Autocad 2002

AutoCAD 2002 UMaT, Tka

John Annan CAD 1

CHAPTER ONE

AUTOCAD 2002

1.1 AUTOCAD 2002 ENVIRONMENT

Figure 1.1 shows a typical environment for autocad 2002. The main areas to consider are the model

space and the command window. A lot of toolbars together with a wide variety of commands are

available for designing in the model space.

AutoCAD operates in either Model space or Paper space. You use model space (the Model tab) to do

drafting and design work and to create two-dimensional drawings or three-dimensional models. You use

paper space (a layout tab) to create a finished layout of a drawing for plotting. When you are in a layout,

you can enter mspace on the command line to make the last viewport in the layout current, and then

work in model space in that viewport within the layout. You can switch to model space by double-

clicking a viewport, and you can switch to paper space by double-clicking an area of paper space.

1.1.1 Toolbars Toolbars contain buttons that start commands. When you move the pointing device over a toolbar

button, the tooltip displays the name of the button. Buttons with a small black triangle in the lower-right

corner have flyouts that contain related commands. With the cursor over the icon, hold down the pick

button until the flyout appears. Release the pick button on a preferred flyout option. The Standard

toolbar at the top of the drawing area is displayed by default. This toolbar is similar to those found in

Microsoft Office programs. It contains frequently used AutoCAD commands such as DIST, PAN, and

ZOOM, as well as Microsoft Office standard commands such as New, Open, and Save.

Floating toolbar

Docked toolbars

Crosshairs

Pick box

Drawing Aids eg. SNAP, GRID, etc X, Y, Z.

Coordinate of pointer

Command window

UCS icon

Menu bar / Main menu

Model tab

Layout tab

Model space

Fig. 1.1 Typical Autocad Environment (Autocad 2002 Drawing Interface)

Object


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To display a toolbar

1. From the View menu, choose Toolbars.

2. In the Customize dialog box, Toolbars tab, select the name of the toolbar you want to show.

3. Choose Close.

Shortcut menu: You can also display a toolbar by right-clicking any toolbar button and choosing a

toolbar from the shortcut menu.

To dock a toolbar

1. Position the cursor on the name of the toolbar or in any blank area, and hold down the button

on your pointing device.

2. Drag the toolbar to a docking location at the top, bottom, or either side of the drawing area.

3. When the outline of the toolbar appears in the docking area, release the button.

To place a toolbar in a docking region without docking it, hold down CTRL as you drag.

To undock a toolbar

1. Position the cursor on the double bars at the end of the toolbar, and hold down the button on

your pointing device.

2. Drag the toolbar away from its docked location and release the button.

To resize a toolbar

1. Position the cursor on the edge of a floating toolbar until the cursor changes to a horizontal

or vertical double arrow.

2. Hold down the button and move the cursor until the toolbar is in the shape you want.

To close a toolbar

If the toolbar is docked, undock it Click Close button in upper-right corner of toolbar.

1.1.2 Command Window You can display commands, system variables, options, messages, and prompts in a dockable and

resizable window called the command window. To enter a command by using the keyboard, type the

full command name on the command line and press ENTER or SPACEBAR, or right-click your

pointing device. Some commands also have abbreviated names. For example, instead of entering circle

to start the CIRCLE command, you can enter c. Abbreviated command names are called command

aliases.

If you want to repeat a command that you have just used, press ENTER or SPACEBAR, or right-click

your pointing device at the Command prompt. You also can repeat a command by entering multiple, a

space, and the command name, as shown in the following example:

Command: multiple circle

To cancel a command in progress, press ESC.

To float the command window

Click any part of the border and drag the command window away from the docking

region until it has a thick outline. Then drop it in the drawing area of the AutoCAD window.

To dock the command window

Click the title bar, or an edge, and drag the command window until it is over the top or

bottom docking regions of the AutoCAD window.

To resize the command window when it is docked

1. Position the cursor over the horizontal splitter bar so that the cursor appears as a double

line and arrows.

2. Drag splitter bar vertically until command window is the size you want it to be.


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1.1.3 Basic Operations

A number of basic settings could be performed for model space. A few are discussed here.

1. Resizing of crosshairs

Tools options display tab under crosshair size, adjust slider

2. Resizing of pick box

Tools options selection tab under pickbox size, adjust slider

3. Displaying and disappearing of UCS icon

View display UCS icon click on

4. Colouring of command window

Tools options display tab click Colors command button for color options

Under window element, select command line background

Under color dialog box, select the appropriate color then click Apply & Close

Model tab background, model tab pointer, layout tabs background (paper), layout tabs

pointer, autotrack vector color, command line text and plot preview background could be

colored through the procedure above.

5. Changing of grip size and grip color

Tools options selection tab under grips, enable grips and chose appropriate

selected and unselected grip color

Grip size can also be changed using the grip size slider

6. To disable today startup dialog

Tools options system tab under general options, under startup:, make an

appropriate selection

Command aliases are shortcuts or alternative names for commands that you enter at the keyboard. This

appendix lists the command aliases provided in the standard acad.pgp file. You can change or delete

these aliases, or you can add some of your own by editing the acad.pgp file.

Command aliases

Commands Aliases Commands Aliases

ADCENTER (autocad design

centre) adc - LINETYPE -lt, -ltype

ARC a LIST li, ls

AREA (finding area) aa MIRROR mi

ARRAY ar MLINE (muti-line) ml

- ARRAY -ar MOVE m

BREAK br MTEXT t, mt

CHAMFER cha - MTEXT -t

CIRCLE c OFFSET o

COLOR col, colour, ddcolor OPTIONS ddgrips, gr, op, pr

COPY co, cp OSNAP ddosnap, os

DDEDIT ed - OSNAP -os

DIMALIGNED dal, dimali PAN p

DIMANGULAR dan, dimang - PAN -p

DIMBASELINE dba, dimbase PEDIT pe


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DIMDIAMETER ddi, dimdia PLINE pl

DIMEDIT ded, dimed POINT po

DIMLINEAR dli, dimlin POLYGON pol

DIMRADIUS dra, dimrad PROPERTIES ch, ddchprop, ddmodify,

mo, props

DIMTEDIT dimted RECTANG rec

DIST di REVOLVE rev

DONUT do ROTATE ro

ELLIPSE el SCALE sc

ERASE e SNAP sn

EXPLODE x SPLINE spl

EXTEND ex SPLINEDIT spe

EXTRUDE ext STRETCH s

FILLET f SUBTRACT su

GROUP g THICKNESS th

- GROUP -g TILEMODE ti, tm

HATCH -h TOOLBAR to

HATCHEDIT he TORUS tor

HIDE hi TRIM tr

INTERSECT in UNION uni

LEADER lead UNITS un, ddunits

LENGTHEN len - UNITS -un

LINE l WEDGE we

LINETYPE lt, ltype, ddltype ZOOM z

1.2 COORDINATE ENTRY

When a command prompts you for a point, you can use the pointing device to specify a point, or you

can enter a coordinate value on the command line. You can enter two-dimensional coordinates as either

Cartesian (X,Y) or polar coordinates.

1.2.1 Absolute Coordinate

Absolute coordinate makes reference to the origin of autocad imaginary axes. Like a graph paper, any

point you place in the command window using absolute coordinate syntax corresponds to an x-axis

value and y-axis value and z-axis value in the case of 3D plots.

To enter an absolute coordinate (2D)

At a prompt for a point, enter the coordinate using the following format: x,y

X represents the distance and direction along the horizontal axis from the origin (0,0).

Y represents the distance and direction along the vertical axis from the origin (0,0).


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1.2.2 Relative Coordinate

Relative coordinate always measured from the previous point that was entered. To apply relative

coordinate, a point must first be placed either by clicking or by absolute coordinate method. This point

will now serve as a reference point for relative coordinate point number 1. Point number 2 will use point

number 1 as the origin or reference point.

To enter a relative coordinate (2D)

At a prompt for a point, enter the coordinate using the following format: @x,y

X represents the distance and direction along the horizontal axis from the last point entered.

Y represents the distance and direction along the vertical axis from the last point entered.

1.2.3 Polar coordinates

To enter a polar coordinate, enter a distance and an angle separated by an angle bracket (<). For

example, to specify a point that is at a distance of 1 unit from the previous point and at an angle of 45

degrees, enter @1<45.

By default, angles increase in the counterclockwise direction and decrease in the clockwise direction.

To move clockwise, enter a negative value for the angle. For example, entering 1<315 is the same as

entering 1<-45. Polar coordinates are either absolute (measured from the origin) or relative to the

previous point. To specify a relative

coordinate, precede the coordinate with

an @ sign.

To enter a polar coordinate (2D)

At a prompt for a point, enter the

coordinate using the following format:

@distance<angle Distance represents the distance

from the origin.

Angle represents the angle from

the origin.

Example 1: Relative Coordinate Entry for Fig. 1.3

a. Select line command

Command: _line Specify first point: Click anywhere for start point

b. Using relative coordinate entry and moving in a clockwise direction

Specify next point or [Undo]: @0,30

Specify next point or [Undo]: @50,0

Specify next point or [Close/Undo]: @0,50

Fig. 1.3

Fig. 1.2


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Specify next point or [Close/Undo]: @-50,0



Specify next point or [Close/Undo]: @0,-20












Specify next point or [Close/Undo]:

Command:

Example 2: Relative Coordinate Entry for Fig. 1.4a

a. Figure 1.4a could best be drawn using the polyline command. Hence, select polyline command.

Command: _pline

Specify start point: Click to specify start point

Current line-width is 0.0000

Specify next point or [Arc/Halfwidth/Length/Undo/Width]: @0,20

b. Select arc from within polyline command. Specify also the direction of the arc where necessary.

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: a

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: d

Specify the tangent direction for the start point of arc: Ortho on: Click required direction (left)

Specify endpoint of the arc: @20,20

c. Switch back to line after drawing arc


[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: l

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @50,0


Fig. 1.4a Fig. 1.4b Polyline

Arc directions


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Specify the tangent direction for the start point of arc: Ortho on: Click required direction (top)

Specify endpoint of the arc: @20,-20



Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @0,-20

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @-20,-20




Specify the tangent direction for the start point of arc: Ortho on: Click required direction (down)

Specify endpoint of the arc: @-50,0



Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @-20,20

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:

Command:

in AutoCAD like all other forms of design requires planning: planning of starting,

processing, finishing and polishing up; planning of final display of design (of how

design will look like). In effect, a model is needed. Mental imaging (thinking about the purpose and

nature of design) and conceptualising (considering the possible solutions alongside constraints and

available resources) are the initial stages of modelling. The next stage is to sketch on paper calculating

all distances and angles of possible ideas so as to make the paper design a true representation of what is

to be expected. Drawing the object model space follows up in the next stage and all other forms of

finishing including rendering are the final stages of designing in AutoCAD.

1.3 DRAW TOOLBAR

The draw menu as well as the draw toolbar contains a lot of commands buttons used for drawing in the

command window.

1.3.1 Line

The line command, unlike polyline is disjointed. Where an object is drawn using line, individual

segments of the objects could be selected separately. You can either group them together using the

command; group or convert them to polyline using polyline edit (pedit join).

To draw lines

1. From the Draw menu, choose Line.

2. Specify the start point. Use the pointing device or enter a coordinate on the command line.

3. Complete the first line segment by specifying the endpoint. To undo the previous line segment

during the LINE command, enter u or choose Undo on the toolbar.

4. Specify the endpoints of any additional line segments.

5. Press ENTER to end or c to close a series of line segments.

To start a new line at the endpoint of the last line drawn, start the LINE command again and press

ENTER at the Specify Start Point prompt.

To draw a line using direct distance entry

1. Start the LINE command and specify the first point.

2. Move the pointing device until the rubber-band line extends at the same angle as the line you

want to draw.

3. Enter a distance on the command line to see the line drawn at the length and angle specified.

Designing


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1.3.2 Polyline

A polyline is a connected sequence of line segments created as a single object. You can create straight

line segments, arc segments, or a combination of the two.

Create Wide Polylines

You can draw polylines of various widths by using the Width and Halfwidth options. You can set the

width of individual segments and make them taper gradually from one width to another. These options

become available after you specify a starting point for the polyline.

The Width and Halfwidth options set the width of the next polyline segments you draw. Zero (0) width

produces a thin line. Widths greater than zero produce wide lines, which are filled if Fill mode is on and

outlined if Fill mode is off. The Halfwidth option sets width by specifying the distance from the center

of the wide polyline to an outside edge.

Taper

When you use the Width option, AutoCAD prompts for both a starting and an ending width. By

entering different values, you can taper the polyline. The starting and ending points of wide polyline

segments are in the center of the line. Intersections of adjacent wide segments are usually beveled.

However, AutoCAD does not bevel nontangent arc segments, acute angles, or segments that use a dash-

dot linetype.

1.3.3 Polygon

Polygons are closed polylines with between 3 and 1,024 equal-length sides. Creating polygons is a

simple way to draw squares, equilateral triangles, octagons, and so on.

There are many ways to create polygons:

Specifying the radius when you know the distance between the center of the polygon and the

endpoint of each side (inscribed)

Specifying the radius when you know the distance between the center of the polygon and the

midpoint of each side (circumscribed)

Specifying the length of an edge and where you want to place it

To draw a circumscribed or an inscribed polygon

1. From the Draw menu, choose Polygon.

2. On the command line, enter the number of sides.

3. Specify the center of the polygon (1).

4. Enter c to specify a polygon circumscribed about a circle or;

5. Enter i to specify a polygon inscribed within a circle of specified points.

6. Enter the radius length (2).

To draw a polygon by specifying one edge

1. From the Draw menu, choose Polygon.

2. On the command line, enter the number of sides.

3. Enter e (Edge) and specify the start point for one polygon segment.

4. Specify the endpoint of the polygon segment.

1.3.4 Arc

You can create arcs in several ways. With the exception of ‘specifying three points’ method, arcs are

drawn counterclockwise from the start point to the endpoint.

To draw an arc by specifying three points

1. From the Draw menu, choose Arc 3 Points.

2. Specify the start point.

3. Specify a point on the arc as well as the endpoint.

1.3.5 Circle

Fig. 1.5


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You can create circles in several ways. The default method is to specify the center and the radius.

AutoCAD provides several ways of drawing a circle.

To draw a circle by specifying a center point and radius or diameter

1. From the Draw menu, choose Circle Center, Radius or Center, Diameter.

2. Specify the center point.

3. Specify the radius or diameter.

To create a circle tangent to two objects

1. From the Draw menu, choose Circle Tan, Tan, Radius.

2. Select the first object to draw the circle tangent to.

3. Select the second object to draw the circle tangent to.

4. Specify the radius of the circle.

To draw an isometric circle

1. From the Tools menu, choose Drafting Settings.

2. On the Snap and Grid tab, under Snap Type and Style, turn on isometric snap and choose OK.

3. From the Draw menu, choose Ellipse Axis, End.

4. Enter i (Isocircle) and specify the center of the circle.

5. Specify the radius or diameter of the circle.

1.3.6 Spline

AutoCAD uses a particular type of spline known as a nonuniform rational B-spline (NURBS) curve. A

NURBS curve produces a smooth curve between control points. Splines are useful for creating

irregularly shaped curves, for example, drawing contour lines for geographic information system (GIS)

applications or automobile designs.

You create splines by specifying points. You can close the spline so that the start and endpoints are

coincident and tangent. Tolerance describes how closely the spline fits the set of fit points you specify.

The lower the tolerance, the more closely the spline fits the points. At zero tolerance, the spline passes

through the points. You can change the spline-fitting tolerance while drawing the spline to see the

effect.

To create a spline by specifying points

1. From the Draw menu, choose Spline.

2. Specify the start point for the spline (1).

3. Specify points (2 through 5) to create the spline,

and press ENTER.

4. Specify the start and end tangents (6, 7).

1.3.7 Elipse

The shape of an ellipse is determined by

two axes that define its length and width.

The longer axis is called the major axis,

and the shorter one is the minor axis.

To draw a true ellipse using endpoints and distance

Fig. 1.6

Fig. 1.7


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2. Specify the first endpoint of the first axis (1).

3. Specify the second endpoint of the first axis (2).

4. Drag the pointing device away from the midpoint, and click to specify a distance (3) for half the

length of the second axis.

To draw an elliptical arc using start and end angles

1. From the Draw menu, choose Ellipse Arc.

2. Specify endpoints for the first axis (1 and 2).

3. Specify a distance to define half the length of the second axis (3).

4. Specify the start angle (4).

5. Specify the end angle (5).

The ellipitical arc is drawn counterclockwise between the start point and endpoint.

1.3.9 Hatch

Many drafting applications use a process called hatching to fill an area with a pattern. The pattern is

used to differentiate components of a project or to signify the material composing an object. You can

use a predefined hatch pattern, define a simple line pattern using the current linetype, or create more

complex hatch patterns.

You can choose among several methods to specify the boundaries of a hatch, and you can control

whether the hatch automatically adjusts when the boundary changes (associative hatching).

To hatch areas

1. From the Draw menu, choose Hatch.

2. In the Boundary Hatch dialog box, choose

Pick Points.

3. In your drawing, specify a point inside each

area you want hatched and press ENTER.

This point is known as the internal point.

4. In the Boundary Hatch dialog box, Quick tab,

in the swatch box, verify that the sample

pattern is the pattern you want to use. To

change patterns, select another pattern from

the Pattern list. To see how the hatch pattern

will look, choose [...] next to Pattern. Choose

OK when you finish previewing.

5. In the Boundary Hatch dialog box, make

adjustments, if necessary. You can specify

new hatch boundaries by choosing Pick

Points.

6. In the Boundary Hatch dialog box, choose OK to create the hatch.

Specify one internal point per hatch block. Specifying more than one internal point can produce

unexpected results when you edit the hatch boundary.

To hatch selected objects

1. From the Draw menu, choose Hatch.

2. In the Boundary Hatch dialog box, choose Select Objects.

3. Select the object or objects you want to hatch. The objects need not form a closed boundary.

You can also specify any islands that should remain unhatched.

4. In the Boundary Hatch dialog box, choose OK to apply the hatch.

You can determine how islands, enclosed areas within the hatch boundary, are hatched using the three

hatching styles: Normal, Outer, and Ignore. You can preview these hatching styles in the Advanced

Options dialog box by selecting Preview.

Fig. 1.9 Boundary Hatch Dialogue Box


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Normal hatching style (the default) hatches inward from the outer boundary. If the hatching process

encounters an internal boundary, hatching is turned off until another boundary is encountered.

If you hatch using the Normal hatching style, islands remain unhatched and islands within islands are

hatched, as shown below.

Outer hatching style hatches inward from the outer boundary and stops at the next boundary. Ignore

hatching style hatches the entire enclosed area, ignoring internal boundaries.

1.4 MODIFY TOOLBAR

Various tools are available for the modification of objects. Among them include copy and mirror which

are explained below together with other forms of modify tools or commands.

1.4.1 Copy

To copy an object

1. From the Modify menu or modify toolbar, choose Copy.

2. Select the objects to copy and specify the base point.

3. Specify the second point of displacement.

To copy an object multiple times

1. From the Modify menu or toolbar, choose Copy.

2. Select the objects to copy, enter m (Multiple) and then specify the base point.

3. Specify the second point of displacement.

4. Specify the next point of displacement. Continue inserting copies, or press ENTER or ESC to

end the command.

1.4.2 Mirror

Mirroring creates a mirror image of objects. It is useful for creating symmetrical objects because you

can quickly draw half the object and then mirror it instead of drawing the entire object. You flip objects

about an axis called a mirror line to create a mirror image. To specify this temporary mirror line, you

enter two points. You can choose whether to delete or retain the original objects. Mirroring works in

any plane parallel to the XY plane of the current UCS.

When you mirror text, attributes, and attribute definitions, they are reversed or turned upside down in

the mirror image. To prevent this, set the MIRRTEXT system variable to 0 (off). Text then has the same

alignment and justification as before the mirroring. Compare the following illustrations.

By default, MIRRTEXT is on. This system variable affects text that is created with the TEXT,

ATTDEF, or MTEXT commands; attribute definitions; and variable attributes.

Fig.

1.10

Fig. 1.11 Mirrtext Settings


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Mirror in 3D

With MIRROR3D, you can mirror objects along a specified mirroring plane. The mirroring plane can

be one of the following:

The plane of a planar object

A plane parallel to the XY, YZ, or XZ plane of the current UCS that passes through a point you

select

A plane defined by three points that you select

To mirror objects

1. From the Modify menu, choose Mirror.

2. Select the objects to mirror.

3. Specify the first point of the mirror line.

4. Specify the second point.

5. Press ENTER to retain the original objects, or enter y to delete them

1.4.3 Offset

Offset creates a new object whose shape parallels the shape of a selected object. Offsetting a circle or an

arc creates a larger or smaller circle or arc, depending on which side you specify for the offset.

A highly effective drawing technique is to offset objects and then trim or extend their ends.

You can offset

To offset an object by specifying a distance

1. From the Modify menu, choose Offset.

2. Specify the offset distance. You can enter a value or use the pointing device.

3. Select the object to offset.

4. Specify a point on the side where you want to place the new objects.

5. Select another object to offset, or press ENTER to end the command.

1.4.4 Array

You can create copies of objects in a rectangular or polar (circular) pattern called an array. For

rectangular arrays, you control the number of rows and columns and

the distance between each. For polar arrays, you control the number of

copies of the object and whether the copies are rotated. To create

many regularly spaced objects, arraying is faster than copying.

To create a rectangular array

1. From the Modify menu, choose Array.

2. In the Array dialog box, choose Rectangular Array.

Lines

Arcs

Circles

Ellipses and elliptical arcs

2D polylines

Construction lines (xlines)

Rays

Splines

Original object

Object with

offset

Fig. 1.12 Offset Command Application


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3. Choose Select Objects. The Array dialog box closes and AutoCAD prompts for object selection.

4. Select the objects to be arrayed and press ENTER.

5. In the Rows and Columns boxes, enter the number of rows and columns in the array.

6. Specify the horizontal and vertical spacing (offsets) between objects by using one of the

following methods:

In the Row Offset and Column Offset boxes, enter the distance between rows and between

columns. Adding a plus sign (+) or a minus sign (-) determines direction.

Click the Pick Both Offsets button to use the pointing device to specify the diagonal corners of a

cell in the array. The cell determines the vertical and horizontal spacing of the rows and

columns.

Click the Pick Row Offset or Pick Column Offset button to use the pointing device to specify

the horizontal and vertical spacing. The example box displays the result.

7. To change the rotation angle of the array, enter the new angle next to Angle of Array.

8. The default angle 0 direction setting can also be changed in UNITS.

9. Choose OK to create the array.

To create a polar array

1. From the Modify menu, choose Array Polar Array.

2. Next to Center Point, do one of the following:

Enter an X value and a Y value for the center point of the polar

array.

Click the Pick Center Point button. The Array dialog box

closes and AutoCAD prompts for object selection. Use the

pointing device to specify the center point of the polar array.

3. Choose Select Objects. The Array dialog box closes and

AutoCAD prompts for object selection.

4. Select the objects to be arrayed.

5. In the Method box, select one of the following methods:

Total Number of Items & Angle to Fill

Total Number of Items & Angle Between Items

Angle to Fill & Angle Between Items

6. Enter the number of items (including the original object), if available.

7. Use one of the following methods:

Enter the angle to fill and angle between items, if available. Angle to Fill specifies the distance

to fill around the circumference of the array. Angle between Items specifies the distance

between each item.

Click the Pick Angle to Fill button and the Pick Angle Between Items button and use the

pointing device to specify the angle to fill and the angle between items. The example box

displays the result.

8. You can set any of the following options:

To rotate the objects as they are arrayed, select Rotate Items As Copied. The example area

displays the result.

To specify the X,Y base point, choose More, clear the Set to Object's Default option and enter

values in the X and Y boxes, or click the Pick Base Point button and use the pointing device to

specify the point.

9. Choose OK to create the array.

To create a 3D polar array of objects

1. From the Modify menu, choose 3D Operation 3D Array.

2. Select the object to array (1).

3. Specify Polar.

4. Enter the number of items to

array.

5. Specify the angle that the

arrayed objects are to fill.

Fig. 1.13 Rectangular Array Row offset=45, Column offset=70

Fig. 1.14 Polar Array Six objects; centre of rotation=35 units

fromarrow apex; rotate as coppied


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6. Press ENTER to rotate the objects as they are arrayed, or enter n to retain their orientation.

7. Specify the start point and endpoint of the axis about which objects are to be rotated (2 and 3).

1.4.5 Move

To move an object using two points

1. From the Modify menu, choose Move.

2. Select the objects to move.

3. Specify a base point for the move.

4. Specify a second point, the point of displacement.

The objects you selected are moved to a new location determined by the distance and direction between

the first and the second points.

To move an object using a displacement

1. From the Modify menu, choose Move.

2. Select the object to move.

3. Enter the displacement in the form of a Cartesian (absolute or relative) or polar value.

4. At the prompt for the second point of displacement, press ENTER.

By entering only one set of coordinate values, you instruct AutoCAD to use it as a relative displacement

rather than a base point. The objects you select are moved to a new location determined by the relative

coordinate values you enter.

1.4.6 Rotate

Rotate an Object by a Specified Angle

You rotate objects by choosing a base point and a relative or absolute rotation angle. Specify a relative

angle to rotate the object from its current orientation around the base point by that angle. Specify an

absolute angle to rotate the object from the current angle to a new absolute angle.

To rotate an object

1. From the Modify menu, choose Rotate and select the object to rotate.

2. Specify the base point for the rotation.

3. Do one of the following:

Enter the angle of rotation.

Drag the object around its base point and specify a point location to which you want to rotate the

object.

4. You can rotate an object by specifying a relative angle using one of two methods:

Enter a rotation angle value from 0 to 360 degrees. You can also enter values in radians, grads,

or surveyor bearings.

Drag the object around the base point and specify a second point. Turning on Ortho and Polar

Tracking, or using object snaps for the second point, is often useful with this method.

In this example, you rotate the plan view of a house by selecting the object (1), specifying a base

point (2), and specifying an angle of rotation by dragging to another point (3).

Rotate an Object to an Absolute Angle

Sometimes it is easier to rotate to an absolute angle with a reference option.

Fig. 1.15 3D Polar Array

Fig. 1.16a Rotation


John Annan CAD 15

In the following example, you specify the reference angle by selecting two points on the object to rotate.

You select the object to be rotated (1), specify the base point (2) by using the Midpoint object snap on

the window shown, and then use the Reference option to specify the angle of rotation. For the reference

angle, specify two points: the midpoint of the window (2) and the endpoint of the window (3). Rotate

the window by dragging it and specify the endpoint of the wall (4).

Rotate an Object in 3D

With ROTATE, you can rotate objects in 2D about a specified point. The direction of rotation is

determined by the current UCS. ROTATE3D rotates objects in 3D about a specified axis. You can

specify the axis of rotation using two points; an object; the X, Y, or Z axis; or the Z direction of the

current view. To rotate 3D objects, you can use either ROTATE or ROTATE3D.

1.4.7 Scale

Scale Objects

With scaling you can make an object larger or smaller, but you cannot alter its proportions. You can

scale it by specifying a base point and a length, which is used as a scale factor based on the current

drawing units, or by entering a scale factor. You can also specify the current length and a new length for

the object. Scaling changes the size of all dimensions of the selected object. A scale factor greater than 1

enlarges the object. A scale factor less than 1 shrinks the object.

To scale an object by a scale factor

1. From the Modify

menu, choose

Scale.

2. Select the object

to scale.

3. Specify the base

point.

4. Enter the scale

factor or drag and

click to specify a

new scale.

You can also scale by reference. Scaling by reference uses an existing measurement as a basis for the

new size. To scale by reference, specify the current measurement and then the new desired size. For

example, if one side of an object is 4.8 units long and you want to expand it to 7.5 units, use 4.8 as the

reference length.

You can use the Reference option to scale an entire drawing. For example, use this option when the

original drawing units need to be changed. Select all objects in the drawing. Then use Reference to

select two points and specify the intended distance. All the objects in the drawing are scaled

accordingly.

To scale an object by reference

1. From the Modify menu, choose Scale.

2. Select the object to scale and then select the base point.

Fig. 1.17 Scale Command Application


John Annan CAD 16

3. Enter r (Reference).

4. Select the first and second reference points, or enter a value for the reference length.

1.4.8 Stretch

Stretch Objects

To stretch an object, you specify a base point and then a point of displacement. Because stretching

moves the endpoints that lie within the crossing selection window, you must select the object with a

crossing selection. To stretch with greater accuracy, you can combine grip editing with object snaps,

grid snaps, and relative coordinate entry.

To stretch an object

1. From the Modify menu, choose Stretch.

2. Select the object using a crossing window selection. The crossing window must include at least

one vertex or endpoint. Specify a crossing window either by entering a c or by clicking, moving

your pointing device from right to left, and clicking again.

3. Do one of the following:

Enter the displacement in the form of a relative Cartesian, polar, cylindrical, or spherical

coordinate. Do not include the @ sign, because a relative coordinate is assumed. Press ENTER

at the prompt for the second point of displacement.

Specify the base point for the move, and then specify a second point, the point of displacement.

Any objects with at least one vertex or endpoint included within the crossing window are

stretched. Any objects that are completely within the crossing window are moved without

stretching.

1.4.9 Lengthen

Lengthen Objects

You can change the included angle of arcs and the length of some objects. You can change the length of

open lines, arcs, open polylines, elliptical arcs, and open splines. The results are similar to extending

and trimming. You can alter length in several ways:

Dragging an object endpoint (dynamically)

Specifying a new length or angle as a percentage of the total length or angle

Specifying an incremental length or angle measured from an endpoint

Specifying the object's total absolute length or included angle

1.4.10 Trim

To trim an object

1. From the Modify menu, choose Trim.

2. Select the objects to serve as cutting edges. To select all objects in the drawing as potential

cutting edges, press ENTER without selecting any objects.

3. Select the objects to trim.

Fig. 1.18 Stretch Command Application


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You can trim objects so that they end precisely at boundary edges defined by other objects. Cutting

edges can be lines, arcs, circles, polylines, ellipses, splines, blocks and rays. They can also be layout

viewport objects in paper space.

You can extend objects without leaving the TRIM command. Hold down SHIFT and select the objects

to be extended. You can trim objects to their nearest intersection with other objects. Instead of selecting

cutting edges, you press ENTER. Then, when you select the objects to trim, AutoCAD automatically

chooses the nearest objects in the drawing as cutting edges. In this example, the walls are trimmed so

that they intersect smoothly.

1.4.11 Extend

To extend an object

1. From the Modify menu, choose Extend.

2. Select the objects to serve as boundary edges. To select all objects in the drawing as potential

boundary edges, press ENTER without selecting any objects.

3. Select the objects to extend.

Extending operates the same way as trimming. You can extend objects so they end precisely at

boundary edges defined by other objects. In this example, you extend the lines precisely to a circle,

which is the boundary edge.

You can extend objects without leaving the TRIM command. Hold down SHIFT and select the objects

to be extended.

1.4.12 Break Using BREAK is a convenient way to create a gap in an object, resulting in two objects with a space

between them. BREAK is often used to create space for block or text insertion.

You can create breaks in

Arcs

Circles

Ellipses and elliptical

arcs

Fig. 1.19 Trim Command Application

Fig. 1.20 Extend

Command

Application


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Lines

Polylines

Rays

Splines

Xlines

When breaking an object, you can either

Select the object at the first break point and then specify a second break point

Select the entire object and then specify two break points

1.4.13 Chamfer

Using CHAMFER is a fast way of creating a line between two nonparallel lines. It is usually used to

represent a beveled edge on a corner. CHAMFER can also be used to bevel all corners of a polyline.

You can chamfer lines, polylines, xlines, and rays. With the distance method, you specify the amount

that each line should be trimmed or extended. With the angle method, you can also specify the length of

the chamfer and the angle it forms with the first line. You can retain the chamfered objects as they were

before the chamfer, or you can trim or extend them to the chamfer line.

To chamfer without trimming

1. From the Modify menu, choose Chamfer.

2. Enter t (Trim Control).

3. Enter n (No Trim).

4. Select the objects to chamfer.

To set chamfer distances


2. Enter d (Distances).

3. Enter the first chamfer distance.

4. Enter the second chamfer distance.

5. Select the lines for chamfering.

Chamfer by Specifying Distances

The chamfer distance is the amount

each object is trimmed or extended to

meet the chamfer line or to intersect

the other. If both chamfer distances

are 0, chamfering trims or extends

the two objects until they intersect

but does not create a chamfer line.

The default setting for the first

distance is the last distance specified. Because symmetrical distances are common, the default setting

for the second distance is whatever you chose for the first distance. However, you can reset the chamfer

distances. In this example, you set the chamfer distance to 0.5 for the first line and 0.25 for the second

line. After you specify the chamfer distance, you select the two lines as shown.

Chamfer by Specify Length and Angle

You can chamfer two objects by specifying where on the first selected object the chamfer line starts,

and then the angle the chamfer line forms with this object.

To chamfer by specifying chamfer length and angle


2. Enter a (Angle).

3. Enter the distance from the corner to be chamfered along the first line.

4. Enter the chamfer angle.

5. Select the first line. Then select the second line.

In this example, you chamfer two lines so that the chamfer line starts 1.5 units from the intersection

along the first line and forms an angle of 30 degrees with this line.

Fig. 1.21 Break Command Application

Fig. 1.22a Chamfer: Distances


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Chamfer an Entire Polyline

When you chamfer an entire polyline, each intersection

is chamfered. For best results, keep the first and second

chamfer distances equal.

To chamfer an entire polyline


2. Enter p (Polyline).

3. Select the polyline. The polyline is chamfered

using the current chamfer method and the

default distances.

When you chamfer an entire polyline, AutoCAD chamfers only the segments that are long enough to

accommodate the chamfer distance. The polyline in the following illustration has some segments too

short to be chamfered.

1.4.14 Fillet

Filleting connects two objects with a smoothly fitted arc of a specified radius. An inside corner is called

a fillet and an outside corner is called a round; you can create both using FILLET in AutoCAD.

You can fillet;

Using FILLET is also a convenient method of creating an arc with a specified radius that is tangent to

two selected objects. FILLET can be used to round all corners on a polyline using a single command.

If both objects being filleted are on the same layer, the fillet arc is created on that layer. Otherwise, the

fillet arc is created on the current layer. The layer affects object properties including color and linetype.

To set the fillet radius

1. From the Modify menu, choose Fillet.

2. Enter r (Radius).

3. Enter the fillet radius

4. Select the objects to fillet.

To fillet two line segments


Fig. 1.22b Chamfer: Length & Angle

Fig. 1.22c Chamfer: Entire Polyline

Fig. 1.22c Chamfer: Entire Polyline with Segments too Short to Chamfer

Arcs

Circles

Ellipses and elliptical arcs

Lines

Polylines

Rays

Splines

Xlines


John Annan CAD 20

2. Select the first line.

3. Select the second line.

To fillet without trimming


2. If necessary, enter t (Trim) and then enter n (No Trim).

3. Select the objects to fillet.

To fillet an entire polyline


2. Enter p (Polyline).

3. Select the polyline.

Fillet Parallel Lines

You can fillet parallel lines, xlines, and rays. AutoCAD ignores the

current fillet radius and creates an arc that is tangent to both parallel objects and located in the plane

common to both objects.

The first selected object must be a line or a ray, but the second object can be a line, an xline, or a ray.

The fillet arc connects as shown in the illustration of Fig. 1.23.

1.4.15 Explode

You can explode a compound object such as a polyline, dimension, hatch, or block reference to convert

it into individual elements. For example, exploding a polyline breaks it down to simple lines and arcs.

Exploding a block reference or an associative dimension replaces it with copies of the objects that

compose the block or dimension.

To explode an object

1. From the Modify menu, choose Explode.

2. Select the objects to be exploded. For most objects, exploding has no visible effect.

Assignments

1. Design the object of Fig. 1.24b using Fig. 1.24a as a guide.

2. Design and apply solid hatch to alternate spaces of the star as shown in Fig. 1.25b. Use

Fig. 1.25a as a guide to obtain the required object. Note that Fig. 1.25a has a pentagon

inside which is the star. Hence, use a pentagon and join the inner points to obtain the

star.

Fig. 1.23 Fillet of Parallel Lines

Fig. 1.24a Fig. 1.24b


John Annan CAD 21

1.5 ISOMETRIC DRAWINGS

To turn on an isometric plane


2. In the Drafting Settings dialog box, on the Snap and Grid tab under Snap Type & Style, select

Isometric Snap.

3. Choose OK.

To change to a different isometric plane quickly

Press F5 or CTRL+E to choose a different isometric plane.

To draw an isometric circle

If you are drawing on isometric planes, use an ellipse to represent a circle viewed from an oblique

angle. The easiest way to draw an ellipse with the correct shape is to use the Isocircle option of

ELLIPSE.


2. On the Snap and Grid tab, under Snap Type and Style, turn on the isometric snap and choose

OK.


4. Enter i (Isocircle) and specify the center of the circle.

5. Specify the radius or diameter of the circle.

Example: To draw Isometric Object of Fig. 1.26

i. Turn Snap and Isometric Grid on

Command: <Snap on>

Command: <Grid on>

ii. Select line or polyline command

Command: _pline

Specify start point: click any point (point 1)


Specify next point or [Arc/Halfwidth/Length/Undo/Width]: Jump 4 points (J4p). Click point (Cp) 2.

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: J4p. Cp3






Command:

iii. Select line or polyline command

Command: _pline

Specify start point: click point 6


Specify next point or [Arc/Halfwidth/Length/Undo/Width]: J4p. Cp7







Command:

iv. Select line or polyline command

Fig. 1.25a Fig. 1.25b

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15 16

Fig. 1.26

C

A A

B


John Annan CAD 22

Command: _pline

Specify start point: click point 10


Specify next point or [Arc/Halfwidth/Length/Undo/Width]: J4p. Cp3





Command:

v. Select line or polyline command

Command: _line Specify first point: click point 3

Specify next point or [Undo]: J4p. Cp14

Command:

vi. Select line or polyline command




Command:

vii. Select line or polyline command




Command:

viii. Choose an isometric plane by typing isoplane at command line

Command: isoplane

Current isoplane: Left

Enter isometric plane setting [Left/Top/Right] <Top>: L

Command:

ix. Draw isometric circle using ellipse isocircle

Command: _ellipse

Specify axis endpoint of ellipse or [Arc/Center/Isocircle]: i

Specify center of isocircle: click centre of plane A

Specify radius of isocircle or [Diameter]: click midpoint of one of the enclosing edges

Command:

x. Choose another isometric plane by typing isoplane at command line

Command: isoplane

Current isoplane: Left

Enter isometric plane setting [Left/Top/Right] <Top>: R

Command:

xi. Draw isometric circle using ellipse isocircle

Command: _ellipse


Specify center of isocircle: click centre of plane B


Command:

xii. Choose another isometric plane by typing isoplane at command line

Command: isoplane

Current isoplane: Right

Enter isometric plane setting [Left/Top/Right] <Top>: T

Command:

xiii. Draw isometric circle using ellipse isocircle

Command: _ellipse


Specify center of isocircle: click centre of plane C



John Annan CAD 23

Command:

Assignment

Using isometric grid and snap as well as isoplane, ellipse isocircle option and trim commands, draw the

isometric diagrams shown in figures 1.27 and 1.28.

Fig. 1.27


John Annan CAD 24

1.6 THREE DIMENSIONAL PLOTS

Three dimensional plots are solid figures that have x,y,z coordinates. Solid figures could be spheres,

pyramids or prisms. Each of these has special properties that define its area and volume. AutoCAD

presents several ways of drawing 3D objects based upon parameters that define properties of the object.

Notably amongst them are the use of; elevation command, preset solids, extrusion and revolve

commands.

1.6.1 Elevation

The default Z value above or below the XY plane of the current user coordinate system, which is used

for entering coordinates and digitizing locations. (ELEV). The ELEV command sets elevation and

extrusion thickness of new objects.

The current elevation is the Z value that AutoCAD uses whenever it

expects a 3D point but receives only X and Y values. AutoCAD

maintains separate current elevations in model space and paper space.

Specifying an elevation setting in one viewport makes that elevation

current in all viewports regardless of whether viewports are set up to

retain their own user coordinate systems (UCSs). AutoCAD resets the

elevation to 0.0 whenever you change the coordinate system.

Command line: elev (or 'elev for transparent use)

Specify new default elevation <current>: Specify a distance or

press ENTER

Specify new default thickness <current>: Specify a distance or

press ENTER

The thickness sets the distance to which AutoCAD extrudes a 2D

object above or below its elevation. A positive value extrudes along

the positive Z axis; a negative value extrudes along the negative Z axis. Note, that ELEV controls only

new objects; it does not affect existing objects.

Fig. 1.28


John Annan CAD 25

Example 1

i. Enter the command ELEV at the command prompt to set elevation at zero (0) and thickness 60.

Command: elev Specify new default elevation <60.0000>: 0

Specify new default thickness <0.0000>: 50

ii. Click the line command button, click any convenient place for start point of object and moving in

anticlockwise direction while ORTHO is on, enter short distances of 100 and long distances of 200.

Command: _line Specify first point: click any convenient point

Specify next point or [Undo]: 200

Specify next point or [Undo]: 100

Specify next point or [Close/Undo]: 100





Specify next point or [Close/Undo]: c

iii. Click SW Isometric view from the View toolbar to see an isometric view as in Fig. 3D1b.

iv. Enter the command HI to hide lines that are supposed to be hidden.

Example 2

i. Using ELEV, specify elevation of 0 and thickness of 100



ii. Select the polyline (alias PLINE) command and starting at the origin 0,0 for clockwise movement

draw a square of side 100 by 100

Command: _pline

Fig. 1.29

b a c

Fig. 1.30

b a c d e


John Annan CAD 26

Specify start point: 0,0


Specify next point or [Arc/Halfwidth/Length/Undo/Width]: 0,100

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 100,100

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 100,0

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: c

iii. Change the elevation settings for a new elevation of 100 and thickness of 150.



iv. Draw a circle of radius 30 and centre 50,50.

Command: _circle Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: 50,50

Specify radius of circle or [Diameter] <30.0000>: 40

Note: The circle will be drawn at a raised elevation of 100 and will have a thickness of 150. This means

the circle will appear as a cylinder of height 150 with its base starting from top of the square since the

circle’s elevation and square’s thickness are the same i.e. 100. Assuming the circle’s elevation is 50,

then the circle (appearing as a cylinder) will have 50 of its height buried in the square of height 100

that will appear as a cube.

v. Change the elevation settings for a new elevation of 250 and thickness of 50.



vi. Draw a pentagon of radius 30 and centre 50,50.

Command: _polygon Enter number of sides <4>: 5

Specify center of polygon or [Edge]: 50,50

Enter an option [Inscribed in circle/Circumscribed about circle] <I>: I

Specify radius of circle: 30

vii. Select the square, go to Color Control palette of Object Properties toolbar and choose red.

viii. Select the circle, go to Color Control palette of Object Properties toolbar and click yellow.

ix. Select the pentagon, go to Color Control palette of Object Properties toolbar and click green.

x. Click SW Isometric view from the View toolbar to see an isometric view as in Fig. 3D2c.

xi. Enter the command HI to hide lines that are supposed to be hidden as in Fig. 3D2d.

xii. Click on Gouraud shading in shade toolbar.

xiii. Click on 3D orbit to turn the resulting figure at various angles.

1.6.2 Solids

A solid object represents the entire volume of an object. Solids are the most informationally complete

and least ambiguous of the 3D modeling types. Complex solid shapes are also easier to construct and

edit than wireframes and meshes.

Solids are created from one of the basic solid shapes of box, cone, cylinder, sphere, torus, and wedge or

by extruding a 2D object along a path or revolving a 2D object about an axis. Once a solid is created in

this manner, more complex shapes can be created by combining solids. Solids can be joined, subtracted

from each other, or can be analysed to find their common volume (overlapping portion).

Solids can be further modified by filleting, chamfering, or changing the color of their edges. Faces on

solids are easily manipulated because they don't require you to draw any new geometry or perform

Boolean operations on the solid. AutoCAD also provides commands for slicing a solid into two pieces

or obtaining the 2D cross section of a solid.


John Annan CAD 27

Like meshes, solids are displayed as wireframes until you hide, shade, or render them. Additionally, you

can analyze solids for their mass properties (volume, moments of inertia, center of gravity, and so on).

You can export data about a solid object to applications such as NC (numerical control) milling or FEM

(finite element method) analysis. By exploding a solid, you can break it down to mesh and wireframe

objects.

The ISOLINES system variable controls the number of tessellation lines used to visualize curved

portions of the wireframe. The FACETRES system variable adjusts the smoothness of shaded and

hidden-line objects.

Example: Combination of Solids to form a Stamp

1

2

3


John Annan CAD 28

4

5

6

7


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8

9

10

11


John Annan CAD 30

12

13


John Annan CAD 31

1.6.3 Extrude

With EXTRUDE, you can create solids by extruding (adding thickness to) selected objects. You can

extrude closed objects such as polylines, polygons, rectangles, circles, ellipses, closed splines, donuts,

and regions. You cannot extrude 3D objects, objects contained within a block, polylines that have

crossing or intersecting segments, or polylines that are not closed. You can extrude an object along a

path, or you can specify a height value and a tapered angle.

Use EXTRUDE to create a solid from a common profile of an object, such as a gear or sprocket.

EXTRUDE is particularly useful for objects that contain fillets, chamfers, and other details that might

otherwise be difficult to reproduce except in a profile. If you create a profile using lines or arcs, use the

Join option of PEDIT to convert them to a single polyline object or make them into a region before you

use EXTRUDE.

Tapering the extrusion is useful specifically for parts that need their sides defined along an angle, such

as a mold used to create metal products in a foundry. Avoid using extremely large tapered angles. If the

angle is too large, the profile can taper to a point before it reaches the specified height.

To extrude an object along a path

1. From the Draw menu, choose Solids Extrude.

2. Select the objects to extrude.

3. Enter p (Path). Note: Line, polyline, spline and arc could be used as path.

4. Select the object to use as the path. After the extrusion, AutoCAD may delete or retain the

original object, depending on the setting of the DELOBJ system variable.

Example 1: Extrusion of a closed single polyline object

i. Copy the diagram of Fig. 1.4a and offset it.

Command: _offset

Specify offset distance or [Through] <8.0000>: 10

Select object to offset or <exit>: Click any line of the copied object

Specify point on side to offset: Click inside the copied selected object

Select object to offset or <exit>: ESC or

ii. Extrude the two objects (original + offset)

Command: ext EXTRUDE

Current wire frame density: ISOLINES=4

Select objects: select original object (outer object of Fig. 1.31a) 1 found

Select objects: select offset object (inner object of Fig. 1.31a) 1 found, 2 total

Select objects:

Fig. 1.31 a b c d


John Annan CAD 32

Specify height of extrusion or [Path]: 50

Specify angle of taper for extrusion <0>:

Command:

iii. View using view toolbar SW Isometric View (Fig. 1.31 c. d is in hidden mode)

iv. Subtract using subtract tool under solid editing toolbar

Command: subtract Select solids and regions to subtract from ..

Select objects: select object to subtract from (original) 1 found

Select objects: Select solids and regions to subtract ..

Select objects: select object to remove (offset object) 1 found

Select objects:

Command:

v. Shade and view by orbitting

Example 2: Extrusion of a disjointed polyline object

i. Draw three circles as shown in Fig. 1.32 a. Big circle R100, top circle at quadrant of big

circle R20, centre circle R30. Fig. 1.32 a

Command: _circle Specify center point for circle or [3P/2P/Ttr (tan tan radius)]:

Specify radius of circle or [Diameter]: 100

Command: _circle Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: <Osnap on>


Command: _circle Specify center point for circle or [3P/2P/Ttr (tan tan radius)]:


Command:

ii. Polar array top small circle. Number = 12, centre of array is centre of big circle. b

iii. Trim off all unwanted areas. First select cutting edge and then unwanted areas. c

Command: _trim

Current settings: Projection=UCS, Edge=None

Select cutting edges ...

Select objects: Specify opposite corner: select all objects. 14 found

Select objects: select unwanted areas

Select object to trim or shift-select to extend or [Project/Edge/Undo]: select unwanted areas

Select object to trim or shift-select to extend or [Project/Edge/Undo]: select unwanted areas

iv. Join all objects using polyline edit (pedit) Fig. 1.32 c

Command: pedit Select polyline or [Multiple]: m

Select objects: Specify opposite corner: select all objects using crossing window 25 found

Select objects:

Convert Lines and Arcs to polylines [Yes/No]? <Y>

Enter an option [Close/Open/Join/Width/Fit/Spline/Decurve/Ltype gen/Undo]: j

Join Type = Extend

Enter fuzz distance or [Jointype] <0.0000>: type 0.1

23 segments added to polyline

Enter an option [Close/Open/Join/Width/Fit/Spline/Decurve/Ltype gen/Undo]:

v. Extrude resulting objects as in Fig. 1.32 c

Fig. 1.32 a b c d


John Annan CAD 33

Command: ext

EXTRUDE

Current wire frame density: ISOLINES=4

Select objects: 1 found

Select objects: 1 found, 2 total

Select objects:

Specify height of extrusion or [Path]: type 50

Specify angle of taper for extrusion <0>:

Command:

vi. Subtract inner circle from outer object d

Command: _subtract Select solids and regions to subtract from ..

Select objects: Select the outer object with curved projections 1 found

Select objects: Select solids and regions to subtract ..

Select objects: select inner circle 1 found

Select objects:

Command:

vii. Shade, view and rotate to have clear d

1.6.4 Revolve

With REVOLVE, you can create a solid by revolving a closed object about the X or Y axis of the current

UCS, using a specified angle. You can also revolve the object about a line, polyline, or two specified

points. Similar to EXTRUDE, REVOLVE is useful for objects that contain fillets or other details that

would otherwise be difficult to reproduce in a common profile. If you create a profile using lines or arcs

that meet a polyline, use the PEDIT Join option to convert them to a single polyline object before you

use REVOLVE.

You can use REVOLVE on closed objects such as polylines, polygons, rectangles, circles, ellipses, and

regions. You cannot use REVOLVE on 3D objects, objects contained within a block, polylines that

have crossing or intersecting segments, or polylines that are not closed.

Fig. 1.33 Revolving with a Line as mirror axis


John Annan CAD 34

1.6.5 Solids Editting

With UNION, you can combine the total volume of two or more solids or two or more regions into a

composite object.

With SUBTRACT, you can remove the common area of one set of solids from another. For example,

you can use SUBTRACT to add holes to a mechanical part by subtracting cylinders from the object.

With INTERSECT, you can create a composite solid from the common volume of two or more

overlapping solids. INTERSECT removes the non overlapping portions and creates a composite solid

from the common volume.

INTERFERE performs the same operation as INTERSECT, but INTERFERE keeps the original two

objects.

1.7 THREE DIMENSIONAL VIEW AND ORBIT

To start 3D Orbit view

1. Select the object or objects you want to view with 3DORBIT. You can view your entire model

by not selecting any objects. However, viewing only selected objects enhances performance.

2. From the View menu, choose 3D Orbit. An arcball is displayed within the active viewport. If the

UCS icon is on, it appears shaded. If the GRID is on, a 3D line grid replaces the 2D dot grid.

3. Click and drag the cursor to rotate the view. When you move your cursor over different parts of

the arcball, the cursor icon changes. The appearance of your cursor when you click to start

dragging indicates the rotation of the view as follows:

A small sphere encircled by two lines is the cursor icon displayed when you move the cursor

inside the arcball. By clicking and dragging when the cursor is a sphere you can manipulate the

view freely. It works as if your cursor were grabbing a sphere surrounding the objects and

dragging the sphere around the target point. You can drag horizontally, vertically, and

diagonally.

A circular arrow around a small sphere is the cursor icon displayed when you move the cursor

outside the arcball. Clicking outside the arcball and dragging the cursor around the arcball

moves the view around an axis that extends through the center of the arcball, perpendicular to

the screen. This is called a "roll." If you drag the cursor into the arcball, it changes to a small

sphere encircled by two lines and the view moves freely, as described above. If you move the

cursor back outside the arcball, you revert to a roll.

A horizontal ellipse around a small sphere is the cursor icon displayed when you move the

cursor over one of the smaller circles on the left or right side of the arcball. Clicking and

dragging from either of these points rotates the view around the vertical or Y axis that extends

through the center of the arcball. The Y axis is represented on the cursor by a vertical line.

A vertical ellipse around a small sphere is the cursor displayed when you move the cursor over

one of the smaller circles on the top or bottom of the arcball. Clicking and dragging from either

of these points rotates the view around the horizontal or X axis that extends through the center of

the arcball. The X axis is represented on the cursor by a horizontal line.

Note: You cannot edit objects while 3DORBIT is active. To exit 3DORBIT, press ENTER or ESC, or

choose Exit from the shortcut menu.

To start a continuous orbit

1. Start 3DORBIT, right-click in the drawing area, and choose More Continuous Orbit. The cursor

changes to a small sphere encircled by two lines.

2. Click and drag in the direction that you want the continuous orbit to move.


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3. Release the pick button. The orbit continues moving in the direction that you indicated with your

pointing device.

4. To change the direction of the continuous orbit, click and drag in a new direction and release the

pick button. The direction of the continuous orbit changes.

To use a zoom window in the 3D Orbit view

1. Start 3DORBIT, right-click in the drawing area, and choose More Zoom Window from the

shortcut menu. The cursor changes to a window icon, and you can select a specific area that you

want to zoom.

2. Click and drag the pointing device to draw a square around the area you want to select. When

you release the pick button, the drawing is zoomed in, focused on the area you selected.

1.8 SHADE

To change the shading mode in 3D Orbit view

1. Start 3DORBIT, right-click in the drawing area, and choose Shading Modes from the shortcut

menu.

2. Choose one of the following options:

Wireframe: Displays the objects in the 3D view using lines and

curves to represent the boundaries.

Hidden. Displays the objects in

the 3D view using wireframe representation with the lines

representing the back faces hidden.

Flat Shaded. Shades the objects in the 3D view between the

polygon faces. This gives the objects a faceted, less smooth

appearance.

Gouraud Shaded. Shades the objects in the 3D view and

smooths the edges between polygon faces. This gives the

objects a smoother, more realistic appearance.

Flat Shaded, Edges On. Combines the Flat Shaded and

Wireframe options. The objects are flat shaded with the

wireframe showing through.

Gouraud Shaded, Edges On. Combines the Gouraud Shaded

and Wireframe options. The objects are Gouraud shaded

with the wireframe showing through.

Note: When you shade objects in the 3D Orbit view, the shading is still applied to the objects after you

exit 3DORBIT. Use SHADEMODE to change the shading when 3DORBIT is not active.


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1.9 BASIC CALCULATIONS WITH AUTOCAD

1.9.1 Addition, Subtraction, Multiplication and Division

The result of the addition. If you supply only one number argument, this function returns the result of

adding it to zero. If you supply no arguments, the function returns 0.

Examples

(+ 1 2) returns 3

(+ 1 2 3 4.5) returns 10.5

(+ 1 2 3 4.0) returns 10.0

The result of the subtraction. If you supply more than two number arguments, this function returns the

result of subtracting the sum of the second through the last numbers from the first number. If you supply

only one number argument, this function subtracts the number from zero, and returns a negative

number. Supplying no arguments returns 0.

Examples

(- 50 40) returns 10

(- 50 40.0) returns 10.0

(- 50 40.0 2.5) returns 7.5

(- 8) returns -8

The result of the multiplication. If you supply only one number argument, this function returns the

result of multiplying it by one; it returns the number. Supplying no arguments returns 0.

Examples

(* 2 3) returns 6

(* 2 3.0) returns 6.0

(* 2 3 4.0) returns 24.0

(* 3 -4.5) returns -13.5

(* 3) returns 3

The result of the division. If you supply more than two number arguments, this function divides the first

number by the product of the second through the last numbers, and returns the final quotient. If you

supply one number argument, this function returns the result of dividing it by one; it returns the number.

Supplying no arguments returns 0.

Examples

(/ 100 2) returns 50

(/ 100 2.0) returns 50.0

(/ 100 20.0 2) returns 2.5

(/ 100 20 2) returns 2

(/ 4) returns 4

1.9.2 Other Mathematical Operations

Display a message in an alert box:

(alert "That function is not available.")

Display a multiple line message, by using the newline character in string:

(alert "That function\nis not available.")

Note: Line length and the number of lines in an alert box are platform, device, and window dependent.

AutoCAD truncates any string that is too long to fit inside an alert box.

Returns the 3D distance between two points

(distance pt1 pt2)

Arguments pt1 A 2D or 3D point list.

Pt2 A 2D or 3D point list.


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Return Values

The distance.

If one or both of the supplied points is a 2D point, then distance ignores the Z coordinates of any 3D

points supplied and returns the 2D distance between the points as projected into the current construction

plane.

Examples

Command: (distance '(1.0 2.5 3.0) '(7.7 2.5 3.0)) 6.7

Command: (distance '(1.0 2.0 0.5) '(3.0 4.0 0.5)) 2.82843

Autocad 2002

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