ieng 248 d. h. jensen 10/13/2015engineering graphics & 3-d modeling1 lecture 04 interpreting and...
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IENG 248
D. H. Jensen04/19/23 Engineering Graphics & 3-D Modeling 1
Lecture 04
Interpreting and Depicting Geometry in Orthogonal Projections
IENG 248
D. H. Jensen04/19/23 Engineering Graphics & 3-D Modeling 3
HW Assignment 03
MGC: Reading:
Finish CH 5Start CH 6
HW 03 MGC CH5:Exercises p. 207 :
5.7, # 4 (note: numbers are above object)
Exercises p.210: 5.19 (note: numbers are below object)
Exercises p.211: 5.28 (note: numbers are below object)
Note: NO borders & title blocks required on HW No more than two sets of part views per page.
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D. H. Jensen04/19/23 Engineering Graphics & 3-D Modeling 4
Line Interpretations
Construction Line Purpose:
Locate intermediate / transition points and extent of features
Weight: light, thick*
Style: semi-solid, and do not
reproduce
Visible (Object) Line Purpose:
show extent of features visible in the current view
Weight:dark, thick
Style:solid, crisp ends
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D. H. Jensen04/19/23 Engineering Graphics & 3-D Modeling 5
Line Interpretations
Center Line Purpose:
show axis and extent of symmetry
Weight: dark, thin
Style: long dash, short dash
at center, long dash
Hidden Line Purpose:
show extent of features hidden by other features
Weight:dark, thin
Style:short, even dashes
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D. H. Jensen04/19/23 Engineering Graphics & 3-D Modeling 6
Line Interpretations
(Short) Break Line Purpose:
show hidden features in detail for clarity
Weight: dark, thick
Style: solid, semi-rough
Section Line Purpose:
show cross-section of material
Weight:dark, thin
Style:solid, angled to
adjacent visible lines
Note: For demonstration only. Prefer the use of conventional breaks in practice (see CH 6).
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Views of Surfaces & Edges
Normal Surfaces Parallel to one plane of
projection and perpendicular to adjacent projections (appearing as a true sized line)
Inclined Surfaces Perpendicular to one
plane (appearing as a line of true size) and are inclined to adjacent projection planes
Oblique Surfaces Inclined to all planes of
projection and cannot appear as a true size edge in any standard view
Normal Edges Perpendicular to one
plane of projection, and appears there as a point
Are parallel to adjacent projection planes and appear in true length
Inclined Edges Parallel to one plane of
projection, where they appear in true size, but are inclined to adjacent projection planes
Oblique Edges Inclined to all planes of
projection, and cannot be shown in true length since they are never parallel to a standard projection
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Types of Surfaces
Normal Surfaces
Inclined Surfaces
Oblique Surfaces
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Types of Edges
Normal Edges
Inclined Edges
Oblique Edges
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True Length & True Angle
True Length Edges
Foreshortened Edges
True Angles
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Planar Geometry
Points Could represent a vertex of three or more surfaces Could represent the point view of an orthogonal edge
Lines Could represent the intersection of two surfaces Could represent the edge view of an orthogonal surface Could represent the extent of a curved surface
Angles Appear in true size only if the angle (intersection of two
edges) lies in a normal plane (in a plane parallel to a projection)
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Intersections & Tangencies
Intersections Are sharp transitions
where adjacent or machined surfaces meet
Are shown as lines in profile and other views
Tangencies Are smooth transitions
from a surface to an adjacent curve
Are shown as lines in profile
Are not shown as lines in other views, unless:
They transition to a normal surface
They are runoutsThey are conventional
edges
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D. H. Jensen04/19/23 Engineering Graphics & 3-D Modeling 13
Runouts & Conventional Edges
Rounds Are exterior rounded
intersections
Fillets Are interior rounded
intersections
Runouts Are small curves used
to represent the connection of a planar to a curved surface
(See Fig. 5.14 – 5.16, p.190 – 191)
Conventional Edges For certain types of
rolled / cast forms, the smooth transitions are eliminated to clarify the shape
(See Fig. 5.17 p.191)
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D. H. Jensen04/19/23 Engineering Graphics & 3-D Modeling 14
Scales
Revolution Conventions Odd, rotational symmetry
is depicted, not projected (See Figs. 5.34, and 5.35,
pp. 198)
Drawing Scale Specify drawing scale in
the title block, i.e.: Scale 1 : 5
Left side of colon are local drawing units
Right side of colon are real life units
Never measure a drawing to obtain a dimension
Never omit a required dimension from a drawing
Measuring Scales Types of Measuring
ScalesMetric ScalesInch-Foot ScalesEngineer’s ScalesArchitect’s ScalesMechanical Engineer’s
ScalesPatternmaker’s Scales
Measuring Scales are only used for taking measurements
Never use a scale as a straight edge for drawing
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