# Projection Theory Projection is a method to represent

• Slides: 55

Projection Theory Projection is a method to represent 3 D object into 2 D plane(paper…etc. ) Object View Therefore we need at least tow or three views (except for especial cases)

Projection Parameters The projection theory is based on 3 variables: 1 - center sight point(station point) 2 - Line of sight 3 - Plane of projection Therefore View is the image on a projection plane

Lines of sight Lines of Parallel Projection Play Convergent Projection Play

Lines of sight The parallel projection lines can be normal (orthogonal) or oblique to the plane of projection. We consider only a parallel and orthogonal projection, i. e. orthographic projection. Orthogonal ﻣﺘﻌﺎﻣﺪ Play Oblique ﻣﺎﺋﻞ Play

Views View depends on a relative orientation between an object and a plane. Normal ﻋﻤﻮﺩﻯ Multiview Drawing Axonometric Drawing Rotation ﺩﻭﺭﺍﻥ Tilting ﺍﻣﺎﻟﺔ

PROJECTION CLASSIFICATION Projections Convergent Parallel Orthogonal Multiview Oblique Axonometric Perspective Drawing Multiview drawing Pictorial drawing

PROJECTION METHOD Perspective Parallel Oblique Axonometric Orthographic Multiview

MULTIVIEW DRAWING

Projection Methods First angle method First quadrant -European countries - ISO standard Third angle method - Canada, USA - Japan, Thailand Transparent Planes ﻣﺴﺘﻮﻳﺎﺕ ﺷﻔﺎﻓﺔ Third quadrant Opaque Planes ﻣﺴﺘﻮﻳﺎﺕ ﻏﻴﺮ ﺷﻔﺎﻓﺔ

First angle system Third angle system (Opaque planes) (transparent planes/glass box)

Arrangement of Views TOP VIEW First angle method LEFT SIDE VIEW FRONT VIEW LEFT SIDE VIEW Third angle method TOP VIEW

Symbols of Projection Systems First angle system Third angle system 1. 7 d d 2. 2 d

Views Dimensions Height Width Depth Width First-angle Projection Width

Projections of points, lines and planes

NOTATIONS FOLLOWING NOTATIONS SHOULD BE FOLLOWED WHILE NAMEING DIFFERENT VIEWS IN ORTHOGRAPHIC PROJECTIONS. OBJECT POINT A LINE AB IT’S TOP VIEW a ab IT’S FRONT VIEW a’ a’ b’ IT’S SIDE VIEW a” a” b” SAME SYSTEM OF NOTATIONS SHOULD BE FOLLOWED INCASE NUMBERS, LIKE 1, 2, 3 – ARE USED.

PROJECTIONS OF A POINT IN FIRST QUADRANT For Tv PICTORIAL PRESENTATION a’ A Y X POINT A IN HP & INFRONT OF VP POINT A ABOVE HP & INFRONT OF VP For a’ PICTORIAL PRESENTATION A For Y Fv Fv Y a’ a X X a For Tv A a For ORTHOGRAPHIC PRESENTATIONS OF ALL ABOVE CASES. Fv above xy, Tv below xy. Fv above xy, Tv on xy. VP Fv on xy, Tv below xy. VP a’ a’ X VP Y X a Y a’ X a a HP HP HP Y Fv

PROJECTIONS OF STRAIGHT LINES INFORMATION REGARDING A LINE means IT’S LENGTH, POSITION OF IT’S ENDS WITH HP & VP IT’S INCLINATIONS WITH HP & VP WILL BE GIVEN. AIM: - TO DRAW IT’S PROJECTIONS - MEANS FV & TV. SIMPLE CASES OF THE LINE 1. A VERTICAL LINE ( LINE PERPENDICULAR TO HP & // TO VP) 2. LINE PARALLEL TO BOTH HP & VP. 3. LINE INCLINED TO HP & PARALLEL TO VP. 4. LINE INCLINED TO VP & PARALLEL TO HP. 5. LINE INCLINED TO BOTH HP & VP. STUDY ILLUSTRATIONS GIVEN ON NEXT PAGE SHOWING CLEARLY THE NATURE OF FV & TV OF LINES LISTED ABOVE AND NOTE RESULTS.

For Tv (Pictorial Presentation) Note: Fv is a vertical line Showing True Length & Tv is a point. a’ . V. P 1. A Line perpendicular to Hp & // to Vp A FV b’ Y For B Orthographic Pattern V. P. a’ Fv b’ X Y Fv TV a b Tv a b X (Pictorial Presentation) 2. . P. V A Line // to Hp & // to Vp Note: Fv & Tv both are // to xy & both show T. L. For Tv . F. V H. P. Orthographic Pattern V. P. b’ B a’ Fv b’ a’ A X Y For b Y Fv a V. X a T. H. P. Tv b

. V. P 3. b’ F. a’ X A . T. V X . a’ Y (Pictorial presentation) b’ F. V B V. A Line inclined to Hp and parallel to Vp Fv inclined to xy V. P. Tv parallel to xy. Y a b T. V. b a H. P. Orthographic Projections 4. A Line inclined to Vp and parallel to Hp . V. P a’ Tv inclined to xy Fv parallel to xy. a’ . F. V b’ A V. P. Ø B (Pictorial presentation) Ø T. V. b’ X Y a a Fv Ø Tv b H. P. b

For Tv A Line inclined to both Hp and Vp 5. F. V Y For Fv A On removal of object i. e. Line AB Fv as a image on Vp. Tv as a image on Hp, a Y For a’ A X T. V. B a’ X V (Pictorial presentation) b’ . P. F. V . . V. P b’ b a T. V. b V. P. b’ FV a’ X Y Orthographic Projections Fv is seen on Vp clearly. To see Tv clearly, HP is rotated 900 downwards, a Note These Facts: Both Fv & Tv are inclined to xy. (No view is parallel to xy) Both Fv & Tv are reduced lengths. (No view shows True Length) TV Hence it comes below xy. H. P. b Fv

FRONT VIEW TOP VIEW SIDE VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW TOP VIEW SIDE VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW TOP VIEW SIDE VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW SIDE VIEW TOP VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW SIDE VIEW TOP VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW TOP VIEW SIDE VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW SIDE VIEW TOP VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW SIDE VIEW TOP VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

FRONT VIEW SIDE VIEW TOP VIEW ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ

ﺗﻤﺮﻳﻦ ﻣﺤﻠﻮﻝ FRONT VIEW TOP VIEW SIDE VIEW

Orthographic writing Procedure 152 1. Decide the suitable number of views 45 2. Layout the decided views on a drawing sheet. 64 Front 20 Top 152 Choose a drawing scale (say 1: 1) Front y x x z Top y 4. Write dimensions and , if any, notes. y y 3. Draw details of each selected views. x x

Front view selection The longest dimension of an object should be presented as a width (in an front view). First choice Second choice appropriate It requires less space Inappropriate It requires More space

Front view selection 2. The adjacent views projected from the selection elevation view should be appeared in a natural position. Inappropriate

Front view selection 3. It has the fewest number of hidden lines. Good Inappropriate

Selection of other views with the front view 1. Choose the adjacent view that has the fewest number of hidden lines. Inappropriate

ﺍ Selection of other views with the front view 2. Choose the minimum number of views that can represent the major features of the object. NOT GOOD - Hole’s information is placed on a separated view. RIGHT SIDE VIEW FRONT VIEW Necessary . GOOD -All hole’s information is placed on a single view TOP VIEW Necessary

Selection of other views with the front 3. Choose the views that are suitable to a drawing sheet. Poor Not enough space for dimensioning. Choose another adjacent view. Good Change orientation of the selected views. Good

Examples on view selection

Important Notes Generally, three views of orthographic drawing. 1 are enough to describes an object’s information. 2. In some specific cases, a necessary view may be less or more than three views.

Objects require only one view 1. Flat (thin) part having a uniform thickness such as a gasket, sheet metal etc. Example Adjacent views provide only a part’s thickness ! 1 Thick

Objects require only one view Cylindrical-shaped part. Example 1 Example 2 Deduce from center line Repeat !

Objects require two views 1. Identical adjacent view exists. 2. The 3 rd view provides no additional information Example 1 Repeat !

Objects require two views 1. Identical view exists. Example 1

Objects require two views 2. The 3 rd view provides no additional information Example 2

FOR P. V. F OR . V. S FO R E. V. ELEV. VIEW PLANE VIEW SIDE VIEW

FOR P. V. F OR . V. S FO R E. V. ELEV. VIEW PLANE VIEW SIDE VIEW

FOR P. V. F OR S. V. FO R E. V. ELEV. VIEW PLANEVIEW SIDE VIEW

Multiview Projection No line should be drawn where a curved surface is tangent to a plane surface. When a curved surface intersects a plane surface a definite edge is formed. Show are examples of intersections and tangencies.

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