This paper presents a Real Tune Computer Aided Process Planning (RTCAPP) system which can serve as a support tool for economic decision making during design activities. The system is capable of providing the information about manufacturing implication of each added design feature to the designer during the design process of prismatic parts. A knowledge-based system using a bierarchical planning scheme and a multi-bank rule base is developed to generate near-optimal process plans in real time. The planning process is supported by an optimization module which uses dynamic programming to minimize manufacturing costs. The incremental planning mechanism utilizes as much of the existing plan information as is necessary to generate a new process plan, whenever the design is updated. The system serves as an effective concurrent engineering tool that can be used to provide real time feedback on the manufacturing cost consequences to the designer