One important use of reverse engineering/reverse modeling and data capture is in part validation and inspection. Traditionally, inspections are performed with gauges or coordinate measuring machines (CMMs). The limitation of these methods is the relatively small number of data points that may be inspected. Also, these types of inspections measure discrete points or line traces. Reverse modeling is a powerful method of part inspection. In this method, a finished part is scanned with high-accuracy three-dimensional digital capture tools, and then the scanned model is overlaid on the CAD file, which is theoretically accurate. The use of fiducial markers helps to align and register the scanned data set to the CAD data set. Inspection analysis software such as PolyWorks (www.innovmet-ric.com) is used to analyze the deviations between the CAD model and the manufactured part. The power of this method is the ability to apply geometric tolerancing analysis tools in software, as well as the ability to color map dimensional variances. This gives the ability to visualize not only discrete inspection points, but, for example, the flatness of a surface, with its high and low areas revealed.
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