Lesson 5
ORTHOGRAPHIC DRAWING
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LESSON 5 OUTLINE
LESSON 5 OUTLINE
Lesson 5ORTHOGRAPHIC DRAWING - SIMPLIFIED
ORTHOGRAPHIC DRAWING - SIMPLIFIED
ORTHOGRAPHIC DRAWING
ORTHOGRAPHIC DRAWING
UNDERSTANDING ORTHOGRAPHIC PROJECTION
UNDERSTANDING ORTHOGRAPHIC PROJECTION
INTRODUCTION TO ORTHOGRAPHIC PROJECTION
INTRODUCTION TO ORTHOGRAPHIC PROJECTION
OBJECTIVES
At the end of the lesson the students should be able to;
understand what orthographic drawing is all about;
know the types of orthographic drawing; and,
draft orthographic projections
ORTHORAPHIC DRAWING
ORTHORAPHIC DRAWING
Orthographic Drawing which is one of the three types of parallel projections (orthographic, oblique, and axonometric), can be defined as a type of technical drawing in which 3-dimensional (3D) objects are represented in 2 dimensions (2D) by projecting planes (consisting of 2 major axes) of objects so that they are parallel with the plane of the media (paper, or computer) they are projected upon.
The two major types of orthographic drawing use two-dimensional views (obtained from different directions or lines of sight) to represent different parts of three-dimensional objects, or planes of objects viewed from/along different axes—typically, the x, y, and z axes.
THREE PRINCIPLE VIEWS
THREE PRINCIPLE VIEWS
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- Top View - Location directly on top of front view.
- Front View - Located just below top view and above bottom view. View in between right and left side views.
- Side View - Normally the right side and located on the right of the front view.
Figure 1
THREE PRINCIPLE DIMENSIONS IN RELATION TO THE PRINCIPLE VIEWS
THREE PRINCIPLE DIMENSIONS IN RELATION TO THE PRINCIPLE VIEWS
1. Height - Revealed in between front and side views.
2. Width - Revealed in between front and top views.
3. Depth - Revealed in between side and top views.
Figure 2
TYPES OF ORTHOGRAPHIC DRAWING
TYPES OF ORTHOGRAPHIC DRAWING
Orthographic drawing (also known as orthographic projection) consists of two types: first angle projection, and third angle projection.
In third-angle projection, the view of a component is drawn next to where the view was taken. In first-angle projection, the view is drawn on the other end of the component, at the opposite end from where the view was taken. (As shown in figure 3).
Figure 3
FIRST ANGLE PROJECTION
FIRST ANGLE PROJECTION
In first angle projection, which is popularly practiced in Europe, whenever six views are used to illustrate how the sides of a 3D object look from six directions (as shown in Figure 4 below), they are usually arranged in the following manner (as shown in Figure below):
The bottom view E is placed at the top of the paper or computer screen.
The front view A is placed beneath the bottom view E.
The top view D is placed beneath front view A (i.e., at the bottom of the paper or computer screen.
The right view C is placed on the left side of front view A.
The left view B is placed on the right side of front view A.
The back/rear view F (which is not shown in Figure 4) is usually placed at the extreme left or right—whichever position is convenient.
Figure 4
Six directions for six views. (Image Credit: Simmons, C. H. and Maguire, D. E. (2004). Manual of Engineering Drawing: p. 33.)
FIVE VIEWS OF FIRST ANGLE PROJECTION
FIVE VIEWS OF FIRST ANGLE PROJECTION
Five views of first angle projection; the sixth view F would depend on the shape of the back/rear view of the object. (Image Credit: Simmons, C. H. and Maguire, D. E. (2004). Manual of Engineering Drawing: p. 34.)
Whenever four views are used, the front view is usually placed at the top of a medium (paper, computer screen, etc.) along with the right side view which is placed at the left side of the front view, while the left side view is placed at the right side of the front view, and the top view (T) is placed alone beneath the front view.
Figure 5
It has to be noted that in many first angle orthographic drawing practices, three views could be sufficient enough to describe the shapes and dimensions of the most important sides of an object which actually exist in 3D as shown in Figure 6 below:
Figure 6
A three dimensional object with 7 visible edges (A, B, C, D, E, F, and G)
THIRD ANGLE PROJECTION
THIRD ANGLE PROJECTION
In third angle projection, which is mostly practiced in North America, whenever six views are used to describe the sides of a 3D object from six different directions (as shown in Figure 4 above), they are usually arranged in the following manner (as shown in Figure 7 below):
The top view D is placed at the top of the paper or computer screen.
The front view A is placed beneath the top view D.
The bottom view E is placed beneath front view A (i.e., at the bottom of the paper or computer screen).
The right view C is placed on the right side of front view A.
The left view B is placed on the left side of front view A.
The back/rear view F is usually placed at the extreme left or right—whichever position is convenient.
Figure 7
Five views of third angle projection; the sixth view F would depend on the shape of the back/rear view of the object. (Image Credit: Simmons, C. H. and Maguire, D. E. (2004). Manual of Engineering Drawing: p. 34.)
Whenever four views are used, the top view is usually placed alone at the top of a medium (paper, computer screen, etc.), while the front view is placed beneath the top view, and the right side view is placed at the right side of the front view, while the left side view is placed at the left side of the front view. (Note that third angle projection is the most popular type of orthographic drawing or projection.)
Generally speaking, the difference between first angle projection and third angle projection depends on where each view is placed on paper or computer screen according to the universally accepted requirements of the two main types of orthographic drawing/projection.
ORTHOGRAPHIC DRAWING VIEWS
ORTHOGRAPHIC DRAWING VIEWS
Figure 8
TOOLS AND APPLICATION OF ORTHOGRAPHIC DRAWING PRACTICE
TOOLS AND APPLICATION OF ORTHOGRAPHIC DRAWING PRACTICE
Tools required for orthographic drawing practice
Tools required for orthographic drawing practice
With regular drawing practice, it is very easy to learn and perfect orthographic drawing skills. The tools usually required for practicing orthographic drawing are quite the same as the ones specified in technical and engineering drawing, respectively. Generally, the tools include:
Drawing board.
Drawing paper: either Ao, A1, A2, A3, and A4.
Drawing pencil.
Eraser.
30°×60° and 45°×45° set squares.
300 mm (30 cm) ruler.
T-square.
Drawing compasses
Applications of orthographic drawing practice
Applications of orthographic drawing practice
Orthographic drawings have many applications scattered across various fields that require planning and designing such as architecture, construction, design, engineering, environment, estate management, manufacturing, surveying, etc.
Orthographic drawings are usually produced according to precision and requirements. It is possible for an orthographic drawing that has been produced in one country, to be used to manufacture an object in another country.
LEARNING ACTIVITY
LEARNING ACTIVITY
LA-LESSON-5.docxREFERENCES:
CONTENT SOURCE:
CONTENT SOURCE:
Manaois, German M. Drafting Volume 2: Phoenix Publishing House, Inc., 1983, Reprinted 2004
Manaois, German M. Drafting Volume 2: Phoenix Publishing House, Inc., 1983, Reprinted 2004
Brown, W. C. (1994). Drafting for Industry /by Walter C. Brown. Goodheart-Willcox.
Brown, W. C. (1994). Drafting for Industry /by Walter C. Brown. Goodheart-Willcox.
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