In this paper the developmental process of a flexible robot-based assembly cell by a research institute in cooperation with the cells end-user is described. The developed cell contains novel processes-such as the assembly of parts with only minimal geometrical clearance-and is capable of producing a large number of product variations. Additionally a lean feeding method to process loosely supplied components was implemented as part of the setup. At the end the validation of the prototype cell within the real production environment is discussed. To fulfill cycle time constraints some changes to the cell concept were necessary for the final production cell, which therefore lacks some of the flexibility of the initial prototype.