Doorknob

October 2000 Journal of Engineering Education 413

RONALD E. BARRMechanical Engineering DepartmentThe University of Texas at Austin

PHILIP S. SCHMIDTMechanical Engineering DepartmentThe University of Texas at Austin

THOMAS J. KRUEGERMechanical Engineering DepartmentThe University of Texas at Austin

CHU-YUN TWUAdvanced Micro Devices, Austin, Texas

ABSTRACT

This paper discusses a new freshman course that merges previoustopics in the “Introduction to Mechanical Engineering” and “En-gineering Design Graphics” courses into a single integrated teach-ing effort. The main objective of the new course is to introduce stu-dents to mechanical engineering education and practice throughlectures and laboratory experiences. A major effort in the course isdevoted to a reverse engineering team project. The students are di-vided into four-member teams and are instructed to select a simplemechanical assembly for dissection. They study and disassembletheir object into basic constituent components, documenting thisprocess with freehand sketches and notes. They use these sketchesand other measured dimensions to construct 3-D solid computermodels of each major component. The teams then obtain .STLfiles of the solid models, which are used to make rapid physical pro-totypes of their parts. The teams conclude their project activities bygenerating engineering drawings directly from the 3-D geometricdata base. All of these efforts are integrated, documented, and sub-mitted to the instructor as a final team project report.

I. INTRODUCTION

A new freshman course at the University of Texas at Austinmerges previous topics in “Introduction to Mechanical Engineer-ing” and “Engineering Design Graphics” courses. The main objec-tive of this new course is to introduce students to mechanical engi-neering education and practice through lectures and laboratoryexperiences. Lecture topics include orientation to university facili-

ties and services, teamwork skills, introduction to the mechanicaldesign process, and guest speakers from industry. A major effort inthe course is devoted to a reverse engineering team project that in-volves mechanical dissection.1,2 The course also includes concomi-tant laboratory exercises in engineering design and graphics.3

The course is taught using both a large lecture class and smallerlaboratory sections. The large lecture class format allows direct ac-cess to approximately 120 students simultaneously for one hour perweek. In this large lecture class, students are oriented to mechanicalengineering education and practice through a series of lectures andassignments. Guest lectures include representatives from the engi-neering library, career placement center, and coop office. In addi-tion, speakers come from industries such as Ford Motor Companyand Proctor and Gamble. Regular class lectures are supported byPowerPoint® slide presentations on various engineering topics, asshown in table 1. The lecture homework exercises are listed intable 2 and include both individual assignments and team exercisesthat support group activities. In an effort to better communicatewith the large number of students in this lecture class, a special In-ternet web-site has been developed for the course and is located atthe following URL: http://www.me.utexas.edu/~me302/.

The smaller laboratory sections of 24 students meet in computergraphics labs for approximately four hours per week. In these small-er sections, they matriculate through a series of typical engineeringdesign graphics exercises.4 These include freehand sketching of pic-torial and orthographic views, sectioning, dimensioning practices,and 3-D computer modeling. They also are exposed to graphics ap-plications such as mass properties and rapid prototyping. The cur-rent software used for computer modeling is AutoCAD-14, andthe hardware system used for rapid prototyping is JP System-5.

II. INTEGRATED REVERSE ENGINEERING PROJECT

A major effort in the course is devoted to a reverse engineeringteam project. The students are divided into four-member teamsbased on the results of a Myers-Briggs Type Indicator (MBTI) sur-vey and a team questionnaire (homework assignment #3). This isdone in an effort to foster healthy team dynamics for the project.Team members are also chosen based on their common enrollmentin the graphics laboratory sections. The teams are instructed to selecta 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 areverse engineering project proposal (homework assignment #4).This proposal includes a cover page, a general written description of

An Introduction to Engineering Throughan Integrated Reverse Engineeringand Design Graphics Project

the object, and a graphic picture. Selection of this object tends to becrucial for the success of the team, and instructor approval is war-ranted before the object is accepted. Typical objects selected arelisted in table 3. The team project involving a door knob (figure 1)has been selected for illustration in this paper.

A. Project PlanningAfter the object has been approved by the instructor, the teams

meet and plan their dissection project activities through exercisesinvolving charts and graphs (homework assignment #5). They or-ganize their entire semester schedule, week-by-week, using aGantt chart (figure 2). An initial engineering study of the object isconducted and they establish its major input-output functionusing a black-box diagram (figure 3). This allows the team tostudy the functionality of the device before the dissection processis initiated.

B. Mechanical DissectionThe team disassembles the mechanical object to study sub-as-

semblies and individual components. In order to help them orga-nize the dissection process, a fishbone diagram (figure 4) is used toshow relationships of these sub-assemblies and components. This

414 Journal of Engineering Education October 2000

Table 1. Weekly topics for the large lecture class.

Table 2. Homework exercises for lecture class.

Figure 1. Graphic picture of the door knob assembly used for dis-section. This object must first be approved by the instructor.

Figure 2. The team plans their reverse engineering projectusing a Gantt chart. This chart serves as a week-to-week planner.

Table 3. Objects selected for reverse engineering.

forces the students to study each individual component’s function-ality, and to name each part appropriately. They work in teams tomeasure the geometry of each major component. This informationis later used for building computer models of the parts.

C. Sketching Assemblies and ComponentsIn order to aid in visualizing the dissection process, the students

make isometric sketches of the whole assembly (figure 5) and of keyindividual components (figure 6). These sketches are submitted asteam homework assignment #6 so that the instructor can commenton their quality, and so that the students can improve them for thefinal report. The sketches also prove useful as visual aids when thestudents start to build the 3-D computer models.

D. Computer Modeling and AnalysisThe next phase in the reverse engineering project is to build 3-

D computer models of the key components of the assembly. Rely-ing on the sketches and measured dimensions for each compo-nent, the students build 3-D computer models using the availablecommands in the software (in this case AutoCAD-14). When fin-ished, the computer models can be visualized on the screenthrough the rendering capabilities of the software (figure 7). Stu-dents also prepare color hard copies of the images to submit ashomework assignment #7.


Figure 5. Freehand sketch of the assembly provides a visualiza-tion aid during dissection.

Figure 6. Sketch of an individual component.

Figure 7. Rendered image of a door knob component: Knob andshaft.

Figure 3. Black-box diagram showing the major input-outputrelationships for the door knob assembly.

Figure 4. Fishbone diagram is used to illustrate sub-compo-nents and assembly relationships in mechanical dissection.


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

E. Rapid PrototypingAnother application of the computer model data base is rapid

prototyping. The students generate an .STL file directly from thedigital geometric data base, and the .STL file is transferred to arapid prototyping system (in this case the JP System 5 from SchroffDevelopment Corp.). The rapid prototyping system slices the geo-metric solid into many thin layers, and each layer outline is cut onadhesive paper using a digital plotter equipped with a sharp blade.The thin slices are assembled together manually on a registrationboard by the students. The product is a 3-D physical prototype ofthe component, which can then be finished with a glue or paintcovering. The whole process takes the student team about 3 hoursper component. In this case, mating components were producedusing the system (figure 9).

F. Documentation and Final ReportThe final graphics documentation is in the form of engineering

drawings. The drawings are projected directly from the 3-D geo-metric solid model using available functions in AutoCAD-14. Thedrawing is then completed using dimensions and annotations (fig-ure 10). In this manner, the students generate drawings for eachmajor component in the assembly. They also include a completedparts list of all the parts (figure 11) of the assembly. The parts listincludes determination of the part’s material, which is also the sub-ject of the final lecture homework assignment #8.

The last activity in the team project is the generation of a finalreport. All of the written and graphics materials are assembled inproper order and bound together. This includes a final section onproduct re-design, in which the team discusses ways to improve thedesign of the object. The project is submitted to the instructor for a

Figure 11. Parts list for the door knob assembly, including iden-tification of part material.

Figure 9. Prototypes of the door knob parts.

Figure 10. Drawings are projected directly from the 3-D solidmodel, and are completed with dimensions and annotations.Figure 8. Mass properties report of casing.

final team grade. To facilitate this process, a project grading sheethas been prepared which lists all obligatory components for the re-port and the point value for each (see figure 12). Also included isthe opportunity to distribute each team member’s contribution tothe project as a percent of the total effort.

III. CONCLUSIONS AND RECOMMENDATIONS

This integrated reverse engineering and design graphics projecthas now been conducted for four semesters. It has been found tostimulate the students’ interests in Mechanical Engineering by giv-ing them hands-on activities that apply engineering principles withsignificant visual feedback. Specific observations about the successof this project in accomplishing class goals include the followingcomments

1. Reverse engineering and team projects are effective meansfor introducing freshmen to the engineering discipline.The related activities mesh well with topics pertinent to en-gineering education and practice. It is not necessary to havea strong background in mathematics or physics to under-stand the various engineering phases of the product designcycle.

2. The students learn about team dynamics and about the im-portance of inter-personal communication skills. They select

a team leader and learn about the responsibilities of individ-ual team members. They also must make judgements on thepercent contribution each team member makes to the overallproject effort.

3. They gain hands-on experience with various mechanicalcomponents during the dissection exercise. Most of the ob-jects operate according to mechanical energy principles, andthe students become familiar with these principles when de-termining the functionality of the device.

4. The students are able to relate what they learn in the graphicslaboratory with a real-life engineering problem. The variousgraphical exercises associated with the project offer strong vi-sual communication modalities for the reverse engineeringprocess.

5. The students witness, first-hand, the various modernapplications of the 3-D geometric data base. They seethe 3-D digital data base being directly used for massproperties analysis, rapid prototyping, and design draw-ing documentation. In this manner, they gain an appre-ciation for the near-future concurrent engineering de-sign paradigm.

6. The teams work together to assemble and submit a finalteam project report that constitutes a significant portion oftheir course grade. In this manner, they learn valuable writ-ten, oral, and graphical communication skills which are re-quired for the new ABET 2000 criteria.

While this reverse engineering design project has been quite suc-cessful during its two years, improvements can still be made. Theusual objective of reverse engineering is to improve the productthrough a re-design process. That objective is not currently fulfilled,since the students merely deal with and mimic the current geometryof the object in all their graphics work. It would be helpful to movethe re-design phase of the project earlier in the semester and havethe students incorporate improved geometry into their graphicswork.

A second problem is the selection of objects for the reverse en-gineering project. Some of the objects selected (see table 3), suchas toy guns and airplanes, proved to be difficult to model and pro-totype because of the sculpted surfaces incasing the inner me-chanical workings. On the other hand, objects like the door knobassembly and can opener turned out to be quite amenable to thisapplication.

In conclusion, the integrated reverse engineering and designgraphics project proved an effective way to orient freshmen stu-dents to the field of Mechanical Engineering. It allowed them towork in teams, to hone inter-personal skills, and to get to knowtheir freshmen peers better. It also demonstrated an integratedprocess that relies heavily on a central computer data base for prod-uct design. In this manner, they have gained a glimpse of the futureof engineering design in practice.

ACKNOWLEDGEMENTS

The door knob examples were taken from the project report byteam 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 Devel-opment grant from the UT College of Engineering.


Figure 12. Evaluation form used to grade the final team pro-ject.

REFERENCES

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

2. Mickelson, S.K., R.D. Jenison, and N. Swanson, “Teaching Engi-neering Design through Product Dissection,” Proceedings, 1995 ASEE An-nual Conference, ASEE, 1995.

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

4. Barr, R., et al., “The Freshman Engineering Design GraphicsCourse at the University of Texas at Austin,” Journal for Geometry andGraphics, vol. 2, no. 2, 1998, pp. 169–179.


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Doorknob