Transcript Pictorial Drawings - ETP - Engineering Technology Pathways

Isometric Drawing
ETP 2005 – Dan Houston
This material is based upon work supported by the National Science Foundation under Grant
No. 0402616. Any opinions, findings and conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the view of the National
Science Foundation (NSF).
Axonometric Projections
Step by Step:
Isometric Sketching
Isometric Projection vs.
Sketch
Isometric projections are foreshortened because the object is tipped
with respect to the viewing plane. Isometric sketches are not usually
foreshortened because they still appear proportionate when showing
the dimensions full size along isometric axis lines. It is easier just to
sketch the full dimension.
Locating Features
To locate a feature such as the upper block, make measurements from an
existing corner as shown here.
Inclined Surfaces in
Isometric
Inclined surfaces can not be measured along inclined lines in an isometric
sketch. To locate inclined surfaces you must make measurements along the
isometric axis lines.
Circles in Isometric
• Circles appear as ellispses
when drawn in an
isometric sketch.
• To sketch an isometric
circle, locate the center
and then sketch the box
that would enclose the
circular shape. Draw the
ellispse tangent to the
lines of the box.
Arcs in Isometric Sketches
Arcs are usually
sketched by
locating their
centers and
then boxing in
the enclosing
parallelogram.
Sketch the arc
tangent to the
enclosing box,
which is drawn
along isometric
lines.
Hidden Lines
Hidden lines are not usually
shown in isometric sketches
unless they are needed to
show a feature that would be
unclear.
Usually the orientation for
the isometric drawing should
be chosen so that hidden
lines aren’t needed.
Holes are assumed to go
completely through the
object unless their depth is
indicated with a note or with
hidden lines.
Exploded Isometric
Assembly
Isometric drawings are
frequently used to show
how parts assemble as
in this automobile
power module.
Oblique Pictorials
The advantage of oblique pictorials like these over isometric pictorials is
that circular shapes parallel to the view are shown true shape, making
them easy to sketch.
Oblique pictorials are not as realistic as isometric views because the
depth can appear very distorted. Oblique views cannot usually be
generated directly from a 3D model using CAD. It is primarily a sketching
technique.
Unnatural Appearance of
Oblique Drawing
Oblique drawings of objects having a lot of depth can appear very
unnatural due to the lack of foreshortening.
Perspective Drawings
• Perspective drawings produce the view that is
most realistic. A perspective drawing shows a
view like a picture taken with a camera
• There are three main types of perspective
drawings depending on how many vanishing
points are used.
• These are called one-point, two-point, and threepoint perspectives.
One Point Perspective
Orient the object so that a principal face is parallel to the viewing plane
(or in the picture plane.) The other principal face is perpendicular to the
viewing plane and its lines converge to a single vanishing point.
Terminology
One-point Perspective
Sketching
front
1. Sketch
surface of
object and
locate
vanishing
point.
Sketch receding lines
2. Sketch
receding lines
from
intersections
and points of
tangency on
front surface to
vanishing
point.
3
.
Estimate the
depth of the
object you will
show and
block in the
back surface
between the
receding lines.
Shading Techniques