Mumbai University > mechanical engineering > sem7 > CAD/CAM/CAE

Marks: 8 M

Year : May 2015

• The term "feature" implies different meaning in different engineering disciplines. This has resulted in many ambiguous definitions for feature. A feature in computer-aided design (CAD), usually refers to a region of a part with some interesting geometrical or topological properties. These are more precisely called form features.

• Feature data in CAD can be specified either as a collection of surfaces or volumes. Surface features can be used to describe manufacturing tolerances or locating surfaces in assembly design.

• Volume features on the other hand, can be used in tool path generation,etc. Manufacturing information is better portrayed using volumetric features.

• Work on features can be divided into two rough categories:Design by feature and feature recognition.

• In design-by-features, also known as feature-based design (FBD), feature structures are introduced directly into a model using particular operations or by sewing in shapes.

• On the other hand, the goal of feature recognition (FR) is to algorithmically extract higher level entities (e.g. manufacturing features) from lower level elements (e.g. surfaces, edges, etc.) of a CAD model.

Design by Features

• By using features to build up shape models, the design process is made more efficient, because the shape of features can be pre-defined. Features in FBD can be directly associated to manufacturing information.so that these information can be retrieved in downstream applications. In this way, an overall CAD/CAM system can be fully automated, however, the idea of using manufacturing features to design a part has its own shortcomings.

• The features used to design the part do not necessarily represent the best way to manufacture it. It is, therefore, the designer's responsibility to evaluate all methods that can produce the part. Furthermore, manufacturing features are not the most natural way of designing a part.