This paper deals with the role, advantages, problems and solution techniques for the implementation of dynamic Computer Aided Process Planning (CAPP) systems in a Felxible Manufacturing system (FMS). A large variety of part features for both rotational and prismatic parts are considered. A custom group technology coding technique is designed and implemented to describe part profile to system software concisely and comprehensively. The part profile code is assimilated by the system interactively. A prototype CAPP system was designed for a pseudo FMS containing multiple machining centres. The system described develops process plans that consider both alternative routes and methods to manufacture a part. Heuristic knowledge was implemented to choose between alternatives with flowtime minimization as the objective function. The system was tested and its outputs validated with respect to both prismatic and rotational parts.