外文翻译--计算机辅助工艺过程设计.doc

Computer-AidedProcessPlanningAccordingtotheTool&ManufacturingEngineersHandbook,processplanningisthesystematicdeterminationofthemethodsbywhichaproductistobemanufacturedeconomicallyandcompetitively.Itessentiallyinvolvesselection,calculation,anddocumentation.Processes,machines,tools,operations,andsequencesmustbeselected.Suchfactorsasfeeds,speeds,tolerances,dimensions,andcostsmustbecalculated.Finally,documentsintheformofillustratedprocesssheets,operationsheets,andprocessroutesmustbeprepared.Processplanningisanintermediatestagebetweendesigningandmanufacturingtheproduct.Buthowwelldoesitbridgedesignandmanufacturing?Mostmanufacturingengineerswouldagreethat,iftendifferentplannerswereaskedtodevelopaprocessplanforthesamepart,theywouldprobablycomeupwithtendifferentplans.Obviously,alltheseplanscannotreflectthemostefficientmanufacturingmethods,and,infact,thereisnoguaranteethatanyoneofthemwillconstitutetheoptimummethodformanufacturingthepart.Whatmaybeevenmoredisturbingisthataprocessplandevelopedforapartduringacurrentmanufacturingprogrammaybequitedifferentfromtheplandevelopedforthesameorsimilarpartduringapreviousmanufacturingprogramanditmayneverbeusedagainforthesameorsimilarpart.Thatrepresentsalotofwastedeffortandproducesagreatmanyinconsistenciesinrouting,tooling,laborrequirements,costing,andpossiblyevenpurchaserequirements.Ofcourse,processplansshouldnotnecessarilyremainstatic.Aslotsizeschangeandnewtechnology,equipment,andprocessesbecomeavailable,themosteffectivewaytomanufactureaparticularpartalsochanges,andthosechangesshouldbereflectedincurrentprocessplansreleasedtotheshop.Aplannermustmanageandretrieveagreatdealofdataandmanydocuments，includingestablishedstandards，machinabilitydata，machinespecifications，toolinginventories，stockavailability，andexistingprocessplansThisisprimarilyaninformationhandlingjob，andthecomputerisanidealcompanionThereisanotheradvantagetousingcomputerstohelpwithprocessplanningBecausethetaskinvolvesmanyinterrelatedactivities，determiningtheoptimumplanrequiresmanyiterations.Sincecomputerscanreadilyperformvastnumbersofcomparisons，manymorealternativeplanscanbeexploredthanwouldbepossiblemanuallyAthirdadvantageintheuseofcomputer-aidedprocessplanningisuniformity.SeveralspecificbenefitsCanbeexpectedfromtheadoptionofcomputer-aidedprocessplanningtechniques：1Reducedclericaleffortinpreparationofinstructions2Fewercalculationerrorsduetohumanerror3.Feweroversightsinlogicorinstructionsbecauseofthepromptingcapabilityavailablewithinteractivecomputerprograms4Immediateaccesstouptodateinformationfromacentraldatabase5Consistentinformation，becauseeveryplanneraccessesthesamedatabase6.Fasterresponsetochangesrequestedbyengineersofotheroperatingdepartments7AutomaticUseofthelatestrevisionofapartdrawing8.Moredetailed，moreuniformprocess-planstatementsproducedbywordprocessingtechniques.9Moreeffectiveuseofinventoriesoftools，gages，andfixturesandaconcomitantreductioninthevarietyofthoseitems.10.Bettercommunicationwithshoppersonnelbecauseplanscanbemorespecificallytailoredtoaparticulartaskandpresentedinunambiguous，provenlanguage.11.Betterinformationforproductionplanning,includingcutter-life,forecasting,materials-requirementsplanning,scheduling,andinventorycontrol.MostimportantforCIM,computer-aidedprocessplanningproducesmachine-readabledatainsteadofhandwrittenplans.SuchdatacanreadilybetransferredtoothersystemswithintheC1Mhierarchyforuseinplanning.Therearebasicallytwoapproachestocomputer-aidedprocessplanning:variantandgenerative.Inthevariantapproach,asetofstandardprocessplansisestablishedforallthepartsfamiliesthathavebeenidentifiedthroughgrouptechnology.Thestandardplansarestoredincomputermemoryandretrievedfornewpartsaccordingtotheirfamilyidentification.Again,GThelpstoplacethenewpartinanappropriatefamily.Thestandardplanistheneditedtosuitthespecificrequirementsofaparticularjob.Inthegenerativeapproach,anattemptismadetosynthesizeeachindividualplanusingappropriatealgorithmsthatdefinethevarioustechnologicaldecisionsthatmustbemadeinthecourseofmanufacturing.Inatrulygenerativeprocess-planningsystem,thesequenceofoperations,aswellasallthemanufacturing-processparameters,wouldbeautomaticallyestablishedwithoutreferencetopriorplans.Initsultimaterealization,suchanapproachwouldbeuniversallyapplicable:presentanyplantothesystem,andthecomputerproducestheoptimumprocessplan.Nosuchsystemexists,however.Socalledgenerativeprocess-planningsystems-andprobablyfortheforeseeablefuture-arestillspecializedsystemsdevelopedforaspecificoperationoraparticulartypeofmanufacturingprocess.Thelogicisbasedonacombinationofpastpracticeandbasictechnology.计算机辅助工艺过程设计根据工具与制造工程师手册，工艺过程是能够经济地和有竞争力地将产品制造出来的一整套方法。它主要由选择、计算和建立工艺文件组成。对加工方法、机床、刀具、工序和顺序必须进行选择。对于一些参数如进给量、速度、公差、尺寸和成本等应该进行计算。最后，应该制订带工序简图的工艺过程卡片，工序卡片和工艺路线等方面的工艺文件。工艺过程是产品设计和制造的中间环节。那么，它是如何将设计与制造联接起来的呢?大部分制造工程师都会同意这个看法，即如果10个不同的工艺人员编制同一个零件的工艺规程，他们很可能得出10种不同的方案。显然，并不是所有这些方案都能反映最适当的制造方法，而且，事实上也不能保证它们中的任何一个方案是由加工这个零件的最好的方法组成的。在目前的制造过程中的一个更为混乱的事情是，对于一个零件来说，现在所编制的工艺规程可能与以前在制造过程中所编制的同一个零件或者相似零件的工艺规程相差很多，而且这个工艺规程可能再也不会应用于同一个零件或者相似零件。这说明很多工作成果都被浪费了，而且在工艺路线、工艺装备、对工人的要求和成本等方面都不一致，甚至对外购件的要求都不一样。当然工艺规程不应该是一成不变的。随着产品批量的变化和新技术、新设备、新的加工方法的出现，加工制造某一特定零件最适当的方法也会发生变化，而且这些变化应该在车间目前使用的加工工艺规程中反映出来。工艺人员应该管理和检索大量的数据和很多文件，其中包括：已经建立了的标准、可加工性数据、机器的规格、工艺装备的清单、原材料库存量和一些目前正在应用的工艺文件。这主要是一些信息处理工作，而计算机是完成这项工作的一个理想助手。在设计工艺过程时应用计算机还有一个优点。因为这项工作涉及到许多相互关联的事情，在确定最优的方案时，需要进行许多次迭代。由于计算机可以很容易地进行大量的比较工作，它比人工所能够分析的可供选择的方案要多得多。采用计算机辅助工艺过程设计的第三个优点是所设计的工艺过程具有一致性。采用计算机辅助工艺过程设计可以获得以下几点好处：1.在准备工艺文件时，减少了书写工作量。2.减少了在进行人工计算时所产生的错误。3.由于交互式计算机程序的提示功能而减少了在逻辑和说明方面的疏漏4.通过中央数据库可以直接利用最新的信息.5.由于每一个工艺人员都利用相同的数据库，因此，可以保证信息的一致