Feature-based machining of curved surfaces using the steepest directed tree approach

Abstract

Abstract A novel and efficient approach for defining and machining curved-surface parts is presented. The intelligent cutter path planning method, called the steepest directed tree method, replicates the actions of an expert engraver by using cutter paths that are established from the surface form. The curved surface is defined by triangular facets, the density and structure of which are determined by the intricacy and shape of the surface. Appropriate decimation and subdivision algorithms are used with swap optimization of facet edges to develop a uniform chordal error surface model. Geometrical form definition and recognition of topological features of the surface triangulation mesh are used to generate cutter paths along successive and interconnected steepest pathways, or steepest directed trees. Thus, geometrical surface features and machining characteristics of the end-milling process are used to develop optimum cutter paths. Planetary cutter locations are adjusted to be moved along smoothly changing paths, and height values are adjusted to avoid surface interference. Two machined examples of intersecting and intricate surface parts are presented that illustrate the benefits of the new approach. It is shown that due to more consistent geometry matching between cutter and surface (in comparison with the current CC-Cartesian method), surface finish can be typically improved by a factor of 16.8:1 while reducing cutting time by a factor of 1.6:1