Cell formation is one of the important problems in design of a cellular manufacturing system. In recent years,many works had been carried out in this active research field. Specially, similarity coe fficient methods had been studied widely to form part-machine cells so as to minimize intercellular part movements, but few of them had considered inŽuence of operation sequences and times on cell formation simultaneously. In this paper, we improve an existing similarity coefficients based on considering the factors of operation sequences and operation times. A feasible and effective operation sequences and times-based similarity coefficient method is presented to solve cell formation problems. The improved method is applied to several examples from literatures and a numerical example with some repeated production processes. The results demonstrate that it is necessary to consider the operation sequences and times into similarity measure between each pair of parts or machines, and the proposed method is valid and available for cell formation in cellular manufacturing system with some repeated operations.
