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    Multiview Sketches

    Engineering Graphics

    Stephen W. Crown Ph.D.

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    Objective

    How to use sketching as an effective

    tool in the engineering design process

    How to represent a 3-D objecteffectively on a 2-D drawing surface

    (multiview sketching)

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    Overview

    Sketching Definition

    Tools / Instruments

    Mechanics of sketching Lines and Curves

    A Bounding Box

    Multiview sketches How to create them

    When to use them

    Why use sketches? Creativity

    Communication

    Documentation

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    Sketching

    Definition: A rough freehand drawing

    used to document, communicate, and

    refine ideas developed in the ideation

    phase of the design process

    Beginners will benefit from instruments

    Follows standard practices

    A developed skill

    Should be the first step of

    any CAD drawing

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    Tools

    Pencils Use a mechanical pencil (0.5mm lead)

    Practice using different pressure to produce

    desired linetypes (construction lines)

    Paper Unlined paper is the most useful

    Square grid and tracing paper is often useful

    Eraser A good eraser is worth the investment

    Do not overuse your eraser (save some mistakes)

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    Using Simple Instruments

    The use of mechanical instruments is

    recommended only for beginners. Break away

    from reliance on tools that slow you down.

    Helpful tools for beginners Compass

    Triangles

    Dividers

    Ruler

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    Drawing straight lines

    Mark starting and ending point

    Break long lines into short line

    segments by marking the midpoint

    Start with a light pass if necessaryand then darken

    Use a loose comfortable grip

    Reorient the paper to your

    convenience test your skill with different orientations

    an awkward orientation may

    occasionally produce positive results

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    Drawing curved lines

    Break large arcs/circles into

    small segments

    Make guide marks for eachsegment

    Circles and Ellipses

    Sketch a light square/rectangle

    Lightly sketch in diagonals

    Mark contact points on

    square/rectangle

    Rotate the paper for each

    segment

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    Bounding Box and Construction Lines

    Plan

    choose proper scale and

    orientation

    dont crowd sketches Start with a bounding box

    Use light straight

    construction lines

    Draw boundary lines of

    internal features starting

    with the largest features

    Sketch dark object lines

    using light boundary lines

    as a guide

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    Multiview Sketching

    Represents a 3-D object

    with a series of 2-D

    views in contrast to

    pictorials which showall three dimensions in a

    single view

    Also called orthographic

    projection

    Best understood by

    engineers or technically

    trained people

    Multiview Drawing

    Pictorial

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    Parallel projection

    Preserves true relationship

    between features

    The geometry is generally not distorted

    Lines that are parallel on the object are

    parallel on the drawing

    Parallel projectors

    The object is projected onto a

    projection plane as a shadow is

    projected where the rays form the lightsource are parallel.

    Projection from one view to another is

    accomplished with parallel projection

    lines

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    Parallel versus Perspective Projection

    Parallel

    Perspective

    Parallel

    Perspective

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    Projection Planes versus Views

    Projection planes:

    Object formed from projection lines projected

    perpendicularly onto a projection plane

    Planes: Horizontal, frontal, and profile Each projection plane is perpendicular to adjacent

    projection planes

    Principle views

    The object is rotated 90 degrees about the horizontalor vertical axis to give six principle views (top,

    bottom, front, rear, left, and right side)

    Common views: top, front, and right side

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    Only use Necessary Views

    One view drawings

    Stamped, thin or extruded parts

    Specify thickness with a note

    Two view drawings

    Cylindrical parts

    Show the circular and

    rectangular view Three view drawings

    Usually sufficient for all other

    drawings

    Top, front, and right side view

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    Orientation and Placement of Views

    The most descriptive view

    should be selected as the

    front view

    The natural orientation of

    the part should be

    preserved if possible

    Views must be aligned Top view above front view

    Right view to the right of

    front view

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    Hidden lines

    Represented with

    dashed lines

    Precedence of lines

    (visible, hidden, center)

    Views should be

    selected to minimize

    the use of hidden linesmost descriptive view

    should be selected as

    the front view

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    Third Angle Projection Associated with English

    units

    First Angle Projection Associated with SI units

    First Versus Third Angle Projection

    ANSI Symbol

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    Fold Lines

    Represents a 90 degree fold between views

    Generally not shown on engineering

    drawings except when views other than the

    principle views (auxiliary views) are used.

    Labeled as: H/F, F/P, F/1, 1/2

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    Terminology to Relate Views

    Adjacent view

    A view that is separated by a fold line

    The top view is an adjacent view to the front view

    Central View A view that is between two adjacent views

    The front view is the central view of the top, front,

    and right side view

    Related views

    Two views that are adjacent to a central view

    The top and right side view are related views

    since they are both adjacent to the front view

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    Constructing a New View

    The top and front viewsof a surface are shown

    The fold linerepresentsa 90 degree foldbetween the views

    Parallelprojection lines

    are perpendicular to thefold line

    1

    2

    3

    3

    2

    1

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    Constructing a New View

    A vertical fold lineis drawn at an

    arbitrary distance from the front view

    Parallelprojection linesare drawn

    from each vertex The common depth between the top

    and side view is used to locate each

    vertex on the projection lines

    1

    2

    3

    3

    2

    11

    2

    3

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    Sketching as Part of the Creative

    Design Process

    Quickly translate

    thoughts to paper

    An effective means

    of communication

    Stimulates creativity

    and visualization

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    Sketching Allows for the Quick

    Translation of Thoughts to Paper

    Commit thoughts to paper before you

    lose an idea

    Avoid the of use mechanical tools (drawing

    tools are helpful for beginners)

    Does not need to be an exact representation

    objects may be simplified

    parts may be missing

    Avoid erasing

    as new ideas are developed make new sketches

    start with light lines and then darken with darker

    lead or heavier strokes

    Sk hi i A Eff i M

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    Sketching is An Effective Means

    of Communication

    Understand your audience

    Who is looking at the sketches?

    What details are they interested in?

    What type of sketch will they best understand?

    Follow standard practices

    You may not always accompany your sketches

    Others may misinterpret your drawing Sketches provide a log of ideas that were

    considered in a brainstorming session

    Sk hi S i l C i i

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    Sketching Stimulates Creativity

    and Helps Visualization

    The process of sketching ideas that are partially

    developed often aids the design process

    do not wait until you have a clear picture before you

    start sketching allow yourself the freedom to make mistakes

    Visualization of the entire design is essential but

    often impossible without aid of sketches

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    Appendix

    Engineering Graphics

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    Make a Quick Sketch

    How many of the nine views consisted of asquare bounding box?

    How many of the nine views are the same?

    How many of the nine views consisted of onlyvertical or horizontal lines?

    What is the volume of each object (Cube=8 in3)?

    You will have ten seconds to make a

    sketch of each object shown below

    before being asked a few questions

    about the objects.