Application of Six Sigma DMAIC methodology to improve the competency rate of students in a lathe machining course

Low competency rates in practical machining courses remain a persistent challenge in manufacturing engineering education. This study applied the Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) methodology to a lathe machining course in which only 13.3% of 60 students initially met the competency standard, with deficits spanning dimensional accuracy, surface finish, machine setup, and safety practice. Following measurement system validation through Gage R&R analysis, root cause analysis traced poor performance to systemic instructional factors insufficient practice time, subjective grading, and the absence of standardized procedures rather than student background. Targeted interventions were implemented, including standardized work instructions for all ten lathe operations, competency-based progression requiring demonstrated proficiency before advancement, and weekly formative assessment. After the intervention, 91.7% of students achieved competency (χ ²  = 73.818, p < 0.001), with mean scores improving from 51.3 to 70.5 (t = −46.78, p < 0.001) and process capability rising from Cpk = −0.34 to 0.43. In practical terms, students machined workpieces with dimensional variation reduced by nearly two-thirds, selected cutting parameters deliberately rather than by guesswork, performed chuck centering and machine setup independently, and showed the greatest gains in traditionally difficult operations such as knurling, boring, and parting off. Statistical process control charts confirmed the improvements were sustained. The study provides a framework for applying industrial quality methodology to hands-on skills education.