2. Introduction to Orthographic Projections Introducing Orthographic Projections as the language of engineering designers
3.
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
6.
7. The intersections of the projectors with the picture plane are the projections of the points from which the projectors emanate.
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
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
46.
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.
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)
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
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.
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
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.
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.
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.