Feature Recognition

Most of the generative type process planning systems have been designed on the premise that each part can be described using a set of predefined features. Part features can be of several types :

• Design features
• Manufacturing features
• Dimensions and tolerances
• Geometric features

Geometric feature is a collection of geometric entities such as surfaces, curves and points having significance in process planning.

There is a loose correspondence between geometric features and manufacturing features. Some sample geometric features used in development of expert process planning of prismatic parts is illustrated in given Table. Computers very often employ expert system for recognition of geometric features.

Table: Sample Geometric Features of Parts and Machinable Volumes

Rule 1 : (Step Recognition)

IF face f₁ is adjacent of face f₂

AND the angle between faces f₁ and f₂ is 90^o.

THEN the faces f₁ & f₂ form a step.

The search process for finding all part features by using production rules is computationally complex. To overcome this complexity it is recommended that we should employ attributed adjacency graph (AAG) for feature recognition.