Some of the arrays offered in Minitab's catalog let a few selected interactions to be studied. Orthogonal array designs concentrate primarily on main effects. This can reduce the time and cost associated with the experiment when fractionated designs are used. Because of this, each factor can be assessed independently of all the other factors, so the effect of one factor does not affect the estimation of a different factor. An orthogonal array means the design is balanced so that factor levels are weighted equally. Taguchi designs use orthogonal arrays, which estimate the effects of factors on the response mean and variation. Using Taguchi designed experiments, the team found that by increasing the clay's lime content, a control factor, the tiles became more resistant, or robust, to the temperature variation in the kiln, letting them manufacture more uniform tiles. They could not eliminate the temperature variation because building a new kiln was too costly. A quality team discovered that the temperature in the kiln used to bake the tiles varied, causing nonuniform tile dimension. The company was manufacturing too many tiles outside specified dimensions. A product designed with this goal will deliver more consistent performance regardless of the environment in which it is used.Ī well-known example of Taguchi designs is from the Ina Tile Company of Japan in the 1950s. A process designed with this goal will produce more consistent output.
During experimentation, you manipulate noise factors to force variability to occur and then determine optimal control factor settings that make the process or product robust, or resistant to variation from the noise factors. Taguchi designs try to identify controllable factors (control factors) that minimize the effect of the noise factors. These uncontrollable factors are called noise factors. Taguchi designs recognize that not all factors that cause variability can be controlled. A Taguchi design is a designed experiment that lets you choose a product or process that functions more consistently in the operating environment.