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    INTRODUCTION TOCOMPUTER AIDED DRAFTING AND DESIGN

    (CADD)

    Rico C. Asuncion

    JANUARY 2011

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    LESSON 1. STEPPING INTO AUTOCAD

    A. Start-up Dialog Box ( available up to version 2006 )Specifies whether to open a drawing or start a new drawing using various

    methods:

    1. Open a Drawing: Opens an existing drawing. You can choose from thefour most recently opened drawings, or browse for any file. This option isnot available when you access this dialog box from the NEW command.

    2. Start from Scratch: Creates a new drawing using either English or metricdefault settings.

    3. Use a Template: Creates a new drawing using the settings defined in atemplate drawing you select. Drawing template files have a .dwt fileextension.

    4. Use a Wizard: Creates a new drawing using the settings you specify ineither the Quick or Advanced wizard.

    B. Understanding the AUTOCAD Window User Interface (2008)

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    1. Title Bar2. Pulldown Menu3. Standard Toolbar4. Object Property Toolbar

    5. Other Toolbars6. Crosshair7. UCS (User Coordinate System) icon8. Model and Layout Tabs9. Command Window10. Status Bar

    a. Snap (F9)b. Grid (F7)c. Ortho (F8)d. Polar (F10)e. Osnap (F3)

    f. Otrack (F11)g. Lwth. Modeli. Dyn (F12)

    C. Function Keys

    F1 - HelpF2 - Switches between Graphics and Text ScreenF3 - Turns Osnap On/OffF4 - Turns Tablet On/OffF5 - Cycles to Top, Right and Left IsoplanesF6 - Turns Coordinates On/OffF7 - Turns Grid On/OffF8 - Turns Ortho On/OffF9 - Turns Snap On/OffF10 - Turns Polar On/OffF11 - Object Snap Tracking On/ OffF12 - Turns Dynamic Input On/ Off (starts in version 2006)

    D. Using Button Functions of the Mouse

    The first 10 pointing device buttons are automatically assigned; you canreassign all except button 1, the pick button.1. Two-button Mouse

    1. Left button is the pick button used to

    Specify locations

    Select objects for editing

    Choose menu options and dialog box buttons and fields2. Right button on a mouse depends on context; it can be used to

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    End a command in progress

    Display a shortcut menu

    Display the Object Snap menu

    Display the Toolbars dialog box Right-click operation can be modified in the Options dialog box.

    The operation of additional buttons on a pointing device isdefined in the menu file.

    2. The Wheel MouseThe wheel mouse has a small wheel between the buttons. The left

    and right buttons behave the same as they do on a standard mouse.You can rotate the wheel by discrete values. You can use the wheelto zoom and pan in your drawing without using any commands.

    By default, the zoom factor is set to 10 percent; each increment inthe wheel rotation changes the zoom level by 10 percent. TheZOOMFACTOR system variable controls the incremental change,whether forward or backward. The higher the number, the larger the

    change.The following table lists the wheel mouse actions supported in thisprogram.

    To... Do this...

    Zoom in or outRotate the wheel forward to zoom in,

    backward to zoom outZoom to drawing extents Double-click the wheel button

    PanHold down the wheel button and drag the

    mouse

    Pan (joystick)Hold down CTRL and the wheel button, and

    drag the mouseDisplay the Object Snap

    menuWith the MBUTTONPAN system variable set

    to 0, click the wheel button

    E. Drawing Area Preparation

    1. LIMITS - Sets and controls the limits of the drawing boundaries andgrid display in the current Model or layout tab The drawing limits aretwo-dimensional points in the world coordinate system that representthe lower-left and upper-right boundaries. You cannot impose limits onthe Zdirection.

    2. GRIDs, SNap, ORTHO - Specifies drafting settings organized fordrawing aids in three categories: Snap and Grid, Polar Tracking, andObject SNAP

    3. UNits - Defines the unit and angle formats.

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    Onscreen paper size can be presented using the following: Grid Extents - use LIMITS command to modify grid extent Bounding Objects - paper can be represented by a rectangle,

    corner pts., line, etc.

    Limits for 11 x 8.5 paper (letter size) at 1:100 scaleConvert inches to meter

    11 * 2.54 = 27.948.5 * 2.54 = 21.59

    F. AutoCAD Coordinate System

    1. You can use Cartesian (Rectangular) Coordinates to locate pointswhen creating objects.

    To use Cartesian coordinates to specify a point, enter anXvalue and aY value separated by a comma (X,Y). The X value is the positive or

    negative distance, in units, along the horizontal axis. The Y value is thepositive or negative distance, in units, along the vertical axis.

    a. Absolute Cartesian coordinates are based on the UCS origin(0,0), which is the intersection of the X and Y axes. Use absolutecoordinates when you know the preciseXand Yvalues of the point.

    With dynamic input, you can specify absolute coordinates with the #prefix. If you enter coordinates on the command line instead of in thetooltip, the #prefix is not used. For example, entering #3,4specifies apoint 3 units along the X axis and 4 units along the Y axis from theUCS origin.

    The following example draws a line beginning at an Xvalue of -2, a

    Yvalue of 1, and an endpoint at 3,4. Enter the following in the tooltip:Command: lineFrom point: -2,1To point: 3,4

    The line is located as follows:

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    b. To specify Relative Cartesian coordinates, precede thecoordinate values with an @ sign. For example, entering @3,4specifies a point 3 units along the Xaxis and 4 units along the Yaxis

    from the last point specified.The following example draws the sides of a triangle. The first side isa line starting at the absolute coordinates -2,1 and ending at a point 5units in theXdirection and 0 units in the Ydirection. The second sideis a line starting at the endpoint of the first line and ending at a point 0units in the X direction and 3 units in the Y direction. The final linesegment uses relative coordinates to return to the starting point.

    Command: lineFrom point: -2,1To point: @5,0To point: @0,3

    To point: @-5,-3

    2. You can usePolar Coordinates(distance and angle) to locate pointswhen creating objects.

    To use polar coordinates to specify a point, enter a distance and anangle separated by an angle bracket (

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    a. Absolute Polar coordinates are measured from the UCS origin(0,0), which is the intersection of the X and Y axes. Use absolutepolar coordinates when you know the precise distance and anglecoordinates of the point.

    With dynamic input, you can specify absolute coordinates with the #prefix. If you enter coordinates on the command line instead of in thetooltip, the #prefix is not used. For example, entering #3

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    b. Relative Polar coordinates are based on the last point entered.Use relative coordinates when you know the location of a point inrelation to the previous point.

    To specify relative coordinates, precede the coordinate values withan @ sign. For example, entering @1

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    3. Direct Distance EntryYou can specify a point by moving the cursor to indicate a direction

    and then entering the distance.To specify a line length quickly, without entering coordinate values,

    you can specify a point by moving the cursor to indicate a direction

    and then entering the distance from the first point. You can entercalculated distances from the QuickCalc calculator.You can use direct distance entry to specify points for all

    commands requiring more than one point. When Ortho mode or polartracking is on, this method is an efficient way to draw lines of specifiedlength and direction, and to move or copy objects.

    Note: The direct distance entry method is not available while youare using the temporary override keys for Ortho mode, object snaptracking, or polar tracking.

    4. PolarSnaprestricts cursor movement to increments of a polar distance

    you specify. For example, if you specify a length of 4 units, the cursorsnaps from the first point specified to lengths of 0, 4, 8, 12, 16, and soon. As you move your cursor, a tooltip indicates the nearest PolarSnapincrement. To restrict point entry to polar distances, both polar trackingand Snap mode must be on. You can turn off all snapping and trackingtemporarily by using an override key.

    G. AUTOCAD Selection Methods

    1. Last - Selects the most recently created visible object.2. Using Pick box - A small box, called the object selection target,

    replaces the crosshairs on the graphics cursor. You can select objectsindividually with the pointing device.

    3. Using Window - Select all objects completely inside a rectangledefined by two points. Specifying the corners from left to right create awindow selection.

    4. Using Crossing - Selects objects within and crossing an area definedby points. A crossing selection is displayed as dashed lines orotherwise highlighted to differentiate it from window selection.Specifying the corners from right to left creates a crossing selection.

    5. All- Selec