Reverse engineering is a powerful tool for duplicating real objects from data acquired by tracking systems, industrial X-ray computed tomography (CT), laser scanners, and image captures. This work proposed a novel method using the three-dimensional (3D) reconstruction and 3D printing to duplicate a mechanical key based on only one single naturally-captured photograph. A reverse engineering system of the mechanical key was self-developed which includes functions of projective transformation, curve extraction, point clouds generation, and 3D geometry reconstruction. The database technology was introduced into the image-based 3D reconstruction process for the first time to store basic dimensional information of key blanks, which provided supplementary information during the 3D key reconstruction process. Five different types of duplicated keys verified the effectiveness of the proposed method. The maximum geometric deviation was less than 0.39 mm. The duplicating time cost was 5 minutes for 3D geometry reconstruction and 18.3 minutes for 3D printing.
