基于最小DFS编码的夹具设计学习重用算法

发布时间：2018-03-17 17:31

本文选题：DFS编码　切入点：最大同构子图　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：企业在加工过程中首先面临的是装夹工件的问题,这个过程直接影响了产品的质量,而工件装夹的质量取决于夹具的设计。也就是说夹具设计的质量和效率直接影响了企业产品的质量和生产效率。在生产制造中,企业不断的追求更好的质量、更高的效率和最低的成本。这样他们才能够在全球化的市场竞争中得以生存,得以发展。在整个加工过程中,夹具设计时间占整个加工周期的35%-50%左右,从提高夹具设计效率方面来缩短加工周期显得非常重要。然而传统的夹具设计最为典型的是类比法和经验法,这些方法不但成本高、效率低,而且夹具的使用范围及其有限。难以达到小批量、多品种的市场要求,难以达到CAD/CAPP/CAM集成的要求。另外,现代加工中常常出现待加工工件尺寸大、定位准确性和协调性差、容易变形等情况,这使得夹具设计工作难上加难。所以打破传统思维方式,探索新的高效率的夹具设计方法迫在眉睫。大量的夹具设计案例为夹具设计提供了可重用的经验和知识,为实现夹具快速设计奠定了基础,而准确的检索到相同或者相似的夹具设计案例则是实现夹具快速设计的核心与关键.为此,本文根据零件B-rep表示的实体模型,通过特征之间的几何拓扑关系构造零件的标号图.结合标号图的线性顺序性和扩展延续性,提出了特征标识的确定原则,构建了最小DFS编码的遍历流程.针对新零件的最小DFS编码与夹具案例的最小DFS编码,提出同构子图的挖掘方法,在建立零件相似度和图集相似度的基础上,进一步提出最大同构子图的判断标准.最后通过挖掘零件的装夹特征及自身几何关系的最大同构子图,以装夹特征的最大同构子图为优先准则,完成新零件与夹具图集的准确匹配,实现夹具的快速设计过程.
[Abstract]:In the process of processing, enterprises are first faced with the problem of clamping workpieces, which has a direct impact on the quality of products. The quality of workpiece clamping depends on the fixture design. That is to say, the quality and efficiency of fixture design directly affect the quality and production efficiency of enterprise products. Higher efficiency and minimum cost. So they can survive and develop in the global market competition. In the whole process, fixture design time is about 35-50% of the whole processing cycle. It is very important to shorten the processing cycle in order to improve the efficiency of fixture design. However, the traditional fixture design is the most typical method of analogy and experience, these methods are not only high cost, but also low efficiency. Moreover, it is difficult to meet the requirements of small batch, multi-variety market and CAD/CAPP/CAM integration. In addition, in modern machining, the size of workpiece to be processed is large, the positioning accuracy and coordination are poor. Easy to deform and so on, which makes the fixture design more difficult. So break the traditional way of thinking, It is urgent to explore new and efficient fixture design methods. A large number of fixture design cases provide reusable experience and knowledge for fixture design and lay a foundation for rapid fixture design. However, retrieving the same or similar fixture design cases accurately is the core and key of rapid fixture design. Therefore, according to the solid model of B-rep representation of parts, Based on the geometric and topological relations between features, the label diagram of parts is constructed. Combining with the linear sequence and extended continuity of label graph, the principle of determining feature identification is put forward. The traversal process of minimum DFS coding is constructed. Aiming at the minimum DFS coding of new parts and the minimum DFS coding of fixture cases, a method of mining isomorphism subgraphs is proposed. Finally, the maximum isomorphism subgraph of the clamping feature and the maximum isomorphism subgraph of the geometric relation of the parts are excavated, and the maximum isomorphism subgraph of the clamping feature is taken as the priority criterion. Complete the accurate matching of new parts and fixture atlas, and realize the rapid design process of fixture.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG75

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