Application Of NURBS Curve In Plasma Arc Surface Treatment

Plasma arc surface treatment technology,as an advanced high-energy beam surface treatment technology,has many advantages due to its energy-saving and environmental protection,which greatly improves the surface performance of the workpiece,and its application range is getting wider and wider.In actual processing,in order to ensure the quality of plasma arc surface treatment,the distance between the plasma arc generator and the workpiece surface needs to be kept within a reasonable range.In order to meet the requirements of this process,the plasma arc generator needs to plan the motion trajectory of the plasma arc generator properly when processing special-shaped workpieces.Aiming at the actual needs of plasma arc surface treatment for special-shaped workpieces,this paper proposes a set of arc trajectory algorithms suitable for high-precision plasma arc CNC machining.Sometimes,due to the limitation of objective conditions,it is difficult to realize high-precision CNC machining of plasma arcs on the engineering site.In order to use plasma arcs to process special-shaped workpieces on site,this paper has designed a set of follow-up mechanisms in an attempt to achieve on-site follow-up processing of plasma arc surface treatment.For high-precision CNC machining of plasma arcs of special-shaped workpieces,first of all,a large number of data points are discretely obtained by CAM software,and the data point set is divided according to the constraints of the angle between the small line segments and the length ratio of the adjacent small line segments;according to three consecutive adjacent The restriction condition of the angle between the small line segments can identify and delete the problem points,and then obtain a reliable data point sequence.Secondly,on the basis of fuzzy division of discrete point sets,an algorithm for adaptively selecting basic interpolation points from the obtained data point sequence is proposed,and another part of basic interpolation points is selected according to the curvature information of the discrete point sets.Two parts of basic interpolation points construct the initial NURBS curve.In the process of continuously improving the accuracy of the NURBS curve by iterative method,an improved control point algorithm of "three points for two points" is proposed.Finally,a double arc spline is used to fit the NURBS curve,and the dichotomy and the longest step method used to adaptively divide the number of double arc segments are compared.For the engineering needs of large-scale special-shaped workpiece processing on site,a set of plasma arc follower mechanism was designed according to the principle of plasma arc surface processing.Based on the accuracy analysis,force analysis and prototype prototype operation experiment of the mechanism,the use of The principle of lever improves the connection parts of the universal follower of the original follower mechanism.The results show that the improved follower mechanism meets the processing requirements of large-scale shaped workpieces with a radius of curvature greater than 165mm.