Computer Aided Engineering Drawing (20ME12P) Unit – 02 introduction to orthographic projections
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This document provides an overview of orthographic projections, detailing the principles, methods, and symbolic representations used in creating 2D representations of 3D objects. It discusses the use of principal planes (frontal, profile, and horizontal) and outlines various projection methodologies (first to fourth angles). Additionally, it explains how to represent points in different quadrants of projection.
Computer Aided Engineering Drawing (20ME12P) Unit – 02 introduction to orthographic projections
- 1. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 1 Computer Aided Engineering Drawing (20ME12P) Unit – 02 Part 01- Introduction to Orthographic Projections Introduction to Orthographic Projections (Theory) 2.1 Introduction to Projections-Principle Planes of Projection and Principle Views 2.2 Introduction to First angle, Second angle, Third angle and Fourth angle method with their symbolic representation. 2.3 Projection of points in All 4 Quadrants
- 2. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 2 2.1 Introduction to Orthographic Projections An Orthographic projection is a 2-D representation of a 3-D object. The 2-D drawing represents different sides of an object. This is such a type of drawing in which Parallel Projection is used for the preparation of the drawing of an object. These lines are perpendicular to the plane. In this drawing, it is assumed that the object is at infinity. The shape of an object is seen in actual size in such drawing. A plane is an imaginary surface on which pictures are prepared imaginably. Then it is transferred to the paper. This plane is faced toward the object whose view is to be prepared. Generally, three views of an object are prepared. These are Top View, Front View, and Side View.
- 3. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 3 2.1.1 Principle Planes of Projection A plane is an imaginary and invisible clear surface. The drawing constructed on this imaginary curtain is transferred on the drawing sheet. For example, if we look at some object through glass or plastic piece, then the picture of the object will be seen there. This piece will work as a plane. However, this plane is not a material body. It is only an imaginary curtain, which is used to give the shape of a drawing by placing it in different positions. This plane can be put in different positions. However, the plane placed in the following positions is called the Principal Plane. Besides such positions, the plane will be called Auxiliary Plane. 1. Frontal Plane. 2. Profile Plane. 3. Horizontal Plane.
- 4. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 4 1. Frontal Plane: Such a plane which is placed in front of an object, while projections are drawn, is called the Frontal plane. 2. Profile Plane: Such a plane which is placed to the right or left of an object. Side view of the object is drawn on this plane. 3. Horizontal Plane: This is a plane which is placed upward or downward in the horizontal position of an object. Top view of the object is constructed on this plane. 2.1.2 Principle Views The 6 principal views are created by looking at the object (straight on) in the directions indicated. Following views are formed of an object in Orthographic Projection. 1. Front View. 2. Top View. 3. Back View. 4. Bottom View. 5. Right Side View. 6. Left Side View.
- 5. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 5 2.2 Introduction to First angle, Second angle, Third angle and Fourth angle method with their symbolic representation. Rules of Orthographic Projections 1) Vertical and Horizontal Planes are imaginary surface plane and transparent which is intersected. 2) Object is Placed in any of the Four Quadrant 3) View Direction is from right to left and top to down in case of any quadrant. 4) The shape of an object is seen in actual size in Planes of Projections (VP or HP). 5) Once the projections are drawn the original object is taken out. 6) Vertical Plane (VP) is fixed and only Horizontal plane is rotated clock wise till it touches Vertical plane on other side, this includes even rotation of Profile Plane in line with Vertical Plane. 7) The symbolic representation is shown along the drawing so that the engineers can identify which quadrant it belongs to. 8) Vertical Plane annotations are represented by („) ex a‟, b‟, c‟...etc. 9) Horizontal Plane annotations are represented by ex a, b, c...etc. 10) Profile Plane annotations are represented by (“) ex a”, b”, c”..etc.
- 6. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 6 Quadrant Orthographic 3D Plane of Projection after Rotating HP Symbolic Representation of the Quadrant First Quadrant or First angle of Projection Second Quadrant or Second angle of Projection Third Quadrant or Third angle of Projection Fourth Quadrant or Fourth angle of Projection
- 7. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 7 2.3 Projection of points in All 4 Quadrants Representation terms used to explain the location of Points in any of the Four Quadrant 1) A Point (A) 15 mm above HP and 20 mm in-front of VP. Draw its Projections.
- 8. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 8 2) A Point (B) is 25 mm above HP and 30 mm behind VP. Draw its Projections. 3) A Point (A) is 15 mm below HP and 30 mm behind of VP. Draw its Projections. 4) A Point (B) is 35 mm below HP and 15 mm In-front of VP. Draw its Projections.