Laser Cladding Molten Pool Morphology Monitoring And Cladding Process Research Based On Machine Visio

As an advanced material forming technology,laser cladding has the advantages of high processing flexibility,small thermal deformation,wide selection of materials and so on.It is widely used in aerospace,automotive industry,Marine ships,medical instruments and petrochemical industries.However,laser cladding process involves complex physicochemical metallurgy process,the quality of cladding layer is affected by many factors such as the characteristics of matrix and powder materials,processing parameters,external environment,and there is a complex coupling relationship between all factors,so in the actual production process has the shortcomings of unstable cladding quality,poor repeatability and low machining accuracy.To solve the above problems,this paper introduces the process monitoring technology in laser cladding process,takes the morphology of the molten pool as the monitoring signal,and studies the relationship between each cladding process and the size of the molten pool,which lays the foundation for the final closed-loop control of laser cladding.The content of this paper is summarized as follows:(1)In order to obtain clear images of the molten pool,a coaxial machine vision monitoring system for the laser cladding pool was built by assembling a CMOS camera and a laser head on the robotic arm without interfering with the laser beam transmission and the movement of the manipulator.The coarse detection of molten pool edge was realized by graying,filtering and denoising,threshold segmentation,morphological processing and Canny edge detection of collected molten pool image.In order to further improve the detection accuracy,the subpixel edge detection technology is proposed in this paper,that is,the traditional Zernike-moment edge detection algorithm is combined with the maximum inter-class variance algorithm,and the subpixel calculation is performed again on the basis of the Canny edge detection algorithm to obtain a higher accuracy of the melt pool edge location.Finally,the length and width of the molten pool contour were obtained by the minimum external rectangle algorithm.(2)The on-line monitoring system of molten pool is designed and developed to monitor the experimental process of orthogonal cladding.The cladding layer was cut along the section and measured under a high-power microscope.The results showed that there was a good correlation between the width of the actual cladding layer and the width of the monitored molten pool,and the size error was less than 5%.Then the data results were analyzed by range method,and the order of influence of cladding process parameters on the width of the molten pool was obtained as follows: laser power >scanning speed > powder feeding rate.(3)A multi-channel single-layer cladding experiment was designed by using the control variable method,and the relationship between laser power,scanning speed,powder feeding rate and characteristic parameters(width,length and area of the molten pool)was studied.The results show that the width,length and area of the molten pool increase with the increase of laser power and powder feeding rate,but decrease with the increase of scanning speed.