三维装配尺寸链的自动生成

提出了一种基于CAD模型的三维装配尺寸链自动生成方法。该方法从定义装配性能特征入手,首先对CAD装配模型进行深层次的解析及预处理,以获取隐含在模型内部的公差分析所需信息。然后利用图论理论,通过构建特征-尺寸邻接矩阵、特征-装配约束关系邻接矩阵、装配关系传递图等,将装配体中参与装配的零件和特征以及其之间的装配约束关系、尺寸及形状等信息的传递过程以图的形式进行表达。最后将三维尺寸链分为显式和隐式两类,对于显式尺寸链,由装配关系传递图搜索连通通路可直接获取尺寸链图和方程:对于隐式尺寸链,提出了尺寸方向差异度的概念、封闭环方向优先的搜索策略以及构建过渡尺寸链的方法,最终可获取尺寸链图和方程。该方法已在自主开发的三维装配尺寸链自动生成系统中得到了验证。

AUTOMATIC GENERATION OF 3D AS SEMBLY DIMENSION CHAINS

An automatic generation method of 3D assembly dimension chains is proposed based on 3D CAD models. Starting with the definition of assembly performance feature (APF), CAD models are deeply analyzed and pre-treated to get the data hiding in the models needed by tolerance analysis. Then based on graph theory, feature-dimension adjacent matrixes, feature-assembly constraint type adjacent matrixes and assembly relation transfer graphics (ARTG) are built, which can express the information transfer process of parts, features, assembly constraints and dimensions in an assembly. Finally, 3D assembly dimension chains are classified into two types, explicit and implicit chains. For explicit chains, tolerance chain graphs and equations can be directly got from ARTG through searching connected routes. For implicit chains, the conception of degree of dimension direction unlikeness and the searching policy which gives priority to closing-loop-direction are proposed, and finally tolerance chain graphs and equations can be achieved by the method of building transition tolerance chain. The method is validated by our own-developed 3D assembly dimension chain automatic generation system.