Robust design optimization of HDPE friction stir welding process using the static RDPP-SF and Taguchi-grey methods: A comparative study

The paper aims to analyze and optimize the FSWing process of plates in a butt configuration. The ultimate objective is to desensitize the process to both endogenous and exogenous noises, which are lacing the manufacturing process.. To this end, the Robust Design for Products and Processes using the stochastic frontier (RDPP-SF) and the Taguchi-Grey methods are employed, and settings of the process parameters, which yield the best mechanical performances, are sought. The process parameters are the pin rotation speed (x 1 ), feed rate (x 2 ), and plunged surface (x 3 ), whereas the process responses are the longitudinal stress (σ L ), transverse stress (σ T ), longitudinal strain (ε L ), and transverse strain (ε T ) that occur in the FSWed seams. Three replications of an FCCD design are conducted and then statistically analyzed. For the RDPP-SF method, the optimal mechanical properties are σ L = 22.197 MPa, σ T = 22.607 MPa, ε L = 18.33 %, and ε T = 15.83 % and they occur when setting the rotation speed (x 1 ) at 1700 rpm, the feed rate (x 2 ) at 29 mm/min, and the plunged surface (x 3 ) at 478 mm 2 . The optimal values with regard to the Taguchi-Grey method are achieved at, σ L = 23.733 MPa, σ T = 23.886 MPa, ε L = 17.76 %, and ε T = 16.91 % while setting the rotation speed (x 1 ) at 1280 rpm, the feed rate (x 2 ) at 29 mm/min, and the plunged surface (x 3 ) at 478 mm 2 . The discrepancy between the RDPP-SF and the Taguchi-Grey method is partly due to the variance decomposition models, which are employed.