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Proceedings of CAD'15, 2015, 412-418
CAD-based Calibration for On-machine Measurement using Vision

Lorène Dubreuil, Yann Quinsat, Claire Lartigue, LURPA, ENS Cachan, Univ Paris-Sud

Abstract. The development and monitoring of machining processes is an important challenge in the control of production cost and for the quality of machined parts. Integrating inspection procedures within the production process contributes to the automation of a production system. Significant benefits include high speed of inspection, measurement flexibility, on-machine inspection, capability, and the possibility of 100% inspection. As far as on-machine inspection is concerned, it allows rapid decision making regarding the conformity of the produced part. This is in particular due to the great interoperability between machining and inspection. However, measurement operations and machining operations must be performed in the same reference frame to facilitate the comparison of the machined part to the CAD model for the conformity analysis. On-machine inspection is often performed using a vision based-system. Vision-based systems are used for the verification of machine set-ups, the survey of tool trajectories, part inspection of socket production, and so on. These systems present various advantages: low cost, rapidity, flexibility and simplicity of implementation in the context of production. A minor drawback is the system calibration. Calibration is necessary to transform a 2D point (or a point belonging to the picture) into a 3D point expressed in the reference frame. Within the context of on-machine inspection, the positioning of the camera frame relatively to the reference frame must be performed for each measurement operation. More generally, the reference frame of calibration can be anything.

Keywords. CAD-based calibration, Geometric feature, Machining setup

DOI: 10.14733/cadconfP.2015.412-418