1. Chapter 2
Sketching

2. Objectives
Explain the importance of sketching in the engineering design process
Make simple sketches of basic shapes such as lines, circles, and ellipses
Use 3-D coordinate systems, particularly right-handed systems
Draw simple isometric sketches from coded plans

3. Objectives (cont’d.) Make simple oblique pictorial sketches
Use advanced sketching skills for complex objects

4. Introduction Sketching
One of the primary modes of communication in initial stages of design process
Means to creative thinking

5. Introduction (cont’d.)
Sketching techniques
Portraying 3-D coordinate systems on 2-D paper
Shading
Cartooning

6. Sketching in the Engineering Design Process
Sketch: any drawing made without using drawing instruments (such as triangles)
All you need for sketching
Pencil, paper, eraser, imagination
Initial sketches based on rough ideas
Refine sketches as you refine your ideas

7. Sketching Lines
FIGURE Techniques for sketching straight lines.

8. Sketching Lines (cont’d.)
FIGURE Techniques for sketching straight lines. (cont’d.)

9. Sketching Lines (cont’d.)
FIGURE Rotating the
paper to draw an angled line.
FIGURE Sketching long
lines in segments.

10. Sketching Curved Entities
FIGURE Sketching a circle using a bounding box.

11. Sketching Curved Entities (cont’d.)
FIGURE Using intermediate radial tick marks for large circles.
FIGURE Using boundary boxes to sketch arcs and ellipses.

12. Construction Lines FIGURE 2.09. The front view of an object to sketch.
FIGURE Construction lines
used to create a sketch.
FIGURE Completed sketch
using construction lines as a guide.

13. Construction Lines (cont’d.)
FIGURE Using diagonal construction lines to locate centers.

14. Coordinate Systems
FIGURE The x-, y-, and z- coordinate axes.

15. Coordinate Systems (cont’d.)
FIGURE An alternative method to check for a right-handed coordinate system.
FIGURE Left-handed coordinate systems.

16. Coordinate Systems (cont’d.)
FIGURE Isometric grid and dot paper.
FIGURE An isometric representation of a right-handed coordinate system.

17. Isometric Sketches of Simple Objects
More than one orientation exists from which a block can be sketched
Choose orientation based on needs or preferences
Lines shown in sketch only where surfaces intersect
Hidden edges not shown in sketch

18. Isometric Sketches of Simple Objects (cont’d.)
FIGURE Four coded plans and the resulting isometric sketches.

19. Circles in Isometric Sketches
FIGURE A cube with the circle center and bounding box on the side.
FIGURE Sketching an ellipse on the top surface of a cube.

20. Circular Holes in Isometric Sketches
FIGURE Blocks with circular holes in them.
FIGURE Determining visibility of back circles.

21. Oblique Pictorials Height and width of object shown in plane of paper
Depth recedes off at an angle
Advantage over isometric pictorials
When face of object shown in plane of paper, it will be undistorted
Length of receding dimension not too important

22. Oblique Pictorials (cont’d.)
FIGURE A comparison of isometric and oblique pictorials.

23. Circular Holes in Oblique Pictorial Sketches
FIGURE Oblique pictorials with circular holes in objects.
FIGURE Determining visible
back arcs in a hole.

24. Shading and Other Special Effects
Shading makes surfaces stand out or shows curvature
FIGURE A simple object with two possible types of progressive shading used to
emphasize the curvature of surfaces.

25. Shading and Other Special Effects (cont’d.)
FIGURE The addition of
surface treatments to convey
smooth surfaces (a) and rough
surfaces (b).
FIGURE Action
lines used to convey the
motion of linkages.

26. Sketching Complex Objects
FIGURE A sketch of a cell telephone.
FIGURE A sketch of a set of headphones.
FIGURE A sketch of a camera.

27. Sketching Complex Objects (cont’d.)
FIGURE A sketch of a computer monitor using the method of “foundation (a), frame (b), finish (c).”

28. Strategies for Simple Pictorial Sketches
Simple isometric sketches
Object grows up from the base
Start sketch by drawing the visible V
FIGURE A completed isometric sketch.

29. Oblique Sketches
Begin by determining which surface is closest to viewer
Sketch closest surface in true shape and size
Decide whether receding dimension should be to left or right

30. Oblique Sketches (cont’d.)
FIGURE An isometric pictorial of an object and a viewing direction for an oblique sketch.

31. Oblique Sketches (cont’d.)
FIGURE Surface A with
receding dimensions sketched.
FIGURE Surface B included in pictorial.
FIGURE A completed oblique
pictorial sketch.

32. Summary
Learned about importance of sketching and the link between creativity and freehand sketching
Developed techniques for sketching basic shapes such as lines, arcs, circles, and ellipses

33. Summary (cont’d.)
Learned about the right-hand rule and the way it is used to define 3-D coordinate systems in space
Discovered how to make basic isometric sketches of objects from coded plans and rules that govern these sketches
Developed techniques for creating oblique pictorials