Computer tomography for nondestructive testing in the automotive industry

The application of computer tomography (CT) for non-destructive testing is of continuing interest to research and industry alike, as economic pressure is ever increasing on production processes. Three concurring goals drive the development of CT, namely: It has to be fast, cheap and precise. With a fast CT-system, the technique can not only be used for error analysis and precision measurements, but also for the application as a standard tool in the production line for the complete quality control of parts. At the Robert Bosch corporate research centre in Stuttgart, Germany, we have set up a CT-system, that allows us to conduct experiments towards these goals and to test and develop the latest software for the reconstruction of x-ray images. One of our main challenges is to use CT for reverse engineering processes and to create computer assisted design (CAD) models from measured data. For this application often a coordinate measurement machine (CMM) is used that gathers a cloud of data points by optical inspection. However, for many parts the inside of the object is relevant. Here CT has the unique advantage of delivering volumetric data. Once the process of the generation of a cloud of data points can be achieved with high precision, standard reverse engineering CAD software can be used to determine the dimensions of the interior structure of an object. This paper describes the use of CT for non-destructive testing at Robert Bosch GmbH, the accuracy limits for the measurement of volumetric data and the classification and analysis of material defects. Furthermore, it highlights the ongoing research to make CT fast, exact and cheap, and to enable its utilisation for 100% testing of parts at the end of a production line.