Abstract:
The research applied the six-sigma method to appropriate proportion of dust rock in ready mix concrete. The six Sigma approach has five steps in working process, which are Define Phase, Measurement Phase, Analysis Phase, Improvement Phase and Control Phase, respectively. This research followed the five steps as follows: 1) Define Phase, defined the problems of the specified factory it is increase cement 30 kg in Mix-Design with effect to cost of Material so that the factory must reduce cost by use dust rock replace in sand 2) Measurement Phase, started with the inspection of measurement system which had the result that met the acceptance criteria. Next, analyzed the problems by using fish bone diagram to get 17 factors. Then, screened the factors with Cause and Effect Matrix. 3) Analysis Phase, analyzed these 4 factors by using statistical method which verified that these factors contributed to defect occurrence. 4) Improvement Phase, used factorial experimental design to conduct experiment two times in order to get optimal value of each factor. 5) Control Phase, established guidelines to control and minimize the defect amount after an improvement. After improvement for using dust rock in ready mix concrete the results before and after the improvement were compared. The percentage of defect amount decreased from which means that the using dust rock in ready mix concrete could reduce cost 67 baht