The aim of this talk is to position Operational Research techniques and Decision Support tools from the perspective of optimal design of machining systems. The developed methodology is based upon advanced line balancing methods and their coupling with process planning and equipment selection algorithms. An example is given where these methods are implemented in a decision support system (DSS) to offer a cognitive aid for the early design stages of machining lines. The DSS assists the decision makers in finding the configuration of a new line that will meet quality and productivity requirements and minimize the investment costs over the long term.