Fundamentals教學(xué)講解課件

Fundamentalsof

ManufacturingTechnologyFundamentalsof

Manufacturing1IntroductionWhatisManufacturingTechnologyItisdefinedthatthebasicsubjectsaremechanicalproducts,includingparts,componentsandmachines,emphasizingtheoperatingprocessesandmethodsinvolvedformachiningandassembly.SignificanceofMechanicalManufacturingAMachineIndustryandItsSignificanceBManufacturingTechnologyUnitedStates,WestEurope,Japan,ChinaCNationanddefencepower

PropertyandSubjectoftheCourseItisanveryimportantfundamentalcourseinSpecialtyofMechanicalEngineering；Examinedcompulsorycourse.IntroductionWhatisManufactur2ContentsandFeaturesoftheCourseMainContentsA)Preface:developmentofthesubject,procedureoftheproduction,patternandlocationofthecomponentinmachiningB)MachiningaccuracyandcontrollingC)MachinedsurfacequalityandstipulationD)PlanningofmechanicalprocessesE)DesignofassemblyprocessproceduresE)Designprinciplesandmethodsofjigs/fixturesformachinetoolsF)Trends&developmentsinmanufacturingtechnologyContentsandFeaturesoftheC3FeaturesA)Diversityofthecontents,Essentialofconcepts,DegreeofdifficultyB)Largelybasedonpractice——perceptualknowledgeandexperienceinworkshopC)Withengineeringcharacteristics——solutionsarenotnecessarilyuniqueD)Prerequisite/preconditionKnowledgeofMetaltechnology,Workshoppractice,Interchangeabilityandtechnicalgauging,metalcuttingprinciplesandcuttingtooldesigns,Machinetools,etc.FeaturesA)Diversityoftheco4TeachingmethodsandlearningrequirementsTeachingmethodsA)Trialonthecoursewithbilinguallanguages（English-Chinese)B)DetailedandbrieflecturingC)KeepbalancebetweenthetheoryandpracticeD)RemaintheequilibriumweightofthedailystudyandexaminationLearningrequirementsA)Comeandconcentrateonthecourse,takenotesfortheessentialandmostimportantpointsB)WorkoutassignmentsandhandtheminintimeC)Askquestionsifany,donotaccumulateproblemsTeachingmethodsandlearning5Assessmentofthecourse

Itwillbesoevaluatedasyourfinalscoresofthecoursethatthecentigradeisutilizedwiththreeaspects:a)pointsontheanswersheetoftheexamination,b)dailybehavior,coveringattendance,assignments,displayduringthelectures,c)pointsforexperiments.Eachofthesethreeaspectshastheweightof70%,20%and10%,respectivelywiththelimitationofatleast40%ofthecontentsaresupposedtoworkoutinEnglish.FortheencouragementofpracticingEnglish，compensationissosetthatupto8%extrapointswillbeobtainediftherestofthecontentshavebeendoneinEnglishproperly,penaltypointsofattheoutside5%willgooff,howeverkeepingthefullpointsof100.(本課程的考核采用百分制，考核內(nèi)容包括三部分：卷面成績、平時成績（出勤、作業(yè)、課堂表現(xiàn)）和實驗成績，分別以70%、20%和10%加權(quán)計入總成績；按量計，至少應(yīng)有40%的內(nèi)容用英文完成，如不能用英文完成，視情有不超過5%的減分；其余部分如用英文完成可獲上限為8%的加分，加分結(jié)果不能超過滿分成績。)Assessmentofthecourse6ContentChapterOneProductionprocedureandbasicnomenclatureChapterTwo

MachiningAccuracyandItsControlChapterThreeMachinedSurfaceQualityandControlChapterFourDesignofProcessPlanning

ChapterFiveDesignofAssemblyProcessingChapterSixDesignofFixturesofMachineToolsContent7ChapterOne:ProductionprocedureandbasicnomenclatureABasicconceptsProductionprocedureofmechanicalproductsProcessprocedureofmachiningBElementsofprocessprocedureofmachining1sequence工序；2installation安裝；3station工位；4step工步；5pass走刀ChapterOne:Productionproce8SequenceSequence:processprocedureconsistsofseveralsequencesduringwhichtheworkeroragroupofworkersoperateontheworkorasetoftheworkscontinuouslyinthesameplace.(操作者、加工地、工作對象——人為劃分，相對可變)SequenceSequence:processp9ExampleExample10InstallationInstallation:inasequenceiftheworkisrequiredtoputintopositionandclampseveraltimes,thepartofsequencedoneinonepositioningandclampingiscalledaninstallation.(確定)InstallationInstallation:ina11ExampleExample12StationStation:Inaninstallation,byusingtheindexingormovingdevicetheworkischangeditspositionrelativelytothecuttingtool.Allthetasksdonefortheworkinonemachiningpositioninaninstallationistermedasthestation.(確定)StationStation:Inaninstalla13ExampleExample14StepandpassStep：Inonestationifthesurfacecut,cuttingtool,velocity,andfeedremainunchanged,theseworkingcontentsarethoughtofasthestep.(加工表面、刀具、切削速度、進(jìn)給量任一改變均為另一工步）Pass:Whenthesurfaceoftheworkiscutforanyonetime,suchtaskcarriedoutisnamedasthepass.(刀具在加工表面的每一次切削）StepandpassStep：Inonestati15Asystemthatcontainstheworktobemachined,fixturethatholdstheworkintheproperposition,cuttingtoolthatmachinestheworkdirectly,andmachinetoolthatgivesthepowerandprovidethemovementstoaccomplishtheprocessing.Inrecentyearsthegaugingandmeasuringisaddedtothesystem.

Processingsystem:Asystemthatcontainsthewor16機(jī)械加工工藝過程的基本概念機(jī)械制造工藝：各種機(jī)械的制造方法和過程的總和。機(jī)械加工工藝過程：在機(jī)械加工車間中，直接改變生產(chǎn)對象的形狀、尺寸、相對位置與性質(zhì)等，使其成為成品或半成品的過程。機(jī)械加工工藝規(guī)程規(guī)定產(chǎn)品或零部件制造工藝過程和操作方法等的工藝文件。機(jī)械加工工藝過程的基本概念17工序是組成工藝過程的基本單元，是指一個（或一組）工人在一臺機(jī)床（或一個工作地點(diǎn)）對一個（或同時對幾個）工件進(jìn)行加工所連續(xù)完成的那一部分工藝過程。工序的主要依據(jù)是工作地點(diǎn)（或設(shè)備）是否變動，零件加工的工作地點(diǎn)變動后，即構(gòu)成另一工序。區(qū)分工序是組成工藝過程的基本單元，是指一個（或一組）工人在一臺18Step-shaftStep-shaft19Step-shaftStep-shaft20SequenceofoperationForsingleorsmallbatchproduction

Order1facing,centerdrillingcylindricalturning,groovingandchamferinglatheOrder2millingforroundedplainkey-seatsmillingmachineburringbench-workOrder3cylindricalgrindinggrinderForbatchorlotproductionOrder1facemilling,centerdrillingspecialmachineOrder2cylindricalturning,groovingandchamferinglatheOrder3millingforroundedplainkey-seatsmillingmachineOrder4burringbench-workOrder5cylindricalgrindinggrinderSequenceofoperationForsingl21PatternsofproductionaredeterminedbythebatchorlotRelationshipbetweenthebatchandthepatternofproductionN-programofproduction,Q-annualturnoutoftheproductn-numberofthecomponentsayear,-sharerate,-waste

rate,F-annual

working

days,A-numberofdaysforinventory,-numberofcomponentsinalotPatternsofproductionaredet22ItmaybeunderstoodlikethisThenumberofannualworkingdaysdividedbythenumberofthedaysspendingonthebatchofproduction(inventorydays)istheaveragenumberofbatchedperyear;andtheannualprogramdividedbythelatternumberistheamountoftheproductsinabatch.Itmaybeunderstoodlikethis23Oritmaybeknowninthefollowingway.Oritmaybeknowninthefoll24ProgramandBatchofproductionAProgramofproductionInaperiodofplanning,theturnoutofproductandscheduletobefulfillediscalledprogram.(計劃期的產(chǎn)量加進(jìn)度=生產(chǎn)綱領(lǐng)）Theturnoutinoneyearplanningisnamedtheannualprogram.BBatchofproductionAtatime,thenumberofidenticalproductstobeputintoproductionortobeproducedistermedasbatchofproduction.(一次投入生產(chǎn)的同一產(chǎn)品的數(shù)量=生產(chǎn)批量）ProgramandBatchofproductio25Table1-5Technologicalfeaturesinvariousproductionstyles/patternsstylecontentSingle/SmallbatchMedialbatchLargebatch/MassproductionProduct/workBlank/allowanceMachine/layoutFixtureTool/gaugeInstallationofworkAssemblingmethodLaborskillProductivityCostTechnologicaldocument/filefrequentchangeManualmold,freeforgeLowaccuracy,largemarginAll-purpose,ingroupuniversal/compositeSpecialifneededUniversalscoring/universal/specialfixtureifneededscrapinghighlowhighSimpleproceduresheetCyclicchangePartdie,,middleaccuracy/marginPartall-purpose,partspecialPipeline/ingroupWideuseofspecial/adjustablePartuniversal,partspecialPartuseofscoring/universal/specialfixtureAlittlescraping,interchangeMediocreMediocreMediocreSequencesheet,regulationNochangeWideuseofdie,dropforge,highaccuracy,lowmarginWideuseofspecial-purpose,Pipeline/automaticlineWideuseofefficient,specialWideuseofefficient,specialSpecial-purposeInterchangeLowHighlowDetailedregulation,sequence,operating,adjustingsheetTable1-5Technologicalfeature26Noticeshouldbepaidattentionto

Withthedevelopmentofthetechnologyandthediversityofthemarket,allthepatternsofproduction,inthatconventionalmassproductioncanhardlykeeppacetotherapidchangeofproductsandsinglepieceorsmallbatchproductionmayscarcelymeettheneedsofmassivedemand,essentiallyareheadingtoflexibleproduction.Noticeshouldbepaidattentio27FunctionofprocessplanningmechanicalmachiningAthebaseonwhichtheplan,dispatch,operationoftheworkersandqualitymeasuringarecarriedout.Actionpertainingtothemanagementistakenaccordingtotheprocesspanning.BThisdocumentisadoptedforthepreparationofproduction,suchasthecoretechniquesanalysis,designorpurchaseofcuttingtools,fixtures,andgauges,preparationofrawmaterials,blanks,tooling.CForbatchormassproduction,theworkshopandfactorywillbebuiltorenlargedrelyingupontheprocessplanning.Thetypesandnumberofmachinetools,thelayoutandenergyforthesemachinetool,theplacethemachinetoolstakeupandoperatorsarealldeterminedwiththeprocessplanning.Functionofprocessplanningm28Processplanningformachiningoperations

:

stipulateddocumentfortechnologicalprocess(機(jī)械加工工藝規(guī)程：以工藝文件形式規(guī)定的機(jī)械加工工藝過程)

PatternsoftheprocessplanningformachiningGenerallyspeaking,theprocessplanningformachiningappearsintheformofsheetorcardwiththesamebasiccontentinthreepatterns:PatternA:sheetofprocessprocedures(工藝過程卡),averysimpleandconcisedocument,usuallyforsingle/smallbatchproductionPatternB:sheetofprocessoperation(機(jī)械加工工藝卡),oftenforbatchproductionPatternC:sheetofprocesssequence(機(jī)械加工工序卡),withdetailedandcompletecontents,frequentlyformassiveproductionProcessplanningformachining29Rules,stepsandcontentsofprocessplanningformachiningRules:1Guarantee/safeguardtherealizationofallthetechnicalrequirementsforthedesignedcomponentinthemachinedrawing.2Pursuethelowestcostinmachiningprocessesundertheproductionprogramandtheproductionbatch,ifpossible.3Makefulluseofthepresentproductionconditionsavailable.4Improvetheconditionsandenvironmentunderwhichworkersoperate,withsafety,comfort,andwithlowworkinghardness/severity

Rules,stepsandcontentsofp30Stepsandcontentsofprocessplanningformachining:

1)Readandlearntheassemblydrawingsandcomponentdrawings（裝配圖和零件圖）.2)Inspectorinsightintoorchecktheprocesses(technologicalmanufacturability)used,suchasthecompleteness,correctness,andcoherenceofthesize,viewing,technicalconditionsonthedrawings,aswellasthestructuralmanufacturabilityofthecomponents（零件的結(jié)構(gòu)工藝性）（underthepresentprocessconditions，beingeasyinmachiningwithlowercostwhilereachingthestandardrequired)3)Makeknownandsizeuptheblank/stock（毛坯）4)Designtheroutesofmachiningprocesses（工藝路線）5)Choosethepropermachinetoolsandtoolingforeachsequence6)Decidethetechnologicalrequirements/conditions（技術(shù)要求）andgaugingmethods（測量方法）

forthemainsequences.7)Setupthemachiningallowance（余量margin）,sequentialsize(工序尺寸）,andtolerance

（公差）oftheworkpieceforeverysequenceofoperation.8)Setupthemachiningengagement（切削用量）.9)Determinethetimerate(時間定額）.10)Fillinthetechnologicaldocument（工藝文件）.Stepsandcontentsofprocess31SectionTwo:LocationandDatumoftheworkinmachiningKeypoints:ConceptsofLocating,Clamping,datums;WaysofpositioningPrincipleofLocatingAThelocationoftheworkInstallationandclamping(裝夾）:concerningaboutthewaysinwhichtheworkisinstalledandclampedinthefixtureoronthemachinetool,includingtwoaspects,locating(定位)andclamping(夾緊).SectionTwo:LocationandDatu32locatingLocating:theprocedureduringwhichtheworkgainsitsproperpositioninthefixtureoronthemachinetool.Clamping:whentheworkpiecehasgaineditscorrectpositioninthefixture,itwillbesubjecttotheexternalforceswhilebeingmachined.So,toholdorkeeptheworkpieceinthecorrectpositionisdefinitelyrequired,whichiscalledclamping.locatingLocating:theprocedur33BasicmethodsoflocationandclampingoftheworkpieceinmachiningIdirectcorrecting(直接找正裝夾)——single/smallbatchproduction,andinhighquality.IIlining/scrapingandcorrecting(劃線找正裝夾)——smallbatchandmedium-sizedbatch,complicatedcastings,androughcastings.IIIlocatingandclampingwithjigs/fixtures(夾具裝夾)——usuallyforallkindsofpatternsofproduction,becauseofthesimpleoperation,easyreachofthequality,andhighproductivity.Basicmethodsoflocationand34BSix-PointLocatingPrinciplesBSix-PointLocatingPrinciple35Acuboidisincartesiancoordinatesystemwithsixdegreesoffreedom

Thesixdegreesoffreedomarethreelinearmovementsalongthethreecoordinateaxes,respectively,andthreerotationsaroundthesecoordinateaxesAcuboidisincartesiancoord36CLocatingelementsandtheirfunctionsIntheory,thelocatingpointisthegeometricpoint;inreality,itissomethingdifferentwithitsthreedimensions.Thefollowingarecommonlyusedinworkshops.Buttonlocator(支撐釘)Plug(檔銷)Supportingplate（支撐板）

Pin/pinlocator（長銷）CLocatingelementsandtheir37LocatingelementsandtheirfunctionsButtonCutpin/rhombuspin（削邊銷/菱形銷）Mandrel（心軸）Vblock（形塊）ShortVblock（短形塊）Positioningsleeve（定位套）Fixed/floatingconicpin（固定/浮動錐銷）Center(頂尖（固定/浮動）)Locatingelementsandtheirfun38Complete/incompletelocatingCompletepositioning:locatingwithconstraintforallsixdegreesoffreedom.Incompletepositioning:locatingwithconstraintforlessthansixdegreesoffreedom.Under/over-positioning:thenumberofconstraintsofdegreeoffreedomislessthanthatrequired.Under-positioningoughttobeavoidedand,thesamedegreeoffreedomisconstrainedbytwoorevenmoreconstrainingpoints,suchsituationiscalledover–positioning,whichwillbeallowedoccasionally.Complete/incompletelocating39Summaryfortheworklocation1)Analyzehowmanydegreesoffreedomshouldbeconstrainedforthesurfaceoftheworktomachine.2)Fromtheviewpointofbeingsubjecttothecuttingforces,usingtheclampingdevices,andenhancingtheproductivity,ofthecomponent,whetheradditionalconstraintsareneededinincompletelocation.3)Ifthereisunder/over-locating,andsuchover-locationisallowedornot.Summaryfortheworklocation140UnderstandingthelocatingandconstrainingDirect

view:eachofthesixpointsofthelocatingelementstouchesandkeepsthetouchingofthesurfaceoftheworkpiecewithacertaincontactarea(whichmaybeextendedininfinity),boththepointandthetouchedsurfaceisrigid.Backwardview:ifthesurfaceoftheworkgoesawayfromthelocatingelement,thatistoseparatefromtheelement,itisnolocatingatall.Understandingthelocatingand41Thelocatingelements:buttonlocatorThelocatingelements:button42Buttonandpin/longpinButtonandpin/longpin43Rhombuspin,locatingcombination:longpinwithsmallshoulder,andbuttonwithlargeshoulderRhombuspin,locatingcombinat44Fixedconicpinandfloating

conicpinFixedconicpinandfloating

45Mandrel,long,short,andwithslighttaperMandrel,long,short,andwith46Vblock，Withnarrowedone,twonarrowedpieces,andwideoneVblock，Withnarrowedone,two47Locatingsleeve,withnarrowedone,withtwonarrowedpieces,andwithwideoneLocatingsleeve,withnarrowed48Center,floatingcenter,andtaperedmandrelCenter,floatingcenter,andt49Completepositioning,Incompletepositioning,Completepositioning,Incomple50Under/overpositioningUnder/overpositioning51Over-positioningOver-positioning52DDatumNotion:datumisthepoint,lineorsurfacebasedonwhichthegeometricrelation-shipsamonggeometricelementsoftheobjecttobeworkedataredetermined.Theconceptissoimportantthatismaybeusedforanyaspectofproduction,fromdesign,throughmanufacturingincludingsequencesofoperation,tothegaugingandassembly.DDatumNotion:datumi53datumDatummaybeclassifiedintotwocategories,DesigndatumandTechnologicaldatum,accordingtotheirfunctions.Idesigndatum:indesignofcomponents,theoriginfromwhich,accordingtotheassemblyrelationshipofthecomponentandtherelativerelationshipofthestructuralelementsofthecomponentitself,thedimensioningisdone.Theseoriginalpositionsfordimensioningarecalleddesigndatums.(設(shè)計圖紙上零件標(biāo)注的起始位置)IItechnologicaldatum:datumusedintheprocessoperationsistermedtechnologicaldatum,whichcanbeevenclassifiedas:datumDatummaybeclassifiedi54ExampleofdesigndatumExampleofdesigndatum55Technological/processdatumsSequentialdatum:

onthesequentialdrawing,datumthatisusedinthissequencetodeterminethesize,form,andpositionoftheworkafterbeingmachinedisnamedSequentialdatum.Thethreeaspectsaresupposedtobetakenintoconsideration:thepriorityofsequentialdatumispaidtothedesigndatum,thatisusethedesigndatumassequentialdatum,theselecteddatumisfavorableforthelocationandthegaugingofthework,andiftheaboverequirementsarehardlymet,thedatumoughttobeusedtoguaranteethetechnicalconditions.Technological/processdatumsSe56Locating,gauging,andassemblingdatums

Locatingdatum:datumusedfortheworkpiecetogainitsproperpositioninmachining,itdirectlyinfluencestheeffectivenessofmachining.LocatingdatumcoversRoughdatumandFinishingdatum.a)Roughdatum/Finishingdatum:un-machinedlocatingdatum,inotherword,anylocatingdatumusedinthefirstsequenceofoperationinthemanufacturingprocessplanningistheroughdatum;finishingdatum:machinedlocatingdatum.b)additional/auxiliarydatum:thespeciallydesigneddatumintheworkpiecebecauseoftherequirementofthemechanicalprocessoperations.Locating,gauging,andassembli57GaugingandassemblingdatumsGaugingdatum:duringandaftermachining,datumusedformeasuringandcheckingtheform,position,anderrorofsize,oftheworkpiece.Assemblingdatum:inassemblingdatumadoptedtodeterminetherelativepositionsoftheworkorthecomponentintheproduct.GaugingandassemblingdatumsG58MeasuringdatumMeasuringdatum59AssemblingdatumAssemblingdatum60Sectionthree:Designtheroutesofmachiningprocesses（工藝路線的制定）Considerationmustbetakenwiththelocatingdatumoftheworkpiece(定位基準(zhǔn)）,theprocessmethods（加工方法）,theorderoftheprocesses（加工順序）,heattreatment（熱處理）,testing（檢驗），andtherelatedoperations（其他工序）.Aselectionoflocatingdatums(定位基準(zhǔn)的選擇)Bselectionofeconomicaccuracyandprocessmethodsofmachining（機(jī)加的經(jīng)濟(jì)精度與方法）Cmachiningroutesforthetypicalsurfaces（典型表面的加工路線——外圓、孔和平面）Dorderofsequences（工序順序安排）Sectionthree:Designtherout61Fromtheexampleaboveitisknownthattheselectionoftheroughdatummayinfluencetherelationshipbetweenthemachinedandun-machinedsurfacesaswellastheallocationoftheallowance.Inaddition,theinitialroughmachiningmustencountersuchtask.Soitisinevitableandsignificanttoselecttheproperroughdatum.

Selectingrules:Iguaranteetheproperrelativepositions.IIguaranteereasonableallocationoftheallowanceforthesurfacebeingmachined.IIIfacilitatethelocatingandclampingoftheworkpiece.Forthisreason,theselectedsurfacesasthedatumsmustbetosomeextentsmooth,enough-sized,flasher-free,withoutotherdefectssuchasreservoirandriserorthelike.IVtheroughlocatingdatumusedonlyforonetime(withoutrepetition)Fromtheexampleaboveitisk62SelectionofroughdatumSelectionofroughdatum63Aselectionofroughdatum(粗基準(zhǔn)的選擇)

Aselectionofroughdatum(粗基64Non-repetitionofroughdatuminuseNon-repetitionofroughdatum65Selectionofthefinishingdatum

Forselectingthefinishingdatum,themainconcernishowtomeetthetechnicalconditionsandguaranteetheproperinstallation,reliabilityandconvenienceintheinstallation

Selectingrules:Ioverlappingprinciple(基準(zhǔn)重合）-datumusedasthesameasdesigndatumIIunifyingprinciple（基準(zhǔn)統(tǒng)一）-usethesamedatumasearlyandasfrequentlyaspossibleIIIinter-referenceprinciple（互為基準(zhǔn)）-especiallyusedforthehighaccuracyofrelativepositionsofthesurfacesIVself-referenceprinciple（自為基準(zhǔn))-forsequenceofsmallroughness,smallandevenallowanceVclamping-facilitating/convenientprinciple（便于裝夾）-forproperandsecure(reliable)locating,simplestructureoftheclampingdevicewitheasyoperationSelectionofthefinishingdat66Theprocessrouteandconversionofthebox-likecomponentinunificationofdatums

SequenceofFaceSideUndersideUpperPinholeLongitudinalholeTransverseholeHolesforfasteningoperationsurface

0Ra50μm1Roughandsemi-finishingUppersurfaceRa3.2μm2DrillthepinholesandholesforfasteningontheupperRa3.2μm3SideandundersideRa3.2μmRa3.2μm4faceRa3.2μm5FinishingundersideRa1.6μm6FinishinguppersurfaceRa1.6μm7RoughmachiningLholeRa12.5μm8Semi-finishingLholeRa6.3μm9finishingLholeRa3.2μm10TransverseholeAndholeforfasteningRa6.3μm11MachiningotherholesforfasteningRa6.3μmTheprocessrouteandconversi67box-likecomponentbox-likecomponent68Bselectionofeconomicaccuracyandprocessmethodsofmachining（機(jī)加的經(jīng)濟(jì)精度與方法）

Notion:economicaccuracyinmachiningUnderthecommonmachiningconditions,thatis,withfacilitiesandtoolinginstandardquality,theoperatorswithtypicalskills,andinratedtime,themachiningisdonewiththerelevantaccuracyandroughnessimpartedtothecomponent.SuchaccuracyandroughnessiscalledtheeconomicaccuracyinmachiningBselectionofeconomicaccura69Machiningerrorvscost,andthetrendofmachiningaccuracyMachiningerrorvscost,andt70Cmachiningroutesforthetypicalsurfaces（典型表面的加工路線——外圓、孔和平面）CylinderHoleFlat/plane/surfaceCmachiningroutesforthetyp71Dorderofsequences（工序順序安排）

Dorderofsequences（工序順序安排）

72Sectionthree:determinationofmachiningallowance,dimensionsbetweensequences,andtolerancemachiningallowance:thedifferencebetweenthesizeoftheblankandthatofthecomponentdesignondrawing

thetotalallowanceisequaltothesumofmaterialthicknesstoberemovedforeverystepintheprocessoperation.Sequentialallowance:thethicknessofmetalremovalofthecutlayerineverysequenceTherelationshipbetweenthetotalallowanceandSequentialallowancewillbeexpressedintermsof

Zo=Z1+Z2+…+Zn=Sectionthree:determinationo73

whereZoisthetotalmachiningallowance,

Ziisasequentialallowanceand

nisthenumberofthesequencesforacomponent.sequentialallowancecanalsobedefinedasthedifferencebetweenthetwoadjacentlynominalsequentialsizes.Fromthislightofstatement,sequentialallowancecanbeclassifiedsinglesideallowanceforasymmetricworkandbilateral/doublesideallowanceforsymmetricwork,respectively.TheyareexpressedintermsofZi=li-1-liAnd

2Zi=li-1-liWhere

Ziisthecurrentsequentialallowanceli-1isthelastprevioussequentialnominalsizeliisthecurrentsequentialnominalsize

whereZoisthetotalmachini74Single-side,bilateral/double-sideallowanceSingle-side,bilateral/double-75NotionofenvelopingobjectorenvelopedobjectfordimensioningSituation:thereisapairofmatingparts(配合運(yùn)動副，如一對齒輪嚙合，活動鉸鏈),oneofwhichwithitsexternal/opensurfacefitsanotherpart,theformeroneiscalledenvelopedobjectthatiscoveredbythelatterpart,andthelatteroneiscalledenvelopingobject.ExamplesaredepictedbelowNotionofenvelopingobjector76envelopingobjectorenvelopedobjectfordimensioningenvelopingobjectorenveloped77Sequentialallowance,entering-objectdimensioning(入體方向標(biāo)注)Sequentialallowance,entering78entering-objectdimensioningDiameterofHoles,widthofkeyseatsetc.arethenominaldimensionwiththeirsmallestsize;Diameterofshaft,widthofkeysetc.arethenominaldimensionwit