chapter 3 geometric construction and editing...

AutoCAD 2015 Tutorial: 2D Fundamentals 3-1

Chapter 3Geometric Construction and Editing Tools

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• Set up the display of Drawing Units• Display AutoCAD's toolbars• Set up and use OBJECT SNAPS• Edit, using EXTEND and TRIM• Use the FILLET command• Create parallel geometric entities• Using the PEDIT command• Use the EXPLODE command

3-2 AutoCAD 2015 Tutorial: 2D Fundamentals

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AutoCAD Certified User Examination Objectives CoverageThis table shows the pages on which the objectives of the Certified User Examination are covered inChapter 3.

Section 1: Introduction to AutoCADPoint Style 3-16OrthoMode 3-25Precision 3-25Drafting Settings 3-26Snap and Grid 3-26

Section 2: Creating Basic DrawingsStart from Scratch 3-5Geometric Construction 3-6Bisection of a Line or Arc 3-6Snap to Perpendicular 3-6Snap to Midpoint 3-6Bisection of an Angle 3-9Construction Line 3-9Snap to Node 3-16Circle through Three Points 3-173-Point Circle 3-17Line Tangent to a circle from a Given Point 3-18Circle of a Given Radius Tangent to Two Lines 3-21Fillet command 3-20

Section 3: Manipulating ObjectsMove command 3-7Rotate command 3-11Transfer of an Angle 3-11Copy command ...3-11Dividing a Given Line into Equal Parts 3-15Point, Divide 3-16Extend command 3-30

Section 4: Drawing Organization and Inquiry CommandsQuickCalc command 3-12Angle of Line Defined by Two Points 3-13Measure Area and Perimeter 3-36

Section 5: Altering ObjectsOffset command 3-34Edit Polyline 3-34Explode 3-38

Section 11: Creating Additional Drawing ObjectsPolylines 3-34

Geometric Construction and Editing Tools 3-3

Tips on Taking the AutoCAD Certified User Examination

1. Study: The first step to maximize your potential on an exam is to sufficientlyprepare for it. You need to be familiar with the AutoCAD package, and thiscan only be achieved by doing drawings and explore the different commandsavailable. The AutoCAD Certified User exam is designed to measure yourfamiliarity with the AutoCAD software. You must be able to perform thegiven task and answering the exam questions correctly and quickly.

2. Make Notes: Take notes of what you learn either while attending classroomsessions or going through study material. Use these notes as a review guidebefore taking the actual test.

3. Time Management: Manage the time you spent on each question. Alwaysremember you do not need to score 100% to pass the exam. Also keep in mindthat some questions are weighed more heavily and may take more time toanswer.

4. Be Cautious: Devote some time to ponder and think of the correct answer.Ensure that you interpret all the options correctly before selecting fromavailable choices.

5. Use Common Sense: If you are unable to get the correct answer and unable toeliminate all distracters, then you need to select the best answer from theremaining selections. This may be a task of selecting the best answer fromamongst several correct answers, or it may be selecting the least incorrectanswer from amongst several poor answers.

6. Take Your Time: The examination has a time limit. If you encounter aquestion you cannot answer in a reasonable amount of time, use the Save Asfeature to save a copy of the data file, and mark the question for review. Whenyou review the question, open your copy of the data file and complete theperformance task. After you verify that you have entered the answer correctly,unmark the question so it no longer appears as marked for review.

7. Don't Act in Haste: Don't go into panic mode while taking a test. Alwaysread the question carefully before you look out for choices in hand. Use theReview screen to ensure you have reviewed all the questions you may havemarked for review. When you are confident that you have answered allquestions, end the examination to submit your answers for scoring. You willreceive a score report once you have submitted your answers.

8. Relax before exam: In order to avoid last minute stress, make sure that youarrive 10 to 15 minutes early and relax before taking the exam.

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Geometric ConstructionsThe creation of designs usually involves the manipulations of geometric shapes.Traditionally, manual graphical construction used simple hand tools like a T-square,straightedge, scales, triangles, compass, dividers, pencils, and paper. The manual draftingtools are designed specifically to assist in the construction of geometric shapes. Forexample, the T-square and drafting machine can be used to construct parallel andperpendicular lines very easily and quickly. Today, modern CAD systems providedesigners much better control and accuracy in the construction of geometric shapes.

In technical drawings, many of the geometric shapes are constructed with specificgeometric properties, such as perpendicularity, parallelism and tangency. For example, inthe drawing below, quite a few implied geometric properties are present.

Implied Geometric Properties

Tangent //Parallel

Vertical line

ConcentricArc & Circles Concentric

Arc 8. Circle

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Starting Up AutoCAD 20151. Select the AutoCAD 2015 option on the Program menu or select the AutoCAD

2015 icon on the Desktop. Once the program is loaded into the memory, theAutoCAD 2015 drawing screen will appear on the screen.

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2. In the Startup window, select Start from Scratch, as shown in the figure below.

Startup

Start from Scratch

Default Settings

|T§) Imperial (feet and inches)

C ) Metric

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TipUses the default imperial feet and inches} settings.

OK Cancel

3. In the Default Settings section, pick Imperial (feet and inches) as the drawingunits.

4. Pick OK in the Startup dialog box to accept the selected settings.


Geometric Construction - CAD MethodThe main characteristic of any CAD system is its ability to create and modify 2D/3Dgeometric entities quickly and accurately. Most CAD systems provide a variety of objectconstruction and editing tools to relieve the designer of the tedious drudgery of this task,so that the designer can concentrate more on design content. A good understanding of thecomputer geometric construction techniques will enable the CAD users to fully utilize thecapability of the CAD systems.

> Note that with CAD systems, besides following the classic geometric constructionmethods, quite a few options are also feasible.

• Bisection of a Line or Arc

A

1. Create an arbitrary arc AB at anyangle, and create line AB byconnecting the two endpoints of thearc.

Dynamic Input - ; Y;

DYNMODE

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2. Switch ON only the Dynamic Inputoption by clicking on the buttonsin the Status Bar area as shown.

Select the Line command icon in the Draw toolbar. Inthe command prompt area, near the bottom of theAutoCAD drawing screen, the message u_line Specifyfirst point:" is displayed. AutoCAD expects us toidentify the starting location of a straight line.

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3Snap to Perpendicular

Snaps to a pcin perpendicular

4. Pick Snap to Perpendicular in the ObjectSnap toolbar. In the command prompt area, themessage "_per to" is displayed.


5. Select line AB at any position.

<* Note the tooltip DeferredPerpendicular is displayed indicatinjthe construction is deferred until allinputs are completed.

6. Select an arbitrary point above theline as shown.

Enter

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Recent Input

Undo

Snap Overrides

Specify rwxt point or lil MHM 7.94i?

7. Inside the Drawing Area, right-mouse-click to activatethe option menu and select Enter with the left-mouse-button to end the Line command.

8. Select Move in the Modify toolbar as shown.

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Moves objects a specified

9. Select the perpendicular line we justcreated.

<* In the command prompt area, themessage: "Specify the base point or[Displacement]" is displayed. AutoCADexpects us to select a reference point asthe base point for moving the selectedobject.

3-i AutoCAD 2015 Tutorial: 2D Fundamentals

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Snap to Eisdpomt

Snaps to the e'Bsest endc-i

10. Pick Snap to Endpoint in the Object Snaptoolbar.

l-o r" /'xjx x — © ooiSnap to MidpointSnaps to the midpoint of ar, obje

11. Select the lower Endpoint of theselected line as shown.

12. Move the cursor inside the DrawingArea, and notice the line is moved to thenew cursor location on the screen.

13. Pick Snap to Midpoint in the ObjectSnap toolbar.

*> In the command prompt area, themessage "_midto" is displayed.AutoCAD now expects us to select anexisting arc or line on the screen.

14. Select the arc to move the line to themidpoint of the arc. Note that themidpoint of an arc or a line is displayedwhen the cursor is on top of the object.

15. On your own, repeat the above process and move the perpendicular line to themidpoint of line AB.

> The constructed bisecting line is perpendicular to line AB and passes through themidpoint of the line or arc AB.


Bisection of an Angle

1. Create an arbitrary angle ABC as shown in thefigure.

Home I Insert Annotate Parametric

Line Polyline Circle Arc

2. Click once with the left-mouse-button on thesmall triangle in the titlebar of the Drawtoolbar as shown.

Line Pclvline Circle Arc

Creates a line of infinite length

Bisect

Offset

Snap to Endpo'ietSnsps to the dosestendpsi

3. Select the Construction Line icon in theDraw toolbar. In the command prompt area,the message "_xline Specify a point or[Hor/Ver/Ang/Bisect/ Offset]:" is displayed.

Construction lines are lines that extend toinfinity. Construction lines are usually usedas references for creating other objects.

4. Inside the Drawing Area, right-mo use-click once to bringup the option menu.

5. Select Bisect from the option list as shown. In thecommand prompt area, the message "Specify angle vertexpoint:" is displayed.



7. Select the vertex point of the angle asshown. In the command prompt area, themessage "Specify angle start point:" isdisplayed.

Pick Snap to Endpoint in the ObjectSnap toolbar.

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Snap to EndpmntSnaps to the cosest e,ndpoi

9. Select one of the endpoints of the angle.

X X X —- © '1 10. Pick Snap to Endpoint in the Object SnapI toolbar.

Snap to Endpoint psnaps go^the dasast endcaiH 11. Select the other endpoint of the angle.

Note that the constructed bisection line divides the angle into two equal parts.


Transfer of an Angle

1. Create an arbitrary angle ABCand a separate line XY asshown in the figure.

> CAD systems provide severaloptions to allow the user toaccurately measure constructedobjects over the classical boarddrafting technique (See page 3-14). For this example, we willuse the QuickCalc option totransfer the angle.

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2. Select Copy in the Modify toolbar as shown.

Snaps bo the aa&sstendpsii

3. Select line XY as the object to be copied.

4. Right-mouse-click once to proceed with the Copy command.


6. Select point X as the base point.

7. Use the Snap to Endpoint option and select point X again to place another lineon top of line XY.

8. Hit the ENTER key once to end the Copy command.

9. Select Rotate in the Draw toolbar as shown.

10. Select one of the two lines at XY.

11. Right-mouse-click once to proceed with theRotate command.


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Bnsps to the dosest ejidpsi

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Angle of Line Defined


13. Select point X as the base point for the rotation.

14. Inside the Drawing Area, right-mouse-click once tobring up the option menu.

15. Select QuickCalc in the option menu as shown.

16. Select Angle of Line Definedby Two Points as shown.

> Note the Distance option is alsoavailable in the toolbar region.

17. Pick Snap to Endpoint in theObject Snap toolbar.

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Snap to Endpoint

Snaps to the cfasest -snd'gai

18. Select the vertex, point B, of theangle ABC as shown.

19. Pick Snap to Endpoint in the ObjectSnap toolbar.

Snap to Enffpoint

Snaps to the c-asest endpsi

20. Select point A as the second point tomeasure the angle as shown.

The default system for measuring angles in AutoCAD 2015 defines positive angularvalues as counterclockwise from the positive X-axis.


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196.955652^

Active CommaUs: ROTATE

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196,955652-101,58...

35.366658

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21. Enter a minus sign behind thedisplayed angle in the QuickCalcwindow.

> Note the display of ActiveCommand: Rotate in theQuickCalc window.

22. Select the Angle of Line Definedby Two Points option as shown.

23. Repeat the above process andmeasure the angle formed by lineBC and the positive X-axis.

24. Press the ENTER key once tocalculate the difference between thetwo values, which is the angleformed by line AB and line BC.

A QuickCatc

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196.955652081.58...

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ive Command: ROTATE

25. Enter a minus sign in front of the calculated value inthe QuickCalc window as shown.

> The minus sign is used to create the new line in theclockwise direction. (We will rotate the line in aclockwise direction relative to the current XY line.)

HiI 26. Click Apply to transfer the calculated value to the command promptL™l

area.

The calculated value is now transferred in the command prompt area.

{Resuming ROTATE command^.

1*3- ROTATE Specify rotation angle or [Copy Reference] <&>: -35.366653

Model • Layout! Layout? * • 1,3062,3.3585,0.0000 MODE


27. Press the ENTER key once to accept the displayed value and complete theRotate command.

You are also encouraged to perform this geometric construction using theclassical method as described below. (Note that R is an arbitrary distance.)


• Dividing a Given Line into a Number of Equal Parts

I. Create a line AB at an arbitrary angle; the lineis to be divided into five equal parts.

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Line Polyline Circle ArcC*> *

O <eDraw

2. From the Draw toolbar, select:

[Divide]

3. Select line AB. In the message area, themessage "Enter the number of segments or[Block]:" is displayed.

Divide

Enter the numb*f of segments or

4. Enter 5 as the number of segmentsneeded.

5. On your own, create an arbitrary short line segment at pointA.

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Copy

Copies object: a specific

6. Select Copy in the Modify toolbar as shown.

7. Select the short line as the object to be copied.

8. Right-mouse-click once to proceed with the Copycommand.


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9. Pick Snap to Endpoint in the 06/ecftoolbar.

10. Select point A as the base reference point.

1. Pick Snap to Node in the Object Snap toolbar.

12. Move the cursor along line AB, and select the nextnode point as shown.

13. Repeat the above steps and create 3 additional linesat the nodes indicating the division of the line intofive equal parts.

~> We can also change the display of the created Points.

14. In the Menu Bar, select:

[Format] -> [Point Style]

15. In the Point Style window, choose the 4th icon in thesecond row, as shown.

Point Style

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1OK ,. 11 16. Click OK to accept the selection and adjust the point style.


Circle through Three Points

1. Create two arbitrary linesegments, AB and BC, asshown.

2. Select the 3-Point Circle command in theDraw toolbar as shown.


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Snap to End pointSnsps to the closest endpoi

4. Select the first point, point A.

5. Repeat the above steps and select points B and C tocreate the circle that passes through all three points.

B


• Line Tangent to a Circle from a Given Point

1. Create a circle and a point A. (Use thePoint command to create point A.)

Home ! Insert Annotate ParameM

Line Polyline Circle Arc

DrawMultiple Points

Snap to Node

2. Select the Line command icon in the Draw toolbar. Inthe command prompt area, near the bottom of theAutoCAD drawing screen, the message "_line Specifyfirst point:" is displayed. AutoCAD expects us toidentify the starting location of a straight line.

3. Pick Snap to Node in the Object Snap toolbar.

4. Select point A as the starting point of the new line.

5. Pick Snap to Tangent in the Object Snap toolbar.

6. Move the cursor on top of the circle andnotice the Tangent symbol is displayed.

Note that we can create two tangentlines, one to the top and one to thebottom of the circle, from point A.


Circle of a Given Radius Tangent to Two Given Lines

Option I: TTR circle

i. Create two arbitrary linesegments as shown.

Line Polyline

. Drawingl

0Circle

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Arc

Center, Radius

Center, Diameter

Stretc|

2. Select TTR Circle in the Draw toolbar asshown.

3. Select one of the line segments; note thetangency is deferred until all inputs arecompleted.

4. Select the other line segment; note the tangency isalso deferred until all inputs are completed.


Specify radius of circle <i.9230>; | 3| !

5. Enter 3 as the radius of the circle.

> The circle is constructed exactlytangent to both lines.

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Option II: Fillet Command

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1. Select the Undo icon in the Standardtoolbar as shown. This will undo the laststep, the circle.

2. Select Fillet in the Modify toolbar as shown.

3. In the command prompt area, the message "Select first object or[Undo/Polyline/Radius/Trim/Multiple]" is displayed. By default Mode is set toTrim and the current arc Radius is set to 0.

Current settings: Mode = TRIM., Radius = 0.6000

FILLET Select first object or [Undo Polyline Radius Trim Multiple]:

Model La'/cutl Lavout2 24,6649,4,0822,0.0000 MODE


Undo

Polyline

Radius.

Trim *

.Multiple

Specify fillet rad.us <0£000> : [ 3| |

4. Inside the Drawing Area, right-mouse-click once to brinjup the option menu.

5. Select Radius to adjust the radius of the fillet

6. Enter 3 as the new radius of the Filletcommand.

B

A

7. Select one of the lines as the firstobject.

B

Select second object oC7

8. Select the other line as the secondobject.

> Note that the default setting of theFillet command is to trim the edgesas shown in the figure below.

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Note that all of the classical methods for geometric construction, such as the oneshown on page 3-14, are also applicable in CAD systems.


The Gasket Design

Exploring the possibilities of a CAD system can be very exciting. For persons who haveboard drafting experience, the transition from the drafting board to the computer doesrequire some adjustment. However, the essential skills required to work in front of acomputer are not that much different from those needed for board drafting. In fact, manyof the basic skills acquired in board drafting can also be applied to a computer system.For example, the geometric construction techniques that are typically used in boarddrafting can be used in AutoCAD. The main difference between using a CAD systemover the traditional board drafting is the ability to create and modify geometric entitiesvery quickly and accurately. As it was illustrated in the previous sections, a variety ofobject construction and editing tools, which are available in AutoCAD, are fairly easy touse. It is important to emphasize that a good understanding of the geometric constructionfundamentals remains the most important part of using a CAD system. The application ofthe basic geometric construction techniques is one of the main tasks in using a CADsystem.

In the following sections, we will continue to examine more of the geometricconstruction and editing tools provided by AutoCAD 2015. We will be looking at thegeometric construction tools, such as Trim, Extend, Edit Polyline and Offset that areavailable in AutoCAD 2015.

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Before continuing to the next page, on your own make a rough sketch showing thesteps that can be used to create the design. Be aware that there are many differentapproaches to accomplishing the same task.


Drawing Units Display SetupBefore creating the first geometric entity, the value of the units within the CAD systemshould be determined. For example, in one drawing, a unit might equal one millimeter ofthe real-world object. In another drawing, a unit might equal an inch. The unit type andnumber of decimal places for object lengths and angles can be set through the UNITScommand. These drawing unit settings control how AutoCAD interprets the coordinateand angle entries and how it displays coordinates and units in the Status Bar and in thedialog boxes.

Layer States Manager.

Layer tools

Color...

Linetype...

Line weight...

Transparency

Scale List...

Text Style...

Dimension Style,..

TablsStyle...

Multrteader Style

Plot Et.'le...

Point Style.,.

Multiline Style...

Unit,.. fe

Thickness;

Drawing Limits

1. In the Menu Bar select:

[Format] -» [Units]

2. In the Drawing Units dialog box, confirm the Length Type to Decimal. This isthe default measurement to English units, inches.

Drawing Units

AngleType:

Precision:

P 1 Clockwise

3. Set the Precision to two digits after the decimal point.

4. Pick OK to exit the Drawing Units dialog box.


GRID and SNAP Intervals Setup1. In the Menu Bar, select:

[Tools] -> [Drafting Settings]

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Named UCS...

Geographic Location.

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Drafting Settings...

Group

2. In the Drafting Settings dialog box, select the Snap and Grid tab if it is not thepage on top.

3. Change Grid Spacing to 7.00 for both X and Y directions.

Drafting Settings

j" Snap and Grid^pda7TracklTOl

7j Snap On (F9J

Snap spacing

Snap Xspacing: "•

Snsp Yspacing: «•

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Polar spacing

Snap typo

'6' Grid snap

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'' .' Isometric snap

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Grid styleDisplay dotted grid in:

|y]2D model space

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Grid spacing

Grid Xspacing:

Grid Yspscing:

Major line every:

1.00

Grid behavior

[•/] Adaptive grid

Cl^low subdivision below gridspacing

[j/] Display grid be-yojid LimitB

[.J Follow Dynamic UCS

4. Switch ON the GnW On and Swap Ow options as shown.

5. Pick OK to exit the Drawing Units dialog box.


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6. On your own, use the Zoom Extentscommand, under the View pull-downmenu, to reset the display.

Notice in the Status Bar area, the GRID and SNAP options are pressed downindicating they are switched ON. Currently, the grid spacing is set to 1 inch and thesnap interval is set to 0.5 inch.

SNAP & GRID ON

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Using the LINE Command with ORTHO option

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Home Insert Annotate

Polyline Circle Arc

Draw »

2.

Select the Line command icon in the Draw toolbar. Inthe command prompt area, near the bottom of theAutoCAD drawing screen, the message "_line Specifyfirst point:" is displayed. AutoCAD expects us toidentify the starting location of a straight line.

In the Drawing Area, move the cursor to worldcoordinates (4,6). Left-click to position the startingpoint of the line at that location.

Restrict cursor orthogonally -

ORTHOMODE (F8)

/

We will next turn CWthe ORTHO option bytoggling on the ORTHO button in the StatusBar area.

T X ' xThe ORTHO option constrains cursor movement to the horizontal or verticaldirections, relative to the current coordinate system. With the Line command, weare now restricted to creating only horizontal or vertical lines with the ORTHOoption.


4. Move the graphics cursor below the last point we selected on the screen andcreate a vertical line that is two units long (Ycoordinate: 4.00).

5. Move the graphics cursor to the right of the last point and create a horizontal linethat is one unit long (Xcoordinate: 5.00).

6. Move the graphics cursor below the last point and create a vertical line that is 2.5units long (Y coordinate: 1.50).

3 EL

Snap mode - Off

SNAPMODE(F9)7. Turn OFF the SNAP option in the Status Bar

area.

8. Move the graphics cursor to the right of the last point and create a horizontal linethat is about seven units long (near Xcoordinate: 12.00). As is quite commonduring the initial design stage, we might not always know all of the dimensions atthe beginning.

x

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10. In the Status Bar area, reset the optionbuttons so that only the GRIDDISPLAY, and ORTHO MODEoptions are switched ON.

Repeat LINE

Recent Input

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11. Activate the Line command by picking the icon in theDraw toolbar or right-mouse-click to activate the optionmenu and select Repeat Line.


Object Snap Toolbar*> Object Snap is an extremely powerful construction tool available on most CAD

systems. During an entity's creation operations, we can snap the cursor to pointson objects such as endpoints, midpoints, centers, and intersections. For example,we can quickly draw a line to the center of a circle, the midpoint of a linesegment, or the intersection of two lines.

1. Bring up the Object Snap toolbar through the [Tools] - [Toolbars] menu.

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Snap to Endpoint

J

2. In the Object Snap toolbar, pick Snap to Endpoint. In the command promptarea, the message "_endp of is displayed, AutoCAD now expects us to select ageometric entity on the screen.

The Snap to Endpoint option allows us to snap to the closest endpoint of objectssuch as lines or arcs. AutoCAD uses the midpoint of the entity to determine whichend to snap to.

3. Pick the top left vertical line by selecting a locationabove the midpoint of the line. Notice AutoCADautomatically snaps to the top endpoint of the line.

4. Move the graphics cursor to the right of the lastpoint and create a horizontal line that is about threeunits long (near Xcoordinate: 7.00).

Enter K

Cancel

Recent In put


Insert Annotate Parar

o—•o—'

Line Polyline

Drau

Center, Radius

Creates a circle L

6. Select the Circle-Radius command icon in theDraw toolbar. In the command prompt area, themessage "Specify center point for circle or[3P/2P/Ttr (tan tan radius)]:" is displayed.

7. In the Status Bar area, switch 07V the SNAP option.


8. In the Drawing Area, move the cursor to world coordinates (11.5,6). Left-clickto position the center point of the circle at this location.

9. Move the graphics cursor to world coordinates (13,6). Left-click at this locationto create a circle (radius 1.5 inches).

|-Jftop]i2DWiiefrime]

X

Polyline Circle Arc

10. Select the Line command icon in the Draw toolbar. Inthe command prompt area, the message "_line Specifyfirst point:'" is displayed.

11. In the Drawing Area, move the cursor to worldcoordinates (11,1.5). Left-click to position the firstpoint of a line at this location.

12. Pick Snap to Tangent in the Object Snap toolbar. In the command prompt area,the message "Jan to" is displayed. AutoCAD now expects us to select a circle oran arc on the screen.

<* The Snap to Tangent option allows us to snap to the point on a circle or arcthat, when connected to the last point, forms a line tangent to that object.


13. Pick a location on the right side of thecircle and create the line tangent to thecircle. Note that the Object Snap optionstake precedence over the ORTHOoption.

Enter

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Recent Input


Y

W

15. In the Status Bar area, reset the option buttons so that none of the buttons areswitched ON.

EL m m -

16. Close the Object Snap toolbar by left-clicking the upper right corner X icon.

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Using the EXTEND Command• The Extend command lengthens an object so that it ends precisely at a selected

boundary.

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Extend

1. Select the Extend command icon in theModify toolbar. In the command prompt area,the message "Select boundary edges... Selectobjects:" is displayed.

<* First, we will select the objects that definethe boundary edges to which we want toextend the object.

2. Pick the circle as the boundaryedge.

3. Inside the Drawing Area, right--mouse-click to proceed with theExtend command.

4. The message "Selectobject to extend or shift-select object to trim or[Project/Edge/Undo]:" isdisplayed in the commandprompt area. Extend thehorizontal line that is tothe left side of the circleby clicking near the rightendpoint of the line.

Enter

Cance5. Inside the Drawing Area, right-mouse-click to activate the

option menu and select Enter with the left-mouse-button toend the Extend command.


Using the TRIM Command• The Trim command shortens an object so that it ends precisely at a selected

boundary.Format Took; Draw Dim

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Trim

Trims objects to rr

Select the Trim command icon in the Modifytoolbar. In the command prompt area, themessage "Select boundary edges... Selectobjects:" is displayed.

First, we will select the objects that define theboundary edges to which we want to trim theobject.

2. Pick the inclined line and the tophorizontal line as the boundary edges.

3. Inside the Drawing Area, right-mouse-click to proceed with the Trim command.

4. The message "Select object to trim or shift-select object to extend or[Fence/Crossing/Project/Edge/eRase/Undo]:" is displayed in the commandprompt area. Pick the right endpoint of the bottom horizontal line.

5. Pick the bottom of thecircle by clicking on thelower portion of the circle.

6. Inside the Drawing Area,right-mouse-click toactivate the option menuand select Enter with theleft-mouse-button to endthe Trim command.

Note that in AutoCAD 2015, we can use the Extend command or the Trim commandfor trimming or extending an object. For example, when using the Extend command,we can select an object to extend or hold down SHIFT and select an object to trim.


Creating a TTR CIRCLE""jr'kruf jSkHJ* . ^ &. 1.9. L

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Radius

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Tan, Tail, RadttK

1. In the Draw toolbar, click the triangle next to theCircle icon to show the additional options.

2. In the displayed list, select the Ttr (Tan, Tan,Radius) option. This option allows us to create acircle that is tangent to two objects.

3. Pick the top horizontal line that is to the leftside of the arc. We will create a circle that istangent to this line and the circle.

4. Pick the arc by selecting a location that isabove the right endpoint of the horizontal line.AutoCAD interprets the location we selected asbeing near the tangency.

5. In the command prompt area, the message "Specify radius of circle <J.50>" isdisplayed.Specffir radius of circle <1.50>: 1.0 [ENTER]

> On your own, use the Trim command and trim the circle, the horizontal line, andthe arc as shown.


Using the FILLET Command

• Fillet rounds or fillets the edges of two arcs, circles, elliptical arcs, or lines with anarc of a specified radius.

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Fillet

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1. Select the Fillet command icon in the Modifytoolbar. In the command prompt area, the message"Selectfirst object or [Polyline/Radius/Trim]:" isdisplayed.

Undo

Polyline

Radius.

Trim ^

Multiply

2. Inside the Drawing Area, right-mouse-click to activate theoption menu and select the Radius option with the left-mouse-button to specify the radius of the fillet.

3. In the command prompt area, the message "Specify fillet radius:" is displayed.

Specify fillet radius: 0.75 [ENTER]

4. Pick the bottom horizontal line and the adjacent vertical line to create arounded corner as shown.

> On your own, use the Fillet command and create a radius 0.25 fillet at the corneras shown.


Converting Objects into a Polyline

• The next task in our project is to use the Offset command and create a scaled copy ofthe constructed geometry. Prior to using the Offset command, we will simplify theprocedure by converting all objects into a compound object - a polyline.

<* Apolyline in AutoCAD is a 2D line of adjustable width composed of line and arcsegments. A polyline is treated as a single object with definable options.

1. In the Ribbon Toolbars, select:

[Modify] -^ [Edit Polyline)

2. The message "Selectpolyline:" is displayedin the command prompt area. Select any ofthe objects on the screen.

3. The message '"'Object selected is not a polyline, Do you want to turn if into one?< 7>" is displayed in the command prompt area. Right-mouse-click to accept theYes default.

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Width

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Pan

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4. Inside the Drawing Area, right-mouse-click once to activatethe option menu and select the Join option with the left-mouse-button to add objects to the polyline.

5. Pick all objects by enclosing them inside a selection window.

6. Inside the Drawing Area, right-mouse-click once to accept the selected objects.

7. Inside the Drawing Area, right-mouse-click once to activate the option menu andselect Enter to end the Edit Polyline command.


Using the OFFSET Command• The Offset command creates a new object at a specified distance from an existing

object or through a specified point.

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1. Select the Offset command icon in the Modifytoolbar. In the command prompt area, the message"Specify offset distance or [Through]:" is displayed.

Specify offset distance or [Through]:0.5 [ENTER]

2. In the command prompt area, the message "Select object to offset or <exit>:" isdisplayed. Select any segment of the polyline on the screen.

> Since all the lines and arcs have been converted into a single object, all segmentsare now selected.

3. AutoCAD next asks us to identify the direction of the offset. Pick a location thatis inside the polyline.

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4. Inside the Drawing Area, right-mouse-click and selectEnter to end the Offset command.


Using the Area Inquiry Tool to Measure Area and Perimeter

• AutoCAD also provides several tools that will allow us to measure distance, area,perimeter, and even mass properties. With the use of polylines, measurements ofareas and perimeters can be done very quickly.

1. In the Ribbon tabs area, left-mouse-click once on theMeasure title in the Utilities toolbar as shown.

2. In the Inquiry toolbar, click on the Area icon to activate theCalculates the area and perimeter of selected objectscommand.

• Note the different Measure options that are available in thelist.

3. In the command prompt area, the message "Specify firstcorner point or [Object/Add/Subtract]:" is displayed. Bydefault, AutoCAD expects us to select points that will form apolygon. The area and perimeter of the polygon will then becalculated.

Cancel

Recent Input

Object.

Add

4

4. AutoCAD can also calculate the area and perimeter ofobjects that define closed regions. For example, a circle ora rectangle can be selected as both of these objects defineclosed regions. We can also select a region defined by apolyline. To activate this option, right-mouse-click onceinside the Drawing Area and select Object as shown.

5. In the command prompt area, the message "Select objects:"is displayed. Pick the inside polyline and the associated areaand perimeter information are shown in the prompt area.

Area = 25.93, Perimeter = 22,84

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6. Inside the Drawing Area, right-mouse-click once to bringup the option menu and select Area as shown.

Object

Add area

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7. We can also select a region defined by multiple polylines.To activate this option, right-mouse-click once inside theDrawing Area and select Add area as shown.

Recent Input

Subtract area

9.

To also activate selection of regions defined by polylines,right-mouse-click once inside the Drawing Area andselect Object as shown.

In the command prompt area, the message "[Add Mode]Select objects:" is displayed. Pick the outside polyline. Theassociated area and perimeter information are shown in theprompt area. Right-click once to end the selection.

mode) Select objects:Area » 37,36, Perimeter = 26,48

area = 37.36

MEASUREGEOM (ADD irode) Select objects

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[Object Subtract area exit];

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10. Next we will subtract the region defined bythe inside polyline. In the command promptarea, select Subtract area as shown.

11. To also activate selection of regions definedby polylines, select Object in the commandprompt area as shown.

| (SUBTRACT mode)

12. In the command prompt area, the message '''Selectobjects:" is displayed. Pick the inside polyline andthe area between the two polylines is shown in thecommand prompt area.

(SUBTRACT mode) Select objects:Area = 25.03^ Perimeter - 22.84Total area = 12,33 ________

- MEASUREGEQM (SUBTRACT (rode) Self


Using the EXPLODE Command• The Explode command breaks a compound object into its component objects.

1. Select the Explode command icon in the Modify toolbar. In the commandprompt area, the message "Select objects:" is displayed.

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2. Pick the inside polyline that we created using the Offset command.

3. Inside the Drawing Area, right-mouse-click to end the Explode command.

Create another Fillet

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1. Select the Fillet command icon in the Modifytoolbar. In the command prompt area, the message"Select first object or [Polyline/Radius/Trim]:" isdisplayed.

2. On your own, set the Fillet Radius to 0.5.Specify fillet radius: 0.5 [ENTER]

3. Pick the horizontal line and the adjacent inclined line to create a rounded corneras shown.


Saving the CAD File

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1. In the pull-down menus, select:

[File] [Save As]

2. In the Save Drawing As dialog box, select the folder in which you want to storethe CAD file and enter Gasket in the File name box.

Save Drawing As

Save in:

Name

P^Bearing.DWG

F^Bracket.dwg3 CAD ExErcisel Drawing File.dwg

p3^ GuidePlate.dwgyS Locator.cfwg3 RockerArm.dwg[ Spacer.dwg

Select the folderto store the file.

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3. Pick Save in the Save Drawing As dialog box to accept the selections and savethe file.

Exit AutoCAD• To exit AutoCAD 2015, select Exit AutoCAD from the Application Menu or type

QUIT at the command prompt.


Review Questions: (Time: 20 minutes)1. Describe when and why you would use the AutoCAD ORTHO option.

2. What is the difference between a line and ^polyline in AutoCAD?

3. Which AutoCAD command can we use to break a compound object, such as apolyline, into its component objects?

4. Which AutoCAD command can we use to quickly calculate the area and perimeter ofa closed region defined by a polyline?

5. Describe the procedure to calculate the area and perimeter of a closed region definedby a polyline?

6. What does the Offset command allow us to do?

7. Create the following triangle and measure the area and perimeter of the triangle.

Create the following triangle and measure the area and perimeter of the triangle. Alsofind the angle &.


Exercises:(Unless otherwise specified, dimensions are in inches.) (Time: 90 minutes)

1. Lines & Squares Pattern

3,0

NJ3,0

,25 TYP,

2. Interlacement Design


3. Positioning Spacer (Dimensions are in inches.)

R1.25 TYP.

Rounds 8, FILLets: R.S

2X01.0

mi.25

4. Indexing Base (Dimensions are in inches.)

RE.OOR4.00

R6.QG

R3.25

31.50

R3.00


5. Guide Block (Create the front view of the design. Dimensions are in inches.)


Notes:

chapter 3 geometric construction and editing...

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