Session TA1-1 Introduction to Mechanical Engineering Design through a Reverse Engineering Team Project Ronald Barr, Thomas Krueger, Billy Wood, Ted Aanstoos, Mostafa Pirnia Mechanical Engineering Department University of Texas at Austin Abstract Our group at the University of Texas at Austin has the responsibility for teaching the first course in Mechanical Engineering. The first-year course ME 302, titled “Introduction to Engineering Design and Graphics,” was derived from a traditional Engineering Graphics course with added material that focuses on the engineering design process. The graphics component is based on a computer modeling educational paradigm that includes 2-D computer sketching, 3-D solid modeling of parts, assembly modeling, and the projection of an engineering drawing directly from the 3-D model. Other applications of the paradigm include kinematics animation, finite element analysis, and generation of a rapid prototype directly from the 3-D data base. In order to motivate the freshmen students in the area of engineering design, we have instituted a team project based on the concept of reverse engineering. Reverse engineering is the dissection of a common mechanical assembly into its individual parts, and then studying the geometry and design function of each part. The team activities in the reverse engineering project have been carefully scheduled by our group so that the teams systematically accomplish various phases of the project over the duration of the course, with intermediate due dates for major tasks. The student teams select a mechanical assembly, dissect it into individual parts, make measurements and sketches, build 3-D solid models, apply the solid models to various analyses, and make rapid prototypes. The whole project is eventually documented with sketches, 3-D model printouts, design analysis reports, prototypes, and final drawings. Introduction to Modern Engineering Graphics Instruction Within the past two decades, the teaching of 3-D solid modeling has become the central theme in most engineering graphics programs. This recent paradigm shift to 3-D has been facilitated by the development and low-cost availability of solid modeling software that allows the student to focus on the “bigger-picture” approach to engineering graphical communication. In this Concurrent Engineering approach1, the 3-D geometric database serves as the hub for all engineering communication activities (Figure 1). These communications include engineering analysis, simulation, assembly modeling, prototyping, and final drafting and documentation. Table 1. The Triad of Modern Engineering Graphics Instruction Proceedings of the 2009 ASEE Gulf-Southwest Annual Conference Baylor University Copyright © 2009, American Society for Engineering Education In the Concurrent Engineering paradigm for A. Engineering Graphics Fundamentals graphical communication, the student starts Freehand Sketching with a sketch of an idea. The sketch can then be used to build a solid model of the part. The Generation of Engineering Drawings solid model not only serves as a visualization Dimensioning modality, but it also contains the solid Sectioning geometry data needed for engineering analysis. Typical of these analyses are finite element B. Computer Graphics Modeling Fundamentals meshing, stress and thermal studies, mass Creation of 2-D Computer Geometry properties reports, and clearance-interference Creation of 3-D Computer Models checking. After analysis, the same geometric Building Computer Assembly Models database can be used to generate final communications like engineering drawings, C. Computer Graphics Applications marketing brochures, and even rapid physical Digital Analysis prototypes that can be held in one’s hand. Animation and Simulation Presentations Indeed, an entire Engineering Graphics curriculum could be developed around three Rapid Prototyping and Manufacturing major aspects of instruction: engineering Design Projects/Reverse Engineering graphics fundamentals, computer graphics Presentation Graphics modeling fundamentals, and computer graphics applications. This triad of modern engineering graphics instruction is listed in Table 1. Figure 1. The Concurrent Engineering Design Paradigm. What Is Reverse Engineering? Proceedings of the 2009 ASEE Gulf-Southwest Annual Conference Baylor University Copyright © 2009, American Society for Engineering Education Reverse engineering is a systematic methodology for analyzing the design of an existing device or system. It can be used as a means to study the design, and is a prerequisite for re-designing the device or system. Reverse engineering is used to gain information about the functionality and sizes of existing design components. It should be noted that, for student projects, reverse engineering is a legitimate activity. Determining “how something works” is not stealing someone’s ideas, but rather is a beneficial way to enhance the learning process of engineering design for the novice. Reverse engineering is sometimes called mechanical dissection because it involves taking apart or “dissecting” a mechanical system. Mechanical dissection has been promoted for many years as an acceptable activity for engineering students2,3,4. When the student dissects the system, careful sketches of the parts are made. These sketches convey the geometry of the part, and show how the parts fit and work together. This facilitates reassembling of the whole system at a later date. The student needs to carefully measure all of the features on each part during the dissection process so that solid models can be created. Since correct measurements are a significant part of the reverse engineering process, the students learn to use common measurement tools such as scales and calipers. Student Reverse Engineering Project The reverse engineering project serves as a semester-long, culminating experience for engineering graphics students at the University of Texas at Austin. Typically, these students are freshmen engineers who have very little background in design or analysis. Hence, the reverse engineering project does not serve as a rigorous analytical challenge, but rather allows them to apply all the tools that they have learned in the graphics course to a real-world design problem. The checklist outlines all the activities expected for the student reverse engineering team project. The following sections detail the chronological events that occur during this reverse engineering project. Assigning Teams At the start of the semester, the students are asked to fill out a form that includes information like section number, class level, gender, dormitory name, and other scheduling data. They are also required to take the Myers-Briggs Type Indicator (MBTI) on-line, and then to indicate their four- letter MBTI personality rating on the information form. These data are then used by the instructor and teaching assistant (TA) to assign the teams (nominally four students per team) in an equitable fashion that balances team factors such as gender, academic backgrounds, and MBTI types. The team will then have an inaugural meeting in class to exchange contact information, to pick a team leader, and to then begin the project. Selecting the Engineering Object to be Reverse Engineered The first team task is to pick the engineering object to be reversed engineered. Some judgment is needed to select an object that matches the task at hand. Usually, the instructor will give some advice on what types of objects work well. Table 2 lists some engineering objects that have been successfully used in the past for this reverse engineering team project. For purpose of illustrating the reverse engineering project, a Trailer Winch student report has been selected for this paper. Table 2. Examples of Acceptable Reverse Engineering Objects Proceedings of the 2009 ASEE Gulf-Southwest Annual Conference Baylor University Copyright © 2009, American Society for Engineering Education Baby Toy Differential Gear Master Cylinder Shower Massage Head Bathroom Scale Doorknob Assembly Model Car Drive Train Spinning Disk Launcher Beer Faucet Flashlight Oil Pump Sprinkler Head Bicycle Pump Fuel Pump Oscillating Sprinkler Stapler Bolt Cutter Gate Valve Pencil Sharpener Toy Gun Can Opener Hand Tool Pepper Grinder Trailer Hitch Corkscrew Hose Nozzle Piston Assembly Trailer Winch Deadbolt Lock Kitchen Timer Pipe Clamp Vise Grip Desktop Clamp Lug Wrench Ratchet Tie-Down Water Faucet Valve Charts and Diagrams As part of the process to get started, the team selects a product for the reverse engineering project and then submits a proposal for approval of that product. The students learn within the same week whether their proposal was approved. The students have to quickly plan how to utilize the remainder of the semester, efficiently, to complete the project. To do this, students prepare a Gantt chart for the team to follow. The students review the team activities that are to be completed during the semester. Some of the assignments have multiple activities. The due dates specified in the course syllabus are the deadlines for completion of each activity. Figure 2 shows the Gantt chart that is used for the Trailer Winch design. Students are encouraged to schedule team meetings for the entire semester in the Gantt chart, and to transfer the meetings to the daily planner of each team member The initial step in the reverse engineering of a product is to analyze the product in terms of inputs and outputs. The exact analytical operation that converts an input into an