汽车轮毂柔性加工夹具的定位误差分析

Analysis on the positioning error of the automotive wheel hub’s flexible machining fixture

定位误差分析是夹具设计过程中的重要环节,直接影响到被加工工件的加工质量和生产成本。针对所设计的汽车轮毂柔性加工夹具,提出一种夹具误差映射模型;建立了机床坐标系、轮毂加工夹具坐标系和工件坐标系,得出了夹具定位元件尺寸公差和工件位置与姿态误差之间的函数关系。在忽略其他影响因素(如切削温度、变形、刀具和机床加工精度等)对轮毂加工精度影响的情况下,以18英寸的汽车轮毂为例,由轮毂给定的加工精度,基于误差映射模型,运用MATLAB软件对汽车轮毂柔性加工夹具定位元件的尺寸公差进行了计算,得出了夹具定位元件的尺寸误差范围,对夹具定位元件公差进行合理的分配、提高夹具设计制造的效率具有重要意义。

Analysis on positioning error is an important part of the fixture’s design process,which directly affects processing quality and production cost of the workpieces being processed. In this article,aiming at the automotive wheel hub’s flexible machining fixture,a machine-tool coordinate system,a hub machining-fixture coordinate system,and a workpiece coordinate system are developed. Through the homogeneous coordinate conversion among these coordinate systems,the fixture’s error-mapping model is set up,and fixture positioning is ensured. The functional relationship among the following factors is identified: component dimensional tolerance,workpiece positioning,and workpiece pose. When the effect of the other influencing factors (such as cutting temperature,deformation,machining accuracy of tools and machine tools,etc.) on the machining accuracy of the wheel hub is neglected,with the 18-inch automotive wheel hub an the example,the dimensional tolerance of the fixture’s positioning elements is calculated and the range of size error is obtained,based on the error-mapping model,by means of the MATLAB software. It is of great significance to reasonably allocate the tolerance of the fixture’s positioning elements and improve the efficiency of fixture design and manufacturing.