CAD_Lecture_3_R1.pdf
-
Upload
yuhui-choi -
Category
Documents
-
view
212 -
download
0
Transcript of CAD_Lecture_3_R1.pdf
1
Computer Aided Design
Lecture 3UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
22
Dimensioning
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningCommunication
Engineering drawing communicate or
conveys information in:
◦ describing the form/shape of the component,
usually by using orthographic and sometimes
pictorial views
◦ giving actual dimensions of all features of the
geometry
◦ giving information about any special
manufacturing processes and materials required
33
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningGeneral Rules
General rules
◦ Standards and conventions should be followed
◦ Dimensions should be placed on drawings so that they may be easily read
◦ The drawing must include the minimum number ofdimensions required to accurately manufacture the design
◦ A dimension should not be stated more than once, unless it aids communication
◦ If use in manufacturing, it should not be necessary for the machinist to have the calculation on any dimensions
44
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningTypes of Dimension
Dimensioning can be broadly
classified as:
◦ Size dimensions. Used to describe heights, widths,
diameters, etc.
◦ Location dimensions. Used to place various
features of a component relative to each other,
such as a hole centre line to a reference surface
◦ Mating dimensions. Used for parts that fit together
requiring a certain degree of accuracy
55
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningConventions of Dimensioning
General conventions:◦ Parallel dimensions, indicating the
size of the plate
◦ edges A and B are being used as
the reference edges (datum)
◦ minimum number of dimensions
required are specified
◦ use of description of 'plate 3mm
thick', so that no side view is
required
◦ evenly spaced dimension lines
66
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningConventions of Dimensioning
General conventions:
◦ Overview
77
Gap
“Break” when
2 projection
line intercept
Short
Extension
Dimension
Thin
projection
line
Arrow
Head
Dimension
Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningConventions of Dimensioning
General conventions:
◦ Dimensioning Line
Thin lines that show where a measurement
begins and where it ends and the size of an angle
Broken for text, if needed
88
Dimension
Dimension
Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningConventions of Dimensioning
General conventions:
◦ Extension/Projection Line
Thin lines that extend the lines or edges of the object
DO NOT touch the object – away from the object
Extend past the dimension line
Break the line where appropriate
99
Short
Extension
Thin
projection
line
Gap
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningConventions of Dimensioning
General conventions:
◦ Arrow Head Used at the ends of dimension lines
Show where a dimension begins and ends
Also used on leaders
Can be open or solid
Must be uniform through out drawing
1010
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningConventions of Dimensioning
General conventions:
◦ Example 1
Parallel Dimensioning – thick dimension line, thin
projection line, well spaced of dimension lines
Superimposed Running Dimensioning – thin origin
circle of min. 3mm, dimensioned in series manner
1111
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningConventions of Dimensioning
General conventions:
◦ Example 2
A central line or projection line should never be used as dimension line
Dimension line should be drawn unbroken even in break feature
When space is constrained , an oblique strokes of min. 3mm at 45˚ instead of arrow head can be
acceptable
1212
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningDimensioning Common Features
Radii
◦ All radial dimensions are proceeded by the
capital R
shows a radius dimensioned with the centre of
the radius located on the drawing
shows how to dimension radii which do not need
their centres locating
1313
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningDimensioning Common Features
Diameter◦ Circles on engineering drawings are usually either
spheres, holes or cylinders of some description. The
dimension refers to the diameter, and the diameter symbol
is Ø
1414
The ∅40 dimension can also be
refereed to as the PCD or Pitch
Circle Diameter
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningDimensioning Common Features
Chamfers
1515
Chamfer at angle 45˚
Chamfer at angle other
than 45˚
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningDimensioning Common Features
Countersinks and counterbores:
1616
Counter-sinks
Counter-bores
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningDo & Don’t Do
Do & Don’t do
1717
Right!
Wrong!
Wrong!
Wrong!
Right!
Wrong!
Right!
Right!
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningDo & Don’t Do
Do & Don’t do
1818
Wrong! Right!
Wrong! Right!
Shaded area for
corresponding
dimension
Wrong! Right!
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
DimensioningDo & Don’t Do
Do & Don’t do
1919
Wrong! Right! Wrong! Right!
Wrong! Right!Wrong!Wrong!But, not
recommended
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Dimensioning
Parallel Dimensioning◦ Parallel dimensioning consists of several dimensions
originating from one projection line
2020
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Dimensioning
Chain Dimensioning◦ Chains of dimension should only be used if the function of
the object won't be affected by the accumulation of the
tolerances
2121
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Dimensioning
Superimposed Running Dimensioning◦ Superimposed running dimensioning simplifies parallel
dimensions in order to reduce the space used on a
drawing. The common origin for the dimension lines is
indicated by a small circle at the intersection of the first
dimension and the projection line.
2222
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Dimensioning
Combined Dimensioning◦ A combined dimension uses both chain and parallel
dimensioning
2323
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Dimensioning
Dimensioning Small Features◦ When dimensioning small features, placing the
dimension arrow between projection lines may create a
drawing which is difficult to read
2424
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Dimensioning
Unidirectional system ◦ all dimension texts are always vertical upright
Aligned system ◦ dimension text ca be placed on or in line with the
dimension lines
2525
Aligned SystemUnidirectional
System
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Dimensioning
Can be classified in to:
◦ Justify
◦ Controls justification of the text
Align, fit, centre, middle, right etc.
◦ Style
◦ Specifies the text style, which determines the
appearance of the text characters
Time News Roman, Arial, Rockwell etc.
2626
AutoCADAutoCAD AutoCAD
V
e
r
t
i
c
a
l
S
t
y
l
eH o r i z o n t a l S t y l
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Placement of Drawing
How?
2727
Good
Drawing
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Placement of Drawing
Or
2828
X XX
Y
Y
Y
Clean,
Neat &
TidyGood
Drawing
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
292929
Line Convention
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•Visible Line
◦ represent features that can be seen in
the current view
◦ lines, edges, corners
30303030
Line ConventionVisible Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
• Centre Line◦ symmetrical parts and features, such as cylinders
and holes (alternating long and short thin dashes)
◦ in circular view, short dash should cross at the intersections of centre line
◦ for small hole, centre line is
presented as thin continuous line
◦ centre line should not extend
between views
31313131
Line ConventionCentre Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•Hidden Line◦ a dashed line that represents a line,
edge or corner, which exists but cannot
be seen or concealed from view due to
obstructed view by part of the object or
of another object
32323232
Line ConventionHidden Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Principle of Hidden Line
33333333
Line ConventionPrinciple of Hidden Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
• In summary
34343434
1. Visible
2. Hidden
3. Center
Line ConventionSummary
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•Precedence of Line• when 2 or more types of lines are happened to
be in the same location
• order of precedence
• A continuous line takes precedence over a hidden line and a hidden line takes precedence over a centerline
353535
Line ConventionPrecedence of Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•Precedence of Line• e.g.
363636
Line ConventionPrecedence of Line
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•Line TypesTHICK• Visible object line 0.60 to 0.70 mm
• Cutting plane line 0 70 to 0.90 mm
• Border line 0.70 to 0.90 mm
• Break Line 0.45 to 0.70 mm
THIN• Hidden line 0.30 to 0.35 mm
• Section line 0.25 to 0 30 mm
• Centerline 0.30 to 0.35 mm
• Dimension line 0.30 to 0.35 mm
373737
Line ConventionLine Types
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•What they look like?
383838
Line ConventionLine Types
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•Example 1
393939
Line ConventionLine Types
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
•Example 2
404040
Line ConventionLine Types
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
414141
Scale
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
• Scale drawings allows the engineer and
drafter to create drawings which are
proportionately the same as the product it
represents.
•Using scale, Very large objects or very
small objects can fit on a standard size
paper accurately.
42424242
Scale
UNIVERSITI TUNKU ABDUL RAHMAN(UTAR)
FACULTY OF ENGINEERING AND SCIENCE
Scale representation
◦ Scale 2:1
DOUBLE SIZE :2 millimeters on paper =1
millimeter on the parts
◦ Scale 1:1
FULL SIZE: 1 millimeter on paper =1
millimeter on the parts
Scale