The Research Of High Quality Tool-path Planning For Five Axis High Speed Machining

Five axis NC machining has become an important means of efficient processing of complex surface parts, it can improve the tool accessibility mainly by changing the cutter axis direction, and avoid the interference between the tool and workpiece. A dual NURBS tool path fairing method meeting the given fitting accuracy and reaching G1 continuity is proposed for the linear tool path in work coordinate system(WCS). The main contents of this paper and the innovatory results are listed as follows:Firstly, The paper studies the tool envelope surface expression formed by the tool interpolation from the line geometry and dual-quaternion. On the basis of the theoretical analysis and precision control, the linear tool path in WCS is fitted with dual-quaternion B-spline vector function in order to obtain the dual-NURBS tool path describing the locus of tool tip point and tool axis point. Simulations show that the linear tool path in WCS is smoothed by using the proposed algorithm to obtain a dual NURBS tool path fitting precision and reaching G1 continuity.Secondly, the isometric double-NURBS, which one was the NURBS curve of axis points and another was the NURBS curve of cutter center points, was generated by discrete tool path data to describe the five-axis tool path. In order to solve the problem that the distance between the two NURBS curves may not be equal, a method of gaussian spherical optimization of cutter axis vector NURBS curve was proposed. The isometric double-NURBS was generated by a method of optimizing cutter axis vector of NURBS curve on the gaussian sphere, then the parameter of the double-NURBS may be not synchronous. Therefore, a parameter synchronous model of isometric double-NURBS tool-path was proposed to solve this problem which double-NURBS curve parameter was not synchronization in the process of five-axis machining interpolation. Simulation results show that the proposed algorithm can generate dual-NURBS tool path and the precision of synchronous interpolation model achieves the accuracy of 10-5 mm degree and mainly in the 10-6 mm degree therefore, it is suitable for complex surface in five-axis machining.Thirdly, through analysising the motion trajectory of dual-NURBS tool path in five-axis machining, the speed distribution of cutter rational ruled surface is derived at any instant and a kinematic model of cutting edge element is established. For any given five-axis machine tools and the axis servo capacity constraints, the relationship between the machine tool’s speed, acceleration and feed rate is derived at dual NURBS interpolation to make the output command of interpolation device not exceed the axis machine tool servo ability.The isometric double NURBS tool path is available in the practical applications. It not only can decrease frequent acceleration or deceleration and improve the stability of machining processes to enhance the cutting efficiency, but also can make accurate and smooth sculpture surfaces. So, the isometric dual NURBS tool path will be widely applied in the manufacturing industry.