Orthographic Projection – Its 2 [Methods & Rules]

The orthographic projection represents three-dimensional objects in two dimensions, and the object is the view in parallel lines that are perpendicular to the drawing plan. Instead of a single three-dimensional view, it uses different two-dimensional views of the object in Orthographic projection.

To represent the image of an object, the orthographic drawing is precise and detailed and used by engineers, designers, and architects to help manufacturing understanding. These projections in either a first or third-angle projection are working drawings.

Orthographic projection drawing consists of three different views front view, top view, and side view; for clarity, more views are used, and usually, the view is on the right side.

Views Of Orthographic Projection:

There are three main views of Orthographic projection such as:

1. Front view
2. Top view
3. Side view

Front View:

These views are prepared by placing the object in front, and in this view, the height and length of the object are shown.

Top View:

By looking at the object from the upper side, this view is prepared, and in this view length and breadth of an object is shown.

Side View:

By looking at the object from the left side or right side, this view is prepared, and in this view breadth and height of an object is shown.

Planes Of Orthographic Projection:

There are three planes of Orthographic projection;

1. Frontal Plane
2. Profile Plane
3. Horizontal Plane

Frontal Plane:

While projections are drawn, such a plane placed in front of an object is called the frontal plane.

Profile Plane:

On this plane side view of an object is drawn, and this is a plane placed to the left or right of an object.

Horizontal plane:

In an object’s horizontal position, this plane is placed upward or downward, and on this plane top view of the object is constructed.

Drawing Of Orthographic Projection:

There are two methods in which the plane is placed;

1. Dihedral Angle
2. Trihedral Angle

Dihedral Angle:

Two principals are kept perpendicular to each other in this method, and one of these planes is horizontal, and the other is frontal. In this way, four right angles are obtained and called dihedral angles, and to take orthographic projection, the object is placed in any of these right angles.

The front view is taken on the frontal plane, and on a horizontal plane, the top view is taken. To take side views profile plane is used.

Trihedral Angle:

All the three principal planes are taken perpendicular to one another, due to which eight right angles are formed and called trihedral angles. To take orthographic projection, an object is placed in any of these right angles, and on the frontal plane, the front view is taken, and on a horizontal plane, the top view is taken. To take side views profile plane is used.

Angles Of Orthographic Projection:

There are the following angles of projection;

1. First Angle System
2. Second Angle System
3. Third Angle System
4. Fourth Angle System

Generally, the second angle systems and fourth angle systems are not used because the line of views of the object overlaps, so first and third angle systems are mainly used.

First Angle System:

By placing it in the first quadrant of dihedral or first octant of a trihedral angle, this view of an object should be taken, and this system is called the first angle system.

The planes are straightened by rotation by taking a top view on the horizontal plane & front view on the frontal plane, and a side view on the profile plane in this wayside view comes beside the front view, and the front view comes over the top view.

Symbol:

Characteristics of First Angle Projection:

There are the following characteristics of first angle projection as given below:

1. Over the top view front view always comes.
2. Under the front view top view always comes.
3. To the left at the front view right side view always comes.
4. To the right of the front view left side view always comes.
5. To the observer, the view is always in the opposite direction.
6. To the view and observer, the object is always in the middle.

Third Angle System:

By placing it in the third quadrant of dihedral or third octant of a trihedral tingle if the view of an object is taken, it is called the third angle system.

On the horizontal plane, the top view forms, and the profile plane side view forms, and on the frontal plane, the front view is formed. The planes are set straight by rotation after making the views, and over the front view, the top view comes while by the side of the front view, the side view forms in this way.

Symbol:

Characteristics of Third Angle Projection:

There are the following characteristics of third angle projection such as;

1. Over the front view top view comes.
2. Under the top view front view always comes.
3. To the right of the front view right side view always come.
4. To the left of the front view left side view always comes.
5. To the side of the observer, the view is always formed.
6. To the object and observer, the view is always in the middle.

Difference Between First And Third Angle Projection:

There are the following differences between the first angle projection and third angle projection:

Rules To Be Follow:

While forming orthographic drawings following rules should be followed;

1. To top view and front view always form over each other.
2. The length and height of an object are shown in the front view.
3. The breadth and height of an object are shown by side view.
4. The length and breadth of an object are shown by the top view.
5. Besides, the front view and side view constantly forms.
6. By the meeting of two surfaces projection line constantly forms.
7. By dotted line, the hidden detail of an object is always shown.

Selection Of View:

In the section of the view, the following points should be kept in mind;

1. The selected view should be more detailed.
2. Full detail should be made by a section of the view.
3. More internal details should be made by a section of the view.
4. A view of the required detail should be made and selected.