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# Lesson 11-isometric-projections-i

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• ### Lesson 11-isometric-projections-i

1. 1. ISOMETRIC PROJECTION Part I Prof.T.JEYAPOOVAN Department of Mechanical Engineering Hindustan Institute of Technology and Science Chennai-603103, India www.EGlive.in
2. 2. Isometric axes and Isometric Line • Isometric view or projection shows all three dimensions of an object which are useful to understand and visualize an object. • There are 3 isometric axes with an angle of 120º between them. • Any line drawn parallel to an isometric axis is called isometric line. www.EGlive.in
3. 3. Isometric View and Isometric Projection • To draw isometric view true dimensions are used. • Isometric view is used for single solid. • To draw isometric projection, isometric dimensions are used which is 0.82× True length. • Isometric projection is used for combination of solids. • Consider isometric projection and isometric view of a rectangular prism shown in fig. www.EGlive.in
4. 4. Box Method • Box method is used to draw isometric view or projection of an object. • A rectangular or square box of suitable size is used to enclose the object in such a way that some of the corners or edges touch the box sides. • Construct the isometric view/projection of the box using the isometric axes. www.EGlive.in
5. 5. Example 1: A hexagonal prism of base side 30 mm and axis length 60 mm is resting on HP on its base with a side of base parallel to VP. Draw the isometric view of the prism. • Draw the TV and project the FV of the prism. • A rectangular box of exact size is used to enclose the prism in TV such a way that some of the corners or edges touch box sides. • Draw two isometric axes at 30° and construct the box in isometric. • Measure the corners of the prism from TV and mark them on the sides of the box in isometric. • Darken the top, left and right edges of the prism to complete the isometric view. www.EGlive.in
6. 6. Example 2: Draw the isometric view of a hexagonal prism of base side 30 mm and axis length 60 mm rests on HP on one of its rectangular faces with its axis perpendicular to VP. • Draw FV and TV of the prism. • A rectangular box of exact size is constructed horizontally to enclose the prism in such a way that some of the corners or edges touch the box sides. • Draw one isometric axis at 30° and another vertical to construct the box horizontally in isometric • Measure the corners of the prism from FV and mark them on the sides of the box. • Darken the right, left and top edges of the prism to complete www.EGlive.in the isometric view.
7. 7. 4-Centre Method • 4-Centre method is used to draw an ellipse in isometric for a circle. • Construct the rhombus in isometric using circle diameter as sides. • Draw arcs using 4-centres m,n,1 and 3 with radius shown fig. • For isometric projection, isometric scale is used to draw the rhombus. www.EGlive.in
8. 8. Example 3: Draw the isometric view of a vertical cylinder of base diameter 50 mm and axis length 60 mm. • Draw TV and FV of the cylinder. • A square box of exact size is used to enclose the cylinder. • Construct the box in isometric. • Use 4-centre method to draw the top base as an ellipse in isometric and repeat the same procedure for bottom base. • Draw left and right extreme generators. • Darken the top, left and right visible portion of the cylinder to complete the isometric view. www.EGlive.in
9. 9. Example 4: Draw the isometric view of a vertical cylinder of base diameter 50 mm and axis length 60 mm. • Draw FV and TV of the cylinder. • A square box of exact size is used to enclose the cylinder. • Construct the box horizontally in isometric. • Use 4-centre method to draw the front base as an ellipse in isometric and repeat the same procedure for rear base. • Draw top and bottom generators. • Darken the top, left and right visible portion of the cylinder to complete the isometric view. www.EGlive.in
10. 10. Example 5: A pentagonal pyramid of base side 30 mm and axis length 65 mm is resting on HP on its base with a side of base perpendicular to VP. It is cut by a plane inclined at 30° to HP and perpendicular to VP and passes through a point at a distance 30 mm from the apex. Draw the isometric view of the remaining portion of the pyramid. • Draw TV, FV of pyramid and cutting plane at 30° to XY. • Draw a rectangle to enclose base of pyramid in TV and rhombus in isometric to mark base corners. • Produce a new corner to touch the side of rectangle like m, then mark it on the sides of rhombus. • Draw a line from m parallel to an isometric axes. • Measure the horizontal distance from TV and mark in isometric, similarly get other new points in isometric. • Darken the visible edges to complete the isometric view. www.EGlive.in
11. 11. Tips to draw Isometric View/ Projection • Draw the TV and FV of the solid and are used to complete isometric view/projection. But it is not compulsory to draw TV & FV, box can be directly constructed to draw the isometric view/projection. • Hidden lines used for invisible edges are not drawn in isometric view/projection. • In isometric view/projection, marking and dimensioning may be omitted and the drawing of the three dimensional object is shown clearly by using dark lines for visible edges. www.EGlive.in
12. 12. REFERENCE BOOKS 1. Jeyapoovan T, “Lesson Plans for Engineering Graphics”, 2010, Vikas Publishing House Pvt Ltd, New Delhi. 2. Jeyapoovan T, “Engineering Drawing and Graphics”, 2011, Vikas Publishing House Pvt Ltd, New Delhi. www.EGlive.in
13. 13. End of Lesson 11 Thank You www.EGlive.in