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14773 chapter 07
- 1. Mechanical Sciences-I Chapter 7: Orthographic Projections
- 2. Introduction to Orthographic Projections Introducing Orthographic Projections as the language of engineering designers
- 4. An orthographic projection consists of the view obtained view when the object is viewed from very far away, so that the resulting rays are all parallel.
- 5. The parallel rays that are used for constructing the views are called projectors.Vijay Gupta
- 7. The intersections of the projectors with the picture plane are the projections of the points from which the projectors emanate.
- 8. The points are joined to obtain the views.Vijay Gupta
- 9. We consider here the development of the orthographic views of a simple object. Object Vijay Gupta
- 10. For the Top view we view from the top! Viewing Direction Picture Plane Vijay Gupta
- 11. Viewing Direction Projectors Perpendicular to picture plane Point of intersection with picture plane Vijay Gupta
- 12. Viewing Direction Intersections of all extreme points Vijay Gupta
- 13. Top View Vijay Gupta
- 14. Similarly, viewing from the front with parallel projectors Front View Vijay Gupta
- 15. Top & Front Views on opening up the page Notice the interrelation Vijay Gupta
- 16. Similarly, the Right Side View Again notice the interrelation Vijay Gupta
- 17. Mitre The third view can also be obtained by taking projections from the two views, using the mitre line, a line at 450 Vijay Gupta
- 18. Two types of projections commonly used: I & III angle I-Angle In third angle, picture planes in between the viewer & object In first angle, picture plane behind the object III-Angle Vijay Gupta
- 19. Opening up of the box with the various views in III angle Vijay Gupta
- 20. The relationship on plane paper of the various views in III angle III Angle Top View Front View Right View Left View Vijay Gupta
- 21. Vijay Gupta
- 22. I-Angle The relationship on plane paper of the various views in I angle Front View Left View Right View Top View Vijay Gupta
- 23. Vijay Gupta
- 24. Mitre Front Top View Front View Vijay Gupta
- 25. Top View Front Front View Vijay Gupta
- 26. Drawing three views in III angle Mitre Top View Front Front View Vijay Gupta
- 28. A demonstration Vijay Gupta Gboxw31.exe
- 30. Front X X X X X X X X Vijay Gupta
- 31. Notice that the oblique face of the cylinder appears as an ellipse in right-side view, but as lines in the front view. Front Vijay Gupta
- 32. Hidden Features
- 33. Hidden Features Shown by dashed lines
- 34. Hidden Features
- 35. Hidden Features
- 36. Hidden Features
- 37. Hidden Features
- 41. A line may be fore-shortened
- 43. Meaning of Areas in Orthographic Views B B B Foreshortened Surface Surface in True shape
- 44. Meaning of Areas in Orthographic Views C C D D C D Curved Surface Tangent Surfaces
- 45. Projections of Areas Some areas are projected in true shapes, while others are distorted. Areas parallel to picture planes are in true shapes Four types of Areas 1.A surface in true shape 2. A foreshortened surface 3. A smoothly curved surface 4. A combination of tangent surfaces
- 47. An plane surface that appears as a line in one view is normal to that view. It may or may not appear its true shape in the other views.
- 50. Reading Areas
- 51. Reading Areas
- 52. Reading Areas
- 54. Meaning of Lines in Orthographic Views Three possible interpretations: An edge view of a surface An intersection of two surfaces A surface limit - reversal of direction of a curved surface (Surface Limit)
- 56. An intersection of two surfaces
- 58. We next illustrate how to read the orthographic drawings. This is done by interpreting the three view to ‘draw’ the represented by those view.
- 59. Reading Lines & Areas Start with a cuboid 3 6 2 7 1 Right front corner is cut away to represent surface 12345 3 1 2 Top front of the upper step is removed to reconcile the slope of 23 in side view. 4 5 Front top is cut away to create a step 1267
- 60. Interpretation of Hidden Lines
- 61. Draw the pictorial views of the object whose three views are shown.
- 62. Draw the pictorial views of the object whose three views are shown.
- 77. Missing Line Exercises In the examples that follow, one or more lines may be missing in (only) one view. Try constructing a pictorial view to determine what line(s) are missing.
- 78. Missing Line Exercises One or more lines may be missing in (only) one view. Try constructing a pictorial view to determine what line(s) are missing.
- 95. Missing Line Exercises ?
- 99. Sectional Views
- 100. Sectional Views Whenever a representation becomes confused due to too many essential hidden details that it is difficult to interpret, sectional views are employed
- 101. Too many hidden lines Too complicated to interpret
- 103. For this purpose a cutting plane is employed. The shape of the object is clarified by distinguishing between the areas where the cutting plane actually cuts the solid material and the areas where it meets voids.
- 105. Sectional Views Cutting Plane The details of the hub are now clearer.
- 106. Sectional Views A sectional view makes things much clearer.
- 107. Sectional Views
- 108. Sectional Views This does not differentiate cut and uncut portions Note that the cutting plane line is long dash – two short dashes line
- 109. Sectional Views Hatch the solid portions which are exposed freshly by the cutting plane These areas not hatched because the cutting plane does not cut any material here. These represent holes.
- 110. Sectional Views 5/4 ream Clarify the view using sections.
- 113. Full Sections
- 114. Half Sections In many symmetrical objects one can show the internal & the external feature in the same view by considering a plane which cuts only one half the object.