Multi-view Projection Drawing CHAPTER 5

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

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

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 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.

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

Perspective Projections 5.1 Projection Theory Projections Perspective Projections Parallel Projections Linear Perspective Aerial Perspective Oblique Projections Orthographic Projections Axonometric Projections Multiview Projections

5.1 Projection Theory: Multi-view

5.1 Projection Theory

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

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

5.2 Multi-view projection Right side view Top view

5.2 Multi-view projection Multiview drawing of an object

5.2 Multi-view: Lines Lines in multi-view projection

5.2 Multi-view: Lines

5.2 Multi-view: Planes

5.2 Multi-view: Planes

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

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

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.

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

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

5.4 Multi-view: View Placement

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

5.4 Multi-view

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

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

5.5 1st- and 3rd-angle projection Brief rules 1st angle projection 3rd angle projection View from above is placed underneath View from above is place 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 Symbols

5.5 1st- and 3rd-angle projection Third-angle projection First-angle projection

5.6 One-view & two-view drawings Three-view One-view

5.6 Two-view drawings Examples Two-view

5.6 Two-view drawing Creating 2-view sketching 1 2

5.6 Two-view drawing 3 4

5.6 Steps in creating multi-view drawing SKETCH DRAW READ Decide: Projection angle, Location of view, Scale Prepare paper -> Draw border -> Title block -> etc. TOP FRONT SIDE height depth y y = (total length – height – depth)/3 Construct view (outline) -> Using thin pencil -> Measure & place view -> Project all views -> Final lining: hidden & centre lines (thin), arcs & circles (thick) Lining views -> Line in the rest of the lines -> Start from top left -> Construction lines may be left if thin enough Finish drawing -> Dimension, notes, etc. -> Finish off title block, etc.

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

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

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

5.6 Creating 3-view drawing Projecting views

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

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

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.

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)

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

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)

5.8 Line convention Hidden lines Centre lines Hidden features

5.8 Line convention Hidden lines Drawing conventions for hidden lines

5.9 Primitive shape

5.9 Primitive shape

5.9 Runouts

5.10 Exercise: Missing views

5.10 Exercise: Missing views

END OF CHAPTER 5