Page 30 - Six Sigma for electronics design and manufacturing

Chapter
1
The Nature of Six Sigma
and Its Connectivity
to Other Quality Tools

1.1 Historical Perspective
The modern attention to the use of statistical tools for the manufac-
ture of products and processes originated prior to and during World
War II, when the United States of America geared up to a massive
buildup of machinery and arms to successfully conclude the war. The
need to manage the myriad of complex weapon systems and their var-
ied and distributed defense contractors led to the evolution of the sys-
tem of Statistical Quality Control (SQC), a set of tools that culminat-
ed in the military standards for subcontracting, such as MIL-Std 105.
The term “government inspector” became synonymous with those in-
dividuals who were trained to use the tables that controlled the
amount of sampling inspection between the different suppliers of
parts used by the main weapons manufacturers. The basis of the SQC
process was the use of 3 sigma limits, which yields a rate of 2700 de-
fective parts per million (PPM).
Prior to that period, large U.S. companies established a quality
strategy of vertical integration. In order to maintain and manage
quality, companies had to control all of the resources used in the prod-
uct. Thus, the Ford Motor Company in the early part of the 20th cen-
tury purchased coal and iron mines for making steel for car bodies
and forests in Brazil to ensure a quality supply of tires. This strategy
was shelved during the rapid buildup for the war because of the use of
coproducers as well as subcontractors.

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