7 Computer-Aided Drafting and Design

Permission granted to reproduce for educational use only. © Goodheart-Willcox Co., Inc. Explain how computer technology is revolutionizing drafting, design, and engineering. Describe the basic features and operation of a computer-aided drafting program. Explain the various commands used to create objects in CAD.

Permission granted to reproduce for educational use only. © Goodheart-Willcox Co., Inc. Describe the tools used to modify CAD drawings. Identify the various display functions used in CAD programs. Describe the typical components in a CAD program Help system.

Permission granted to reproduce for educational use only. © Goodheart-Willcox Co., Inc. Explain the importance of CAD file management and identify common storage techniques. List different types of CAD software and their applications.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Benefits of CAD Simplifies traditional drafting tasks –Drawing basic shapes –Lettering –Creating views Maximizes accuracy and proficiency –Setup tools –Drawing and editing commands –Customization methods

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Computer Graphics and CAD First used for aerospace design in 1950s Prior to emergence of CAD, design work consisted of 2D drawing production and modelmaking CAD introduces many benefits –Eliminates repetitive tasks –Allows more time for creative work –Simplifies process of making 2D and 3D designs

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Traditional Drafting and CAD Principles of drafting are fundamental to both methods Knowledge of standards, techniques, and procedures is essential to using CAD effectively

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Computer Graphics Programs Classified according to types of images created –Vector objectsVector objects –Raster objectsRaster objects

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Vector Objects Created in CAD drawings Made up of lines and arcs Defined with point coordinates in space Hard copy images may be converted to raster format with a scannerscanner

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Raster Objects Also called bitmap graphics Number of pixels defines resolutionresolution Modified using an image editing program

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Vector and Raster Images

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. How CAD Works Create CAD model in 2D or 3D form Use commands to give program instructions Modify objects with editing and modifying commands Add dimensions and text Output drawing to plotter or printer

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Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. File Management Commands New Open Close Save Save as

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Exporting Files Typically done with the Export command Used to create files in a different format –Windows Metafile (WMF) –Bitmap (BMP) –Stereolithography (STL) –Portable Document Format (PDF)

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Plotting and Distribution Commands Page setup –Used to specify plot device and layout settings Plot –Used to configure plot device and select type of media Publish –Used to “publish” multiple-sheet drawing sets

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Basic CAD System Functions Coordinate systems Drawing aids Layers and linetypes Blocks

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Coordinate Systems Used to define coordinates coordinates World coordinate system is most basic systemWorld coordinate system –Based on Cartesian coordinate systemCartesian coordinate system

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Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Coordinate Entry Methods Absolute coordinates Relative coordinates Polar coordinates

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Absolute Coordinates

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Relative Coordinates

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Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. User Coordinate System Useful for creating drawings in 3D Orients drawing plane to specific surface Coordinates are located on drawing plane relative to fixed origin (point on object) Simplifies 3D drawing process

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Drawing Aids Grid Snap Object snap Orthogonal mode

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Layers Used to organize drawing content Named to reflect content –Layer naming conventions observe company or school standards Similar to overlays used in manual drafting Assigned colors Assigned linetypeslinetypes Specified in a drawing template

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Blocks Typically created for commonly used symbols –Windows and doors on architectural plans Used to save drafting time Inserted into drawings as needed Typically stored in a symbol librarysymbol library May be saved with attributes for use in creating a scheduleattributesschedule

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Drawing Setup Functions Specify drawing unit format Determine drawing scale and sheet size Create layers Save common user settings in a templatetemplate

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Object Drawing Commands Line Circle Arc Ellipse Polygon

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Drawing Lines Line command typically used Requires two coordinates –More coordinates may be added within single command sequence Use proper linetype –Set appropriate layer current before drawing

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Drawing Circles Circle command typically used Use appropriate method –Specify center point and radius or diameter –Specify points along perimeter of circle –Enter radius and select two lines or two circles to which circle should be tangent

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Drawing Arcs Arc command typically used Use appropriate method –Specify center point, radius, and endpoint –Specify three points along arc –Specify start point, center point, and chord length

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Drawing Ellipses Ellipse command typically used –Specify center point, major axis, and minor axis Elliptical arcs drawn in similar fashion –Specify axis endpoints and start and end angles

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Drawing Polygons Polygon command typically used –Enter number of sides –Specify center point –Inscribe or circumscribe the polygon –Enter radius

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Editing and Modifying Commands Move Copy Rotate Scale Undo Erase Array Mirror Fillet Trim Extend

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Moving Objects Move command typically used –Select object or objects to move –Specify base point for selection set –Specify displacement point

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Copying Objects Copy command typically used –Select object or objects to copy –Select base point –Specify displacement point –Multiple option copies same selection to more than one location

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Rotating Objects Rotate command typically used –Used to change angular position of object –Select object or objects to rotate –Specify base point –Specify angle (clockwise or counterclockwise)

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Scaling Objects Scale command typically used –Used to reduce or enlarge objects by specified scale factor –Select object to scale –Select base point –Specify scale factor

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Undoing Operations Undo command typically used –Used to “undo” previous action –Allows for undoing multiple actions in reverse sequence

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Erasing Objects Erase command typically used –Used to remove unwanted objects quickly –Select objects to erase –Use Undo command to restore erased object

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Arraying Objects Array command typically usedArray –Used to copy and orient multiple objects in a pattern Use rectangular array for rectangular orientation –Enter base point, number of rows, number of columns, and spacing Use polar array for polar orientation –Specify center point, number of objects, and angular value determining amount of rotation

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Mirroring Objects Mirror command typically used –Used to create symmetrical objects by creating mirrored copy of object –Select object to mirror –Specify mirror axis –Keep or delete original object

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Creating Rounded Corners Fillet command typically used –Used to create round or filletroundfillet –Set radius –Select entities forming intersection

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Creating Angled Corners Chamfer command typically used –Used to create chamferchamfer –Set chamfer distance –Select two lines

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Trimming Lines Trim command typically used –Used to clean up line overlaps –Specify cutting edge –Select object to trim

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Extending Lines Extend command typically used –Used to lengthen object to meet edge –Specify boundary –Select object to extend

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Display Commands Zoom command –Used to zoom in (to view drawing details) or zoom out (to reduce the view) Pan command –Used to adjust view in real time without changing magnification More advanced commands available in 3D drawing programs

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Making Measurements Measure Geometry command typically used to calculate common measurements –Linear distances Select two points –Area and perimeter calculations Select object or pick points defining the area

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Object Property and Drawing Status Commands Properties command –Used to identify object coordinates and settings assigned to object List command –Used to list information from drawing database Status command –Used to identify drawing statistics Time command –Used to identify current time and drawing time in current session

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Help System Provides user help Accessed with Help command Organized into documents and references Includes search functions and question-and- answer tools

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. File Management and Storage Establish a logical system of folders to organize files in a project Use established file naming conventions –Use prefixes to identify project and drawing information Follow school or company practice

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Backing Up and Archiving Files Save and back up work at regular intervals Follow established protocol –Save work every 15 minutes –Save to a network server –Back up files on a weekly basis Create file archive during project wrapup –Ensure that files can be accessed in future –Use standard naming, organization, and backup practices

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. CAD System Components Computer Monitor Keyboard Pointing device Output device Software

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. CAD Software Type used depends on specific application –2D drawing –3D modeling –Mechanical drafting and manufacturing –Advanced rendering and animation

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. CAD Modeling Programs Used to construct 3D models Classified by modeling method –Solid modelingSolid modeling –Surface modelingSurface modeling –Parametric modelingParametric modeling Often provide rendering capabilityrendering

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Solid Modeling (Designed with Solid Edge from Siemens PLM Software)

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Surface Modeling (Discreet, a division of Autodesk)

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Parametric Modeling Allows modification of parameters during construction Used for assembly modeling in mechanical drafting and engineering applicationsassembly (Designed with Solid Edge from Siemens PLM Software)

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Computer-Aided Design/Computer- Aided Manufacturing (CAD/CAM) Computer numerical control (CNC) machines control manufacturing processes Computer data input to machine controls movement of machine tools CAD-generated drawings supply tool data

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Rendering Program Used to create realistic displays of models with special effects –Lighting –Materials –Environmental settings Requires greater computing power to perform necessary calculations

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Animation Program Used to assign movement parameters for frame- by-frame animations Used for higher-end applications –Architectural building tours –Film special effects –Medical imaging

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. What are coordinates? Points representing units of real measurement from a fixed point.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. When using relative coordinates, objects are drawn using coordinates in relation to the _____. last coordinate specified

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. How does orthogonal mode simplify the task of drawing horizontal and vertical lines? The movement of the cursor is confined to horizontal and vertical movement in relation to the drawing plane.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. What are layers? Layers are user-defined object settings that can be displayed or “turned off” to distinguish the different types of content in a drawing.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. An ellipse has a center point, a(n) _____ axis, and a(n) _____ axis. major, minor

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. What two types of arrays can be created with the Array command? Rectangular and polar arrays

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. The Mirror command is useful when drawing _____ objects. symmetrical

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. The _____ command can be used to restore an object that has been erased unintentionally. Undo

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Which of the following is not an object drawing command? A. Line B. Properties C. Circle D. Arc B. Properties

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Name the three most common types of CAD modeling. Solid modeling, surface modeling, and parametric modeling

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. What is parametric modeling? An advanced form of modeling that allows object dimensions, or parameters, to be modified during the construction of a model.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. How does CAD/CAM combine CAD with automated manufacturing operations? After a part is drawn in a CAD program, the design data is calculated by the program. The computer data is input to the CNC machine to control the movement of machine tools.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Absolute coordinates –Coordinates located in relation to the coordinate system origin (0,0,0). Array –An orientation of copied objects in a rectangular or polar pattern. Assembly –A functional mechanism made up of multiple components, referred to as parts. Attributes –Text strings of information about related block symbols, such as product numbers, sizes, or materials.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Blocks –Predrawn objects designed for multiple use in drawing projects. Cartesian coordinate system –A system in which coordinate points are located using the X, Y, and Z axes. Chamfer –An angled cut made to remove the “corner” of two perpendicular surfaces.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Computer-aided design/computer-aided manufacturing (CAD/CAM) –A type of manufacturing in which machining data is generated from CAD drawings and used by computer numerical control (CNC) machines. Coordinates –The positions or locations of points along the X, Y, and Z axes. In a CAD system, the points represent units of real measurement from a fixed point. Fillet –An arc representing an inside rounded corner.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Grid –A network of uniformly spaced points used to determine distances. Layers –User-defined object settings that can be displayed or “turned off” to distinguish the different types of content in a drawing. Linetype –A user-defined object setting used to describe a line definition in the Alphabet of Lines. Object snap –A function that allows the cursor to be “snapped” to specific locations on an object.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Orthogonal mode –A drawing mode used to draw horizontal and vertical lines by confining the cursor to horizontal and vertical movement. Parametric modeling –A type of 3D-based drawing in which changes to object parameters during the modeling process affect the entire model. Pixels –Tiny shapes of data making up a raster image. Also called picture elements. Polar coordinates –Coordinates located at a given distance and angle.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Raster objects –Objects made up of pixels. Also known as bitmap graphics. Relative coordinates –Coordinates located in relation to the last point specified (or the origin, if a previous point has not been specified). Rendering –A highly realistic representation of a model with lighting, shadows, and other visual effects applied.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Resolution –A term used to describe the visual quality of a raster image, determined by the number of pixels making up the image. Round –An arc representing an outside rounded corner. See also Fillet. Scanner –A computer hardware device used to convert a hard copy image into digital form.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Schedule –A chart or table used to list manufacturing and purchasing information about parts and products on a drawing. Snap –A function that allows the user to align or “snap” the cursor to specific increments in an invisible grid. Solid modeling –A type of 3D-based drawing used to create solids (objects that represent the entire mass of an object).

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Surface modeling –A type of 3D-based drawing used to create surface models (objects that have an outer “skin” to represent exterior surfaces). Symbol library –A collection of related drawing symbols. Template –A saved set of configurations used to start a drawing file.

Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. User coordinate system –A relative drawing configuration enabling the user to orient a drawing plane to a specific surface, typically used in 3D drawing. Vector objects –Objects made up of lines and arcs, defined with point coordinates in space. World coordinate system –A system for locating points using Cartesian coordinates on the XYZ axes in relation to the 0,0,0 origin.