Page 510 - Design for Six Sigma a Roadmap for Product Development

Chapter
13

Taguchi’s Orthogonal Array
Experiment

13.1 Taguchi’s Orthogonal Arrays
The Taguchi method is a comprehensive quality strategy that builds
robustness into a product/process during its design stage. The Taguchi
method is a combination of sound engineering design principles and
Taguchi’s version of design of experiment, called an orthogonal array
experiment, discussed in this chapter. Other aspects of the Taguchi
method are discussed in subsequent chapters.
In Taguchi’s experimental design system, all experimental layouts
are derived from about 18 standard orthogonal arrays. An orthogonal
array is a fractional factorial experimental matrix that is orthogonal
and balanced. Let’s look at the simplest orthogonal array, the L 4 array
in Table 13.1.
The values inside the array (i.e., 1 and 2) represent two different
levels of a factor. By simply using 1 to substitute for 1, and 1 to sub-
stitute for 2, we can find that this L 4 array becomes

Column
Experiment no. 1 2 3
1 1 1 1
2 1 1 1
3 1 1 1
4 1 1 1

Clearly, this is a 2 3 1 fractional factorial design, with defining relation
I ABC. Where column 2 of L 4 is equivalent to the A column of the

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