This article uses the concepts of lean and manufacturing cells with the objective of increasing the productivity of a conversion process of a UHT dairy product. The research methodology is a case study on a part of the milk making process in a large dairy food company in Peru. The research is of the qualitative type and employs the methodof action research, which consists of successive cycles of experimentation and evaluation. This method is used for the design of a manufacturing cell for the conversion of the UHT product into a food plant. The results of the research indicate that the manufacturing cells allow to optimize the conversion process, increase productivity, reduce inventory and balance the process in the supply chain. Additionally, the designedcell allowed to work simultaneously in the areas of occupational safety and hygiene and ergonomics.