orthographic projection

1. Orthographic projection In engineering drawing the meaning of the word projection is to project(Throw ) an object on to a plane by means of straight lines. The representation of any three dimensional object placed in front of a two dimensional plane is called Projection of an object on that plane.

2. contents Introduction to orthographic projections First angle projection method Third angle projection methods Drawing orthographic projection of simple pictorial view

3. Introduction to orthographic projection In orthographical projection it is assumed that observer is at infinite distance and rays or projection lines are parallel to each other and perpendicular to the plane of projection.( e.g board and students, theater)

4. System of orthographic projection

5. How to identify the quadrant of object Sr.no Quadrant Position of the object with respective planes of projection 1 First Above HP,in front of VP 2 Second Above HP,Behind V.p 3 Third Below HP.Behind VP 4 Fourth Below HP,in front of VP

6. Position of the views on a plane paper when object is lying in four quadrant. Position of the object Position of the top view Position of the front view First quadrant Below XY axis Above XY axis Second quadrant NA NA Third quadrant Above XY Below XY Fourth quadrant NA NA

7. Sketches speaks more………….

8. First angle projection method When an object is situated in the first quadrant, The method of projection is said to be FIRST ANGLE PROJECTION METHOD. When an object is situated in third quadrant ,The method of projection is sai to be THIRD ANGLE PROJECTION METHOD.

9. Important facts about first angle projection method 1.The object is situated in first quadrant. 2.The object lies between the observer and the principal plane. 3.The orthographic projection of an object obtained on the vertical plane is front view. 4.The orthographic projection of an object obtained on HP is TV and lies below the XY line. 5.LHSV is drawn on the right side of FRONT VIEW. 6.RHSV is drawn on the left side of FRONT VIEW.

10. Now you can analyze better………..

11. Procedure of preparing orthographic views by using first angle projection method 1.Find out the maximum size of box which will contain the object. 2.Draw FV, TV, and RHSV of the imaginary box.While drawing the views of the box maintain proper spacing of the views with reference lines XY 3.Now Draw the portion which is visible from front in FRONT VIEW. 4.The portion of the object which will be visible from the top is drawn in top view.

12. Third angle projection method When object is situated in third quadrant,The method of projection is said to be THIRD ANGLE PROJECTION METHOD.

13. THANK YOU