Chapter 1 Design and Graphic Communication
Total Page：16
File Type：pdf, Size：1020Kb
CHAPTER 1 DESIGN AND GRAPHIC COMMUNICATION Introduction OVERVIEW A new machine structure or system must exist in the mind of the engineer or designer before it can become a reality. The design process is an exciting and challenging effort, during which the engineer-designer uses graphics as a means to create, record, analyze, and communicate design concepts or ideas. Everyone on the engineering and design team needs to be able to communicate quickly and accurately in order to compete in the world market. Like carpenters learning to use the tools of their wade, engineers, designers, and drafters must learn the tools of technical drawing. The design team progresses through five stages in the design process. To be a successful member of the design team, you must understand the process and know your role. While CAD has replaced traditional drafting toos for many design teams the basic concepts of graphic communication remain the same. Your proficiency in communicating using graphics will be valuable to you and to your eventual employer. 1-1 Engineering Design Engineering design is a process which requires a clear understanding of the function and performance expected of the end product. It is a way of conceiving and creating new ideas and then communicating those ideas to others in a way that can be easily understood. This is accomplished most efficiently through the use of graphics. Design can be used to reflect personal expressions or to enhance product development. 1.2 Design Concepts – Sources for New Models 1. Individual Creativity 2. Study Patent Drawings 3. Examine Manufactured Products 4. Study the Natural World 5. Creativity and Teamwork 1.3 Design Processes Design is the ability to combine ideas, scientific principles, resources, and often existing products into a solution of a problem. This ability to solve problems in design is the result of an organized and orderly approach to the problem known as the design process. The design process leading to manufacturing, assembly. marketing, service, and the many activities necessary for a successful product is composed of several easily recognized phases. Although many industrial groups may identify them in their own particular way, a convenient procedure for the design of a new or improved product is in five stages as follows: 1. Identification of problem, need, or “customer.” 2. Concepts and ideas 3. Compromise/analysis solutions. 4. Models and/or prototypes. 5. Production or working drawings. 1.4 Identification of the Problem and the Customer The design activity begins with the recognition of a problem and/or the determination of a need or want for a product, service, or system and the economic feasibility of fulfilling this need. 1.5 Identification of the Problem and the Customer At this stage, many ideas are collected—reasonable and otherwise—for possible solutions to the problem. The ideas are broad and unrestricted to permit the possibility of new and unique solutions. The ideas may be from individuals, or they may come from group or team brainstorming sessions where one suggestion often generates many more ideas from the group. As the ideas are elicited, they are recorded for future consideration and refinement. 1.6 Compromise / Analysis Solutions Various features of the many conceptual ideas generated in the preceding stages are selected after careful consideration and combined into one or more promising compromise solutions. At this point the best solution is evaluated in detail, and attempts are made to simplify it so that it performs efficiently and is easy to manufacture, repair, and even dispose of when its lifetime is over. 1.7 Models and Prototypes A 3-D CAD model or scale model is often constructed to study, analyze, and refine a design. A full-size working model made to final specifications, except possibly for materials, is known as a prototype. The prototype is tested and modified where necessary, and the results are noted in the revision of the sketches and working drawings. Figure below shows a prototype of the magnetic levitation train. 1.8 Production or Working Drawings To produce or manufacture a product, a final set of production or working drawings is made, checked. and approved. In industry the approved production design layouts are turned over to the engineering department for the production drawings The necessary views are drawn for each part to be made, and complete dimensions and notes are added so that the drawings will describe these parts completely. These are called detail drawings. Design is an Iterative Process • Begins with a • Models or prototypes are recognition of need for a made and problems that product, service, or arise may require new ideas system to solve and a return to an • During the idea phase earlier stage in the process encourage a wide • Finally drawings are variety of solutions released to manufacturing through brainstorming, for production literature search, and talking to users • Best solutions are selected for further refinement 1.9 Communicating Using Graphics Although people around the world speak different languages, graphic communication has existed since the earliest of times. The earliest forms of writing were picture forms, such as the Egyptian hieroglyphics shown in Figure 1.16. Later these forms were simplified and became the abstract symbols used in writing today. Graphic representation has developed along two distinct lines: artistic and technical. From the beginning of time, artists have used drawings to express aesthetic, philosophic, or other abstract ideas. People learned by looking at sculptures, pictures, and drawings in public places. Everybody could understand pictures~ and they were a principal source of information. 1.10 Earlier Technical Drawing Perhaps the earliest known technical drawing in existence is the plan view for the design of a fortress drawn by the Chaldean engineer Gudea and engraved on a stone tablet. 1.11 Earlier Descriptive Geometry Descriptive geometry uses graphics and projections to solve spatial problems. Gaspard Monge (1746 – 1818) is considered the inventor of the descriptive geometry. While he was a professor at Polytechnic School in France, he developed the principles of projection that are now the basis for technical drawing. 1.12 Modern Technical Drawing In 1876 the blueprint process was introduced at the Philadelphia Centennial Exposition. Up to this time, creating technical graphics was more or less an art, characterized by fine-line drawings made to resemble copperplate engraving, by shade lines, and by water-color washes These techniques became unnecessary after the introduction of blueprinting, and drawings gradually became less ornate to get better results in reproduction. This was the beginning of modem technical drawing. Technical drawing became a relatively exact method of representation, often making it unnecessary to build a working model before a device could be constructed. 1.13 Drafting Standards Standards for the appearance of technical drawings have been developed to ensure that they are easily interpreted across the nation and around the world. As you learn to create technical graphics, you will adhere to these standards. This will allow you to create drawings which communicate clearly and cannot be misinterpreted by others. In the United States the American National Standards Institute (ANSI), the American Society for Engineering Education (ASEE), the Sodety of Automotive Engineers (SAE), and the American Society of Mechanical Engineers (ASME) have been the principal organizations involved in developing the standards now in place. As sponsors, they have prepared the American National Standard Drafting Manual—Y14, which consists of a number of separate sections that are frequently updated. (See Appendix I.) 1.15 Drafting Drawings have accompanied and made possible technical advancements throughout history. Today the connection between engineering and science and the ability to visualize and communicate graphically is as vital as ever. Engineers, scientists, and technicians need to be proficient in expressing their ideas through technical graphics, using both sketching and CAD. Training in the application of technical drawing is required in virtually every engineering school in the world. In most technical professions the ability to read a drawing is a necessity, whether or not you produce drawings yourself. Technical drawings are found in nearly every engineering textbook, and instructors often require you to supplement calculations with technical sketches, such as free body diagrams. So mastering a course in technical drawing using both sketching and CAD will help you not only in your professional work, but also in many courses. Training and Continuing Education Training is an essential part of continuing education and a wise investment. Training enables you to: work faster, smarter and become more productive increase your engineering expertise and value to your company and customers make analysis and simulation an integral part of your design process take advantage of advanced software capabilities and meet with other users to exchange ideas and techniques. Knowledgeable users can then help companies speed up time to market and make better, safer products at a lower cost. 1.16 Projections Modern technical graphics uses individual views or projections to communicate the shape of a 3-D object or design on a sheet of paper. You can think of every drawing as involving the spatial relationship of four things: 1. The observer’s eye, or the station point 2. The object 3. The plane of projection 4. The projectors, also called visual rays or lines of sight. There are two main types of projection—perspective and parallel. Classification of Projections Summary Engineering drawing can be a universal language to communicate your ideas. The engineering design process uses sketching and CAD to communicate and record ideas. A single CAD database can be used to produce many types of drawings and models used throughout the design process. .