Autocad Slides

1. BTM1614 Computer Aided Drafting
Chapter 1: Introduction to Engineering Drawing
Chapter 2: Basic Knowledge for Drawing
Prepared by: Dr Mas Ayu bt Hassan

2. Objectives
1. Describe why the use of graphics is an effective means of
communicating when designing.
2. Describe traditional and modern design processes.
3. Define standards and conventions as applied to technical
drawings.
4. Identify the types and thicknesses of the various lines in the
alphabet of lines.
5. Identify traditional tools used for sketching.
6. Read and use mechanical and metric scales.

3. What is Graphic Communication?
• Graphic Communication is the study of using
visualizing, sketching, modelling and detailing for
clear and efficient communication in creating
and producing new products.
• Using engineering drawing & model as a language
in presenting technical ideas and problem
solutions.
• In engineering, 92% of design process is
graphically based, and only 8% mathematics,
written & verbal communications.

4. • Graphics communication will influence the
way you think & the way you approach
problems. WHY??
• Because thinking in the language of graphics,
you will visualize problems more clearly and
will use graphic images to find solutions with
greater ease.

5. Let’s imagine an aircraft

6. Do you think of this ?

7. or this ?

8. or this ?

9. Or maybe this ?

10. • Each aircraft was designed for a
specific task and within specified
parameters; however before it could
be manufactured, 3-D model &
engineering drawings must be
provided.
• Just imagine trying to communicate
all necessary details verbally or in
writing….it would be IMPOSSIBLE.

11. Why Engineering Drawing?
Real & complete language used in design
process for:
1. Visualization
2. Communication
3. Documentation

12. Sketch
an idea
Create
drawings
Manu-
facturing
Parts
Traditional tool 2-D CADD Solid modeling
CNC machine
Translate
part information
to machine code
Pencil & Paper
Ideation/Visualization Brain
Conventional machine
(manual operate)
Time
Process
Working Drawing
Interpret
by operator
Evolution of Engineering Design
Create machine code
by operator

13. Visualization
• Ability to mentally picture things that do not exist.
• Good visualization means able to picture things in their
minds, allowing them to move around the image,
change the form, look inside and make other
movements as they were holding the object.
• Greatest engineers and scientists who had powerful
visualization ability such as Albert Einstein, Leonardo da
Vinci & Thomas Edison.

14. • Visualization and the resulting sketch is the
FIRST phase in the design process.
• The ability to visualize problem solutions and
communicate them through your sketches is
one of your most important skills to become
the professional engineer.
Design sketch

15. Communication
• SECOND phase in design process is
communication drawings and models.
• Goal: To refine initial sketches so your design
solution can be communicated without
ambiguity – improve the clarity of the graphics
then creating a 3-D model using CAD
software.
• Sometimes it is necessary to have real
models, which can easily produced through a
process called rapid prototyping.

16. 3-D computer model
(Solid Modeling)

17. Examples of prototype designs

18. Documentation
• Final phase is to permanently record the
solution using documentation drawings; 2-D
details drawings (blueprint).
• Purpose is for legal and archival which follow
very strict standard practices so everyone in
engineering field can “read” the drawings.
• These standard are the “language” used to
communicate graphically, examples ISO, ANSI,
JIS and etc.

19. Multiview drawing

20. Traditional vs. Modern Design
Process

21. Team activity
(concurrent engineering)
Linear activity

22. Figure above shows many different groups, technical and non-
technical, share information in a graphic format. Computer
graphics allowing large , diverse groups to communicate faster
and more efficient.

23. Standards & Conventions
• The graphics language must follow a set of
standards and conventions in order to make
communication using technical graphics
effective.
• These standards and conventions are not
timeless and unchanging truth. Not like
English gradually changes over the years.

24. • Conventions commonly are accepted
practices, rules or methods.
• For example….

25. • Standards are sets of rules that govern how
technical drawing are presented.
ANSI standard: all
diametral dimension
should be preceded
by a phi (ø) symbol

26. • Standard used for engineering and technical
drawings, American National Standard
Institute (ANSI) assist by American Society for
Mechanical Engineers (ASME).
• Other standards: International Standard
Organization (ISO), Japanese Standards (JIS)
and etc.

27. Standard Linetypes (ASME)

28. Linetypes used on technical drawing

29. 2-29
Figure 2.1 – Use of projection
and dimensioning lines

30. 2-30
Figure 2.2 – Use of centre and
projection lines in dimensioning

31. 2-31
Figure 2.3 –
Methods of
dimensioning
(a) unidirectional
(b) aligned

32. 2-32
Figure 2.4 –
Use of staggered dimensions

33. 2-33
Figure 2.5 –
Use of overall dimensions

34. 2-34
Figure 2.6 –
Use of auxiliary dimensions

35. 2-35
Figure 2.7 – Diameters dimensioned (a) end
view (b) side view
(a)
(b)

36. 2-36
Figure 2.8 –
Methods of
dimensioning radii

37. 2-37
Figure 2.9 –
Dimensioning small spaces

38. 2-38
Figure 2.10 –
Methods of
dimensioning
spherical surfaces

39. 2-39
Figure 2.11 – Methods of dimensioning
squares

40. 2-40
Figure 2.12 – Methods of dimensioning
holes

41. 2-41
(b)
Figure 2.13 –
Positioning holes by
angular dimensions
(a)

42. 2-42
Figure 2.14 – Positioning holes by co-
ordinate dimensions
(a) (c)
(b) (d)

43. 2-43
Figure 2.15 – Methods of
dimensioning countersinks
(a) (b) (c)

44. 2-44
Figure 2.16 – Methods of
dimensioning counterbores
(a) (b) (c)

45. 2-45
Figure 2.17 – Methods of
dimensioning spotfaces
(a) (c)
(b)

46. 2-46
Figure 2.18 – Methods of
dimensioning chamfers

47. 2-47
Figure 2.19 – Methods of
dimensioning keys and keyways

48. 2-48
Figure 2.20 – Enlarged detail of
key and keyways

49. 2-49
Figure 2.22 – Methods of
dimensioning Woodruff keys

50. 2-50
Figure 2.23 – Methods of
dimensioning tapers

51. 2-51
Figure 2.3 – Methods of
representing screw threads

52. 2-52
Figure 2.24 – Methods of representing
assembled and special threads

53. 2-53
Figure 2.26 – Methods of
dimensioning threaded members

54. 2-54
Figure 2.27 – Methods of
dimensioning threads in holes

55. 2-55
Figure 2.28 – Basic profile and proportions
of the ISO metric thread

56. Technical Drawing Tools
• Computer-Aided Drawing Tools:
1. The central processing unit (CPU) – hardware
device
2. Computer operating system – software program
3. Display devices or monitors – display information
for user.
4. Input devices – Tablet, scanners, keyboard and
mouse.
5. Output devices – Printers.

57. • Traditional Tools (to assist human hand):
1. Wood & mechanical pencils.
2. Instruments set, including compass & divider.
3. 45- and 30/60-degree triangles.
4. Scales.
5. Irregular curves.
6. Eraser and erasing shields.
7. Drawing paper.
8. Circle templates.
9. Isometric templates.

58. Traditional tools used for sketching Mechanical pencils

59. Today’s Objectives:
 Apply the knowledge
of geometry
construction (using traditional
tools of drawing).
Subchapter
Geometry Construction

60. Circles
• The circle as a basic form is extremely important in
technical drawing. It is drawn with a compass. First, the
center point of the circle is marked by the centerline
crossing. Then the compass point is placed in the center
point and the circular line is drawn.

61. Bisection of a Distance AB, or Establishing Vertical
Center Line
• Draw circular arcs of an equal radius around A and B. The
points of intersection are C and D.
• The connection line CD is the asked vertical centerline. It
bisects the distance AB in E.

62. Bisection of Any Angle
• Draw a circular arc around the angle point S, that cuts the
sides of the angle. The points of intersection are A and B.
• Draw circular arcs of equal radius around A and B that meet
each other in C.
• The connection line CS bisects the angle.

63. Determination of The Center Point M of a Circle.
• Draw two chords through the circle that are approximately right angled
to each other. Note: A chord is a distance that connects two points of a
curved line.
• Establish the mid-perpendiculars on the chords (construction: see
bisection of a distance AB, or establishing a mid- perpendiculars).
• The intersection of the mid-perpendiculars is the center point M.

64. Construction of a Regular Hexagon
• The wrench-size SW is marked in mm.
• Draw a circle around the center point M with half of the wrench-size as
dimension for the radius. The intersections of the circle with the
horizontal centerline are A and B.
• Draw circular arcs with the same radius around A and B. The
intersections of the horizontal centerline are C and 0, those of the circle
are E, F, G and H.
• Connect C with E and F, as well as 0 with G and H and establish vertical
lines in A and B.

65. Connecting Circles and Straight Lines
• Two straight lines running towards each other in a right, acute or
obtuse angle are to be connected with a circular are with the radius R.
• The compass insertion point M is found when parallel lines with the
distance of R are drawn to the initial lines until they meet.
• If a perpendicular line is drawn from M to the two initial lines, the
intersection marks the joining of the circular arc and the straight lines.

66. Remarks for technical drawing:
• The transition from the circular arc to the straight line may be well
performed, if the circular arc is drawn first and followed by the straight
lines.
• Should a circle be connected with a straight line through a circular arc
with the radius R, a circular arc must be drawn around the center point
M1 of the circle with a radius of R1 + R and parallel line to the straight
line with a distance of R. The parallel line and the circular arc intersect
at M, the compass insertion point.
• If two circles are to be connected by a circular arc, a circular arc with a
radius of R1 + R is drawn around M, and a circular arc with a radius of Rz
+ R is drawn around. The circular arcs intersect at M.

68. To draw an arc tangential to two arcs (internally)

69. To draw an arc tangential to two arcs (externally)

70. Exercise

72. 5-72
Figure 3

73. 5-73
Figure 4

74. 5-74
Figure 5

75. Questions for Review
1. What is the purpose of document drawings?
2. Why are technical drawings an important
form of communication for engineers and
technologists?
3. Define standard. Lists the name of standards
commonly used in engineering drawing.
4. Define convention.
5. List three examples of how graphics are used
in engineering design.

76. • Sketch and label the concurrent engineering
model.
• Define CAD. List the CAD drawing tools.
• List the typical hand tools used to create a
sketch.