Automatic Recognition Of Features Interaction And It’s Applications On STEP-NC

Because of the industry’s urgent need, CAD/CAPP/CAM integration has become one ofmajor goals for the researcher. However, CAD, CAPP, CAM organic integration still faces manydifficulties.One of the difficulty is lack of intelligent conversion interface between CAD andCAPP. Currently, it uses the solid models or design features to represent the mechanical product.Although it capable generates feature models as its end result, lacks the necessary link to a CAPPsystem, simply because the design features do not always carry the manufacturing informationwhich is essential for process planning activities. Consequently, feature recognition is the bestchoice. There are many feature recognition systems have been exist already. Some of thesetechniques are know an, graph-based approach, hint-based approach, geometric decompositionapproach and composite of the two. Unfortunately, it still has not a mature feature recognitionsystem, on account of encountered bottleneck on the identification problem of featureinteractions.At the beginning of this century, the international standards organization published theSTEP AP224, as one part of the standard ISO10303protocol. It gives feature standardizeddefinitions, and belongs to product data definition of mechanical product data definition. Thenthe STEP-NC data model was released, which included feature-based machining technology.Although automatic feature recognition research on feature interactions is continue to be popularin recent years, there is very little research on dealing with feature interaction based on theSTEP-NC data model.This paper presents the feature recognition method started by the STEP AP203file an in put,based on graph and hint to recognize feature interactions, and output by the STEP AP238file atlast. The output file is not add with process information, but during the whole process, thestandard of STEP-NC data model is applied. This Feature recognition process involves theconstruction of machining feature adjacency graph, the judgment of feature interactions, the splitof feature interactions, the match of machining feature and presents machining feature bySTEP-NC said five components:(1) The construction of machining feature adjacency graph is characterized that: Firstly,imports the STEP AP203file into memory, converts into geometry entity object, and generatesface edge adjacency graph through traversing the object face and edge. Then, adds some relevantattributes for face and edge to form attribute adjacency graph. Finally, removes the contoursurface vertexes of attribute adjacency graph to generate the connected subgraph.(2) The judgment of feature interactions is characterized by determining the process toidentify whether it contains the convex side. Before the judgment, it should exclude thoseconvex side who is connected with the outer contour surface. (3) The split of feature interactions is characterized by creating an orderly split factor queueof feature interactions for feature base-face, then adding virtual link by the order queue to splitfeature interactions. The split factor takes into account characteristics of feature volume disjoint,the number of convex side of feature face, feature base-face priority and so on. From the resultwe can kown,it is better for the split of feature interactions.(4) The match of machining feature is characterized that through encoding the featurebase-face and storing in Sql Server2005, takes the use of current more mature database querytechnology to identify machining feature, and avoids the use of may be very time-consumingsub-graph matching algorithm. The feature base-face is those face which adjacent to the featureother side surface. If feature haven’t any base-face, such an through holes, it could be creating avirtual base-face by feature boundary edge-loop.(5) The machining feature of STEP-NC data model presentation is characterized that isdescribed by ISO10303-238standard protocol. This means that takes use of parameterization torepresents the machining feature and output by the STEP AP238file at last.