13723_orthographic projection

Basics of Orthographic projections Basics of Orthographic projections byby

Pradip PatilPradip Patil

Department of Mechanical EngineeringLOVELY PROFFESIONAL UNIVERSITY,

JALANDHAR

1

Orthographic Projections2

PRADIP PATILASST. PROF. LPU

Drawing is the one of the language of communicating our views and ideas in the form of picture.

As like the all language this also have its grammar and own vocabulary .

Lines are the words for this language and set of lines forms the sentence which conveys the our idea .

So for that it is important to study the different types of lines used in drawing.

In engineering drawing, the word ‘projection’ means an image or the act of obtaining the image of an object.

3 PRADIP PATILASST. PROF. LPU

Types of line

LINES

Lines are like the alphabet of a drawing language. Each line in a drawing is used in a specific sense.

Pencil Grades

An H grade pencil is advised for THICK and MEDIUM lines. THIN lines may be drawn by a 2H grade pencil.

4




The projection system used in engineering drawing, is depicted in above Fig. The lines of sight of the observer create the view of the object on the screen. The screen is referred as plane of projection (POP). The lines of sight are called projection lines or projectors



7

Defining the Six Principal Views or Orthographic Views


8

Principal planes in drawing


9

The three RPs required to obtain the views in multi-view projections are the HP, the VP and the PP, in shown above Fig.

The HP and the VP make four quadrants.

The position of an object in space can be determined by these quadrants, i.e., the object can be in the first quadrant or in the second quadrant or in the third quadrant or in the fourth quadrant.

The line at which the HP and the VP meet is called horizontal reference line and denoted by XY.

The line at which the HP (or the VP) and the PP meet is called the profile reference line and is denoted by X1Y1.

After the views are obtained, the HP is rotated about XY in the clockwise direction to bring it in plane with the VP.

The PP is rotated about X1Y1 away from the object. PRADIP PATILASST. PROF. LPU

10

Front View When the observer looks at the object from the front, the view obtained is called the front view (FV) or Elevation. FV is seen on the VP.

Top View When the observer looks at the object from above, the view obtained is called top view (TV) or plan. TV is seen on the HP.

Side Views When the observer looks at the object from side, i.e., from his left-hand side or right hand side, the view obtained is called side view (SV). SV is seen on the PP.

Left-Hand Side View When the observer views the object from his left-hand side, the view obtained is called left-hand side view (LHSV).

Right Hand Side View When the observer views the object from his right-hand side, the view obtained is called as right-hand side view (RHSV).

Bottom View When the observer looks to the object from below, the view obtained is called bottom view (BV) or bottom plan.

Rear View When the observer looks to the object from back, the view obtained is called rear view (RV) or back view or rear elevation.

ORTHOGRAPHIC VIEWS


11

PROJECTION SYSTEMS

1. First angle system

2. Third angle system

First Quadrant

ThirdQuadrant

- European country

- ISO standard

- Canada, USA,

Japan, Thailand


12

ORTHOGRAPHIC PROJECTION

1st angle system 3rd angle system


13

ORTHOGRAPHIC VIEWS


Foldingline

Foldingline

Foldingline

Foldingline


14


ORTHOGRAPHIC VIEWS


Front View

Front View

Right Side View

Right Side View

Top View

Top View

15


First angle system Third angle system

PROJECTION SYMBOLS

16

First-angle Projection Method

In first-angle projection, an object is placed in the first quadrant, i.e., above the HP and in front of the VP. (shown in NEXT fig.)

The object lies in between the observer and the plane of projection.

The plane of projection is assumed to be non transparent and views drawn on it.

Front view is above the reference axis and top view lies below the reference axis exactly bellow the front view.

Right hand side view is drawn to left of front view and Left hand side view is drawn to the right of front view.

First angel projection symbol:

METHODS OF MULTIVIEW PROJECTION


17

First angle projection method


18


18

Third -angle Projection Method

In third-angle projection, an object is placed in the third quadrant, i.e., below the HP and behind the VP (shown in NEXT fig.)

The plane of projection lies in between the observer and the object.

The plane of projection is assumed to be transparent and views drawn on it.

Front view is below the reference axis and top view lies above the reference axis exactly above the front view.

Right hand side view is drawn to right side of front view and Left hand side view is drawn to the left side of front view.

Third angel projection symbol:

METHODS OF MULTIVIEW PROJECTION

19

Third angle projection method


20


20

Difference in first and third angel projection

21


The second and fourth angel methods are not used in practice because after rotating the horizontal plane by 90° in clockwise direction the front view and top are overlapping. So we can not differentiate the front and top vies.

Why we are not using second and fourth angle projections ?

22


To obtain the projections of various faces of an object, the following rules must be observed:

1. If a face is perpendicular to the direction of viewing, its true shape and size will be seen in that view.

2. If a face is parallel to the direction of viewing, it is seen as a line in that view. This view is called the line view or edge view.

3. If a face is inclined to the direction of viewing, its true shape and size will not be seen in any view.

4. If an edge of the object is perpendicular to the direction of viewing, its actual length will be seen in that view.

5. If an edge of the object is parallel to the direction of viewing, it is seen as a point in that view. This view is called point view.

6. If an edge of the object is inclined to the direction of viewing, its foreshortened length will be seen in that view. The foreshortened length is obtained by locating the end points of the edge.

Some guide lines to draw the views of object

Glass Box Approach23


24


25


26


27


13723_orthographic projection

Documents

pradip patil

1st angle

3rd angle

angle projection

angel projection

hand side

top view lies

angle system