EG presentation 3 unit 2 Projection of Points & Lines

ERODE SENGUNTHAR ENGINEERING COLLEGE
(An Autonomous Institution)
(Approved by AICTE, New Delhi, Permanently Affiliated to Anna University, Chennai&
Accredited by National Board of Accreditation (NBA), New Delhi,
National Accreditation Assessment Council, Bangalore)
PERUNDURAI, ERODE - 638 057
DEPARTMENT OF MECHANICAL ENGINEERING
Presented by,
Dr.J.BALAJI., M.E., Ph.D
Associate Professor
Department of Mechanical Engineering
Erode Sengunthar Engineering College
Perundurai, Erode 638051.

UNIT-2 PROJECTION OF POINTS AND LINES
SYNOPSIS
1. ORTHOGRAPHIC PROJECTION
I. DEFINITION
II. TERMINOLOGIES
III. FIRST ANGLE AND THIRD ANGLE PROJECTION
IV. MODEL PROBLEMS
2. PROJECTION OF POINTS
I. INTRODUCTION
II. ORTHOGRAPHIC PROJECTION OF POINTS
III. MODEL PROBLEMS
3. PROJECTION OF LINES
I. INTRODUCTION
II. ORTHOGRAPHIC PROJECTION OF LINES
III. MODEL PROBLEMS

1. ORTHOGRAPHIC PROJECTION
I. DEFINITION OF PROJECTION
A projection is defined as an image or drawing of an object made on a plane.
(OR)
It is representation of the image of an object on a plane surface, as it is observed by a viewer.

I.DEFINITION OF ORTHOGRAPIC PROJECTION
Orthographic projection is a means of representing three dimensional objects in two
dimensions. It is a form of parallel projection, where all the projection lines are orthogonal
to the projection plane, resulting in every plane of the scene appearing in affine
transformation on the viewing

II. TERMINOLOGY
1. PLANE OF PROJECTION
A plane of infinite thickness and transparent on which the projection of an object is drawn is know as
plane of projection.
2. OBJECT
A body for which the projection are to be drawn as object. The object may be of a machine building
(or) any body composed by a number of solids.
2. OBSERVER
The person looking for the projections of an object is known as observer.
3. PROJECTORS
The projection of an object is drawn by means of a straight lines called visual rays. These lines or
rays visualized by the observer, parallel to each other and perpendicular to the plane are called as
projectors.

II. TERMINOLOGY
5. PLANES
A planes which is kept draw a various views of an given object by projection is know as planes.
(i) Horizontal Plane
(ii)Vertical Plane
(iii)Profile Plane
6. VIEWS
(i) Front View
(ii) Top View
(iii) Side View
(a) Right side view
(b) Left side View

TYPES OF ORTHOGRAPHIC PROJECTION
according to the position of the object and the position of planes the orthographic projection are classified
into two groups such as,
(i) First angle Projection
(ii) Third angle Projection

S.No First Angle Projection Third Angle Projection
1 The object is placed in first quardrant.ie.,
above HP & in front of VP
The object is placed in third quardrant.ie., below
HP & behind of VP
2 Object is in between the plane and observer Plane is in between the object and the observer
3 Front is drawn above the reference line. Front is drawn below the reference line.
4 Top view is arranged vertically below the
front view
Top view is arranged vertically above the front
view.
5 Side view is horizontally aligned with the
front view. But left side view is drawn on
the right side of the front view and the right
side view is drawn on the left side of the
front view.
Side view is horizontally aligned with the front
view. But left side view is placed on the left side
of the front view and the right side view is
placed on the right side of the front view.
6

FIRST ANGLE PROJECTION THIRD ANGLE PROJECTION

IV. MODEL PROBLEMS
PROBLEM:1 Draw the Orthographic projection of a given isometric view.

IV. MODEL PROBLEMS

2. PROJECTION OF POINTS
 First quadrant -- Above HP & in front ofVP
 Second quadrant -- Above HP & behind ofVP
 Third quadrant -- Below HP & behindVP
 Fourth quadrant -- Below HP & in front of VP

PROJECTION OF POINTS IN DIFFERENT QUADRANTS

MODEL: 1 Mention the position of the following points with respect to the planes of
Projections. All dimensions are marked in mm
 Point A 20 mm above HP and 30 mm behind of VP
 Point B 20 mm below HP and 25 mm in front ofVP
 Point C 25 mm below HP and 30 mm behind VP
 Point D 30 mm below HP and in VP
 Point E 25 mm above HP and 20 mm in front ofVP

MODEL: 2 Draw the projections of the following points on a common reference. Take 30
mm distance between the projectors.
 Point A 35mm above HP and 25mm in front of VP
 Point B 40 mm below HP and 15mm behind VP
 Point C 50 mm above HP and 25mm behind VP
 Point D 45 mm below HP and 25mm behind VP
 Point E 30 mm behind VP and on HP

3. PROJECTION OF LINES
I. INTRODUCTION
DEFINITION: A straight line may be defined as the locus of a point which moves along the shortest
path joining two given points. A straight line may also be defined as the locus of a point which moves
linearly. Thus two ends of a straight line are points. Therefore projection of a straight line can be
drawn by joining the respective projections of its end points
POSITION OF LINES IN THE PLANE
(i) Line parallel to both VP and HP
(ii) Line Parallel to HP & Perpendicular to VP
(iii) Line Parallel to VP & Perpendicular to HP
(iv) Parallel to HP & Inclined to VP
(v) Parallel to VP & Inclined to HP
(vi) Line inclined to both VP and HP

i. Line Parallel to VP and HP
(ii) Line Parallel to HP and Perpendicular
to VP

(iii) Line Parallel to VP and
Perpendicular to HP
(iv) Line Parallel to VP and
Inclined to HP

(v) Line Parallel to HP and
Inclined to VP
(vi) Line inclined to both
HP & VP

Important Terms (Line inclined to both HP & VP)

MODEL PROBLEM
1) A line PQ, 80 mm has its end P, 20 mm above the HP and 30 mm in front of the VP. It is inclined at
30° to the HP and 45° to the VP. Draw its projections.

EG presentation 3 unit 2 Projection of Points & Lines

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EG presentation 3 unit 2 Projection of Points & Lines