Orthographic Projection Welcome Engineering Graphics - Lect

Types of lines Line for an outline of view Projection line Hidden line Center line

Applications of Types of Lines

4  Objects are not always drawn to their actual size.  They may be too large to fit a standard drawing sheet, or too small for all details to clearly show.  For example, a microchip circuit must be drawn at several thousand times its actual size to be seen. On the other side, a plan view of a small town must be drawn with reduced scale than the actual size. Drawing Scale

5 Type of scaleRecommended scale Reduction scale 1:101:21:5 1:1001:201:50 1:10001:2001:500 1:100001:20001:5000 Enlargement scale 10:120:150:1 2:15:1 Full scale1:1 Drawing Scale

Projection Projection : In Engineering drawing, the word projection means an image or the act of obtaining the image of an object. Technical people often refer to the image as a view.

Projection Methods  Orthographic Projection  Isometric Projection  Oblique Projection  Perspective Projection

Orthographic Projection Multiview Drawings

Technique used to present a three- dimensional object (an object having height, width and depth) As a group of related two-dimensional views ( having only width and height, or width and depth). 10 Multiview drawing

A better way to fully describe the bus graphically would be to create a multiview drawing. The multiview drawing of the bus is represented by six views, the front, top, sides, back and bottom. These views represent the six “regular” views of the bus. Top View Front View Bottom View Right View Left View Back View 11

The 6 principle views are created by looking at the object, straight on, in the directions indicated. 12 The Six Principle Views

PROJECTION THEORY The projection theory is based on two variables: 1) Line of sight 2) Plane of projection (image plane or picture plane) The projection theory is used to graphically represent 3-D objects on 2-D media (paper, computer screen). 13

Line of sight Line of sight is an imaginary ray of light between an observer’s eye and an object. Line of sight Parallel projection 14

Plane of projection Plane of projection is an imaginary flat plane on which the image is created. The image is produced by connecting the points where the LOS (Light of sight) pierce the projection plane. Parallel projection Plane of projection 15

Orthographic Projections It is a parallel projection technique in which the Lines of Sight (LOS) are perpendicular to the Plane of Projection Ortho –1 straight. 2 right.(Oxford Dictionary)Ortho –1 straight. 2 right.(Oxford Dictionary) 16

Planes of Projection Vertical Plane of Projection (V.P.) – Also called as Frontal Reference Plane (F.R.P.) – Projections obtained in FRP are called as Front View Horizontal Plane of Projection (H.P.) – Also called as Horizontal Reference Plane (H.R.P) – Projections obtained in HRP are called as Top View 17

H.R.P F.R.P. H.R.P. and F.R.P.

Planes of Projection 90 0 H.R.P. F.R.P P.R.P X Y 20

Four Quadrants If the Planes of Projection are extended beyond the line of intersection (XY line) they form four quadrants. All planes are assumed to be transparent. 21

Four Quadrants 22

Methods of Projections First Angle Method – Object is kept in FIRST QUADRANT. Third Angle Method – Object is placed in the THIRD QUADRANT. 23

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First Angle Method 26

First Angle Method 27

First Angle Method 28

First Angle Method 29

First Angle Method 30

First Angle Method- Conversion to 2D 31

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FOR T.V. FOR S.V. FOR F.V. FIRST ANGLE PROJECTION IN THIS METHOD, THE OBJECT IS ASSUMED TO BE SITUATED IN FIRST QUADRANT MEANS ABOVE HP & INFRONT OF VP. OBJECT IS INBETWEEN OBSERVER & PLANE. ACTUAL PATTERN OF PLANES & VIEWS IN FIRST ANGLE METHOD OF PROJECTIONS X Y VP HP PP FVLSV TV

Third Angle Method 34

Four Quadrants 35

Third Angle Method 36

Third Angle Method 37

Third Angle Method 38

Third Angle Method 39

Third Angle Method H.R.P. F.R.P 40

Third Angle Method H.R.P. F.R.P 41

In this method, The object is assumed to be situated in third quadrant (Below HRP & behind of FRP) 42 Planes being transparent and in between Observer & object.

Symbolic Representation

44 1. Principal surface 2. Inclined surface 3. Skew surface 4. Curved surface Types of Surfaces

45 The surface, which is parallel to one reference plane and perpendicular to other two, is referred as principal surface. It shows two line views and one area view as true area. Horizontal surfaces are always principal surfaces but not the vertical. Principal Surfaces

46 The surface, which is inclined to two reference planes and perpendicular to other, is referred as an inclined (or slant) surface. It shows one line view and two area-views with apparent size as shown in Figure. In this type of surface, at least one edge of the surface is along the principal axis. Inclined Surfaces

47 The surface, which is inclined to all three principal planes (HP, VP and PP), is referred as a skew (or oblique) surface. It shows 3 area- views with apparent size as shown in Figure. In this type of surface, none of the edge of the surface is along the principal axis. Skew Surfaces

48 The surface, which has constant radius such as arc or circle, is referred as curved (or rounded surface). Curved Surfaces In this type of surface, the last visible part of the curved surface falls in line view.

49 Concept of Hidden Line

50 Hidden Line Coincides with Visible Line

51 Last visible part of curved surface falls into a line view

52 Object as an Assembly

53 Object as a Single Piece

54 Object as a Single Piece

55 Assembly versus Single Piece Object

56 Precedence of Lines

57 Thickness 3 mm FV One View Drawing

58 Three View Drawing

59 Three View Drawing

Example 60

Example 61

Example 62

Example 63

Example 64

Example 65

Example 66

Example 67

Example 68

Example 69

Example 70

Example 71

Example 72

Example 73

Example 74

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Fill in the visible lines into top view.

Fill in the visible lines in to front view.

Fill in the visible lines in to right side view.

Fill in the hidden lines in to front, top and right side views.

Draw the center lines in all the views.

X Y

Problem 13 F.E. (Graphics) - Nilesh Sabnis R D X 55