In Taguchi method the least variation and the optimal parameters are obtained by mean of the S/N ratio. The
higher the S/N ratio, the more stable the achievable quality. Depending on the required objective characteristics,
there are three types of S/N ratio: the lower-the better, the higher-the-better and the nominal-the-best. To reduce
overloading that can cause unexpected die failure and inadequate die filling forging load need to be minimized.
During hot forging heat transfer from the billet to the die reduces the hardness of the die surface, which leads to the
plastic deformation of the die and ultimately reduces the die life; hence the billet temperature loss needs to be
minimized. For this S/N ratio with a lower -the-better characteristic given by Equation 1 is used for forging load (FL)
and billet temperature loss (dT).