Freehand sketching-Introduction to mechanical engineering

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Freehand Sketching

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  1. 1. Freehand Sketching
  2. 2. Freehand Sketching Ideation Integral to the design process Generation of design concepts to solve a design problem Usually freehand sketching is used to explore, study and communicate these design concepts Even today, and for the foreseeable future, many great design ideas are communicated via freehand sketching The BEST design engineers can immediately communicate an idea via a freehand sketch
  3. 3. Required Pencil, Paper and Eraser Do not use Straight edges, templates, compasses etc. They slow down the process and defeat the purpose of fast communication of ideas!
  4. 4. Sketches are planned Visualize the sketch Size of paper & scale Orientation of the object Minimum detail to communicate the idea Type of sketch Oblique Isometric Orthographic
  5. 5. Types of Sketches Oblique Advantage: one true face Disadvantage: not photorealistic Isometric (a type of axonometric drawing) & Perspective Advantage: easy to visualize the object Disadvantage: no true face
  6. 6. Multi-View (orthographic) Advantage: true faces Disadvantage: hard to visualize Isometric, oblique, and perspective sketches are methods of showing the object in a single view.
  7. 7. Freehand sketches are not sloppy!
  8. 8. When possible use the grid on your engineering paper!
  9. 9. Outline the sketch Use light lines Show major edges and boundaries and then add small details
  10. 10. Shape the sketches Add appropriate details Darken object lines
  11. 11. Fundamental Rule of Sketching Maintain Proportion Hints: use standard techniques to draw lines and arcs Lines Locate a start dot Locate an end dot Put pencil on start dot, look at the end dot and smoothly move pencil toward the end dot
  12. 12. Circles (arcs) Draw light horizontal and vertical lines that intersect at the center Lightly mark the radius on the lines Connect the radius marks with arcs to complete the circle See Step-by-Step 3.1& 3.3 on pages 60 & 62.
  13. 13. Construction Lines Light and thin lines Serve as path for final straight lines Intersection of construction lines specify the length of the final lines Points marked by the intersection of construction lines serve as guides for sketching of arcs and circles Guide the proportion of the sketch
  14. 14. Linetypes
  15. 15. Examples of Good Freehand Sketching Technique
  16. 16. Oblique Sketching Step 1 Draw the horizontal and vertical construction lines which outline the basic shape of the main face - Blocking in Step 2 Sketch the face of the part Step 3 Sketch receding construction lines at 30 or 45 degrees Step 4 Sketch- in and darken the lines outlining the part Done!
  17. 17. Isometric Sketching Step 1 Construct a horizontal line, two lines at 30 degrees above the horizontal and a vertical line through their intersection This defines the isometric axes used to draw the sketch
  18. 18. Isometric Sketching Step 2 Sketch in a box to block-in the front face and the other faces follow Step 3 Sketch the outline of the front face in its block and the other faces follow Work parallel to the isometric axes
  19. 19. References Chapter 3 of Modern Graphics Communication by Giesecke, Mitchell, Spencer, Hill, Dygdon, Novak, and Lockhart, 3rd edition. Prentice- Hall, 2004. Technical Drawing by Giesecke, Mitchell, Spencer, Hill, Dygdon, and Novak, 9th edition. Macmillan, 1991.