看到一本质量管理学书籍的一章，里面有个例子：美国福特与日本马自达基于同样的图纸、加工设备和工序，分别在美国和日本生产变速器组件（ transmission components）。由Ford 组装的变速器，出现故障的机率较Mazda 的高，对 Ford生产的部件进行严格检查，发现所有的产品都在“可容忍的标准范围”内（within acceptable tolerances，即一般统计学上的95%或99%置信度，这是质量的最低要求）。然而，对Mazda生产的部件检查发现，几乎毫无例外的都精确地达到了的指标，没有一个是落在“可容忍的范围”。这就解释了在机械组装上，因为误差大的部件引起的磨损，最后导致早出现汽车故障。
http://www.flexstudy.com/catalog/schpdf.cfm?coursenum=9529a
Two well-publicized examples in practice have given credence to this theory. In one case, Ford and Mazda were producing identical transmission components in the United States and Japan using the same blueprints, equipment, and processes. The Ford assemblies were experiencing a higher rate of field failures. Upon examining the critical dimensions produced by the Ford plant, all were found to be within acceptable tolerances. However, upon examining the Mazda-built components, nearly all were precisely on target with almost no variation within the allowable tolerance. The explanation is that in mechanical assemblies, excessive variation from design targets causes premature wear, eventually resulting in early field failure.
http://www.flexstudy.com/catalog/schpdf.cfm?coursenum=9529a
Two well-publicized examples in practice have given credence to this theory. In one case, Ford and Mazda were producing identical transmission components in the United States and Japan using the same blueprints, equipment, and processes. The Ford assemblies were experiencing a higher rate of field failures. Upon examining the critical dimensions produced by the Ford plant, all were found to be within acceptable tolerances. However, upon examining the Mazda-built components, nearly all were precisely on target with almost no variation within the allowable tolerance. The explanation is that in mechanical assemblies, excessive variation from design targets causes premature wear, eventually resulting in early field failure.
最后编辑: 2012-10-19
