Practical work 3

EC202-Computer Aided Design

amy/khk/jke/puo EC3.1

PRACTICAL EVALUATION FORM

NAME:………………………………………………………. CLASS.: ………………

REGISTRATION NO.: ………………………………………

PRACTICAL WORK: 3

APPLICATION OF AUTOCAD PACKAGE IN TECHNICAL AND ELECTRICAL

DRAWINGS: THE DRAW COMMANDS AND DRAWING AID COMMANDS

No.

Skill

i. Accuracy

ii. Within time frame

Excellent

(8-10 marks)

Average

(5-7 Marks)

Weak

(0-4 Marks) Total

1. Part A: Setting A4 Metric

measurement

2. Part E: Exercise

Sub-Total /20

No. Report Total

1. Discussions /10

2 Questions /8

3. Reflection /2

Sub-Total /20

Total /40



PRACTICAL WORK: 3

TITLE : APPLICATION OF AUTOCAD PACKAGE IN TECHNICAL AND

ELECTRICAL DRAWINGS

COURSE LEARNING OUTCOME:

CLO4: Apply the draw and edit commands skillfully to produce simple and

complex technical drawings.

OBJECTIVES: The students should be able to:

1. Set the drawing limits before starting to draw.

2. Draw objects by using the Drawing Commands such as Line, Arc, Circle,

Ellipse, Polygon, Point, Polyline, Solid and Doughnut.

3. Select Drawing Aids Commands such as Snap, Ortho, Grid and Object

Snap for precision of drawing.

4. Create shapes and specifications applied in drawings by using the

Drawing Commands and Drawing Aids commands

THEORY :

Drawing Limits is used to define the extent of the grid display and to toggle Limits mode

which can be used to define the extent of your drawing. The grid is displayed within a

rectangle defined by two pick points or co-ordinates.

Draw commands is a fundamental to the efficient use of AutoCAD. In common with most

AutoCAD commands, the Draw commands can be started in several ways by:

i. Selecting the <DRAW> commands from the Pull-Down Menu <DRAW>

ii. Selecting the require icon tools from the Toolbar <DRAW>

iii. Typing names or shortcuts entered at the keyboard and press [Enter]



Drawing Aids commands such as the SNAP, GRID and ORTHO mode buttons which can be

seen at the Status Bar and the Object Snap Toolbar are analogous to traditional drafting

tools. Just as you have a parallel motion and set squares to help you draw horizontal and

vertical lines on a drawing board, AutoCAD has similar drawing aids which can help you to

draw horizontal and vertical lines on a computer.

EQUIPMENT : 1. Desktop Computer/Laptop

2. AutoCAD 2004 Software

PROCEDURE :

Part A: Start the AutoCAD program

1. Create a New drawing.

2. Set the drawing measurement to metric..

3. Display the grid to the extent of drawing limits.

Part B: Determining drawing limits

Drawing limits can be set according to the drawing requirements in either paper size A/B

/C/D etc. Table 1 shows the measurement units in metric and imperial (inches) for an A size.

.

Table 4.1: International paper size for ‘A’ series



Click at the Pull-Down Menu <FORMAT>

and select drawing limits.

Fig. 3.1: Pull Down Menu <FORMAT> drawing limits.

Notice the message displayed at the command prompt area:

Fig. 3.2: Message displayed at the Command Promp Area

You will be prompt to specify the lower left coordinates :

o In relation to the origin of the User Coordinate System (UCS)i.e. (0,0)

Press [Enter] to accept the default value of 0.0000,0.0000.

AutoCAD will prompts for the upper right corner:

o In metric measurement, AutoCAD default paper size is at A3 size and the

working area is in landscape mode.

o To set the upper right corner limits for A4 metric:

Type: 297,210 and press [Enter]

Notice the message displayed at the command prompt area:

Fig. 3.3: Message displayed at the Command Prompt Area



Click at the Bar Status <GRID> mode for grid display.

o AutoCAD will display a grid to the extent of the drawing limits specified.

Click the Pull-down menu <ZOOM> and select All.

Part C: Draw Commands

As stated earlier, Draw Commands can be started in one of these three ways:

i. Selecting the from the Pull-Down Menu <DRAW>

Fig. 3.4:Pull-down Menu <DRAW>

ii. Selecting the required icon from the Draw Toolbar

Fig. 3.5: Draw Toolbar

iii. Typing names or shortcuts entered at the keyboard (e.g. Line) and press [Enter]

Fig. 3.6: Entering draw commands through Keyboard

1. Drawing Line Objects

With the <line> command, you can draw a simple line from one point to another. After

selecting the first point and dragging the cursor to the second location, you will see a

rubber band line showing where the line will be drawn when the second point is picked.



Line objects have only two ends i.e. the first and last points. Continue picking the points

and AutoCAD will draw a straight line between each picked point and the previous

picked point.

Toolbar Draw

Pull-down Draw Line

Keyboard LINE short-cut L

Draw a line by following the instructions below:

Command: Line

Specify first point or [Close/Undo]: <pick point P1>…

(by using coordinate formulas system…etc.)

Specify next point or [Close/Undo]: <pick point P2>

Specify next point or [close/Undo]: to end

2. Drawing Rectangles

The Rectangle command is used to draw a rectangle whose sides are vertical and

horizontal. The position and size of the rectangle are defined by picking two

diagonal corners. The rectangle isn't really an AutoCAD object at all. It is, in fact,

just a closed polyline which is automatically drawn for you.

Draw a Rectangle by following the instructions below:

Command: Rectangle

Specify first corner point or

[Chamfer/Elevation/Fillet/Thickness/Width]:<pick point P1>

Specify other corner point or [Dimensions]: <pick point P2>

Toolbar Draw

Pull-down Draw Rectangle

Keyboard RECTANGLE short-cuts REC, RECTANG



This method provides a good alternative to using relative cartesian coordinates for determining length and width.

Notice that, instead of picking a second point to draw the rectangle, you have the

option of entering dimensions. For example, draw a rectangle 20 units long and 10

units wide. The command sequence would look like this:

Command: Rectangle

Specify first corner point or

[Chamfer/Elevation/ Fillet/Thickness/Width]:

(pick point P1)

Specify other corner point or [Dimensions]: @20,10

3. Drawing Arcs

The Arc command allows you to draw an arc of a circle. There are numerous ways to

define an arc; the default uses three pick points: a start point, a second point and an end

point. Using this method, the drawn arc will start at the first pick point, pass through the

second point and end at the third point. You may, for example, need to draw an arc with

a specific radius. All of the Arc command options are available at the Pull-Down menu.

Toolbar Draw

Pull-down Draw Arc 3 Points

Keyboard ARC short-cut A

Draw an arc by following the instructions below:

Command: Arc

Specify first point of arc or [Center]: <pick point P1)>

Specify the second point or [Center/End]: <pick point P2>

Specify end point or arc: <pick point P3>

It is possible to create an arc by trimming a circle object. In practice, many arcs

are actually created this way.



4. Drawing Circles

The Circle command is used to draw circles. There are a number of ways you can define

the circle. The default method is to pick the centre point and then to either pick a second

point on the circumference of the circle or enter the circle radius at the keyboard.

Toolbar Draw

Pull-down Draw Circle Center, Radius

Keyboard CIRCLE short-cut C

Draw a circle by following the instructions below:

Command: Circle

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

(pick point P1)

Specify radius of circle or [Diameter] <0.0>: (pick point P2 or

enter the exact radius value)

At the command prompt, the circle command gives you three extra options to define

a circle; 3P which uses any three points on the circumference, 2P which uses two points

on the circumference to form a diameter and TTR which stands for Tangent, Tangent,

Radius.

5. Drawing Ellipse

The Ellipse command gives you a number of different creation options. The default

option is to pick the two end points of an axis and then a third point to define the

eccentricity of the ellipse.

Toolbar Draw

Pull-down Draw Ellipse Axis, End

Keyboard ELLIPSE short-cut EL



Draw the ellipse by following the instructions below:

Command: Ellipse

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

(pick point P1)

Specify other endpoint of axis: (pick point P2)

Specify distance to other axis or [Rotation]: (pick point P3)

6. Drawing Polygon

The Polygon command can be used to draw any regular polygon from 3 sides up to 1024

sides. This command requires four inputs from the user, the number of sides, a pick

point for the centre of the polygon, whether you want the polygon inscribed or

circumscribed and then a pick point which determines both the radius of this imaginary

circle and the orientation of the polygon. The polygon command creates a closed

polyline in the shape of the required polygon.

This command also allows you to define the polygon by entering the length of a side

using the Edge option. You can also control the size of the polygon by entering an exact

radius for the circle.

Toolbar Draw

Pull-down Draw Polygon

Keyboard POLYGON short-cut POL

Draw the Polygon by following the instructions below:

Command: Polygon

Enter number of sides <4>: 5

Specify center of polygon or [Edge]: (pick P1 or type E to define by edge length)

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

accept the inscribed default or type C for circumscribed)

Specify radius of circle: (pick point P2 or enter exact radius value)



7. Drawing Point

The point command will insert a point marker in your drawing at a position which you

pick in the drawing window or at any co-ordinate location which you enter at the

keyboard. The default point style is a simple dot, which is often difficult to see but you

can change the point style to something more easily visible or elaborate using the point

style dialogue box. Points can be used for "setting out" a drawing in addition to

construction lines. You can Snap to points using the Node object snap.

Toolbar Draw

Pull-down Draw Point Single Point

Keyboard POINT short-cut PO

Draw a point by following the instructions below:

Command: Point

Current point modes: PDMODE=0 PDSIZE=0.0000

Specify a point: (pick any point)………….If the symbol doesn’t appear on the points

specified, you need to change the point size.

To change the point size, do the following:

From the Pull-Down menu <FORMAT> select Point

Style.

o A dialogue box appears on the screen and make

the selection required.

Fig.3.7: Format Point Style



8. Drawing the POLYLINE

The Polyline or Pline command is similar to the line command except that the resulting

object may be composed of a number of segments which form a single object. In

addition to the two ends a polyline is said to have vertices (singular vertex) where

intermediate line segments join. In practice the Polyline command works in the same

way as the Line command allowing you to pick as many points as you like. Again, just

press to end.

As with the Line command, you also have the option to automatically close a polyline

end to end. To do this, type C to use the close option instead of pressing

a. Draw a Polyline by following the instruction below:

Command: Pline

Specify start point: (pick point P1)

Current line-width is 0.0000

Specify next point or [Arc/Halfwidth/Length/Undo/Width]: (pick point P2)

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: (pick point P3)



Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: (or C to close)

Toolbar Draw

Pull-down Draw Polyline

Keyboard PLINE short-cut PL

In the illustration on the right,

the figure on the left was

created by hitting the key

after the fifth point was picked.

The figure on the right

demonstrates the effect of using

the Close option



b. Polylines are very handy in creating arrows.

Command: Pline

Specify first point: (pick P1)

Current line-width is 0.0000

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

Specify starting width <0.00>: 5

Specify ending width <5.00>: 5

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

the location of P2]

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

Specify starting width <0.00>: 20

Specify ending width <20.00>: 20

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

location of P3)

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width] (or C to closed)

9. Drawing Solid Objects

The solid command createas a fill in area of quadrilateral or triangular shapes. Two

endpoints or intersections are picked as a starting edge of the solid. Two additional

endpoints or intersections complete the opposite edge of the solid.

Toolbar Surfaces

Pull-down Draw Surfaces 2D Solid

Keyboard SOLID short-cut SO

Draw the Solid command by following the instructions below:

Command: Solid

Specify first point: <pick point P1>

Specify second point: <pick point P2>

Specify third point: <pick point P3>

Specify fourth point or exit: <pick point P4>



10. Drawing Donut

This command draws a solid donut shape; actually it's just a closed polyline consisting

of two arc segments which have been given a width. AutoCAD asks you to define the

inside diameter i.e. the diameter of the hole and then the outside diameter of the donut.

The donut is then drawn in outline and you are asked to pick the centre point in order to

position the donut. You can continue picking centre points to draw more donuts or you

can press to end the command.

Toolbar custom

Pull-down Draw Donut

Keyboard DONUT short-cut DO

Draw the Donut by following the instructions below:

Command: Donut

Specify inside diameter of donut <10.00>:

(determine the inside diameter value)

Specify outside diameter of donut <20.00>:

(determine the outside diameter value)

Specify center of donut or <exit>:

(determine the position for center of donut…e.g. point P1)

Specify center of donut or <exit>: (determine other points for more placement

of donut or press to end command)

TIPS:

Many of the draw commands require the key on the keyboard to be

pressed to end them. In AutoCAD, clicking the right mouse button and

selecting "Enter" has the same effect as using the key on the keyboard.

which is a much more efficient way of working than using the keyboard.

You can also use the key or right mouse click to repeat the last command

used. When a command has ended, you can start it again by right clicking

and selecting "Repeat command" from the context menu rather that entering

the command at the keyboard or selecting it from the pull-down or toolbar.



Part D: Drawing Aids Commands

Drawing Aids Commands can be selected through the:

a. Selection modes as in the Status Bar

Fig. 3.8: Drawing Aid modes at the Status Bar

b. Toolbar Object Snap

Fig. 3.9: Object Snap Toolbar

1. The Ortho Mode

Ortho is short for orthogonal, which means either vertical or horizontal. The Ortho tool

restricts drawing or editing movement in a drawing to the left/right or up/down

directions. When Ortho is toggled On , your lines will be drawn along the X- or Y-

plane. Like the other options on the status bar, Ortho is not really a command; it is a

drawing mode which can either be turned on or off.

Status Bar

Pull-down None

Keyboard ORTHO or F8

Command sequence:

Command: Ortho

Enter mode [ON/OFF] <OFF>: (type ON or OFF)

2. The Snap Mode

With Snap mode turned on AutoCAD only allows you to pick points which lie on a

regular grid. The Snap grid is completely independent of the display grid. However,



Grid spacing set to

10 drawing units

Grid spacing set to

5 drawing units

the Grid spacing and Snap spacing are usually set to the same value to avoid

confusion. When Snap mode is turned on and the Grid is displayed, the Snap and

Grid spacings are the same and the crosshairs will jump from one grid point to

another as you move across the screen..

Status Bar (right-click for settings)

Pull-down None

Keyboard SNAP or F9 Command sequence:

Command: SNAP

Specify snap spacing or [ON/OFF/Aspect/Rotate/Style/Type] <10.0000>: (enter

the required snap spacing in drawing units)

3. The Grid Mode

AutoCAD's grid is a set of evenly spaced, visible dots that serve as a visual distance

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

equivalent of having a sheet of graph paper behind your drawing on a drawing board.

You can control the grid spacing, so it can give you a general idea about the size of

drawn objects. It can also be used to define the extent of your drawing.

Status Bar (right-click for settings)

Pull-down None

Keyboard GRID or F7 Command Sequence;

Command: GRID

Specify grid spacing(X) or

[ON/OFF/Snap/Aspect] <10.000>: (enter

grid spacing)



The Snap option allows you to automatically set the grid spacing to the current snap

spacing. By default, the X and Y spacing of the Grid are the same, resulting in a regular

square matrix of grid points. But you can display a grid with different X and Y spacing

by using the "Aspect" option.

4. The Object Snap

The Object Snaps (Osnaps for short) are drawing aids which are used in conjunction

with other commands to help you draw accurately. Osnaps allow you to snap onto a

specific object location when you are picking a point.

Osnaps in AutoCAD are so important that you cannot draw accurately without them. For

this reason, you must develop a good understanding of what the Osnaps are and how

they work.

Follow the instructions below to create how Osnaps work:

Firstly, draw a circle:

Command: Circle

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

Specify radius of circle or [Diameter]: (specify the radius)

Next, draw a line:

Command: Line

Specify first point or [Close/Undo]: <pick point P1)>

Specify next point or [Close/ndo]: <pick point P2>

Specify next point or [close/Undo]: to end

To draw a line connecting the center of the circle to the midpoint of line P1P2 using

Osnap.

Command: LINE

Specify first point: CEN (this is the short-cut for the Center Osnap) of (pick any

point along the circle)

Specify next pointt: MID (this is the short-cut for the Midpoint Osnap) of (pick any

point along line P1P2

Specify next point: (to end)



You have now drawn a line from the exact centre of the circle to the exact midpoint

of the line. The line is drawn with perfect geometric accuracy.

PART E: EXERCISE :

1. Create a new drawing space using the Metric measurement.

2. Set the drawing limits to A4 paper size.

3. By referring to the dimensions and shapes given in Fig. 3.10, complete the diagram

as in Fig. 3.11.

4. Save the drawing file and exit AutoCAD.

Fig. 3.10: Shapes with Dimensions from <DRAW> commands



(2 Marks )

(2 Marks )

(2 Marks )

Fig. 3.11: Diagram constructed using the <DRAW> commands

DISCUSSIONS :

1. List 3 (three) selection modes of the Object Snap toolbar that you had used in the

above exercise and describe their functions.

a. ………………….

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b. …………………

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c. …………………

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(4 Marks )

(4 Marks )

(4 Marks )

(2 Marks )

2. Describe the steps to create the 7-sided polygon in the exercise above?

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QUESTION :

1. How do you set and display an A4 imperial paper size on the screen?

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2. Name the <Draw> commands used in the diagram:

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REFLECTION:

At the end of this practical work, I have learnt that:

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Practical work 3

Education

drawing commands

drawing limits drawing

drawing measurement

drawing aid commands

extent of drawing limits

autocad commands

drawing board

drawing requirements