Mechanical Engineering Drawing
MECH 211
LECTURE 2
The design process
• A design is created after analysis, full understanding of
requirements and constraints and synthesis
• Two individuals may not come with the same solution to
the same problem
– Example: Connect two straight pipes ND 4” to avoid
leaking of the gas and to permit easy maintenance of
the segment
Solutions to the problem
• Multiple: flanges, clips, clamps, seals, etc.
The design process
The design process
1. Problem Defn.
2. Concept and
ideas
3. Solutions
4. Models/Prototype
5. Production and
working drawings
Concurrent engineering
approach
The design process
Drawings in product development
Sketches
Mechanical
Engineer
Assembly
Drawings
Quality
Assurance
Prod.
drawings
Vendors/
Customers
Functional
Drawings
Designer
Production
Shops
Assembly
Drawings
Assembly
Drawings in product development
Content of the lecture
• Drawing instruments and practices
• Graphic constructions – more during the
tutorial period
• Computer Aided Design (CAD) Tools
• CAD comprehensive tools
• Demonstration on AutoCAD
Assignments
• This week you will start to solve assignments
• The problem numbers and page numbers are given in the
web (for edition 8) along with the due date for
submission.
• Draw on paper the solution
• Submit the hard-copy to the relevant TA
Tutorials
• There is no scheduled AUTOCAD lab for this course
• However you can do practice with AutoCAD during the
tutorials and or in any free time you have.
• Most ENCS labs are equipped with AutoCAD.
Anatomy of Engg. Laboratory
• Starting 2007, there is a lab component for this course
• The schedule and venue for the lab is available in the
course outline
• Safety is of utmost importance
• So is your preparation for what you have to do during
your scheduled time in the lab
Drawing instruments
• Depending on the practice condition
• Basic representations performed by free hand sketching
– require paper and pencil
• To-scale sketching requires drafting tools
• Component design – CADS tools
– Changes could be fast operated
– Solid model is created
– Analysis is carried out with minimal effort
– Easy portable
Drafting tools
• Engineering drafting tools
Parallel rulers, Squares (30º/60º)
• Draw straight lines
• Provide support to
squares for lining
(hatching)
• Draw straight perpendicular
lines
• Draw parallel lines to a
specific direction
Compasses, dividers
• Draw circles, arcs
• Used to perform geometric constructions: divisions,
measurements, copying of dimensions
• Used to draw specific angles:
• 30º, 60º, 45º, 90º
Protractors, T-squares, splines
• Measure angles, maintain a fixed direction, connect two
lines by a curve
Why learn to use drafting tools?
• CAD Tools are not easily available – computer, power
and software are needed
• Some jobs could be easier performed using graphics
tools
• Hand drawing is another skill that the designer needs to
acquire
• Enhances the designer capability to perform better quality
free hand sketching
Why free-hand sketching?
• Perform a sketch without rulers, triangles or compasses,
only by free hand
• Ideation, conceptual proofing, technical dialogue – all
require free-sketching capabilities
• Often, the first conceptual sketches are carried out
outside an office
• Added skills to the designer
• Include within the sketch all the needed information or to
convey or to understand when reviewing, an idea.
Free Hand Sketching
• Example:
Free Hand Sketching
• Sketches could be performed for various level of
detailing
Free Hand Sketching
• Projection type is also important
Free Hand Sketching
• The ultimate objective
– the working
drawing production
Free Hand Sketching
• How to practice?
• Select objects that you could sketch for various levels of
detailing – DRAW IT!
• Try to represent one of your ideas on a new product (say,
a car, a boat, an airplane, etc.).
• After production, ask one of your colleagues to have a
look and tell you what he understands out from your
sketch
Graphic constructions
• EXAMPLES: Making use of the drawing tools only, draw:
– Line perpendicular to a segment passing through the
middle point
– Bisection line of an angle
– Tri-section lines of a 90° angle
– A hexagon inscribed into a given circle
– A point on a segment that divides the line in a given
ratio
Given the segment AB, draw a
line perpendicular to the direction
AB passing through the middle
of the segment AB
• Given the segment AB, Draw
line perpendicular to the
direction AB passing through
the centre of the segment AB
Example-Graphic construction
A
B
Example-GraphicGivenconstruction
the segment AB, draw a
•
line perpendicular to the direction
AB the
passing
through the
middle
Given
segment
AB,
Draw line
of the segment AB
perpendicular to the direction AB
With the compasses in the point
passing
theand
centre
of the
A and through
B respectively
opened
larger than
segment
ABhalf the segment,
•
A
B
draw two arcs, one above, one
Withbelow
compass
in the point A and B
the segment.
OBS. Maintain
the opening
of the
the
opened
larger than
half of
compasses while moving the
segment draw two arcs above and
center from one point to the other
below the segment
•
Maintain the opening of the compass
do not change it while moving
Example-Graphic construction
•
Given
thethesegment
AB,draw
Draw
Given
segment AB,
a line
line perpendicular to the direction
perpendicular
to the direction AB
AB passing through the middle
of the through
segment AB
passing
the centre of
M
the
With the compasses in the point
segment
AB
A and B respectively and opened
•
larger than half the segment,
Withdraw
compass
in the point A and B
two arcs, one above, one
belowlarger
the segment.
opened
than half of the
A
B
•
OBS. Maintain the opening of the
compasses
while
moving
segment
draw
two
arcsthe
above
center from one point to the other
below
the segment
The segment MN is the searched
line
and
Maintain the opening of the compass
do not change it while moving
N
•
Line MN is the line that is asked for
Example-GraphicGiven
construction
the segment AB, draw a
•
linethe
perpendicular
the Draw
direction
Given
segmenttoAB,
line
AB passing through the middle
perpendicular
toAB
the direction AB
of the segment
M
With through
the compasses
in the point
passing
the centre
of the
A and B respectively and opened
segment
AB half the segment,
larger than
90°
•
draw two arcs, one above, one
Withbelow
compass
in the point A and B
the segment.
OBS.larger
Maintain
the opening
of the
opened
than
half of the
A
compasses while moving the
segment
two
arcs
above
center draw
from one
point
to the
otherand
The
segment
MN is the searched
below
the
segment
line
B
•
N
2.2500
Maintain the opening of the compass
do not change it while moving
2.2500
•
Line MN is the line that is asked for
Example 2 -Graphic construction
A
O
Given an angle, find the line that
• Given an angle, find the line that
passes through point O and
divides
the anglethrough
in two equal
passes
point O and divides
parts
the angle in two equal parts
B
Example 2 -Graphic construction
an angle, find the line that
•Given
Given
an angle, find the line that
passes through point O and
A
divides the angle in two equal
passes through point
parts
O and divides the
in two
equal
Withangle
a conveninet
opening
in theparts
compass, draw an arc with the
in O and
that intersects opening
•centre
With
a convenient
both OA and OB
in the
compass draw and arc with centre in O
and that intersects OA and OB
O
B
Example 2 -Graphic construction
A
Given• an Given
angle, findan
theangle,
line that find the line that
passes through point O and
passes
through
point O and divides
divides the
angle in two
equal
parts
the angle in two equal parts
With a conveninet opening in the
compass, draw an arc with the
• With a convenient
centre in O and that intersects
both OA and OB
opening in the
compass draw and arc with centre in
With same or another
convenient
opening
the
O and
thatinintersects
OA and OB
compasses, larger than half of
the
of thesame
arc, drawor
two
• corWith
another convenient
arcs with the centres located
in theopening
previous point
in sof
compass, larger than half
interersection
O
B
of the arc size, draw two arcs with
centers located in the previous points
of intersection
Example 2 -Graphic construction
•
Given an angle, find the line that • With a convenient opening in the
find the line
that a continuous arc
passes through point O and Given an angle,
compass
draw
passes through point O and
divides the angle in two equaldivides the angle
withincentre
two equalin O and that
parts
parts
A
intersects both OA and OB
With a conveninet opening in the
through
shortest
distance
compass, draw
an arc with
the
centre in O and that intersects
both OA• andWith
OB same or another convenient
With same
or anotherin compass, larger than
opening
convenient opening in the
halflarger
of the
arcofsize, draw two arcs
compasses,
than half
the cor of the arc, draw two
with centers located in the
arcs with the centres located
in the previous
point sof
previous
points of intersection
interersection
O
• lineThe
line that connects the point O
B The
that connects the
point Owith
with the
lastlast intersection point, as
the
interection point, as shown
shown
in figure
in figure
is the bisectory
line is the bisectory
of the angle
line of the angle
wo
point
hree
Example 3 -Graphic construction
•
A
O
B
Given the 90° angle, find two lines that
pass through point O and divides the
angle in three equal parts (30° each)
Example 3 -Graphic construction
wo
point
hree
•
Given the 90° angle, find two lines that
pass through point O and divides the
angle in three equal parts (30° each)
•
With a convenient opening in the
compass draw a continuous arc with
centre in O and that intersects both OA
and OB through shortest distance
A
of
nO
A and
O
B
Example 3 -Graphic construction
wo
point
ree
•
Given the 90° angle, find two lines that
pass through point O and divides the
angle in three equal parts (30° each)
•
With a convenient opening in the
compass draw a continuous arc with
centre in O and that intersects both OA
and OB through shortest distance
•
Maintaining the same opening of the
compass, draw arcs to cut the previously
drawn arc with centre at the intersections
of the arc with OA and OB respectively
A
of
O
and
ing of
o cut
ith the
f the
ively.
O
B
o
int
ee
Example 3 -Graphic construction
The two segments
divide
90° angle
Thethe
two segments
divide the 90° angle
in three
equal
parts
in three
equal parts
A
•
Given the 90° angle, find two lines that
pass through point O and divides the
angle in three equal parts (30° each)
•
With a convenient opening in the
compass draw a continuous arc with
centre in O and that intersects both
OA and OB through shortest distance
•
Maintaining the same opening of the
compass, draw arcs to cut the
previously drawn arc with centre at the
intersections of the arc with OA and
OB respectively
f
O
nd
g of
cut
h the
the
vely.
O
B
•
The two segments divide the 90°
angle in three equal parts
Example 4 -Graphic construction
•
Given the circle of radius R, inscribe
a hexagon
inside
thea circle
Given
a circle of radius
R, inscribe
hexagon inside the circle
Example 4 -Graphic construction
•
Given the circle of radius R, inscribe a
hexagon inside the circle
•
Given a circle of radius R, inscribe a
Draw inside
two the
perpendicular
diameters that
hexagon
circle
Draw two perpendicular diameters
pass
the centre
of the circle.
that
passthrough
through the centre
of the
circle.
Select
one of
the
diameters
as
Select
one
of
the
diameters
as the
the reference. Two of the sides of the
hexagon
will be peroendicular
to the
reference.
Two of the
sides of the
other diameter.
hexagon will be perpendicular to the
other diameter
Example 4 -Graphic construction
•
•
•
Given the circle of radius R, inscribe
a hexagon
inside
thea circle
Given
a circle of radius
R, inscribe
hexagon inside the circle
Draw
two perpendicular
diameters
Draw
two perpendicular
diameters
that pass through the centre of the
that
pass
through
the
circle.
Select
one of
the diameters
as centre of the
the reference. Two of the sides of the
circle.
one toofthethe diameters
hexagon
will Select
be peroendicular
other
asdiameter.
the reference. Two of the sides of
From the intersection of the reference
diameter
with the circle,will
drawbe
two perpendicular to
the hexagon
arcs of same openeing as the circle to
the other
intersect
the givendiameter
circle in 4 points
From the intersection of the
reference diameter with the circle,
draw two arcs of same opening as
the circle to intersect the given circle
in 4 points
Example 4 -Graphic construction
•
Given the circle of radius R,
inscribe a hexagon inside the
circle
•
•
•
Draw two perpendicular diameters
that pass through the centre of the
circle. Select one of the diameters
as the reference. Two of the sixes of
Given a circle of radius R, inscribe a
the hexagon
will be perpendicular to
hexagon
inside the circle
Draw
perpendicular
diameters
thetwo
other
diameter
that pass through the centre of the
circle.
Select
oneintersection
of the diameters asof the
From
the
the reference. Two of the sides of the
hexagon
will be peroendicular
the the circle,
reference
diametertowith
other diameter.
draw
two arcsof of
From
the intersection
the same
reference opening as
diameter with the circle, draw two
the circle to intersect the given circle
arcs of same openeing as the circle to
intersect
the given circle in 4 points
in 4 points
The four points of intersection and
the
two centre
the arcs will
form
The
fourofpoints
of intersection
and
the hexagon when connected in order
two centre of the arcs will form the
hexagon when connected in order
Example 5 -Graphic construction
Given the segment AB, find the point D
such that the ratio AD/BD to be 5/6.
•
A
B
Given the segment AB, find the point
D such that the ratio of AD/BD is 5/6
Example 5 -Graphic construction
A
B
Given the segment AB, find the point D
such that the ratio AD/BD to be 5/6.
5
A ratio
a number
of 5 + 6 AB, find the point
• ofGiven
the
segment
8 requires
= 11 equal segments to be built.
such
that thedirection
ratio of AD/BD is 5/6
Draw a line
of a convenient
that passes through either point A or B,
Ratio
of 5/6
as is• more
convenient.
The requires
line should 11 equal
be long enough to accomodate 11 equal
be built. Draw a line of
segmentssegments
of a appropriatetolength.
convenient direction passing though
either A or B. the line should be long
enough to accommodate 11 equal
segments of appropriate length
D
Example 5 -Graphic construction
A
B
Given
the
segment
AB,segment
find the pointAB,
D find the point
•
Given
the
such that the ratio AD/BD to be 5/6.
A ratioD
of 85such
requires
a number
5 + 6 of AD/BD is 5/6
that
the ofratio
= 11 equal segments to be built.
Draw
line of aof
convenient
direction 11 equal
• aRatio
5/6 requires
that passes through either point A or B,
as is more
convenient. to
Thebe
linebuilt.
should Draw a line of
segments
be long enough to accomodate 11 equal
convenient
direction
passing though
segments
of a appropriate
length.
Connect the end of the last drawn
either A or B. the line should be long
segment of the auxiliary line to the
other end
of the line.
parallel
enough
toDraw
accommodate
11 equal
lines to the previously described line.
The parallel
lines will divide
the
segments
of appropriate
length
segment AB is 11 equal segments.
•
Connect the end of the last drawn
segment of the auxiliary line to the
other end of the line. Draw parallel
lines to the previously described line.
The parallel lines divide the segment
AB into 11 equal segments
Example 5 -Graphic construction
•
A
• Ratio of 5/6 requires 11 equal
Given the segment AB, find the
segments to be built. Draw a line of
Given
the
segment AB, find the point D
point D such that the ratio of
such that
the ratio AD/BD
to be 5/6. passing though
convenient
direction
AD/BD is 5/6
A ratio of 85 requires a number of 5 + 6
either A or B. the line should be long
= 11 equal segments to be built.
line of a convenient
direction
to accommodate
11 equal
B Draw aenough
D
that passes through either point A or B,
segments
length
as is more
convenient.of
Theappropriate
line should
be long enough to accomodate 11 equal
• Connect
the end
of the last drawn
segments
of a appropriate
length.
Connect
the end of the
segment
of last
thedrawn
auxiliary line to the
segment of the auxiliary line to the
other
of the
line. Draw parallel
other end
of theend
line. Draw
parallel
lines to the previously described line.
lines to the previously described line.
The parallel lines will divide the
segment
AB is
11 equal lines
segments.
The
parallel
divide the segment
Locate point D on the line AB such
AB into 11 equal segments
that AD = 5 segments while BD = 6
segments.
•
Locate point D on the line AB such
that AD = 5 segments while BD = 6
segments
Laying out an Angle

•
Draw
the line X to any convenient

length (preferably 100 units)
•
Find the Sine of the angle  in the
table of natural sine - Multiply that by
the value length of the X (in this case
100) - Use this as Radius R
Laying Out An Angle.
Sine Method.
Draw line X to any convenient length,
preferably 100 units.
Find the sine of angle q in a table of
natural sines, multiply by 100.
R = XSIN 
 = 33°16’
R = 100 x SIN 33°16’
R = 100 x 0.5485364
R = 54.85364
Laying out an Angle
•
Draw the line X to any convenient
length (preferably 100 units)

• Find the Sine of the angle  in the
table of natural sine - Multiply that
by the value length of the X (in
this case 100) - Use this as
Radius R
•
Strike an arc R = 54.85364
Laying Out An Angle.
Sine Method.
Draw line X to any convenient length,
preferably 100 units.
Find the sine of angle q in a table of
natural sines, multiply by 100, and strike
Laying out an Angle
•
Draw the line X to any convenient
length (preferably 100 units)
•
Find the Sine of the angle  in the

table of natural sine - Multiply that
by the value length of the X (in
this case 100) - Use this as
Radius R


•
Strike an arc R = 54.85364
•
Draw the other side of the angle
tangent to the arc
Laying Out An Angle.
Sine Method.
Draw line X to any convenient length,
preferably 100 units.
Find the sine of angle q in a table of
natural sines, multiply by 100, and strike
Transfer a Triangle
•
Set of any side of the given triangle, such as ABC, in the new location.
Start from the selected location of point of choice
•
Draw an arc with the center in A of radius B
Transfer a Triangle
Set of any side of the given triangle, such as ABC, in the new location.
Start from the selected location of point of choice
Draw an arc with the center in A of radius AB (3.9365)
From A draw a line of the specified direction until intersects the arc
Transfer a Triangle
Set of any side of the given triangle, such as ABC, in the new location.
Start from the selected location of point of choice
Draw an arc with the center in A of radius AB (3.9365)
From A draw a line of the specified direction until intersects the arc
From that point B, draw an arc with the centre in B of radius BC (5.3179)
Transfer a Triangle
Set of any side of the given triangle, such as ABC, in the new location.
Start from the selected location of point of choice
Draw an arc with the center in A of radius AB (3.9365)
From A draw a line of the specified direction until intersects the arc
From that point B, draw an arc with the centre in B of radius BC (5.3179)
From A draw an arc with centre in A of radius AC (7.9186)
Transfer a Triangle
Set of any side of the given triangle, such as ABC, in the new location.
Start from the selected location of point of choice
Draw an arc with the center in A of radius AB (3.9365)
From A draw a line of the specified direction until intersects the arc
From that point B, draw an arc with the centre in B of radius BC (5.3179)
From A draw an arc with centre in A of radius AC (7.9186)
Connect B with C and again C with A. The triangle is relocated.
Draw an Arc Tangent to Two Arcs
To draw a circular arc from a given Radius R
tangent to two given circular arcs
To Draw a Circular Arc of a Given
Given
circular
arcsCircular
withArcs.
centers A and B,
Radiusthe
R Tangent
to Two Given
and
r, respectively
Given radius
the circular R
arcsand
with centers
A and B, and radius R and r,
respectively.
Using A as a center and R1 plus R as a radius, strike an arc parallel to
first arc. Using B as a center and R1 plus r as a radius, strike an
intersecting arc parallel to second arc. Because each of these
intersecting arcs are disance R1, away from arcs, C will be the center
for the required arc that is tangent to both. Mark the points of
tangency T and T that lie on the lines of centers AC and BC.
Draw an Arc Tangent to Two Arcs
To draw a circular arc from a given Radius R1
tangent to two given circular arcs
To Draw a Circular Arc of a Given
Given
circular
arcsCircular
withArcs.
centers A and B,
Radiusthe
R Tangent
to Two Given
and
r, respectively
Given radius
the circular R
arcsand
with centers
A and B, and radius R and r,
respectively.
Using A asany
a center
and R1in
plusthe
R as first
a radius,arc
strikeas
an arc
parallel toand
Using
point
centre
first arc. Using B as a center and R1 plus r as a radius, strike an
R1
as radius
strike
parallel
tothese
first arc.
intersecting
arc parallel
to secondarc
arc. Because
each of
intersecting
arcs are
disancein
R1,the
awaysecond
from arcs, C arc
will beas
the center
Using
any
point
centre
for the required arc that is tangent to both. Mark the points of
tangency
that lie on the
lines of an
centers
AC parallel
and BC.
and
R1T and
asT radius
strike
arc
to the
second arc
Draw an Arc Tangent to Two Arcs
To draw a circular arc from a given Radius R1
tangent to two given circular arcs
To Draw a Circular Arc of a Given
Radius
Tangent
to Two Given
Circular
Arcs.centers
GivenR the
circular
arcs
with
A and B,
andtheradius
Rwith
and
r, respectively
Given
circular arcs
centers
A and B, and radius R and r,
respectively.
Using
A as aany
center point
and R1 plus
as a radius,
arc centre
parallel to and
Using
inRthe
firststrike
arcanas
first arc. Using B as a center and R1 plus r as a radius, strike an
R1 as arc
radius
strike
arc
parallel
to first arc.
intersecting
parallel to
second arc.
Because
each of these
intersecting arcs are disance R1, away from arcs, C will be the center
Using any point in the second arc as centre
for the required arc that is tangent to both. Mark the points of
tangency
T andas
T that
lie on the strike
lines of centers
BC.
and R1
radius
an AC
arcandparallel
to the
second arc
Using A as centre and R1 + R as radius strike
arc parallel to first arc. Using B as centre and
R1 + r as radius strike an intersecting arc
parallel to the second arc
Draw an Arc Tangent to Two Arcs
To draw a circular arc from a given Radius R1
tangent to two given circular arcs
To Draw a Circular Arc of a Given
Given
the circular arcs with centers A and B, and
Radius R Tangent to Two Given Circular Arcs.
radius R and r, respectively
Given the circular arcs with centers A and B, and radius R and r,
respectively.
Using
a apoint
inR1the
first
arc as
and
Using A as
center and
plus R
as a radius,
strikecentre
an arc parallel
to R1 as
first arc. Using
B as an
a center
and R1
plus r asaa radius,
strike
an
radius
strike
arc.
Using
point
in
the second
intersecting arc parallel to second arc. Because each of these
arc
as centre
and R1,
R1away
asfrom
radius
strike
an arc
intersecting
arcs are disance
arcs, C will
be the center
for the required arc that is tangent to both. Mark the points of
tangency T and T that lie on the lines of centers AC and BC.
Using A as centre and R1 + R as radius strike arc
parallel to first arc. Using B as centre and R1 + r
as radius strike an arc parallel to the second arc
Since the intersecting arcs are R1 away from the
given arcs, C will be centre of the tangent arc.
Mark the points of tangency T and T that line on
the lines of AC and BC
Draw an Arc Tangent to Two Lines
Draw a circular arc of radius R tangent to two lines
Given the two lines, not at right angles, and the radius R
Draw an Arc Tangent to Two Lines
Draw a circular arc of radius R tangent to two lines
Given the two lines, not at right angles, and the radius R
Draw lines parallel to given lines at distance R. because the point of
intersection of these lines is at distance R from the both lines, it will be
centre for the required arc
Draw an Arc Tangent to Two Lines
Draw a circular arc of radius R tangent to two lines
Given the two lines, not at right angles, and the radius R
Draw lines parallel to given lines at distance R. because the point of
intersection of these lines is at distance R from the both lines, it will be
centre for the required arc
Draw arc of Radius R
Draw an Arc Tangent to Two Lines
Draw a circular arc of radius R tangent to two lines
Given the two lines, not at right angles, and the radius R
Draw lines parallel to given lines at distance R. because the point of
intersection of these lines is at distance R from the both lines, it will be
centre for the required arc
Draw arc of Radius R
Mark the points of intersection T1 and T2 are found @ the intersection of
the perpendiculars from C to sides of the angle
Computer Aided Design
• ADVANTAGES
– Create a traceable record in the documentation
– Integration of analysis, manufacturing, cost
analysis
– Solid modeling - assembly and interference
analysis
– Easy portable and shareable documentation
• DISADVANTAGES
– More effort in design
– No more drafting personnel (?)
Computer Aided Design
• Types of CAD tools
– Comprehensive – with integrated modules for
stress analysis, thermal analysis – etc (Ex:
CATIA, Pro ENGINEER, IDEAS)
– Drafting – low end CAD tools (AutoCAD)
• Cost is proportional to the capability of the tool – 85%
of companies use low end CAD tool
Computer Aided Design
INTRODUCTION
TO
AutoCAD
CAD Software
• Aimed to ease the design
– Better quality drawings (accuracy 10-14 of a unit)
– Easier to operate modifications
– Convenient archiving
– Structured organization of the documentation
– Portability and exchange
– Synergy
– Integrated approach on design, analysis, optimization,
etc.
CAD Software
• Disadvantage
– Requires special training
– Difficult to be used in the preliminary ideation
process (free hand sketching)
– Require expensive software and computing
equipment
– If not used to the entire capability, such CAD
tools are more liability than advantage
CAD Software
• Basic introduction to AutoCAD
• Used by many small industries – cost based decision
• Requires other pieces of software to be able to
integrate the design with the analysis