Study On Compound Tool Paths Generation Of Free-form Curve And Surface Numerical Control Machining

As to most programs given by CAM software, line interpolation and arc interpolation are the interpolations which are mostly used. Spline interpolation could be the powerful supplement for line and arc interpolation as its brevity and smoothness. Integrating several interpolations are significant to free-form curve and surface NC machining.A new approach to compound tool path generation based on discrete cutter locations is proposed. The mathematical model integrating line fitting, arc fitting and B-spline fitting is constructed. Through error analysis of three fitting methods, the iteration of different fitting methods and tool path segmenting could be carried out. Compound tool paths are produced.First, arc fitting and B-spline fitting are carried out based on least square method. The procedure for B-spline is divided into two parts. After the original control points being gotten on the uniform parameterization of data points, the parameter values are optimized to get new control points.Second, the method for selecting line fitting, arc fitting and B-spline fitting according to precedence level is given, implementing the combination of three fitting methods. The judgement of fitting error decides the iteration of different fitting methods. The line fitting method is definitely used when the points distance is beyond the set valve value in order deduce calculation.Third, reading cutter location points, the machining method consists of line interpolation, arc interpolation and B-spline interpolation is achieved. The compound tool paths are generated for planer machining. The compound tool paths integrating line and B-spline are used for surface machining. The optimized tool paths could advance stability for milling and shorten the time for continual speeding up and speeding down in order to increase efficiency, shorten machining time and improve the surface roughness.Comparing the parts using compound tool paths generating method to using original method, the surface quality and efficiency are both improved.