CHAPTER 14
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Transcript of CHAPTER 14
![Page 1: CHAPTER 14](https://reader035.fdocuments.in/reader035/viewer/2022070401/56813675550346895d9e02a1/html5/thumbnails/1.jpg)
CHAPTER 14
Pictorial Drawings and Technical Illustrations
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Learning Objectives
• Draw three-dimensional objects using 3-D coordinates
• Construct objects using isometric, diametric, or trimetric methods
• Construct objects using oblique drawing methods
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Learning Objectives
• Draw objects using one-, two-, or three-point perspective
• Apply a variety of shading techniques to pictorial drawings
• Given an orthographic engineering sketch of a part or assembly, draw the part in pictorial form using proper line contrasts and shading techniques
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Pictorial Drawings
• Often accompany 2-D orthographic multiviews• Provide a realistic 3-D view
• Help improve visualization
• Now created using CADD or illustration programs
• ASME Y14.4M, Pictorial Drawing standard
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Pictorial Drawings
• Useful for a variety of applications• Clarify basic and complicated
engineering designs• Help designers and engineers work
out spatial problems• Most often the basis for technical
illustrations
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Pictorial Drawings
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Uses of Pictorial Drawings
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Isometric Projections and Drawings
• Equal (iso) measure (metric)• Simplest form of axonometric
projection• Single scale for all axes
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Isometric and Nonisometric Planes
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Regular Isometric
• Most common• View the top of the object and the
object from either side
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Reverse Isometric
• View the bottom of the object
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Long-Axis Isometric
• Common for long objects
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Isometric Construction: Box or Coordinate Method
• Most common form of isometric construction
• Used on objects that have angular or radial features
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Isometric Construction: Centerline Layout Method
• Used on objects with many circles and arcs
• Circles in isometric are isometric ellipses
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Isometric Circles and Arcs
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Establishing Isometric Intersections
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Drawing Isometric Sections
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Drawing Isometric Threads
• Equally spaced elliptical arcs• Detailed thread representation
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Drawing Isometric Spheres
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Dimetric Pictorial Representation
• Form of axonometric projection• Two different scales for
measurement
• Missing image – go to page 566
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Trimetric Pictorial Representation
• Most involved form of axonometric projection
• Three different scales for measurement
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Exploded Pictorial Drawings
• Exploded assembly• Show the relationship of parts in a
realistic manner• Commonly used in:• Parts catalogues
• Owner's manuals
• Assembly instructions
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Exploded Pictorial Drawings
• Isometric drawings most common• Can include centerlines between
part and subassembly axes• Can use solid extension lines
between non-cylindrical features, parts, and subassemblies
• Can include balloons
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Exploded Pictorial Drawing
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Oblique Drawing
• Shows three faces of the object• Useful if one face of an object
needs to be shown flat
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Cavalier Oblique
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Cabinet Oblique
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General Oblique
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Perspective Drawings
• Most realistic pictorial illustration• Show depth and distortion
perceived by the human eye• Objects appear smaller the farther
away they are until they vanish at a point on the horizon
One-point or parallel perspective Two-point or angular perspective Three-point perspective
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General Perspective Drawing Concepts
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One-Point Perspective
• Plan view is oriented so the front surface of the object is parallel to the picture plane
• Elevation view is placed below and to the right or left of the plan and rests on the ground line
• Used most often when drawing interiors of rooms
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Two-Point Perspective
• Two principal planes are at an angle to the picture plane
• Two vanishing points provide another dimension to the depth of the perspective
• Most popular form of perspective drawing• Exteriors of houses and small buildings
• Civil engineering projects
• Machine parts (occasionally)
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Three-Point Perspective
• Time consuming to construct• Often occupy a considerable area
on the drawing sheet• Used to illustrate objects having
great vertical measurements, such as tall buildings
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Drawing Circles and Curves in Perspective
• Circles in perspective typically appear as ellipses
• Any circle on surface parallel to the picture plane appears as a circle
• Construction using the coordinate method
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Basic Shading Techniques