fundamentals of drawing and isometric and orthographic projection

fundamentals of drawing and difference between isometric and orthographic projection. Basic representation principles.

1. ENGINEERING DRAWING FUNDAMENTALS

2. CONTENTS 1. Engineering Drawing Definition 2. Projection 3. First Angle Projection 4. Third Angle Projection 5. Multi views 6. Conversion of Isometric to orthographic 7. Conversion of orthographic to Isometric

3. ENGINEERING DRAWING Engineering Drawing is a two dimensional representation of a three-dimensional object graphically.

4. The ability to read drawings is the most important requirement of all technical people in engineering profession. Graphics language Describe a shape (mainly). Word language Describe size, location and specification of the object.

5. The classification of Engineering Drawings include: Building drawing, Machine drawing, Electrical drawing etc. Dimensions are indicated on the drawing to define geometric characteristics such as lengths, diameters, radii, angles and locations.

6. SCALE Size in drawing Actual size : All engineering drawings are prepared to some scale. The scale adopted should be the largest possible one. Full size scale, Reducing scale and Enlarging scale. Full size scale 1:1, Reducing scale 1:2, Enlarging scale 50:1

7. PROJECTION A projection is defined as a representation of an object on a two dimensional plane. There are basically three types of projections. Orthographic projection Isometric projection Perspective projection

8. ORTHOGRAPHIC PROJECTION A projection is said to be orthographic, when the point of sight is imagined to be located at infinity, so that the rays of sight are parallel to each other and intersect the plane of projection at right angles to it. Line of sight Line of sight

9. Line of sight is an imaginary ray of light between an observer’s eye and an object. Line of sight Parallel projection Line of sight Perspective projection There are 2 types of LOS : parallel converge and

10. Plane of projection is an imaginary flat plane on which the image is created. The image is produced by connecting the points where the LOS pierce the projection plane. Parallel projection Perspective projection Plane of projection Plane of projection

11. Perspective projection is not used by engineer for manu- facturing of parts, because 1) It is difficult to create. 2) It does not reveal exact shape and size. Width is distorted Disadvantage of Perspective Projection

12. Orthographic projection technique can produce either 1. Multiview drawing that each view show an object in two dimensions. 2. Axonometric drawing that show all three dimensions of an object in one view. Both drawing types are used in technical drawing for communication. ORTHOGRAPHIC VIEW

13. Axonometric drawing Multiview drawing

14. Drawing Sheet Sizes Trimmed paper of a size A0 ~ A4. Standard sheet size A4 210 x 297 A3 297 x 420 A2 420 x 594 A1 594 x 841 A0 841 x 1189 A4 A3 A2 A1 A0 (Dimensions in millimeters)

15. Example Placement of the text on drawing Dimension & Notes Notes Title Block

16. PROJECTION SYSTEMS 1. First angle system 2. Third angle system First Quadrant Third Quadrant - European country - ISO standard - Canada, USA, Japan, Thailand

17. ORTHOGRAPHIC PROJECTION 1 st angle system 3 rd angle system

18. ORTHOGRAPHIC VIEWS 1 st angle system 3 rd angle system Folding line Folding line Folding line Folding line  

19. ORTHOGRAPHIC VIEWS 1 st angle system 3 rd angle system Front View Front View Right Side View Right Side View Top View Top View

20. First angle system Third angle system PROJECTION SYMBOLS

21. ISOMETRIC PROJECTIONS Isometric projection is a type of pictorial projection in which the three dimensions of a solid are shown in one view

22. CONVERSION OF ORTHOGRAPHIC TO ISOMETRIC PROJECTION

23. CONVERSION OF ISOMETRIC TO ORTHOGRAPHIC PROJECTION

24. CONVERSION OF ISOMETRIC TO ORTHOGRAPHIC PROJECTION

25. Orthographic views of objects with either (i) a line or (ii) lines missing are given below. Complete the given views. Also draw freehand, the isometric view of each object.

26. MACHINE DRAWING

27. PRODUCTION DRAWING

28. EXAMPLE : Interpreting detail drawing General note Revision table Title block 1. Orthographic views 2. Dimensions & Tolerances 3. Surface finishing Projection Gen. tolerance

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