The purpose of this project entitled “Design of the manufacturing process of a reduction gear” is to design a manufacturing process in order to produce 20000 units of a reduction gear per year. It is enrolled for a forecast of 5 years. As the product involves public users, therefore it was mandatory to obtain good quality of part. Taking into account today’s highly competitive economic environment, it was also necessary to ensure the economic viability of the project, and thus profitability. For achieving that, different steps have been followed. The first one was the definition of a manufacturing strategy, which consists of deciding, for each part, which kind of operation is done, either internally or externally (outsourcing manufacturing), according to criteria such as surface finish of parts, mechanical properties, and the cost of rough parts. Afterwards, an advanced planning of each cycle phase was prepared. In this second step, the choice of the most convenient process and machine tool, tools, cutting conditions, maximum power of the spindle, machining times and minimal production costs were defined. The cycle and phase sheets were then provided for each machined part with related explaining drawings. In order to avoid waste times, a definition of the workshop organization machine tools and layout was done. Calculation of economical viability has ensured the feasibility and the profitability of the manufacturing process. As a conclusion, a comprehensive manufacturing process has been defined taking into account both quality and economic requirements.