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Engineering H191 Engineering Fundamentals and Laboratory I

Engineering H191 Engineering Fundamentals and Laboratory I. Projection Systems: Orthographic and Isometric. Objectives. Orthographic Projections View Selection Glass Box Approach First and Third Angle Projections Line Precedence Two View Drawings Tips. Orthographic Projections.

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Engineering H191 Engineering Fundamentals and Laboratory I

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  1. Engineering H191Engineering Fundamentals and Laboratory I Projection Systems: Orthographic and Isometric

  2. Objectives • Orthographic Projections • View Selection • Glass Box Approach • First and Third Angle Projections • Line Precedence • Two View Drawings • Tips AU 2005

  3. Orthographic Projections • Reference: Technical Graphics • Advantage – Represent features of an object more accurately • Example Problem AU 2005

  4. Orthographic Projections • Orthographic Projections are a collection of 2-D drawings that work together to give an accurate overall representation of an object. AU 2005

  5. Defining the Six Principal Views or Orthographic Views AU 2005

  6. 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) AU 2005

  7. AU 2005

  8. 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 AU 2005

  9. Glass Box Approach • Available on the FEH website: • http://feh.eng.ohio-state.edu • Lecture Notes • Engineering H191 – Autumn 2005 • Glass Box Animation AU 2005

  10. Glass Box Approach AU 2005

  11. Glass Box Approach AU 2005

  12. Glass Box Approach AU 2005

  13. Glass Box Approach AU 2005

  14. Glass Box Approach AU 2005

  15. Glass Box Approach AU 2005

  16. Third-angle Projection First-angle Projection First and Third Angle Projections • First Angle – International • Third Angle – U.S. AU 2005

  17. Width Top View Depth Right Side View Front View Height Conventional Orthographic Views AU 2005

  18. Is The Orthographic View OK? AU 2005

  19. Orthographic Must Be In Projection AU 2005

  20. 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 Hidden and Center Lines AU 2005

  21. For Example: 1. Visible 2. Hidden 3. Center AU 2005

  22. 0.6 mm 0.3 mm 0.6 mm Precedence of Lines • Visible lines takes precedence over all other lines • Hidden lines and cutting plane lines take precedence over center lines • Center lines have lowest precedence AU 2005

  23. Example: Application of Precedence AU 2005

  24. Gap Intersecting Lines in Orthographic Projections Solid Line Intersections Dashed Line Intersections Reference – Technical Graphics, Chapter 3 AU 2005

  25. Two-View Drawings • Some objects can be fully described by two views, look for: • Symmetry or Bodies of Rotation Front View Right Side View Right Side Front View AU 2005

  26. Other Two-View Examples AU 2005

  27. Summary • Introduced to orthographic projections • We recommend the software animation exercise introduced in class. Animation can be found on Carmen – Glass Box Theory. AU 2005

  28. 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 AU 2005

  29. 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 AU 2005

  30. 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 AU 2005

  31. 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 AU 2005

  32. 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 AU 2005

  33. Today's Assignment • A11 • TG 2.7 and 2.18 AU 2005

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