2 Objectives Fundamentals Views of Edges & Planes Quick review and comments on creation of proper multiview drawingsQuick review standard line practices used in multiview drawingsFundamentals Views of Edges & PlanesIdentify normal, inclined, and oblique planes in multiview drawingsANSI Standards for Partial & Revolved Views
3 Introduction to Projections In design, drawings are (ideation, documentation) used to represent 3-D objects in a number of different waysRepresentation of objects largely done on 2-D media (paper, or computer screens)Drawings are still the primary tool for representing 3-D objects even though modern techniques such as holograms & Virtual Reality devices attempt to communicate in 3-DMost projection methods were developed to address the problem of trying to represent 3-D images on 2-D media
5 Common Projection Techniques MultiviewAxonometric (isometric)ObliquePerspective
6 Drawing Classifications Pictorial vs. MultiviewObject presented in a single pictorial view with all three dimensions representedObject presented in a series of projections, each showing only two of the object’s three dimensionsParallel vs. PerspectiveParallel: preserves true relationships of object’s features and edgesPerspective: distorts object so it matches more closely how we perceive it visuallyAdvantages / Disadvantages (pictorials)More realisticEasier to drawEasier to interpret by non-technical people
7 Projection Methods & their Attributes: Perspective versus Parallel
14 Axonometric Projection Parallel projection technique used to create pictorial drawings(observer theoretically at infinite distance from projection plane)Created by rotating object on an axis relative to a picture or projection planeLines-of-sight are perpendicular to plane of projectionClassified by angles between lines comprising the axonometric axes (axes that meet to form the corner of the object that is nearest the observer)Trimetric projection: all 3 angles unequalDimetric projection: two of the 3 angles are equalIsometric projection: all 3 angles are equal
16 Multiview Projections (based on // projection techniques) Used to represent features of an object more accurately than is possible with a single pictorial viewCollection of flat 2-D drawings that work together to give an accurate representation of the overall objectEach view concentrates on only 2-dimensions of object (minimum distortion)Sufficient no. of views generated to capture all important featuresViews must be coordinated with one another to represent object properly.
28 Multiview Drawing of Object (Conventional View Placement)Central view
29 Multiview Drawing of Object (Alternate View Arrangement)
30 Three Space Dimensions: Width, Height, Depth - Require Multiple Views (at least 2 views) -Rule 1Alignment of Features: Every point or feature in one view must be aligned on a parallel projector in any adjacent viewRule 2Distances in Related Views: Distances between any two points of a feature in related views must be equal
56 Various Applications of Center Lines (Conventions)
57 Fundamental Views of Edges and Planes Know when the edges or planes are in true size, not foreshortened. Distances, angles, and areas can then be measured.
58 Fundamental Views of Edges Edge line: intersection of two planes & is represented as a line on multiview drawingsRule 3True Length & Size: Features are true length or true size when the lines of sight are perpendicular to the featureEdge line appears as a point in a plane of projection to which it is perpendicularEdge lineAppears as a pointEdge lines
59 Fundamental Views of Edges Inclined line: is parallel to a plane of projection but inclined to the adjacent planes (4 black lines)Oblique line: is not parallel to any principal plane of projection. It never appears as a point or in true length in any of the six principal views (line 1 – 2)
60 Fundamental Views of Surfaces Surface A: principal plane // to frontal planeSurface B: principal plane // to horizontal planeSurface C: principal plane // to profile planeSurface D: inclined plane (edge view in front view)Surface E: oblique plane (not parallel nor on edge in any principal planes)Rule 4Foreshortening: Features are foreshortened when the lines of sight are not perpendicular to the feature
61 Rule of Configuration of Planes Configuration of Planes: Areas that are the same feature will always be similar in configuration from one view to the next, unless viewed on edgeRule 6Parallel Features: Parallel features will always appear parallel in all viewsRule 7Edge Views: Surfaces that are parallel to the lines of sight will appear as lines or edge views
62 Analysis by Surfaces (of Multiview Drawings) Technique used to visualize 3-D objects from multiview drawingsRule 5Configuration of Planes: Areas that are the same feature will always be similar in configuration from one view to the next, unless viewed on edgeRule 6Parallel Features: Parallel features will always appear parallel in all viewsRule 7Edge Views: Surfaces that are parallel to the lines of sight will appear as lines or edge views
63 Analysis by Surfaces (of Multiview Drawings) Technique used to visualize 3-D objects from multiview drawingsRule 8Contiguous Areas: No two contiguous areas can lie in the same plane(If they were in the same plane a line would not be drawn to separate them)
64 Analysis by Surfaces (of Multiview Drawings) Technique used to visualize 3-D objects from multiview drawingsRule 8Contiguous Areas: No two contiguous areas can lie in the same plane(If they were in the same plane a line would not be drawn to separate them)
65 Angles in Multiview Drawings (C) A 90-degree angle can be measured in a foreshortened surface if one edge is true length. (A) Angles other than 90 degrees can only be measured in views where the surface that contains the angle is perpendicular to the line of sight. (B) Not true angle shown in drawing
66 Representing Limiting Elements The sides of the triangle represent limiting elements of the cone.The vertical sides of the rectangle represent the limiting elements of the sides of the cylinder.
67 Tangent & Non-tangent Partial Cylinder Note: When the transition of a rounded end to another feature is not tangent, a line is used at the intersection of the two features
68 Elliptical Representation of a Circle An elliptical view of a circle is created when the circle is viewed at an oblique angle
69 Viewing Angles for Ellipses Note: The size (or exposure) of an ellipse is determined by the angle of the line of sight relative to the circle
71 Representation of Types of Machined Holes See textbook (Ch. 10) for technical drawing representations of fillets, rounds, finished surfaces, chamfers, intersecting cylinders with prisms and other features.
72 ANSI Standards for Multiview Drawings Partial Views and Revolution Conventions
73 Partial View for A Symmetrical Object (also for some types of auxiliary views & for saving time)
74 Use of Partial Views to Eliminate Hidden Lines Improves clarityFront View
75 Revolution Conventions for Ribs and Webs Violates true projection of views
76 Revolution Conventions for Objects with Bolt Circles Violates true projection of views
77 Revolution Convention for Representation of Arms Violates true projection of views