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Engineering drawing chapter 03 orthographic projection.
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- 2. Line convention Multiview drawing Projectiontheory Contents
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- 4. Purpose To graphically representa 3-D object on 2-D media (paper, screen etc.). Object (3D) placing on the paper (2D) Transparent plate is placed between object and observer’s eyes. Object’s features are transferred through projection. Inconvenient to communicate A view of an object on 2D media Convenient to communicate
- 5. Concept A projection theoryis based on 2 variables: 1) Line of sight 2) Plane of projection (image or picture plane) Plane of projection is an imaginary flat plane upon which the image created by the LOS is projected. Line of sight (LOS) is an imaginary ray of light between an observer’s eye and an object.
- 6. Line of sight Linesof sight can be parallel or converge. Converge projectionParallel projection Play Play
- 7. Line of sight Theparallel projection lines can be normal (orthogonal) or oblique to the plane of projection. ObliqueOrthogonal Play Play In this course, we consider only a parallel and orthogonal projection, i.e. orthographic projection.
- 8. Image on aprojection plane. Rotate Tilt Multiview drawing shows a 2D view of an object. Axonometric drawing shows a virtual 3D view of an object. View View depends on a relative orientation between an object and a plane.
- 9. Summary : Typesof views Projections ConvergeParallel Orthogonal Oblique AxonometricMultiview Pictorial drawing Perspective drawing Multiview drawing (Later chapter)(This chapter)
- 10. View comparison Pictorial drawing Perspectivedrawing Multiview drawing Difficult to create Easy to visualize. Shape and angle distortion Object looks more like what our eyes perceive. Size and shape distortion Right angle becomes obtuse angle. Circular hole becomes ellipse Distorted width Accurately presents object’s details, i.e. size and shape. Require training to visualization. Advantage DisadvantageType
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- 12. Multiview drawing isa set of related images that are created by viewing the object from a different direction. Definition Width Depth Height Width Height Depth Depth Adjacent view(s) is needed to fulfill the object description.
- 13. 1. Revolve theobject with respect to observer Methods 2. The observer moves around the object. Front view Right side view Top view Right side view Top view play play Front view Glass box concept
- 14. Glass box :Revolution of the planes of projection Bottom view Left side view Rear view
- 15. Height Width Depth Relative orientation ofviews Left side view Right side view Bottom view Top view Rear view Front view
- 16. Summary : Problemsolving steps 1 2 3 4 Given
- 17. Object features Edge isa line that represent the boundary between two faces of an object. Surface limit is a line that represents the last visible part of the curve surface. Prism Cylinder Sphere No edges! Surface is an area that are bounded by edges or surface limit. Surface can be plane or curve. These features will appear as lines in a multiview drawing.Note
- 18. Class activity :Object’s features 1 2 3 4 5 6 7 8 Identify name of the features denoted by a NO. 1 to 9? 1 2 3 4 5 6 7 8 Edge Surface limit Surface Skip test Next slideReset all
- 19. B AF BF BRAR AT BT Projectionof a normal line A Play Glass box concept Multiview drawing AR BR AT BT AF BF
- 20. Projection of anormal plane Play Glass box concept Multiview drawing
- 21. Projection of anobject Play Glass box concept Multiview drawing Do the same procedures for all remaining edges (or planes) Hidden line is used to show existence of a hidden edge.
- 22. Projection of aninclined line Play Glass box concept Multiview drawing AF BF AF B A BF AR BR AR BR AT BT AT BT
- 23. Projection of aninclined plane Play Glass box concept Multiview drawing
- 24. Projection of anobliqued line Play Glass box concept Multiview drawing AF B A BF AR BR AT BT AF BF AR BR AT BT
- 25. Projection of anobliqued plane Play Glass box concept Multiview drawing
- 26. Projection of acurve line Play Glass box concept Multiview drawing AFBF CF BR AT BT CT AR CR B A C AFBF CF BRAR CR AT BT CT
- 27. Projection of acurve surface Play Glass box concept Multiview drawing
- 28. Transferring a depth: Direct measurement 0123 27 0 1 2 3 Prefer space between front and side views 27
- 29. Transferring a depth: miter line Prefer space between front and side views miter line 45o
- 30. Projection of anobject having curved surface and plane In the case of intersection, an edge exists and becomes a line in a multiview drawing Curved surface can either tangent or intersect with an adjacent plane or curve surface. In the case of tangential, there is no edge and line in a multiview drawing I I T T T I
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- 34. 3D representation of anobject Suggestion for practicing 1 Given Choose lines (or areas) Multiview drawingRepresent each features by a line 2Choose features 1 12 Match each lines (or areas) to features Identify line (or plane) types, i.e. normal, inclined, and obliqued. 3 Try to relate the object’s features to the lines in a multiview drawing, i.e. interpret the meaning of lines.
- 35. Suggestion for practicing2 Modify the object’s features of a given object, then observe what’s changed on a multiview drawing. Given 3D representation of a simple object Modified object
- 36. Self study :Type of planes Normal plane Click on any area of a given object. You will get the type of plane. Inclined plane Curve surface Skip
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- 38. Line convention Precedence ofcoincide lines Hidden line drawing Center line drawing
- 39. Precedence of line Whenlines coincide with each other, the more important lines cover up the other lines. Order of importance (highest to lowest) - visible line - hidden line - center line - construction line. Line convention Play
- 40. What is anappropriate line type to replace the lines NO. 1-4? 1 2 3 V H C Skip test Next slideReset all “V” denotes visible line “H” denotes hidden line “C” denotes center line Class activity : Precedence of lines 1 2 3 4 4
- 41. Hidden line drawing Hiddenline should join a visible line, except it extends from a visible line. join space join space space space
- 42. Hidden line drawing Intersectionbetween hidden lines should form L, T, V or Y corner. L T inside V Y L T
- 43. A curve hiddenline should start on a center line. Hidden line drawing Line convention
- 44. Center line drawing Ina circular view, short dash of a center line should cross at the center of the circle or arc. Center line should always start and end with long dash. Center line should not extend between views. Leave space Leave space Play Play 3~4 mm 3~4 mm
- 45. Center line drawing Fora small hole, a center line is presented as a thin continuous line. Leave a gap when centerline forms a continuation with a visible or a hidden line. Play Leave space Leave space Leave space Line convention
- 46. Class activity :Hidden line drawing correct wrong correct wrong Skip test Next slideReset all