S试件几何形状定义与特性分析

Geometry Definition and Properties Analysis of S-shape Test Piece

S试件是用于综合检测五轴数控铣床动态加工精度的检测试件,目前已申请纳入国际标准ISO 10791-7标准组作为附加测试件。S试件的型面由两个直纹面构成,但S试件草案中并未对S形直纹面的参数化方式进行详细指定,因而导致S试件的几何形状表达方式不唯一,不同的型面几何定义对试件的检测特性有重要影响。针对以上问题,本文给出了Nurbs参数和等弧长两种典型的S试件直纹面定义方法,对比分析了两种直纹面的扭曲角变化及侧铣原理性误差等特性,并根据分析结果选取Nurbs参数作为S试件直纹面定义方式,从原理上完善了S试件的几何定义,有利于S试件标准的推广。

As a test piece for detecting the dynamic accuracy of five-axis milling machine tools, S-shape test piece has been applied to ISO 10791-7 groups to be an international standard specimen. The profile of S-shape test piece is constituted by two ruled surfaces. However, the exactly parameterized method of ruled surfaces has not been included in the S-shape piece draft, which may cause the non-unique expression of S-shape test piece. Different definition methods of ruled surfaces may have important effects on the detecting characteristics of S-shape test piece. In order to address the above issue, two typical parametric definition methods of ruled surfaces are provided in this paper, which are iso-parametric method and arc length method. Furthermore,iso-parametric method is chosen as the profile definition method of ruled surface of S-shape test piece according to the analysis of the twist angle and the theoretical machining errors. The research improves the definition theoretically, which may be beneficial to the promotion of S-shape test piece.