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A digital factory platform for the design of roll shop plants Terkaj, W.; Gaboardi, P.; Trevisan, C.; TOLIO TULLIO ANTONIO, Maria.; Urgo, M. This is a post-peer-review, pre-copyedit version of an article published in CIRP - JOURNAL OF MANUFACTURING SCIENCE AND TECHNOLOGY. The final authenticated version is available online at: http://dx.doi.org/10.1016/j.cirpj.2019.04.007 This content is provided under CC BY-NC-ND 4.0 license

AdigitalfactoryplatformforthedesignofrollshopplantsW.Terkaja,*,P.Gaboardib,C.Trevisanb,T.Tolioc,M.Urgoca.STIIMA–CNR,InstituteofIntelligentIndustrialTechnologiesandSystemsforAdvancedManufacturing,NationalResearchCouncilofItaly,Milano,Italyb.TENOVAS.p.A.–BUPomini,Castellanza(VA),Italyc.MechanicalEngineeringDepartment,PolitecnicodiMilano,Milano,Italy*Correspondingauthor–walter.terkaj@stiima.cnr.it

Replying to requests forquotation ina fastandeffectiveway isakeyneed for technologyproviders, inparticularmachine toolbuildersandsystemintegrators.Digitalfactorytechnologiesprovidetheopportunityofspeedingupthegenerationoftechnicaloffersthroughthedevelopmentofadigitaltwinof thesystemunderstudy, thusenabling theassessmentofdifferentcandidateconfigurationsandtheassociatedperformance. In thispaperwepresentasetofintegrateddigitaltoolstosupportthedesignofrollshopplants,i.e.,plantsdevotedtogrindingcylindersforrollingmills.Thesedigitaltoolsareaimedtosupportsengineersinthedesignofanewsystemconfigurationthroughaconfigurationworkflow,a3Denvironmentandperformanceevaluationtools.Theinteroperabilityamongthesoftwaremodulesandthereuseofknowledgeisenhancedbytheuseofsemanticwebtechnologiesandthedefinitionofacommondatamodelasanontologyrelyingontechnicalstandards.DigitalFactory,VirtualFactory,DiscreteEventSimulation,Ontology

1.Introduction

Thedesignofproductionsystemsentailscomplexworkflowsthataremoreandmoresupportedbyheterogeneousmethodologiesanddigitaltools.Machinetoolbuildersandsystemintegratorsarechallengedbytheneedtoreplytorequestsforquotationinafastandeffectivewaywhileconcurrentlyworkingonmultipletechnicalandcommercialbids.Despitetheverylimitedtimetosubmitaproposal,the preliminary design phase is of fundamental importance, because a high-quality early design gives the possibility of properlycalibratingtheassociatedquotation,thusincreasingthechancefortheproposaltobeaccepted.Moreover,incaseofsuccessfulbid,thepreliminarydesignwillhaveasignificantimpactonthesubsequentdetaileddesignphase.Increasingtheefficiencyandeffectivenessofthebidgenerationphasehasastrongimpactoncompanycompetitiveness.Indeed,some

ofthedevisedproposalsdonotleadtoanacceptedorder,inspiteoftherelevantamountofworkofthedesigndepartmentthatistypicallyoverloaded.Successfactorstowinordersinclude:• speeding-upthedesignphasetobeabletomanagemorebids;• providingthecustomerwithasetofalternativesolutionstoincreasethechancetofindasuitableproposal;• carryingoutareliableperformanceevaluationfortheproposedsystemconfigurationtosupportandjustifythedesignchoicesand

theassociatedcosts;• enrichingtheproposeddesignwith3Dvisualrepresentations(staticand/ordynamic)toenhancethetransferofinformationtothe

potentialcustomerandincreasetheinvolvementduringtheofferselectionprocess.ApproachesbasedonDigital/Virtual Factory technologies [REF], andmore recentlyDigitalTwin [1], havebeenproposedbyboth

researchersandpractitionersasviablesolutionstoimproveandspeed-upthedesignandre-configurationofmanufacturingsystemsthroughtheextensiveuseofmodellingandsimulationtools[2][3].Inaddition,VirtualFactorycanbeexploitedtosupportproductdesign,processdesign,productionplanningandcontrol,monitoring,etc.[REF]inasingleandintegratedframework.MajorICTcompanies(e.g.SiemensPLM,DassaultSystèmes,etc.)alreadyprovidecommercialsoftwaresolutionsforproduct,processandsystemdesign,generallyrecognized as Product Life-cycleManagement (PLM) organized in comprehensive suites.Nevertheless, theprice of these very largesolutionsisoneofthemainobstaclestotheadoptionoftheseapproaches,usuallylimitedtoverylargecompanies.Rather than pursuing a general and very large framework,we present the development of a set of digital factory tools and their

integrationinaplatformaimedatthedesignofaspecificclassofmanufacturingsystems,characterizedbyapre-definedarchitecture.Hereintheattentionisfocusedonrollshopplants,devotedtogrindingcylindersforrollingmills.Theproposeddigitalplatformprovidesalimitedsetoffunctionalitiestosupportthedesignofrollshops,namely,layoutdesign,resourceselection,discreteeventsimulationand3Dvisualization.Inparticular,thedigitalplatformhasbeenconceivedanddevelopedtosupportthedesigndepartmentofTENOVAS.p.A.,anItaliancompanyprovidingcompletesolutionsfortheironandsteelindustry.Thispaperisorganizedasfollows.Section2describestheindustrialproblemandtheproposedapproach,whereasSection3presents

thetechnicalsolutionandinparticularthedigitaltools.Finally,theconclusionsaredrawninSection4.

2.Industrialcaseandproposedsolution

Roll shopplants aremanufacturing systemsdedicated to thegrindingof cylinders employed in rollingmills. In the ironand steelindustry,millingisthemainprocesstoobtainsheetsofdifferentthickness.Millingplantsconsistofasetofmillingstepswheretwoormorecylindersareusedtoprogressivelyreducethethicknessofthemetalsheet.Duetothecontactwiththeprocessedmaterial,thesurfaceofcylindersisdamagedduringtherollingprocess.Therefore,exhaustedcylindersaretransferredtotherollshopareatobegrinded.Incaseofhotstripmills,cylinders(weightingbetween10and100tons)mustbefrequentlygrinded(betweentwohoursand30minutesaccordingtothepositioninthemill).Thetypicalreconditioningprocessentailsacoolingphase(onlyforhotrollingprocesses)andtheremovalofbearingstofacilitategrindingoperations.Hence,cylindersaretransferredtothemachinesthatexecutethegrindingprocess.Differentclassesofcylinders(i.e.working,intermediateandbackuprolls)areusuallyassignedtodifferentmachines,sincetheirdimensionsaresignificantlydifferent.Grindingmachines(Fig.1)processingbackuprollshaveahigherpowerandareusuallymoreversatile,beingabletoprocessawiderrangeofdifferenttypesofcylindersifproperlysetup.Handlingandtransportationofcylindersisoperatedthroughoverheadandsemi-gantrycranes.

Fig.1Arollgrindingmachine(courtesyofTENOVAS.p.A.)

Herein,themainobjectiveistodevelopadigitalplatformtosupportthedesignofrollshopplantsandthenegotiationwithpotential

customersduringthebiddingprocesswhileprovidingthefollowingkeyfunctionalities:• evaluation of the roll shop performance considering the system dynamics and the actual capacity of production resources to

quantitativelyandaccuratelyvalidatethetechnicaloffer;• fastgenerationofa3Drepresentationoftherollshopthatcanhelptooptimizetherollshoplayoutandvisualizethedynamicbehavior

ofthesystem.TheworkflowofactivitiesrelatedtothedesignofarollshopplantresemblesthatofagenericproductionsystemasrepresentedinFig.

2usingtheIDEF0formalism.

Fig.2IDEF0diagramrepresentingthereferenceworkflowofproductionsystemdesign.

TheGenerateResourceCatalogactivity(A11 inFig.2)dealswiththeformalizationofacatalogofproductionresourcesthatcanbe

includedinarollshopplant.Thisactivitymustbecarriedoutwheneverthereisanupdateinthespecificationsoftheresourcesbecauseofresearchanddevelopmentornewmarketneeds.TheDesignSystemConfigurationactivity(A12inFig.2)takesasinputtheresourcecatalogandtheinformationprovidedbyapotential

customerinthebidinquiry,e.g.buildinglayout,rollstobeemployed,butalsoproductiongoalsandconstraints.Theoutputistherollshopconfigurationconsistingofsystemlayout,selectedproductionresources,processplansandcontrolpolicies.TheEvaluateSystemConfigurationactivity(A13inFig.2)aimsatestimatingtheperformanceoftherollshopconfiguration.Various

methodologiescanbeemployedtoevaluatetheperformanceofarollshopdependingontherequiredaccuracyandlevelofdetails.Theoutputwilltypicallyincludekeyperformanceindicators(KPIs)thatcanbecomparedwiththeproductiongoalsandconstraints.Finally,thedigitalversionoftherollshopcanbevisualized(activityA14inFig.2)takingasinputtheresultsofthepreviousactivities.

Thisactivitycanbecarriedouttorunaninternalcheckofthedesignedrollshopplantortobettercommunicateaproposaltoapotentialcustomer.Itmustbenotedthat,aftercompletingactivitiesA13orA14,itmaybenecessarytostartare-designloopiftheseactivitieshighlightspecificreconfigurationneedsorbecauseofchangesincustomerrequirements.

3.DigitalRollShopplatform

ADigitalFactoryapproachwasadoptedtosupportthedesignofarollshop(cf.Fig.2)byintegratingdifferentdigitaltoolsasshowninFig.3.The basis for the implementation of this approach is a formal representation of the information involved in the design process throughacommonandsharedRollShopModel that instantiateareferenceDataModel (component1 inFig.3).Theresultingdigitalplatformischaracterizedbyastarnetworkconfigurationandeachdigitaltoolmaysupportmorethanonerollshopdesignactivity.

Fig.3.Model-basedintegrationoftoolsintheDigitalRollShopplatform

OntoGui(component2inFig.3)supportsthegenerationoftheresourcecatalog(activityA11inFig.2).RollShopConfigurator(component

3)leadstheuserthroughtheconfigurationofarollshopplant(activityA12)andshowtheresultsoftheperformanceevaluation(activityA13).RollShopSimulator(component4)enablestheperformanceevaluationofrollshopconfigurations(activityA13)viadiscreteeventsimulation, while generating also a log of events that is used to visualize the system dynamics (activity A14). Virtual RollShop(component5) is a 3D virtual reality environment supporting both the design of roll shop configurations (activity A12) and thevisualizationofsystemconfigurationsanddynamics(activityA14).Thenextsub-sectionswillgivedetailsaboutthemethodsandtoolscomposingtheproposeddigitalfactoryplatform.

3.1RollShopDataModelSemanticWebtechnologieshavebeenexploitedtofacilitatetheinteroperabilityamongthedifferentdigitaltools[4].Thedatamodel

fortherollshopdomainwasdevelopedasamodularontologyinOWL2languagetoformalizetheinformationthatisrelevanttothedesignofarollshopplantwhilereusingandextendingpreviousworks[5].Inparticularanovelontologymodulenamedrollshopwasdevelopedasanextensionofthedmanufacturingontologypresentedin[5]thatinturninheritsseveralontologymoduleslikeifcOWL[6]andSOSA/SSN[7].TheoveralldatamodelconsistsofthemoduleslistedinTable1,i.e.thenovelmodulenamedrollshop(prefixrs)andasubsetofthemodulesincludedin[5].Therollshopmoduledefinesclassesrepresentinghardwareandsoftwareelementsthatareusedtodesignarollshopplant.Table2reportsexamplesofsuchclasses,theirdefinitionandthelinkwiththeirsuper-classesdefinedinotherontologymodules.

Table1ListofontologymoduleswithprefixnamesPrefixname

PrefixIRIofontologymodule

dm http://www.ontoeng.com/dmanufacturing#expr https://w3id.org/express#ex http://www.ontoeng.com/expression#factory http://www.ontoeng.com/factory#fsm http://www.learninglab.de/~dolog/fsm/fsm.owl#ifc http://www.buildingsmart-tech.org/ifcOWL/IFC4_ADD1#ifcext http://www.ontoeng.com/IFC4_ADD1_extension#list https://w3id.org/list#osph http://www.ontoeng.com/osph#rs http://www.ontoeng.com/rollshopsosa http://www.w3.org/ns/sosa/ssn http://www.w3.org/ns/ssn/statistics http://www.ontoeng.com/statistics#

Table2Excerptofclassesdefinedintherollshopontologymodule

ClassURI ClassDefinitionrs:CoolingDownArea Area where rolls are places to cool down.

Subclassofifc:IfcSpatialZoners:StandByPlace Stand-byplacewhere the rolls canbe stored.

Subclassofdm:BufferElement,ifc:IfcElementrs:Roll Roll that isemployedintherollmillingplant.

Rolls can be of different type, e.g. work roll,backuproll.Subclassofifc:IfcElement

rs:OverheadCrane Overhead crane to move rolls along the rollshop.Subclassofifc:IfcTransportElement

rs:AutomaticLoader Semi-gantrycranetomoverollsalongtherollshop.Subclassofifc:IfcTransportElement

rs:RollGrinder Roll grinder. Subclass of ifc:IfcElement,factory:MachineTool

rs:RollStateChocking State of the roll regarding the presence ofbearing chocks (i.e. chocked or dechocked).Subclassoffsm:Simple

rs:RollStateSurface Stateoftherollregardingthesurface(i.e.wornorresurfaced).Subclassoffsm:Simple

rs:RollLength Lengthofaroll.Subclassofssn:Propertyrs:RollGrindingTask Comprehensive grinding process. Subclass of

ifc:IfcTask,factory:ManufacturingTaskTheclassesoftherollshopmodulecanbegroupedasfollows:

• apartitionschemeforthelayout(e.g.rs:CoolingDownArea);• hardware elements representing rolls (i.e. rs:Roll), transporters (e.g. rs:OverheadCrane, rs:AutomaticLoader), machines (e.g.

rs:RollGrinder),bufferswhererollscanbeplaced(e.g.rs:StandByPlace);• manufacturingoperations(e.g.rs:RollGrindingTask);• stateofobjectstorepresentdynamicbehaviors(e.g.rs:RollStateChocking,rs:RollStateSurface);• propertiesspecifyingthecharacteristicsofelements(e.g.rs:RollLength).3.2OntoGuiOntoGuiisageneral-purposegraphicaluserinterfacesupportingthedirectinstantiationofOWLontologies,i.e.A-boxontologymodules

consistingofOWLindividuals[8].OntoGuiwasemployedtogeneratethecatalogofresources(activityA11inFig.2)whilereferringtothecommondatamodel.Asforthedatamodel,modularitywasexploitedalsotoinstantiatethecatalogasasetoflibraries:LibDechockerfordechockingmachines,LibGrinder forrollgrinders,LibRoll forrolltypes,LibStorage forstand-byplaces,LibTexturing fortexturingmachines,LibTransporterfortransporters.Eachtypeofresourcedefinedinthelibrariesischaracterizedintermsofclass,properties,size,and3Dmodel(seeFig.4).Resource

catalogscanbereusedforeveryrollshopprojectandcanbeupdatedwhenevernewspecificationsareintroduced.

Fig.4.Examplesofrolls(firstrow)andstand-byplaces(secondrow).

3.3RollShopConfiguratorTheRollShopConfiguratorisagraphicaluserinterfacedevelopedinC#languagetosupportengineersinthedesignofrollshopplants

(activityA12inFig.2)byprovidingastandardizedconfigurationworkflowstartingfromthedefinitionoftherolltypesandsubsequentlyaskingtheusertoprovidetheneededinformation(e.g.processingtimes)andtakeconfigurationdecisions(e.g.routings,layout).Theelementscomposingarollshopconfigurationareselectedaccordingtoproductionresourcesavailableintheresourcecatalogsdescribedbefore.Theworkflow in theRollShopConfigurator hasbeendesigned taking into consideration theknow-howaswell as thedesignpractices in the reference company, thus aiming at guaranteeing a complete and standardized design process for all the technicalquotations.Besidethis,theRollShopConfiguratorprovidesalsoasetofreportsassessingtheperformanceoftherollshopplantintermsofKPIs(e.g.leadtimeandflowtimeforeachclassofcylinders,saturationofthemachines,etc.)thatareobtainedfromanotherdigitaltool,theRollShopSimulator.3.4RollShopSimulatorTheRollShop Simulator is a reconfigurable Discrete Event Simulator (DES) based on the commercial simulation package Arena byRockwellAutomation.TheRollShopSimulatoraimsatprovidingdesignengineerswiththecapabilityofevaluatingtheperformanceofasystemconfiguration

usingadynamicmodelwithouttheneedofbeingexpertinDES(activityA13inFig.2).ThesimulatorgroundsonaskeletonDESmodel

containingall thepossiblerangeofcharacteristicsandoptionsthatarerelevant inarollshopplant.Moreover, thesimulatorcanbedynamicallyadjustedtomodelaspecificconfigurationbyswitchingon/offtheseoptions.Asanticipated,theRollShopSimulatorprovidesasoutputasetofKPIs,e.g.theservicelevelsguaranteedbytherollshoptotherollingmill(s),statisticsrelatedtothemachines,thetransporters,utilizationofthebuffers.Finally,thesimulatorgeneratesasoutputthelogofeventstakingplaceduringthesimulationrun(s).

3.5VirtualRollShopTheVirtualRollShopwasdevelopedasanenhancementofGIOVEVirtualFactory(GIOVE-VF),a3Dvirtualrealitycollaborativetool

supportingthedesign,visualizationandexplorationof3Denvironments,inparticularfactories[9].OneofthemainadvantagesofGIOVE-VF,comparedtoothercommercialoff-the-shelfsolutions,isthecapabilitytobeeasilycustomizedandintegratedwithothersoftwaretoolsthroughitssemanticwebinterface.GIOVE-VFwasconceivedasatooltobemainlyusedbySMEs,beingalsofreeandsimpletouseandinstall.TheVirtualRollShopsupportsthemodificationofarollshopdesign(activityA12inFig.2)whenusedconcurrentlywiththeRollShop

Configuratorto:• checkthedetailedrollshoplayoutandchangetheplacementofequipmentbymeansofa3Dmanipulatorwidgetora2Duserinterface

(seeFig.5).Thepositioningofitemscanbesupportedbytheimportofanexisting2Dlayout(asaDXFdrawing)intothe3Dscene.• addandplacenewpiecesofequipment(e.g.rollgrinders,texturingmachines,cleaningcabin)byaccessingtheresourcecatalogs.The

catalogscanbeeasilyupgradedasnewelementsareofferedbythecompany(activityA11inFig.2).

Fig.5.Exampleofrollshopreconfiguration:additionofarollgrinder.Theiconsoftheresourcecatalogcanbenoticedatthebottomofthescreenshot.

Theuserinterfaceintop-rightcornerprovidedetailsabouttheselectedobject.TheVirtualRollShopcanbealsousedtovisualizethedynamicbehavioroftheplant(activityA14inFig.2),i.e.:

• movementsofthetransportersandtheircomponents(e.g.tongsandchains);• movementsofrollswithintheplant;• progressoftheprocessingintermsofchangesoftherollstatelinkedtoachangeinits3Drepresentation(Fig.6).The3DanimationisgeneratedbyautomaticallytransformingtheoutputoftheRollShopSimulatorintoasequenceofeventsaffecting

the rolls and the equipment, tracking their evolution in time in terms of placement, state, and dynamic properties [10]. Thistransformationisfacilitatedbytheunderlyingcommondatamodelandalsoprovidesacategorizationandsimplificationoftheverylargelogofthesimulationintosomethingthatismoreeasytounderstandbyahuman.TheVirtualRollShopembedsvideoplayercontrols(onthetopofFig.6)tonavigatethroughthedifferentrelevanteventsintheanimation.Thismaybeusefulto:• validatethesimulationmodel,e.g.bycheckingifthemodellinghypothesesarecorrectlyimplemented;• checkthesoundnessofthesystemconfigurationgroundingonitsvisualbehaviorandperformance;• beexploitedformarketingpurposesasanenrichedpresentationoftherollshopplantdesigntothecustomer.

Fig.6.TwoscreenshotsofVirtualRollShopshowingdifferentstatesoftherolls:workwithchocks(left),wornwithoutchocks,resurfacedwithout

chocks,andwornwithchocks(right).

4.Conclusions

TheproposedDigitalRollShopplatformwasdevelopedincooperationwithTENOVAPominitosupportthedesignofrollshopplants,specificallyfortheprocessofoffergeneration.Benefitscomingfromtheuseofthisplatformaretwofold.Firstly,thedesignprocesscanbeenriched(i.e.numberofalternativedesigns,simulation,3Dvisualization)andspeduptomatchtherequirementsofthecustomers.Secondly, the adopted ontology-based approach enables the implementation of a comprehensive but concise and extensible designplatform. Possible future developments are the exploitation of the digital model during the use phase of the plant, through asynchronizationwitharealrollshoptosupportitsmonitoringandtheimplementationofsimulation-baseddecisiontools[10].References

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