In-line quality control utilizing close-range photogrammetry and a CAD-model

Abstract

This paper presents an overview of a measurement system that is designed for in-line shape inspection of metal sheet components in real-time utilizing pre-calibrated close-range photogrammetry and a CAD-model. The system is currently designed to measure parts thrown out on a conveyor belt that moves at about 1 m s−1 at a frequency of 0.5 Hz or less without fixturing. Detected features on the components in the camera images are used to align the CAD-model, describing the nominal shape, to the images from which required deviations are computed using photogrammetry. The measurement volume of the current system is 500 × 800 × 200 mm3 and absolute measurements are performed with an accuracy in the order of 0.1 mm. The in-line functionalities of the system have been verified at several real production sites in Sweden. In this paper, the basic components of the system are described together with a few results from real tests.

Optical metrology for digital manufacturing: a review

“…Conversely, optical non-contact technologies are more easily applicable in integrated scenarios. Still, hardware limitations often make true real-time measurement difficult to achieve, despite recent attempts made to overcome such barrier [79][80][81][82][83][84][85].…”

“…6, where the use of an additional source of homogenous light can potentially decrease the generation of occlusions and shadowing in correspondence to hidden and difficult to access geometric features [77]. Another example is given by Sjödahl et al [85] who developed an industrial demonstrator designed for in-line inspection of metal sheet components based on close-range photogrammetry. For this case, in addition to the redesign of the required illumination system, the measurement device used information derived from the computer-aided design model of the part to detect features in the images and perform reconstruction.…”