DESIGN ELEMENT INTRODUCTION

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Fundamentals of Machine Elements, 3rd

ed.Schmid, Hamrock and Jacobson

© 201 !"! #ress

Chapter 1: Introduction

The invention all admir'd, and each, how he

To be th' inventor miss'd; so easy it seem'd,

Once found, which yet unfound most would have thought

Impossible

John Milton

The i8 concept car, ahybrid sports carrequiring three liters per100 km (94 mpg) andacceleration from 0 to100 km/hr in under fiveseconds.Source: Courtesy of BMW.


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ed.Schmid, Hamrock and Jacobson

© 201 !"! #ress

Product

DevelopmentApproaches

Figure 1.1: Approaches to productdevelopment. (a) Classic approach, withlarge design iterations typical of theover-the-wall engineering approach.Source: Adapted from Kalpakjian andSchmid [2003]. (b) A more modernapproach, showing a main design flowwith minor iterations representingconcurrent engineering inputs.Source:Adapted from Pugh [1996].


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ed.Schmid, Hamrock and Jacobson © 201 !"! #ress

The Safety Hierarchy

Design Procedure 1.1: The Safety Hierarchy

A designer should attempt the following, in order, in attempting toachieve reasonable levels of safety:

1.Eliminate hazards through design.2.Reduce the risk or eliminate the hazard through safeguardingtechnology.

3.Provide warnings.4.Train and instruct.

5.Provide personal protective equipment.


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Design for Manufacture

Figure 1.2: Effect of manufacturing and assembly considerations on the design of areciprocating power saw. (a) Original design, with 41 parts and 6.37-min assembly time; (b)modified design, with 29 parts and 2.58-min assembly time.Source: Adapted from Boothroyd[1992].


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Unit Checks

Design Procedure 1.2: Procedure for Unit Checks

It is generally advisable to carry units throughout calculations. However, anexpression can generally be evaluated by:

1.Establish units of specific terms of an equation while making use ofTable 1.3a.

2.Place units of terms into both sides of an equation and reduce.3.The unit check is complete if both sides of an equation have the sameunits.


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Invisalign®

Figure 1.3: The Invisalign® product. (a) An example of an Aligner; (b) acomparison of conventional orthodontic braces and a transparent Aligner.Source: Courtesy of Align Technology, Inc.


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Invisalign® ProductionFigure 1.4: The process used inapplication of Invisalign orthodontictreatment. (a) Impressions are made ofthe patient's teeth by the orthodontist andshipped to Align Technology, Inc. Theseare used to make plaster models of thepatient's teeth. (b) High-resolution, three-dimensional representations of the teeth

are produced from the plaster models.The correction plan is then developedusing computer tools. (c) Rapid-prototyped molds of the teeth atincremental positions are producedthrough stereolithography. (d) An aligneris produced by molding a transparent

plastic over the stereolithography part.Each Aligner is used for approximatelytwo weeks. The patient is left with ahealthy bite and beautiful smile.Source: Courtesy of Align Technology, Inc.


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SI Units andPrefixes

(a) SI units

Quantity Unit SI symbol FormulaSI baseunits

Length meter m -Mass kilogram kg -Time second s -Temperature kelvin K -

SI supplementary unitPlaneangle radian rad -SI eriveunits

Energy joule J N-mForce newton N kg-m/s2

Power watt W J/sPressure pascal Pa N/m2

Work joule J N-m

(b)SI prefi!

e

sSI symbol

"ultiplicationfactor #refi! for prefi!

1,000,000,000,000=1012 tera T1,000,000,000=109 giga G1,000,000=106 mega M1000=103 kilo k100=102 hecto h10=101 deka da0.1=10−1 deci d0.01=10−2 centi c0.001=10−3 milli m0.000001=10−6 micro µ0.000000001=10−9 nano n0.000000000001 =10−12 pico p

Table 1.3: SI units and Prefixes.


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Conversion Factors

Table 1.4: Conversion factors anddefinitions.

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DESIGN ELEMENT INTRODUCTION