Computer Aided Design -Lecture 03

8/2/2019 Computer Aided Design -Lecture 03

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COMPUTER AIDED DESIGN

LECTURE 03

DRAWING OBJECTS

ENGR. ASSAD YOUSAFZAI



CONTENTS

1. STARTING NEW DRAWING

2. USER COORDINATE SYSTEM

3. SNAP & GRID FUNCTIONS

4. POLAR TRACKING FUNCTION

5. ORTHO TRACKING FUNCTION

6. DEFINING UNITS AND PRECISIONS

7. DRAWING LINES

8. CONSTRUCTION LINES

9. RAY (UNI-DIRECTIONAL CONSTRUCTION LINES)



STARTING A NEW DRAWING

START MENU PROGRAM AutoDesk AutoCAD 20xx

Select Acad.dwt template in start up dialog box

If the startup dialog box doesn’t appear,

Click on Tools Options System Select

“Show Start Up dialog box” from the Start Up drop down menu

Ensure that Grid, Snap and Model buttons on task bar are turned ON.



COMMAND LINE WINDOW

&

UNITS AND THEIR PRECISION

Command Window:

Command line window appears below the main screen and above the taskbar

Commands are entered through keyboard

Function key F2 toggles the display of maximized Command Windowshowing all commands entered

Units and Precisions:

Command: Units

Used to select unit types and precisions



User Coordinate System

Default UCS (World)

Defining New UCS

Command: Type ucs and press enter to get options

You may change the move UCS, define new UCS, Save UCS and much more options

To get back the default UCS

Command: UCS & press enter

Type world or only W and press enter

Static vs Dynamic UCS

Using function key F6 to switch between static and dynamic UCS



Snap & Grid

Grid

Set of evenly spaced, visible dots

Serve as a visual distance reference.

The grid (by default) also indicates how far the drawing limits extend.

Default Grid is Half a unit apart (0.500 unit)

Press Function Key F7 to turn default Grid on

May be customized through;

Grid command OR

Right click on Grid tab and selecting settings



Snap & Grid

Command: grid

Specify grid spacing (X) or [ON/OFF/Snap/Aspect] <0.5000>:

Options:

1. Type ON and press Enter to turn default Grid On (OR)

2. Simply Enter to select a default (half unit grid)

3. Type a numerical value say 2 and press Enter to select 2 x 2 unit grid

4. Type Snap or only S and press enter adjust Grid = Snap

5. Type Aspect or only A to select vertical and horizontal grid spacing differently



Snap & Grid

Snap

Creates a set of evenly spaced, invisible hot spots

M akes the crosshairs/Cursor move in even increments (verify from UCs)

Press Function Key F9 to turn default Snap on

May be customized through;

Snap command OR

Right click on Snap tab on task bar and selecting settings

Model Space



Snap & Grid

Command: snap

Specify snap spacing or [ON/OFF/Aspect/Rotate/Style/Type] <0.5000>:

Options:

1. Press Enter to select default snap =0.5000 units

2. Type Aspect or only A and press Enter to select horizontal and vertical snapspacing separately

3. Type Rotate or only R to change direction of snap to some other angle

4. Snap Style can be standard or isometric

5. Snap Type is either polar or grid (See Polar Snaps in coming slides)



Drawing Lines

Command: LINE

Specify first point: (pick P1=1,1) Specify next point or [Undo]: (pick P2 =9,9)

Specify next point or [Undo]: (Enter to end)

________________________________________

Command: LINE

Specify first point: 1,1 Specify next point or [Undo]: @8,8


________________________________________

Command: LINE

Specify first point: (pick P1=1,1)Specify next point or [Undo]: @9.8994<45


________________________________________



Drawing Lines

Direct Distance Entry Method:

Command: LINE

Specify first point: (pick P1=1,1)

Move the cursor diagonally to select the direction of next point (45o)

Enter the length of the line through keyboard (9.8994) and press Enter

ERASE:

Click on line segment, Right Click and erase or press e andenter



Drawing Construction Lines

Line of infinite length which passes through two picked points

Very useful for creating construction frameworks or grids within which to design.

They are not used in finished drawing therefore kept in separate layer to remove later

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Command: XLINE

Specify a point or [Hor/Ver/Ang/Bisect/Offset]: (pick a point)Specify through point: (pick a second point)Specify through point: (Enter to end or pick another through point)

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Options in XLINE Command

Hor- To draw Horizontal Construction Lines

Ver- To draw Vertical Construction Lines Ang- To draw Angular Construction Lines

Bisect- To bisect/divide an angle into two equal parts

Offset- To draw a construction Line parallel to some object side or surface



RAY Command

Construction line that extends only in one direction from the 1st pick point

Direction of extension is specified by second pick point

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Command: RAY Specify start point: (pick the start point)Specify through point: (pick a second point to determine direction)Specify through point: (Enter to end or pick another point)

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Ortho Tracking (F8), Polar Tracking (F10) & Polar Snap functions

While creating or modifying objects in AutoCAD, tracking techniques are used todisplay temporary alignment paths (Polar Angles) and distances along these paths(Polar Distances).

Ortho tracking is used to specify/display alignment paths along orthogonal polesonly i.e. polar angles of 0, 90, 180, 270 and 360 degree (Practice Example 1)

(F8 Toggles Ortho Function On/Off)

Polar Tracking can be used to specify a variety of polar angles and thus displaytemporary alignment paths to help easier different angles specification

F10 function key toggles Polar Tracking On/Off

Polar Snap is used to track/specify polar distances along selected polar angles



Example 1

Drawing Rectangle with lines using ortho function

Turn Ortho function ON by clickingon Ortho button on task bar or bypressing F8

Invoke Line command and click on

screen to pick a starting point as 3,3

Move the cursor around the pointand notice that it will show atemporary alignment line along 4orthogonal poles

Move the cursor along 0 degreepole to Pick another point 6,3

Repeat the process to draw theshown rectangle

(3,3)

6,9

(6,3)

(3,9)

Practicing OrthoFunction



Example 2

Practicing Polar Tracking

Right click Polar button on task bar and go tosettings

Set increment angle to 45o

Click on screen to pick a point P1

Move the cursor around and notice that the atool tip showing current angle and the polardistance appears as the cursor crosses every45 degree angular increment

Pick another point P2 at 90 degree angle withP1

Again move the cursor around P2 to selectpolar angle of 225 degree

Drop a line at point P3 on Horizontal Axisalong this polar angle of 225 degree toconstruct the shape as shown

90o

225o

P1

P2

P3

P1

P2

P3



Example 3

Using Polar Snap

Right click on Polar button and go tosettings

Turn on Polar Tracking

Set increment angle to 30

Right click snap and go to settings

Check the Snap On box

Select Polar Snap

Set polar distance to 1.000 unit

Draw the parallelogram as shown infigure

20”

20”

12” 12”

30o

180o210o

0o



AutoCAD Commands

Circle

Rectangle

Linear dimensioning



Practice Exercises

Draw a line from (3,2) to (4,8) using key board only

Draw a line from (6,6) to (7,5) using mouse only

Draw a line from (6,6) to (12,12) by direct distance

method Undo all the lines drawn

Draw a square with corners (2,2), (7,2), (7,7) & (2,7)

Erase this square using the erase command



Practice Exercises

Design GRATE

Design SHIM

Design STAMP

Design TILE

Polygon



Exercises Draw the following Octagon using Line Command

Each side length = 8 units

Angles increment by 45o

The bottom right corner lies at point(4,5)

(4,5)

Computer Aided Design -Lecture 03

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