1. Lecture 2: 2-D Transformation and Projection Multi-view Drawing
PTT 105/3 Engineering Graphicss

2. PTT 105/3 Engineering Graphics
Outline
Projection Theory
Multi-view Projection
Principle views & View placement
Projection angle
Detail drawing: 1view, 2 view, 3 view drawing
Creating multi-view drawing
View Selection
Line convention
PTT 105/3 Engineering Graphicss

3. PTT 105/3 Engineering Graphics
Projection Theory
Engineering and technical graphics are depend on projection methods.
Two methods commonly used:
Parallel: object positioned at infinity & viewed from multiple points on an imaginary line, parallel to the object.
Perspective: object positioned at finite distance & viewed from a single point.
PTT 105/3 Engineering Graphicss

4. Parallel- all LOS are parallel Perspective- all LOS start at a point.
Projection theory comprises of principles used to graphically represent 3D objects on 2D media based on 2 variables:
Line of Sight (LOS): an imaginary ray of light between an observer’s eye and an object.
Parallel- all LOS are parallel
Perspective- all LOS start at a point.
Plane of projection: an imaginary flat plane where the image created by LOS is projected.
PTT 105/3 Engineering Graphicss

5. Orthographic Projection
A parallel projection technique
The projection plane is placed between observer and object.
The projection plane is also perpendicular to the parallel line of sight.
PTT 105/3 Engineering Graphicss

6. Multi-view projection
Multi-view projection is an orthographic projection for which the object is behind the plane of projection.
PTT 105/3 Engineering Graphicss

7. Multi-view drawings i. Employ multi-view projection technique
ii. Generally 3 views of an object are drawn
iii. Each view is a 2D flat image
PTT 105/3 Engineering Graphicss

8. Example: Multi-view Projection
PTT 105/3 Engineering Graphicss

9. Multi-view Lines
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10. Multi-view: Planes
PTT 105/3 Engineering Graphicss

11. Multi-view: Planes
PTT 105/3 Engineering Graphicss

12. Multi-view: 6 Principle Views
The 6 principle views are the six mutually perpendicular views that are produced by six perpendicular planes of projection.
Image an object is suspended in a glass box, the 6 sides become projection plane showing the six views.
PTT 105/3 Engineering Graphicss

13. The views are laid flat by “unfolding the glass box”
This forms the basis of two important multi-view drawing standard:
Alignment of views
Fold lines
Top and bottom views are all aligned vertically & share the same height with dim.
Rear, left, front and right side are aligned horizontally & share same height with dim.
PTT 105/3 Engineering Graphicss

14. Fold lines are imaginary hinged edges of the glass box
i. The fold line between the top & front views is labeled H/F
ii. The distance from a point in front view to the H/F is the same as the distance from the corresponding point in the top view to the H/F fold line.
PTT 105/3 Engineering Graphicss

15. View Placement
PTT 105/3 Engineering Graphicss

16. View Placement
The arrangement of views may vary as shown, where the top view is considered the central view.
PTT 105/3 Engineering Graphicss

17. Angle Projection
There are two standard arrangement of all six views of an object
i. First-angle projection
ii. Third-angle projection
Each uses different symbol
The names are derived from the method used to view the object being drawn
PTT 105/3 Engineering Graphicss

18. In 1st angle projection, the object is placed in the first quadrant.
In 3rd angle projection, the object is placed in third quadrant.
PTT 105/3 Engineering Graphicss

19. Rules: Symbols 1st angle projection 3rd angle projection
View from above is placed underneath
View from above is placed above
View from below is placed above
View from below is placed below
View from left is placed on right
View from left is placed on left
View from right is placed on left
View from right is placed on right
(a) 1st angle projection (b) 3rd angle projection
PTT 105/3 Engineering Graphicss

20. Example: 1st and 3rd angle view projection
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21. 1, 2 and 3 view drawing
PTT 105/3 Engineering Graphicss

22. Step in creating multi-view drawing
PTT 105/3 Engineering Graphicss

23. Before start drawing, produce sketch on rough paper
i. Decide on front view and projection angle
ii. Obtain the overall width, height and depth
iii. Place the views (in block)
iv. Determine approximate space between the views
v. Sketch the component, place dimensions
PTT 105/3 Engineering Graphicss

24. Creating 3-view drawing
Draw border/frame, title block, etc.
Draw border, title block
Locating the view
i. should be approx. in
centre
ii. distance between view
= total length available
– view length / 3
Drawing projection lines
PTT 105/3 Engineering Graphicss

25. Creating 3-view drawing
PTT 105/3 Engineering Graphicss

26. Creating 3-view drawing
2. Light construction of the
views
Draw light/thin horizontal & vertical lines accordingly for front view
Draw center lines and hidden lines as final
Draw top (or side) view
Project top view (or side) from front view using thin, light construction line
Draw side (or top) view
Project side view (or top) from front view and top (or side) view
All arcs and circles should be lined (final) at this stage
PTT 105/3 Engineering Graphicss

27. Creating 3-view drawing
3. Lining in of the views
To darken all visible edges (lines that represent a hard edge)
Done using thick, black pencil (0.5mm, 2B)
Should be done systematically for 3 views
Start with horizontal line at the top of the top/plan view, working down the page using T-square
From left hand side, working across the page, line in all vertical lines, using T-square and set square
Projection lines may be left on the drawing if they are light
PTT 105/3 Engineering Graphicss

28. Creating 3-view drawing
4. Write dimensioning, notes, annotation, etc.
Be aware of redundant dimensioning
5. Complete drawing by writing the rest of title block, parts list & revision table, and others
PTT 105/3 Engineering Graphicss

29. View Selection 4 basic decisions:
1. Determine the best position. The object must be positioned such a way that the surface of major features are either perpendicular or parallel to glass planes
PTT 105/3 Engineering Graphicss

30. View Selection
2. Define the front view. Should show the object in natural state and show most features
PTT 105/3 Engineering Graphicss

31. View Selection
Determine the minimum number of views needed to completely describe the object.
Determine other views that fewest number of hidden lines
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32. Line Convention
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33. Line Convention
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34. THANK YOU…
PTT 105/3 Engineering Graphicss