Application of Taguchi-based Six Sigma method to reduce defects in green sand casting process: a case study

摘要

Six Sigma is a systematic method for process improvement. It relies on statistical and scientific methods to reduce the defect rates and achieve improved quality. A case study carried out for a green sand casting manufacturing company. Here, Six Sigma methodology is used for the part: bearing bracket 3809. Define-measure-analyse-improve-control (DMAIC) methodology along with Taguchi method is used to minimise the defects in the bearing bracket 3809. The major tools used in this work are the project charter, process map, statistical graph and cause-and-effect diagram. Use of design of experiment (DOE) and analysis of variance (ANOVA) techniques are combined to determine statistically the correlation of defects with the mould hardness, moisture content, green strength, permeability of sand, pouring rate and pouring temperature and also to find their optimum values needed to reduce/eliminate the defects. The experimental results were statistically analysed and modelled through Taguchi analysis. Based on the findings, the optimised process parameters are taken for experiment and better performance obtained in the production process was confirmed. The comparison between the existing and the proposed process has been attempted in this paper and the results have been discussed in detail.