first-year engineering program engineering h191 engineering fundamentals and laboratory i projection...
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First-Year Engineering Program
Engineering H191Engineering Fundamentals and Laboratory I
Projection Systems: Orthographic and Isometric
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First-Year Engineering Program
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Objectives
• Orthographic Projections• View Selection• Glass Box Approach• First and Third Angle Projections• Line Precedence• Two View Drawings• Tips
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First-Year Engineering Program
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Orthographic Projections
• Reference: Technical Graphics• Advantage – Represent features of an object
more accurately• Example Problem
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First-Year Engineering Program
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Orthographic Projections
• Orthographic Projections are a collection of 2-D drawings that work together to give an accurate overall representation of an object.
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Defining the Six Principal Views or
Orthographic Views
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Which Views to Present?
General Guidelines
• Pick a Front View that is most descriptive of object
• Normally the longest dimension is chosen as the width (or depth)
• Most common combination of views is to use:
– Front, Top, and Side View
• Any other view different from the Principal Views is called an Auxiliary View (see Technical Graphics text)
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First-Year Engineering Program
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Glass Box Approach
• Most powerful technique to understand orthographic projections
• Suspend the object with transparent strings inside a glass box
• Freeze the view from each direction (each of the six sides of the box) and unfold the box
• Animation illustrates glass-box approach
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Glass Box Approach
• Available on the FEH website:
• http://feh.eng.ohio-state.edu– Lecture Notes– Engineering H191 – Autumn 2005– Glass Box Animation
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AU 2005
Glass Box Approach
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AU 2005
Glass Box Approach
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First-Year Engineering Program
AU 2005
Glass Box Approach
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First-Year Engineering Program
AU 2005
Glass Box Approach
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First-Year Engineering Program
AU 2005
Glass Box Approach
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AU 2005
Glass Box Approach
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Third-angle Projection
First-angle Projection
First and Third Angle Projections
• First Angle – International• Third Angle – U.S.
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Conventional Orthographic Views
Height
Depth
Width
Front View
Top View
Right Side View
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Is The Orthographic View OK?
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Orthographic Must Be In Projection
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Hidden and Center Lines
• Hidden Line – used to represent features that cannot be seen in the current view
• Centerlines – used to represent symmetry and to mark the center of circles and the axes of cylinders, and the axes of symmetrical parts, such as cylinders and bolts
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For Example:
1. Visible
2. Hidden3. Center
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• Visible lines takes precedence over all other lines
• Hidden lines and cutting plane lines take precedence over center lines
• Center lines have lowest precedence
Precedence of Lines
0.6 mm
0.3 mm
0.6 mm
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Example: Application of Precedence
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Intersecting Lines in Orthographic Projections
Solid Line Intersections
Dashed Line Intersections
Gap
Reference – Technical Graphics, Chapter 3
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Two-View Drawings
• Some objects can be fully described by two views, look for:
– Symmetry or Bodies of Rotation
Front View Right Side View
Front View
Right Side
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Other Two-View Examples
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Summary
• Introduced to orthographic projections
• We recommend the software animation exercise introduced in class. Animation can be found on Carmen – Glass Box Theory.
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Review Questions
• Rectilinear grids are used for sketching isometric pictorials … True/False
• Based on the lines of sight, orthographic projection drawings are classified as ___________ projections
• There are ____ standard principal views of orthographic projections
• Each view in an orthographic projection concentrates on ____ dimensions of the object
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Hints for Orthographic Projection Sketching
• Identify the major features and overall dimensions of the object
• Do not use any straight-edge devices as a pencil guide when sketching by hand
• Start by drawing bounding boxes with light construction lines.
• Keep views aligned while sketching
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Hints for Orthographic Projection Sketching
• Title Information is required – follow conventions
• Usage of construction lines is encouraged.
– Mandatory for circle or ellipse
• Orthographic projection:
– Alignment of the views is important!
– Will not be graded, if not aligned
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Hints for Orthographic Projection Sketching
• Map inclined and oblique faces to all three views
• Follow the precedence of lines
• Darken all visible, hidden, and center lines
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Sketching a Circle
• Draw a square whose sides are the diameter of the circle.
• At the center of each side define the point of tangency for the circle.
• Draw the diagonals of the square.
• Orient the paper so you can draw equal arcs to construct the circle
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Today's Assignment
• A11• TG 2.7 and 2.18