The task of the design engineer is to configure a design such that a predetermined functional requirement is fulfilled, and that it is achieved within a given set Of performance criteria. As a design evolves, so these performance criteria change, driven by the ever-increasing needs of the customer and the inherent competition between manufacturers. It is during this evolutionary process that the engineer demands a CAD system which can represent knowledge about the design and explore solutions regarding the relationship between geometry and behaviour. This is necessary in order to realize the full potential of an existing design, or to examine modifications to an existing design that may achieve the desired performance characteristics. The work described in this paper uses a constraint-based modelling environment to represent and analyse a high-speed packaging operation. The goal of the modelling work is to produce an optimal design solution for the given performance requirements, as well as to satisfy the constraints imposed by the existing machine system and packaging process. The construction of the model is described and the identification and representation of the design constraints are discussed. These constraints are then applied to a possible machine modification or redesign and an optimized configuration is developed in the modelling environment.