Geometric Dimensioning and Tolerancing (GD&T), due to the inherent complexity, is a challenging topic to teach and learn, especially at the undergraduate freshman level. Many institutes either cover GD&T on a superficial level or choose to overlook it. In fact, this particular subject can be a standalone course due to the concept-heavy nature of it. It is an extremely important tool that manufacturers and engineers use on a daily basis across several industries. Incorporating such a broad subject in an already busy curricula remains a major challenge for many academic institutes, including ours. At the current university, this has been an ongoing issue for the past several years. While some universities incorporate GD&T incrementally throughout the undergraduate curriculum, our institute is unable to do so given the mandatory cooperative education (co-op) program. Each engineering student is required to complete three semesters of mandatory co-op with a local employer, and the fifth semester marks the beginning of their co-op journey. The knowledge and skill level of our students in GD&T at the beginning of their co-op is a major concern for several employers. These employers have to expend significant resources to train our students (and our graduates). To address this growing concern, the authors decided to incorporate a practical project in the freshman engineering course EGR 107: Introduction to Engineering II.

EGR 107 is a two-hour course offered twice a week for multidisciplinary engineering students in their second semester. It is the second course in the principles and practice of engineering analysis, design, construction, and evaluation. The topics in this already content-dense course include design process, graphical communication, solid modeling, computer-aided manufacturing, computer programming, and principles of digital and analog electronics. This course already has a culminating project that is time consuming, and it was decided that the existing project cannot be modified. Thus, the onus was on the authors to implement a new creative activity to incorporate GD&T in an effective manner. Merely lecturing on GD&T and providing simple examples to students was not the scope of this endeavor. During the Spring/Summer 2019 semester, a practical project on reverse engineering a hedge trimmer was added to the syllabus as a pilot study. A secondary motive of the project was to enhance project collaboration. The duration of the project was three weeks, and it was seamlessly incorporated into the course.  

For the project, a Ryobi hedge trimmer Model No. RY39500 was used. The students were divided into seven groups, and each group was given a mechanical component from the assembly. First, each group was tasked with taking the necessary measurements to create a Computer Aided Design (CAD) model of their component in an effort to commence the reverse engineering process. The CAD model was then additively manufactured using fused deposition modeling. A detailed drawing of each component was created and GD&T concepts and symbols were applied to the drawing following ASME/ANSI Y14.5-2009 standards. The project was very well received by the students. It enhanced their understanding and skills necessary to implement GD&T concepts and symbols both in practice and in preparing engineering drawings. The 3-D printed parts were shared among the groups and the manufactured parts were fit together to replicate the real life assembling. This group collaboration confirmed the skills and efficient application of GD&T concept on the CAD models, their relevant drawings, and eventually the accuracy and precision of assembling the physical parts they made which was in confirmation with the original parts assembly process.


Reverse Engineering a Hedge Trimmer: A Practical Approach to Incorporate Geometric Dimensioning and Tolerancing (GD&T) Effectively in an Undergraduate Freshman Engineering Course

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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