ORTHOGRAPHIC PROJECTION

BE-SEM-1DIVISION-KGROUP-46 TO 52L.D.COLLEGE OF ENGINEERING

1• ORTHOGRAPHIC

PROJECTIONS

2• SYSTEMS OF ORTHOGARPHIC

PROJECTONS

3• First angle system of

projections:

4• Third angle system of

projections:

5 • Important conclusions

6 • Methods of projections

1.ORTHOGRAPHIC PROJECTIONS

In Orthographic projection ,it is assumed that observer is at infinite distance and rays or projection lines are parallel and perpendicular(i.e. ortho.)to the plane of projection .

It is extensively used by engineers for the purpose of communication because these projections reveal exact shape and size of the object .

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There are six directions of sight, six principal planes perpendicular to these six directions of sight and correspondingly there are six principal projections .they are given in the table below.

Direction of sight

Plane of projection

Name of projection

1 From front Vertical plane Front view /front elevation

2 From rear -do- Rear view/rear elevation

3 From top Horizontal plane Top view/top plan

4 From bottom -do- Bottom view/bottom plan

5 From right Profile plane Right hand side view

6 From left -do- Left hand side view

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2.SYSTEMS OF ORTHOGARPHIC PROJECTONSThere are two systems of principal orthographic projections, they are as follows:

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SYSTEMS OF ORTHOGARPHIC PROJECTONS

1.First angle system of

projections

2.Third angle system of

projections

In both systems of projections object is imagined inside a transparent glass box.Object is viewed from all six directions perpendicular to the plans of glass box. Important features of the object is kept parallel to the front plane of glass box.Projection is named according to the directions of sight. now we shall study system of projections and note where exactly they differ. now a days the 1st angle system is more popular. Difference in the two systems is underlined. 4

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3.1First angle system of projections:

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3.2 First angle system of projections:

As shown in pervious slide object is shown inside a glass box. Look at the object from all six directions and draw viewed as given below.

no View of the object from

Known as Is drawn on the

1 front Front elevation or F.V. Rear plane of the box

2 rear Rear elevation or R.V. Front plane of the box

3 top Top plan or T.V. Bottom plane of the box

4 bottom Bottom plan or B.V. Top plane of the box

5 right Right hand view Left plane of the box

6 left Left hand view Right plane of the box

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3.3First angle system of projections:

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3.4 First angle system of projections:

Having already drawn six view on the six planes of the box ,as shown in previous slide open out five planes of the box around plane containing front elevation or F.V.(i.e. REAR PLANE OF THE BOX ).In the open condition all planes along with projections will look like as shown in figure1 .views are finally drawn as shown in figure 2.

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3.5 First angle system of projections:

Observe these views to under stand following for 1st angle system of projection .1.Front elevation or F.V. remains in the center of all views.2.Top plan or T.V. is vertically below F.V.3.Bootom plan or B.V. is vertically above F.V.4.R.H.E.V or R.H.S.V is horizontally on left of F.V.5.L.H.E.V or L.H.S.V is horizontally on right of F.V.6.Rear elevation or rear view is horizontally on extreme right of F.V.7.Front portion of the object, in all views surrounding F.V., faces away front F.V.

8.Rear portion of the object, in all views surrounding F.V., faces F.V.9.Length of F.V. and T.V is same.10.Hight of the F.V and S.V. is same.11. In depth of the top view is the same as the depth of the side view.

3.6 First angle system of projections:

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4.1 Third angle system of projections:

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4.2 Third angle system of projections:

As shown in pervious slide object is shown inside a glass box. Look at the object from all six directions and draw viewed as given below.no View of the

object fromKnown as Is drawn on the

1 front Front elevation or F.V. Front plane of the box

2 rear Rear elevation or R.V. Rear plane of the box

3 top Top plan or T.V. Top plane of the box

4 bottom Bottom plan or B.V. Bottom plane of the box

5 right Right hand view Right plane of the box

6 left Left hand view Left plane of the box

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4.3 Third angle system of projections:

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4.4 Third angle system of projections:

Having already drawn six view on the six planes of the box ,as shown in previous slide open out five planes of the box around plane containing front elevation or F.V.(i.e. FRONT PLANE OF THE BOX ).In the open condition all planes along with projections will look like as shown in figure1 .views are finally drawn as shown in figure 2.

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4.5 Third angle system of projections:

Observe these views to under stand following for 3rd angle system of projection .1.Front elevation or F.V. remains in the center of all views.2.Top plan or T.V. is vertically above F.V.3.Bootom plan or B.V. is vertically below F.V.4.R.H.E.V or R.H.S.V is horizontally on right of F.V.5.L.H.E.V or L.H.S.V is horizontally on left of F.V.6.Rear elevation or rear view is horizontally on extreme right of F.V.7.Front portion of the object, in all views surrounding F.V., faces the front F.V.

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4.6 Third angle system of projections:

8.Rear portion of the object, in all views surrounding F.V., faces away from F.V.9.Length of F.V. and T.V is same.10.Hight of the F.V and S.V. is same.11. In depth of the top view is the same as the depth of the side view.

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5.1 Important conclusions

Now it is advisable to go through some important conclusions regarding projections of straight lines and projections of plans.

1.If a line is perpendicular to one of the principal planes then it will be parallel to two other principal planes.

2.If a line is perpendicular to one of the principal planes then its projection on that principal plan will be point view and on other two principal planes it will show the true length.

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5.2 Important conclusions

3.If a line is parallel to one of the principal planes and inside to two other P.Ps then its projection on parallel P.P. will be the true length showing true inclinations and on other P.Ps it will show shorter lines parallel to ground lines(vertical or horizontal).

4.If a line is inclined to all P.Ps then its all projections will be shorter and inclined to ground lines

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5.3 Important conclusions

5.If a surface is parallel to one of the principal then its projection on it will be the true shape and projections on other two principal plane will be straight lines parallel to corresponding ground lines.

6.If a surface is perpendicular to one of the principal planes and inclined to two other. Its projection on it will be straight line and other two views will be foreshortened.

7.If a plane is inclined to all principal planes then nowhere it will show straight line view and all projections will be foreshortened.

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6.1 Methods of projections

The projections of an object are obtained by one of the following method 1.The glass box method see in previous slide 2.The natural method shown in figure.

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6.2 Methods of projections

Natural method:-Object is kept in a position such that its important features face front side. now look at the object from front , top, bottom , right , left and rear to get front view, top view, bottom view, right hand side view, left hand side view and rear view respectively.

In figure six principal projections according to 3rd angle system are shown. In the application of this method either observer changes his position and observes the object fr4ojm six different positions or observer remains at one position and turn the object to observe 6 faces of the object to get six different projections

• NameRoll no 1092….

•Akash Chauhan 46

•Hitesh Chavda 47

•Hiren Patel 48

•Harshad Pargi49

•Mehul Patel50

•Ronak Pargi51

•Chintan Kunbi 52

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