The Development Of A Project Based Introduction To Manufacturing Laboratory Involving A Stirling Engine


Many current introduction to manufacturing courses contain a series of individual labs illustrating different processes: turning, milling, polymer processing, casting, etc. Although students leave these courses with an understanding of manufacturing processes and some limited experience analyzing them, they all too often dislike these laboratories since they discourage self-learning, and often appear contrived. In addition, many of these labs do not give students hands-on experience with a variety of the subtle manufacturing-related issues like tolerances, surface finish, quality, assemblability, and the tradeoffs between accuracy and time, since these issues have essentially been designed out of the exercises. A new project-based laboratory has been developed and tested where students manufacture a working Stirling engine. The engine contains approximately 30 parts that require the use of a wide range of processes. Although complex, the engine can be produced by teams with as few as eight students within a one quarter course. The project is a truly team-driven exercise, requiring both student participation and communication, and has received extremely enthusiastic response. This paper describes experience in developing a project-based manufacturing laboratory, and includes a description of the manufacturing processes employed, associated exercises, and expected outcomes. Introduction At the University of Washington, we currently have one undergraduate course devoted to manufacturing processes, ME 304. This course is intended to be taken during the middle of the Junior year, and has minimal prerequisites: knowledge of stress-strain relations in engineering materials, and metallurgy of ferrous and nonferrous metals. The course is 3 quarter-credit hours, and consists of two one-hour lectures and a three hour laboratory each week. Lectures cover a wide range of topics, including: concurrent engineering concepts, machining, bulk deformation, joining processes, polymer processing, and casting. The course is designed to provide engineering students with the necessary knowledge to use materials effectively, and introduce them to processes and equipment that can bring their designs to reality. The course also presents the basic processes and fundamentals of manufacturing, and intends to provide a foundation for the practice of professional engineering. Previously, the lab portion of the course consisted of eight individual laboratories, including a safety seminar. For each of these labs, a process was demonstrated, and specimens were generated for further analysis. For example, the lab instructor would pour fluidity spirals at different levels of superheat for the casting lab. Students would then measure the length of the fluidity spirals and generate a two page report describing their findings. Laboratories that had been used in the past included: 1. Heat Treating 2. Casting Processes 3. Sheet Metal Forming Springback P ge 355.1 4. Machining Processes-All lathe work 5. Welding Processes Although these labs illustrated a number of manufacturing processes and also gave students considerable experience generating technical reports, students generally disliked these exercises. A critical evaluation yielded the following observations: 1. These laboratories were primarily demonstrations and students were not always allowed to participate directly. A majority of the students were only allowed to observe. 2. Often times there were aspects of the labs that students would have explored on their own, but were not given the opportunity. Usually, the labs were so structured that students could not spend their own time with the equipment. 3. The labs were not tied together in any way. 4. Even though this was a manufacturing lab, students rarely produced anything other than test specimens. To address these observations, a quarter-long team project was introduced, where groups of approximately 10 students manufacture a working Stirling engine, as shown in Fig. 1. Hands-on labs where students produce working mechanical devices are far from new. Since the late 1950’s however, many of these labs have been replaced with analytical work and exercises in engineering science [1,2]. Dejong [1] reminds us that it was the Grinter Report [3] that sent engineering education in a much more theoretical and science based direction. Although these changes in engineering curricula led to many improvements, practice-based courses in the areas of design and manufacturing have suffered. In the past several years, many authors have reported their efforts to reintroduce engineering design and manufacturing to their curricula [2,3,4,5]. Most of these courses include hands-on exercises [2], which promote active learning and emphasize practical experience. Two such exercises in the area of manufacturing education are the gearbox produced at Lafayette College [2], and another Stirling Engine Project at MIT [5]. Although similar to our own project, these institutions present manufacturing processes in slightly different ways. The most notable differences occur due to quarter vs. semester systems. This paper details our experiences at the University of Washington by first discussing the course goals and expected outcomes, and then describing some issues regarding institutionalization of this laboratory project, including plans for future work. Course Objectives In addition to the broad goals of the course, the goals of this new set of laboratories were formulated as follows: 1. Give students the experience and satisfaction of manufacturing a working mechanical device. 2. Encourage self-learning. 3. Introduce a truly team-driven project requiring participation by all students. 4. Provide an environment where many manufacturing related issues like tolerances, design for manufacturability, etc. arise and can be discussed. 5. Engage students in a project which requires them to practice engineering design. P ge 355.2 6. Give students experience in planning and executing a project in a specified amount of time. Although mechanical engineering students are typically taught machine design, they are rarely provided with the opportunity to design processes. For this project, students did very little part design and spent considerable time developing processes to produce their parts. Expected Outcomes In addition to the above goals, we also wanted to see that students had improved their level of skill in a number of areas. Morell de Ramirez and Beauchamp [7] have categorized engineering skills into three broad groups: (1) Design/problem solving, (2) Communication, (3) Awareness of self, others, and the environment. We intended for every student to gain experience in each of these areas as described below. (1) Design / Problem Solving For this project, students must start by looking for information/data on the processes to produce their parts. Most of them have very little experience in a machine shop. They must then evaluate this information and make decisions about what processes they will use. For example, some students decided to use the CNC milling machine to produce their flywheel, where others used the lathe. In this respect, student are given the option design their own processes, and have the opportunity to explore these designs on their own. In addition to self learning, students are also required to manage their projects. These labs span eight weeks, requiring a modest amount of planning. Since there are about 30 parts for the engine, and typically only 10 students per lab, each student is responsible for approximately three parts, depending on complexity. These parts must be completed before assembly begins, and time must be scheduled to use the various pieces of equipment. For example, scheduling was especially important for the milling machine, since our shop only had two. (2) Communications Students are required to organize different process ideas and formulate questions so that “experts” can help them. They need to communicate these ideas orally and with simple sketches. Through the development of the final process plans (discussed below), they must communicate, in detail, how their parts were produced. The students must then use the WWW for communication by posting their process plans for future students to see and benefit from. (3) Awareness of self/others This laboratory exercise develops a great deal of self-esteem, especially for those students who have little or no prior hands-on experience. We find that most of our students have very little or no shop experience. This lack of experience keeps them away from projects that may require these skills. After completing the labs, all students have the confidence to build simple prototypes of their designs, and are aware of the proper tools and safety issues when accomplishing this task. This project is also intended to develop a great deal of teamwork skills. Unlike most other projects the students will experience, this project requires interpersonal relationships to develop over several months instead of several weeks. It also requires students to work in very diverse groups; within a single lab section there are some students who have worked as professional machinists, and some who have never stepped into a shop in their lives. There is also a great deal of cultural diversity, with some students who speak English fluently and others who may have only been in the U.S. for two or three years. In addition, every student is a member of a relatively large group, about 10 students, requiring much more effective communication than the students are used to. Some students will naturally fall into a leadership role, Page 355.3 while others will simply produce their parts. Regardless, every student understands that their contribution is significant, for without their help, the engine will not run at the end of the quarter. Lab Schedule The schedule for the lab is shown in Table 1.