机械类毕业设计外文及其翻译.docx

机械类毕业设计外文及其翻译.docx

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机械类毕业设计外文及其翻译

译文

原文题目：

Stateoftheartinroboticassembly

译文题目：

用机械手装配的发展水平

学院：

机电工程学院

专业班级：

09级机械工程及自动化01班

学生姓名：

学号：

From:

Stateoftheartinroboticassembly

Roboticassemblysystemsoffergoodperspectivesfortherationalizationofassemblyactivities.Variousbottlenecksarestillencountered,however,inthewidespreadapplicationofroboticassemblysystems.Thisarticlefocusesontheexternaldevelopments,bottlenecksanddevelopmenttendenciesinroboticassembly.

Externaldevelopments

Thecurrentmarkettrendsare:

Increasinginternationalcompetition,shorterproductlifecycle,increasingproductdiversity,decreasingproductquantity,shorterdeliverytimes,higherdeliveryreliability,higherqualityrequirementsandincreasinglabourcosts.Nexttothesemarketdevelopments,technologicaldevelopmentsalsoplayarole,offeringnewopportunitiestooptimizeprice,qualityanddeliverytimeintheirmutualrelationships.Thetechnologicaldevelopmentsareamongotherthings:

informationtechnology,newdesignstrategies,newprocessingtechniques,andtheavailabilityofflexibleproductionsystems,suchasindustrialrobots.Companieswillhavetoadjusttheirpolicytothesemarketandtechnologydevelopments（marketpullandtechnologypush,respectively）.Thispolicyisdeterminedbythecompanyobjectivesandthecompanystrategywhichlieatitsbasis.Undertheinfluenceoftheexternaldevelopmentsmentioned,thecompanyobjectivescan,ingeneral,bedividedinto:

highflexibility,highproductivity,constantandhighproductquality,shortthroughputtimes,andlowproductioncosts.Optimizingthesecompetitionfactorsnormallyresultsinthegenerationofmoremoney,andthus（greater）profits.Torealizethisobjective,mostcompanieschoosethefollowingstrategies:

reductionofcomplexity,applicationofadvancedproductiontechnologies,integralapproach,qualitycontrol,andimprovementoftheworkingconditions.Figure1showsthecompanypolicyinrelationtotheexternaldevelopmentstowhichthecompanypolicyshouldbeadjusted.

Figure1.Externaldevelopmentsandcompanypolicy

Withregardtotheproductandproductiondevelopment,asubdivisioncanbemadeintothefollowingstrategieswhichinvolve[1]:

Theproduct:

designformanufacturing/assembly,ashortdevelopmenttime,amorefrequentdevelopmentofnewproducts,functionintegrationtominimizethenumberofparts,miniaturizationandstandardization.

Theprocess:

improvedcontrollability,shortercycletimesandminimalstocks.Thereisatrendincreasinglytocarryoutprocessesindiscreteproductioninflowform.

Theproductionsystem:

theuseofuniversal,modular,andreliablesystemcomponents,highsystemflexibility（inrelationtodecreasingbatchsizes,andincreasingproductvariants）,andtheintegrationofproductsystemsintheentireproduction.

Stateoftheart

Partsmanufacturingandassemblytogetherformcoherentsub-processeswithintheproductionprocess.Inpartsmanufacturing,therawmaterialisprocessedortransformedintoproductpartsinthecourseofwhichtheform,sizesand/orpropertiesofthematerialarechanged.Inassemblytheproductpartsareputtogetherintosubassembliesorintofinalproducts.Figure2showstherelationshipsbetweenthesefunctionalprocessesandthemostimportantcontrolprocesseswithinanindustrialenterprise.Thisshowsthatassemblybymeansofmaterialorproductflowsislinkedtopartsmanufacturing,andthatbymeansofinformationflowsitisintegratedwithmarketing,productplanning,productdevelopment,processplanningandproductioncontrol.

Figure2.Assemblyaspartoftheproductionprocess

Assemblyformsanimportantlinkinthewholemanufacturingprocess,becausethisoperationalactivityisresponsibleforanimportantpartofthetotalproductioncostsandthethroughputtime.Itisoneofthemostlabour-intensivesectorsinwhichtheshareofthecostsoftheassemblycanamountfrom25to75percentofthetotalproductioncosts[1].Researchshowsthattheshareofthelabourcostsintheassemblyinrelationtothetotalmanufacturingcostsisapproximately45percentforlorryengines,approximately55percentformachinetools,andapproximately65percentforelectricalapparatus[1].Thecentreofthecostitemsmovesmoreandmorefromthepartsmanufacturingtotheassembly,asautomationofthepartsmanufacturinghasbeenintroducedonalargerscaleandmoreconsistentlythanfortheassembly.Thisismainlyduetothecomplexityoftheassemblyprocessandisalsoaresultofassemblyunfriendlyproductdesigns.Asaresult,therearehighassemblycosts.Furthermore,itappearsthatassemblyaccountsforapproximately20to50percentofthetotalthroughputtime[1].

Ontheonehand,rationalizationandautomationoftheassemblyoffergoodopportunitiestominimizetheproductioncostsandthethroughputtime.However,successdependsonnumerousfactors,suchasanintegralperceptionofassemblyinconjunctionwithmarketing,productplanning,productdevelopment,processplanning,productioncontrolandpartsmanufacturing（seeFigure2）.Forthispurpose,anassembly-friendlyproductandprocessdesignareofessentialimportance.Researchshowsthatthedesigncostsofaproductamounttoonlyapproximately5percentofthemanufacturingcostsonaverage,andthattheproductdesigninfluencesapproximately70percentofthesecosts.Examplesarealternativematerialchoice,differentlyshapedparts,and/orhavingonepartfulfilvariousfunctions.Ontheotherhand,rationalizationandautomationoftheassemblyprovidetheopportunityoftakingadvantageofexternaldevelopments,suchasincreasingproductdiversity,shorterdeliverytimes,andashorterproductlifecycle（seeFigure1）.

Exceptforthecomplexityoftheproductandprocessdesign,theperformanceofroboticassemblysystemsisalsodeterminedbythedegreeofsynchronizationbetweentheassemblysystemandthepartsmanufacturing,theflexibilityoftheend-effectorsandoftheperipheralequipment,aswellasbythesystemconfiguration.InJapan,mostroboticassemblysystemshavealineconfigurationincontrastwiththesystemsintheUSAandEurope.ApartfromEuropeandtheUSA,preferenceisincreasinglygiventoroboticassemblysystemsinJapan,insteadofmanualandmechanizedsystems.ThelargestareaofapplicationofroboticassemblysystemsinJapanistheelectromechanicalindustry（40percent）,followedbythecarindustry（approximately27percent）.

Increasingly,robotapplicationsareenvisagedfortheassemblyofcomplexfinalproducts,inseveralvarietiesandinlowtomedium-highproductionvolumes.Researchhasshownthatroboticassemblyoffersgoodperspectivesinsmalltomedium-sizebatchproductionwithannualproductionvolumesbetween100,000and600,000productcompositionspershift.Theproductionvolumesforroboticassemblycellsliebetweenapproximately200and620productsperhour,andforroboticassemblylinesbetweenapproximately220and750productsperhour[1].

Bottlenecks

Experiencehasshownthatvariousbottlenecksstillthwartthewidespreadapplicationofroboticassemblysystems.Thesebottlenecksinclude:

ahighcomplexityoftheproductandprocessdesign,alowqualityleveloftheproductparts,aswellasproductdependenceoftheperipheralequipment.FromastudyinGermanyintotheautomationoftheassemblyprocessin355companies,itappearedthat40percentofthecompanieshadanunsuitableproductdesign,30percenthadtoocomplexprocessingoftheparts,and25percenthadtoocomplexassemblyoperations[5].Thisstudyconfirmstheimportanceofdesignforassembly（DFA）.

Thesecondareainwhichdifficultiesoccurconcernsthelimitedaccuracyoftheproductpartswhichmakestheassemblyprocessunnecessarilycomplex.Thisproblemcanbesolvedbyoptimizingthemachiningprocessesinthepartsmanufacturing,andapropersynchronizationbetweenthepartsmanufacturingandtheassemblyprocess.Theintegrationofpartsmanufactureintoassemblyisalsoanoption.

Thethirdareainwhichdifficultiesoccurinvolvestherobotandtheperipheralequipment.Thebottleneckshereare:

1Limitedaccelerationandecelerationofrobots:

resultinginreducedspeed.

2Insufficientmeansofintegratingcomplexsensors:

ontheonehandbecauseofthelowreliabilityofthesesensors,andontheotherhandbecauseoftheclosenessofrobotcontrollers;auniversallanguageforroboticassemblysystemsandastandardinterfaceforrobotcontrollersare,unfortunately,notyetavailable.

3Limitedflexibilityofgrippersandotherassemblytools:

owingtotheproduct-dependenceoftheseassemblymeans,end-effectorchangeisingeneralrequired,forwhichonaverage30percentofthecycletimewillbeneeded[1].

4Limitedflexibilityoftheperipheralequipment:

thisisgenerallyseenasthemainbottleneck.Theperipheralequipmentisoftenproduct-dependent,whichaffectsthesystemflexibilitynegatively.Inthismanner,nojusticeisdonetothehighflexibilityoftherobot.

5Limitedreliabilityoftheperipheralequipmentandthelowaccessibilityofindividualsystemcomponents:

theseaspectsaregreatlyinfluencedbytheproductcomplexityandthesystemconfiguration[1].

Thesebottlenecksoftenresultinahighercapitalconsumption,andalongercycletimeoftheassemblysystem.Insufficientcoherenceandsynchronizationbetweenproduct,processandsystemdesignoftenlieatthebasisofthis.

Developmenttendencies

Inthepastyears,numerousDFAmethodshavebeendevelopedtooptimizeproductdesign,reducingthecomplexityoftheassemblyprocessandass