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4.3 Taguchi methods
There are two types of factors in parameter design that affect a product‟s functional
characteristic: control factors and noise factors. Noise factors are primarily response
for causing a product‟s performance to deviate from its target value. Taguchi
developed a family of fractional factorial experiments matrices which eventually
reduce the number of experiments, but still provide sufficient information. The
conclusions can also be associated with statistical levels of confidence. In Taguchi‟s
methodology, the factors affecting the process quality can be divided into two types:
control and noise factors. Control factors are those set by the person conducting the
experiments and are easily adjustable. These factors are expected to have a
significant influence over the quality of the product. Noise factors, on the other hand,
are those undesired variables that are difficult, impossible, or expensive to control,
such as the ambient temperature, humidity, and the aging of parts.
The major steps in the application of Taguchi‟s method in an experimental
investigation are:
To identify the factors / interactions
To identify the number of levels of each factor
To determine the values of the level of the factors
To select a appropriate orthogonal array
To assign the factors / interactions to the columns of the orthogonal array
To conduct experiments
To analyse the data and determine optimum levels
To conduct the confirmation of experiments
The Taguchi approach has been successfully implemented in research and several
industrial organizations to change their perspective on quality management [34].
Taguchi philosophy is to design quality built into the product rather than to have it
inspected after its production. Quality improvement must start at the very beginning
i.e. during the design stage of the product development and should continue through
the production process. Dr Taguchi observed that any amount of inspection could
not put quality back into the product and it only treated the symptom, therefore he
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