Research On Fixture Design System Based On Fixturing Case Reasoning

As a traditional tooling equipment, fixture is essential in a typical mechanical manufacturing enterprise. Fixture design and process planning are always relied on each other, the design efficiency and quality of them are crucial for controlling the cycle of new product introduction as well as determining the success of a new product trial and quickly transferred to mass production. The purpose of computer-aided fixture design is to build a tooling preparation system which can promote the rapid manufacturing of new product, so that to achieve fixture planning development,efficacy and visual assembly. For the shortage of some current fixture design system, Automatic feature extraction, case representation and case retrieval technologies which used for fixture design have been studied. A fixturing case-based reasoning fixture design system is developed based on UG secondary development techniques. The main research is as follows:The real impact factor to fixture design in the fixturing case representation model is explored from new entry point contrast with process decision. A set of fixturing case representation model have been proposed base on shape, positon and topology of fixturing feature, which are different from the previous overall feature modeling. Part features automatic extraction algorithms are discussed and realized. A case representation method based on the hybrid of framework and coding techniques is proposed to represent the basic part, process and fixturing feature information.The candidate locating datum and locating mode inference rules are summarized. For fixture planning, candidate locating datum sorting optimization methods have been proposed based on the Analytic Hierarchy Process. Judgment maxtrix construction process achieves a change from qualitative comparative analysis to quantitative calculation based on the Standard Deviation method and Menbership Degree theory, so that to avoid the impact of experience-dependent in the process of importance comparison and weight determination of locating datum factors. At last, the optimal locating scheme is deduced.By studing the typical case retrieval mechanism, a hierarchical case retrieval mechanism is proposed based on boundary locating face set matching theory and nearest neighbor strategy. system start to index case based on the overall part information and process information in the first stage; then start case similarity retrieval based on shape and position information of lcocating datum set that to narrow the scope of optimal case, at last retrieve based on the topology of locating datum set.The fixturing case-based system structure is proposed and developed based on UG 7.5 and ACCESS database technology, at the same time a User interactive Interface is created. Finally, an case example is given to verify the feasibility of system.