Product Manufacturing and Cost Estimating Using Cad/Cae. The Computer Aided Engineering Design Series

555 Pages·2013·63.21 MB·English

by  Kuang-Hua Chang (Auth.)

CHAPTER
1
Introduction to e-Design
CHAPTER OUTLINE
1.1 Introduction......................................................................................................................................2
1.2 Thee-DesignParadigm......................................................................................................................5
1.3 VirtualPrototyping............................................................................................................................7
1.3.1 ParameterizedCADProductModel..................................................................................7
ParameterizedProductModel................................................................................................8
AnalysisModels.....................................................................................................................9
MotionSimulationModels...................................................................................................10
1.3.2 ProductPerformanceAnalysis......................................................................................11
MotionAnalysis...................................................................................................................11
StructuralAnalysis..............................................................................................................12
FatigueandFractureAnalysis.............................................................................................12
ProductReliabilityEvaluations.............................................................................................12
1.3.3 ProductVirtualManufacturing......................................................................................13
1.3.4 ToolIntegration...........................................................................................................14
1.3.5 DesignDecisionMaking...............................................................................................15
DesignProblemFormulation...............................................................................................16
DesignSensitivityAnalysis...................................................................................................16
ParametricStudy................................................................................................................17
DesignTrade-OffAnalysis...................................................................................................18
What-IfStudy......................................................................................................................19
1.4 PhysicalPrototyping.......................................................................................................................19
1.4.1 RapidPrototyping........................................................................................................19
1.4.2 CNCMachining...........................................................................................................22
1.5 Example:SimpleAirplaneEngine....................................................................................................23
System-LevelDesign...........................................................................................................23
Component-LevelDesign.....................................................................................................25
DesignTrade-Off.................................................................................................................26
RapidPrototyping...............................................................................................................27
1.6 Example:High-MobilityMultipurposeWheeledVehicle....................................................................27
HierarchicalProductModel.................................................................................................28
PreliminaryDesign..............................................................................................................29
DetailDesign.......................................................................................................................31
DesignTrade-Off.................................................................................................................33
1
ProductManufacturingandCostEstimatingusingCAD/CAE.http://dx.doi.org/10.1016/B978-0-12-401745-0.00001-0
Copyright(cid:1)2013ElsevierInc.Allrightsreserved.
2 CHAPTER 1 Introduction to e-Design
1.7 Summary.......................................................................................................................................36
QuestionsandExercises........................................................................................................................36
References...........................................................................................................................................36
Sources................................................................................................................................................38
Conventionalproductdevelopmentemploysadesign-build-testphilosophy.Thesequentiallyexecuted
developmentprocessoften results inprolonged lead times andelevatedproductcosts. The proposed
e-Design paradigm employsIT-enabledtechnologyfor product design,includingvirtual prototyping
(VP) to support a cross-functional team in analyzing product performance, reliability, and
manufacturing costs early in product development, and in making quantitative trade-offs for design
decision making. Physical prototypes of the product design are then produced using the rapid pro-
totyping (RP) technique and computer numerical control (CNC) to support design verification and
functional prototyping, respectively.
e-Designholdspotentialforshorteningtheoverallproductdevelopmentcycle,improvingproduct
quality, andreducingproductcosts. It offers three concepts and methods for product development:
• Bringingproductperformance,quality, andmanufacturing costs together early in design
for consideration.
• Supportingdesigndecision making based on quantitativeproductperformance data.
• Incorporating physical prototyping techniquesto supportdesignverification and functional
prototyping.
1.1 INTRODUCTION
A conventional product development process that is usually conducted sequentially suffers the
problemofthedesignparadox(Ullman1992).Thisreferstothedichotomyormismatchbetweenthe
design engineer’s knowledge about the product and the number of decisions to be made (flexibility)
throughouttheproductdevelopmentcycle(seeFigure1.1).Majordesigndecisionsareusuallymadein
the early design stage when the product is not very well understood. Consequently, engineering
FIGURE1.1
Thedesignparadox.
1.1 Introduction 3
changes are frequently requested in later product development stages, when product design evolves
and isbetter understood, tocorrect decisions made earlier.
Conventional product development is a design-build-test process. Product performance and reli-
abilityassessmentsdependheavilyonphysicaltests,whichinvolvefabricatingfunctionalprototypes
of the product and usually lengthy and expensive physical tests. Fabricating prototypes usually
involves manufacturing process planning and fixtures and tooling for a very small amount of
production.Theprocesscanbeexpensiveandlengthy,especiallywhenadesignchangeisrequestedto
correct problems found in physical tests.
Inconventionalproductdevelopment,designandmanufacturingtendtobedisjoint.Often,manu-
facturability of aproduct isnotconsidered in design. Manufacturing issues usually appearwhen the
design is finalized and tests are completed. Design defects related to manufacturing in process
planningorproductionareusuallyfoundtoolatetobecorrected.Consequently,moremanufacturing
procedures are necessary for production,resulting inelevatedproductcost.
With this highly structured and sequential process, the product development cycle tends to be
extended,costiselevated,andproductqualityisoftencompromisedtoavoidfurtherdelay.Costsand
the number of engineering change requests (ECRs) throughout the product development cycle are
oftenproportionalaccordingtothepatternshowninFigure1.2.Itisreportedthatonly8%ofthetotal
productbudgetisspentfordesign;however,intheearlystage,designdetermines80%ofthelifetime
cost of the product (Anderson 1990). Realistically, today’s industries will not survive worldwide
competitionunlesstheyintroducenewproductsofbetterquality,atlowercost,andwithshorterlead
times.Manyapproachesandconceptshavebeenproposedovertheyears,allwithacommongoaldto
shorten the productdevelopment cycle,improveproductquality, andreduceproductcost.
Anumberofproposedapproachesarealongthelinesofvirtualprototyping(Lee1999),whichis
a simulation-based method that helps engineers understand product behavior and make design deci-
sions in a virtual environment. The virtual environment is a computational framework in which the
geometricandphysicalpropertiesofproductsareaccuratelysimulatedandrepresented.Anumberof
successful virtual prototypes have been reported, such as Boeing’s 777 jetliner, General Motors’
locomotiveengine,Chrysler’sautomotiveinteriordesign,andtheStockholmMetro’sCar2000(Lee
1999). In addition tovirtual prototyping,the concurrentengineering (CE) conceptand methodology
havebeenstudiedanddevelopedwithemphasisonsubjectssuchasproductlifecycledesign,design
FIGURE1.2
Cost/ECRversustimeinaconventionaldesigncycle.
4 CHAPTER 1 Introduction to e-Design
for X-abilities (DFX), integrated product and process development (IPPD), and Six Sigma
(Prasad1996).
Althoughsignificantresearchhasbeenconductedinimprovingtheproductdevelopmentprocess,
and successful stories have been reported, industry at large is not taking advantage of new product
development paradigms. The main reason is that small and mid-size companies cannot afford to
developanin-housecomputertoolenvironmentlikethoseofBoeingandtheBig-Threeautomakers.
Ontheotherhand,commercialsoftwaretoolsarenottailoredtomeetthespecificneedsofindividual
companies; they often lack proper engineering capabilities to support specific product development
needs,andmostofthemarenotproperlyintegrated.Therefore,companiesareusingcommercialtools
to support segments of their product development without employing the new design paradigms to
their fulladvantage.
The e-Design paradigm does not supersede any of the approaches discussed. Rather, it is simply
arealizationofconcurrentengineeringthroughvirtualandphysicalprototypingwithasystematicand
quantitativemethod fordesigndecisionmaking.Moreover,e-Designspecializesinperformanceand
reliability assessment and improvement of complex, large-scale, compute-intensive mechanical
systems. Theparadigm alsousesdesignformanufacturability(DFM),designformanufacturingand
assembly(DFMA),andmanufacturingcostestimatesthroughvirtualmanufacturingprocessplanning
andsimulationfor design considerations.
The objectiveof this chapter is to present an overview of the e-Design paradigm and the sample
tool environment that supports a cross-functional team in simulating and designing mechanical
products concurrently in the early design stage. In turn, better-quality products can be designed and
manufacturedatlowercost.Withintensiveknowledgeoftheproductgainedfromsimulations,better
design decisions can be made, breaking the aforementioned design paradox. With the advancement
of computer simulations, more hardware tests can be replaced by computer simulations, thus
reducing cost and shortening product development time. The desirable cost and ECR distributions
throughouttheproductdevelopmentcycleshowninFigure1.3canbeachievedthroughthee-Design
paradigm.
Atypical e-Designsoftware environmentcan bebuiltusingacombinationofexistingcomputer-
aideddesign(CAD),computer-aidedengineering(CAE),andcomputer-aidedmanufacturing(CAM)
as the base, and integrating discipline-specific software tools that are commercially available for
specificsimulationtasks.Themaintechniqueinbuildingthee-Designenvironmentistoolintegration.
Toolintegrationtechniques,includingproductdatamodels,wrappers,engineeringviews,anddesign
processmanagement,havebeendeveloped(Tsaietal.1995)andaredescribedinDesignTheoryand
MethodsusingCAD/CAE,abookinTheComputerAidedEngineeringDesignSeries.Thisintegrated
e-Design tool environment allows small and mid-size companies to conduct efficient product devel-
opmentusingthee-Designparadigm.Thetoolenvironmentisflexiblesothatadditionalengineering
toolscan beincorporated with alesser effort.
In addition, the basis for tool integration, such as product data management (PDM), is well
establishedincommercialCADtoolsandsonowheelneedstobereinvented.Thee-Designparadigm
employs three main concepts and methods for product development:
• Bringingproductperformance,quality, andmanufacturing cost for design considerations in the
early design stagethrough virtualprototyping.
• Supportingdesigndecision making through aquantitativeapproach for both conceptand detail
designs.
1.2 The e-Design Paradigm 5
FIGURE1.3
(a)Cost/ECRversuse-Designcycletime;(b)productknowledgeversuse-Designcycletime.
• Incorporating productphysical prototypes for designverification and functional tests via rapid
prototypingand CNC machining,respectively.
Inthischapterthee-Designparadigmisintroduced.Thencomponentsthatmakeuptheparadigm,
includingknowledge-basedengineering(KBE)(GonzalezandDankel1993),virtualprototyping,and
physical prototyping, are briefly presented. Designs of a simple airplane engine and a high-mobility
multipurpose wheeled vehicle (HMMWV) are briefly discussed to illustrate the e-Design paradigm.
Detailsofmodelingand simulationare provided inlater chapters.
1.2 THE e-DESIGN PARADIGM
AsshowninFigure1.4,ine-Design,aproductdesignconceptisfirstrealizedinsolidmodelformby
design engineers using CAD tools. The initial product is often established based on the designer’s
experience and legacy data of previous product lines. It is highly desirable to capture and organize
6 CHAPTER 1 Introduction to e-Design
FIGURE1.4
Thee-Designparadigm.
designerexperienceandlegacydatatosupportdecisionmakinginadiscreteformsoastorealizean
initial concept. The KBE (Gonzalez and Dankel 1993) that computerizes knowledge about specific
product domains to support design engineers in arriving at a solution to a design problem supports
the concept design. In addition, a KBE system integrated with a CAD tool may directly generate
a solid model of the concept design that directly serves downstream design and manufacturing
simulations.
WiththeproductsolidmodelrepresentedinCAD,simulationsforproductperformance,reliability,
andmanufacturingcanbeconducted.Theproductdevelopmenttasksandthecross-functionalteamare
organizedaccordingtoengineeringdisciplinesandexpertise.Basedonacentralizedcomputer-aided
designproductmodel,simulationmodelscanbederivedwithpropersimplificationsandassumptions.
However,aone-waymappingthatgovernschangesfromCADmodelstosimulationmodelsmustbe
established for rapid simulation model updates (Chang et al. 1998). The mapping maintains consis-
tencybetween CAD and simulationmodelsthroughout the product developmentcycle.
Product performance, reliability, and manufacturing can then be simulated concurrently. Perfor-
mance,quality,andcostsobtainedfrommultidisciplinarysimulationsarebroughttogetherforreview
by the cross-functional team. Designvariablesdincluding geometric dimensions and material prop-
ertiesoftheproductCADmodelsthatsignificantlyinfluenceperformance,quality,andcostdcanbe
identified by the cross-functional team in the CAD product model. These key performance, quality,
andcostmeasures,aswellasdesignvariables,constituteaproductdesignmodel.Withsuchamodel,
asystematicdesignapproach,includingaparametricstudyforconceptdesignandatrade-offstudyfor
detaildesign,canbeconductedtoimprovetheproductwithaminimumnumberofdesigniterations.
The product designed in the virtual environment can then be fabricated using rapid prototyping
machines for physical prototypes directly from product CAD solid models, without tooling and
processplanning.Thephysicalprototypessupportthecross-functionalteamfordesignverificationand
1.3 Virtual Prototyping 7
assembly checking. Change requests that are made at this point can be accommodated in thevirtual
environment without high cost and delay.
The physics-based simulation technology potentially minimizes the need for product hardware
tests. Because substantial modeling and simulations are performed, unexpected design defects
encountered during the hardware tests are reduced, thus minimizing the feedback loop for design
modifications.Moreover,theproductionprocessissmoothsincethemanufacturingprocesshasbeen
plannedandsimulated.Potentialmanufacturing-relatedproblemswillhavebeenlargelyaddressedin
earlierstages.
AnumberofcommercialCADsystemsprovideasuiteofintegratedCAD/CAE/CAMcapabilities
(cid:3) (cid:3)
(e.g., Pro/ENGINEER and SolidWorks ). Other CAD systems, including CATIA and NX, support
one or more aspects of the engineering analysis. In addition, third-party software companies have
madesignificanteffortsinconnectingtheircapabilitiestoCADsystems.Asarepresentativeexample,
CAE and CAM software companies worked with SolidWorks and integrated their software into
(cid:3)
SolidWorks environments such as CAMWorks . Each individual tool is seamlessly integrated into
SolidWorks.
In this book, Pro/ENGINEER and SolidWorks, with a built-in suite of CAE/CAM modules, are
employed as the base for the e-Design environment. In addition to their superior solid modeling
(cid:3)
capability based on parametric technology (Zeid1991),Pro/MECHANICA andSolidWorks Simu-
lation support simulations of nominal engineering, including structural and thermal problems.
Mechanism Design of Pro/ENGINEER and SolidWorks Motion support motion simulation of
mechanical systems. Moreover, CAM capabilities implemented in CAD, such as Pro/MFG
(Parametric Technology Corp., www.ptc.com), and CAMWorks, provide an excellent basis for
manufacturing process planning and simulations. Additional CAD/CAE/CAM tools introduced to
supportmodelingandsimulationofbroaderengineeringproblemsencounteredingeneralmechanical
systems can be developedand added to the tool environment asneeded.
1.3 VIRTUAL PROTOTYPING
Virtualprototypingisthebackboneofthee-Designparadigm.Aspresentedinthischapter,VPconsists
ofconstructingaparametricproductmodelinCAD,conductingproductperformancesimulationsand
reliability evaluations using CAE software, and carrying out manufacturing simulations and cost
estimatesusingCAMsoftware.ProductmodelingandsimulationsusingintegratedCAD/CAE/CAM
software are the basic and common activitiesinvolved invirtualprototyping. However, a systematic
designmethod,includingparametricstudyanddesigntrade-offs,isindispensablefordesigndecision
making.
1.3.1 Parameterized CAD Product Model
A parametric product model in CAD is essential to the e-Design paradigm. The product model
evolves to a higher-fidelity level from concept to detail design stages (Chang et al. 1998). In the
conceptdesignstage,aconsiderableportionoftheproductmaycontainnon-CADdata.Forexample,
when the gross motion of the mechanical system is sought the non-CAD data may include engine,
tires, or transmission if a ground vehicle is being designed. Engineering characteristics of the non-
CAD parts and assemblies are usually described by engineering parameters, physics laws, or
8 CHAPTER 1 Introduction to e-Design
FIGURE1.5
Airplaneenginemodel:(a)CADmodeland(b)modeltree.
mathematical equations. This non-CAD representation is often added to the product model in the
concept design stage for a complete product model. As the design evolves, non-CAD parts and
assemblies are refined into solid-model forms for subsystem and component designs as well as for
manufacturing process planning.
A primary challenge in conducting product performance simulations is generating simulation
models and maintaining consistency between CAD and simulation models through mapping. Chal-
lengesinvolvedinmodelgenerationandinstructuralanddynamicsimulationsarediscussednext,in
which an airplane engine model in the detail design stage, as shown in Figure 1.5, is used for
illustration.
Parameterized Product Model
A parameterized product model defined in CAD allows design engineers to conveniently explore
design alternatives for support of product design. The CAD product model is parameterized by
definingdimensionsthatgovernthegeometryofpartsthroughgeometricfeaturesandbyestablishing
relationsbetweendimensionswithinandacrossparts.Throughdimensionsandrelations,changescan
be made simply by modifying a few dimensional values. Changes are propagated automatically
throughout the mechanical product following the dimensions and relations. A single-piston airplane
enginewithachangeinitsborediameterisshowninFigure1.6,soasillustratingchangepropagation
through parametric dimensions and relationships. More in-depth discussion of the modeling and
parameterization ofthe engine examplecan befound in Product Design Modeling using CAD/CAE,
abook inThe ComputerAided Engineering Design Series.
1.3 Virtual Prototyping 9
FIGURE1.6
Designchangepropagation:(a)borediameter¼1.3in.;(b)borediameterchangedto1.6in.;(c)relationsof
geometricdimensions.
Analysis Models
For product structural analysis, finite element analysis (FEA) is often employed. In addition to
structuralgeometry,loads,boundaryconditions,andmaterialpropertiescanbeconvenientlydefined
in the CAD model. Most CAD tools are equipped with fully automatic mesh generation capability.
This capability is convenient butoften leads to large FEA models with somegeometric discrepancy
10 CHAPTER 1 Introduction to e-Design
FIGURE1.7
Finiteelementmeshesofaconnectingrod:(a)CADsolidmodel,(b)h-versionfiniteelementmesh,and
(c)p-versionfiniteelementmesh.
atthepartboundary.Plus,triangularandtetrahedralelementsareoftentheonlyelementssupported.
An engine connecting rod example meshed using Pro/MESH (part of Pro/MECHANICA) with
default mesh parameters is shown in Figure 1.7. The FEA model consists of 1,270 nodes and 4,800
tetrahedron elements, yet it still reveals discrepancy to the true CAD geometry. Moreover, mesh
distortionduetolargedeformationofthestructure,suchashyperelasticproblems,oftencausesFEA
to abort prematurely. Semiautomatic mesh generation is more realistic; therefore, tools such as
(cid:3) (cid:3) (cid:3)
MSC/Patran (MacNeal-Schwendler Corp., www.mscsoftware.com) and HyperMesh (Altair
Engineering, Inc., www.altair.com) are essential to support the e-Design environment for mesh
generation.
In general, p-version FEA (Szabo´ and Babu(cid:1)ska 1991) is more suitable for structural analysis in
termsofminimizingthegapingeometrybetweenCADandfiniteelementmodels,andinlesseningthe
tendency toward mesh distortion. It also offers capability in convergence analysis that is superior to
regular h-version FEA. As shown in Figure 1.7c, the same connecting rod is meshed with 568
tetrahedronp-elements,usingPro/MECHANICAwithadefaultsetting.Aone-waymappingbetween
changesinCADgeometricdimensionsandfiniteelementmeshforbothh-andp-versionFEAscanbe
established through a design velocity field (Haug et al. 1986), which allows direct and automatic
generation ofthe finiteelementmesh of newdesigns.
Anotherissueworthconsideringisthesimplificationof3Dsolidmodelstosurface(shell)orcurve
(beam)modelsforanalysis.Capabilitiesthatsemiautomaticallyconvert3Dthin-shellsolidstosurface
models are available in,for example, Pro/MECHANICA andSolidWorks Simulation.
Motion Simulation Models
Generatingmotionsimulationmodelsinvolvesregroupingpartsandsubassembliesofthemechanical
systeminCADasbodiesandoftenintroducingnon-CADcomponentstosupportamultibodydynamic
simulation (Haug 1989). Engineers must define the joints or force connections between bodies,
including joint type and reference coordinates. Mass properties of each body are computed by CAD
withthe materialpropertiesspecified.IntegrationbetweenMechanism Design and Pro/ENGINEER,
as well as between SolidWorks Motion (Chang 2008) and SolidWorks, is seamless. Design changes
madeingeometricdimensionspropagatetothemotionmodeldirectly.Inaddition,simulationtools,