Transcript Sketching and Dimensioning

Visualization and Graphics
Introduction
Drafting, Sketching &
Dimensioning
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Objectives
Understanding graphics as a
communication tool
Technical sketching
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Freehand
Instrument
Computer
Projections
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Orthographic
Pictorial
Visualization
Visualization is often used as a mode of
communication between engineers
Sketches, tables, graphs, computer
generated drawings, blueprints are
various ways in which engineers
communicate via visual mediums
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How Would You Describe This?
In teams of two, describe using only
words
How effective is this approach?
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Three Basic Types of Technical
Drawings
Freehand sketches
Instrument drawings
Computer drawings
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Introduction to Projections
Present 3-D objects with 2-D media
Two Basic Categories
Orthographic
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Pictorial
Projections: Four Basic Types
Note:
Isometric is a
special case of
Axonometric
Orthographic
Projections
Axonometric
Pictorials
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Oblique
Perspective
Types of Axonometrics
Pictorial Drawings
Shows an object like you would see in a
photograph
Give a three dimensional view of a
room or structure
Three common types
 Isometric (Axonometric)
 Oblique
 Perspective
Pictorial Sketch of Kitchen
Review Questions 1-2
Isometric Drawings
The most common pictorials
Constructed with the two faces 30
degrees above the horizontal
The axes are 120 degrees between
each axis
Lines that are horizontal are drawn at
30 degrees
Vertical lines remain vertical
Isometric Projection
CUBE
• Isometric means equal measure
• All planes are equally or proportionately
shortened and tilted
• 13
All the major axes (X, Y, Z) are 120 degrees apart
Making an Isometric
Sketch
• Defining Axis
60o
60o
30o
30o
Isometric Axis
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Isometric Dimensioning
Dimension lines
are parallel to the
isometric axes
Extension lines are
extended in line
with these axes
Oblique Drawings
The front view is draw like it would be
using orthographic projection
The front view shows all features with
true shape and size
The top and side view are then
projected back from the front view
Views can be at any angle
15, 30 or 45 degrees are common
Oblique Drawing
Oblique Drawings Continued
Useful when the front contains more
details and features than the side view
A mental image can be created more
quickly than with orthographic alone
Two types of oblique drawings
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cavalier
cabinet
Review Questions 3-5
Cavalier Oblique
The entire drawing uses the same scale
Sometimes creates a distorted
appearance
Which is the cube ?
Were you right?
Cavalier Oblique
Front view true size
Receding Axis Angle
(Normally 30°, 45°
or 60°) is Variable
Depth dimension
(receding axis) true
size
Cabinet Oblique
Front view true size
Receding Axis Angle
(Normally 30°, 45°
or 60°) is Variable
Depth dimension
(receding axis) half
size
Cavalier Oblique Drawing
Cabinet Oblique
Measurements on the receding axes are
reduced by half
More visually realistic representation
Often used for drawing cabinets
Cabinet Oblique Drawing
Side by Side Comparison
Cavalier Oblique
Cabinet Oblique
Review Questions 6-8
Perspective Drawings
The most realistic of all pictorial drawings
Receding lines in the drawing “meet” at a
vanishing point instead of being parallel
Eliminates distortion at the back part of
pictorial drawings
Two types
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parallel (one-point) perspective
angular (two point) perspective
Perspective Drawing
Parallel Perspective (One Point)
One face of the object is shown as the
front view
Lines parallel to the front view remain
parallel
Lines that are perpendicular to the front
view converge at a SINGLE VANISHING
POINT
Angular Perspective (Two-Point)
Similar to isometric drawings
One edge of the object is place in front
The two faces that meet at this edge
recede to DIFFERENT VANISHING
POINTS
All lines parallel to each face go to the
different vanishing points
Angular Perspective Drawing
Types of Perspectives
Horizon Below Object
Exploded Pictorial Drawings
Used to show relative position of parts
or construction details
Used to clarify assembly sequence
Common in appliance and cabinetry
service manuals
Exploded Pictorial Drawing