Generally, it is difficult to produce homogenous deformation in
MFP because of the presence of friction at the interface of the
die/workpiece. In most of the MFP, since friction is undesired
factor which has to be reduced as much as possible in order
to have realistic material flow, low deformation load as well as
the better product quality, the main and interaction effects have to be first determined and then taken into consideration for the
analysis of MFP.