Process planning was traditionally considered as manufacturing preparation that provides manufacturing methods and operation instructions. When computer aided process planning (CAPP) was first attempted in the early 1960s [Neibel, 1965; Schenk, 1966], it emerged as a vital link between computer aided design (CAD) and computer aided manufacturing (CAM). Today process planning has become an important part in computer integrated manufacturing (CIM) environment [Zhang and Alting, 1993; Larsen, 1993;