During the recent years, researchers have been pointing out that the implementation of quality tools in conjunction with simulation technique has not yet been examined in small and medium enterprises (SMEs). With an aim of filling this research gap, the case study presented in this paper was carried out by applying DMAIC phases. After conducting this case study, the occurrence of micro-porosity defect in the castings of a component called bush cam was prevented. This goal was achieved by applying four quality tools namely, brainstorming, cause and effect analysis, normality test and design of experiments and developing the CAD model of bush cam casting. The thermal behaviour of bush cam casting was simulated using this CAD model by inputting different values of the design parameters. The new casting design was implemented in practice, which decreased the defect rate from 8% to 1%. © 2020 Inderscience Enterprises Ltd.