EC202-Computer Aided Design
PRACTICAL EVALUATION FORM
NAME:………………………………………………………. CLASS.: ………………
REGISTRATION NO.: ………………………………………
PRACTICAL WORK: 5
APPLICATION OF AUTOCAD PACKAGE IN TECHNICAL AND ELECTRICAL DRAWINGS: CONCEPTS OF DIMENSIONING, LINETYPES AND TEXTSTYLES
No.
Skill
i. Accuracy
ii. Within time frame
Excellent
(8-10 marks)
Average
(5-7 Marks)
Weak
(0-4 Marks)Total
1.Setting drawing limits &
display grid to extent
2. Fig. 5.15 (Border)
3. Fig. 5.15 (Text)
4. Fig. 5.16
5. Fig. 5.17
6. Dimensioning Objects
Sub-Total /60
No. Report Total
1. Discussions /5
2 Questions /3
3. Reflection /2
Sub-Total /10
Total /70
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PRACTICAL WORK: 5
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. Make text by using the Text and DText command.
2. Change the properties of Text Styles.
3. Dimension objects by using the dimension command.
4. Make use of the Dimension style to set a suitable scale for geometry,
format and annotation.
5. Set different linetypes according to the drawing requirements.
THEORY :
The correct use of AutoCADs dimension tools is the key to producing clear and concise
measured drawings. Dimensioning in AutoCAD is automatic; lines, arrows and text are all
taken care of by the dimension commands.
When working with dimensions it is very important that line origins are picked accurately so
that the resulting measurement and text are correct. Always use an Osnap to pick dimension
line origins.
The illustration above shows two different dimension styles. The one on the left is the
default style known as STANDARD. The dimension line has arrow heads and the dimension
text is positioned above the line and is drawn using the current text style. The dimension on
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the right has been drawn using a new style. The arrows have been changed to obliques, the
vertical alignment of the text has been centred and the current text style has been changed.
EQUIPMENT : 1. Desktop Computer/Laptop
2. AutoCAD 2004 Software
PROCEDURE :
Part A: The Dimension Command
When you create dimensions, AutoCAD automatically creates a new layer called
"Defpoints". This is a special layer which cannot be deleted or renamed. AutoCAD uses this
layer to store dimension information.
The Dimension command can be started through any one of these three ways:
i. Click at the Pull-Down Menu <DIMENSION> and select the options
Fig. 5.1: Pull-Down Menu <DIMENSION>
ii. Toolbar Dimension
Fig. 5.1: Toolbar Dimension
iii. Accessed through the keyboard
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Fig. 5.3: Message displayed at the Command Promp Area
Dimensioning Principles
There are two basic principles to follow when you add dimensions to a drawing.
1. Assignment of more than one dimension to a feature should be avoided.
2. The reader of the drawing should not be required to do calculation in order to obtain
the dimension of the object.
Components of a Dimension
A dimension consists of four components:
1. A dimension value.
2. A dimension line that is parallel to the direction of the described object.
3. A pair of arrowheads.
4. A pair of extension lines projecting from the object to which the dimension refers.
i. There should be a small gap between the end of the extension line and the
object.
ii. The extension line should project a short distance away from the intersection
with the dimension line.
Fig. 5.4: Components of Dimension
The Linear Dimension Commands
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The Linear dimension commands are used to dimension along straight lines. There are five
linear dimension commands, namely: DIMLINEAR, DIMCONTINUE, DIMBASELINE,
DIMALIGNED and DIMROTATED. The DIMLINEAR command is probably the most
common dimension command you will use.
The Linear Dimension Command
After starting the command, specify the two points between which you want the dimension
to be drawn and pick a point to fix the position of the dimension line. You can use this
command to generate horizontal and vertical dimensions.
Toolbar
Pull-down Dimension Linear
Keyboard DIMLINEAR
Command Sequence
Command: DIMLINEAR
First extension line origin or press ENTER to select: (pick P1)
Second extension line origin: (pick P2)
Dimension line location (Mtext/Text/Angle/Horizontal/Vertical/Rotated): (pick a
point to position the dimension line, you will see the dimension rubber banding)
You may have noticed that the first prompt asks you to pick the first extension line origin or
to press the ENTER key. Pressing the Enter/Return key results in the following prompt:
Select object to dimension:
AutoCAD allows you to dimension an object simply by picking it.
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Dimensions will automatically adjust themselves to accommodate most situations. For
example, the illustration on the right shows what happens to a dimension if the gap between
the two extension lines is too small for the dimension text.
The Continue Dimension Command
The Continue command adds a string of dimensions.
Toolbar
Pull-down Dimension Continue
Keyboard DIMCONTINUE
Command Sequence:
Command: DIMCONTINUE
Specify a second extension line origin or (Undo/<Select>): (pick P3)
Specify a second extension line origin or (Undo/<Select>): (pick another or to
End
The first dimension (P1P2) was drawn with the DIMLINEAR command; all the other
dimensions were drawn using the DIMCONTINUE command by simply picking the four
points, P3, P4, P5, P6 one after the other.
The Baseline Dimension Command
This command generates a series of dimensions from a single base point. The first
dimension is created with the DIMLINEAR. The DIMBASELINE command then creates
further dimensions in a similar way to the DIMCONTINUE command.
Toolbar
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Pull-down Dimension Baseline
Keyboard DIMBASELINE
Command Sequence:
Command: DIMBASELINE
Specify a second extension line origin or (Undo/<Select>): (pick next point)
Specify a second extension line origin or (Undo/<Select>): (pick another or to
end)Select base dimension: ( again to end)
The first dimension P1P2 was created using the DIMLINEAR command. The others were
created using DIMBASELINE by picking points P3 and P4.
The Aligned Dimension Command
These are dimensions along inclined lines which cannot be dimensioned with the
DIMLINEAR dimension command because that command will only give a measured
dimension in either a horizontal or vertical direction.
Toolbar
Pull-down Dimension Aligned
Keyboard DIMALIGNED
Command Sequence
Command: DIMALIGNED
First extension line origin or press ENTER to
select:(pick P1)
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Second extension line origin: (pick P2)
Dimension line location (Mtext/Text/Angle): (pick a point)
The DIMCONTINUE and DIMBASELINE commands can both be used in conjunction with
DIMALIGNED dimensions.
Changing the Text
The Text option allows you to enter a single line of text and the Mtext option starts the
MTEXT command and enables you to add formatted, multiline text to the dimension. These
options can be used to add descriptions to your dimensions or to modify the measured
distance.
In the example above, the Mtext option has been used to create a multi-line annotation.
When you use this option you will notice that the Multiline Text Editor dialogue already has
some text in the text window. This is the measured dimension and is displayed as "<>". If
you delete this marker the dimension measurement will not appear in the annotation.
If you need to edit dimension text after the dimension is drawn, you can use the DDEDIT
command or the Modify/Object/Text… from the pull-down. If you select a dimension, the
Multiline Text Editor will appear and you can make any necessary changes to the
annotation.
The Radial Dimension Commands
There are two main radial dimension commands,
DIMDIAMETER and DIMRADIUS. Both
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commands result in a similar looking dimension so AutoCAD automatically inserts a "R" to
indicate a radius and the dimension symbol to indicate a dimension.
The Diameter and Radius commands are supplemented by the DIMCENTER command
which can be used to add a center mark to any circle or arc. The DIMDIAMETER and
DIMRADIUS commands do not automatically draw a center mark.
By convention it is usual to dimension full circles using a diameter and arcs (partial
circles) using radius.
The Diameter Dimension Command
You can use the Diameter command to annotate a circle or an arc with a diameter
dimension.
Toolbar
Pull-down Dimension Diameter
Keyboard DIMDIAMETER
Command Sequence
Command: DIMDIAMETER
Select arc or circle: (pick the circumference P1)
Dimension line location (Mtext/Text/Angle): (move the
cursor until you are happy with the text position and
then pick to complete the sequence)
The Radius Dimension Command
The Radius command is identical to the Diameter command except that the dimension
measurement is a radius rather than a dimension and the resulting dimension text is prefixed
with a "R" to indicate radius.
Toolbar
Pull- Dimension Radius
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down
Keyboard DIMRADIUS
Command Sequence
Command: DIMRADIUS
Select arc or circle: (pick the circumference P2)
Dimension line location (Mtext/Text/Angle): (move the
cursor until you are happy with the text position and then
pick to complete the sequence)
Notice that in the illustration above the radius dimension has been positioned inside
the circle. Both diameter and radius dimensions can be positioned either inside or
outside an arc or circle.
The Angular Dimension Command
The Angular command is e used to indicate an angle in almost any situation.
Toolbar
Pull-down Dimension Angular
Keyboard DIMANGULAR
Command Sequence
Command: DIMANGULAR
Select arc, circle, line, or press ENTER: (pick a line)
Second line: (pick another line)
Dimension arc line location (Mtext/Text/Angle): (pick point)
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Move the cursor position until you are happy with the result. Notice that you can
move the cursor to either side of the lines and the angular dimension will change
accordingly.
The Leader Command
The Leader command is used to annotate any point on a drawing.
Toolbar
Pull-down Dimension Leader
Keyboard LEADER
Command Sequence
Command: LEADER
From point: (pick the point to annotate)
To point: (pick vertex point)
To point (Format/Annotation/Undo)<Annotation>:
(pick end point)
To point (Format/Annotation/Undo)<Annotation>:
Annotation (or press ENTER for options): Corner of
MText: building
MText: (to end)
Unlike other dimension commands the leader and annotation text are drawn as
separate objects. So, if you need to move or edit the text, you can do so without
affecting the leader line.
Dimension Styles
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Dimension styles are the main method used to control the way dimensions look. Using styles
you can change the text font, the arrow head style, the relative position of the text, the scale
of dimensions and many other parameters. Styles are created using the DIMSTYLE
command.
Toolbar
Pull-down Dimension Style…
Keyboard DDIM short-cut D
The Dimension Style command can be used to change the appearance of dimensions. The
best method is to create a new style before you start creating dimensions so that you can
leave the STANDARD style as a default option.
You can change styles such as: Linear, Radial, Angular, Diameter, Ordinate and Leader.
Fig. 5.5: Dimension Style Dialogue Box
The Dimension Update Command
The Dimension Update command is used to apply the current dimension style to existing
dimensions. You can use this command to change the style of a dimension. Unlike text
styles, dimension styles do not automatically update when the style is changed. The
UPDATE command must be used to force dimensions to appear in the current text style.
Toolbar
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Pull-down Dimension Update
Keyboard DIM UPDATE
Command Sequence:
Command: DIM
Dim: UPDATE
Select objects: (pick dimension to update)
Select objects: (pick more dimensions or to end)
Dim: (press the escape key, Esc to return to the command prompt)
Part B: The Text Command
Text can be added to an Autocad drawing to create notes and labels on your drawings. There
are two different text commands used to add text to drawings: Text and Mtext.
Text command can be started through:
i. Selecting Text from the Pull-down Menu
Fig. 5.6: Pull-Down Menu Selection <Text>
ii. Draw Toolbar
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Fig. 5.7: Draw Tolbar <A>
iii. Typing at the keyboard
Fig. 5.8: Keyboard entry
Text or Dtext or Single Line Text Command
It is a simple way to add basic text notes. The height and rotation of the text can be quickly
specified and the text can be viewed on the drawing while being typed.
a. Do the text command by following the instructions below:
Command: TEXT
Current text style: "Standard" Text height: 3.0000
Specify start point of text or [Justify/Style]: (pick a point)
Specify height <3.0000>:5 (enter the text height required)
Specify rotation angle of text <0>: (to accept the default)
Enter text: ELECTRICAL ENGINEERING DEPARTMENT
Enter text: POLITEKNIK UNGKU OMAR IPOH
Enter text:
Enter text: (exit text command)
Text displayed using the Single Line Text command.
Notice that each line is separately selectable and independent of the previous line. As each
line is separately editable, this text type is called single line text.
b. Do the following text command by following the instructions below;
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Create a rectangular measuring 150mm length and 15mm width.
Start the text or dtext command:
Current text style: "Standard" Text height: 3.7500
Specify start point of text or [Justify/Style]: J (selection for Justify)
Enter an option [Align/Fit/Center/Middle/Right/TL/TC/TR/ML/MC/MR/BL/BC/BR]:
F (selection Fit)
Specify first endpoint of text baseline: (pick point P1)
Specify second endpoint of text baseline: (pick point P2)
Specify height <3.0000>: 15
Enter text: POLITEKNIK UNGKU OMAR IPOH
Enter text:
Enter text: ( exit text command)
Text displayed using the Single Line Text Command justification
(The text is fixed accordingly to the height of the given box)
c. Do the following text command by following the instructions below;
Create another rectangular measuring 150mm length and 15mm width.
Start the text or dtext command
COMMAND: TEXT
Current text style: "Standard" Text height: 15.0000
Specify start point of text or [Justify/Style]: J (Selection for Justify)
Enter an option [Align/Fit/Center/Middle/Right/TL/TC/TR/ML/MC/MR/BL/BC/BR]:
F (selection for Fit)
Specify first endpoint of text baseline: _from Base point: <Offset>: @5,5
Specify second endpoint of text baseline: _from Base point: <Offset>: @-5,5
Specify height <15.0000>: 5
Enter text: POLITEKNIK UNGKU OMAR IPOH
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Enter text:
Enter text: (exit text command)
Text displayed using the Single Line Text Command justification
(Text is fixed accordingly to height of the text required)
d. Multiline Text
Multiline text is the more advanced text tool within Autocad. The multiline text command
has its own editor, with all the options available that you'd expect to see in a word
processing program. Also, all text on separate lines is treated together, so editing notes and
sentences is simple.
Do the Multiline command by following the instructions below:
Command: Mtext
Current text style: "Standard" Text height: 5
Specify first corner: (pick a point P1)
Specify opposite corner or [Height/Justify/Line spacing/Rotation/Style/Width]: (drag
the cursor and pick a point P2)
A multiline text editor appears on the screen.
Fig. 5.9: Multiline Text Editor
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When a text is entered into the multiline text editor, it will automatically start a
second line when it comes to the edge of the text box we specified. Its similar to
getting to the right hand margin in a text editor.
We can choose the font style, text height, also and also add symbols.
Press the ok button to place the text into the drawing (The text placement will be
justified as set in the properties-justification setting in the text editor.
Text in Autocad is treated like every other object, it can be rotated, mirrored, exploded,
moved layers etc.
Part C: The Linetype
When you first start AutoCAD, the default template has only one linetype is available. This
is the continuous linetype. AutoCAD has many more available, but only loads in one to start
with in order to keep the drawing file size smaller. If you need a different linetype, you must
load it into your current drawing
Instead of creating a new linetype (like you would a layer), you will have to LOAD it into
your drawing.
The linetype command can be started through:
i. Selecting the linetype at the Pull-down Menu <FORMAT>
A Linetype dialogue box appears on the screen.
Fig. 5.10: Pull-down menu Selection <Linetype>
ii. Object Properties Toolbar <By layer>
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Fig. 5.11:Object Properties Toolbar <By layer>
iii. Typing at the keyboard
Fig. 5.12: Keyboard command <linetype>
A Linetype Manager dialog box appear as in Fig. 5.11
Fig 5.13: A Linetype Manager dialogue box
Click the Load Button and a Load or Reload Linetypes dialogue box appears.
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Fig. 5.14: A Load or Reload Linetypes dialogue box
Notice that AutoCAD is giving you a choice of different linetypes as defined in the acad.lin
file. Scroll through the list to see what options you have available. You'll see the most
common ones (hidden, center, etc) as well as some that are only for certain applications.
Click on the Hidden linetype and then press OK.
Part D: EXERCISE
1. Create a new drawing space using the Metric measurement.
2. Set the drawing limits to A4 paper size.
3. Display the grid to the extent of the drawing limits.
4. Redraw all the figures in Fig. 5.15, Fig. 5.16 and Fig. 5.17 below.
5. Give dimensions to the figures drawn.
6. Save the drawing file and exit AutoCAD.
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Fig. 5.15
Fig.5.16
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Fig. 5.17
DISCUSSION:
1. What is the difference between Text Command and Mtext Command?
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2. Draw the symbols for these following linetypes:
a. Hidden line -
b. Center line -
c. Phantom line -
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QUESTIONS :
1. Why must you use the OSNAP points when making dimensions to an object?
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REFLECTION:
At the end of this practical work, I have learnt that:
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