基于密切曲率法的汽轮机叶片数控加工

Numerically Controlled Machining of Steam Blade by Curavture Catering Method

为了提高汽轮机叶片数控加工的质量和效率，用2×3次非均匀有理B样条方法，建立了叶片的数学模型，推导了其三维点和法矢量矩阵表达式，实现了叶片的数字化表示。在此基础上利用密切曲率法，即采用中凹的盘形铣刀取代传统的球头铣刀，在每一次行程中，使刀具轴线绕工件的旋转轴线按特殊的规律摆动，使得在垂直于进给方向的法截面中，刀尖轨迹的包络面的法截线与理论曲面的法截线具有相同的1阶～2阶导数，从而在保持精度不变的前提下，使实际行程次数得以大幅度地减少，提高加工效率。

The mathematical model of steam vane is established with 2× 3 degree nurbs method to improve the quality and efficiency of vane machining. The expression of three - dimensional point and unit vector matrix are put forward and the numeric show of vane is realized. By means of using a disc cutter with a concave end instead traditional ball-ended or flat - ended ones, and adjusting the cutter axis to move relatively to the component being machined according to some special rules, the envelop formed by the trace of the tool-nose in each pass and the required surface have the same derivatives up to the second order in the plane normal to the feeding direction. Thus the machining width in each tool pass increases greatly and efficiency is raised highly while the same accuracy is guaranteed.