The purpose of the research was to reduce the proportion of block rubber contaminated with iron from the production process while all relevant constraints were taken into account. According to the current problem situation, the extent of the contaminated rubber was higher than the acceptable upper range. The analysis was conducted using the Cause-and-Effect diagram and the Failure Mode and Effect Analysis method (FMEA). It was found that the contamination issues were mainly caused by the lack of the iron separation machine, the inefficient magnet set used to withdraw iron debris from rubber raw materials, and the low-performance inspecting system for rubber shredder blades. Lean Six Sigma approach was then utilized to tackle the problems. The practiced alterations included the new iron separation machine installation in the production line, more magnet sets assembled inside rubber raw materials storages, at the shredded rubber screening machine and the base of the shredder blades, and a record-keeping logbook for the blades. The integrated approach decreased the fraction of the problematic iron-contaminated rubber by 17.97 percent. The capability analysis, C_pk, is 1.50 with a 0.05 significance level, which indicated the highly efficient process. The confidence interval of the process is 1.08 < C_pk < 1.93. The forecasted reduced cost from rubber reprocessing was 924,630 Baht per year.