Multi-view Projection Drawing

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Multi-view Projection Drawing

• CHAPTER 5

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Content

• Projection Theory
• Multi-view Projection Planes Lines
• Multi-view 6 principle views View placement
• Projection angle 1st angle 3rd angle
• Detail drawing 1-view 2-view 3-view drawing
• Creating multi-view drawing
• View selection
• Line convention
• Common feature in multi-view drawing

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5.1 Projection Theory

• Engineering and technical graphics are dependent
  on projection methods
• 2 methods primarily used
• Parallel object positioned at infinity viewed
  from multiple points on an imaginary line
  parallel to the object
• Perspective object position at finite distance
  viewed from a single point

Parallel
Perspective
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5.1 Projection Theory

• Projection theory comprises of the principles
  used to graphically represent 3D objects on 2D
  media
• Based on 2 variables
• Line of Sight (LOS) an imaginary ray of light
  between and observers 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.

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5.1 Projection Theory

• Orthographic projection a parallel proj.
  technique where the proj. plane is placed
  between observer and object and is perpendicular
  to the parallel lines of sight

Changing view point
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5.1 Projection Theory
Projections
Perspective Projections
Parallel Projections
Oblique Projections
Orthographic Projections
Linear Perspective
Aerial Perspective
Multiview Projections
Axonometric Projections
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5.1 Projection Theory Multi-view
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5.1 Projection Theory
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5.2 Multi-view projection

• Multiview projection is an orthographic
  projection for which the object is behind the
  plane of projection, and the object is orientated
  such that only two of its dimensions are shown.

object
Projection plane
Orthographic projection Front View
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5.2 Multi-view projection

• Multiview drawings
• Employ multiview projection technique
• Generally three views of an object are drawn
• Each view is a 2D flat image

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5.2 Multi-view projection
Right side view
Top view
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5.2 Multi-view projection
Multiview drawing of an object
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5.2 Multi-view Lines

• Lines in multi-view projection

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5.2 Multi-view Lines
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5.2 Multi-view Planes
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5.2 Multi-view Planes
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5.3 Multi-view The 6 principal views

• The 6 principal views are the six mutually
  perpendicular views that are produced by six
  mutually perpendicular planes of projection
• Imagine an object is suspended in a glass box,
  the 6 sides become projection plane showing the
  six views

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5.3 Multi-view The 6 principal views

• The views are front, rear, top, bottom, left and
  right
• Front view
• the 1st to be established
• Shows the most features
• All other views are based on the orientation
  chosen for the front view

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5.3 Multi-view The 6 principal views

• The views are laid flat by unfolding the glass
  box
• This forms the basis of two important multiview
  drawing standard
• Alignment of views
• Fold lines
• Top, front and bottom views are all aligned
  vertically share the same width dim.
• Rear, left, front and right side are aligned
  horizontally share same height dim.

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5.3 Multi-view The 6 principal views

• Fold lines are the imaginary hinged edges of
  the glass box
• The fold line between the top front views is
  labeled H/F
• 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

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5.4 Multi-view View Placement

• The three-view drawing is the standard used in
  engineering, as normally other three principal
  views are mirror images
• The standard views top, front right
• The width dim. are aligned between the front
  top view using vertical projection lines
• The height dim. are aligned between the front
  right side view, using horizontal projection
  lines
• The depth dim. are aligned between top right
  side view, using scale, miter line or compass

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5.4 Multi-view View Placement
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5.4 Multi-view View Placement

• The arrangement of views may vary as shown,
  where the top view is considered the
  central view

Alternate view arrrangement
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5.4 Multi-view
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5.5 1st- and 3rd-angle projection

• There are two standard arrangement of all six
  views of an object
• First-angle projection
• Third-angle projection
• Each uses a different symbol
• The names are derived from the method used to
  view the object being drawn

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5.5 1st- and 3rd-angle projection

• In first-angle projection, the object is placed
  in the first quadrant
• In third-angle projection, the object is placed
  in the third quadrant

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5.5 1st- and 3rd-angle projection

• Brief rules

• Symbols

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5.5 1st- and 3rd-angle projection
Third-angle projection
First-angle projection
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5.6 One-view two-view drawings
One-view
Two-view
Three-view
One-view
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5.6 Two-view drawings

• Examples

Two-view
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5.6 Two-view drawing

• Creating 2-view sketching

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5.6 Two-view drawing
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5.6 Steps in creating multi-view drawing
SKETCH
DRAW
READ
Decide Projection angle, Location of view, Scale
Prepare paper -gt Draw border -gt Title block -gt
etc.
Construct view (outline) -gt Using thin pencil -gt
Measure place view -gt Project all views -gt
Final lining hidden centre lines (thin), arcs
circles (thick)
Lining views -gt Line in the rest of the lines -gt
Start from top left -gt Construction lines may be
left if thin enough
Finish drawing -gt Dimension, notes, etc. -gt
Finish off title block, etc.
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5.6 3-view dwg

• Before start drawing, produce sketch on rough
  paper
• Decide on front view and projection angle
• Obtain the overall width, height and depth
• Place the views (in block)
• Determine approx. space between the views
• Sketch the component, place dimensions

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5.6 Creating 3-view drawing

• (1) Drawing of border/frame and location of view
• (2) Light construction of view (inc. title block
  frame)
• (3) Lining in the views
• (4) Dimensioning and inserting of any subtitles
  and notes
• (5) Drawing title block, parts list and revision
  table

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5.6 Creating 3-view drawing

• (1) Draw border/frame, title block, etc.
• Draw border, title block
• Locating the view
• should be approx. in centre
• distance between view
• (total length available
• view length) / 3
• Drawing projection lines

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5.6 Creating 3-view drawing

• Projecting views

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5.6 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

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5.6 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 very light

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5.6 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.

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5.7 View Selection

• 4 basic decisions
• (1) Determine the best position. The object must
  be positioned in such a way that the surface of
  major features are either perpendicular or
  parallel to glass planes.

(1)
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5.7 View Selection

• (2) Define the front view. Should show the object
  in natural state and show most features.

(2)
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5.7 View Selection

• (3) Determine the minimum number of views needed
  to completely describe the object.
• (4) Determine other views that have fewest number
  of hidden lines

(3)
(4)
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5.8 Line convention

• Hidden lines

Centre lines
Hidden features
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5.8 Line convention

• Hidden lines

Drawing conventions for hidden lines
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5.9 Primitive shape
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5.9 Primitive shape
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5.9 Runouts
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5.10 Exercise Missing views
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5.10 Exercise Missing views
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END OF CHAPTER 5