Dissection Module

"Engineering Dissection 101": A five week multimedia module where students, by taking apart and reassembling a simple mechanical assembly (e.g., a valve, a coupling, etc.), learn the importance of providing, at the design stage, for accessibility in view of inspection, maintenance, repair or replacement; for choice of material for durability, robustness or recycling; for choice of manufacturing process (casting, forging, machining, welding, etc.) dictated by use and economy; for choice of form dictated by function, esthetics and economy, etc.; where they develop the ability to observe and describe graphically, verbally and in writing (e.g. by writing a manual for disassembling or reassembling their piece of equipment).
Students in this course would already have completed 15 weeks of CAD drafting instruction and would be familiar with orthographic projections, drawing conventions, dimensioning and tolerances and with some concepts of production drawings.

The multimedia module would include written material for instruction and reference, some videos (for instance on manufacturing processes) some software (e.g., on economics), etc. It would be "media-intensive" in the sense that it would consist mostly of self-taught, self-paced instructional material leaving the instructor readily available for tutoring, coaching and direct involvement with the student groups.

Typically, students working in groups of two would learn and practice:

Taking a simple mechanism apart and reassembling it.

Building a vocabulary of common engineering terms (valves, pistons, cylinders, screws, nuts, rivets, guides, bushings, shafts, journal bearings etc...)

Taking graphical, notes by sketching: the individual parts (perspective, and axonometric views, dimensioned freehand orthographic views) and the assembly, (exploded view and external or sectional orthographic views).

Taking written notes by writing assembly and disassembly instructions. (A technique might be to take an audio or video record as they disassemble and reassemble the unit and to edit this into a coherent "expletiveless" written record.)

The material that might be included for teaching engineering sketching would be such as that in Croft et al., Engineering Graphics, Wiley, 1989, Chapter 3, Chapter 4 (Set 4-15), Chapters 5 and 6, selected sections from Chapter 9 and from Appendix A on Advanced Dimensioning topics.

The students would be expected to complete:

A set of detailed orthographic dimensioned freehand drawings suitable for shop manufacturing together with axonometric views.

An assembly drawing of the unit including an exploded view of the assembly.

A written analysis of the design explaining how each piece would have been manufactured and assembled and a critique of the design with suggestions on how it could be improved.

A short video tape (5 to 8 minutes) of an oral presentation explaining the operation, use and design of the simple mechanism constituting the case study.

Of course, it is not expected that students will learn all this in great depth. The purpose is to make them aware, through a simple case study, that here are some of the important factors a designer has to keep in mind during the design process and that they will, therefore, have to learn about in the course of their further studies. The approach to take is more towards awakening the students to the multiplicity and diversity of topics necessary to perform design than presenting them with treatises on any of these topics.

Chronology of Events

Week 1
As this five week portion of the EID 103, Principles of Design evolved, it became obvious that a certain degree of flexibility in presenting the material was required depending on the background of the students. Most of the students in the class had just completed EID 101 which includes an extensive amount of mechanical drawing theory and practice. Emphasis was therefore placed on freehand sketching and the so-called "Brain-Hand-Image-Eye" process of drawing as a continual cycle of development and expression.

An important objective of this portion of the course was the intensity of the "hands-on-" design experience to be learned by the actual disassembly and re-assembly of fairly complicated electromechanical devices. Following the "heuristic" teaching method, which encouraged the student to discover design concepts himself by asking questions, the class was divided into twelve groups of two or three, with each group given a 5 1/4 inch computer floppy disk drive to disassemble. Tools were supplied to each group including precision screwdriver and hex-key sets as well as other miscellaneous items. A short lecture on the concepts of a disk drive was given using the overhead projector and accompanying hand out sheets. Thus students began actual hands on work at the first meeting of the class.

Week 2
In the second week, a short lesson was given on the concepts of rational design exposing the student to the ideas of functional requirements, design parameters, and external, human and input constraints. In accordance with the heuristic approach, a list of design questions to be answered by the student in the course of disassembly and reassembly, was presented. An industrial size butterfly valve was then disassembled in front of the class as an example of the heuristic approach to be applied to the disk drive. Several written articles pertaining to design were then distributed to the class. The students continued to disassemble the drives and were asked to then reassembly them before the end of the class.

Week 3
As was to be expected only a few students were able to successfully reassemble the drives. This demonstrated the importance of sketching, blow up drawings, wiring diagrams and notes in the course of disassembly. Photographs of the drive in various stages of disassembly were displayed as a guide for the students to complete their assemblies. Each group was then challenged to devise their own system or procedure for a successful disassembly and reassembly of the drive down to the smallest possible components. This included disassembly of the stepper motor for the read-write head, the drive motor, and hub bearings, along with an inventory of the many small screws, nuts, bolts and sensors. All sketch work and notes were to be done in a log book for later submission as part of the class grade. Students were also invited to bring cameras to class and utilize the concepts of oblique, isometric and orthographic projection with photographs. The class remarked that they were able to work much faster during their second attempt illustrating an example of the "learning curve" on hands on manufacturing.

Week 4
The class continued documenting free hand sketches and notes in their log books, and a discussion was held on the various written articles distributed to the class regarding concepts of design including the manufacturing process, re-cycling of materials and environmental consciousness. In preparation for the audio/visual student presentation of next week, the class was coached for about one hour by an adjunct professor on how to exploit the VCR for report presentation.

Week 5
Final report were presented and commented on by the class. Each group worked together on an audio-visual presentation of design concepts related to their mechanical disassembly and reassembly of the floppy disk drive. The presentation was recorded with a VCR. Individual log books with the disassembly procedure, sketches, answers to heuristic design questions and in many cases, photographs were also collected. The remaining time was used for the students to complete final assembly and turn in the disk drives and tools to the instructor.

The students commented enthusiastically about the course. For many of them, it was their first opportunity to use precision tools in a "hands on" environment involving state of the art engineering technology.