Manufacturing Systems Foundations of World-Class Practice (1992) / Chapter Skim
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Are There 'Laws' of Manufacturing?
Are There 'Laws' of Manufacturing?
Pages 180-188
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From page 180... ...
L = ~ relates the average number of items present in a queuing system to the average waiting time per item. Specifically, suppose we have a queuing system in steady state and let L = the average number of items present in the system, = the average arrival rate, items per unit time, and W = the average time spent by an item in the system, then, under remarkably general conditions, L = kW.
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From page 181... ...
The basic tautological nature of the proof can be illustrated by drawing a plot of the number of items in the system versus time, as in Figure 1. The area, A, under the curve represents the total waiting done by the items passing through the system in the time period T
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From page 182... ...
The regularity of the curves can be distorted by a variety of special circumstances, such as electronic mail, location of people on different floors, and the presence of a coffee machine, but the basic phenomenon is strong and its understanding is vital for designing buildings and organizing work teams effectively. Another example is the experience curve, which is illustrated in Figure 3.
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From page 183... ...
183 FIGURE 2 Communications between R&D groups as a function of their physical distance from each other. Cumulative Production FIGURE 3 Experience curve illustrates the decreasing unit costs for manufacture with accumulated production.
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From page 184... ...
For example, if a person has, as a reference point, the catalog price of a particular product and then finds the item in a store at a lower price, he or she is likely to treat the difference as a potential gain. Subsequently, if the person buys the product, the purchase is likely to be considered especially satisfactory, and, in fact, the price "gain" may have helped stimulate the transaction.
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From page 185... ...
Familiarity with linear programming and duality provides a powerful framework for thinking qualitatively about many scheduling and resource allocation problems and for building specific manufacturing models. Another candidate could be the economic lot size model.
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From page 186... ...
It is likely that such a model will make too many assumptions to be accepted for the decision at hand, so a more complex and detailed model may be desirable. However, if the results of running a complex model suggest a particular course of action, it is imperative to know why the model produced those results, that is, what were the key assumptions and parameter values that made things come out as they did.
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From page 187... ...
Modeling Myopia People trained in operations research and management science or in engineering tend to think top-down, that is, in terms of objective functions, control or design variables, models, synthesis of systems from subsystems and the like, with the goal of using the entities under their control to maximize system performance. Consider, however, the following observation by Konosuke Matsushita of Matsushita Electric Industrial company (Stevens, 1989)
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From page 188... ...
As information technology has decreased the cost of communication, there has been a growth of lateral communication and coordination and a shift from vertically hierarchical organizations to more lateral and marketlike structures. Lateral coordination is valuable in speeding new product development, finding process improvements, implementing new ideas, and generally facilitating parallel operations in different physical locations.
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