Research On Robot Trajectory Planning Of Three-dimensional Stone Carving Based On Grinding Force Constraint

Stone carving is the perfect combination of stone and carving art.It has always recorded the development of world civilization and has high artistic and cultural value.The three-dimensional stone carving has a complex outline structure and a variety of curved surface configurations,showing more abundant information,thus becoming a stone product with high added economic value.In recent years,processing equipment represented by robots has shown great advantages in workpiece size,processing efficiency and modeling flexibility,which can greatly replace manual labor and reduce labor costs.Three-dimensional stone carving processing is generally divided into two main processes: roughing and finishing.In rough machining,a large amount of material is removed,high machining efficiency is required,and the dynamic characteristics of grinding force change greatly;in finishing,the low rigidity part has poor manufacturability and improper control of grinding force,which can easily lead to the fracture of the stone blank and cause the workpiece to be scrapped..The state of the intermediate blank obtained after roughing will also directly affect the subsequent finishing.Therefore,for roughing and finishing,the use of uniform trajectory processing is not conducive to improving the removal efficiency,and is not conducive to the processing quality of the surface.This subject takes the white marble three-dimensional stone carving as the research object,studies the influence of the model shape of the intermediate blank after rough machining on the grinding force during the finishing process,and analyzes the variation law of the standard deviation of the three-dimensional stone carving processing force in different processing trajectories;in order to reduce the finishing process The grinding force fluctuation of the process is the goal to determine the optimal machining trajectory for finishing,so as to achieve the improvement of the machining quality of the three-dimensional stone carving surface.The main contents and results of this paper are as follows:(1)Partition planning of three-dimensional stone carvings according to curvature characteristics.The non-uniform rational B-spline surface model is used to establish the surface geometric feature model of the three-dimensional stone sculpture,and the surface is preliminarily divided according to the curvature information of each point on the surface;the clustering center of each sub-region is found by the paste clustering algorithm;the Voronoi diagram is used to determine each sub-region.Subregion boundaries;complete zoning planning.The corresponding model is established according to the divided surface type.(2)A three-dimensional stone carving intermediate blank model was established.The composition and specific process flow of the industrial robot three-dimensional stone carving processing system are introduced;on this basis,a white marble material model is established in the Production Module 3D software through calibration experiments;the state of the intermediate blank model under different processing trajectory parameters is obtained by simulation;And the fluctuation of the grinding force in the finishing process is used as the evaluation index,and the influence of the state of the intermediate blank model on the quality of the finishing process is studied.(3)The influence of different tool paths in the finishing stage on the fluctuation of grinding force and machining efficiency is analyzed.Four commonly used tool path formation mechanisms in the finishing process of three-dimensional stone carving are expounded;the machining process of different tool paths under the standard surface is simulated,and the optimal matching relationship between different finishing tool paths and the fluctuation of grinding force and machining efficiency is obtained;The influence law of the fluctuation value of grinding force on the contour error of three-dimensional stone carving is studied.(4)Finishing simulation and verification of specific three-dimensional stone sculpture models.Fangshan white marble was selected as the blank,and the reliability of the simulation was verified by experimentally machining the convex cylindrical surface and comparing the grinding force.Use the optimal roughing path parameters to process the blank to obtain the intermediate blank model;use the partition algorithm to divide the thin-walled part into 6 processing areas;use the weighted method to select the optimal process parameters and the optimal tool path.Simulation comparison using traditional machining method and optimized partition machining method.The results show that the grinding force fluctuation is reduced by 33.3%,the maximum grinding force is reduced by 61.9%,and the surface contour error after machining is reduced by 42.8%.The research results of this paper provide theoretical basis and practical application value for precision machining of weak rigid parts in robotic three-dimensional stone sculptures.