An introduction to engineering through an integrated reverse engineering and design graphics project

An introduction to engineering through an integrated reverse engineering and design graphics project

Barr, Ronald E

ABSTRACT

This paper discusses a new freshman course that merges previous topics in the “Introduction to Mechanical Engineering” and “Engineering Design Graphics” courses into a single integrated teaching effort. The main objective of the new course is to introduce students to mechanical engineering education and practice through lectures and laboratory experiences. A major effort in the course is devoted to a reverse engineering team project. The students are divided into four-member teams and are instructed to select a simple mechanical assembly for dissection. They study and disassemble their object into basic constituent components, documenting this process with freehand sketches and notes. They use these sketches and other measured dimensions to construct 3-D solid computer models of each major component. The teams then obtain .STL files of the solid models, which are used to make rapid physical prototypes of their parts. The teams conclude their project activities by generating engineering drawings directly from the 3-D geometric data base. All of these efforts are integrated, documented, and submitted to the instructor as a final team project report.

I. INTRODUCTION

A new freshman course at the University of Texas at Austin merges previous topics in “Introduction to Mechanical Engineering” and “Engineering Design Graphics” courses. The main objective of this new course is to introduce students to mechanical engineering education and practice through lectures and laboratory experiences. Lecture topics include orientation to university facilities and services, teamwork skills, introduction to the mechanical design process, and guest speakers from industry. A major effort in the course is devoted to a reverse engineering team project that involves mechanical dissection.’, The course also includes concomitant laboratory exercises in engineering design and graphics.’

The course is taught using both a large lecture class and smaller laboratory sections. The large lecture class format allows direct access to approximately 120 students simultaneously for one hour per week. In this large lecture class, students are oriented to mechanical engineering education and practice through a series of lectures and assignments. Guest lectures include representatives from the engineering library, career placement center, and coop office. In addition, speakers come from industries such as Ford Motor Company and Proctor and Gamble. Regular class lectures are supported by PowerPoint slide presentations on various engineering topics, as shown in table 1. The lecture homework exercises are listed in table 2 and include both individual assignments and team exercises that support group activities. In an effort to better communicate with the large number of students in this lecture class, a special Internet web-site has been developed for the course and is located at the following URL: http://www.me.utexas.edu/-me302/.

The smaller laboratory sections of 24 students meet in computer graphics labs for approximately four hours per week. In these smaller sections, they matriculate through a series of typical engineering design graphics exercises. These include freehand sketching of pictorial and orthographic views, sectioning, dimensioning practices, and 3-D computer modeling. They also are exposed to graphics applications such as mass properties and rapid prototyping. The current software used for computer modeling is AutoCAD-14, and the hardware system used for rapid prototyping is JP System-5.

11. INTEGRATED REvERSE ENGINEERING PROJECT

A major effort in the course is devoted to a reverse engineering team project. The students are divided into four-member teams based on the results of a Myers-Briggs Type Indicator (MBTI) survey and a team questionnaire (homework assignment #3). This is done in an effort to foster healthy team dynamics for the project. Team members are also chosen based on their common enrollment in the graphics laboratory sections. The teams are instructed to select a simple mechanical assembly, such as a door knob, pencil sharpener, or toy gun, which will be used for the mechanical dissection process.

The team members submit their selected object in the form of a reverse engineering project proposal (homework assignment #4). This proposal includes a cover page, a general written description of the object, and a graphic picture. Selection of this object tends to be crucial for the success of the team, and instructor approval is warranted before the object is accepted. Typical objects selected are listed in table 3. The team project involving a door knob (figure 1) has been selected for illustration in this paper.

-4. Project Planning

After the object has been approved by the instructor, the teams meet and plan their dissection project activities through exercises involving charts and graphs (homework assignment #5). They organize their entire semester schedule, week-by-week, using a Gantt chart (figure 2). An initial engineering study of the object is conducted and they establish its major input-output function using a black-box diagram (figure 3). This allows the team to study the functionality of the device before the dissection process is initiated.

B. Mechanical Dissection

The team disassembles the mechanical object to study sub-assemblies and individual components. In order to help them organize the dissection process, a fishbone diagram (figure 4) is used to show relationships of these sub-assemblies and components. This forces the students to study each individual component’s functionality, and to name each part appropriately. They work in teams to measure the geometry of each major component. This information is later used for building computer models of the parts.

C. Sketcbing Assemblies and Components

In order to aid in visualizing the dissection process, the students make isometric sketches of the whole assembly (figure 5) and of key individual components (figure 6). These sketches are submitted as team homework assignment #6 so that the instructor can comment on their quality, and so that the students can improve them for the final report. The sketches also prove useful as visual aids when the students start to build the 3-D computer models.

D. Computer Modeling and Analysis

The next phase in the reverse engineering project is to build 3D computer models of the key components of the assembly. Relying on the sketches and measured dimensions for each component, the students build 3-D computer models using the available commands in the software (in this case AutoCAD-14). When finished, the computer models can be visualized on the screen through the rendering capabilities of the software (figure 7). Students also prepare color hard copies of the images to submit as homework assignment #7.

Once the 3-D computer model is built, its digital data base is available for other applications. One of these applications is mass properties analysis. The software used for this project has a built-in mass properties report function. The students load the model and then perform the analysis, which generates a mass properties report file (.MPR) that can be printed out, as shown in figure 8.

E. Rapid Prototyping

Another application of the computer model data base is rapid prototyping. The students generate an .STL file directly from the digital geometric data base, and the .STL file is transferred to a rapid prototyping system (in this case the JP System 5 from Schroff Development Corp.). The rapid prototyping system slices the geometric solid into many thin layers, and each layer outline is cut on adhesive paper using a digital plotter equipped with a sharp blade. The thin slices are assembled together manually on a registration board by the students. The product is a 3-D physical prototype of the component, which can then be finished with a glue or paint covering. The whole process takes the student team about 3 hours per component. In this case, mating components were produced using the system (figure 9).

F. Documentation and Final Report

The final graphics documentation is in the form of engineering drawings. The drawings are projected directly from the 3-D geometric solid model using available functions in AutoCAD-14. The drawing is then completed using dimensions and annotations (figure 10). In this manner, the students generate drawings for each major component in the assembly. They also include a completed parts list of all the parts (figure 11) of the assembly. The parts list includes determination of the part’s material, which is also the subject of the final lecture homework assignment #8.

The last activity in the team project is the generation of a final report. All of the written and graphics materials are assembled in proper order and bound together. This includes a final section on product re-design, in which the team discusses ways to improve the design of the object. The project is submitted to the instructor for a final team grade. To facilitate this process, a project grading sheet has been prepared which lists all obligatory components for the report and the point value for each (see figure 12). Also included is the opportunity to distribute each team member’s contribution to the project as a percent of the total effort.

III. CONCLUSIONS AND REcommENDATioNs

This integrated reverse engineering and design graphics project has now been conducted for four semesters. It has been found to stimulate the students’ interests in Mechanical Engineering by giving them hands-on activities that apply engineering principles with significant visual feedback. Specific observations about the success of this project in accomplishing class goals include the following comments

1. Reverse engineering and team projects are effective means for introducing freshmen to the engineering discipline. The related activities mesh well with topics pertinent to engineering education and practice. It is not necessary to have a strong background in mathematics or physics to understand the various engineering phases of the product design cycle.

2. The students learn about team dynamics and about the importance of inter-personal communication skills. They select a team leader and learn about the responsibilities of individual team members. They also must make judgements on the percent contribution each team member makes to the overall project effort.

3. They gain hands-on experience with various mechanical components during the dissection exercise. Most of the objects operate according to mechanical energy principles, and the students become familiar with these principles when determining the functionality of the device.

4. The students are able to relate what they learn in the graphics laboratory with a real-life engineering problem. The various graphical exercises associated with the project offer strong visual communication modalities for the reverse engineering process.

5. The students witness, first-hand, the various modern applications of the 3-D geometric data base. They see the 3-D digital data base being directly used for mass properties analysis, rapid prototyping, and design drawing documentation. In this manner, they gain an appreciation for the near-future concurrent engineering design paradigm.

6. The teams work together to assemble and submit a final team project report that constitutes a significant portion of their course grade. In this manner, they learn valuable written, oral, and graphical communication skills which are required for the new ABET 2000 criteria.

While this reverse engineering design project has been quite successful during its two years, improvements can still be made. The usual objective of reverse engineering is to improve the product through a re-design process. That objective is not currently fi,lfil_led, since the students merely deal with and mimic the current geometry of the object in all their graphics work It would be helpful to move the re-design phase of the project earlier in the semester and have the students incorporate improved geometry into their graphics work.

A second problem is the selection of objects for the reverse engineering project. Some of the objects selected (see table 3), such as toy guns and airplanes, proved to be difficult to model and prototype because of the sculpted surfaces incasing the inner mechanical workings. On the other hand, objects like the door knob assembly and can opener turned out to be quite amenable to this application.

In conclusion, the integrated reverse engineering and design graphics project proved an effective way to orient freshmen students to the field of Mechanical Engineering. It allowed them to work in teams, to hone inter-personal skills, and to get to know their freshmen peers better. It also demonstrated an integrated process that relies heavily on a central computer data base for product design. In this manner, they have gained a glimpse of the future of engineering design in practice.

AcKNOWLEDGEMENTS

The door knob examples were taken from the project report by team members Terry Grumbles, Edgar Castro, Michael Daywood, and Tony Rogers. The class web page design http://www.me. utexas.edu/-me302/ was supported in part by an Academic Development grant from the UT College of Engineering.

REFERENCES

1. Sheppard, S.D., “Dissection as a Learning Tool,” Proceedings, 1992 Frontiers in Education Conference, IEEE, 1992.

2. Mickelson, S.K., RD. Jenison, and N. Swanson, “Teaching Engineering Design through Product Dissection,” Proceedings, 1995ASEE Annual Conference, ASEE, 1995.

3. Barr, R., and D. Juricic, “Classroom Experiences in an Engineering Design Graphics Course with a CAD/CAM Extension,” Engineering Design Graphicsjournal, vol. 62, no. 1, 1997, pp. 9-21.

4. Barr, R., et al., “The Freshman Engineering Design Graphics Course at the University of Texas at Austin,” Journal/for Geometry and Graphics, vol. 2, no. 2,1998, pp. 169-179.

RONALD E. BARR

Mechanical Engineering Department

The University of Texas at Austin

PHILIP S. SCHMIDT

Mechanical Engineering Department

The University of Texas at,Austin

THOMAS J. KRUEGER

Mechanical Engineering Department

The University of Texas at Austin

CHU-YUN Twu

Advanced Micro Devices, Austin, Texas

RONALD E. BARR (CONTACT AUTHOR)

Dr. Ronald E. Barr is Professor of Mechanical and Biomedical Engineering at the University of Texas at Austin, where he has taught since 1978. Barr is active in the American Society for Engineering Education and has served on the ASEE Board of Directors as Chair of Zone 111 (1997-1999) and as Vice-President of Member Affairs (2000-2002). Barr received the AT&T Foundation Award (1990) for Excellence in Engineering Teaching, the ASEE Chester F. Carlson Award (1993) for Innovation in Engineering Education, and the Distinguished Service Award (1999) from the Engineering Design Graphics Division of ASEE. His research interests are in Biosignal Analysis, Biomechanics of Human Movement, and Engineering Computer Graphics.

Address: Mechanical Engineering Department, University of Texas at Austin, Austin, Texas, 78712; telephone: 512-471-3008; fax: 512-471-7683; e-mail: rbarr@mail.utexas.edu.

THOMAS J. KRUEGER

Dr. Thomas J. Krueger is a Teaching Specialist in the Mechanical Engineering Department at the University ofTexas at Austin, where he has taught since 1994. He received his Ph.D. from Texas A&M University in 1975, and has taught previously at TAMU, Brazosport College, and Southwest Texas State University. He is a member of ASEE and SME. His interests are in the areas of Engineering Design Graphics curriculum development, Solid Geometric Modeling, Rapid Prototyping, and Engineering Computer Graphics.

Address: Mechanical Engineering Department, University of Texas at Austin, Austin, Texas, 78712; telephone: 512-471-3014; fax: 512-471-7683; e-mail: tkrueger@mail.utexas.edu.

PHILIP S. SCHMIDT

Dr. Philip S. Schmidt is the Donald J. Douglass Centennial Professor of Engineering and University Distinguished Teaching Professor at the University of Texas at Austin, where he has taught since 1970. He has been a member of ASEE and ASME for over 30 years. Schmidt has received a number of teaching honors, including the 1993 Ralph Coates Roe Award from ASEE’s Mechanical Engineering Division. In 1994 he was named as one of the 50 U.S. Professors of the Year by the Carnegie Foundation for the Advancement of Teaching and the following year was named as one of the inaugural members of the Academy of Distinguished Teachers at UT Austin. His research interests include microwave and radio frequency heating processes, thermal process design and industrial ecology.

Address: Mechanical Engineering Department, University of Texas at Austin, Austin, Texas, 78712; telephone: 512-471-3118; fax: 512-471-8727; e-mail: pschmidt@mail.utexas.edu.

Car-YNTwu

Chu-Yun Twu is currently an Engineer at Advanced Micro Devices in Austin, Texas. She received her BS from National Taiwan University in 1997 and her M.S. from the University of Texas at Austin in 1999. She served as a Teaching Assistant and web page designer for ME302 “Introduction to Engineering Design and Graphics” while at the University of Texas. Her research interests are in solid state devices.

Address: Advanced Micro Devices, 5204 E. Ben White Blvd. MS 540, Austin, Texas, 78741; telephone: 512-602-9967; fax: 512-602-6888; e-mail: chuyun.twu@amd.com.

Copyright American Society for Engineering Education Oct 2000

Provided by ProQuest Information and Learning Company. All rights Reserved