Reverse engineering has been widely recognized as a central step in a product cycle of designing and manufacturing. However, major problems with current reverse engineering technology are the inefficient surface reconstruction process, lack of digitizing accuracy control in the data digitization process, and bottlenecks resulted from huge amounts of digitized surface points in the surface modeling process. Moreover, under this limitation, modern concurrent engineering concepts are difficult to be applied to obtain optimal product process. This paper presents a case study on the reverse designing of a plastic part. The study applies a developed reverse engineering approach to reconstruct surface--a series of advanced algorithms, including segmentation, simplification, extraction, fitting curves and reconstruction surface. Two orthogonal curves, which are fitted from the digitized points, are taken as base curves of a ruled surface patch. All surface patches are merged into a whole surface by trimming and chamfering. A CAD model is constructed based on the whole surface. The approach integrates surface digitizing and modeling processes of a plastic part into surface reconstruction process. Using the approach, accurate product CAD model can be efficiently generated and the product design cycle of plastic parts can be successfully linked.