ORTHOGRAPHIC DRAWING

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Agus Arsad, Azizul Azri Bin Mustaffa

ENGINEERING DRAWING

SKKK 1021

LEARNING OUTCOMES

It is expected that students will be able to:

• Identify the significance and application

of the orthographic drawing

• Apply the techniques of orthographic

drawing

• Using the techniques for spacing out

drawing

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ORTHOGRAPHIC DRAWING

• INTRODUCTION

• SIGNIFICANCE AND ITS APPLICATION

• BASIC THEORY

– FIRST ANGLE PROJECTION

– THIRD ANGLE PROJECTION

• TECHNIQUES FOR SPACING OUT

DRAWING

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INTRODUCTION

• Orthographic projection

o A method to show real shape of an object on a

certain plane

o Projection Plane - plane where the object were

projected

o View Direction – Viewer location from the object

o Three Projections – Front, adjacent and plan/top

view

o Every plane is perpendicular to each other

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SIGNIFICANCE & APPLICATION

• In this chapter – transfer the isometric

object to orthographic drawing and

complete the drawing with projection

lines.

• Orthographic projection is a means of

representing a three-dimensional (3D)

object in two dimensions (2D).

• Combination of these 2D shapes will

produce complete info of a component

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ENGINEERING THE RESOURCES

MULTIVIEW PROJECTION

Three principle dimensions of an object …

Width Depth

Height

Width

He

igh

t

Depth

De

pth

… can be presented only two in each view.

Adjacent view(s)

is needed to

fulfill the size description.

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ENGINEERING THE RESOURCES

REVOLVE THE OBJECT

Front view Right side view

Top view

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PROJECTION SYSTEMS

1. First angle system

2. Third angle system

First Quadrant

Third Quadrant

- European country

- ISO standard

-Canada, USA,

Malaysia, Japan,

Thailand

BASIC THEORY

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ORTHOGRAPHIC PROJECTION

1st angle system 3rd angle system

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ORTHOGRAPHIC VIEWS

1st angle system 3rd angle system

Folding line

Folding line

Folding line

Folding line

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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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ENGINEERING THE RESOURCES

OBSERVER MOVE AROUND

Front view Right side view

Top view

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THE GLASS BOX CONCEPT

Bottom view

Left side view

Rear view

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Height

Width

De

pth

History

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OBJECT FEATURES

Edges are lines that represent the boundary

between two faces.

Corners Represent the intersection of two or

more edges.

Edge

Corner

Edge No edge

No corner No corner

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Surfaces are areas that are bounded by edges

or limiting element.

Limiting

element

is a line that represents the last visible

part of the curve surface.

Surface Surface Surface

Limit Limit

OBJECT FEATURES

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A

B

PROJECTION OF POINT(S)

AF

BR

AT

BF AR

BT

AF AR

AT

BF BR

BT

Equal distance

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NORMAL LINE

A

B

AF BF BR AR

AT

BT

BR

AR

AF BF

AT

BT

True length

True length Point

Equal length

PROJECTION OF LINE

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INCLINED LINE

A B

AF BF BR AR

AT

BT

Foreshortened

BR

AR

AF

BF

Foreshortened

AT

BT

True length

A

Equal length

PROJECTION OF LINE

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OBLIQUED LINE

A B

AF

BF BR

AR

AT

BT

A

Equal length

B

Foreshortened Foreshortened

Foreshortened

BR

AR

AF

BF

AT

BT

PROJECTION OF LINE

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PROJECTION OF PLANE

NORMAL PLANE

B C

A

BF AF,CF CR AR,BR

AT

CT

Equal length

Edge Edge

True size

CR

AR,BR

AF,CF

BF

AT

BT

CT

BT

10/2/2012 24 INCLINED PLANE

B C

BF AF

CR

AR,BR

AT

CT

A

Equal length

BT

C

CF

Edge

CR

AR,BR

Foreshortened

BT

CT

AT

AF

CF

Foreshortened

BF

PROJECTION OF PLANE

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OBLIQUED PLANE

B C

BF

AF

CR

AR

AT

CT

A

Equal length

BT

C

CF

B

BR

Foreshortened

CR

AR

BR

AF

BF CF

Foreshortened

AT

BT

CT

Foreshortened

PROJECTION OF PLANE

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PROJECTION OF OBJECT

The views are obtained by projecting all

object features to the picture plane.

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s

s

s

PROJECTION OF OBJECT

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PROJECTION OF OBJECT

TECHNIQUES FOR SPACING OUT

DRAWING

• Things to consider

o Selection of the front view

o Selection of the adjacent view

o Method to space out drawing

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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.

Select a Front View

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Select a Front View

Choose the view that have the fewest number of hidden lines.

GOOD Inappropriate

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Select an Adjacent View

GOOD

Inappropriate

Inappropriate

GOOD

Choose the view that have the fewest number of hidden lines.

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Choose the minimum number of views that can represent the major features of the object.

Select an Adjacent View

Necessary

Necessary

Hole’s location can be specified on the same view.

Difficult to interpret.

Easy to understand

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Choose the views that are suitable to a drawing

space.

Select an Adjacent View

POOR

Not enough space

for dimensioning.

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Choose the views that are suitable to a drawing

space.

Select an Adjacent View

GOOD

Method to space out drawing • Before starting the orthographic drawing,

the drawing space must be divided by

determining the space for front, adjacent and

plan view.

• The space can be divided as follows:

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B = 285 – A – P – L ______________________________________________________________________________________________________________

2

C = 175 – A – L – T - ______________________________________________________________________________________________________________

2

Method to space out drawing (cont’d)

• The drawing space is divided into four quarters

(one quarter-45 degrees line – reflection

reference)

• The visible lines are drawn 10 mm from the

dividing lines

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Method to space out drawing (cont’d)

• Projection lines

o Used as guide lines to produce the drawing

o Projected from one edge to another in the other view

o Drawn at a length more than the edge of an object

o Intersections of this line will produce sides of an

object

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WRITING STEPS

1. Select the necessary views

2. Layout the views.

3. Project the views.

4. Dimension the views.

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END

OF

CHAPTER 4

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