Hands On Workshop Based Learning Of Rapid Prototyping

Although the manufacturing industry has recently declined considerably, several new manufacturing methods are growing in the 21 st century. One of these methods is Rapid Prototyping (RP). Through the past decade, RP technology has increasingly been implemented in many places, (i.e. dentistry, biology, casting, tooling, and robotics). Although this technology has been advancing swiftly in teaching, training, and learning, it is still in its infancy. Since this vital technology is very important for the progression of the manufacturing industry, an NSF grant has been awarded for the RP Education (DUE Award Number 0302314: Technician Education in RP and Virtual Manufacturing Technologies). Project team members organized a workshop on Training the RP trainers at San Diego City College from July 27 to August 1, 2003. Tennessee Tech University (TTU) faculty and assistants attended this workshop because TTU was in the process of building a RP Lab and organizing workshops for high school students/instructors. This paper intends to report learning practices, adaptations, and implementations accomplished via this workshop. The State of the Art The mission for all instructors is to educate their students the best way possible. Their teaching techniques should challenge, educate, and promote the students' innovative thinking 1 . The lecture-based format of teaching, which predominates in engineering education, may not be best to achieve these technical learning goals 2 . Through the lecture method, an instructor introduces students to course work by producing notes on a chalkboard or overhead projector. The instructor then hopes that students can regurgitate this collected information on their homework or exams. Some classes, if students are lucky, have accompanied laboratory practices where they can gain hands-on experience. There have been several attempts to revise engineering curriculum to improve understanding and foster creative thinking 3 . RP laboratories and practices may bridge lecture based education and laboratory execution in design and manufacturing courses, and then increase students’ comprehension. “Proceedings of the 2004 American Society for Engineering Education Conference & Exposition Copyright©2004, American Society for Engineering Education” P ge 959.1 In July 1999, TTU’s Technology Access Fund provided a computer laboratory to support many of the software needs for CAD, CAM and CNC practices. Fifteen DELL OptiPlex GX1, Pentium III computers currently run programs such as: AutoCAD, Mechanical Desktop, I-DEAS, Pro/E, MasterCAM, and CNCez. In December 2002, this computer lab was upgraded to include 22 Pentium IV computers and multimedia teaching capabilities. Although students gain excellent experience with industrial-level CAD/CAM/CNC software tools, compatible advanced manufacturing hardware is limited for producing parts in a real environment. Since the hands-on labs are very important to concrete the CAD/CAM/CNC concepts, lack of adequate CAM and CAD application hardware was the “weak link” in the current enhancement effort. TTU students’ lab practices were limited to conventional and some CNC turning and milling projects. There was no high technology equipment beyond a token handful of CNC machines. Therefore, implementing RP was planned to fill the gap between CAD/CAM and provide TTU students with the opportunity to practice high tech prototyping practices. Finally, TTU received a NSF DUE CCLI A&I Grant, 0311586 to establish the state’s first educational RP Laboratory funded by NSF in Summer 2003 4 . A Generic Overview of RP RP consists of various manufacturing processes by which a solid physical model of a part is made directly from 3D model data, without any special tooling. CAD data may be generated by 3D CAD modelers or model data created by 3D digitizing systems 5 . Charles Hull is given credit with bringing the first commercial RP machine to market in 1987 with SLA-1 6,7 . His machine, like all RP machines, requires 3D CAD data for its operation. To begin the RP process, the 3D CAD data is sliced into its thin (~.005 in.) crosssectional planes by a computer. The cross-sections are sent from the computer to the RP machine, which builds the part layer-by-layer. The first layer’s geometry is defined by the shape of the first cross-sectional plane generated by the computer. It is bonded to a platform or starting base and additional layers are bonded on top of the first, shaped according to their respective cross-sectional planes. This process is repeated until the prototype part is complete. The advantages of RP are clear: development of physical models can be accomplished in significantly less time as compared to the traditional machining process. Some other applications of these technologies include development of molds, patterns for casting, and tooling. The prototype built by RP machines can be put to a number of uses as given in Table 1. Three-dimensional prototypes put students and designers on equal footing in evaluating designs. All the interested parties can see, touch, and handle the design, just as the ultimate customers will. “Proceedings of the 2004 American Society for Engineering Education Conference & Exposition Copyright©2004, American Society for Engineering Education” P ge 959.2 Most students can’t see the design changes or final designs in product form until tooling is produced. New concept-stage RP technologies can provide dozens of snapshot views of the final product at a fraction of the time and cost of RP systems. This lets students watch as the product evolves and lets them take more chances and be more creative as less time, effort, and ego are invested in each model. Table 1: The Advantages of Rapid Prototyping Systems Check the feasibility of new design concepts Visualization Function/fit test and verification Conduct market tests/evaluation Promote concurrent product development Make Rapid tooling Make many exact copies simultaneously Use as a master for metal mold conversion Manufacturing producibility and supplier quoting Reverse Engineering using RP The various existing RP methods can be categorized by the material they use: photopolymer, thermoplastic, and adhesives. Photopolymer systems start with a liquid resin, which is then solidified by discriminating exposure to a specific wavelength of light. Thermoplastic systems begin with a solid material, which is then melted and fuses upon cooling. The adhesive systems use a binder to connect the primary construction material. The typical processes are Stereolithography, Laminated Object Manufacturing, Selective Laser Sintering, Fused Deposition Modeling, 3D Printing, and Multi Jet Modeling 5 . Rapid Prototyping Technology at TTU Although neither the current TTU curriculum nor any other school in the state of Tennessee had an RP laboratory in which to practice 8 , Middle Tennessee State University, Murfreesboro, TN has recently purchased some rapid prototyping machines for their machine tool technology lab. These machines were planned to be used in industrial projects and senior level capstone courses 9 . At TTU, all the CAD design labs are currently done with AutoCAD2002 in the computer lab, and the CNC production labs cover only Milling and Turning Processes practicing CNCez and MasterCAM. Establishing the RP laboratory and enhancing the current courses with RP help the course instructor to convey the cutting edge technology to current students in CAD, CNC, and CAM courses. Since the initial introduction of the RP process in 1987, several machines have entered the market, which are now affordable by universities. Project team has searched many sources in order to decide which RP machine will be selected. A low cost per prototyped part is important because of the need to prototype a large number of concepts, and to have many student teams use the machine. Speed is important as well. With a class size ranging from 15-20 students and plans to increase the class size to 40 students, a machine that takes one-to-two days to produce a part would limit student access. The use of benign printing materials also would make it safer to let students work with the system. Because of the short time allowed in the course schedules for the projects, and large number of student teams, cost and speed are the two main determinants in the “Proceedings of the 2004 American Society for Engineering Education Conference & Exposition Copyright©2004, American Society for Engineering Education” P ge 959.3 decision to purchase the Z406 machine 10 . The speed of the system allows an entire class of students to print color parts for their projects within a week. Additionally, it is easier to modify parts after they have been printed, just as traditional foam models are reshaped. Safety concerns are negligible with the Z406 machine. After a communal build is completed, students receive the final parts they designed and built. There is also no need to add additional support structure on the CAD part design. This extra work is totally eliminated with the Z406 system. Rapid Prototyping Technologist “Train the Trainer” Workshop The objective the NSF grant, 0302314 is to develop rapid prototyping and timecompression techniques in a “design for manufacturing” program for technicians 11 . Tasks include developing and expanding nine course modules, offering workshops for faculty, providing technical and research experiences for students, and developing laboratory and computer-aided design tools. A strong information technology component includes the sharing of design code and files over the Internet between the laboratories at the institutions. The project also serves community college, university, and high school vocational technical students. Figure 1: RP Technologist “Train the Trainer” workshop announcement As part of this grant, RP Technologist “Train the Trainer” Workshop was held in San Diego City College from July 27 to August 1, 2003. One TTU f