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MECH 100 – Graphics I Technical Graphics Communication: Multiview Drawings (Part 2)

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Objectives Quick review and comments on creation of proper multiview drawings Quick review standard line practices used in multiview drawings Fundamentals Views of Edges & Planes Identify normal, inclined, and oblique planes in multiview drawings ANSI Standards for Partial & Revolved Views

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Introduction to Projections In design, drawings are (ideation, documentation) used to represent 3-D objects in a number of different ways Representation 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-D Most projection methods were developed to address the problem of trying to represent 3-D images on 2-D media

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Representing a 3-D Object on 2-D Medium

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Common Projection Techniques Multiview Axonometric (isometric) Oblique Perspective

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Drawing Classifications Pictorial vs. Multiview Object presented in a single pictorial view with all three dimensions represented Object presented in a series of projections, each showing only two of the objects three dimensions Parallel vs. Perspective Parallel: preserves true relationships of objects features and edges Perspective: distorts object so it matches more closely how we perceive it visually Advantages / Disadvantages (pictorials) More realistic Easier to draw Easier to interpret by non-technical people

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Projection Methods & their Attributes: Perspective versus Parallel

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Perspective Projection

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Parallel Projection

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Pictorial drawings Perspective (distorts object to match more closely how we perceive it visually) Isometric (preserves true relationships of objects features & edges)

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Perspective: Distort object to more closely match how we perceive visually

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Perspective Projection: Distorted Dimensions

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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 plane Lines-of-sight are perpendicular to plane of projection Classified 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 unequal Dimetric projection: two of the 3 angles are equal Isometric projection: all 3 angles are equal

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Various Parallel Projections

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Multiview Projections (based on // projection techniques) Used to represent features of an object more accurately than is possible with a single pictorial view Collection of flat 2-D drawings that work together to give an accurate representation of the overall object Each view concentrates on only 2-dimensions of object (minimum distortion) Sufficient no. of views generated to capture all important features Views must be coordinated with one another to represent object properly.

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Multiview Orthographic Projection

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Orthographic Projection: FRONT View

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Orthographic Projection Drawing: FRONT View

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Orthographic Projection: TOP View

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Orthographic Projection: Profile View (RIGHT Side View)

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Multiview Drawing of Object: FRONT, TOP, ISOMETRIC

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Multiview Drawings: The Six Principal Views & Angle of Projection

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Multiview Orthographic Projection

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Imagine Object Suspended in Glass Box Projections Produce Six Principal Views

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Unfolding Glass Box to Produce the Six Principal Views of the Drawing

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Multiview Drawing of Object

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(Conventional View Placement) Central view

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Multiview Drawing of Object (Alternate View Arrangement)

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Three Space Dimensions: Width, Height, Depth - Require Multiple Views (at least 2 views) - Rule 1 Alignment of Features: Every point or feature in one view must be aligned on a parallel projector in any adjacent view Rule 2 Distances in Related Views: Distances between any two points of a feature in related views must be equal

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Three-View Multiview Layout on A-size Sheet

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Transferring Depth Dimensions: - Between TOP & RIGHT views -

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Parts Requiring Two-View Drawings

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Parts Requiring One-View Drawings

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Layout of CAD Model on a Drawing Sheet

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Good versus Poor Orientation

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Place Object in Natural Position

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Use Minimum Number of Views

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Use the Most Descriptive Views

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First- & Third-Angle of Projection Drawings: The Different Six Principal Views

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Principal Projection Planes and Quadrants: Used to Create First- and Third- Angle Projections

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Pictorial Comparison: First-AngleandThird-AngleProjections

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Standard View Arrangements: Third-Angle (U.S.) and and (ISO) First-Angle Projections Third- Angle First- Angle

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View Arrangement: First-Angle Projection

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Alphabet of Lines: ASME standard line types for technical drawings

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Alphabet of Lines: Hand Sketched

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Engineering Sketch Showing Several Line Types Used

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Various Line Types used in a Technical Drawing ASME standard line types for technical drawings (dimensions shown for traditional drawing tools)

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Drawing Conventions for Hidden Lines

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Precedence of Lines (Review)

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Engineering Drawing: Showing Application of Precedence of Lines

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Application of Center Lines (for a Cylinder)

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Various Applications of Center Lines (Conventions)

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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.

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Fundamental Views of Edges Edge line: intersection of two planes & is represented as a line on multiview drawings Rule 3 True Length & Size: Features are true length or true size when the lines of sight are perpendicular to the feature Edge line appears as a point in a plane of projection to which it is perpendicular Appears as a point Edge line Edge lines

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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)

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Fundamental Views of Surfaces Surface A: principal plane // to frontal plane Surface B: principal plane // to horizontal plane Surface C: principal plane // to profile plane Surface D: inclined plane (edge view in front view) Surface E: oblique plane (not parallel nor on edge in any principal planes) Rule 4 Foreshortening: Features are foreshortened when the lines of sight are not perpendicular to the feature

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Rule of Configuration of Planes Rule 5 Configuration of Planes: Areas that are the same feature will always be similar in configuration from one view to the next, unless viewed on edge Rule 6 Parallel Features: Parallel features will always appear parallel in all views Rule 7 Edge Views: Surfaces that are parallel to the lines of sight will appear as lines or edge views

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Analysis by Surfaces (of Multiview Drawings) Rule 6 Parallel Features: Parallel features will always appear parallel in all views Rule 7 Edge Views: Surfaces that are parallel to the lines of sight will appear as lines or edge views Technique used to visualize 3-D objects from multiview drawings Rule 5 Configuration of Planes: Areas that are the same feature will always be similar in configuration from one view to the next, unless viewed on edge

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Rule 8 Contiguous 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) Analysis by Surfaces (of Multiview Drawings) Technique used to visualize 3-D objects from multiview drawings

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Rule 8 Contiguous 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) Analysis by Surfaces (of Multiview Drawings) Technique used to visualize 3-D objects from multiview drawings

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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

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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.

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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

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Elliptical Representation of a Circle An elliptical view of a circle is created when the circle is viewed at an oblique angle

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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

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Multiview Drawings of Solid Primitive Shapes

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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.

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ANSI Standards for Multiview Drawings Partial Views and Revolution Conventions

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Partial View for A Symmetrical Object (also for some types of auxiliary views & for saving time)

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Use of Partial Views to Eliminate Hidden Lines Improves clarity Front View

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Revolution Conventions for Ribs and Webs Violates true projection of views

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Revolution Conventions for Objects with Bolt Circles Violates true projection of views

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Revolution Convention for Representation of Arms Violates true projection of views

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Assignment Review: Chapter 10 – Multiview Drawings Study: Chapter 17 – Dimensioning Practices Answer Review Questions on Bb Learn (Chapter 10 – Part 2)

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