Chapter 5 Pictorial Sketching. Objectives Be able to explain the difference between an axonometric...
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Transcript of Chapter 5 Pictorial Sketching. Objectives Be able to explain the difference between an axonometric...
Chapter 5
Pictorial Sketching
Objectives
Be able to explain the difference between an
axonometric projection and an oblique
projection.
Be able to explain the difference between an
isometric projection and an isometric
drawing/sketch.
Be able to create an isometric and oblique
sketches from an actual object and multiview
drawing.
Axonometric& ObliqueProjection
Axonometric Projection
AB
CD
Parallel & normalto picture plane
Lineof
sightA
B
CD
Axonometric ProjectionType of axonometric drawing
a
b c2. Dimetric Two angles are equal.
b
a
c3. Trimetric None of angles are
equal.
a
b c1. Isometric All angles are equal.
AB
CDA
B
C
D
Axonometric axis
Axonometric axis
Axonometric axis
A
BC
D
Lineof
sight
Parallel & obliqueto picture plane
Oblique Projection
A
D
C
B
Oblique Projection
A
D
C
B
B
C D
A
Oblique drawing angle
30o45o 60o
Type of Oblique drawing
45o 45o
1) Cavalier 2) Cabinet
Fullscale Half
scale
Isometric Projection& Isometric drawing
Rotate 45about vertical axis
Tilt forward (35o16’)
Isometric Projection
All edges foreshortenabout 0.8 time.
Isometric DrawingIsometric drawing is a drawing drawn on an isometric
axes using full scale.
Isometric projection(True projection)
Isometric drawing(Full scale)
Forshorten
Full scale
Positions of Isometric AxesIsometric axes can be arbitrarily positioned to create
different views of a single object.
Regularisometric
Reverse axisisometric
Long axisisometric
View point is lookingdown on the top ofthe object.
View point is lookingup on the bottom ofthe object.
View point is lookingfrom the right (or left)of the object.
Distance in Isometric Drawing
Isometric line is the line that run parallel to
any of the isometric axes.
Isometric axes
True-length distances are shown along
isometric lines.
Nonisometric lines
Isometric Sketching
2. Define an isometric axis.
3. Sketching the enclosing box.
4. Estimate the size an and relationship of each
details.
5. Darken all visible lines.
1. Place the object in the position which its shape
and features are clearly seen.
Sketch from an actual object
STEPS
1. Positioning object.
2. Select isometric axis.
3. Sketch enclosing box.
4. Add details.
5. Darken visible lines.
Sketch from an actual object
1. Positioning object.
2. Select isometric axis.
3. Sketch enclosing box.
4. Add details.
Note In isometric sketch/drawing), hidden lines are omitted
unless they are absolutely necessary to completely
describe the object.
Sketch from an actual objectSTEPS
5. Darken visible lines.
1. Interprete the meaning of lines/areas in
multiview drawing.
2. Locate the lines or surfaces relative to isometric
axis.
Sketch from multiview drawing
Front View
Top View
Side View
Example 1 : Object has only normal surfaces
Bottom View
Bottom
FrontSide
SideFront
Top
Regular
Reverse
WD
H
H
DW
Example 2 : Object has inclined surfaces
W
H
D
y
x Front View
y
x
Nonisometric line
Nonisometric line
A
A x
y
x
xB
B
AB
C
C
C
x
y
Example 3 : Object has inclined surfaces
A
A
B
B
C D
E
D
EF
F
x
y
Front View
Regular
C
Example 4
Reverse
Circle & Arc in IsometricIn isometric drawing, a circle appears as an ellipse.
2. Construct an isometric square.
3. Sketch arcs that connect the
tangent points.
Sketching Steps
1. Locate the center of an ellipse.
Circle & Arc in Isometric
3. Construct a perpendicular
bisector from each tangent point.
4. Locate the four centers.
5. Draw the arcs with these centers
and tangent to isometric square.
Sketching Steps
Four-center method is usually used when drawn an
isometric ellipse with drawing instrument.
2. Construct an isometric square.
1. Locate the center of an ellipse.
Example 5
Irregular Curve in Isometric
1. Construct points along the
curve in multiview drawing.
2. Locate these points in the
isometric view.
3. Sketch the connecting lines.
Steps
ObliqueSketching
Object Orientation Guidelines
Place complex features (arc, hole, irregular shapesurface parallel to frontal plane.
Object Orientation GuidelinesThe longest dimension of an object should beparallel to the frontal plane.
GOOD
WORSE
GOOD
WORSE
Object Orientation Guidelines
Which orientation is better ?
D
45
ESTIMATE DEPTHESTIMATE LINES
Sketch from actual object
Sketch from multiview drawing
Sketch from multiview drawing
AB
C
D
E
Sketch from multiview drawing
AB
C
D
E
Sketch from multiview drawing
AB
D
E
C
Sketch from multiview drawing
AB
D
E
C
Sketch from multiview drawing