lecture 3 sunday, 03 may 2015 1 engineering graphics 1e7 lecture 3: orthographic projections
TRANSCRIPT
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Lecture 3 Friday 21 April 2023 1
ENGINEERING GRAPHICS1E7
Lecture 3: Orthographic Projections
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Projections (1)• Projections transform points from n
(here, n = 3) dimensional space into a space of dimension less than n (here, n = 2)
• Points to be considered,– Location of object
– Location of observer
– Plane of projection
– Projectors
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Projections (2)Projections
Parallel/Cylindrical
Perspective/Conical
Oblique Orthographic One-Point Three-PointTwo-Point
Cabinet
Other
Cavalier
Multi-view
Axonometric
First-angle Fourth-angle Third-angle Second-angle
Isometric (30°)
Di-metric Trimetric
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Perspective Projections
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Parallel Projections
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Parallel Projections
• Projectors are parallel to each other but not perpendicular to projection plane
• Effective in pictorially representing objects
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Parallel Projections
• Projectors are parallel to each other and perpendicular to the projection plane
• Effective in technical representation of objects
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Axonometric
The object is tilted with all three coordinate axes are visible in any one view
(PP projection plane)
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Orthographic (Orthogonal)
The object is at rest and two coordinate axes are visible in any one view
(PP projection plane)
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Multiview Projections
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Multiview Projections
• Front surfaces of object is parallel to plane of projection
• Projectors or line of sights are perpendicular to projection plane
• Projectors are parallel to each other and originate from any point on object
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The six views
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Angles
• First angle projection – European System
• Third angle projection – American System
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Sketching Views (1)
• Measure the overall width, depth and height of the object
STEP 1:
• Draw the construction (thin) lines following the number sequence
STEP 2: Top ViewFront View
Right Side View
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Sketching Views (2)
• Draw all the details using blocks
STEP 3:
• Sketch the circles and corners using compass
STEP 4:
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Sketching Views (3)
• Draw the centre lines, hidden lines
STEP 4:
•Lighten the construction lines and thicken the final lines.
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First Angle Projection
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First Angle Projection 1
How to draw plan and elevation?
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First Angle Projection 2
How to draw end view?
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First Angle Projection 3
Points to remember:
• The ‘front view’ (or elevation) is the view with maximum information.
•The ‘plan’ is below the ‘elevation’ (in projection).
•The ‘end view’ is placed on the right if viewed from left side of object and on the left if viewed from right side.
•‘End view’ and plan face inwards from ‘elevation’.