MATERIAL-HANDLING SYSTEMS

1. OVERVIEW

At a basic level, material handling is primarily concerned with the storage and movement of material (in various forms) in / through production and service systems such as factories, warehouses, distri- bution centers, cross-docks, container terminals, airports, hospitals, and similar mission-oriented fa- cilities. Although the physical movement of material is perhaps the most visible aspect of material handling, as suggested by the following ‘‘right definition,’’ material handling goes beyond that. Ma- terial handling is ‘‘providing the right amount of the right material, in the right condition, at the right place, at the right time, in the right position, in the right sequence, and for the right cost, by using the right method(s)’’ (Tompkins et al. 1996). Note that using the ‘‘right method(s)’’ includes safety and ergonomic considerations, especially when humans are involved directly or indirectly in the handling system.

It is interesting to note that some publications have used a similar definition (i.e., providing the right amount of the right material at the right time and place) in referring to the just-in-time philos- ophy of the Toyota Production System, which is now generally known as lean manufacturing. This

overlap suggests that providing the right amount of the right material at the right time and place must occur at two levels. One is at a planning level, where decisions such as lot sizes, shipment frequencies, reorder quantities, production or delivery schedules, and so on are made, while the other is at an execution level, where actual product (or parcel) movement and tracking / control takes place. The former would generally fall under production and inventory control for manufacturing facilities (or scheduling and planning for service facilities), while the latter would fall under material handling for either type of facility.

Another interesting aspect of material handling is the fact that, in the context of lean manufac- turing, material handling is viewed uniformly as waste. A driving force in lean manufacturing is the elimination of waste. If this is interpreted strictly as the elimination of all material handling, it becomes immediately obvious that no goods would be shipped from factories (in fact, all the incoming raw material and purchased components would accumulate at the receiving dock of a factory), all incoming and outgoing ships would wait indefinitely at container terminals, no trucks would be loaded or unloaded at cross-docks, and so on. Clearly, the intent is to eliminate waste by eliminating all movement and inventories that are not essential for completing the mission of a production or service system. Therefore, planning, engineering, and the successful day-to-day operation of the material- handling system is absolutely necessary to achieve efficiency while meeting the goals of a mission- oriented facility. Significant cost-savings and performance improvements can be realized by eliminating and / or simplifying material handling functions, implementing methods changes, selecting proper handling equipment, and eliminating unnecessary handling operations and inventories.

With the increasing availability and use of automatic identification technologies (such as bar coding), many people have come to recognize that material and information flow together, or that material flow generates information and vice versa. Clearly, the two flows occur in different forms over different channels. Material flow involves movement of physical objects, while information flow involves movement of bytes or packets; material flow is handled via people, conveyors, lift trucks, hand trucks, and so on while information flow is handled through copper or fiber networks. However, as one type of flow occurs, it changes the state of the other or it triggers certain ‘‘events’’ for the other, and the two flows are in many ways intertwined.

Before automatic identification technologies became widely available, information flow was slow relative to material flow. Material would be moved (typically in large batches and / or over a period of time) before the information system was updated. This resulted in delays and in information that was too old, highly clustered, and often inaccurate to be useful, except for accounting or off-line, limited tracking purposes. Today, with the aid of automatic identification technologies (such as bar coding and voice recognition), used in conjunction with computer networks and communications technologies (such as radio frequency), information systems are often updated on a real-time (or near- real-time) basis and hence have become more accurate and more prominent / useful to a wider range of users, from decision makers to operations managers and end customers. This has also resulted in a higher degree of parallelism between information flow and material flow.

Due to rapid advances in computing technology, the information system has, at the same time, moved from a batch-oriented, centralized mainframe environment to a real-time-oriented, decentral- ized microprocessor environment, which makes it possible to store / retrieve larger amounts of infor- mation at multiple locations while developing more advanced logic to guide, optimize, or interpret material flow. (Despite an occasional misplaced parcel or lost luggage, most readers can readily identify with excellent examples of real-time information and material-flow systems used by overnight delivery providers and major airports.) While information technology and the hardware / software considerations for material-handling systems are well beyond the scope of this chapter, reference will be made to information flow / handling and its implications when appropriate.