Manufacturing Feature Recognition from Solid Models

Abstract

Indiscrete part manufacturing a product undergoes a finite number of machining and assembly operations. When a finished design is passed to the manufacturing department, detailed instructions are required to convert the work material (blank) from its initial form to final form defined by an engineering drawing or product model. These detailed instructions required are known as process plan. So once the process planning phase has been completed, actual production of the part begins, according to instructions generated during the process planning. So the interface between the design and manufacturing is process planning - Today computer aided design (CAD) and computer aided manufacturing (CAM), have been implemented. Process planning is the critical bridge between design and manufacturing. In CAD/CAM Integration, computer aided process planning (CAPP) system plays a Key role between design and manufacturing. In a typical CAD/CAPP/CAM/ integration, there are two basic interfaces to be established, CAD/CAPP interface and CAPP/CAM interface. The former is accomplished by a "Feature Recognizer ", whereas the latter is achieved by an "NC part programme Generator" Informally, features are generic shapes or other characteristics of a part with which engineers can associate knowledge useful for reasoning about the part. These are many published, definitions of the concept of a feature. Even enough there definitions seem to be dissimilar, they are consider features as entities which are of semantically higher level than the pure geometric elements typically used in solid modeling systems. Features are generally be classified into three categories; design features, machining feature and geometric features. The geometric aspects of features are defined as volumes enveloped by a set of real and imaginary faces. Geometric elements are solid primitives in CSG type solid models (blocks, Cylinders, spheres, tore) or boundary elements used in B-Rep type solid models (faces, edges, vortices)- Almost Universally, the concept of generic feature classes is used and models are built from Instances of genetic features - The generic type may be organized into feature taxonomy, often realized as a collection of classes with in inheritance of information according to the principles of object-oriented programming. In the type - instance approach, feature instances are represented in terms of various feature attributes, common attributes include the intrinsic geometric attributes of shape corresponding to the feature (length, width, depth, radius), the position and orientation of the feature with respect to some global coordinate frame, geometric tolerances, material properties, references of the type. A manufacturing feature is commonly defined as a collection of related geometric elements which correspond to a particular manufacturing method or process, or which can be used to reason about the suitable manufacturing method or processes for creating that geometry. The Development of an automatic CAD/CAPP interface with the use of features has generally been proposed within the following two main philosophies; First is Design the part with solid modeling system and then manufacturing specific information is Retrieved from the geometrical Representation of component alone is known as Automatic Feature Recognition or Extraction. Second approach is Design the part with a feature-based modeling system and thereby incorporate manufacturing information in the model at the design stage is known as Feature Based Modeling. Automatic feature Recognition has been an active Research area in solid modeling for many years and is considered as critical component for integration of computer-Aided design and computer Aided Manufacturing(CAD/CAM).Advanced Computing methods used in feature processing include the use of Expert systems and Artificial Intelligence(AI) techniques ,so these techniques are also discussed in detail. This Thesis gives an overview of the state-of-the-art in feature recognition research. Various Algorithmic approaches for feature Recognition: graph based algorithm, volumetric decomposition techniques, and hint based geometric reasoning. Each approach is discussed in detail with some assessments of the technology.