The New 3-D Printer is Here, What do We Do Now? Rapid Prototyping in the Undergraduate Engineering Environment

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1 The New 3-D Printer is Here, What do We Do Now? Rapid Prototyping in the Undergraduate Engineering Environment H. Joel Lenoir 1 Abstract Rapidly declining prices are making rapid prototyping machines increasingly attractive to undergraduate engineering education. Western Kentucky University has been using one of the smaller 3-D printers for nearly two years in the Department of Engineering. Although other rapid prototyping machines have been available on campus in the past, this is the first machine widely available for student use. The machine has had a profound impact on the design skills of the students. They now view prototyping as an integral phase of the design process, whether virtual or rapid prototyping. However, use of the machine has revealed some unexpected problems when included as a tool available to the student. For instance, the motto think it, draw it, print it has led to designs that can only be made on the 3-D printer. Problems such as this and the resulting opportunities for student learning are included. Keywords: rapid prototyping, design, fabrication. INTRODUCTION The Department of Engineering at Western Kentucky University (WKU) has been using a Dimension SST rapid prototyping machine for nearly two years. The Civil, Electrical, and Mechanical Engineering programs have utilized the printer in a wide range of design experiences at various points in their respective four-year curricula. Many other authors have discussed the impact of rapid prototyping in their programs, whether with a single machine [Jordan, 5] or with a wide range of prototyping techniques [Jensen, 4]. Their experiences are similar to those at WKU, but WKU has found the motivation for the use of rapid prototyping is different for each discipline. Some applications represent the need for sophisticated parts that cannot be produced by conventional or even CNC machining. Other projects are an element in repetitive design-build-test experiences with a need for quick digital and physical prototypes. In addition, the machine is used to make simple parts for students with limited machining skills. Faculty and staff also make use of the machine for their projects, whether for regional industrial partners or for individual projects. The machine has proven to be a valuable addition to the department, with jobs for regional industry partners providing sufficient resources to support extensive student usage. TECHNOLOGY SELECTION The faculty realized the first decision to be made when selecting a first 3D printer was not the budget, but was rather a philosophical decision on the method of model creation. Searches on Internet revealed two basic choices are available: additive printing or subtractive machining. Additive printing implies the creation of models by the addition of material to a base to create a prototyped part from a drawing. Subtractive machining uses high-speed 1 Western Kentucky University, Dept. of Engineering, Bowling Green, KY 42101, joel.lenoir@wku.edu

2 cutting tools to form the finished part from an initial block of material. Various technologies are used to create the part, but the specific method of prototyping was judged to be a secondary decision after the selection of additive or subtractive. Additive printing has the advantage that printed parts are generally ready for evaluation and use, with some techniques yielding components suitable for immediate use in actual devices. The major disadvantage is that each manufacturer has a different material used in their machine, which can limit the usefulness of some parts due to material restrictions in usage environment or loading. The accuracy of the machines can be very high, producing parts that can be used in assemblies with a high degree of fidelity to actual production parts. The additive process also allows creation of parts that cannot be machined or molded. As long as a suitable CAD file can be created, the part can likely be printed on an additive printer. Subtractive machining typically implies the use of small precision CNC mills or routers to cut the prototype from a block of material. Specialized machines are widely available for this use, with control software allowing for optimized operation. Subtractive methods produce robust parts from a wide range of materials, accommodating a wide range of service environments. The main disadvantage was determined to be the ability to produce only those parts that can be machined. Clearance for the cutters and the inability to form internal voids of odd shapes may limit the types of parts produced. However, the ability to create strong and rigid parts is a strong positive that may overshadow the limitations of part production. After a period of review by the faculty and a discussion with regional industrial partners about their needs, a decision was made to pursue an additive printing machine. Meetings with various vendors, visits to trade shows, and reviews from consultants [Grimm, 2 & 3] in WKU s economic development region, along with college budget negotiations narrowed the search the two vendors: Dimension (a division of Stratasys, Inc., and Z Corporation ( Other technologies such as Dimension offers a fused deposition modeler using ABS plastic in layers 0.01 thick to build a model on a base. A different plastic is laid down in the layer to support holes and voids, and this support material can be broken out by hand or washed out with water depending upon the machine selected. The Z Corp. machine sprays a binder agent onto a thin layer of powder, and repeats the process in layers until the entire part is complete. Prices of both machines were competitive, and various decision analysis techniques continued to show no substantial advantages. The decision was ultimately made during a hot Kentucky summer when extremely high (but normal) humidity in a design office of a regional firm caused the powder-based component to get friable and crumble within a week. Once the Dimension machine was the primary choice, a decision was made to select the version with the water soluble support material. A regional company assisted in this decision, sending a part file as shown below in Figure 1. This 3 part has numerous voids and holes, and was printed by Dimension with both breakout and washout machines. The difficulty in removing the breakout material was very high, and when assured by this and other companies that this part complexity was typical in our region, the decision was made to purchase the more expensive water soluble Dimension SST printing machine. Budget concessions with other projects were available to add this feature. Figure 1: Common Industrial Part for Rapid Prototyping

PROTOTYPING PROJECTS A wide range of projects have made use of this rapid prototyping machine. As discussed above, the three programs at WKU have different needs for the machine.

heaviest user of the machine. The ME curriculum has an integrated series of design courses [Byrne, 1] spanning the entire four years.

Since each ME student has a course in SolidWorks, the creation of parts ready to be 3D printed is an easy matter for them. A common use of the printer is the ASME Design Competition.

In fact, the machine on the left won the regional competition and moved to the national competition in Florida.

the single reason of creating 3D parts. The example below is typical of a part created by an EE student.

3 PROTOTYPING PROJECTS A wide range of projects have made use of this rapid prototyping machine. As discussed above, the three programs at WKU have different needs for the machine. Support for these student activities is subsidized by the work done for regional industrial partners Student Projects As might be expected, the WKU Mechanical Engineering (ME) program is the heaviest user of the machine. The ME curriculum has an integrated series of design courses [Byrne, 1] spanning the entire four years. Students have multiple opportunities to create prototypes, some with traditional machining but with an increasing number utilizing rapid prototyping. Since each ME student has a course in SolidWorks, the creation of parts ready to be 3D printed is an easy matter for them. A common use of the printer is the ASME Design Competition. This past year two teams from the Junior design course built stair climbing robots using a range of mechanical components made on the 3D printer. In fact, the machine on the left won the regional competition and moved to the national competition in Florida. Figure 2: Competition Vehicles for Mechanical Engineering Students in the EE program do not take a drafting course, but they have shown enough initiative to learn SolidWorks on their own time for the single reason of creating 3D parts. The example below is typical of a part created by an EE student. It is a body for an IEEE robot competition, and contains mounting and locating features for sensors and circuit boards. This part is relatively large, utilizing approximately $350 of materials in this single part. However, due to the complex nature of the shape, fabrication with traditional tools would require attachment of individual parts to create an assembly. To prevent alignment errors, this work would have to be done very carefully. The 3D printer removes this source of error and assembly time. Figure 3: Complex Part from Electrical Engineering

The Civil Engineering program has created the most unusual student objects with the printer, ranging from models of concrete canoes to the pattern for a concrete frisbee shown below.

The longest survivable throw is the goal, and depends very strongly on the disc shape for both distance and shape.

4 The Civil Engineering program has created the most unusual student objects with the printer, ranging from models of concrete canoes to the pattern for a concrete frisbee shown below. It is used in a student competition where flying discs are molded from concrete and thrown after curing. The longest survivable throw is the goal, and depends very strongly on the disc shape for both distance and shape. Students design their sectional profile, and then rotate them to create a virtual solid. These solids are connected together in a compact stack for printing, and appear similar in structure to the inside of a hornets nest. After printing, the individual discs are separated and serve as patterns for plaster molds for use in forming the concrete. Figure 4: Pattern for Concrete Frisbee Many of these student uses are for competitions. Students often are on short deadlines, and desire to have complex parts created quickly. As the concrete disc illustrates, they are ingenious in finding practical uses for the printer to solve difficult tasks. However, not all projects are school related. They do have some freedom to use it for entrepreneurial projects such as the pattern for a resin mold below. A student was interested in creating a business selling cobblestone elements to a castle building craft group, and used the printer to create this part to serve as the master pattern for a series of flexible molds for casting plaster. Other projects have included sensor housings for experimental devices, support pieces for machine elements, and components for model aircraft. Industrial Projects Figure 5: Entrepreneurial Pattern for Plaster Cobblestones Of course, industrial projects make up the heaviest use of the machine. Although many projects remain confidential, parts such as those in Figure 1 and in Figure 6 below show the range of projects completed. A surprising number of jobs has started to come from small startup companies needing parts for evaluation of design and for solicitation of state entrepreneurial funds. Figure 6 is a new product from a regional company slated to hit

the commercial this year. Although this figure is an assembly view, sample parts of key design elements were printed by WKU students for use in consumer review sessions.

5 the commercial this year. Although this figure is an assembly view, sample parts of key design elements were printed by WKU students for use in consumer review sessions. The results of these sessions lead to improvements which ultimately resulted in the awarding of a major state grant for further product development and marketing. Figure 5: Regional Entrepreneurial Project for Startup Company LESSONS LEARNED Prototyping activities over the last two years has yielded various keys to success, some learned easily while others were more costly. Experience has shown that students are respectful of the cost of part printing, but that the machine must remain on a restricted basis. A faculty member or staff person must review each part before committing resources to its creation. For parts supporting a class experience, a faculty signature is now required on the part drawing to assure the operator that an adequate needs assessment and overall design feasibility has been performed. Students wanting to do individual work must collaborate with a faculty member before the part can be printed. However, care must be taken to not discourage students, but rather to help them see that these reviews are useful and typical in industry. The most difficult lesson for students and faculty is to respect that rapid prototyping machines have the ability to create extremely complex parts. Although this is perhaps the machines greatest strength, it is a dangerous trap for the inexperienced engineer. Many parts created on the WKU machine could not be made by conventional machining, and some could not even be injection molded by segmented molds. The 3D printer must never be a replacement for good Design for Manufacturing (DFM) instruction and practice. This is likely to be the greatest barrier to its success in a design-based curriculum since students will tend to rush this step and move to fabrication. One way around this problem is to have the students discuss their DFM analysis as part of their project design report. This forces the printer into the role of design verification instead of design replacement. Students can play a key role in the success of the machine is they become advocates to local companies for rapid prototyping. WKU is in the process of using student workers to create a business serving regional interests. The students already possess the greatest amount of operational knowledge of the machine, and they simply need to formalize the processes so later cohorts can learn them more quickly. The goal is charge external users enough to maintain the machine and support student use, but not charge such a large rate as to discourage usage. This has been a common complaint in our region, but WKU has begun to address these concerns in consultation with our Industrial Advisory Board. The most difficult operational issue with the machine has not been inappropriate use, as initially feared by the administration, but rather trying to balance time lines with internal and external customers. The Dimension SST is

6 very accurate, with a reasonable part finish, but it is rather slow. Great care must be taken in scheduling work so that customer deadlines can be met. The longest single printing job was 142 continuous hours, requiring multiple machine material refills. Jobs of this nature sometimes require night and weekend service visits by students or faculty, but are necessary for machine operation to be economically viable. The intention is to use job shop scheduling software to streamline this process. CONCLUSIONS An appropriate rapid prototyping machine can be a valuable complement to the undergraduate engineering curriculum. If students have supervised use of the machine, with appropriate design scrutiny before printing, they will find innovative ways to create parts that are useful and aid in their design education. It is the responsibility of the faculty to ensure students recognize that devices such as 3D printers can create parts that not only cannot be machined, but could not even be molded with expensive tooling. The students cannot be allowed to substitute good design for rapid part generation. Collaboration with industry can provide support for student usage while allowing students to assist companies in fulfilling their development needs. REFERENCES [1] Byrne, Chris, Robert Choate, Joel Lenoir, and Kevin Schmaltz, Integrated Professional Component Plan from Freshman Experience to Senior Project, Proceedings of the 2004 American Society for Engineering Education, Salt Lake City, 2004, Session [2] Grimm, Todd, 3D Printer Dimensional Accuracy Benchmark, self published white paper, T. A. Grimm & Associates, Edgewood, KY, USA, [3] Grimm, Todd, Rapid Prototyping Benchmark: 3D Printers, self published white paper, T. A. Grimm & Associates, Edgewood, KY, USA, [4] Jensen, Daniel, Chris Randall, John Feland, and Martin Bowe, A Study of Rapid Prototyping for Use in Undergraduate Design Education, Proceedings of the 2002 American Society for Engineering Education, Montreal, Quebec, Canada, 2002, Session [5] Jordan, William and Hisham Hegab, Introducing Rapid Prototyping into Different Classes, Proceedings of the 2004 American Society for Engineering Education, Salt Lake City, 2004, Session H. Joel Lenoir H. Joel Lenoir is the Layne Professor of Mechanical Engineering at WKU, and primarily teaches in the dynamic systems and instrumentation areas. He received his B.S.M.E and M.S. degrees from the University of Tennessee in Knoxville. His industrial experience includes positions at Michelin Research and Oak Ridge National Laboratory, as well as extensive professional practice in regional design and manufacturing firms. He can often be found with his four children in his home machine shop building steam engines and repairing Jeeps.

: APPLICATION OF RAPID PROTOTYPING FOR ENGINEERING DESIGN PROJECTS

2006-2317: APPLICATION OF RAPID PROTOTYPING FOR ENGINEERING DESIGN PROJECTS Jorge Rodriguez, Western Michigan University Jorge Rodriguez is an Associate Professor in the Department of Industrial and Manufacturing