Thermal Spray Robot Trajectory Planning And Experimental Research

Thermal spray technology consists of a series of processes,such as plasma spray,flame spray,arc spray and so on.In these processes,feedstock materials(e.g.,metals,alloys,ceramics,polymers and composites)are deposited onto a substrate surface in a molten or semi-molten state,and form a stacked layer with various functions.It can be used not only for product prevention,but also for regeneration and repairing of defective products.The main objective of thermal spraying process is to achieve the required coating thickness,but it is difficult to achieve this goal when the sprayed substrate is a complex freeform surface.The trajectory generation of thermal spraying robot was studied deeply in this paper,the mathematical models of cylinders and mathematical model of spheres were built,and corresponding experiments were conducted.The experimental results have shown the validity and accuracy of the models and achieved the ideal coating thickness of complex freeform surface.The construction technology of virtual simulation for thermal spraying was studied.Based on the Robot Studio software platform for Offline Programming by ABB Company,the parameterized model of thermal spraying gun was constructed by analyzing the characteristics of spray gun in robot workstation.The fixture tools library were designed combining the actual size of fixtures.According to the framework of real thermal spraying environment,we have deeply studied the designed process of thermal spraying virtual simulation environment,defined the construction of thermal spraying virtual simulation environment in different stages and built the virtual simulation environment of thermal spray.The mathematical models of coating thickness for thermal spraying were studied.In this paper,the method of establishing the single-pass coating thickness mathematical models of cylinders and spheres based on polar coordinate system and spherical coordinate system were proposed,respectively.Based on the analysis of characteristic parameters influencing the mathematical model of coating thickness and the cumulative coating thickness data of sampling points of pre-experiment,Gauss model on account of least squares method was used as empirical formula to fit the mathematical model.By means of constructing a coating profile model superimposing single-pass coating thickness,the calculation method of coating thickness at any point on coating profile was given in this paper.The application examples of thermal spray based on cylindrical and spherical substrates were presented,which have showed the validity and accuracy of the single-pass coating thickness mathematical models of cylinders and spheresThe trajectory generation for thermal spraying of non-holonomic cylinders was deeply studied.Based on the analysis of influencing factors spraying interval angle and radius of cylindrical workpiece,the distribution characteristics of coating thickness on cylindrical substrate were defined.Depending on the allowable coating thickness errors,the optimum spraying interval angle and the cycle numbers of spraying were determined,and the spraying path of the spraying gun was generated.Through the calibration of the path,it guarantees the robot will not collide with the peripheral equipment in the course of operation,and the feasibility of trajectory was verified.By calculating the maximum,minimum and average thickness of the coating on the substrate of spraying experiment,and the uniformity of coating profile was analyzed.The result has shown that the effectiveness and operability of thermal spraying trajectory based on the non-holonomic cylinders.The trajectory generation for thermal spraying of spheres was deeply studied.Based on the feature that the distance between adjacent longitudes on spherical workpiece decreases gradually with the increase of latitude from the equatorial plane,a method of generating spraying trajectory of spraying gun adopted uniformly variable motion along the longitude of spherical surface was presented.Distribution characteristics of coating thickness on spherical substrate were defined by analyzing the influence factors of azimuth angle of spraying interval and speed of spraying gun.According to the analysis of the absolute error and relative error values of coating thickness between simulation and experiment,it is clear that the errors are mainly caused by the change of deposition efficiency of powder deposited on spherical substrate and the loss of spraying material.Depending on the allowable coating thickness errors,the optimum azimuth angle of spraying interval and the cycle numbers of spraying were determined,and the spraying path was formed.Through the calibration of the path,it guarantees the robot will not collide with the peripheral equipment in the course of operation,and the feasibility of trajectory was verified.By calculating the coating thickness on the spherical substrate of spraying experiment,and the uniformity of coating profile was analyzed.The result has shown that the effectiveness and operability of thermal spraying trajectory based on the spheres.