DESIGN ELEMENT INTRODUCTION
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Transcript of DESIGN ELEMENT INTRODUCTION
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8/18/2019 DESIGN ELEMENT INTRODUCTION
1/10
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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Fundamentals of Machine Elements, 3rd
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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Fundamentals of Machine Elements, 3rd
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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Fundamentals of Machine Elements, 3rd
ed.Schmid, Hamrock and Jacobson © 201 !"! #ress
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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Fundamentals of Machine Elements, 3rd
ed.Schmid, Hamrock and Jacobson © 201 !"! #ress
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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Fundamentals of Machine Elements, 3rd
ed.Schmid, Hamrock and Jacobson © 201 !"! #ress
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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8/18/2019 DESIGN ELEMENT INTRODUCTION
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Fundamentals of Machine Elements, 3rd
ed.Schmid, Hamrock and Jacobson © 201 !"! #ress
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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Fundamentals of Machine Elements, 3rd
ed.Schmid, Hamrock and Jacobson © 201 !"! #ress
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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Fundamentals of Machine Elements, 3rd
ed.Schmid, Hamrock and Jacobson © 201 !"! #ress
Conversion Factors
Table 1.4: Conversion factors anddefinitions.