夹具定位误差分析自动建模方法

Approach to Automated Modeling of Fixture Location Errors Analysis

提出一般夹具的定位误差分析模型建立方法。根据工件—夹具系统的误差形成和传递路线分析,将工件—夹具系统分为定位元件、定位基准、工序基准和加工特征等四个要素组成,通过求解四个要素之间的位置变动获得工件—夹具系统整体的定位误差。将四个要素之间的位置及其变动关系用连杆机构模型等价表示,工件—夹具系统转换为接触副等价机构、公差关系等价机构、工序尺寸等价机构等三个等价机构的组合。研究工件和夹具定位元件接触副与等价机构之间的映射关系的建立方法,研究定位基准与工序基准、工序基准与加工特征之间的尺寸与公差关系所对应的等价连杆机构的建立方法,研究采用机构的结构参数和运动参数表示工件—夹具系统的所有工序信息及其内在联系的方法。利用机构学的机构位置计算方法求解定位误差,实现定位误差分析的自动化。

The modeling method of fixture location error is proposed.By the analysis of location error transmit route,the workpiece-fixture system is defined as a composition of four elements,i.e.machining feature,process datum,location datum and locators.The fixture location errors are obtained by calculating the relative position variations among the four elements.The position variation relationships among the four elements are represented by link mechanism model.The workpiece-fixture system is composed by the contact pair equivalent mechanisms,tolerance equivalent mechanism and process dimension equivalent mechanism.The rules mapping from contact pairs to equivalent mechanism components are established,the modeling methods of the equivalent mechanisms of tolerance and process dimension are proposed,here,tolerance mechanism reflects the relationships between process datum and location datum,and process dimension mechanism embodies the relationship between process datum and machined surface,and the approaches to using mechanism structure motion parameters to represent the process information and the inner relationship of workpiece-fixture system are explored.According to the mapping rules mentioned above,the equivalent mechanism model is established automatically,and the automatic solution of location error can be realized by means of the position calculation methods of mechanism.