This thesis covers the theme of inter-operational buffer following the concept of kaizen and WCM. The project took place in the FCA’s Mirafiori Powertrain Plant, concentrating on the internal logistics process, especially the connection between the two main areas, production and assembly. The project itself is continuously improving and ever evolving, adapting the nested PDCA cycle. Hence, a constant monitoring and adjustment is required. Within the first two chapters the background of FCA and specifically the Mirafiori Powertrain Plant will be unveil. The second chapter discusses in detail the products of Mirafiori Powertrain Plant. The third chapter will be started by introduction to the theories and instruments used in this project to reach the goal/target.