Case-based agile fixture design

Abstract

In this paper, the general situation of research on agile fixture design is summarized and the achievements and deficiencies in the field of case-based fixture design are pointed out. There are no correlative case bases and matching mechanisms during the period from establishing the fixture planning to designing the fixture in currently used case-based fixture design systems. Thus a great amount of experience of fixture design is wasted and cannot be re-used, which reduces design efficiency and violates the original intention of case-based reasoning methods. In order to realize agility of fixture design, including re-configurability, re-scalability and re-usability, in this paper, a re-configurable agile fixture element base and an element assembly relation base are established. Using these two bases, the fixture structure is function-based decomposed, which makes it easy for an agile fixture to be re-configured and modified. Furthermore, a whole case-based agile fixture design model is presented, in which three modules are introduced, including the evaluation of the similarity of fixture planning, conflict arbitration and the modification of an agile fixture case. The three modules can be used to solve a problem where experience and design results cannot be re-used in the process of fixture design. Against the agile fixture design model, the evaluation method is put forward to evaluate the similarity in various phases. However, a similar case in the base could not generally meet the actual requirement and resolve the conflict between the similar case and the actual condition. Thus three methods, including a local restriction-relaxed method, a function-based conflict arbitration method and a case-based conflict arbitration method, are presented to clear up the conflict and could be used to modify the case to obtain an approach to a design result. Finally, an agile fixture design example is presented. The result demonstrates that the case-based agile fixture design approach can improve re-usability and design efficiency.