Production Planning Problems in Cellular Manufacture

This paper analyses what kind of coordination between cells is necessary when using cellular manufacture compared to a production situation that is functionally organized. Three levels of coordination are distinguished: internal, horizontal and vertical. Two types of relations between units are considered: sequential and lateral. It is shown that there is a change in coordination requirement if cellular manufacture is used in stead of functional manufacture. This is illustrated with some cases in which the production planning problems of firms that use cells in the production of parts are analyzed. INTRODUCTION In metalware fabrication many firms have changed to cellular manufacture without fundamentally changing their production planning and control systems. Often they face problems with the support given by these (MRP) systems. This paper analyses the kind of coordination between and within cells that is necessary in cellular manufacture compared to functional organized manufacture and presents the results of 5 short case studies performed in small batch mechanical parts producing firms that use cellular manufacture. In the literature on the comparision of cellular and functional layout a distinction is made between cellular systems that use mainly the flow line type of cell and systems that use hybrid cells with a functional layout. The firms we have studied use the latter type. COORDINATION WITH SEQUENTIAL AND LATERAL RELATIONS The concept of a relative autonomous production unit is used in determining the coordination requirements in cellular and functional manufacture. In both situations a kind of autonomous unit is used: in cellular manufacture it is a cell in which the same kind of products are made (using different operations) and in functional production it is a production department in which the same kind of operations are performed (on different products). To compare the coordination requirement in functional and cellular manufacture three levels of coordination are distinguished (see figure 1): internal coordination (within the unit), horizontal coordination between units and vertical coordination with other organizational areas (for example R&D, purchasing, engineering, maintenance). Differences in vertical coordination requirements are generally caused by differences in the degree staff functions are decentralized to the units /1/. In general there is a stronger tendency to take decentralizing support functions in consideration in cellular manufacture, especially if the cells are designed according to sociotechnical principles. In /2/ it is stated that the focus on improving the skills of workers by decentralizing support functions is an important difference between production islands in Germany and cells in the USA. So a change to cellular manufacture can result in a change in vertical coordination requirements. In the rest of this paper the focus is on internal and horizontal coordination.