Research On The Scheme Design Methodology For Machining Centers Based On Topological Structure And Tool Changing Motion Characteristics

The theoretical basis of this research is the topological, kinematical characteristics of mechanisms and the analysis of kinematical chain configuration. The main objects are four- five-axis machining centers with tool change arm and without tool change arm. We study their topological, motion characteristics and kinematical chain configurations, and then present a systematical creative scheme design method for open-chain mechanisms like as machining centers with or without automatic tool changers.First of all, starting by investigating and collecting the relevant literatures and existing implements of machining centers, we introduce mechanism allocation matrix and tree-graph theory to analyze and conclude the topology and motion characteristics. This work serves as the basis of mechanism motion synthesis and scheme design of machining centers. Then, analyzing the kinematical chain design requirements and restricts of machining centers from the view of mechanism kinematical chain, combining with the characteristics of topology and tool change motion of machining centers, we present a creative scheme design method for machining center. By this method, the atlas of creative mechanism for machining centers is given systematically. On the analysis process of kinematical chain of machining centers, we discussed their workspace briefly. In this paper, some evaluating methods for tool changing time of automatic tool change on machining centers are discussed in detail, and a more reasonable and practicable calculating and evaluating method for automatic tool changer is proposed.The first step of the design method starts by investigating existing mechanisms and concludes their topology and motion characteristics; the second step is to describe the topological structures of existing mechanisms based on the coordinate systems and tree-graph representations; the third step is to transform these mechanisms into their corresponding generalized tree graphs according to the process of generalization; the fourth step is to obtain all possible tree graphs with the given numbers of edges and vertices based on graph enumeration; the fifth step is to assign certain type of links and joints into available tree graphs subject to required topology constrains through the process of specialization; the last step of the design process is to obtain the atlas of mechanisms subject to specified motion constrains.According to the concept of coordinate systems, graph theory, generalization, specialization, and motion synthesis, we use the design methodology synthesize the configurations of machining center with automatic tool changers. As the result, for the machining centers with the drum type tool magazine, the number of configurations of four-axis machining centers with 7, and 8 links are...