基于装配的计算机辅助公差设计主要包括公差表达、公差链的生成、公差分析和公差综合四个部分。公差链的生成是其余三部分的基础。本文在实体关系模型的基础上研究了装配尺寸链的自动生成算法 ,在一维尺寸链生成算法中提出基于搜索方向的配合关系图生成的新算法。该算法中加入了配合关系方向性的取舍 ,降低了配合图生成的复杂度 ,同时该算法可以判断关系设计的冗余性 Assembly-based computer-aided design of tolerance mainly includes four parts: tolerance expression, tolerance chain generation, tolerance analysis and tolerance synthesis. Tolerance chain generation is the basis of the remaining three parts. Based on the entity relation model, this paper studies the automatic generation algorithm of assembly dimension chain, and proposes a new algorithm for generating the cooperation relation graph based on the search direction in the one-dimensional dimension chain generation algorithm. In this algorithm, the choice of the direction of cooperation is added, which reduces the complexity of the production of the cooperation graph and at the same time, the algorithm can judge the redundancy of the relationship design