The Mini-Mill Experience: A Self-Paced Introductory Machining Exercise for Mechanical Engineering Students

Buckley, Jenni; Trauth, Amy; De_Rosa, Alexander

doi:10.18260/1-2--48122

Practicing mechanical engineers interface regularly with machinists to design and manufacture components in metal and other engineered materials. Direct, hands-on exposure to precision machining operations, like mill and lathe work, helps young engineers design manufacturable components and facilitates better collaboration with machinists. Mechanical engineering undergraduate programs have been cited for weaknesses in training students on industry-standard manufacturing practices. While there are several excellent examples in the literature of student manufacturing projects, these projects are relatively advanced on the whole, and they require extensive human and capital resources to deploy in large-enrollment classes. Prior investigators have conserved resources by teaming students on projects, which dilutes the hands-on manufacturing experience for individual learners. In this study, we present an introductory mill training exercise for engineering students that allows them to individually develop transferable machining skills but requires fairly modest resources. This exercise, which we call the “Mini-Mill Experience,” involves students individually manufacturing two separate parts with a hobby-grade mini-mill and then completing a written self-reflection documenting their procedures and final part inspection. Students first manufacture a simple part out of reusable wax with direct coaching from a teaching assistant. They then independently manufacture one of six different wooden Erector Set components. The Mini-Mill Experience is designed to give students firsthand experience and promote confidence with the basic mill controls and operations, e.g., changing out an endmill or squaring up a face, that are transferable to the full-sized mills they will use in later courses. The one-time equipment set-up costs for this exercise were approximately $60 per student, with recurring costs of less than $2 per student for stock material. Each student completed the exercise during a two-hour lab period, and it took approximately six weeks for all students in the course (ca. 170 students) to complete the exercise. All sessions were supervised by a machinist and one to two teaching assistants. To gauge the effectiveness of the Mini-Mill Experience, a survey was distributed to all students in a freshmen year mechanical engineering design course. Survey responses indicated that the majority of the students (77%) had no prior experience with mills. Post-activity, students reported high levels of self-confidence in identifying the critical components of a mill and most basic mill operations, like proper use of a vise and tool changes. Compared to students who had prior mill experience, students with no prior experience demonstrated slightly lower self-efficacy with more advanced mill operations like creating blind holes and tapping threads. Post-activity, 75% of students agreed they “were not intimidated or afraid to use the mill to make a part,” and 90% said that they “looked forward to their next experience on a mill.” In this study, we developed an introductory manufacturing experience – the “Mini-Mill Experience” – that is effective in teaching basic mill operations, promotes students’ self-efficacy and enthusiasm for future machining experiences, and is cost effective and scalable for large class sizes. In these ways, it is a valuable addition to the existing literature and curriculum on manufacturing education for mechanical engineers. Future work by our group will focus on whether the skills acquired in the Mini-Mill Experience are transferable to manufacturing experiences later in the curriculum.

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