Transcript ME 161 Introduction to Design

Engineering Drawings
ME 161
ME161 - Introduction to Design
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Drafting
• The drafting application is creating 2D
drawings with different views from a solid
model.
• You have a solid first, and then drawings.
• You will learn how to
– Create a drawing
– Add orthographic and section views
– Add dimensions and annotations
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ORTHOGRAPHIC VIEWS
• Orthographic Views: 2-D views of objects
where the viewpoint of the object is at right
angles to surfaces.
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• An object inside
a box with its
surfaces
"projecting" on
to the sides of
the box.
• Unfold the box
to project the
views on a flat
surface.
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Drafting Example (cont.)
• Add more views
Orthographic view
Front view
TFR-ISO view
Orthographic view
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How Many Views?
• Three-view drawing is most commonly
used.
• Avoid using views more than needed.
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Isometric or Trimetric Views
Included to help visualization.
Should not be used to define object.
Optional
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Isometric & Trimetric Views
Isometric
Trimetric
TFR-ISO
TFR-TRI
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Auxiliary Views
Use to show true view of important features.
Dimensions should be in true view.
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Section Views
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Dimensioning Rules
• There are multiple ways to specify the
dimensions, but they will not all represent the
identical manufactured part.
• There should only be one way to interpret the
dimensions and tolerances.
• Choose to dimension features to maintain the
critical locations and tolerances.
• A redundant dimension should be denoted with
(ref), indicating it is only included for reference.
• Every dimension has a tolerance.
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Some Dimensioning Tips
•
•
•
•
Avoid putting dimensions on top of the part.
Avoid dimensioning to hidden lines.
Always dimension in a “true” view.
Choose to dimension in the view that shows the
feature most clearly.
– Holes should be dimensioned in the view where the
cross-section is seen.
• Minimize crossing of leader lines.
• Large dimensions are positioned outside of
small dimensions.
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Tolerances
• All dimensions must have a tolerance.
• Can show defaults with a note
Dimension tolerances:
Fractional
+/- 1/16
x.x
+/- 0.01
x.xx
+/- 0.001
x.xxx
+/- 0.0001
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Tolerance Accumulation
• Chain Dimensioning
10±0.05
10±0.05
10±0.05
10±0.05
Overall length = 30.80 to 40.20
• Baseline Dimensioning
40±0.05
30±0.05
20±0.05
10±0.05
Overall length = 30.95 to 40.05
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Tolerance Accumulation
• Direct Dimensioning
40±0.05
20±0.05
10±0.05
20±0.05
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Line Types
• Visible - are continuous
lines used to depict
edges directly visible
from a particular angle
• Hidden - are shortdashed lines that may be
used to represent edges
that are not directly
visible
• Center - are alternately
long- and short-dashed
lines that may be used to
represent the axes of
circular features
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Title Blocks
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In Your Design Project
• In the engineering drawings:
– Use dashed lines for hidden lines.
– Use center lines for the axis of symmetry of a
part or feature.
– In the title block, include the information of
part name, designer’s name, general
tolerance, material, date, units, etc.
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Example of Working or Detail
Drawings (1)
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Example of Working or Detail
Drawings (2)
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Example of Working or Detail
Drawings (3)
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Example of Exploded View or
Assembly Drawing
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