CHAPTER 3. MULTI-VIEW DRAWING 1.pptx

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1. ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITY Collage of Electrical and Mechanical Engineering Department of Mechanical Engineering COURSE :ENGINEERING DRAWING [ Meng1011]

2. CHAPTER 3 MULTI-VIEW DRAWING

3. TOPICS SYSTEM OF PROJECTION CHOICE OF VIEWS LAYING OUT DRAWINGS AND RELATION BETWEEN HEIGHT, DEPTH AND WIDTH ONE VIEW, TWO VIEW AND THREE VIEW DRAWINGS PROJECTION OF CURVE ,INCLINDE, OBLIQUE AND INTERSECTION AND TANGENTS LINE CONVENTION

4. 3.1 SYSTEM OF PROJECTION

5. SYSTEM OF PROJECTION A plane of projection ( POP ) is a plane on which a particular view is projected. Three such planes, perpendicular to each other, are called principal planes or reference planes (RP). When the observer looks at the object from the front, the view obtained is called the front view or elevation and is seen on the vertical plane (VP)/ frontal plane (FP). When the observer looks at the object from above, the view obtained is called top view or plan and is seen on the horizontal plane (HP). When the observer looks at the object from side, i.e., from his left-hand side or right-hand side, the view obtained is called side view and is seen on the profile plane (PP).

6. SYSTEM OF PROJECTION LEFT PROFILE PLANE HORIZONTAL PLANE FRONTAL PLANE RIGHT PROFILE PLANE FRONT VIEW

7. HORIZONTAL PLANE FRONTAL PLANE SYSTEM OF PROJECTION RIGHT PROFILE PLANE LEFT PROFILE PLANE FRONT VIEW

8. First Angle Projection : the object is placed in the first quadrant . This means that the Vertical Plane is behind the object and the Horizontal Plane is underneath the object . The object lies in between the observer and the planes of projection . SYSTEM OF PROJECTION Third Angle Projection : The Object is placed in the Third Quadrant . This means that the Vertical Plane is in front of the object and the Horizontal Plane is above the object. The Plane of projection lie between the object and the observer .

9. SYSTEM OF PROJECTION 1. First angle system 2. Third angle system First Quadrant Third Quadrant - European country - ISO standard - Canada, USA, Japan, Thailand

10. 1 st angle system 3 rd angle system SYSTEM OF PROJECTION

11. 1 st angle system 3 rd angle system Folding line Folding line Folding line Folding line   SYSTEM OF PROJECTION

12. 1 st angle system 3 rd angle system Front View Front View Right Side View Right Side View Top View Top View SYSTEM OF PROJECTION

13. First angle system Third angle system SYSTEM OF PROJECTION Projection Symbo ls

14. SYSTEM OF PROJECTION d 1.7 d 2.2 d Suggested proportion Projection Symbols

15. 3.2 CHOICE OF VIEWS

16. CHOICE OF VIEWS 16 Most commonly used views Front View Top View Right Side View Steps for Choice of views Orient the object to the best position Select the front view Select adjacent views

17. STEP 1 : Orient the Object The object should be placed in its natural position . NO ! The object should presents its features in actual size and shape in orthographic views. GOOD 17 CHOICE OF VIEWS

18. STEP 2 : Select a Front View The object’s longest dimension should be presented as a width . Inappropriate First choice GOOD Second choice Waste more space 18 CHOICE OF VIEWS Most descriptive view is typically designated as the Front View

19. Inappropriate The adjacent views that are projected from the selected front view should appear in its natural position. STEP 2 : Select a Front View 19 CHOICE OF VIEWS

20. STEP 2 : Select a Front View Choose the view that have the fewest number of hidden lines . GOOD Inappropriate 20 CHOICE OF VIEWS

21. STEP 3 : Select an Adjacent View GOOD Inappropriate Inappropriate GOOD Choose the view that have the fewest number of hidden lines . 21 CHOICE OF VIEWS

22. Choose the minimum number of views that can represent the major features of the object. STEP 3 : Select an Adjacent View Necessary Necessary Hole’s location can be specified on the same view. Difficult to interprete. Easy to understand 22 CHOICE OF VIEWS

23. Choose the views that are suitable to a drawing space . STEP 3 : Select an Adjacent View POOR Not enough space for dimensioning. 23 CHOICE OF VIEWS

24. Choose the views that are suitable to a drawing space . STEP 3 : Select an Adjacent View GOOD 24 CHOICE OF VIEWS

25. Example : View selection Shape description Size description F.V. W D  W H  D mislead to…     F.V. & T.V. Three views F.V. & R.S.V. H 25 CHOICE OF VIEWS

26. 3.3 ONE VIEW, TWO VIEW AND THREE VIEW DRAWINGS

27. ONE-VIEW DRAWING Thin objects can be described with only one view: Depth is given in a note eg . Flat part having a uniform thickness. Unnecessary These 2 views provide only information about the part thickness ! 1 Thick 27

28. ONE-VIEW DRAWING Simple objects can be described with one views eg . Cylindrical-shaped part. Unnecessary Repeat ! Unnecessary 28

29. TWO-VIEW DRAWING There exists an identical view. Repeat ! Unnecessary 29

30. The 3 rd view has no significant contours of the object. TWO-VIEW DRAWING Unnecessary 30

31. TWO-VIEW DRAWING Unnecessary The 3 rd view has no significant contours of the object . 31

32. 32 Necessary Necessary Hole’s location can be specified on the same view. Difficult to interprete. Easy to understand THREE-VIEW DRAWING Complex objects require three views to describe its shape

33. 33 THREE-VIEW DRAWING Complex objects require three views to describe its shape

34. 3.4 LAYING OUT DRAWINGS

35. 35 LAYING OUT DRAWINGS Hand Layout of a metric three-view drawing

36. 36 LAYING OUT DRAWINGS Views should be visually balanced within the working space Draw border ( 20mm from left and 5 mm from each 3 sides ) and title block using light construction lines STEP 1 A4 Border line 20 5 28 5 5

37. 37 Determine space desired between the front and right-side views (C ), and front and Top views (C) say 20 or 30 mm. Add STEP 2 To set equal distances to the paper edge, subtract this total from the sheet width ( Ws =185), and height (Hs=259) then divide the remaining number by two. A = ( Ws - H)/2 B = (Hs - V)/2

38. 38 1 st Angle Projection Set off vertical and horizontal spacing measurements with light tick marks along the edge of the sheet and draw construction lines STEP 3 Dimension take from the object

39. 39 STEP 3 Set off vertical and horizontal spacing measurements with light tick marks along the edge of the sheet and draw construction lines Dimension take from the object 3 rd Angle Projection

40. 40 Construct the views : add hidden lines and darken final lines . STEP 4 1 st Angle Projection

41. 41 Construct the views : add hidden lines and darken final lines . STEP 4 3 rd Angle Projection

42. 1 st Angle Projection LAYING OUT DRAWINGS

43. 3 rd Angle Projection LAYING OUT DRAWINGS

44. 44 The three-view drawing is the standard used in engineering, as normally other three principal views are mirror images . The standard views – TOP, FRONT and RIGHT . All objects have 3 dimensions Height : Distance from top to bottom Width : Distance from side to side Depth: Dista nce from the front to back R/N B/N HEIGHT, DEPTH AND WIDTH Height Width Depth

45. The width dimensions are aligned between the front and top view using vertical projection lines. The height dimensions are aligned between the front and side views, using horizontal projection lines. The depth dimensions are aligned between top and side views , using scale , miter line or compass . 45 R/N B/N HEIGHT, DEPTH AND WIDTH

46. 46 Top View Front View RS.View Width Height Depth Width Height Depth R/N B/N HEIGHT, DEPTH AND WIDTH

47. 3.5. LINE CONVENTION

48. PRECEDENCE OF LINE Visible line Order of importance Hidden line Center line

49. HIDDEN LINE PRACTICE Hidden line should join a visible line, except it extended from the visible line. Correct No ! Join Leave space

50. Correct No ! Hidden line should join a visible line, except it extended from the visible line. Leave space Leave space HIDDEN LINE PRACTICE

51. Hidden line should intersect to form L and T corners. Correct No ! L T HIDDEN LINE PRACTICE

52. Hidden arcs should start on a center line. HIDDEN LINE PRACTICE

53. Make a hidden line “jump ” a visible line when possible . Draw parallel hidden lines so that the dashes are staggered, as in bricklaying . HIDDEN LINE PRACTICE

54. When two or three hidden lines meet at a point, join the dashes, as shown for the bottom of this drilled hole . The same rule of joining the dashes when two or three hidden lines meet at a point applies for the top of this countersunk hole .. HIDDEN LINE PRACTICE

55. CENTER LINE PRACTICE In circular view, short dash should cross at the intersections of center line. For small hole, center line is presented as thin continuous line. Center line should not extend between views. Leave space Leave space

56. Leave the gap when centerline forms a continuation with a visible or hidden line Leave space Leave space Leave space Leave space Center line should always start and end with long dash. CENTER LINE PRACTICE

57. 3.6. PROJECTION OF CURVE ,INCLINDE, OBLIQUE AND INTERSECTION AND TANGENTS

58. PROJECTION OF CURVED EDGES Curved edges project as straight lines on the plane to which they are perpendicular Curved edges project as curved lines on the planes to which they are parallel or inclined

59. PROJECTION OF NORMAL SURFACES Normal surfaces appear as an edge in two opposite principal views, and appear a surface in all other principal views. 59

60. PROJECTION OF INCLINED SURFACES Inclined surfaces appear as an edge in two opposite principal views, and appear foreshortened (not true size) in all other principal views. 60

61. PROJECTION OF OBLIQUE SURFACES Oblique surfaces do not appear either as an edge or true size in any principal view. 61

62. PROJECTION OF INTERSECTIONS & TANGENCIES Where a curved surface is tangent to a plane surface, no line should be shown where they join

63. PROJECTION OF INTERSECTIONS & TANGENCIES Where a plane surface intersects a curved surface, an edge is formed

64. PROJECTION OF INTERSECTIONS & TANGENCIES Where the plane surface is horizontal or vertical, exceptions to these rules may occur

65. Example 1. Using the first angle projection system, draw the three principal view of the object whose pictorial drawings are given below.

66. 1 ST ANGLE PROJECTION 80 75 60

67. Example 2. Using the first angle projection system, draw the three principal view of the object whose pictorial drawings are given below.

68. 1 ST ANGLE PROJECTION 60 50 40