Transcript Sketching - California University of Pennsylvania

TED 105: Communicating
Technical Designs
• Sketching and Shape Description
– Straight Lines
– Circles and Arcs
– Proportions
– Generating Technical Designs
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.
Freehand Sketching
• Most original designs are first expressed
on medium as a freehand sketch.
• Used for:
– Amplifying and clarifying
– Recording
verbal explanations
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.
Types of Sketches
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.
Do you want to be a good
sketcher?
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.
Proposed Notebook Sample
Size requirements.
Shows design details
Title
Initialed and dated.
Sketching Techniques
• Line Types:
Vertical Line
Horizontal Line
Inclined Line
Sketching Techniques
• Finding the slope angle of an inclined line:
Equation:
tans = RISE/RUN
tans = 2/4
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.
tans = .5
s = arctan .5
s  27
Sketching Techniques
• Sketching a Line.
Sketching Techniques
• Sketching an Arc
Sketching Techniques
• Sketching an Arc
Sketching Techniques
• Sketching a Circle
1) Setup the
diameter
2) Square in the
diameter
3) Sketch
diagonals
Sketching Techniques
• Sketching a Circle
4) Identify triangle
centers
5) Sketch arcs
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.
Size and Proportion
• How to create proper size and proportion.
Technique I
– Using a pencil to measure.
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.
Figure 2
Size and Proportion
• How to create proper size and proportion.
Technique I
– Using a pencil to measure.
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.
Figure 3
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
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
Alphabet of Lines
Alphabet of Lines
Short Break Line: A freehand
Object Line: Thick lines
Hidden Line: Lines used to
drawn line that shows where a part is
about .6mm(.032in) that show
show interior detail that is not visible
broken to reveal detail behind the part or
the visible edges of an object.
Center
Line: Lines
from
the outside
of thethat
part.define
to shorten a long continuous part. (See
Section
Lines are
used to
the center
of Lines:
arcs, circles,
or symmetrical
parts. of Long Break Line
example
define
there
material
They
arewhere
half as
thickis as
an object line. on the next slide.)
after a part of the object is cut away.
Construction Line: Very lightly
drawn lines used as guides to help draw
all other lines and shapes properly.
Usually erased after being used.
Alphabet of Lines
Dimension
Lines
that
used
to A line used to
Cutting
Plane
Line:
Long Break
Lines:Lines:
Break
lines
areare
used
are
drawn
on
designate
where
a part has been cut
to either show
show distance.
detail or asArrows
in this
case
they
canthe
Extension
Lines:
Lines
used
to
show
where
ends
show
where
the
dimension
starts
and
ends.
away
toline
see
detail.
The
arrows should
be to
used
to shorten
very
long
objects
that
achange
dimension
starts
and located
stops
an
object.
The
actual
distance
is usually
inthe
the
middle of
this
point
in
direction
that
you are
do not
in detail.
Notice
that on
this
part
with
dimension
lines
properly
dimension
lineisUsed
to
letlong
you however
know
thewe
distance
being
communicated.
looking
at the cutout.
12”
havetoshortened
object. with
The
line
1/16”to
from the
Dimension
lines
areislines
used
inaway
conjunction
thean
drawing
break
use
part as
notextension
get
confused
the object lines
with
lineswith
to properly
ourto
space
more
efficiently.
dimension objects.
Leader Lines: Leader lines are used to
show dimensions of arcs, circles and to help
show detail. An arrow head is used to point
to the part you are dimensioning and the line comes
off the arrow point usually at a 45 degree angle.
At the end of this line a horizontal line is drawn
with a note at the end telling information
How many lines from the
about what is being pointed at.
previous slide can you identify
here?
Alphabet of lines
Phantom Lines: Phantom lines are used
to identify alternate positions that a part my
take up. In this example we are using Phantom
lines to show that the door handle may only move
45 degrees from it’s horizontal
position.
How many lines from the
previous 2 slides can you
identify here?
PROJECTIONS
•Pictorial
•Isometric
•Oblique
•Caviler
•Cabinet
•Perspective
•Orothographic
Pictorial
• Pictorial sketches are sketches that
show height, width, and depth all in one
view. There are three common types:
– Isometric
– Oblique
– Perspective
Isometric
Width and depth lines
are drawn at 30 degrees from
the horizon line.
Note one view shows
height width and depth.
Oblique
Front view is true
Width
sizelines
andare
shape.
parallel with the
horizon.
Depth lines are drawn
at an angle with the
horizon.
In Cavalier Oblique depth
is fullDepth
size. in
This
an cube
oblique
has the
same
Easiest
ofheight,
the pictorials
pictorial
is width
and depthto
dimensions
draw.
distorted.
Oblique
Width lines are
parallel with the
horizon.
In Cabinet Oblique depth
is half size. This allows the view
to look more realistic.
Front view is true
size and shape.
Perspective
• Perspective is a way to draw that shows a
view of the object in the most realistic way.
Vanishing points are used to guide the
lines in the object to the horizon line or the
horizontal line you see at your line of sight.
We will discuss one and two point
perspective.
One Point Perspective
All lines in the depth project
to one point (vanishing
point). The location of the
vanishing point is based
on your line of sight.
Note: The vanishing
point in this sample
is chosen for
demonstration.
Two Point Perspective
In two point perspective
the depth lines converge on one
vanishing point (VP2) and the
width lines converge on the
other vanishing point (VP1).
Shading
• Shading allows us to create a more
realistic image by showing how light
reflects on the object. We use shading in
engineering graphics to show features not
easily seen otherwise. There are two
main types of shading:
– Straight Line
– Stippling
Shading
(Straight Line)
Shading
(Stipple Shading)
Orthographic
(Multiview Drawings)
• Pictorial sketches are great for engineers to
explain ideas and communicate what the final
part will look like to the customer. Unfortunately,
pictorial drawings have some disadvantages.
Foreshortened views and distorted features do
not allow for accurate prototyping. Many times,
for parts to be accurately depicted, you need
straight on views of each surface.
Orthographic
(Multiview Drawings)
• In order to obtain these straight line views
we have a type of drawing called
Orthographic Projection also known as
Multiview drawings. Orthographic
projection is a way to project a view based
on a line of sight that is perpendicular to
that view. There are six of these views to
any object as shown in the next slide.
Orthographic
(Multiview Drawings)
The arrows represent the
line of sight associated
with each view.
Use the button
below to jump
between this
view and the ortho
view on the next
page.
ORTHO
Orthographic
Principal Views
Note how the views
are oriented. Each view is
adjacent to the other as
if they were unfolded
from a 3D shape.
Front,
Top and Right views
are used most often. You can
see how other views resemble
these three except they are not
as clear due to hidden lines.
Click to go back
to ISO view.
ISO
Orthographic
Angle of Projection
• The example you have just seen is shown
in the third angle of projection. This is the
standard in the United States and Canada.
The rest of the world draws in the first
angle of projection. The following slides
will show how the views are derived and
what they look like.
Orthographic
Spacial Quadrants and Planes
In 3rd
angle
projection,
This
sketch
shows
the
the
projection
planes
used
quadrants where the angles
to create
of projection
are views
made are
from
as shown in red.
Top
Front
Right Side
Orthographic
3rd Angle Projection
Views are projected onto planes
that exist on the face of that view.
Arrows show the direction of the
projection
ISO Symbol
Back
Orthographic
Spacial Quadrants and Planes
Side
Top
In 1st angle projection
the projection planes used to
create the views are
as shown in red.
Front
Orthographic
1st Angle Projection
Views are projected onto planes
that exist on the opposite face of the
view you want to display. The
arrows show the direction
of the projection.
ISO Symbol
Back
Orthographic
View Selection
• Finding the best view of a part can be
difficult. Two or more sides may look like
the best solution for a front view. On the
next slide is a list of characteristics that
you should use in choosing your views.
Orthographic
View Selection
• Steps in selecting the front.
–
–
–
–
–
–
Most natural position or use.
Shows best shape and characteristic contours.
Longest dimensions.
Fewest hidden lines.
Most stable and natural position.
Relationship of other views
•
•
•
•
Most contours.
Longest side.
Least hidden lines.
Best natural position.
Orthographic
View Selection
Longest Dimension
Most natural position.
Best shape description.
No hidden lines.
Orthographic
View Selection Numbers
• Another decision on view selection you
need to make is how many views. You
usually do not need more than three but
you may only need one or two. The
following slides will show when to make a
decision between one, and two view
drawings.
One View Selection
Uniform shape.
Two views
will be identical
All dimensions easily
shown on one view.
One View Selection
It is also possible to
have one view drawings
of objects that are flat
and have even thickness.
Gauges and gaskets are
two such objects. We
have a gauge here on the
left.
Two View Selection
Symmetrical parts. A third view
would be identical to the other
views
Second view is necessary for
depth.
Precedence of Lines
• In multiple view drawings, many times different
line types will take up the same space, therefore,
we have line precedence. The following is an
explanation of which lines exist over others.
– Object lines over hidden and center.
– Hidden over center.
– Cutting plane lines over center lines.
• The following slide will show an example.
Precedence of Lines
An object line here takes prece
over
theprecedence
center line. over
Howeve
Object lines
took
draw
short
linessee
beyond
the hidden
lines
youthin
would
show
there
is in
a cente
from theobject
hole. to
The
center
line
underneath
object line
the top view would
show the depth
of the hole as well as the right
side view.
References
• Project Lead the Way.
www.myteacherpages.com/webpages/IED/files/​Sketchi
ng.ppt
• Madsen, David A., Shumaker, Terence M., Stark,
Catherine, Turpin, J. Lee, Engineering Drawing and
Design Second Edition,Delmar Publishers, 1996, ISBN
0-8273-6720-1.
• Brown, David, You Can Draw,North Light Books,
Cincinnati, Ohio, 1986, ISBN 0-89134-216-8.
• Olivo, Dr. C. Thomas, Olivo, Thomas P., Basic Blueprint
Reading and Sketching Sixth Edition, Delmar Publishers
Inc., 1993, ISBN 0-8273-5740-0.
References
• Johnson, Cindy M., Lockhart, Shawna D., Engineering
Design Communication, Prentice Hall, 2000, ISBN 0201-33151-9.
• Spencer, Henry Cecil, Dygdon, John Thomas, Novak,
James E; Basic Technical Drawing 6th Edition; Glencoe
McGraw Hill; New York, New York,1995, ISBN 0-02685660-3.
Do you want to be a good
sketcher?
First Slide