Advanced CAQ: Comparing Manufactured Products With Underlying CAD Models

The quality of manufactured products usually needs to be verified. This paper presents an advanced CAQ approach to compare manufactured objects with reference data from underlying CAD models. First, we give an overview about the current state of the art of optical 3D measurement techniques. Then we discuss the methods developed to implement our prototypic system in which we used a stripe projection system with combined grey-code and phase shifting processing. With this equipment, 3D data of object surfaces can be measured. In order to compare the 3D data (represented in some sensor co-ordinate system) we need a registration to the CAD co-ordinate system. First the selection of a starting point for the orientation parameters is described. For the registration process we use different numerical algorithms to minimise a distance function. To achieve a better performance, we introduce an optimisation process based on 3D voxel arrays. After the registration process several parameters for the kind of geometric displacement can be calculated and visualised. For objects that cannot be measured from one direction we also implemented a pair wise registration as well as a global registration. Furthermore, we present some rapid prototyping examples our CAQ approach has been applied to and outline some application fields.