lecture iv orthographic writing
DESCRIPTION
TRANSCRIPT
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Engineering Drawing ILecture – IVOrthographic WritingHafiz Ahmad Ashfaq
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TOPICS
Views selection
Alignment of views
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View Selection
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VIEW SELECTION STEPS
1. Orient the object to the best position
relative to a glass box.
2. Select the front view.
3. Select adjacent views.
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STEP 1 : Orient the Object
The object should be placed in its natural position.
NO !
The object should presents its features in actual
size and shape in orthographic views.
GOOD
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STEP 2 : Select a Front View
The object’s longest dimension should be
presented as a width.
Inappropriate
First choice
GOOD
Second choice
Waste more space
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Inappropriate
The adjacent views that are projected from the
selected front view should appear in its natural
position.
STEP 2 : Select a Front View
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STEP 2 : Select a Front ViewChoose the view that have the fewest number ofhidden lines.
GOOD Inappropriate
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STEP 3 : Select an Adjacent View
GOOD
Inappropriate
Inappropriate
GOOD
Choose the view that have the fewest number ofhidden lines.
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Choose the minimum number of views that can represent the major features of the object.
STEP 3 : Select an Adjacent View
Necessary
Necessary
Hole’s location can be specified on the same view.
Difficult to interprete.
Easy to understand
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Choose the views that are suitable to a drawing
space.
STEP 3 : Select an Adjacent View
POOR
Not enough spacefor dimensioning.
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Choose the views that are suitable to a drawing
space.
STEP 3 : Select an Adjacent View
GOOD
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Example : View selection
Shape description
Size description
F.V.
W D
W
H
D mislead to…
F.V. & T.V. Three views F.V. & R.S.V.
H
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ONE-VIEW DRAWING
Flat part having a uniform thickness.
Unnecessary These 2 views provide only informationabout the part thickness !
1 Thick
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ONE-VIEW DRAWING
Cylindrical-shaped part.
Unnecessary
Repeat !
Infer from CL
Unnecessary
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TWO-VIEW DRAWING
There exists an identical view.
Repeat !
Unnecessary
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The 3rd view has no significant contours of the object.
TWO-VIEW DRAWING
Unnecessary
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TWO-VIEW DRAWING
Unnecessary
The 3rd view has no significant contours of the object.
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Alignment of Views
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PROJECTION SYSTEMS
1. First angle system
2. Third angle system
First Quadrant
ThirdQuadrant
- European country
- ISO standard
- Canada, USA,
Japan, Thailand
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ORTHOGRAPHIC PROJECTION
1st angle system 3rd angle system
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ORTHOGRAPHIC VIEWS
1st angle system 3rd angle system
Foldingline
Foldingline
Foldingline
Foldingline
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ORTHOGRAPHIC VIEWS
1st angle system 3rd angle system
Front View
Front View
Right Side View
Right Side View
Top View
Top View
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First angle system Third angle system
PROJECTION SYMBOLS
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PROJECTION SYMBOLS
d 1.7d
2.2d
Suggested proportion
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QUIZ
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1. Which should be the natural position of the light bulb ? (20 sec)
c)
b)a
d)
5 10 15 200
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A
B
C
D E
F
2. Which are the necessary views ? (60 sec)
a) A-C-E
b) E-B-D
c) E-A
d) E-C
15 30 45 600