An inspecting method of 3D dimensioning completeness based on the recognition of RBs

The intelligent and automatic inspection of 3D dimensioning completeness plays an important role in 3D CAD/CAM systems. This paper proposes a new inspection method based on the recognition of the rigid body (RB) using the trajectory intersection method. The concept of the positioning element (PE) is introduced, and the selection rules of the PE group are established based on their intersection with the degree of invariance (DOI). Then, by setting the PEs as the datum, the RB recognition method, based on the trajectory intersection method, is proposed. Through adding a virtual dimension to the inner part of a RB, a combination of RBs is achieved by fixing the equivalent PE group. Thereafter, four conditions of dimensioning completeness are analyzed according to the combined RB and dimensional states. Through the differential locus method, the minimum missing dimension extraction process of the basic geometric elements is established. The algorithm for extracting dimensions missing from two related RBs is also carried out. Finally, the validity and stability of the method are verified using two dimensional models, and a prototype system of 3D dimensioning completeness inspection is introduced. (C) 2017 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.