Error sources in a 3-D reverse engineering process

The repeatability and accuracy of the digitizing process in a reverse engineering or 3-D inspection process becomes critical when destructive methods are used for data capture, as the part is no longer available for verification by other methods. This paper deals with the error sources in a destructive 3-D reverse engineering process. In this process, the part is encapsulated in epoxy and the encapsulated part is milled one layer at a time using a fly cutter with a small layer thickness. The freshly cut surface is scanned and images of different layers are merged to give 3-D point data for the part. Various sources of errors contributing to overall error in accuracy and repeatability of the process have been identified and their effects are discussed. The study showed that the threshold setting for image processing and mill-head vibrations have significant effect on accuracy and repeatability, respectively.