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Engineering Graphics V

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Title: Team-based design and CAD modelling using Lego in first year engineering graphics Author: Ralph Buchal Last modified by: Paul Kurowski Created Date – PowerPoint PPT presentation

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Title: Engineering Graphics V


1
Engineering Graphics V
  • Prof. Jon Southen
  • October 20, 2008

2
Tolerancing
3
Tolerances
  • 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

4
Tolerancing
  • Allowable variations or tolerances must be
    specified by the designer, with two objectives
  • ensure fit and function
  • minimize manufacturing cost

5
Tolerancing
  • 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
  • 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?

6
Tolerances of Different Manufacturing Processes
7
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)

8
Tolerance Specific Parts
  • Plus and minus tolerance
  • e.g. 4.650 0.003 (bilateral tolerance)
  • e.g. 4.650 (unilateral tolerance)
  • Limit tolerance
  • Maximum and minimum sizes are specified directly
  • e.g.

9
Geometric Dimensioning and Tolerancing (GDT)
  • GDT symbols specify additional tolerancing
    information for 3D geometry
  • Used in addition to standard /- dimensioning
  • Used properly, GDT can allow looser tolerances
    to minimize manufacturing cost

10
GDT symbols
11
Example
12
Working Drawings
13
Outline
  • Definition of working drawings
  • Some basics
  • Standard sheet size
  • Dimensioning standards
  • Drawing scale
  • Projection angle
  • Title blocks
  • Detail drawings
  • Assembly drawings
  • Examples

14
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.

15
Working Drawings
  • Working drawings are the complete set of
    standardised drawings specifying the manufacture
    and assembly of a product based on its design.

16
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 (Europe) or third-angle (North
    America)

17
ANSI Standard Sheet Sizes
Metric (mm) U.S. Standard
A4 210 x 297 A-Size 8.5 x 11
A3 297 x 420 B-Size 11 x 17
A2 420 x 594 C-Size 17 x 22
A1 594 x 841 D-Size 22 x 34
A0 841 x 1189 E-Size 34 x 44
18
Dimensioning Standards
  • Specify appearance of arrowheads, dimension
    lines, text alignment, etc.
  • ANSI North America
  • ISO Europe
  • DIN Germany
  • JIS Japan
  • Etc.

19
Metric Scale
  • Each view on a drawing has an associated scale
  • Unless otherwise specified, the drawing scale is
    used

11 Full size
12 Half size
15 Fifth size
110 Tenth size
120 Twentieth size
150 Fiftieth size
20
Title Blocks
  • Drawing title blocks typically contain the
    following
  • 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)

21
Title Block
22
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

23
Other Required Information
  • Revision block
  • records revisions to drawing
  • CAD packages create these automatically
  • Tolerance specifications
  • assumed tolerances for all dimensions, unless
    otherwise specified on the drawing

24
Requirements for Working Drawings
  • Completely describe the parts
  • Show the parts in an assembly
  • Identify all the parts
  • Specify standard parts

25
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

26
Detail Drawings
  • Dimensioned, multi-view drawing of a single part
  • All information required for manufacture,
    including
  • Dimensions and tolerances
  • Material
  • Surface finish
  • Etc.

27
Dimensioned Detail Drawing
28
Example Detail Drawing
29
http//www.tpub.com/content/draftsman/14040/img/14
040_47_1.jpg
30
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

31
Elements of an Assembly Drawing
  • All parts shown in one drawing
  • assembled view
  • sectioned assembly
  • exploded assembly
  • Parts list or bill of materials (BOM)
  • part ID, quantity, description, catalog number,
    etc.
  • Balloons
  • each part is identified by a numbered balloon,
    and referenced to the parts list
  • Machining and assembly instructions

32
Assembly Drawing
33
Exploded Assembly Drawing
34
(No Transcript)
35
Sectioned assembly
http//www.jatsgreenpower.com/Uwtech3.gif
36
Example
37
Example
38
Example
  • MicroLux Drill Press 81631 Assembly Drawing

http//www.micromark.com/html_pages/instructions/8
1631i/81631g.gif
39
Example
  • Harley Sportster Transmission

http//www.nightrider.com/biketech/images/xl_cam_a
ssembly.gif
40
Example Geared Locomotive (1896)
41
Examples from Westerns Formula SAE Team
SolidWorks rendering of 2005 car
42
Formula SAE Shock Absorber
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