Parametric optimization of the investment casting process using utility concept and Taguchi method

Investment casting process, also known as lost wax process, is utilized when complex detail, undercuts or non-machinable features and accurate parts are desired. It begins with a wax pattern which is an exact replica of the as cast part. So the properties of the wax patterns are ultimately passed on to the castings. This article highlights the application of utility concept with Taguchi method for the multi-response optimization of wax patterns made by the investment casting process. The wax injection process parameters considered are injection temperature, injection pressure and injection time, whereas the responses are linear shrinkage, surface roughness and penetration, respectively. The experiments are planned as per Taguchi’s L₉ orthogonal array. The utility concept converts multi-response optimization problem into single response optimization problem and thereafter Taguchi method is applied. The results indicate that injection pressure is the most significant process parameter influencing the quality characteristic of the wax patterns. The confirmation tests with optimal levels of injection process parameters are carried out to illustrate the efficacy of the proposed method. The results are found to be within the confidence interval. The optimization results revealed that a combination of lower level of injection temperature and injection time along with higher level of injection pressure leads to overall improvement in the quality of the wax patterns. It has also been established that there is some quality loss in terms of surface finish of the wax patterns in multi-response optimization as compared to single response optimization, though an overall improvement in the process is being observed.