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Case Study of Cost-Effective Design Alternatives

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2011 ASEE Annual Conference & Exposition


Vancouver, BC

Publication Date

June 26, 2011

Start Date

June 26, 2011

End Date

June 29, 2011



Conference Session

Design Education I

Tagged Division


Page Count


Page Numbers

22.311.1 - 22.311.25



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Paper Authors


Louis Reifschneider Illinois State University

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Associate Professor,
Registered Professional Engineer,
Research interests include product design, net-shape manufacturing, and sustainable technology.

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RJ Linton Illinois State University

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RJ Linton is an adjunct professor in the department of technology at Illinois State University. He can be reached by email at

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Case Study of Cost-Effective Design AlternativesA good story is often the best way to relate technical information to students. This paper presentsthe story of a small company seeking a cost-effective but attractive way to protect the electroniccomponents of its educational robot. The objective of this paper is to inform students new to thesubject of design for manufacturability about how there is often more than one way to solve aproblem. The case study presented in this paper is based upon actual design iterations to solvethe problem of shrouding the small mobile robot. Three alternatives are considered: fabricationfrom laser-cut plastic panels, thermoforming from plastic sheet, and injection molding. Aneducator could use this paper as a case study for students to teach them about the choicesavailable when determining the best design and corresponding process to make a cost-effectiveproduct. Further, the example of a small educational robot is one that will be of interest to manycollege students.The three alternatives represented in this paper cover the spectrum of manufacturing processes.The fabrication process represents the classic separation-and-assemble approach.Thermoforming is a near net-shaped process that will require some secondary milling operationsto create the desired product. Finally, injection molding is the net-shaped process thatconsolidates material into a single shape that when ejected from the mold is the desired product.The purpose of this paper is to educate the reader about the special tooling required for eachprocess, the intrinsic design benefits each offers, and ultimately what production volumes willdetermine the most cost-effective design based upon their respective economies of scale. Forexample, it is shown that the fabrication method with a low initial cost will have higher relativevariable costs than the alternatives. Injection molding is the most capital intensive process buthas the lowest variable cost.The paper is richly illustrated with computer-aided renderings of design details related to eachprocess: a layout of the fabrication approach, section views of a thermoformed part andcorresponding mold, and section views of the injection molded part and corresponding mold.The merits of each process is annotated in the CAD drawings and summarized in a productfeature versus process table. Further, a comprehensive cost summary table is presented toeducate the reader about the capital and incremental costs associated with each alternative. Thecost factors quoted are based upon actual quotations from companies specializing in makingproducts using the three alternative processes showcased in the paper. Using the data from thequotations, a graphic illustration of the unit cost change with the order size for each process ispresented. Such information is used by the designer to determine the most cost-effective methodto accomplish the design objective. In summary, the subject matter, the quality visualinformation, and the comprehensive cost information make this paper a story of interest for areader wanting to learn about cost-effective design for manufacturability.

Reifschneider, L., & Linton, R. (2011, June), Case Study of Cost-Effective Design Alternatives Paper presented at 2011 ASEE Annual Conference & Exposition, Vancouver, BC. 10.18260/1-2--17592

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