3d Geometry Measurement of Hot Specimens in Rough Vacuum

Inline process control by 3d geometry measurement is an important part of the cost-effective production of high precision components. Within the Collaborative Research Centre (CRC) 1153, funded by the German Research Association (DFG), a production chain for high performance hybrid components is developed. These so called Tailored Forming components are composed out of two or more materials such as aluminium and steel, bonded at a discrete joining zone. The inline inspection of the components, especially directly after hot forming processes, can be used to reduce costs of production by rejecting defect components early. We use a fringe projection system to acquire the geometrical data within the available timeslot. The temperature gradient around the hot specimen causes an inhomogeneous refractive index field in the surrounding air, which prevents rays of light from proceeding in a straight line. By placing the specimens in rough vacuum, we reduce the undesired light deflection effect and are able to measure the 3d geometry of hot specimens with increased accuracy.