At the University of Kansas in Aerospace Computer Aided Design, AE 421, students .... automotive design, aircraft structure, or building structure that are more ...
Session XXXX
The Practical Integration of Rapid Prototyping Technology into Engineering Curricula Lorin P. Maletsky Department of Mechanical Engineering The University of Kansas Richard D. Hale Department of Aerospace Engineering The University of Kansas
Abstract A recently acquired fused deposition modeling rapid prototyping system has been incorporated into existing engineering courses in the undergraduate Mechanical and Aerospace Engineering curricula at the University of Kansas. The new technology has allowed instructors to provide design and build experiences more similar to what might be seen in industry. The models are created out of ABS plastic and have been used in the design process to test form, fit, and function. In early courses, students use the models to communicate complex three-dimensional geometries and create working models of their concepts. For senior-year projects that are both designed and built, rapid prototype models are used not only during the design process but as functional components of larger systems and scaled models for testing. This paper describes how rapid prototyping technology can be incorporated in many general courses in the engineering curricula to enable improved communication and student experiences without significantly altering course content.
Introduction In today’s marketplace companies are faced with increasing pressure to remain competitive and are constantly looking for ways to improve their product development process. Consumer demand is forcing companies to find ways to reduce time to market in hopes of being the first to bring new products to the consumer. In addition, business owners, stockholders, and the competitive nature of the economy are forcing more companies to find faster and less expensive ways to develop products. New technology is enabling companies to work toward this goal, with rapid prototyping and lean certification leading productivity improvements1. These approaches are not inconsistent -- increased reliance on high fidelity analytical models to enable reduced experimentation leading to certification, and lower cost experimentation on rapid prototypes to enable validation of analytical models. In engineering education the challenge is to develop engineers who are ready to contribute to this highly competitive market right at graduation, especially in design and manufacturing where rapid prototyping can be most useful2,3. It is the obligation of strong engineering programs to not only foster learning of fundamental knowledge Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
but also provide realistic, industrial motivated, and relevant experiences. Modern technology and practices from industry should be part of any strong curriculum. A common question for educators is how to introduce new technologies into curricula already overloaded with fundamentals. This paper offers insights from a first year exercise on integrating rapid prototyping across the engineering curricula of Aerospace and Mechanical Engineering at the University of Kansas and provides a broader application of equipment than similar papers4,5. Four common types of courses are discussed in this paper. The experience of the authors' is that such technology may be readily incorporated into diverse courses with minimal influence on existing content, and that implementation enhances design content in the span of one semester that would otherwise have been avoided due to time constraints on developing functional models.
Drafting and/or Introduction to Engineering Course One of the initial courses that an engineering student might take as part of the curriculum is an engineering drafting or computer aided design (CAD) course. In some schools an effort has been made to incorporate design earlier in the curricula and use this introductory engineering course to better motivate engineering students6,7. Drafting teaches students to visualize three-dimensional objects and communicate those objects in a graphical way. Students are frequently introduced to manufacturing concepts such as tolerances, assemblies, and standard geometries. Most engineering schools use solid modeling software that encourages the students to visualize the part, and create the features in similar ways to how they might be machined. Rapid prototyping can be readily incorporated into a drafting or CAD course to provide a better experience for the students with product design and presentation, as well as aid students who are having trouble visualizing a three-dimensional part8. Students who have trouble understanding how a theoretical part looks in three dimensions or how it would fit with other products will likely have trouble in later courses with more complex components. Engineering students are visual learners and it is believed that the capability to hold an object in one’s hands would dramatically help those students who have trouble visualizing and communicating a component’s geometry; however, one study from Southeast Missouri State University suggests that rapid prototyping does not improve visualization skills for industrial technology students9. The models could be used as an instructional aid where students construct a part from three standard orthogonal views and then check their finished part with a physical model that the instructor had previously built. The prefabricated parts could be used differently depending on the level of the student. Rapid prototyping is a way to fabricate parts designed by students to verify design intent. Simple parts would not be overly challenging; however, designing parts that had to mate with a series of other components would be more challenging and require students to visualize in multiple dimensions. The prototyped part could then be fabricated and checked for fit, allowing for a meaningful hands-on experience for students. For courses that include an open-ended design project, it is possible to rapid prototype components for student use. This technology has been used successfully in a freshman-year Engineering Fundamentals course at Virginia Polytechnic University4 and Northwestern University7 and a similar course using reverse engineering at The University of Texas at Austin6. At this level of course, a firm understanding of rapid prototyping technology or the use of prototypes in the design process may not be required. The technology may better serve the class if used simply as a tool. Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
At the University of Kansas in Aerospace Computer Aided Design, AE 421, students fabricated parts based on team designs. This year's activities included a seemingly simple task for a golf putting training device to reduce the effective target hole diameter thus increasing putting complexity for standard dimension PGA golf balls (Figure 1). A stated desire is that the device be compatible with “standard” holes on practice or putting greens. While the former is a wellestablished standard, the latter offers insight into the complexity of real-world design. The depth of the hole, the dimensions of the hole, the type of cup insert (if any), the depth of the land from the turf to the cup insert, the influence of the device on the ball path and the type of earth each has an influence on the required dimensions and tolerances for proper form, fit, and function. Students are able to develop their visualization skills; verify dimensions, tolerances and assemblies; modify designs based on field tests; and use the product to further communicate their design. Interaction with non-technical customers is enabled via real time demonstrations of function. Students are also introduced to design for affordability, as team printing costs are capped at a challenging level and all developed business plans are required to include prototyping as well as expected manufacturing costs. Within the Mechanical Engineering Curriculum this technology has not been utilized, however, it will be incorporated into this coming freshman year CAD course to help students visualize geometry.
A
· ·
Variable Gap (A) Variable Cup Diameter (B) Variable Turf Height, and Earth Variable Diameter Inserts
·
Select desired putt complexity (inner hole diameter) Insert ring clip, if required Position putting disk, …Putt
· ·
B
·
·
Figure 1. Implementation of Rapid Prototyping in Engineering Drafting and Early Design
V
Design Methodology Course
The use of prototypes during the design process has been shown to improve design quality, decrease time to market for a product, and reduce cost of the product1. Many engineering curricula contain a course where the process of design is taught. This course might include development in areas of oral communication, written communication, interpersonal skills by working in teams, as well as understanding the logical order of design and tools in the design process. Prototyping should be an important part of this process where designers fabricate their ideas for a variety of reasons. In many instances it may simply be to communicate geometry and/or feel of a product to a client. In some cases the prototype may be functional and used to illustrate how a component would work. In all cases the prototype would be used to better understand the product to make design changes and improvements prior to moving into a Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
manufacturing phase. Many of these courses utilize design projects to illustrate concepts discussed in class and provide experiences for students to develop their skills. Since prototyping may be part of the syllabus in such a course, the inclusion of rapid prototyping should be reasonably straightforward. The technology has been used successfully in courses such as “Product Engineering and Manufacturing” at The University of Maryland10 and “Mechanical Engineering Design” at Boise State University11. In such a course it would be appropriate to lecture on the different rapid prototyping technologies that students may see in industry, as well as ways to prototype conceptual designs. Ideally students already have the necessary computer skills to create solid models of the design. Rapid prototyping may be presented as one alternative means to create a prototype, since other methods may be more cost effective in certain cases. Rapid prototyping is best utilized for complex geometries that would be time consuming to fabricate any other way. Size is a concern as the rapid prototyping materials can be costly. Large designs may be best prototyped using other means, where perhaps, only small sections are fabricated using the rapid prototyping machine. Scaling down a concept is possible; however, some features may be lost or the part may have inadequate strength if the concept is scaled down too much. It is important to emphasize to students the reasons for creating a prototype and what they might learn from such a prototype. Following up with students to ensure they understand how a design changes as a result of the prototype is important. Making conceptual models of designs, “just because they can,” should be discouraged. Obviously three-dimensional models can be extremely useful in communicating geometry; however, care should be taken to understand when two-dimensional pictures are sufficient to communicate an idea. In two courses that teach design methodology at the University of Kansas, rapid prototyping has been successfully used. One of the courses in Aerospace Engineering, AE 421, has already been addressed and further exercises will not be discussed here. The other junior-year course is Mechanical Engineering Design Process, ME 501. In both courses the advantages of prototyping as an integral part of the design process are discussed. Student teams undertake open-ended design projects during these courses, although the duration of the projects vary. In AE 421, teams are given one week to develop a product, including a prototype, business plan, and marketing strategy. Rapid prototyping is used to quickly fabricate student designs so that customers can interact with them to affect design. In ME 501, student teams work on the design of a project over the course of a semester. Prototyping is a required part of the design process during the conceptual design period and is one of the deliverables for the class (Figure 2). Once a concept has been selected by teams and some part of the detailed Figure 2. Model of 60-foot structure with a design is completed, teams create physical vertical-axis wind turbine for Mechanical representations of their designs. In some cases Engineering Design Process. Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
models may simply be to better communicate the design to a potential customer, and in others the component functionality is demonstrated. In a class with ten teams, only three took advantage of rapid prototyping technology to physically represent complex geometries in their design. Two of the three designs had functional scaled components. In both courses students had hands-on experiences with their designs, both with fabrication and use, and identified improvements to be made as a result of the prototyping experience. In some cases rapid prototyping reduced the amount of time required to construct a model, as well as improved the quality and function of the prototype and ultimately the final design.
Advanced Design Courses Many advanced courses in design could use rapid prototyping technology to improve education. A curricular sequence might include courses related to typical machine components or machines related to a specific discipline or area of interest. Machine design (e.g. threaded fasteners, gears and gear trains) and mechanisms (e.g. four-bar linkages, kinematics of machine components) are typical courses within a Mechanical Engineering curriculum. Upper level courses might include automotive design, aircraft structure, or building structure that are more discipline specific where students might develop analytical tools to design complex machines or geometries. Other advanced topics in design, such as design for manufacturability, could benefit from rapid prototyping technology. While the use of models may seem similar in advanced design courses and design methodology courses, the objective of their use should differ. In a methodology course the goal is for students to understand and experience prototyping and in an advanced design course the physical models should help students understand concepts taught in those courses. Ideally these courses occur after students are comfortable with creating computer-based solid models. Courses that already contain a laboratory component or project driven design assignment could use rapid prototyping to help students fabricate and work with their designs. One such example is at the University of Nebraska-Lincoln in their Machine Design and Kinematics and Dynamics Laboratories12. In some cases fabricated models could provide a check for the analytical design. Other advanced topics in design or manufacturing could be enhanced with rapid prototyping such as the Advanced Manufacturing course at Purdue University where students prototype a part to be injection molded13 and the Manufacturing Automation and Robotics course at Western Washington University where students prototype concepts for design for automated assembly14. If not addressed previously in a course, this could be a logical place to discuss rapid prototyping technology, although this may not be complementary with existing course material. It would be encouraged to allow students to use rapid prototyping equipment as a tool or a “threedimensional printer.” This may also be an ideal location in the curriculum for instructors to develop educational models to use in class; perhaps physical models of example problems, or models of complicated structures or geometries. In ME 696, Design for Manufacturability, product architecture, component interface, and injection mold design were discussed. Student teams then designed and built hand-held products (video cell phone, multiple device remote control) that could be injection molded to demonstrate these concepts (Figure 3). Rapid prototyping allowed the teams to quickly fabricate and evaluate designs that would have been very hard and time consuming to create (e.g. complex geometries Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
such as ribs, snap fits). Having a physical model allowed student teams to experience the different feel and function of the features, and to make educated decisions on how to improve the design. In a materials and process course the technology can be used to further demonstrate techniques such as casting or fiber reinforced composite lay-up by developing low-cost tools or plugs for subsequent processing. Integrated experimentation for analytical model validation is possible if one considers photoelastic coatings or if subsequent casting utilizes photoelastic resins. Complex motion studies to examine point stresses of interfering mechanisms can be visualized and verified via stress freezing techniques with such materials.
Figure 3. Multi-device remote control for Design for Manufacturability class.
Capstone Design Projects Senior-year capstone design courses are common in many curricula where teams of students are required to apply knowledge they have gained across the curricula to an open-ended design problem, frequently one motivated from industry. These experiences vary in length from multiple projects per semester to a yearlong experience. In many cases the final product of this class is a fully functional physical design. This type of course may or may not be accompanied by a regular lecture period depending on the institution and other courses taught in the curricula. Rapid prototyping can be a great benefit to capstone design teams, especially those who experience the equipment earlier in their education and are aware of its capabilities and limitations. Prototype models can be used in iterative steps throughout the design process to communicate geometry and function to a customer. Teams may be able to check form, fit, and function of the design or components of the design prior to fabricating the final part. If strength and accuracy of rapid prototyped parts are acceptable, teams may be able to create final components for their design. The speed in which prototypes can be created is the greatest advantage of the equipment, allowing teams to focus more resources on design and less on manufacturing. Senior student design teams from both Mechanical and Aerospace Engineering have used rapid prototyping equipment in design projects. The formula SAE car team within Mechanical Engineering used rapid prototyping to create an air intake manifold with variable geometry to experimentally optimize engine performance. The model was surrounded with composite material to provide additional strength during testing. Once the experimental work was completed and the desired geometry determined, another rapid prototype model was generated that fit within the car body. The rapid prototype was then used as a mold to lay-up carbon fiber composite material for the final component. In previous years fabrication of the intake manifold geometry took weeks to accomplish and was not altered once it was created. With the current technology it was possible to create the manifold in one day. Rapid prototyping allowed students Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
to perform experiments on the design to improve geometry and then create a final version. A team within Aerospace Engineering created rapid prototype parts for air intakes on a flying platform (Figure 4), again allowing students to concentrate more time onvehicle and control system design and less on fabrication. Another student team designed a satellite with a 6-inch stiffened cube geometry. The team was able to quickly fabricate the external shell of the satellite and concentrate on fitting components within the limited space. This team in particular found that allowing people to see and touch the outside geometry of the satellite greatly helped them understand the design challenges due to Figure 4. Flying platform for Senior the relative small size. Another team was also Capstone Design. able to easily fabricate their final design concept for an airplane to show potential customers. In all examples provided, speed of fabrication of a prototype or a functional model allowed design teams to spend more time on another area of the design that otherwise might have been ignored.
Other Factors to Consider There are a number of different rapid prototyping technologies that can be used in an engineering curricula. These designs differ in a number of areas including cost of required equipment, cost of materials, build time, strength of fabricated parts, and part accuracy and tolerance. Each institution will have different desires that will need to be identified when looking for an appropriate machine. At the University of Kansas a Stratasys Inc. Prodigy Plus machine that uses fused deposition modeling was purchased for use in the engineering curricula (Figure 5). The material is ABS plastic and costs approximately $4.31 per cubic inch including support material. An hourly rate when the machine is in operation is assessed to generate funds to continue the equipment support warranty. In the experiences described, build times ranged from less than one hour for small parts to over thirty hours for larger, more complicated geometries. The strength of a fabricated part is determined by a number of variables during the build process and not easily quantifiable, although there are a few labs that have measured the strength of simple geometries15,16. The machine has a build volume of 8"x8"x10" with a minimum layer thickness of 0.007" and a nominal toolpath width of 0.012". Cost will most likely be an important consideration when selecting a machine for use. There is a wide range of machines that can generate rapid prototype models from solid geometries. To effect the broadest use of models across the curriculum requires reasonable material and fabrication costs, possibly at the expense of part strength and accuracy. In a course with multiple teams of students iteratively fabricating designs throughout the semester, these costs will accumulate quickly. Instructors should approve designs to ensure that models are created for good reason, and that students understand how they will use the prototype to improve the product final design. At The University of Kansas all teams or individuals who desire to fabricate a Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
model are required to submit a memo to the instructor or someone who can approve the expenditure. This memo must include a computer generated threedimensional picture of the part along with overall dimensions. The students must also explain how they will use the prototype to improve the final design or how it will be part of the final design. Teams are also encouraged to obtain an estimate for the costs associated with building the model. This method has been successful to document all models constructed and force students to think about its use. Follow-up information is generated in each class and with the instructors. At KU student teams have not directly built models themselves. A research assistant has been trained to use the equipment and act as an informational resource for Figure 5. Stratasys Prodigy Plus students. This person is the one who actually starts the Rapid Prototyping System. build process and performs any required postprocessing (usually the removal of support material). The cost structure developed includes paying this person an hourly rate. In some cases this can be accomplished by the instructor or perhaps even the student teams themselves. Most rapid prototyping systems will include tutorial material that may take a few hours to learn. One possibility is to train individual members of the various design teams on how to use the software and equipment, minimizing instructor investment of time. Rapid prototyping equipment has also enhanced interaction with other groups at the university, aided outreach with the public, and provided cooperative efforts with local industry. The ability to quickly fabricate physical models is desired by not only engineers but any design related discipline. Industrial design students have been able to fabricate conceptual designs that might have taken many weeks to create. For them, shortening the fabrication process can be critical to their success. Rapid prototyping has also brought together instructors from Industrial Design and Engineering at Rochestor Institute of Technology where a rapid prototyping laboratory was created17. Similar experiences with architecture students that are required to create models of structures have been seen, especially complicated structures involving irregular and blended curves that would be nearly impossible to physically duplicate by hand. Tours and open houses with the public have shown a great interest in rapid prototyping technology, probably because it is visual and relatively easy to observe and understand its uses within engineering. Local industry working with student teams have also benefited from the technology due to the speed in which prototypes and final designs can be generated.
Conclusions The use of rapid prototyping technology in the curricula of the Mechanical and Aerospace Engineering Departments at the University of Kansas has improved the experience of the Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
students and better prepared them for industry. This paper has provided suggestions for use of the equipment at many stages throughout an engineering students educational experience, from introductory courses in engineering for first-year students to senior-year capstone design experiences and upper-division technical electives. Rapid prototyping has enabled instructors to provide hands-on design experiences for students and allows them to focus more time on course material, and less time on fabrication of conceptual designs.
Acknowledgements Partial funding to acquire the rapid prototyping equipment has been provided by The National Science Foundation (DUE CCLI-A&I award #0127081), the Kansas University Center for Research, and the University of Kansas Mechanical, Aerospace, and Civil, Environmental, and Architectural Engineering Departments.
References 1. Thilmany, J., 2001, “Printing in Three Dimensions,” ASME Mechanical Engineering Magazine, May. 2. Nyaluke, A.P., An, D., Leep, H.R., and Parsaei, H.R., 1995, “RAPID PROTOTYPING: A New Tool to Bridge Design and Manufacturing,” Proceedings of the ASEE Annual Conference, 1995, pp. 2658-61. 3. Sullivan, L., Erevelles, W., and Lai, G., 1997, “Implementing Concurrent Engineering Through Rapid Prototyping and Manufacturing – An NSF-Funded Project,” Proceedings of the ASEE Annual Conference, Milwaukee, WI, June 15-18, 1997, Session 1526. 4. Bøhn, J.H., 1997, “Integrating rapid prototyping into the engineering curriculum – a case study,” Rapid Prototyping Journal, Vol. 3, No. 1, pp. 32-37. 5. Stamper, R.E., and Dekker, D.L., 2000, “Utilizing Rapid Prototyping to Enhance Undergraduate Engineering Education,” Proceedings of the ASEE/IEEE Frontiers in Education Conference, Kansas City, MO, October 18-21, 2000, Paper F3C-1. 6. Barr, R.E., Schmidt, P.S., Krueger, T.J., and Twu, C.Y., 2000, “An Introduction to Engineering Through an Integrated Reverse Engineering and Design Graphics Project”, Journal of Engineering Education, Oct., pp 413-418. 7. Hirsch, P., Shwom, B., Anderson, J., Olson, G., Kelso, D., and Colgate, J.E., 1998, “Engineering Design and Communication: Jump-starting the Engineering Curriculum,” Proceedings of the ASEE Annual Conference, Seattle, WA, June 28 - July 1, 1998, Session 3253. 8. Zecher, J., 1998, “Integration of a Rapid Prototyping System in a MET Curriculum,” Proceedings of the ASEE Annual Conference, Seattle, WA, June 28 - July 1, 1998, Session 3549. 9. Frey, G. and Baird, D., 2000, “Does Rapid Prototyping Improve Student Visualization Skills,” Journal of Industrial Technology, Vol. 16, No. 4, pp. 1-6. 10. Zhang, G., Cunniff, P., and Dally, J., 1997, “Teaching New Product Development through a Product Engineering Approach,” Proceedings of the ASEE/IEEE Frontiers in Education Conference, 1997, pp.1573-1578. 11. Eggert, R., Bunnell, D., and Tennyson, S., 1998, “Designing Across the Curriculum: Linking Sophomores to Mechanical Engineering,” Proceedings of the ASEE Annual Conference, Seattle, WA, June 28 - July 1, 1998, Session 2566. Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
12. Szydlowski, W.M., 2001, “Using a Rapid Prototyping Machine in the Integrated Kinematics, Dynamics, and Machine Design Lab”, Proceedings of the ASEE/IEEE Frontiers in Education Conference, Reno, NV, October 10-13, 2001, Paper S2E-11. 13. Anderson, J.C., 2002, “Teaching the Manufacturing Design Cycle in a Project Course,” Proceedings of the ASEE/IEEE Frontiers in Education Conference, Boston, MA, November 6-9, 2002, Paper F4D-1. 14. Newcomer, J.L., 2002, “Using Rapid Prototyping to Teach Design for Automated Assembly Principles,” Proceedings of the ASEE/IEEE Frontiers in Education Conference, Boston, MA, November 6-9, 2002, Paper F4D-12. 15. Ahn, S., Montero, M., Odell, D., Roundy, S,. and Wright, P.K., 2002, “Anisotropic material properties of fused deposition modeling ABS,” Rapid Prototyping, Vol. 8, No. 4, pp. 248-257. 16. Rodriguez, J.F., Thomas, J.P., and Renaud, J.E., 2001, “Mechanical behavior of acrylonitrile butadiene styrene (ABS) fused deposition materials. Experimental investigation,” Rapid Prototyping Journal, Vol. 7, No. 3, pp. 148-158. 17. Gupta, S.K., and Hefner, R.J., 1995, “Rapid Prototyping Laboratory at RIT,” Proceedings of the ASEE Annual Conference, 1995, Session 3564. LORIN P. MALETSKY Dr. Maletsky is a third-year Assistant Professor in the Mechanical Engineering Department at the University of Kansas. In the undergraduate curriculum he teaches Mechanics of Materials and Mechanical Engineering Design Process. At the graduate level he has taught Design for Manufacturability and Applications of Biomechanics. He obtained his undergraduate degree from Rutgers, the State University of New Jersey, and his graduate degrees from Purdue University. His research interests include biomechanics of the lower limb, biologically inspired machines, and design for manufacturing. RICHARD D. HALE Dr. Hale is a fifth-year Assistant Professor in the Aerospace Engineering Department at the University of Kansas. In the undergraduate curriculum he teaches Computer Aided Design, Structural Analysis, Finite Element Analysis, and Materials and Processes. At the graduate level he teaches composite materials and structures. His expertise is in the areas of engineering mechanics, experimental mechanics, and composite materials and structures. He received his B.S. in Aerospace Engineering from Iowa State University in 1988, his M.S. in Mechanical Engineering from Washington University in 1991, and his Ph.D. in Engineering Mechanics from Iowa State University in 1995.
Proceedings of the 2003 ASEE Midwest Section Meeting University of Missouri-Rolla Copyright ã 2003, American Society of Engineering Education
