Abstract: A method to realize automatic programming of shaft part is proposed based on
type-encoding and feature-encoding of entities. The paper first presents a method of
entity-breaking based on pitch point set, and introduces the method of minimum anti-clockwise
angle for searching the outline. Secondly, the type and feature of the entities is encoded which
constitute the outline. And then, the main feature is extracted and the assistant feature is
reconstructed. At last, according to the reconstructed outline, NC code is generated automatically
which can be recognized by CNC lathe. With a typical shaft part as an example, a program is
developed under the AutoCAD 2002 with ObjectARX, and verifies the methods and principles
proposed, which gives an effective result.

Key words: entity-breaking, outline-searching, feature-encoding, feature recognition;
automatic programming