Recognition of multi axis milling features: Part I-topological and geometric characteristics

Most of the work in machining feature recognition has been limited to 2-1/2 and 3 axis milling features. The major impediment to recognition of complex features has been the difficulty in generalizing the characteristics of their shape. This two-part paper describes general purpose methods for recognizing both simple and complex features; the latter may have freeform surfaces and may require 4 or 5 axis machining. Part I of this paper attempts to describe features in terms of geometric and topological characteristics. Part II of the paper uses the characterization and classification developed in Part I for designing feature recognition algorithms. Part I proposes five basic categories and several subclassifications of features derived both from machining considerations and computational methods for NC toolpath generation. Rather than using topologically rigid features, such as slots and steps, etc., machining features are classified as "Cut-Thru," "Cut-Around" and "Cut-on" and further classified into sub-categories. Each feature class is described by a list of properties. Apart from the obvious use in feature recognition, this feature classification and characterization may have potential use in developing future data exchange standards for complex features.