外文翻译--卡拉调查设计和制造机械输送系统食品加工 英文版.pdf

DOI10.1007/s00170-003-1843-3ORIGINALARTICLEIntJAdvManufTechnol(2005)25:551559S.H.Masood·B.Abbas·E.Shayan·A.KaraAninvestigationintodesignandmanufacturingofmechanicalconveyorssystemsforfoodprocessingReceived:29March2003/Accepted:21June2003/Publishedonline:23June2004Springer-VerlagLondonLimited2004AbstractThispaperpresentstheresultsofaresearchinvesti-gationundertakentodevelopmethodologiesandtechniquesthatwillreducethecostandtimeofthedesign,manufacturingandassemblyofmechanicalconveyorsystemsusedinthefoodandbeverageindustry.Theimprovedmethodologyfordesignandproductionofconveyorcomponentsisbasedontheminimisa-tionofmaterials,partsandcosts,usingtherulesofdesignformanufactureanddesignforassembly.Resultsobtainedonatestconveyorsystemverifythebenefitsofusingtheimprovedtech-niques.Theoverallmaterialcostwasreducedby19%andtheoverallassemblycostwasreducedby20%comparedtoconven-tionalmethods.KeywordsAssembly·Costreduction·Design·DFA·DFM·Mechanicalconveyor1IntroductionConveyorsystemsusedinthefoodandbeverageindustryarehighlyautomatedcustommadestructuresconsistingofalargenumberofpartsanddesignedtocarryproductssuchasfoodcartons,drinkbottlesandcansinfastproductionandassemblylines.Mostoftheprocessingandpackagingoffoodanddrinkin-volvecontinuousoperationswherecartons,bottlesorcansarere-quiredtomoveatacontrolledspeedforfillingorassemblyoper-ations.Theiroperationsrequirehighlyefficientandreliableme-chanicalconveyors,whichrangefromoverheadtypestofloor-mountedtypesofchain,rollerorbeltdrivenconveyorsystems.Inrecentyears,immensepressurefromclientsforlowcostbutefficientmechanicalconveyorsystemshaspushedcon-veyormanufacturerstoreviewtheircurrentdesignandassemblymethodsandlookatanalternativemeanstomanufacturemoreeconomicalandreliableconveyorsfortheirclients.Atpresent,S.H.Masood(a117)·B.Abbas·E.Shayan·A.KaraIndustrialResearchInstituteSwinburne,SwinburneUniversityofTechnology,Hawthorn,Melbourne3122,AustraliaE-mail:smasoodswin.edu.aumostmaterialhandlingdevices,bothhardwareandsoftware,arehighlyspecialised,inflexibleandcostlytoconfigure,installandmaintain1.Conveyorsarefixedintermsoftheirlocationsandtheconveyorbeltsaccordingtotheirsynchronisedspeeds,mak-inganychangeoveroftheconveyorsystemverydifficultandex-pensive.Intodaysradicallychangingindustrialmarkets,thereisaneedtoimplementanewmanufacturingstrategy,anewsystemoperationalconceptandanewsystemcontrolsoftwareandhard-waredevelopmentconcept,thatcanbeappliedtothedesignofanewgenerationofopen,flexiblematerialhandlingsystems2.HoandRanky3proposedanewmodularandreconfigurable2Dand3Dconveyorsystem,whichencompassesanopenre-configurablesoftwarearchitecturebasedontheCIM-OSA(opensystemarchitecture)model.Itisnotedthattheresearchintheareaofimprovementofconveyorsystemsusedinbeveragein-dustryisverylimited.Mostofthepublishedresearchisdirectedtowardsimprovingtheoperationsofconveyorsystemsandinte-grationofsystemtohighlysophisticatedsoftwareandhardware.Thispaperpresentsaresearchinvestigationaimedatim-provingthecurrenttechniquesandpracticesusedinthede-sign,manufacturingandassemblyoffloormountedtypechaindrivenmechanicalconveyorsinordertoreducethemanufactur-ingleadtimeandcostforsuchconveyors.Applyingthecon-ceptofconcurrentengineeringandtheprinciplesofdesignformanufacturinganddesignforassembly4,5,severalcriticalconveyorpartswereinvestigatedfortheirfunctionality,materialsuitability,strengthcriterion,costandeaseofassemblyintheoverallconveyorsystem.Thecriticalpartsweremodifiedandredesignedwithnewshapeandgeometry,andsomewithnewmaterials.Theimproveddesignmethodsandthefunctionalityofnewconveyorpartswereverifiedandtestedonanewtestcon-veyorsystemdesigned,manufacturedandassembledusingthenewimprovedparts.2Designformanufacturingandassembly(DFMA)Inrecentyears,researchintheareaofdesignformanufacturingandassemblyhasbecomeveryusefulforindustriesthatarecon-552sideringimprovingtheirfacilitiesandmanufacturingmethodol-ogy.However,therehasnotbeenenoughworkdoneintheareaofdesignforconveyorcomponents,especiallyrelatedtotheis-sueofincreasingnumbersofdrawingdataandre-engineeringoftheprocessofconveyordesignbasedontraditionalmethods.Avastamountofpapershavebeenpublishedthathaveinvesti-gatedissuesrelatedtoDFMAandappliedtovariousmethodolo-giestoachieveresultsthatprovedeconomical,efficientandcosteffectiveforthecompaniesunderinvestigation.ThemainclassificationsofDFMAknowledgecanbeiden-tifiedas(1)Generalguidelines,(2)Company-specificbestprac-ticeor(3)Processandorresource-specificconstraints.Generalguidelinesrefertogenerallyapplicablerules-of-thumb,relat-ingtoamanufacturingdomainofwhichthedesignershouldbeaware.ThefollowinglisthasbeencompiledforDFMguidelines6.DesignforaminimumnumberofpartsDevelopamodulardesignMinimisepartvariationsDesignpartstobemultifunctionalDesignpartsformultiuseDesignpartsforeaseoffabricationAvoidseparatefastenersMaximisecompliance:designforeaseofassemblyMinimisehandling:designforhandlingpresentationEvaluateassemblymethodsEliminateadjustmentsAvoidflexiblecomponents:theyaredifficulttohandleUsepartsofknowncapabilityAllowformaximumintoleranceofpartsUseknownandprovenvendorsandsuppliersUsepartsatderatedvalueswithnomarginaloverstressMinimisesubassembliesFig.1.Layoutofconveyorsys-temforlabellingplasicbottlesEmphasisestandardisationUsethesimplestpossibleoperationsUseoperationsofknowncapabilityMinimisesetupsandinterventionsUndertakeengineeringchangesinbatchesThesedesignguidelinesshouldbethoughtofas“optimalsuggestions”.Theytypicallywillresultinahigh-quality,low-cost,andmanufacturabledesign.Occasionallycompromisesmustbemade,ofcourse.Inthesecases,ifaguidelinegoesagainstamarketingorperformancerequirement,thenextbestalternativeshouldbeselected7.Company-specificbestpracticereferstothein-housedesignrulesacompanydevelops,usuallyoveralongperiodoftime,andwhichthedesignerisexpectedtoadhereto.Thesedesignrulesareidentifiedbythecompanyascontributingtoimprovedqualityandefficiencybyrecognisingtheoverallrelationshipsbetweenparticularprocessesanddesigndecisions.Companiesusesuchguidelinesaspartofthetraininggiventodesignersofproductsrequiringsignificantamountsofmanualassemblyormainte-nance.Notethatmostofthemethodologiesaregoodateitherbeingquickandeasytostartorbeingmoreformalandquanti-tative.Forexample,guidelinesbyBoothroydandDewhurst8onDFAareconsideredasbeingquantitativeandsystematic.WhereastheDFMguidelines,whicharemerelyrulesofthumbderivedfromexperiencedprofessionals,aremorequalitativeandlessformal9.3ConventionalconveyorsystemdesignDesignandmanufacturingofconveyorsystemsisaverycom-plexandtime-consumingprocess.Aseveryconveyorsystemisacustom-madeproduct,eachprojectvariesfromeveryotherprojectintermsofsize,productandlayout.Thesystemdesign553isbasedonclientrequirementsandproductspecifications.More-over,thesystemlayouthastofitinthespaceprovidedbythecompany.Theprocessofdesigningalayoutforaconveyorsys-teminvolverevisionsandcouldtakefromdaystomonthsorinsomeinstancesyears.Onewiththeminimumcostandmaximumclientsuitabilityismostlikelytogetapproval.Figure1showsaschematiclayoutofatypicalconveyorsysteminstalledinaproductionlineusedforlabellingofplasticbottles.Differentsectionsoftheconveyorsystemareidentifiedbyspecifictechnicalnames,whicharecommonlyusedinsimilarindustrialapplication.The“singlizer”sec-tionenablestheproducttoformintoonelanefrommultiplelanes.The“slowdowntable”reducesthespeedofproductonceitexitsfromfiller,labeller,etc.The“massflow”sec-tionisusedtokeepupwithhigh-speedprocess,e.g.,filler,labeller,etc.The“transfertable”transfersthedirectionofprod-uctflow.Thepurposeofthesedifferentconveyorsectionsisthustocontroltheproductflowthroughdifferentprocessingmachines.Atypicalmechanicalconveyorsystemusedinfoodandbev-erageapplicationsconsistsofovertwohundredmechanicalandelectricalpartsdependingonthesizeofthesystem.Someofthecommonbutessentialcomponentsthatcouldbestandard-isedandaccumulatedintofamiliesoftheconveyorsystemaresideframes,spacerbars,endplates,coverplates,insidebendplates,outsidebendplates,bendtracksandshafts(drive,tailandslave).Thesizeandquantityofthesepartsvaryaccordingtothelengthofconveyorsectionsandnumberoftrackscorrespond-ingtothewidthandtypesofchainsrequired.Theproblemsandshortcomingsinthecurrentdesign,manufacturingandassemblyofmechanicalconveyorsarevaried,butinclude:OverdesignofsomepartsHighcostofsomecomponentsLonghoursinvolvedinassembly/maintenanceUseofnon-standardpartsTable1.ConveyorcriticalpartsbasedonpartscostanalysisProductdescriptionQtyMaterialusedCost(%)Improvementpossible(Yes/No)Legset68Plasticleg+SStube20.22YesSideframe802.5mmSS16.07YesSupportchannel400CchannelSS15.00YesBendtracks8Plastic14.36NoRt.rollershaft13920dia.SSshaft6.70YesTailshaft3935dia.Stainlesssteel6.27NoSpacerbar13550X50X6SS5.43YesSupportwearstrip40040×10mmplastic5.36YesSupportsidewearstrip132Plastic3.01YesEndplate392.5mm/SS1.88YesCoverplate391.6mmS/S1.57NoBendplates82.5mm/SS1.29YesTorquearmbracket186mmS/Splate1.21YesSlotcover97Stainlesssteel0.97YesInsidebendplate82.5mm/SS0.66YesTotal100.00Criticalparts4AreasofimprovementInordertoidentifytheareasofcostreductioninmaterialandlabour,acostanalysisofallmainconveyorpartswasconductedtoestimatethepercentageofcostofeachpartinrelationtothetotalcostofallsuchparts.Thepurposeofthisanalysiswastoidentifythecriticalparts,whicharemainlyresponsibleforin-creasingthecostoftheconveyorandtherebyinvestigatemeansforreducingthecostofsuchparts.Table1showsthecostanalysisofa50-sectionconveyorsys-tem.Theanalysisrevealsthat12outof15partsconstitute79%ofthetotalmaterialcostoftheconveyorsystem,wherefurtherimprovementsindesigntoreducethecostispossible.Outofthese,sevenpartswereidentifiedascriticalparts(shownbyanasteriskinTable1)constitutingmaximumnumberofcompo-nentsinquantityandcomprisingover71%ofoverallmaterialcost.Amongthese,threecomponents(legset,sideframeandsupportchannel)werefoundtoaccountfor50%ofthetotalconveyormaterialcost.Adetailedanalysisofeachofthese12partswascarriedoutconsideringtheprinciplesofconcurrenten-gineering,designformanufactureanddesignforassembly,andanewimproveddesignwasdevelopedforeachcase10.De-tailsofdesignimprovementofsomeselectedmajorcomponentarepresentedbelow.5RedesignoflegsetassemblyInaconveyorsystem,thelegsaremountedonthesideframetokeeptheentireconveyorsystemoffthefloor.Theexistingdesignofconveyorlegswork,buttheyarecostlytomanufacture,theyhavestabilityproblems,andcausedelaysindeliveries.Thedelayisusuallycausedbysomeofthepartsnotarrivingfromover-seassuppliersontime.Themostcriticalspecificationsrequiredfortheconveyorlegsare:554StrengthtocarryconveyorloadStabilityEaseofassemblyEaseofflexibility(foradjustingheight)Figure2indicatesallthepartsfortheexistingdesignoftheconveyorleg.TheindicatednumbersarethepartnumbersdescribedinTable2,whichalsoshowsabreakdownofcostan-alysiscompletewiththelabourtimerequiredtoassembleacom-pletesetoflegs.Theexistinglegsetupconsistsofplasticlegbracketsorderedfromoverseas,stainlesssteellegtubes,whicharecutintospecifiedsizes,legtubeplasticadjustments,whichareclippedontothelegtubeatthebottomasshowninFig.2.Lugs,whicharecutinsquaresizes,drilledandweldedtothelegtubetobolttheanglecrossbracingandbackingplatetosupportlegbracketsbolts.The#ofpartsinTable2signifiesthenumberofcomponentsineachpartnumberandthequantityisthecon-sumptionofeachpartinthelegdesign.Companieshaveusedthisdesignformanyyearsbutoneofthecommoncomplaintsreportedbytheclientswasoftheinstabilityoflegs.Fromaninitialinvestigation,itbecameclearthattheconnec-tionbetweenthestainlesssteeltubeandplasticlegsbracket(partFig.2.ExistinglegdesignassemblywithpartnamesshowninTable1Table2.CostanalysisforoldlegdesignassemblyPartno.Partdescription#ofpartsQtyCostSource1Plasticlegbracket22$30.00Overseas5,6Legtubeplasticadjustment42$28.00Overseas4Lug22$4.00In-house7Anglecrossbracing11$5.00In-house2Backingplate22$4.00In-house3Legtube22$25.00In-house8Bolts66$3.00In-houseTotalassemblycost(welding)$15.00In-houseTotal1917$114.001andpart3inFig.2)wasnotrigidenough.Theconnectionsforthesepartsareonlyasingle6mmbolt.Attimes,whentheconveyorsystemwascarryingfullproductloads,itwasobservedthattheconveyorlegswereunstableandcausedmechanicalvi-bration.Oneofthemainreasonsforthiswasduetoasingleboltconnectionateachendofthelugsinpart3andpart7.Thesta-bilityoftheconveyorisconsideredcriticalmatterandrequiresrectificationimmediatelytosatisfycustomerexpectations.Consideringtheproblemsoftheexistingconveyorlegde-signandtheclientspreferences,anewdesignfortheconveyorlegwasdeveloped.Generallythestabilityandthestrengthofthelegswereconsideredastheprimarycriteriaforimprove-mentinthenewdesignproposalbutotherconsiderationswerethesimplicityofdesign,minimisationofoverseaspartsandeaseofassemblyatthepointofcommissioning.Figure3shows,thenewdesignoftheconveyorslegassembly,andTable3givesadescriptionandthecostofeachpart.Figure3showsthatthenewdesignconsistsofonlyfivemainpartsfortheconveyorslegcomparedtoeightmainpartsintheolddesign.Intheolddesign,theplasticlegbracket,thelegtubeplasticadjustmentandthelegtubewerethemostexpensiveitemsaccountingfor72%ofthecostoflegassembly.Inthenew