Manufacturing Systems Foundations of World-Class Practice (1992) / Chapter Skim
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Improving Quality Through the Concept of Learning Curves
Improving Quality Through the Concept of Learning Curves
Pages 107-115
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From page 107... ...
It would be hard to find a U.S.-based manufacturing enterprise that does not place quality near the top of a list of strategic or operating objectives that would also include cost, innovation, and customer focus. This sensitivity to the customer demand for quality has not always been a dominant force in the operating strategies of U.S.
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From page 108... ...
The measures of quality that are implicit in the application of SPC necessarily concern shorter time periods; that is, they reflect the current status of the process or system that is producing the product. Although the importance of this near-term collection of data and appropriate analysis to
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From page 109... ...
THE LEARNING CURVE RELATED TO COSTS A traditional approach to measuring the long-term cost performance in a manufacturing operation is to use the "experience" or "learning" curve concept (Henderson and Levy, 19651. This asserts that the fractional reduction in the average cumulative cost (in constant units of measure)
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From page 110... ...
Although the specific actions taken to improve quality differ from those taken to reduce unit costs, a striking similarity exists between the two lists. In particular, both result from conscious actions taken by management and employees to accomplish a common strategic objective for the enterprise.
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From page 111... ...
In Equations 2, 3, and 4, the sign can be positive or negative positive if the quality index is improving as cumulative production volume increases, for example, yield from a process; negative if the quality index reflects defects or defective parts, which will decrease as the cumulative production volume increases. While the particular attribute of the product or process being considered will most likely be different for each product and process, the above formulations are independent of the specific attribute that can be related to the quality index.
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From page 112... ...
Data are presented in Figures 1 through 3 relating an index of quality to the cumulative volumes of production for three different products light bulbs, a small electric motor, and grey iron castings. General Electric Company and The Dalton Foundries, Inc., graciously supplied the data contained in these figures.
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From page 113... ...
Courtesy of General Electric Co. what to be preferred for batch, or average, sampling of the metric in question, we have chosen to present three of these sets of data in terms of the exponential relationship of the quality index to the cumulative volumes of the product produced.
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From page 114... ...
Although the present data do not appear capable of distinguishing among the various forms for a learning curve for quality, it appears that one or more forms can easily be found to permit a reasonable extension for setting new goals or examining the impact of past actions on performance. Because the time frame in which these products were in production is long, it is reasonably certain that the actions suggested earlier as being important for management and employees in achieving a continuous improvement in quality were taken throughout the life of these products.
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From page 115... ...
In our view, this is a shortcoming that should be addressed by all concerned with continuous improvement. The systematic collection of data on quality and the representation of these data in the form described by Equations 2, 3, or 4, offer a means of tracking progress on the "continuous improvement" of quality and a means by which realistic expectations can be established for future goals.
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