Optimisation of percent dilution and HAZ width of submerged arc weldment using Taguchi philosophy coupled with fuzzy inference system

In any manufacturing system, multi-objective optimisation problem is usually encountered because it is desired to improve multiple criteria of the process/product simultaneously. However, it is really difficult to solve such problems due to the complex process behaviour. The control parameters (process factors) interact in a complicated manner thereby influencing various process outputs. Direct (main effect) as well as interactive effect of process parameters are to be examined carefully to select the most favourable process environment to achieve desired level of quality output. Taguchi optimisation method is very popular in production engineering field; however, the method fails to solve multi-objective optimisation problems. Therefore, to solve a multi-objective optimisation problem, it is customary to convert multiple objectives into a single performance index (single objective function) which can be optimised finally by Taguchi method. In this work, a fuzzy logic approach has been adopted here to optimise the process environment and to produce quality product. By this approach, the imprecision and uncertainty in experimentation as well as data analysis can be handled conveniently. The study highlights a case study of optimising process parameters to satisfy contradicting requirements of multiple bead geometry parameters of submerged arc weld.