CHAPTER 1 DESIGN AND GRAPHIC COMMUNICATION

CHAPTER 1DESIGN AND GRAPHICCOMMUNICATION

IntroductionOVERVIEWA new machine structure or system must exist in the mind of the engineeror designer before it can become a reality. The design process is anexciting and challenging effort, during which the engineer-designer usesgraphics as a means to create, record, analyze, and communicate designconcepts or ideas.Everyone on the engineering and design team needs to be able tocommunicate quickly and accurately in order to compete in the worldmarket. Like carpenters learning to use the tools of their wade,engineers, designers, and drafters must learn the tools of technicaldrawing. The design team progresses through five stages in the designprocess. To be a successful member of the design team, you mustunderstand the process and know your role.While CAD has replaced traditional drafting toos for many design teamsthe basic concepts of graphic communication remain the same. Yourproficiency in communicating using graphics will be valuable to you and toyour eventual employer.

1-1 Engineering DesignEngineering design is a process which requires a clear understanding ofthe function and performance expected of the end product. It is a way ofconceiving and creating new ideas and then communicating those ideas toothers in a way that can be easily understood. This is accomplished mostefficiently through the use of graphics. Design can be used to reflectpersonal expressions or to enhance product development.

1.2 Design Concepts – Sources forNew Models1.2.3.4.5.Individual CreativityStudy Patent DrawingsExamine Manufactured ProductsStudy the Natural WorldCreativity and Teamwork

1.3 Design ProcessesDesign is the ability to combine ideas, scientificprinciples, resources, and often existing products intoa solution of a problem. This ability to solve problemsin design is the result of an organized and orderlyapproach to the problem known as the designprocess.The design process leading to manufacturing,assembly. marketing, service, and the many activitiesnecessary for a successful product is composed ofseveral easily recognized phases. Although manyindustrial groups may identify them in their ownparticular way, a convenient procedure for the designof a new or improved product is in five stages asfollows:1. Identification of problem, need, or “customer.”2. Concepts and ideas3. Compromise/analysis solutions.4. Models and/or prototypes.5. Production or working drawings.

1.4 Identification of the Problemand the CustomerThe design activity begins with the recognition of a problem and/or thedetermination of a need or want for a product, service, or system and theeconomic feasibility of fulfilling this need.

1.5 Identification of the Problemand the CustomerAt this stage, many ideas are collected—reasonable and otherwise—forpossible solutions to the problem. The ideas are broad and unrestrictedto permit the possibility of new and unique solutions. The ideas may befrom individuals, or they may come from group or team brainstormingsessions where one suggestion often generates many more ideas fromthe group. As the ideas are elicited, they are recorded for futureconsideration and refinement.

1.6 Compromise / Analysis SolutionsVarious features of the many conceptual ideas generated in thepreceding stages are selected after careful consideration and combinedinto one or more promising compromise solutions. At this point the bestsolution is evaluated in detail, and attempts are made to simplify it so thatit performs efficiently and is easy to manufacture, repair, and evendispose of when its lifetime is over.

1.7 Models and PrototypesA 3-D CAD model or scale model isoften constructed to study, analyze,and refine a design. A full-sizeworking model made to finalspecifications, except possibly formaterials, is known as a prototype.The prototype is tested andmodified where necessary, and theresults are noted in the revision ofthe sketches and working drawings.Figure below shows a prototype ofthe magnetic levitation train.

1.8 Production or Working DrawingsTo produce or manufacture a product, a final set of production orworking drawings is made, checked. and approved.In industry the approved production design layouts are turned over tothe engineering department for the production drawings Thenecessary views are drawn for each part to be made, and completedimensions and notes are added so that the drawings will describethese parts completely. These are called detail drawings.

Design is an IterativeProcess Begins with arecognition of need for aproduct, service, orsystem During the idea phaseencourage a widevariety of solutionsthrough brainstorming,literature search, andtalking to users Best solutions areselected for furtherrefinement Models or prototypes aremade and problems thatarise may require new ideasto solve and a return to anearlier stage in the process Finally drawings arereleased to manufacturingfor production

1.9 Communicating Using GraphicsAlthough people around the world speak different languages, graphiccommunication has existed since the earliest of times. The earliestforms of writing were picture forms, such as the Egyptianhieroglyphics shown in Figure 1.16. Later these forms were simplifiedand became the abstract symbols used in writing today.Graphic representation has developed along two distinct lines: artisticand technical. From the beginning of time, artists have used drawingsto express aesthetic, philosophic, or other abstract ideas. Peoplelearned by looking at sculptures, pictures, and drawings in publicplaces. Everybody could understand pictures and they were aprincipal source of information.

1.10 Earlier Technical DrawingPerhaps the earliest knowntechnical drawing in existence isthe plan view for the design of afortress drawn by the Chaldeanengineer Gudea and engraved ona stone tablet.

1.11 Earlier Descriptive GeometryDescriptive geometry usesgraphics and projections tosolve spatial problems.Gaspard Monge (1746 –1818) is considered theinventor of the descriptivegeometry. While he was aprofessor at PolytechnicSchool in France, hedeveloped the principles ofprojection that are now thebasis for technical drawing.

1.12 Modern Technical DrawingIn 1876 the blueprint process was introduced at the PhiladelphiaCentennial Exposition. Up to this time, creating technical graphics wasmore or less an art, characterized by fine-line drawings made toresemble copperplate engraving, by shade lines, and by water-colorwashes These techniques became unnecessary after the introduction ofblueprinting, and drawings gradually became less ornate to get betterresults in reproduction. This was the beginning of modem technicaldrawing. Technical drawing became a relatively exact method ofrepresentation, often making it unnecessary to build a working modelbefore a device could be constructed.

1.13 Drafting StandardsStandards for the appearance of technical drawings have beendeveloped to ensure that they are easily interpreted across the nationand around the world. As you learn to create technical graphics, youwill adhere to these standards. This will allow you to create drawingswhich 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 ofAutomotive Engineers (SAE), and the American Society of MechanicalEngineers (ASME) have been the principal organizations involved indeveloping the standards now in place. As sponsors, they haveprepared the American National Standard Drafting Manual—Y14,which consists of a number of separate sections that are frequentlyupdated. (See Appendix I.)

1.15 DraftingDrawings have accompanied and made possible technical advancementsthroughout history. Today the connection between engineering and scienceand the ability to visualize and communicate graphically is as vital as ever.Engineers, scientists, and technicians need to be proficient in expressingtheir ideas through technical graphics, using both sketching and CAD.Training in the application of technical drawing is required in virtually everyengineering 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 arefound in nearly every engineering textbook, and instructors often requireyou to supplement calculations with technical sketches, such as free bodydiagrams. So mastering a course in technical drawing using both sketchingand CAD will help you not only in your professional work, but also in manycourses.

Training and Continuing EducationTraining is an essential part of continuing education and a wiseinvestment. Training enables you to: work faster, smarter and become more productive increase your engineering expertise and value to yourcompany and customers make analysis and simulation an integral part of your designprocess 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 tomarket and make better, safer products at a lower cost.

1.16 ProjectionsModern technical graphics usesindividual views or projections tocommunicate the shape of a 3-Dobject or design on a sheet ofpaper. You can think of everydrawing as involving the spatialrelationship of four things:1. The observer’s eye, or thestation point2. The object3. The plane of projection4. The projectors, also calledvisual rays or lines of sight.There are two main types ofprojection—perspective andparallel.

Classification of Projections

Summary Engineering drawing can be a universal language tocommunicate your ideas. The engineering design process uses sketching andCAD to communicate and record ideas. A single CAD database can be used to produce manytypes of drawings and models used throughout thedesign process.

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 pla