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

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

Allowable variations or tolerances must be specified by the designer, with two objectives:ensure fit and functionminimize manufacturing cost

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?

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)

e.g. 4.650 (unilateral tolerance)

Limit tolerance Maximum and minimum

sizes are specified directly e.g.

648.4

650.4

002.0

0

647.4

653.4

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

Definition of working drawings

Some basics Standard sheet size Dimensioning standards Drawing scale Projection angle Title blocks

Detail drawings Assembly drawings Examples

Elements of Engineered ProductsEngineered products contain many parts: Non-standard parts that must be made Standard parts that can be ordered from

catalogues fastenersbearingsgearsetc.

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 (Europe) or third-angle (North America)

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”

Dimensioning Standards

Specify appearance of arrowheads, dimension lines, text alignment, etc.ANSI – North America ISO – EuropeDIN – GermanyJIS – JapanEtc.

Metric Scale

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

1:50 Fiftieth size

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)

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

Other Required Information

Revision blockrecords revisions to drawingCAD packages create these automatically

Tolerance specificationsassumed 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, includingDimensions and tolerancesMaterialSurface finishEtc.

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

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

Assembly Drawing

Exploded Assembly Drawing

Sectioned assembly

http://www.jatsgreenpower.com/Uwtech3.gif

Example

Example

Example MicroLux Drill Press

#81631 Assembly Drawing

http://www.micromark.com/html_pages/instructions/81631i/81631g.gif

Example

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