Cells are formed by grouping equipment in a process sequence by following the three principles of Just In Time processing; flow according to takt time, inventory pull through signals generated by demand, and use of minimum resources to make or repair only what is needed – when it is needed.
Equipment is positioned within a cell so that production goes from one adjacent machine to the next, for most products processed within that cell. Right-sized equipment is preferred, not only to enable single-piece flow but also to physically fit within the cell so as to minimize operator motion.
A U shape is preferred because it minimizes walking distance and allows different combinations of operations for a family of products. The cell should be designed as small as physically possible yet with enough room for the necessary number of operators to meet maximum demand. There should be no room in the cell for inventory other than Standard WIP.
Progress tracking is made simple by cells; one can stand at the opening to a cell and see the amount of product already completed and that awaiting processing. The goal is to not have product leave the cell for any reason, to further that managerial ease.
Many companies use the terms cell and line interchangeably, but for highly engineered products requiring many operations we prefer to think of a line as consisting of a collection of several cells linked together with kanban or supermarkets to support a more complex production line.
Office layouts benefit from cellular design for identical reasons.