Optical inspection of formed sheet metal parts applying fringe projection systems and virtual fixation

Modern forming technology allows the production of highly sophisticated free form sheet metal components, which are subject to a reversible geometrical deformation caused by residual stress, gravity or variations of the material. This distortion is usually removed during assembly and therefore the part’s tolerated parameters have to be inspected in fixed state, which simulates assembly conditions. Today this time-consuming work is done on CMMs (Coordinate measuring machines). Using fast optical measuring systems and virtual fixation, this process chain can be dramatically shortened and in-line measurement seems to be possible in future. Virtual fixation means that at first a workpiece is measured in distorted state without fixation and afterwards the shape in assembled state is simulated by FEM analysis. Thus, workpieces can be inspected with significantly reduced effort.