FREEHAND SKETCHING-I FREEHAND SKETCHING-I

FREEHAND SKETCHING-I FREEHAND SKETCHING-

1. FREEHAND SKETCHING-I

2. Communicating Technical Designs Sketching and Shape Description Straight Lines Circles and Arcs Proportions Generating Technical Designs

3. Purpose The main purpose of sketching is to convey ideas. Engineers have to use sketches to brainstorm ideas, as well as, to show others what they are working on or what should be designed. Sketches are also used to document measurements from the field before they are produced as solid models on the computer.

4. Freehand Sketching Most original designs are first expressed on medium as a freehand sketch. Used for: Amplifying and clarifying Recording verbal explanations

5. Technical Sketching Engineers’ view: ability to render serviceable sketches greater value than skill to create instrument drawings. Freehand sketch should not mean crude and sloppy. Freehand sketch should be made with care and attention to proportion, clarity, and line widths.

6. Types of Sketches

7. Scale Typically not made to any scale. Correct proportions are needed. Size of sketch: Optional Determined by: Complexity of object Size of paper Small objects may be enlarged to show details clearly.

8. Purpose Proper documentation in a notebook is essential. When proper documentation is made, ideas are not lost and projects can be duplicated. The sketch on the next slide is a sample from a notebook where a sketch was made and notes as well as dimensions have been documented.

9. Proposed Notebook Sample Shows design details Size requirements. Initialed and dated. Title

10. Freehand Sketching Freehand sketching is a method of making a drawing without the use of instruments. Most designers use sketches to “think through” an idea before making the final drawing. Freehand sketching requires only a pencil and plain or grid paper.

11. Freehand Sketching Cross-section paper may be used for freehand sketching.

12. Sketching Technique When sketching, hold the pencil with a grip firm enough to control the strokes. Your arm and hand should have a free and easy movement. As you sketch, rotate the pencil slightly between the strokes to retain the point longer. Initial lines should be sharp and light.

13. Sketching Technique Apply light pressure to avoid making grooves in the paper. Keep your eye on the point where the line will end; use a series of short strokes to reach that point. When all the lines are sketched, go back and darken the lines. Strive for neatness and good technique.

14. Sketching Technique When sketching, grip your the pencil farther back than you normally would.

15. Sketching Horizontal Lines There are four basic steps.

16. Sketching Vertical Lines There are four basic steps. 16

17. Sketching Inclined Lines Locate the end points of the line. Position arm for trial movement. Sketch several short, light lines. Focus on end point. Darken the line.

18. Sketching an Angle First, sketch a right angle (90°). Subdivide the right angle to get the angle you desire.

19. Sketching Techniques Line Types: Vertical Line Horizontal Line Inclined Line

20. Sketching Techniques Finding the slope angle of an inclined line: Run = 4 Rise = 2 Note: Rise and Run units do not matter (As long as the units are the same). You are finding an angle. In the above case, we are counting grid boxes. Equation: tan s = RISE/RUN tan s = 2/4 tan s = .5 s = arctan .5

21. Sketching Techniques Sketching a Line.

22. Sketching Techniques Sketching an Arc

23. Sketching Techniques Sketching a Circle 1) Setup the diameter 2) Square in the diameter 3) Sketch diagonals

24. Sketching Circles and Arcs There are several methods of sketching circles and arcs: Centerline method. Enclosing square method. Hand-pivot method. Free-circle method. All are sufficiently accurate, so use the best method for a particular situation.

25. Centerline Method Locate centerlines. Mark off radius. Position arm. Sketch the circle in short sweeps. Darken the circle.

26. Enclosing Square Method Locate centerlines. Sketch a box equal to the diameter. Sketch arcs where the centerlines cross the box line. Sketch the circle.

27. Sketching Techniques Sketching an Arc

28. Sketching Techniques Sketching a Circle 4) Identify triangle centers 5) Sketch arcs

29. Hand-Pivot Method First, position the pencil and small finger. Then, rotate the paper to sketch the circle.

30. Sketching Ellipses The rectangular method for sketching ellipses is similar to the enclosing square method for circles.

31. Sketching Irregular Curves Sketch an irregular curve by connecting a series of points at intervals of 1/4" to 1/2" along its path.

32. Proportion in Sketching Proportion is the size relationship of one part to another or to the whole object. Keep the same width, height, and depth in proportion. Unit method. Pencil-sight method.

33. Proportion in Sketching Gauge proportions using the pencil-sight method.

34. Size and Proportion Although you have learned to draw lines and arcs, you can not communicate properly until you understand how to sketch with the correct size and proportion . Without proper size and proportion your sketch will not look right. Size: Length, width, height, distance. How big is the object you are sketching? Proportion: If two objects are five feet apart in real life, then those two objects must appear to be five feet apart in your sketch.

35. Size and Proportion How to create proper size and proportion. Technique I Using a pencil to measure. Figure 2 Hold your pencil at arms length as you see in Figure 2. Use the top of the pencil and your thumb as a distance for the height of the window. This distance will be used as a reference for sketching the rest of the house as we did in the house on the next slide.

36. Size and Proportion How to create proper size and proportion. Technique I Using a pencil to measure. Figure 3 As you see in the completed house in Figure 3, the units of the numbered dimensions are in windows. You should also notice that the use of graph paper also helps in creating proper size and proportion.

37. Size and Proportion How to create proper size and proportion. Technique II Boxing in the sketch. In Figure 4 we are sketching a chair. We sketch the boxes to the largest outside dimensions of our final object. Notice that light construction lines are also used to help guide us to the proper size and proportion. Figure 4

38. Size and Proportion How to create proper size and proportion. Technique II Boxing in the sketch. Finally we use our sketching techniques for drawing arcs, lines and circles to complete our chair in Figure 5. Notice the box we started with is still existent as light construction lines. These are our guides for proportion and size. Figure 5

39. Alphabet of Lines

40. Border Lines Border lines are very heavy lines used to form a boundary for the drawing .

41. Object Lines Object lines are heavy lines that outline features of an object .

42. Hidden Lines Hidden lines represent edges that are behind a visible surface in a given view .

43. Centerlines Centerlines indicate the center of holes and symmetrical objects, such as windows and doors .

44. Extension Lines Extension lines are used to denote the termination points of a dimension line . Extension lines

45. Dimension Lines Dimension lines are used to show size and location. They have a dimension figure halfway between the ends of the dimension line .

46. Long Break Lines Long break lines are used to show that not all of the part is shown .

47. Short Break Lines Short break lines show part of the object broken away .

48. Cutting-Plane Lines Cutting-plane lines are used to show where the object is sectioned .

49. Section (Crosshatch) Lines Section lines or crosshatch lines are used to show that a feature is sectioned. May represent different types of material .

50. Alphabet of Lines Object Line: Thick lines about .6mm(.032in) that show the visible edges of an object . Hidden Line: Lines used to show interior detail that is not visible from the outside of the part. Center Line: Lines that define the center of arcs, circles, or symmetrical parts. They are half as thick as an object line . Construction Line: Very lightly drawn lines used as guides to help draw all other lines and shapes properly. Usually erased after being used . Short Break Line: A freehand drawn line that shows where a part is broken to reveal detail behind the part or to shorten a long continuous part. (See example of Long Break Line on the next slide.) Section Lines: Lines are used to define where there is material after a part of the object is cut away.

51. discussions