Transcript Team-based design and CAD modelling using Lego in first

ES050 – Introductory Engineering
Design and Innovation Studio
Engineering
Graphics V
Prof. Jon Southen
October 20, 2008
ES050 – Introductory Engineering
Design and Innovation Studio
Tolerancing
Tolerances
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Variations exist in all manufactured parts
Tolerances specify minimum and maximum
allowable value of a dimension
Especially important for systems of with mating
parts - if tolerances are exceeded, parts may not
fit together
Tolerancing
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Allowable variations or tolerances must be
specified by the designer, with two
objectives:
 ensure
fit and function
 minimize manufacturing cost
Tolerancing
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Tolerances can drive the manufacturing process
 e.g. a shaft must turn in a hole in a bearing
 hole .7500 to .7512, shaft .7484 to .7492
 function drives tolerance which then drives machining
process used
OR
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The manufacturing process can drive the
tolerance
 What
if drill press is only tool available to make the
hole, and it can only deliver .748 to .754?
Tolerances of Different
Manufacturing Processes
Tolerance – Specific Parts
If a part is dimensioned 4.650 ± 0.003, it
means that the part is acceptable within
the range 4.653 and 4.647
 The upper and lower limits are called limit
dimensions (4.653 and 4.647)
 The tolerance is the difference between
the limit dimensions ( 4.653 – 4.647 =
0.006)

Tolerance – Specific Parts

Plus and minus
tolerance
 e.g.
4.650 ± 0.003
(bilateral tolerance)
0
 e.g. 4.650  0.002
(unilateral tolerance)

Limit tolerance
 Maximum
and minimum
sizes are specified directly
 e.g.
4.653
4.647
4.650
4.648
Geometric Dimensioning and
Tolerancing (GD&T)
GD&T symbols specify additional
tolerancing information for 3D geometry
 Used in addition to standard +/dimensioning
 Used properly, GD&T can allow looser
tolerances to minimize manufacturing cost

GD&T
symbols
Example
ES050 – Introductory Engineering
Design and Innovation Studio
Working Drawings
Outline
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Definition of working
drawings
Some basics
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Standard sheet size
Dimensioning standards
Drawing scale
Projection angle
Title blocks
Detail drawings
Assembly drawings
Examples
Elements of Engineered
Products
Engineered products contain many parts:
 Non-standard parts that must be made
 Standard parts that can be ordered from
catalogues
 fasteners
 bearings
 gears
 etc.
Working Drawings

“Working drawings are the complete set of
standardised drawings specifying the
manufacture and assembly of a product
based on its design.”
Some Basics
Drawings use standard sheet sizes
 Specified dimensioning standards are
used
 Drawings are to a specified scale
 Specified projection angle is used

 First-angle
America)
(Europe) or third-angle (North
ANSI
Standard
Sheet
Sizes
Metric (mm) U.S.
Standard
A4 210 x 297
A3 297 x 420
A2 420 x 594
A1 594 x 841
A0 841 x 1189
A-Size 8.5” x 11”
B-Size 11” x 17”
C-Size 17” x 22”
D-Size 22” x 34”
E-Size 34” x 44”
Dimensioning Standards

Specify appearance of arrowheads,
dimension lines, text alignment, etc.
– North America
 ISO – Europe
 DIN – Germany
 JIS – Japan
 Etc.
 ANSI
Metric Scale
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Each view on a
drawing has an
associated scale
Unless otherwise
specified, the
drawing scale is
used
1:1
Full size
1:2
Half size
1:5
Fifth size
1:10
Tenth size
1:20
Twentieth
size
Fiftieth size
1:50
Title Blocks
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Drawing title blocks typically contain the following:
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Name and address of company
Title of drawing
Drawing number
Names and dates of drafter, checker, etc.
Design approvals
Predominant drawing scale
Drawing sheet size
Weight of item
Projection angle
Sheet number (if multiple sheets used)
Title Block
Part and Drawing Numbers
Every part is assigned a unique part
number for record keeping
 This allows the same part to be used in
different products
 Every drawing is also assigned a unique
number, also for record keeping
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Other Required Information
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Revision block
 records
revisions to drawing
 CAD packages create these automatically
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Tolerance specifications
 assumed
tolerances for all dimensions, unless
otherwise specified on the drawing
Requirements for Working
Drawings
Completely describe the parts
 Show the parts in an assembly
 Identify all the parts
 Specify standard parts

Elements of Working Drawings
A set of working drawings typically includes:
 Detail drawings of each nonstandard part
 Assembly drawings showing all the
standard and nonstandard parts in a single
drawing
Detail Drawings
Dimensioned, multi-view drawing of a
single part
 All information required for manufacture,
including
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 Dimensions
and tolerances
 Material
 Surface
 Etc.
finish
Dimensioned Detail Drawing
Example Detail Drawing
http://www.tpub.com/content/draftsman/14040/img/14040_47_1.jpg
Assembly Drawings
Assembly drawings show all the parts and
how they go together
 Dimensioning is not usually required
 Hidden lines usually omitted
 3D CAD packages can generate assembly
drawings directly from assembly models
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Elements of an Assembly
Drawing
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All parts shown in one drawing
 assembled view
 sectioned assembly
 exploded assembly
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Parts list or bill of materials (BOM)
 part
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ID, quantity, description, catalog number, etc.
Balloons
 each
part is identified by a numbered balloon, and
referenced to the parts list
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Machining and assembly instructions
Assembly Drawing
Exploded Assembly Drawing
Sectioned assembly
http://www.jatsgreenpower.com/Uwtech3.gif
Example
Example
Example
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MicroLux Drill Press
#81631 Assembly
Drawing
http://www.micromark.com/html_pages/instructions/81631i/81631g.gif
Example
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Harley
Sportster
Transmission
http://www.nightrider.com/biketech/images/xl_cam_assembly.gif
Example: Geared Locomotive
(1896)
Examples from Western’s Formula
SAE Team
SolidWorks rendering of 2005 car
Formula SAE Shock Absorber