Major companies use product performance, cost, quality and reliability as assets in the on-going battle for market leadership and sustainable competitive advantage. No company can commercially stand still and the way to be competitive is to continuously improve both product and process. Product development optimisation methods that give companies a head start have been the focal point of researchers for years. This paper proposes a study of functional analysis focused on the particularities of rapid manufactured custom-fitting products. The authors approach each stage of existence in a product’s life cycle with technical functional analysis in order to obtain a custom-fitting product that better satisfies the customer’s needs and yet permits a sustainable manufacturing process. The functional analysis (FA) study is targeted on the specific characteristics of rapid manufacturing (RM) for single part products and uses tools like FAST diagrams, product life cycle analysis, technical and economic matrices. The study focuses on the functionality of the product all throughout its life cycle, starting with development, production, usage, maintenance and finishing with storage or disposal. The merging of rapid manufacturing technologies with technical functional analysis facilitates major changes, which lead the way to product innovation and achievement of sustainable competitive advantage. Amongst the most important advantages brought together by FA and RM are customer focus, high quality final products, energy efficiency, low material waste, production speed and time-to-market, manufacturing complex geometries, low costs etc.