Industry-Sponsored Design Projects for Freshmen Engineering Graphics Students

Transcription

1 Industry-Sponsored Design Projects for Freshmen Engineering Graphics Students Ronald E. Barr, Thomas J. Krueger, Ted A. Aanstoos University of Texas at Austin Austin, Texas John Horan Applied Materials Austin, Texas Jeremy Moore Ford Motor Company Dearborn, Michigan ABSTRACT - The freshman Engineering Design and Graphics course is an integral part of curriculum reform efforts throughout the Mechanical Engineering Department at the University of Texas At Austin. Called PROCEED, for Project-Centered Education, this curriculum reform is an attempt to bring industrialsponsored projects into the classroom that will add some relevance to the learning experience. This paper presents some preliminary results in implementing these PROCEED objectives in the freshman graphics course using a Robotic Blade Assembly supplied by Applied Materials and a Piston Assembly supplied by Ford Motor Company. I. INTRODUCTION TO THE COURSE The freshman Engineering Design and Graphics course at the University of Texas at Austin continues to evolve from its inception many decades ago. It has gone from a manual, board-drafting course to a short era of electronic drafting using Computer-Aided Design and Drafting (CADD) systems. During the last ten years, the emphasis has focused on implementing a 3-D solid modeling paradigm as the pedagogical basis for the course [1]. This recent era also slowly unveiled the important applications of the 3-D model to engineering analysis, simulation, manufacturing, and downstream documentation. This latest design paradigm is now being realized and promoted by members of the engineering graphics education community [2]-[6]. The current step in the evolution of the Engineering Design and Graphics course is to employ the latest generation of 3-D modeling software, namely the feature-based SolidWorks modeling software, and to extend this 3-D model to several engineering applications that would excite the freshmen students. Hence, the current goals of the course mesh well with the goals of PROCEED. II. PROJECT-CENTERED EDUCATION An engineering student project is an exercise that usually requires integrating several tasks to achieve a defined goal. It can be an individual project or a team project, or even some form of both. The Mechanical Engineering Department at the University of Texas at Austin has embarked on systemic educational reform throughout the ME curriculum. Called PROCEED, for Project-Centered Education, this curriculum reform is an attempt to bring real-world projects into the classroom that underscore the need to learn fundamental principles while adding excitement and relevance to the learning

2 experience. One important aspect of PROCEED is garnering support from industrial partners who supply project ideas and personnel for the student projects. Two companies, Ford Motor Company and Applied Materials, have already joined the PROCEED effort at the University of Texas. In the freshman Engineering Design and Graphics course, the project consists of a team of four students who reverse engineer a mechanical assembly, such as those illustrated in this paper. They study the individual parts, make sketches and computer models, perform various analyses, and make rapid prototypes of their assembly. At the conclusion of this integrated graphics and design project, the team assembles a final written report. III. THE GRAPHICS LEARNING MODULES To facilitate this project-centered approach, the freshman Engineering Design and Graphics curriculum has been organized into learning modules with specific educational outcomes. Table 1 lists the current modularization scheme and computer graphics learning activities for the course. It consists of ten units that can serve as individual student projects, plus an integrated team project that is conducted throughout the semester. In this way, the individual units train students to develop computer skills and educational outcomes that can also be used on the larger, semester-long team project. These modern course objectives, as outlined in Table 1, are still in the preliminary stage. Several modules were developed and tested in the Spring and Summer 2002 semesters with selected student sections to see how the ideas work in the classroom. Four class sections, with a total of about 70 students, participated in studies of some proposed modules. The rest of this paper describes these trial modules and presents some brief results of student opinions of the material. Table 1 Ten Computer Graphics Learning Modules for Engineering Design and Graphics. Module Computer Graphics Learning Activities 1 2-D Computer Sketching I 2 2-D Computer Sketching II 3 3-D Solid Modeling of Parts I 4 3-D Solid Modeling of Parts II 5 Assembly Modeling and Mating 6 Analysis and Design Modification I 7 Analysis and Design Modification II 8 Kinematics Animation and Rapid Prototyping 9 Section Views in 3-D and 2-D 10 Generating and Dimensioning Three-View Drawings IV. THE INDUSTRIAL SPONSORS Two industrial sponsors supplied mechanical assemblies for student projects. Ford Motor Company of Dearborn, Michigan, supplied a piston assembly. Applied Materials of Austin, Texas, supplied a robotic blade assembly. In this latter case, the project was presented to the freshmen graphics students by an inclass presentation by their representative (see Figure 1). Figure 1. Applied Materials Representative Presenting the Project to the Freshmen Graphics Students During the Summer Session.

3 V. THE ANALYSIS MODULE The analysis module starts with the building of a solid model, such as a piston head. In SolidWorks, the natural way to start a solid model is with a 2-D profile sketch, which can then be revolved around an axis to create a base part. The base part is next edited into the final solid model part. The students can assign a material (or density) to the part and then perform some engineering analyses of the model, such as mass properties or finite element analysis (FEA). For this trial module, the students performed an FEA study. SolidWorks and their gold partner software COSMOS are quite amendable for student learning and usage when performing an FEA study. Once the steps had been outlined for them in a simple handout, the students accomplished this FEA study in less than one hour. After loading COSMOS inside the SolidWorks shell, the students declare a static study (e.g. Study1) and assign a material property to the piston head (e.g. aluminum alloy). They apply restraints and loads on the model. A radial restraint is applied around the cylindrical wall of the piston to disallow circumferential displacement. Similarly, a restraint is applied to the wrist pin holes to have a zero axial displacement. Finally, a uniform force (pressure) is applied to the top face of the piston to simulate gas combustion, and vertical reaction forces are applied inside the wrist pin holes. In order to execute the finite element analysis processing, a mesh must first be created. This is done easily in COSMOS with the Mesh command using a medium grid resolution (Figure 2). Next, the students perform the analysis by displaying the maximum von Mises stress directly on the solid model, as shown in Figure 3. The side bar on the display shows the range of values (colors) for the von Mises stress, and this facilitates the student s ability to identify where the stresses are concentrated. Figure 2. A Mesh is Generated Over the Solid Model for the FEA Study. Figure 3. Results of the FEA Study Show the Von Mises Stress Distribution Over the Solid Model. By allowing the students to rotate the piston head in 3-D space, they are able to see the underside of the piston and notice that the stresses concentrate around the bosses associated with the wrist pin holes. They are also able to print out a color hardcopy of their FEA results for submission to the instructor. As part of the testing of this module, Pre- and Post- FEA surveys were administered to the students. The survey asked three simple questions about their understanding of: 1. 3-D Solid Modeling. 2. Engineering Analysis. 3. Finite Element Analysis (FEA).

4 The response scale was from 5 (exceptional understanding) to 1 (no understanding at all). The results of these Pre- and Post-FEA surveys are shown in Figure 4. As can be seen, the ratings for all three questions went up from the pre- to post-exercise period. The ranking for Solid Modeling went from 3.38 (pre) to 3.85 (post), and the ranking for Do Engineering Analysis went from 3.22 (pre) to 3.86 (post). Most importantly, the rating for the Run FEA Study question went from 2.27 (pre) to 3.55 (post), a large differential which demonstrates that learning outcomes were achieved for this FEA study. In addition to the numerical rating questions, students also had an opportunity to provide open-ended feedback about the modules. Some of the frequent positive comments included the following: Color stress distributions were nice. Seeing loads and stresses was easy. It seemed like a real world application. The visualization was good throughout. Two common criticisms of the module were: More detail/illustrations were needed in notes. Mathematics behind FEA was not explained. This latter comment is particularly challenging, due to the limited mathematical background that most engineering freshmen possess. It is, nonetheless, an issue that must be addressed in the course. VI. THE ASSEMBLY MODELING MODULE Most engineering products are not single parts, but rather are a collection of parts that mate together to perform a desired function. SolidWorks solid modeling software allows not only the creation of individual parts, but also the creation of an assembly of parts. For the two different assemblies supplied by the industrial partners, the students first needed to create the remaining parts. This took about two lab periods. Figure 4. Results of the Student Survey for the Pre- and Post- FEA Study. The first part imported into the assembly file becomes the base part of the assembly and remains immovable during subsequent operations. The subsequent parts are imported and then mated together. In the mating process, a number of constraints were attributed to the mated parts. Some of the geometric constraints used for aligning and mating the parts in the robotic blade assembly included: Parallel mate between the wafer arm and the lower casing (Figure 5). Coincident mates in several places to completely fix the casing to the blade. Concentric mate between the round edge of the lower casing and the outer circular edge of the left wrist (Figure 6). Concentric mates between the left and right wrists, and the two bearing rings. Parallel and Coincident mates to add the upper casing to the assembly. When the assembly modeling and mating exercise is finished, the robotic blade assembly has seven parts: the wafer blade, the lower and upper casings, the left and right wrists, and the two bearing rings. A completed, fully-mated assembly (minus the upper casing to show the bearing rings) is depicted in Figure 7.

5 Figure 6. Applying a Concentric Mate Between the Lower Casing and the Left Wrist. Figure 5. Beginning the Mating Procedure for the Robotic Arm Blade and the Lower Casing. Some of the geometric constraints used for aligning and mating the parts in the piston assembly included: Concentric mate between the piston head boss holes and the wrist pin. Distance mate to position the wrist pin exactly inside the boss holes. Concentric mate between the top hole of the connecting rod and the wrist pin. Concentric mate between the bottom semicircular feature of the connecting rod and its counterpart on the rod cap. Parallel mate between the flat lugs of the connecting rod and the rod cap. Coincident mate between the sides of the connecting rod and the rod cap. When completed, the piston assembly has four completely mated parts: the piston head, the wrist pin, the connecting rod, and the rod cap (see Figure 8). A similar Pre- and Post-Assembly survey was used for this exercise using the same 5-point response scale. The three questions posed were about the students understanding of the three following activities: Figure 7. The Finished Assembly of the Robotic Blade, Minus the Upper Casing. 1. Building Multiple Solid Models 2. Building an Assembly of Solid Model Parts. 3. Mating Solid Model Parts in an Assembly.

6 Figure 9. Results of the Student Survey for the Preand Post- Assembly Modeling Study. Figure 8. The Piston Assembly Model After All the Mating Constraints Are Applied. The results of this survey (Figure 9) again showed that students had a better understanding of the material after the exercise. The Build Parts score went from 3.31 to 4.02, and the Assemble Parts score went from 3.27 to More importantly, their understanding of Mate Parts in an assembly went from a pre-score of 2.98 to a post-score of In addition to the numerical results, some useful comments about the Assembly Modeling and Mating exercise included: Different ways to mate parts were useful. Graphics viewing commands in SolidWorks helped to do the mating. Seems like a real-world practical application. VII. THE KINEMATICS ANIMATION MODULE While assembly models may show how the parts fit together, they are still only static images. With current solid modeling software, it is possible to study dynamic images through kinematics animations. For example, the piston assembly can be animated to show the motion of the piston head as it moves through one complete stroke cycle. That goal proved to be too challenging for the freshmen students in the class, so a simplified kinematics exercise was developed that showed the assembly exploding in a dynamic way. SolidWorks has the ability to create simple animation files when the user is in the Assembly Modeling mode. The students first create an exploded view of the assembly, such as shown in Figures 10 and 11. During this process, the student inputs the direction of the explosion for each part and the distance to explode it. For example, for the piston assembly, the wrist pin was exploded out from the boss holes of the piston head to a distance of about 3 inches. Likewise, the piston head was exploded upwards and the rod cap was exploded downwards from the connecting rod. The connecting rod remained in its current position, although it also could have been positioned somewhere in the assembly model space. Next the path of each exploded part was edited to create a realistic animation in the correct temporal sequence. A time span of 6 seconds was arbitrarily picked for the kinematics animation. The wrist pin was first exploded outward from 0 to 2 seconds. Next the piston head was exploded upward from 2 to 4 seconds of the time span. Finally the rod cap was exploded downward for the final 4 to 6 seconds of the time span.

7 The animation was played on the screen and simultaneously recorded as an.avi file (a nice feature of SolidWorks). The students then saved the.avi file on a diskette to run on an external viewer, like QuickTime or Microsoft Windows Media Player. They then played the.avi file on the screen for the instructor and laboratory teaching assistant to observe. As in the two previous test modules, a Pre-and Post- Kinematics student survey was conducted concerning their understanding of: 1. Exploding a 3-D Assembly Model. 2. Creating a Kinematics Animation. 3. Making an.avi file. The responses to the pre- and post- survey questions are shown in Figure 12 using the same ranking scale as before. It is interesting to note that the ratings on both creating the animation and making the.avi file went from about 1.75 (Pre-) to about 3.75 (Post-exercise), a jump of two whole units on the ranking scale. Most of the student comments suggested that the exercise went fast and was easy to execute. This is due to the ease in which SolidWorks has created their animation wizard. One final observation was noted. When asked if they had ever made an animation file before, over ninety percent of the students responded no. This further underscores the educational value of this exercise, since the next dimension in 3-D CAD modeling is time. Figure 10. The Exploded Piston Assembly Used to Create the Animation. VIII. STUDENT OUTCOMES ASSESSMENT The Mechanical Engineering Department at the University of Texas at Austin has established a set of ten student educational outcomes for the department-wide curriculum. Individual courses in the department are expected to contribute to one or more of these outcomes. Student outcomes are defined to be knowledge, skills, abilities, and traits that students can achieve through learning activities in a course. Hence, it is of interest to determine which departmental outcomes are being Figure 11. The Exploded Robotic Blade Assembly Used to Create the Animation.

8 achieved by freshmen students in this Engineering Design and Graphics course. An outcomes survey was conducted at the beginning and end of the course during the summer session. The survey asked the students to rank their skills and abilities supporting each outcome using the following ranking scale: 5 - Very Significant Skill/Ability 4 - Significant Skill/Ability 3 - Some Skill/Ability 2 - A Little Skill/Ability 1 - No Skill/Ability The results for this survey at the beginning and end of the course are shown in Table 2. It can be noted that all outcome rankings improved during the end of course survey. This demonstrates that the course, in general, contributed to the overall educational goals of the department. The outcomes showing the greatest gains from the Pre-to-Post survey were the ability to design Figure 12. Results of the Student Survey for the Pre- and Post- Kinematics Animation Study. mechanical components, the ability to solve open-ended problems, and the ability to conduct experiments and to report the results in a professional manner. These results indicate that the students learned about the openended nature of the design process and that they appreciated the need to report these experiences in a professional format. Table 2 Results of Student Outcomes Survey Outcome Pre-Course Post-Course Difference 1. Knowledge of and ability to apply engineering and science fundamentals to real problems Ability to formulate and solve open-ended problems Ability to design mechanical components, systems, and processes Ability to set up and conduct experiments, and to present the results in a professional manner Ability to use modern computer tools in mechanical engineering Ability to communicate in written, oral and graphical forms Ability to work in teams and apply interpersonal skills in engineering contexts. 8. Ability and desire to lay a foundation for continued learning beyond the baccalaureate degree. 9. Awareness of professional issues in engineering practice, including ethical responsibility, safety, the creative enterprise, and loyalty and commitment to the profession. 10. Awareness of contemporary issues in engineering practice, including economic, social, political, and environmental issues and global impact

9 IX. CONCLUSIONS The freshman Engineering Design and Graphics curriculum has evolved to a new era in which 3-D geometric computer models, and the attendant databases, are the center of instruction. The true power of this new approach is realized when the 3-D solid model data is applied to analysis, simulation, prototyping, and design documentation activities. For example, the digital model databases from the previous exercises can also be transferred to a rapid prototyping system to create real physical prototypes (Figure 13). This paper has proposed a set of ten educational modules for this integrated engineering design and graphics process, and tested it in the classroom with several example exercises supplied by industrial sponsors. Results suggest that student learning outcomes were achieved and that the industrial projects offered real-world classroom experiences. X. ACKNOWLEDGMENTS The authors wish to acknowledge the following corporations who contributed to this educational research project: Ford Motor Company for sponsorship of the Project Centered Education (PROCEED) grant to the University of Texas at Austin and for supplying the piston assembly project. Applied Materials for sponsorship of the Project Centered Education (PROCEED) grant to the University of Texas at Austin and for supplying the robotic blade assembly project. SolidWorks Corporation for their grant of the feature-based modeling software SolidWorks used to build the assembly parts. Structural Research & Analysis Corporation (SRAC) for their grant of COSMOS/Works design analysis used in the FEA study. Figure 13. Rapid Prototypes of the Individual Parts of the Piston Assembly. XI. REFERENCES 1. Barr, R. and Juricic, D. (editors): Proceedings of the NSF Symposium on Modernization of the Engineering Design Graphics Curriculum, Austin, Texas, August Barr, R.E. (1999). Planning the EDG Curriculum for the 21 st Century, Engineering Design Graphics Journal, 63(2): Ault, H.K. (1999). 3-D Geometric Modeling for the 21 st Century, Engineering Design Graphics Journal, 63(2): Cole, W.E. (1999). Graphical Applications: Analysis and Manufacturing, Engineering Design Graphics Journal, 63(2): Tennyson, S.A. and Krueger, T. J. (2001). Classroom Evaluation of a Rapid Prototyping System, Engineering Design Graphics Journal, 65(2): Newcomer, J.L., McKell, E.K., and Raudebaugh, R.A. (2001): Creating a Strong Foundation with Engineering Design Graphics, Engineering Design Graphics Journal, 65(2):