Accurate gear profile plays an important role in determining the transmission performance of gear-drive equipment. In this paper, a novel method for extracting gear tooth profile edge is presented. The presented method is based on engagement-pixel image edge tracking (EPIET) technique, and does not rely on the traditional meshing theory. An algorithm for the proposed method is put forward. Firstly, instantaneous contact images between the envelope curves of the gear profile and the instantaneous locus of the cutting tool are acquired. Secondly, pixels on the boundary of the envelope curves are lighted and the instantaneous locus coordinates of the cutting tool are calibrated. Lastly, the pixel coordinates of instantaneous meshing points are extracted, based on the fact that there is exactly one contact point per instant, and major error sources of the presented method are discussed. To verify the effectiveness of the presented method, a case study is conducted on a face gear, which is a type of complex conjugate gear, to extract its tooth profile edge. In the study, the tooth profile error and the contact line error are investigated. The results demonstrate that the presented method, without knowing complicated meshing equations, can acquire feasible accuracy and stability, compared with traditional meshing equations. It is shown that the novel method can be extended to applications of digital design of complex conjugate curved surfaces, in a simple and fast manner.
