Research On Integration And Process Monitoring Of Multi-DOF Laser Cladding System Based On Machine Vision

As a particular light source,the laser has powerful advantages in four aspects:energy density,monochromaticity,directionality and coherence,and the laser cladding layer has superior corrosion resistance,abrasion resistance,fatigue resistance,and oxidation resistance.Therefore,laser Cladding has been widely used in the remanufacturing of mining equipment,large ships,metallurgical industry,and defense industry.However,the energy transferred in the laser cladding process is very complex and changeable in terms of mechanism.The quality of the cladding is affected by many factors such as processing parameters,matrix and powder material properties,external environment,and part size.The change of process parameters will have a more significant impact on the quality of cladding.It is essential to reasonably control the process parameters of laser cladding during the cladding process.To ensure the quality of the cladding,it is essential to monitor the quality of the cladding and control the process parameters in real-time during the processing.In response to the needs of scientific research and actual working conditions,this project uses Siemens PLC to integrate a robot laser cladding control system.It builds a realtime monitoring system for the molten pool based on a CCD camera,and cladding 316 L alloy powder on the H13 substrate in the process experiment,the characteristic relationship between the cladding defect and the molten pool image is analyzed.Moreover,by changing the cladding parameters and calculating the area of the molten pool,the correlation between the cladding speed,cladding power,cladding inclination,and the area of the molten pool was established.The main research contents are as follows:(1)PLC-based laser cladding control system integration.Due to the problems of low integration of existing laser cladding equipment,independent vision system,and complicated operation,a laser cladding robot system integration scheme based on S7-1200 PLC is proposed.The communication module and I/O port of S7-1200 PLC are used to integrate the laser,cooler,robot,powder feeder,etc.into an overall control system,and WINCC is used to create a human-computer interaction interface.PLC and PC communication is used to realize the combination of laser cladding control system and machine vision monitoring system,to achieve multi-degree-of-freedom laser cladding control and monitoring based on machine vision.(2)Research on real-time monitoring method of the molten pool based on machine vision.Aiming at the problems in repairing complex curved surfaces,a CCD-based coaxial monitoring method for six-degree-of-freedom laser cladding is proposed.In laser cladding,in the process of image acquisition,transmission,and conversion,the weld pool image will be disturbed for many reasons,so this paper compares a variety of filtering algorithms and chooses a median filter to eliminate noise interference.Moreover,through threshold processing and image segmentation to obtain the ideal area.To meet the need to incline the laser to a certain angle during the cladding process,the shape parameters of the molten pool are converted into vertical cladding shape parameters according to the spatial coordinate conversion of the inclination angle.Since the shape of the molten pool monitored during the cladding process is irregular,this paper uses an edge detection algorithm to extract the edge contour of the molten pool and obtain the area characteristics of the molten pool image.After the algorithm verification is completed,the software platform is constructed under the Win Forms architecture using C# language and Halcon vision algorithm package.(3)Research on the relationship between the quality of laser cladding and the image characteristics of the molten pool.To explore the characteristic relationship between the quality of the cladding and the image of the molten pool,image processing technology is used to analyze the relationship between the different defects and the area of the molten pool during the cladding process,as well as the change in power,tilt angle,and speed.Under different process parameters,through the real-time acquisition of molten pool images,the area of the molten pool is calculated to analyze the influence of different process parameters on the area of the molten pool.According to the actual project needs,this thesis completed the construction of a laser cladding system integration and visual monitoring system.On this basis,the cladding quality was analyzed experimentally,which improved the equipment foundation and verified the research of laser cladding surface repair technology-the feasibility of the visual monitoring method.The paper has 63 pictures,16 tables,and 85 references.