2023 ASEE Annual Conference & Exposition

Mechanical Engineering Capstone Senior Design at University of X (UX) challenges students to combine design, fabrication, and manufacturing skills to produce working pre-commercial product prototypes for customers external to the course. Parts must be created via appropriate manufacturing methods using available lab equipment. Historically at UX, Capstone parts were machined. However, machining some of the components requires special equipment and tools, which are not available in the lab, and purchasing commercial off-the-shelf products directly is expensive. In response, we acquired a tabletop casting kiln (originally meant for jewelry casting) and used it to sand cast aluminum 6061 parts for Capstone. Part patterns were 3D printed in PETG and used to build up green sand molds. Pattens were then removed, producing a hollow cavity into which molten aluminum from the kiln was poured. For the 2022 Summer course, only conventional sand casting was allowed, but 3D printed patterns also enable lost wax (lost PLA) casting, which will be explored in future UX ME Capstone courses. UX mechanical engineering students receive hands-on exposure to machining in earlier classes, but they have never experienced casting. We were therefore curious how availability of this new manufacturing technique would influence their Capstone design and fabrication plans, if at all.
The kiln, a QuikMelt Pro 120 top loader from Tabletop Furnace Company, provides 1500 watts, heating to over 2200 F, and costs less than $600. Thus, casting is within the budget of most engineering Capstone programs, but is it worth the investment? How does access to sand casting capability influence design decisions engineering students make in Capstone? Does it change their enjoyment and/or perception of the class?
To answer, we deployed a 5-question open ended survey to the first Capstone class, 2022 Summer, for which the casting foundry was available. A total of 9 out of 13 students enrolled responded to the survey, and we applied qualitative examination and thematic analysis and coding to evaluate the results.
Students identified practical limitations including observations that 3D printed features smaller than 5 mm did not resolve well because sand particles adhere to the 3D printed pattern layers. This issue was minimized by printing layer heights of 0.1 mm. Sanding surfaces to create a smooth finish on the filament layer lines was also recommended.
Another opportunity casting affords is recovering machining scrap to facilitate in-house metal recycling and reduce waste. Coordinating recycling with classes emphasizing machining provides significant reduction of material waste from subtractive manufacturing processes. Feeding waste metal into the kiln can produce billets whose value quickly recoups the cost of the kiln.