2OBJECTIVES 1. Describe the role of computer-aided design in project development.2. Define rapid prototyping and list four rapid prototypingtechnologies.3. Describe the role of design in manufacture, assembly,disassembly, and service.4. Define modeling for assembly.5. Describe the role of material selection and material properties.6. List the major manufacturing processes.7. Look up accuracy and surface finishes for manufacturingprocesses.8. Describe the role of measuring devices in production.9. List factors that determine the cost of manufactured goods.10.Define computer-integrated manufacturing.
3UNDERSTANDING MANUFACTURING Manufacturing is generally a complex activity involving a wide variety of resources and activities such as:• Product design• Purchasing• Marketing• Machinery and tooling• Manufacturing• Sales• Process planning• Production control• Shipping• Materials• Support services• Customer service
4The Design Process and Concurrent Engineering Sharing product design data among multiple usersconcurrently can shorten the time to product realizationand result in a better product.Design and manufacturing activities have traditionally taken place sequentially rather than concurrently or simultaneously.
5COMPUTER-AIDED DESIGN AND PRODUCT DEVELOPMENT Computer-aided design (CAD) allows the designer to conceptualize objectsmore easily without having to make costly illustrations, models, or prototypes.These systems are now capable of rapidly and completely analyzing designs, from a simple bracket to complex structures.(Ford Motor Company/Dorling Kindersley.)
6Computer-Aided Engineering Allows for Future Modification Computer-aided engineering (CAE) allows the performance of structures subjected to static or fluctuating loads and various temperatures to be simulated, analyzed, and tested efficiently, accurately, and more quickly than ever. The information developed can be stored, retrieved, displayed, printed, and transferred anywhere in the organization.Fiberglass Chassis for a Lotus Car Being Removed from the Mold. (Lotus Cars Ltd. /Dorling Kindersley.)
7Computer-Aided Engineering Links All Phases of Manufacturing Computer-aided manufacturing (CAM) involves all phases of manufacturing byutilizing and processing further the large amount of information on materials andprocesses collected and stored in the organization’s database. Computers now assistmanufacturing engineers and others in organizing tasks such as programmingnumerical control of machines; programming robots for materials handling andassembly; designing tools, dies, and fixtures; and maintaining quality control.Car Frames Being Weldedon a Robotic Assembly Line. (Courtesy of Adam Lubroth / Stone/Getty Images Inc.)
8RAPID PROTOTYPINGRapid prototyping systems allow the engineer to develop a prototype directly from a CAD design within minutes orhours instead of the days or weeks it might otherwise take to create a prototype part.(Courtesy of Stratasys, Inc.)SLA Rapid Prototyping System. (Courtesy of 3D SystemsCorporation.)
10TYPES OF RAPID PROTOTYPING SYSTEMS Stereolithography Apparatus (SLA)Solid Ground Curing (SGC)Selective Laser Sintering (SLS)Fused Deposition Modeling (FDM)Laminated Object Manufacturing (LOM)Topographic Shell Fabrication (TSF)3D PrintingRapid ToolingDirect Shell Production Casting (DSPC)3D Printer Model. (Courtesy of Z Corporation.)
11DESIGN FOR MANUFACTURE, ASSEMBLY, DISASSEMBLY, AND SERVICE This area is termed design for manufacture (DFM). DFM is a comprehensiveapproach to producing goods and integrating the design process with materials, manufacturing methods, process planning, assembly, testing, and quality assurance.(Courtesy of the New York Times.)
13PROPERTIES OF MATERIALS Manufacturing properties of materials determine whether they can be cast, formed, machined, welded, and heat treated with relative easeGeneral Manufacturing Characteristics of Various AlloysMethods used to process materials to the desired shapes can adversely affect the product’s final properties, service life, and cost.
14COST AND AVAILABILITY OF MATERIALS APPEARANCE, SERVICE LIFE, AND RECYCLING Cost and availability of raw and processed materials and manufactured components are major concerns in manufacturing. Competitively, the economic aspects of material selection are as important as the technological considerations of properties and characteristics of materials.The appearance of materials after they have been manufactured into products influences their appeal to the consumer.Time- and service-dependent phenomena such as wear, fatigue, creep, and dimensional stability are important.Recycling or proper disposal of materials at the end of their useful service lives has become increasingly important in an age when we are more conscious of preserving resourcesand maintaining a clean and healthy environment.
15MANUFACTURING PROCESSES There is usually more than one way to manufacture a part from a given material.
16Processing MethodsThe broad categories of processing methods for materials are:CastingForming and ShapingMachiningJoiningFinishingSelecting a particular manufacturing process, or a series of processes, depends not only on the shape to be produced but also on many other factors pertaining to material properties.
17DIMENSIONAL ACCURACY AND SURFACE FINISH Ultraprecision manufacturing techniques and machinery are now being developed and are coming into more common use. For machining mirrorlike surfaces, for example, the cutting tool is a very sharp diamond tip, and the equipment hasvery high stiffness and must be operated in a room where the temperature is controlled within 1°C. Highly sophisticated techniques such as molecular-beam epitaxy and scanningtunneling microscopy are being implemented to obtain accuracies on the order of the atomic lattice 0.1 nm.
18MEASURING DEVICES USED IN MANUFACTURING Although the machinist uses variousmeasuring devices depending on the kindof dimensions (fractional, decimal, or metric) shown on the drawing, to dimension correctly, the engineering designer must have a working knowledge of common measuring tools.Most measuring devices in manufacturing are adjustable so they can be used for a range of measurements, but some measuring devices are designed to be used for only one particular dimension.
19OPERATIONAL AND MANUFACTURING COSTS The design and cost of tooling, the lead time required to begin production, andthe effect of workpiece material on tool and die life are major considerations.Depending on its size, shape, and expected life, the cost of tooling can be substantial. For example, a set of steel dies for stamping sheet metal fenders for automobiles may cost about $2 million.quantity of partsscrap rateAvailability of machines and equipmentsafety
20COMPUTER-INTEGRATED MANUFACTURING Few developments in the history of manufacturing have had a more significant impact than computers.Computer numerical control (CNC)Adaptive control (AC)Industrial robotsAutomated handling of materialsAutomated and robotic assemblyComputer-aided process planning (CAPP)Group technology (GT)Just-in-time (JIT)Cellular manufacturingFlexible manufacturing systems (FMS)Expert systemsArtificial intelligence (AI)
21MANUFACTURING METHODS AND THE DRAWING In designing a part, consider what materials and manufacturing processes are to be used. These processes will determine the representation of the detailed features of the part, the choice of dimensions, and the machining or processing accuracy. Theprincipal methods of metal forming are:• Casting• Machining from standard stock• Welding• Forming from sheet stock• ForgingForgedCasted or Forged
23OBJECTIVES1. Use conventional dimensioning techniques to describe size andshape accurately on an engineering drawing.2. Create and read a drawing at a specified scale.3. Correctly place dimension lines, extension lines, angles, and notes.4. Dimension circles, arcs, and inclined surfaces.5. Apply finish symbols and notes to a drawing.6. Dimension contours.7. Use standard practices for dimensioning prisms, cylinders, holes,and curves.8. List practices for dimensioning a solid model as documentation.9. Identify guidelines for the dos and don’ts of dimensioning.
24UNDERSTANDING DIMENSIONING The increasing need for precision manufacturing and interchangeabilityhas shifted responsibility for size control to the design engineer or detail drafter.Practices for dimensioning architecturaland structural drawings are similarin many ways to those for dimensioningmanufactured parts, but some practicesdiffer.Refer to the following standards:• ANSI/ASME Y Dimensioning and Tolerancing• ASME Y Digital Product definition Data Practices• ASME B (R1999) Preferred Metric Limits and FitsAutomatically Generated Dimensions. Views and dimensions can be generated automatically from a solid model. (Courtesy of Robert Kincaid.)
25Three Aspects of Good Dimensioning Technique of dimensioningPlacement of dimensionsChoice of dimensions
26UNLESS OTHERWISE NOTED. ToleranceTolerance is the total amount that the feature on the actual part is allowedto vary from what is specified by the drawing or model dimension.ALL TOLERANCES ±.02 INCHUNLESS OTHERWISE NOTED.EXAMPLSA Title Block Specifying Tolerances. (Courtesy of Dynojet Research, Inc.)
27Geometric BreakdownEngineering structures are composed largely of simple geometric shapes, such as the prism, cylinder, pyramid, cone, and sphere. They may be exterior (positive) or interior (negative) forms.
28LINES USED IN DIMENSIONING Dimension, Extension and Centerlines
29ARROWHEADSWhen you are drawing by hand and using the arrowhead method in which both strokes are directed toward the point, it is easier to make the strokes toward yourself.
30LEADERSA leader is a thin, solid line directing attention to a note or dimension and starting with an arrowhead or dot.For the Best Appearance, Make Leaders• near each other and parallel• across as few lines as possibleDon’t Make Leaders• parallel to nearby lines of the drawing• through a corner of the view• across each other• longer than needed• horizontal or vertical
31DRAWING SCALE AND DIMENSIONING Drawing scale is noted in the title block. The drawing should not be scaled for dimensions. (Courtesy of Dynojet Research, Inc.)Many standard title blocks include a note such as:DO NOT SCALE DRAWINGFOR DIMENSIONS
32DIRECTION OF DIMENSION VALUES AND NOTES All dimension values and notes are lettered horizontally to be read from the bottom of the sheet, as oriented by the title block.
33DIMENSION UNITSA note stating ALL MEASUREMENTS IN MILLIMETERS or ALL MEASUREMENTS IN INCHES UNLESS OTHERWISE NOTED is used in the title block to indicate the measurement units…(Courtesy of Dynojet Research, Inc.)
34MILLIMETER VALUESThe millimeter is the commonly used unit for most metric engineering drawings. One-place millimeter decimals are used when tolerance limits permit. Two (or more)–place millimeter decimals are used when higher tolerances are required.
35DECIMAL-INCH VALUESTwo-place inch decimals are typical when tolerance limits permit. Three or more decimal places are used for tolerance limits in the thousandths of an inch. In two-place decimals, the second place preferably should be an even digit.
36RULES FOR DIMENSION VALUES Good hand-lettering is important for dimension values on sketches. The shop produces according to the directions on the drawing so to save time and prevent costly mistakes, make all lettering perfectly legible.Make all decimal points bold, allowing ample space. When the metric dimension is a whole number, do not show either a decimal point or a zero. When the metric dimension is less than 1 mm, a zero precedes the decimal point.When the decimal-inch dimension is used on drawings, a zero is not used before the decimal point of values less than 1 in.
37DUAL DIMENSIONING and COMBINATION UNITS Dual dimensioning is used to show metric and decimal-inch dimensions on the same drawing. Two methods of displaying the dual dimensions are:Position MethodBracket MethodDIMENSIONS IN () ARE MILLIMETERS
38Form and Proportion of Dimensioning Symbols. DIMENSION SYMBOLSDimensioning symbols are used to replace traditional terms or abbreviations.Form and Proportion of Dimensioning Symbols.(Reprinted from ASME Y14.5M-1994 (R2004),by permission of The American Society of Mechanical Engineers. All rights reserved.)
39PLACING AND SHOWING DIMENSIONS LEGIBLY Rules for the placement of dimensions help you dimension your drawings so that they are clear and readable…Fitting Dimension Values in Limited Spaces (Metric Dimensions)
40SUPERFLUOUS DIMENSIONS All necessary dimensions must be shown, but do not give unnecessary or superfluous dimensions.