The goal of this paper is to study the importance of drawing (both formal drafting and informal sketching) in the process of mechanical design. This AOL can be extended to state that we intend to show the necessity of drawing during all the developmental stages Of a mechanical design. Through the information presented here, the requirements for future computer aided design tools, graphics education, and further studies will be developed. All mechanical engineers are taught drafting.
Thus, most engineers are skilled at making and interpreting these formal mechanical drawings. These drawings are representations of a final design (the end product of the design process) and they are intended to archive the completed design and communicate it to other designers and manufacturing personnel. Additionally, engineers are notorious for not being able to think without making “back-of-the-envelope” sketches of rough ideas. Sometimes these informal sketches serve to communicate a concept to a colleague, but more often they just help the idea take shape on paper.
It is in considering how these sketches help an idea take form that gives a hint that drawing’s role in engineering is more than just to archive a concept or to communicate with others. Understanding the use of both drafting and sketching in design is important to help formulate the future development of Computer Aided Design or Drafting (CAD) systems. As CAD evolves and becomes more “intelligent,” the question of what attributes these systems must have becomes more important. In the past CAD system attributes have primarily been driven from developments in the computer industry.
It is only through understanding drawing’s importance in the design process that these systems can be based on design needs. (l ) Additionally, the pressures of CAD tool development, faculty time demands, and course expenses cause academic institutions to reevaluate the content of their “graphics” courses. Understanding drawings importance in the design process helps establish what skills need to be aught to engineers during their training. This paper is organized by first, in Section II, clarifying the types of drawings used in mechanical design.
The hypotheses to be addressed in this paper are given in Section Ill. A discussion of research on the understanding of visual imagery to be used as a basis for arguments in support of the hypotheses is in Section IV. In Section V is a discussion of the results of data taken on how mechanical engineers use drawings during design. Lastly, in Section VI, is a discussion of how well the hypotheses have been supported and the implications of our findings on CAD development, educational requirements and future research directions. . TYPES OF DRAWINGS USED IN DESIGN Engineers make many types of marks-on-paper.
In research, to be described in Section V, we have broken down these marks into two main groupings: support notation and graphic representations. Support notation includes textual notes, lists, dimensions (including leaders and arrows) and calculations. Graphic representations include drawings of objects and their functions, and plots and charts. Mechanical design graphic representations are often scale drawings made tit mechanical instruments or CAD computer systems. These drawings, made in accordance with a set of widely accepted rules, are defined as having been drafted.
Sketches, on the other hand, are defined as “free hand” drawings. They are usually not to scale and may use shorthand notations to represent both objects and their function. A differentiation must be made between the act of graphic representation and the medium on which it occurs. The medium, whether it be paper and pencil, a computer stylus on a tablet, chalk on a blackboard or other medium may put interface restrictions on the representation. The following concussions are concerned with what is being represented, not with how the representation is made.
However, the discussions point to the medium’s restriction on representation and the need for improved interfaces. Another aspect of drawings to be considered is the level of abstraction of the information to be represented. During the design process, the design is refined from an abstract concept to a final, detailed, drafted design. This can be clearly seen in an example taken from one of our studies described in Section V. In this study the designer was developing an assembly to hold three batteries for a clock/calendar in a computer.
Figure 1 is a compilation of all the sketches and drawings one subject made during the development of a battery contact in this design. The number under each graphic image is the percentage of the way through the design when the representation was made. The component is refined from a sketch that contains primarily functional information to a refined, scale drawing of the final form. The first sketch in Fig. 1 shows two contacts (represented as circles) and a connection between them for current flow (represented as a line). The cosmology here is clearly functional. Figure 1 .
The evolution of a battery contact – total protocol time of 8 hours ND 34 minutes. Even though a good percentage of an engineer’s graphic representation is informal sketching, drafting is the focus of most engineering training and the strength Of CAD systems. On the other hand, most engineers receive no formal training in sketching. It is often assumed to be some natural ability. Three typical texts used in teaching undergraduate “mechanical” drawing were reviewed [1, 2, 3]. Each of these presented only a few pages of information on sketching. Additionally, CAD systems do not support sketching in any meaningful way.
For the purposes of this paper, the term CAD is defined as the use of interactive computer graphics to help solve a mechanical design problem. Current CAD tools aid the mechanical design process in four ways: as an advanced drafting tool; through assisting in the visualization of hardware and data; by improving data organization and communication; and through being used as a pre- and post-processor for computer based analytical techniques such as finite element analysis, weight and mass properties, kinematics analysis, etc. For all these uses, the “design” must be refined to the point that a scale drawing of it can be made.