Engineering Design, Cad And Fabrication Skills Within A Biomedical Engineering Context

The challenge of exposing biomedical engineering (BME) students to the broad array of core engineering and biology topics often makes it difficult to adequately address supporting skills such as computer-aided design (CAD) and fabrication in the undergraduate curriculum. This paper will present a six-week module from a course developed to introduce students to hands-on skills that could be important for BME students in design and their future careers. The BME “Cube of Knowledge” is a design and prototyping project where six design teams work together to create a six-sided cube. Each team first develops a CAD model, rapid prototype, and engineering drawings for one side of the six-sided cube. After the creation of engineering drawings, each team fabricates their individual side of the cube with a conventional milling machine based on the engineering drawings. After each team has manufactured their own part, the six individual parts are assembled in class. A successful design and manufacturing experience would predicate that the six parts, or “sides,” combine to create an assembly in the shape of a cube, where each of the six sides are fabricated from a different material commonly used in biomedical engineering. Most materials used are biocompatible polymers, but metals such as stainless steel and aluminum have also been used. Each step of this design and prototyping project has a different emphasis. For example, in the initial CAD model and rapid prototyping portion, students are required to use several advanced CAD functions to create geometries that would be difficult or impossible to fabricate using conventional machine shop tools. The CAD models are then simplified for fabrication using a milling machine, with the emphasis in the machine shop focusing on each student gaining handson experience machining the part. Preliminary student assessment indicates that the students feel that designing, rapid prototyping, and physically producing the Cube of Knowledge was both a valuable and enjoyable experience. The vast majority of students agree that the project experience will be valuable for senior design and their future engineering careers. Additionally, they indicated that they would like to see the module expanded to include a larger variety of fabrication techniques and more time for basic skill development. Introduction Given the broad spectrum of topics that must be addressed in an undergraduate biomedical engineering (BME) curriculum it is difficult to provide adequate exposure to students in design and manufacturing technology such as computer-aided design (CAD) and conventional machining [1]. These skills are vital for engineers to communicate design ideas, and a basic understanding of manufacturing technology helps enable students to consider how a design on paper might be turned into a physical prototype. Faculty observations and student and alumni feedback have indicated that these skills are vital for success in classroom design projects such as senior design, as well as for careers in industry [2]. P ge 15482.2 Within the biomedical engineering curriculum at Bucknell University, a fabrication and experimental design course is integrated into a four course design sequence where two courses comprise the senior capstone experience and two courses teach supplementary material. The intent of the sequence is to provide experience with a variety of skills that are valuable for both senior design projects and in BME careers after graduation. As designed, the Fabrication and Experimental Design course is not a full-credit course, meeting only two days a week for onehour sessions, with several lab sessions (approximately 2 hours long) scheduled outside of normal classroom hours. Included among the skills introduced in the course are the use of CAD software, an introduction to rapid prototyping machines and a hands-on introduction to the machining tools of the College of Engineering’s machine shop. These skills are taught for the first half of the semester, with the second half of the semester currently devoted to other biolaboratory skills such as cell culturing and biocompatibility experiments, along with a review of biostatistics. During the initial course offerings in the fall of 2006 and 2007, students were taught the CAD software program SolidWorks, and were exposed to manufacturing and machining technology by demonstrations given by the staff in the College of Engineering’s machine shop. Faculty observation as well as student feedback indicated that more hands-on exposure to machining skills would be beneficial. Therefore, a project-based design and fabrication experience was introduced to the course in the fall of 2008 and further enhanced in the fall of 2009 to marry the CAD and fabrication portions of the course. This project allowed students an opportunity to follow a process from design conception through prototyping and offer a hands-on opportunity for final production. The general idea for the project, colloquially referred to as the “Cube of Knowledge” was to provide a context to teach several aspects of engineering design, CAD and fabrication skills with a project that involved the whole class, but afforded individual students the chance to run the machines and develop personal experience with the skills, technology, and effort that is required to produce a precisely machined part. Project Overview The Cube of Knowledge project consists of a very simple overall design made up of six rectangular pieces that are assembled to create an equilateral cube. The rectangular pieces are affixed via two different specified types of screws. During the project, the class functions as six design teams of approximately 2-4 students, where each team is responsible for final design details on a single side of the cube. Each team designs a different side of a cube, which will later be assembled to form a complete cube that will be fastened together by screws. Each side of the cube is made from a different material relevant to the biomedical engineering field which exposes the class to a wide variety of materials that can be used in the fabrication process and in machining operations. Materials that have been used include: acetal (Delrin ® ), chlorinated polyvinyl chloride (CPVC), acrylonitrile butadiene styrene (ABS), polycarbonate, acrylic, polypropylene (PP), aluminum, and stainless steel. An example SolidWorks model and a photo of a final product are shown in Figure 1.