unit13夹具与固定装置

ProfessionalEnglish（13）

北华大学机械学院王开宝Unit13JigsandFixture

钻模与夹具

Introduction导言Ithasalreadybeenstatedthattheworkpiecemustbelocatedrelativetothecuttingtool,andbesecuredinthatposition.Aftertheworkpiecehasbeenmarkedout,itisstillnecessarytopositionitwithrespecttothemachinemovements,andtoclampitinthatpositionbeforemachiningisstarted.已经说明了工件必须相对于切削刀具定位并确保到位。工件划线后，仍有必要将其相对于切削运动定位，并在机加工开始前把它装夹到位。

Whenseveralidenticalworkpiecesaretobeproducedtheneedtomarkouteachpartiseliminatedbytheuseofjigsandfixtures,butifacastingorforgingisinvolved,atrialworkpieceismarkedout,toensurethattheworkpiececanbeproducedfromit,andtoensurethatribs,cores,etc.havenotbecomemisplaced.

当要加工若干同样的工件时，使用钻模和夹具可以不必在每个工件上划线；但对铸件或锻件而言，还需取一试验工件划线以保证照此加工不会将加强肋、型芯等放错位置。Jigsandfixturesarealikeinthattheybothincorporatedevicestoensurethattheworkpieceiscorrectlylocatedandclamped,buttheydifferinthatjigsincorporatemeansoftoolguidingduringtheactualcuttingoperation,andfixturesdonot.钻模和夹具的相似点是它们都把保证工件正确定位和夹紧的装置相结合，它们的不同在于钻模在实际切削作业中还能与刀具导向方法相结合，而夹具则不能。Inpractice,theonlycuttingtoolsthatcanbeguidedwhileactuallycuttingaredrills,reamers,andsimilarcutters;andsojigsareassociatedwithdrillingoperations,andfixtureswithallotheroperations.Fixturesmayincorporatemeansofsettingthecuttingtoolsrelativetothelocationsystem.实际上，在真实切削中能被导向的切削刀具只有钻头、铰刀和类似的刀具；因此钻模用于钻削作业，而夹具用于其余作业。夹具可以与切削刀具相对定位系统装夹的方法结合在一起。Theadvantagesofjigsandfixturescanbesummarisedasfollows:1)Markingoutandothermeasuringandsettingoutmethodsareeliminated;钻模和夹具的优点可归纳如下：1)可以省去划线和其它测量及放样程序；2)Unskilledworkersmayproceedconfidentlyandquicklyinknowledgethattheworkpiececanbepositionedcorrectly,andthetoolsguidedorset;2)在知道工件能正确定位、刀具能恰当导向或装夹的情况下，不熟练的工人也能自信而快速地操作；Boltholesoftenhave1.5mmoreven3.0mmclearanceforthebolt,andthereadermaydoubtthenecessityofmakingprecisionjigsforsuchwork.Itmustberememberedthatthejigs,oncemade,willbeusedonmanycomponents,andtheextracostofanaccuratelymadejigisspreadoveralargeoutput.螺栓孔常给螺栓留出1.5毫米或甚至3.0毫米的间隙，读者可能会怀疑为这样的工作制造精密钻模的必要性。但要记住，这种钻模一旦造好，可用于许多零部件，精确制造钻模的额外成本可分摊在大量产品上。Furthermore,itissurprisinghowsmallerrorsaccumulateinamechanismduringitsassembly.Whenaclearanceisspecified,itisbettertoensureitsobservance,ratherthantoallowcarelessmarkingoutandmachiningtoencroachuponit．此外，这样做在装配机械装置时其累积误差之小也是令人惊讶的。在确定一个间隙时，最好能保证它的习惯要求，而不是随便划线和机加工使其超出正常的界限。1)Thelocationofworkpiece.Fig.13.1representsabodythatiscompletelyfreeinspace.Inthisconditionithassixdegreesoffreedom.ConsiderthesefreedomswithrespecttothethreemutuallyperpendicularaxesXX,YY,andZZ.1)工件的定位：图13.1表示一个在空间完全自由的物体，在这种情况下它具有六个自由度。相对于三根互相垂直的坐标轴XX、YY和ZZ来考虑这些自由度。Thebodycanmovealonganyoftheseaxes;itthereforehasthreefreedomsoftranslation.Itcanalsorotateaboutanyofthethreeaxes;itthereforehasthreefreedomsofrotation.Thetotalnumberoffreedomsissix.Whenworkislocated,asmanyofthesefreedomsaspossiblemustbeeliminated,toensurethattheoperationisperformedwiththerequiredaccuracy.此物体能沿三根坐标轴的任意一根移动；这样就具有三个平移自由度。它也能围绕三根坐标轴的任意一根回转；这样它又具有三个旋转自由度。总的自由度数目是六个。当工件被定位时，必须尽可能多地消除这些自由度，以保证作业按要求精度进行。Accuracyisensuredbymachiningsuitablelocationfeaturesasearlyaspossible,andusingthemforalllocation,unlessotherconsiderationsmeanthatotherlocationfeaturesmustbeused.Ifitisnecessary,thenewlocationfeaturesmustbemachinedasaresultoflocationfromtheformerlocationfeatures.除非有必要采用另外定位要素的其它考虑，精度可通过尽可能早地加工合适的定位要素并采用它们进行所有定位来保证。如果必要的话，新的定位要素必须作为先前的定位要素的定位结果来加工。2)Theclampingoftheworkpiece.Theclampingsystemmustbesuchthattheworkpieceisheldagainstthecuttingforces,andtheclampingforcesmustnotbesogreatastocausetheworkpiecetobecomedistortedordamaged.2)工件的装夹：装夹系统必须使工件对着切削力夹持，而且装夹力又不能大得引起工件变形或损坏。Theworkpiecemustbesupportedbeneaththepointofclamping,toensurethattheforcesaretakenbythemainframeofthejigorfixture,andontothemachinetableandbed.Whenjigsandfixturesaredesigned,theclampingsystemisdesignedtoensurethatthecorrectclampingforceisapplied,andthattheclampscanbeoperatedquicklybutwithsafety.工件必须在装夹点下被支撑，以保证这些力由钻模或夹具的主框架来承受并传递给机器台和床身。在设计钻模和夹具时，要同时设计装夹系统来保证提供恰当的装夹力，并使装夹操作快速而安全。DefinitionofaDrillJig

钻模的定义Adrilljigisadeviceforensuringthataholetobedrilled,tapped,orreamedinaworkpiecewillbemachinedintheproperplace.钻模是一种确保在工件正确位置进行钻孔、攻丝或铰孔加工的装置。Basicallyitconsistsofaclampingdevicetoholdthepartinpositionunderhardened-steelbushingsthroughwhichthedrillpassesduringthedrillingoperation.Thedrillisguidedbythebushings.它基本上由在淬硬钢衬套下将零件夹持到位的夹持装置组成，钻孔作业中钻头穿过这些衬套，通过它们来导向。Iftheworkpieceisofsimpleconstruction,thejigmaybeclampedontheworkpiece.Inmostcases,however,theworkpieceisheldbythejig,andthejigisarrangedsothattheworkpiececanbequicklyinsertedandasquicklyremovedafterthemachiningoperationisperformed.如果工件结构比较简单，钻模可夹持在工件上。然而大多数情况下，工件由钻模来夹持，并且把钻模设计成能将工件迅速装入而在加工后同样能很快取出。Jigsmakeitpossibletodrill,ream,andtapholesatmuchgreaterspeedsandwithgreateraccuracythanwhentheholesareproducedbyconventionalhandmethods.Anotheradvantageisthatskilledworkersarenotrequiredwhenjigsareused.Responsibilityfortheaccuracyofholelocationistakenfromtheoperatorandgiventothejig.相对于用常规的手工方法加工孔，钻模使得钻孔、铰孔和攻丝速度快很多而且精度更高成为可能。另一个优点是采用钻模时不需要熟练工人。保证孔定位精度的责任从操作者身上转移到了钻模上。Thetermjigshouldbeusedonlyfordevicesemployedwhiledrilling,reaming,ortappingholes.Itisnotfastenedtothemachineonwhichitisusedandmaybemovedaroundonthetableofthedrillingmachinetobringeachbushingdirectlyunderthedrill.Jigsphysicallylimitandcontrolthepathofthecuttingtool.钻模这个术语只用在服务于钻孔、铰孔或攻丝的装置上。它不固定在使用它的钻床上，它能在钻床工作台上到处移动以使每个衬套都直接位于钻头下。钻模有形地限制和控制钻削刀具的路径。Iftheoperationincludesmachiningoperationslikemilling,planing,shaping,turning,etc.,thetermfixtureshouldbeused.Afixtureholdstheworkduringmachiningoperationsbutdoesnotcontainspecialarrangementsforguidingthecuttingtool,asdrilljigsdo.如果作业还包括其它象铣削、刨削、成型、车削等机加工，则应采用夹具这一术语。夹具在机加工作业时夹持工件，但它不象钻模那样包含引导切削刀具的特殊布置。TypicalJigsandFixtures

典型的钻模和夹具Typicaldrilljig.Figure13.2illustratesadrillingjigfordrillingfourholesintheflangeofaworkpiecethathasbeencompletedexceptforthefourholes.典型的钻模：图13.2所示为一个能在某工件的法兰上钻四个孔的钻模，该工件除了这四个孔外已全部完成。Theworkpiecehasanaccuratelymachinedbore,andislocatedfromtheboreandtheendface,fromacylindricalpost.Thereisnoneedtocontroltherotationalpositionabouttheaxisofthebore,becauseuptothetimewhentheholesaredrilled,itissymmetricalaboutthataxis.此工件有一精确机加工的大孔，因此通过一圆柱体采用该孔和工件端面定位。由于直至钻这些小孔时，工件都对称于大孔轴线，所以没必要控制围绕大孔轴线回转的位置。Thefourbushesusedtocontrolthedrillareheldinthedrillplate,which,withthehandnut,isusedtoclamptheworkpieceagainstthebaseofthefixture.四个控制钻头的衬套装在钻板里，连同手拧螺母一起用于靠着夹具基座夹持工件。Typicalmillingfixture.Figure13.3illustratesasimplemillingfixtureformillingtheslotintheotherwisecompletedworkpieceshown.Theworkpieceislocatedfromtwoofthefourholesinitsbase,andfromtheundersideofthebase.典型的铣削夹具：图13.3所示为一用于在图示其它工序都完成的工件上铣槽的简单铣削夹具。此工件采用其基座上四孔中的两孔和基座的底面定位。Theworkpieceisclampedinposition,andcutterislocatedagainstthesettingblock,whichprovidessettingorcutterpositionanddepthofcut.工件被夹持到位，铣刀靠着提供安装或铣刀位置及切削深度的安装台定位。Thefixturemustbepositionedrelativetothemachinetable,thisisdonebyengagingthetwotenonsatthebottomofthefixtureintheslotinthemachinetable.ThefixtureissecuredtothemachinetablewithT-bolts,alsoengagingintheslotsinthetable(Fig.13.3).夹具必须相对于铣床工作台定位，这可通过把夹具底部的两个凸榫插入工作台上的槽中来实现。夹具用T型螺栓固定于铣床工作台，同时与工作台上的槽接合(图13.3)。slotn.缝,狭槽,位置,水沟,细长的孔,硬币投币口,狭通道,足迹vt.开槽于,跟踪n.（名词）Anarrowopening;agrooveorslit:狭槽，缝：狭窄的开口；槽或狭长的裂缝：aslotforcoinsinavendingmachine;amailslot.自动售货机上的投币口；投信口Agapbetweenamainandanauxiliaryairfoiltoprovidespaceforairflowandfacilitatethesmoothpassageofairoverthewing.（飞机的）翼缝：主机翼与辅机翼之间的沟