Generalised models of design iteration using signal flow graphs

Changing customer preferences, demand for quality, and new technologies have led to very short product life cycles. This requires firms to have short product development lead times while keeping product costs low and quality high in order to stay competitive. In this context, we focus on improved understanding of time-consuming design iterations. We are creating tools for modeling product development projects in order to predict the performance of product development organisations. In this paper, signal flow graphs are presented as a flexible tool for design process modeling, and illustrated using an industrial example. Analysis of the model allows computation of the probability distribution of lead time and identification of the key drivers of lead time.