Lean Manufacturing 306 

During the past fifty years, continuous flow manufacturers have led American industry in automating plant operations and adopt­ing new systems, with one exception—MRP II. On the surface, the marriage of continuous flow and MRP II would appear to be a natural fit. A shallow bill of material with relatively few raw materials represents a simple analytical model for computerized planning. However, continuous flow manufacturers have until recently steered clear of MRP II for a variety of reasons, including the inability to cost justify it, the lack of continuous flow functionality, and the perception that MRP II is an expensive IS toy with no application in the world of process controllers and DCS.

The objective of this paper is to make clear why continuous flow manufacturers are now embracing MRP II, and to examine the benefits they are achieving. First, continuous flow industries are identified and continuous flow characteristics are explained. Differences are drawn between continuous flow manufacturing, batch processing, and repetitive manufacturing. Then, computer system requirements are explored, both in general terms, and in terms of specific MRP II package requirements. Finally, benefits which are being obtained by these industries are discussed. MRP II is successfully being used to improve multiplant planning, to enable better sourcing decisions, to improve raw materials and finished goods inventory control, and to improve cost identifica­tion and control.

Despite the popular view of continuous flow manufacturing as "steady state" processing in which every variable is controlled to the ninth decimal place, there are many opportunities for improve­ment in the areas of capacity planning, inventory control, and costing. Process manufacturers recognize this and are implement­ing CIM and ERP programs on a broad scale, at divisional levels as well as corporate-wide. In all cases they realize that MRP II plays a key role as the foundation of an integrated environment.

Continuous flow manufacturing is found in a wide variety of industries, and always involves the manufacture of bulk product for immediate sale, for further processing, or for packaging. Any further generalizations are tough, because there are more differ­ences than similarities among flow processors, especially when compared across industry verticals like chemicals, foods, and textiles. However, the choice to use a continuous flow process is always the logical outcome of a decision that takes into account product attributes, process economics, and market forces.

Industries that perform continuous flow manufacturing can be categorized by type of process—e.g., refining (petroleum, sugar), milling (rice, corn, wheat), weaving (cotton, silk, polyester), and coating (steel, paper). Other processes common to continuous flow manufacturing include distillation, thermal cracking, reduc­tion, bleaching, grading, carding, spinning, and splitting. In terms of Standard Industry Classifications (SIC), continuous flow is found in major industry groups 20 (food), 22 (textiles), 24 (lumber), 26 (paper), 28 (chemicals), 29 (petroleum), 30 (rubber and plastics), 32 (glass), and 33 (primary metals).

Continuous flow manufacturers can be found throughout the world, but processing plants tend to be clustered in regional pockets. For example, because they often require large quantities of water either as a formula ingredient or for cooling purposes, plants are commonly located along rivers. Chemical and steel plants can be found strung along the Ohio and Mississippi rivers, which also serve to support barge traffic of raw materials. Plants are also located where natural resources are plentiful, like trees, cotton, grain, petroleum, and fish. Other determining factors in the location of plants includes the ability to minimize transporta­tion costs, and the availability of inexpensive labor.

To be Continued

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