Laser cladding technology is an advanced surface modification technology that has gradually matured with the development of high-power lasers. Its basic principle is to utilize a high-energy laser beam to instantaneously melt metal powder or wire, and at the same time form a dense coating layer metallurgically bonded to the substrate surface, thereby realizing directional strengthening of the performance of the component surface and repair of defects. Compared with conventional surface treatment technologies (such as electroplating and thermal spraying), laser cladding has significant advantages such as a small amount of heat input, controllable dilution rate, high bonding strength, and wide applicability of materials. Conventional laser cladding is mainly planar cladding and uses a single camera for detection. Specifically, it is designed as follows.

[0003] (1) The patent with publication number CN119144954A discloses a laser cladding device for processing cookware, wherein the laser cladding device body and mounting base are arranged on a processing table, a fixed base is provided on the mounting base, a rotating box is rotatably connected inside the mounting base, a movable rod is symmetrically slidably connected on the mounting base, one end of each movable rod near the symmetrical center is inserted into the rotating box, the movable rod is symmetrically hinged connected to a support base, a second clamping rod is provided on each of the movable rods, a clamping block is elastically connected to each of the second clamping rods, a first clamping rod is provided on each of the movable rods, a fixed bar is provided on each of the first clamping rods, an extendable base is elastically connected to the side of each first clamping rod near the second clamping rod, and a fitting groove for fitting with the extendable base is provided on each of the second clamping rods. This allows for quick fixing of cookware, improves stability of cookware during the laser cladding process, allows for clamping of cutting tools, is suitable for various types of cookware, and improves processing efficiency. However, this device lacks the ability to detect the shape of the laser-clad layer, making it difficult to obtain products with good processing quality.

[0004] (2) The patent with publication number CN118268610A discloses a laser wire powder composite apparatus and method for online repair of parts. This invention solves problems such as difficulty in maintaining parts and poor quality by using a robot to perform laser repair, reduces the workload of artificial repair, accurately identifies and analyzes defects using a 3D scanner, can provide various repair methods according to needs, and can adjust the scanning range according to the dimensions of the part, thus increasing the flexibility of the apparatus. However, in the laser cladding process, the curved substrate drips the molten metal liquid due to gravity, which reduces the cladding quality.

[0005] In summary, conventional laser cladding systems have the following main problems: They often use fixed processing platforms, resulting in poor adaptability to free-form surfaces. Furthermore, they lack real-time shape detection capabilities, making them prone to molten liquid dripping during curved surface laser cladding, thus reducing the effectiveness of the laser cladding. [Overview of the project]

[0006] In view of this, the present invention provides a laser cladding system for a Babbitt alloy for a sliding bearing having a free-form surface and a control method thereof, in order to solve the problems present in the background art.

[0007] The present invention provides a laser cladding system for Babbitt alloys for sliding bearings having free-form surfaces. The laser cladding system comprises a robotic arm, a laser cladding device, a parallel connection platform, a femtosecond laser microfabrication module, a molten pool monitoring camera, a contour scanning device, and an X-ray defect detector. The contour scanning device is mounted on the end of the robotic arm and is used to scan the surface contour of the bearing shell (bearing metal) of the sliding bearing to be cladded. The laser cladding device is mounted on the end of the robotic arm and performs laser cladding on the bearing shell of the sliding bearing to be cladded. The femtosecond laser microfabrication module is mounted on the end of the robotic arm and is used to remove bubble defects within the cladding layer and at the interface between the cladding layer and the bearing shell of the sliding bearing to be cladded. The molten pool monitoring camera is mounted on the end of the robotic arm and monitors the shape of the molten pool of the cladding layer. The X-ray defect detector is mounted on the end of the robotic arm and detects the bubble defect status within the cladding layer and at the interface between the cladding layer and the bearing shell of the sliding bearing to be cladded. The parallel connection platform is used to mount the bearing shells of the sliding bearings to be cladded. The robot arm controller is electrically connected to the robot arm, and the parallel connection platform controller is electrically connected to the parallel connection platform. The computer is electrically connected to the contour scanning device, laser cladding device, femtosecond laser microfabrication module, molten pool monitoring camera, X-ray defect detector, robot arm controller, and parallel connection platform controller, respectively.

[0008] Preferably, the laser cladding device employs an optical fiber laser, the femtosecond laser microfabrication module employs a femtosecond laser, and the contour scanning device employs a laser contour scanner.

[0009] Preferably, the melting pool monitoring camera employs a 3D camera or depth camera with infrared active illumination capabilities.

[0010] The present invention provides a method for controlling a laser cladding system for a Babbitt alloy for a sliding bearing having a free-form surface. The control method includes the following steps. S1: Secure the bearing shells of the plain bearings to be cladded to the parallel connection platform. S2: Set the output, wire feed rate, defocus amount, and scan rate of the laser cladding device. S3: A contour scanning device is used to scan the surface of the bearing shell of the plain bearing to be cladded, and the computer is used to obtain 3D model data of the bearing shell of the plain bearing to be cladded. S4: On the computer, a cladding path is set based on 3D model data, and the surface normal vectors of each cladding path point are calculated synchronously. The surface normal vectors are defined as having a positive direction toward the inside of the bearing shell of the sliding bearing to be cladded, and the surface normal vectors are associated with the cladding path points and saved as cladding path data on the computer. S5: Use the robot arm controller to drive the robot arm so that the laser cladding device reaches above the initial cladding path point, and the deviation between the laser direction of the laser cladding device and the surface normal vector of the initial cladding path point is less than 0.1°. S6: The robot arm controller drives the robot arm to move along the cladding path. When the robot arm moves above a cladding path point, the computer retrieves the surface normal vector of that cladding path point and drives the robot arm via the robot arm controller to reduce the deviation between the laser direction of the laser cladding device and the surface normal vector of that cladding path point to less than 0.1°. Next, cladding is started, and the molten pool monitoring camera monitors the molten pool shape of the cladding layer at the cladding path point. Point cloud data of the molten pool shape is sent to the computer to calculate the width of the molten pool. If the width of the molten pool exceeds a first threshold, the computer sends a signal to reduce the output and scan speed of the laser cladding device. If the width of the molten pool is less than a second threshold, the output and scan speed are increased. Furthermore, the computer determines the lateral displacement angle (lateral deviation angle) and direction of the molten pool at the cladding path point based on the point cloud data of the molten pool shape. If the lateral displacement angle of the molten pool is greater than the angle threshold, the parallel connection platform controller drives the parallel connection platform to rotate the bearing shell of the sliding bearing to be cladded in the opposite direction to the lateral displacement direction of the molten pool by the lateral displacement angle of the molten pool. This reduces the lateral displacement of the molten pool at the next cladding path point, optimizes the molten pool shape at the next cladding path point, and updates the surface normal vector of each cladding path point. During cladding at the cladding path point, the X-ray defect detector detects images in real time of the inside of the cladding layer and the bonding interface between the cladding layer and the bearing shell of the sliding bearing to be cladded, transmits these images to the computer for processing, and identifies bubbles with an area greater than the area threshold. If a bubble defect is identified, it is determined that a bubble defect exists, and at this time, the femtosecond laser microfabrication module emits a laser to remove the bubble defect. S7: Step S6 is repeated until the robot arm has traveled along the cladding path to all cladding path points, forming a cladding layer on all cladding path points on the surface of the bearing shell of the sliding bearing.

[0011] Preferably, the bearing shells of the sliding bearings to be cladded are fixed to the work surface of the parallel connection platform via a magnetic attraction fixture. In the initial state, the origin of the platform coordinate system of the parallel connection platform and the origin of the base coordinate system of the robot arm are aligned by calibration, the parallel connection platform is at the horizontal zero position, and the feedback values ​​of each support leg displacement sensor of the parallel connection platform are all 0 mm.

[0012] Preferably, the molten pool monitoring camera monitors the molten pool shape and transmits point cloud data of the molten pool shape to a computer. The computer performs noise reduction on the point cloud data of the molten pool shape using a bilateral filter, then reconstructs a 3D model of the molten pool. Next, it extracts the edges of the molten pool using an adaptive thresholding algorithm and calculates the width. If the width of the molten pool exceeds 4 mm, the computer transmits a voltage signal to the laser cladding device via an analog quantity output module, reducing the output at a rate corresponding to 1% of the maximum output to 0.1 V. If the width of the molten pool is less than 3.5 mm, it increases the output at the same rate, with an output adjustment step width of 10 W. The scan speed is adjusted by pulse frequency control, with 100 pulses corresponding to a scan distance of 1 mm, and a speed adjustment step width of 0.1 mm / s.

[0013] Preferably, the computer obtains the surface normal vector of the geometric center point of the molten pool based on a three-dimensional model of the molten pool, and the positive direction is defined as the direction of the surface normal vector pointing towards the interior of the molten pool, and the angle between the surface normal vector and the surface normal vector at the current cladding path point is defined as the lateral displacement angle of the molten pool at the current cladding path point.

[0014] Preferably, the surface normal vector of the cladding path point is updated by rotating it in the opposite direction to the lateral displacement direction of the molten pool by the lateral displacement angle of the molten pool. [Effects of the Invention]

[0015] The present invention has the following beneficial effects.

[0016] 1. By adopting a cooperative control architecture between the robot arm and the parallel connection platform, the limitations of conventional fixed processing platforms in their adaptability to curved surface processing are overcome, enabling continuous dynamic posture compensation for cladding of free-form surfaces. The synergistic effect of the robot arm's multi-axis flexibility and the parallel connection platform's precision leveling function allows the laser cladding device to maintain the optimal processing angle throughout, avoiding the problem of uneven cladding due to surface inclination. Furthermore, if lateral displacement occurs in the molten pool, the angle of the parallel connection platform can be adjusted to achieve the optimal molten pool shape. For example, if leftward displacement occurs in the molten pool shape, the parallel connection platform is adjusted to shift to the right; if rightward displacement occurs, the parallel connection platform is adjusted to shift to the left. The displacement of the parallel connection platform is not limited to left or right; the displacement angle and direction of the parallel connection platform are determined by imaging from a molten pool monitoring camera and computer evaluation of the lateral displacement angle and direction of the molten pool shape.

[0017] 2. By integrating multi-mode sensing and monitoring using support leg displacement sensors, 6-axis force sensors, contour scanning devices, and molten pool monitoring cameras, data is received and controlled in cooperation with a computer. This overcomes the drawback of conventional laser cladding, which lacks shape feedback. It establishes a fully closed-loop control system from molten pool shape identification to adjustment of process parameters (laser direction, output and scan speed of the laser cladding device, and displacement angle of the parallel connected platform). This allows for real-time capture of dynamic changes in the molten pool shape and control of process parameters. By combining these dynamic process parameters with the control mechanism, uncontrollable phenomena in the flow of molten metal during the curved surface cladding process are eliminated, defects such as depressions or protrusions in the cladding layer are significantly suppressed, and the stability of forming and surface flatness of the cladding layer on complex curved surfaces are essentially improved, ensuring the metallurgical bonding quality of the cladding layer on complex curved surfaces.

[0018] 3. Using an X-ray defect detector, bubble defects are detected in real time within the cladding layer and at the interface between the cladding layer and the bearing shell of the sliding bearing to be cladded. If a bubble with an area larger than the area threshold is detected, it is determined that a bubble defect exists, and at this time the femtosecond laser microfabrication module emits a laser to remove the bubble defect. This intelligent detection and defect processing linked mechanism enables real-time monitoring and automatic repair of bubble defects within the cladding layer and at the interface between the cladding layer and the bearing shell of the sliding bearing to be cladded, effectively improving the density and integrity of the cladding layer. The crystal structure of the cladding layer becomes finer and more uniform, reducing the cost of subsequent manual detection and repair, and improving the level of automation in processing and product quality. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram of the laser cladding system for a Babbitt alloy sliding bearing having a free-form surface according to the present invention. [Figure 2] This is a diagram showing the rightward shift in the shape of the molten pool. [Figure 3] This diagram shows the state in which the angle of the parallel connection platform in the present invention is adjusted to the left to maintain the molten pool shape in the center. [Figure 4] This is a diagram showing the leftward shift in the shape of the molten pool. [Figure 5] This diagram shows the state in which the angle of the parallel connection platform in the present invention is adjusted to the right to maintain the molten pool shape in the center. [Figure 6] This is a schematic diagram of a bubble defect that occurred during the cladding of a dovetail groove in the bearing shell of a sliding bearing. [Figure 7] This is a schematic diagram illustrating how the combined action of the X-ray defect detector and the femtosecond laser microfabrication module in the present invention removes air bubble defects during the cladding of a dovetail groove in the bearing shell of a sliding bearing. [Figure 8]It is a logical block diagram of a control method for a laser cladding system of a babbit alloy for a sliding shaft having a free-form surface of the present invention.

Explanation of symbols

[0020] 1 Robot arm, 2 Parallel connection platform, 3 Parallel connection platform controller, 4 Robot arm controller, 5 Laser cladding device, 6 Femtosecond laser micromachining module, 7 Molten pool monitoring camera, 8 Profile scanning device, 9 Computer, 10 X-ray defect detector, 11 Molten pool, 12 Guide wire nozzle, 13 Laser lens, 14 Cladding laser, 15 Wire, 16 Groove, 17 Bubble defect, 18 Clad layer

Embodiments for carrying out the invention

[0021] Hereinafter, the present invention will be described in detail while referring to the drawings and embodiments.

[0022] As shown in Figures 1 and 2, embodiments of the present invention provide a laser cladding system for Babbitt alloy for sliding bearings having a free-form surface. The system comprises a robot arm 1, a parallel connection platform 2, a parallel connection platform controller 3, a robot arm controller 4, a laser cladding device 5, a femtosecond laser microfabrication module 6, a molten pool monitoring camera 7, a contour scanning device 8, a computer 9, and an X-ray defect detector 10. The contour scanning device 8 is attached to the end of the robot arm 1 and is used to perform contour scanning on the surface of the bearing shell (cladding substrate) of the sliding bearing to be cladded. The laser cladding device 5 is attached to the end of the robot arm 1 and moves in conjunction with the robot arm 1 to perform laser cladding operations. During laser cladding, the cladding laser 14 emitted by the laser cladding device 5 penetrates the laser lens 13 at its tip and is used to heat the wire 15 output from the guide wire nozzle 12. This enables metallurgical bonding between the wire 15 and the surface of the bearing shell of the sliding bearing to be cladded (for example, the surface of the dovetail groove 16 provided in the bearing shell of the sliding bearing), forming a cladding layer 18. The femtosecond laser microfabrication module 6 is attached to the end of the robot arm 1 and is used to subdivide the grain structure of the rubbing layer using a micro-explosion of air, to expel bubbles, and to form a dense cladding layer. The molten pool monitoring camera 7 is attached to the end of the robot arm 1 and monitors the shape of the molten pool of the cladding layer in real time. If a lateral displacement occurs in the shape of the molten pool 11, the parallel connection platform 2 adjusts the angle to ensure that the molten pool shape is optimal. Figures 2, 3, 4, and 5 show the molten pool shapes formed on the parallel connection platform 2 at different angles for a single drop of molten liquid. The X-ray defect detector 10 is attached to the end of the robot arm 1 and is used to perform X-ray defect detection on the cladding layer and to detect the condition of bubble defects 17 within the cladding layer and at the bonding interface between the cladding layer and the bearing shell of the sliding bearing to be cladded.Figures 6 and 7 show the situation where bubble defects 17 are present at the interface between the cladding layer and the bearing shell of the sliding bearing to be cladded, and the situation where bubble defects 17 are not present, respectively. The robot arm controller 4 is electrically connected to the robot arm 1 and controls the movement of the robot arm 1. The parallel connection platform 2 is used to place the bearing shell of the sliding bearing to be cladded. The parallel connection platform controller 3 is electrically connected to the parallel connection platform and controls the movement of the parallel connection platform. The computer 9 is electrically connected to the contour scanning device, laser cladding device, femtosecond laser microfabrication module, molten pool monitoring camera, X-ray defect detector, robot arm controller, and parallel connection platform controller, respectively, and receives data to perform coordinated control.

[0023] In a preferred embodiment, a 6-degree-of-freedom industrial robot arm is selected, which has high load capacity and positioning accuracy, and the repeatable positioning accuracy can reach ±0.05 mm. The maximum working radius is approximately 1.5 m, which can meet the machining needs of large workpieces such as bearing shells for sliding bearings.

[0024] In a preferred embodiment, the parallel connection platform utilizes a 6-degree-of-freedom parallel connection mechanism to achieve micron-level displacement control in three-dimensional space. The maximum adjustment range is a spherical space with a diameter of 300 mm, and the displacement accuracy can reach ±0.01 mm.

[0025] In a preferred embodiment, the laser cladding apparatus employs a high-power optical fiber laser with a maximum output of 10 kW and a wavelength of 1070 nm, and is equipped with a focusing mirror that allows adjustment of the laser spot diameter, with a spot diameter adjustment range of 1 to 10 mm, which can meet the needs of different cladding thicknesses and widths, and simultaneously provides stable output and rapid output adjustment capabilities, with an output adjustment range of 0 to 100% and an adjustment time of 0.1 s or less.

[0026] In a preferred embodiment, the femtosecond laser microfabrication module is equipped with a femtosecond laser having a central wavelength of 800 nm, a pulse width of approximately 30 fs, an adjustable frequency, a maximum single pulse energy of 1 mJ, and a beam shaping and focusing system, enabling micron-level processing accuracy, removal of bubble defects in the cladding layer, and finer, more uniform crystals.

[0027] In a preferred embodiment, the molten pool monitoring camera employs a monitoring camera (3D camera or depth camera) with a resolution of 1280 x 720 pixels, a frame rate of up to 30 fps, a measurement accuracy of ±1 mm, and infrared active illumination capabilities, which can operate normally in low-light environments and capture three-dimensional shape information of the molten pool in real time.

[0028] In a preferred embodiment, the contour scanning device is selected as a laser contour scanner, which can achieve a scanning speed of 12,800 points / second and a measurement accuracy of ±0.002 mm, enabling rapid acquisition of high-precision contour data of the bearing shell surface of the sliding bearing to be cladded and achieving comprehensive scanning of complex curved surfaces.

[0029] In a preferred embodiment, an industrial computer is used, possessing powerful data processing and control capabilities, and having multiple communication interfaces such as Ethernet, RS232, and RS485, enabling centralized management and cooperative control.

[0030] In a preferred embodiment, the robot arm 1 and the robot arm controller 4 are connected via a fieldbus to enable real-time transmission of motion commands and state feedback. The parallel connection platform 2 and the parallel connection platform controller 3 are connected via a motion control bus to ensure the motion control accuracy and real-time performance of the parallel connection platform 2. The robot arm controller 4, the parallel connection platform controller 3, the laser cladding device 5, the femtosecond laser microfabrication module 6, the molten pool monitoring camera 7, the contour scanning device 8, and the X-ray defect detector 10 are all connected to the computer 9 via an RS232 interface. The computer 9 acts as the core control unit, receiving state information and data feedback from each device, and transmitting control commands to each device to enable collaborative work.

[0031] In a preferred embodiment, the X-ray defect detection device 10 can detect images of the interior of the cladding layer and the interface between the cladding layer and the bearing shell of the sliding bearing to be cladded, thereby detecting whether or not bubble defects 17 exist in the interior of the cladding layer and the interface between the cladding layer and the bearing shell of the sliding bearing to be cladded.

[0032] As shown in Figure 8, embodiments of the present invention further provide a method for controlling a laser cladding system of a Babbitt alloy for sliding bearings having a free-form surface. The control method includes the following:

[0033] S1: Secure the bearing shells of the plain bearings to be cladded to the parallel connection platform.

[0034] Specifically, the bearing shells of the sliding bearings to be cladded are fixed to the work surface of the parallel connection platform via a magnetic attraction fixture. Initially, the origin of the platform coordinate system of the parallel connection platform and the origin of the base coordinate system of the robot arm are aligned through calibration. The computer sends an initialization command to the parallel connection platform controller to position the parallel connection platform at the horizontal zero position, sets the feedback values ​​of each support leg displacement sensor of the parallel connection platform to 0 mm, and awaits subsequent position and orientation adjustments.

[0035] S2: Set the output, wire feed rate, defocus amount, and scan rate of the laser cladding device.

[0036] Specifically, in this embodiment, the output is set to 1800W, the wire feed speed to 2m / min, the defocus amount to +3mm, and the scanning speed to 8mm / s.

[0037] S3: Using a contour scanning device, the surface of the bearing shell of the sliding bearing to be cladded is scanned, and the computer is used to acquire 3D model data of the bearing shell of the sliding bearing to be cladded.

[0038] S4: On the computer, a cladding path is set based on 3D model data, and the surface normal vectors of each cladding path point are calculated synchronously. The surface normal vectors are defined as having a positive direction toward the inside of the bearing shell of the sliding bearing to be cladded, and the surface normal vectors are associated with the cladding path points and saved as cladding path data on the computer.

[0039] S5: Use the robot arm controller to drive the robot arm and move the laser cladding equipment above the initial cladding path point.

[0040] Specifically, the robot arm, under the control of the robot arm controller, positions itself in cooperation with a 6-axis force sensor at the end of the robot arm, moving the laser cladding device directly above the initial cladding path point at a translational speed of 50 mm / s, while ensuring that the deviation between the laser direction of the laser cladding device and the surface normal vector of the initial cladding path point is less than 0.1°.

[0041] S6: The robot arm controller drives the robot arm to move along the cladding path. When the robot arm moves above a cladding path point, the computer retrieves the surface normal vector of that cladding path point and drives the robot arm via the robot arm controller to reduce the deviation between the laser direction of the laser cladding device and the surface normal vector of that cladding path point to less than 0.1°. Next, cladding is started, and the molten pool monitoring camera monitors the molten pool shape of the cladding layer at the cladding path point. Point cloud data of the molten pool shape is sent to the computer to calculate the width of the molten pool. If the width of the molten pool exceeds a first threshold, the computer sends a signal to reduce the output and scan speed of the laser cladding device. If the width of the molten pool is less than a second threshold, the output and scan speed are increased. Furthermore, the computer determines the lateral displacement angle and direction of the molten pool at the cladding path point based on the point cloud data of the molten pool shape. If the lateral displacement angle of the molten pool is greater than the angle threshold, the parallel connection platform controller drives the parallel connection platform to rotate the bearing shell of the sliding bearing to be cladded in the opposite direction to the lateral displacement direction of the molten pool by the lateral displacement angle of the molten pool. This reduces the lateral displacement of the molten pool at the next cladding path point, optimizes the molten pool shape at the next cladding path point, and updates the surface normal vector of each cladding path point. During cladding at the cladding path point, the X-ray defect detector detects images in real time of the inside of the cladding layer and the bonding interface between the cladding layer and the bearing shell of the sliding bearing to be cladded, transmits these images to the computer for processing, and identifies bubbles with an area greater than the area threshold. If a bubble defect is identified, it is determined that a bubble defect exists, and at this time, the femtosecond laser microfabrication module emits a laser to remove the bubble defect.

[0042] Specifically, the molten pool monitoring camera monitors the molten pool shape, generates point cloud data at 200 frames per second, with a point cloud density of 0.2 mm / point, and transmits the molten pool shape point cloud data to a computer via a GigE Vision interface. The computer performs noise reduction on the molten pool shape point cloud data using a bilateral filter, then reconstructs a 3D model of the molten pool with an accuracy of 0.05 mm. Next, it uses a thresholding algorithm to extract the edges of the molten pool and calculate its width. If the molten pool width exceeds 4 mm, the computer sends a voltage signal to the laser cladding device via an analog quantity output module, reducing the output at a rate (based on a proportional relationship) where 1% of the maximum output corresponds to 0.1 V. If the molten pool width is less than 3.5 mm, the output is increased at the same rate, with an output adjustment step width of 10 W. The scan speed is adjusted by pulse frequency control, with 100 pulses corresponding to a scan distance of 1 mm, and a speed adjustment step width of 0.1 mm / s.

[0043] Specifically, the parallel-connected platform controller rotates at an angular velocity of 0.1° / s after receiving an adjustment command for the lateral displacement angle of the molten pool, with a resolution of 0.01° for each axis encoder and an angular positioning accuracy of ±0.05°.

[0044] Specifically, the computer obtains the surface normal vector of the geometric center point of the molten pool based on a 3D model of the molten pool. The positive direction is defined as the direction of the surface normal vector pointing towards the interior of the molten pool, and the angle between the surface normal vector and the surface normal vector at the current cladding path point is defined as the lateral displacement angle of the molten pool at the current cladding path point.

[0045] Specifically, the surface normal vector of the cladding path point is updated by rotating it in the opposite direction to the lateral displacement direction of the molten pool by the corresponding lateral displacement angle of the molten pool.

[0046] Specifically, the femtosecond laser microfabrication module outputs a pulsed laser with a pulse width of 30 fs, scans the bubble defect region point by point at a repetition frequency of 100 kHz and a speed of 100 μm / s, controls the single pulse energy to 50 μJ and the pulse interval to 20 μm, and ensures that the surrounding cladding layer is not damaged during the bubble defect removal process.

[0047] S7: Step S6 is repeated until the robot arm has traveled along the cladding path to all cladding path points, forming a cladding layer on all cladding path points on the surface of the bearing shell of the sliding bearing.

Claims

1. A laser cladding system for Babbitt alloy for free-form surface sliding bearings, comprising a robotic arm and a laser cladding device, further comprising a parallel connection platform, a femtosecond laser microfabrication module, a molten pool monitoring camera, a contour scanning device, and an X-ray defect detector, wherein the contour scanning device is mounted on the end of the robotic arm and is for scanning the surface contour of the bearing shell of the sliding bearing to be cladded; the laser cladding device is mounted on the end of the robotic arm and is for performing laser cladding on the bearing shell of the sliding bearing to be cladded; the femtosecond laser microfabrication module is mounted on the end of the robotic arm and is for removing bubble defects in the cladding layer and at the bonding interface between the cladding layer and the bearing shell of the sliding bearing to be cladded; and the molten pool monitoring camera is mounted on the end of the robotic arm. A laser cladding system for a Babbitt alloy for a sliding bearing having a free-form surface, characterized in that the X-ray defect detector is attached to the end of the robot arm and is for detecting bubble defect conditions within the cladding layer and at the bonding interface between the cladding layer and the bearing shell of the sliding bearing to be cladded, the parallel connection platform is for placing the bearing shell of the sliding bearing to be cladded, the robot arm controller is electrically connected to the robot arm, the parallel connection platform controller is electrically connected to the parallel connection platform, and the computer is electrically connected to the contour scanning device, the laser cladding device, the femtosecond laser microfabrication module, the molten pool monitoring camera, the X-ray defect detector, the robot arm controller, and the parallel connection platform controller, respectively.

2. A laser cladding system for a Babbitt alloy for a sliding bearing having a free-form surface, as described in claim 1, characterized in that the laser cladding device employs an optical fiber laser, the femtosecond laser microfabrication module employs a femtosecond laser, and the contour scanning device employs a laser contour scanner.

3. The laser cladding system for a Babbitt alloy for a sliding bearing having a free-form surface, according to claim 1, characterized in that the molten pool monitoring camera employs a 3D camera or depth camera having an infrared active illumination function.

4. Step S1 involves fixing the bearing shell of the sliding bearing to be cladded to the parallel connection platform, Step S2 involves setting the output, wire feed speed, defocus amount, and scan speed of the laser cladding device. Step S3 involves scanning the surface of the bearing shell of the sliding bearing to be cladded using a contour scanning device, and having a computer acquire 3D model data of the bearing shell of the sliding bearing to be cladded. Step S4 involves setting a cladding path on a computer based on 3D model data, synchronously calculating the surface normal vector for each cladding path point on the cladding path, defining the surface normal vector as positive in the direction toward the inside of the bearing shell of the sliding bearing to be cladded, and saving the surface normal vectors in association with the cladding path points as cladding path data on the computer. Step S5 involves driving the robot arm using a robot arm controller to move the laser cladding device above the initial cladding path point, and making the deviation between the laser direction of the laser cladding device and the surface normal vector at the initial cladding path point less than 0.1°. The robot arm controller drives the robot arm to move along the cladding path. When the robot arm moves above any cladding path point, the computer retrieves the surface normal vector of that cladding path point and drives the robot arm via the robot arm controller to reduce the deviation between the laser direction of the laser cladding device and the surface normal vector of that cladding path point to less than 0.1°. Then, cladding is started, and a molten pool monitoring camera monitors the molten pool shape of the cladding layer at that cladding path point. Point cloud data of the molten pool shape is sent to the computer to calculate the width of the molten pool. If the width of the molten pool exceeds a first threshold, the computer sends a signal to reduce the output and scan speed of the laser cladding device. If the width of the molten pool is less than a second threshold, the output and scan speed are increased. Furthermore, the computer performs cladding based on the point cloud data of the molten pool shape. Step S6 involves determining the lateral displacement angle and direction of the molten pool at the path point, and if the lateral displacement angle of the molten pool is greater than the angle threshold, the parallel connection platform controller drives the parallel connection platform to rotate the bearing shell of the sliding bearing to be cladded in the opposite direction to the lateral displacement direction of the molten pool by the lateral displacement angle of the molten pool, thereby reducing the lateral displacement of the molten pool at the next cladding path point, optimizing the molten pool shape at the next cladding path point, and updating the surface normal vector of each cladding path point. During cladding at the cladding path point, the X-ray defect detector detects images in real time of the inside of the cladding layer and the bonding interface between the cladding layer and the bearing shell of the sliding bearing to be cladded, and transmits them to a computer for processing. If a bubble with an area greater than the area threshold is identified, it is determined that a bubble defect exists, and at this time the femtosecond laser microfabrication module emits a laser to remove the bubble defect. A method for controlling a laser cladding system for a Babbitt alloy sliding bearing having a free-form surface, according to claim 1, 2, or 3, comprising: repeating step S6 until the robot arm has traveled along the cladding path to all cladding path points, thereby forming a cladding layer at all cladding path points on the surface of the bearing shell of the sliding bearing, in addition to step S7.

5. Control method for a laser cladding system for a Babbitt alloy for a free-form sliding bearing, as described in 4, characterized in that the bearing shell of the sliding bearing to be cladded is fixed to the work surface of the parallel connection platform via a magnetic attraction jig, in the initial state the origin of the platform coordinate system of the parallel connection platform and the origin of the base coordinate system of the robot arm are aligned by calibration, the parallel connection platform is at the horizontal zero position, and the feedback values ​​of each support leg displacement sensor of the parallel connection platform are all 0 mm.

6. A control method for a laser cladding system for a Babbitt alloy for a sliding bearing having a free-form surface, as described in claim 4, characterized in that a molten pool monitoring camera monitors the shape of the molten pool, transmits point cloud data of the molten pool shape to a computer, the computer performs noise reduction on the point cloud data of the molten pool shape using a bilateral filter, then reconstructs a three-dimensional model of the molten pool, then extracts the edges of the molten pool using an adaptive threshold division algorithm and calculates the width, if the width of the molten pool exceeds 4 mm, the computer transmits a voltage signal to the laser cladding device via an analog quantity output module and reduces the output at a rate corresponding to 1% of the maximum output to 0.1 V, if the width of the molten pool is less than 3.5 mm, increases the output at the same rate, sets the output adjustment step width to 10 W, adjusts the scan speed by pulse frequency control, sets 100 pulses to a scan distance of 1 mm, and sets the speed adjustment step width to 0.1 mm / s.

7. A control method for a laser cladding system for a Babbitt alloy sliding bearing having a free-form surface, as described in claim 4, characterized in that a computer obtains a surface normal vector of the geometric center point of the molten pool based on a three-dimensional model of the molten pool, the direction of the surface normal vector is positive when it is directed towards the interior of the molten pool, and the angle between the surface normal vector and the surface normal vector at the current cladding path point is defined as the lateral displacement angle of the molten pool at the current cladding path point.

8. A control method for a laser cladding system of a Babbitt alloy for a sliding bearing having a free-form surface, as described in claim 4, characterized in that the surface normal vector of the cladding path point is updated by rotating it in the opposite direction to the lateral displacement direction of the molten pool by the lateral displacement angle of the molten pool.

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