unit13夾具與固定裝置

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北華大學(xué)機(jī)械學(xué)院王開寶Unit13JigsandFixture

鉆模與夾具

Introduction導(dǎo)言Ithasalreadybeenstatedthattheworkpiecemustbelocatedrelativetothecuttingtool,andbesecuredinthatposition.Aftertheworkpiecehasbeenmarkedout,itisstillnecessarytopositionitwithrespecttothemachinemovements,andtoclampitinthatpositionbeforemachiningisstarted.已經(jīng)說明了工件必須相對(duì)于切削刀具定位并確保到位。工件劃線后，仍有必要將其相對(duì)于切削運(yùn)動(dòng)定位，并在機(jī)加工開始前把它裝夾到位。

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

當(dāng)要加工若干同樣的工件時(shí)，使用鉆模和夾具可以不必在每個(gè)工件上劃線；但對(duì)鑄件或鍛件而言，還需取一試驗(yàn)工件劃線以保證照此加工不會(huì)將加強(qiáng)肋、型芯等放錯(cuò)位置。Jigsandfixturesarealikeinthattheybothincorporatedevicestoensurethattheworkpieceiscorrectlylocatedandclamped,buttheydifferinthatjigsincorporatemeansoftoolguidingduringtheactualcuttingoperation,andfixturesdonot.鉆模和夾具的相似點(diǎn)是它們都把保證工件正確定位和夾緊的裝置相結(jié)合，它們的不同在于鉆模在實(shí)際切削作業(yè)中還能與刀具導(dǎo)向方法相結(jié)合，而夾具則不能。Inpractice,theonlycuttingtoolsthatcanbeguidedwhileactuallycuttingaredrills,reamers,andsimilarcutters;andsojigsareassociatedwithdrillingoperations,andfixtureswithallotheroperations.Fixturesmayincorporatemeansofsettingthecuttingtoolsrelativetothelocationsystem.實(shí)際上，在真實(shí)切削中能被導(dǎo)向的切削刀具只有鉆頭、鉸刀和類似的刀具；因此鉆模用于鉆削作業(yè)，而夾具用于其余作業(yè)。夾具可以與切削刀具相對(duì)定位系統(tǒng)裝夾的方法結(jié)合在一起。Theadvantagesofjigsandfixturescanbesummarisedasfollows:1)Markingoutandothermeasuringandsettingoutmethodsareeliminated;鉆模和夾具的優(yōu)點(diǎn)可歸納如下：1)可以省去劃線和其它測(cè)量及放樣程序；2)Unskilledworkersmayproceedconfidentlyandquicklyinknowledgethattheworkpiececanbepositionedcorrectly,andthetoolsguidedorset;2)在知道工件能正確定位、刀具能恰當(dāng)導(dǎo)向或裝夾的情況下，不熟練的工人也能自信而快速地操作；Boltholesoftenhave1.5mmoreven3.0mmclearanceforthebolt,andthereadermaydoubtthenecessityofmakingprecisionjigsforsuchwork.Itmustberememberedthatthejigs,oncemade,willbeusedonmanycomponents,andtheextracostofanaccuratelymadejigisspreadoveralargeoutput.螺栓孔常給螺栓留出1.5毫米或甚至3.0毫米的間隙，讀者可能會(huì)懷疑為這樣的工作制造精密鉆模的必要性。但要記住，這種鉆模一旦造好，可用于許多零部件，精確制造鉆模的額外成本可分?jǐn)傇诖罅慨a(chǎn)品上。Furthermore,itissurprisinghowsmallerrorsaccumulateinamechanismduringitsassembly.Whenaclearanceisspecified,itisbettertoensureitsobservance,ratherthantoallowcarelessmarkingoutandmachiningtoencroachuponit．此外，這樣做在裝配機(jī)械裝置時(shí)其累積誤差之小也是令人驚訝的。在確定一個(gè)間隙時(shí)，最好能保證它的習(xí)慣要求，而不是隨便劃線和機(jī)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：圖13.1表示一個(gè)在空間完全自由的物體，在這種情況下它具有六個(gè)自由度。相對(duì)于三根互相垂直的坐標(biāo)軸XX、YY和ZZ來考慮這些自由度。Thebodycanmovealonganyoftheseaxes;itthereforehasthreefreedomsoftranslation.Itcanalsorotateaboutanyofthethreeaxes;itthereforehasthreefreedomsofrotation.Thetotalnumberoffreedomsissix.Whenworkislocated,asmanyofthesefreedomsaspossiblemustbeeliminated,toensurethattheoperationisperformedwiththerequiredaccuracy.此物體能沿三根坐標(biāo)軸的任意一根移動(dòng)；這樣就具有三個(gè)平移自由度。它也能圍繞三根坐標(biāo)軸的任意一根回轉(zhuǎn)；這樣它又具有三個(gè)旋轉(zhuǎn)自由度?？偟淖杂啥葦?shù)目是六個(gè)。當(dāng)工件被定位時(shí)，必須盡可能多地消除這些自由度，以保證作業(yè)按要求精度進(jìn)行。Accuracyisensuredbymachiningsuitablelocationfeaturesasearlyaspossible,andusingthemforalllocation,unlessotherconsiderationsmeanthatotherlocationfeaturesmustbeused.Ifitisnecessary,thenewlocationfeaturesmustbemachinedasaresultoflocationfromtheformerlocationfeatures.除非有必要采用另外定位要素的其它考慮，精度可通過盡可能早地加工合適的定位要素并采用它們進(jìn)行所有定位來保證。如果必要的話，新的定位要素必須作為先前的定位要素的定位結(jié)果來加工。2)Theclampingoftheworkpiece.Theclampingsystemmustbesuchthattheworkpieceisheldagainstthecuttingforces,andtheclampingforcesmustnotbesogreatastocausetheworkpiecetobecomedistortedordamaged.2)工件的裝夾：裝夾系統(tǒng)必須使工件對(duì)著切削力夾持，而且裝夾力又不能大得引起工件變形或損壞。Theworkpiecemustbesupportedbeneaththepointofclamping,toensurethattheforcesaretakenbythemainframeofthejigorfixture,andontothemachinetableandbed.Whenjigsandfixturesaredesigned,theclampingsystemisdesignedtoensurethatthecorrectclampingforceisapplied,andthattheclampscanbeoperatedquicklybutwithsafety.工件必須在裝夾點(diǎn)下被支撐，以保證這些力由鉆?；驃A具的主框架來承受并傳遞給機(jī)器臺(tái)和床身。在設(shè)計(jì)鉆模和夾具時(shí)，要同時(shí)設(shè)計(jì)裝夾系統(tǒng)來保證提供恰當(dāng)?shù)难b夾力，并使裝夾操作快速而安全。DefinitionofaDrillJig

鉆模的定義Adrilljigisadeviceforensuringthataholetobedrilled,tapped,orreamedinaworkpiecewillbemachinedintheproperplace.鉆模是一種確保在工件正確位置進(jìn)行鉆孔、攻絲或鉸孔加工的裝置。Basicallyitconsistsofaclampingdevicetoholdthepartinpositionunderhardened-steelbushingsthroughwhichthedrillpassesduringthedrillingoperation.Thedrillisguidedbythebushings.它基本上由在淬硬鋼襯套下將零件夾持到位的夾持裝置組成，鉆孔作業(yè)中鉆頭穿過這些襯套，通過它們來導(dǎo)向。Iftheworkpieceisofsimpleconstruction,thejigmaybeclampedontheworkpiece.Inmostcases,however,theworkpieceisheldbythejig,andthejigisarrangedsothattheworkpiececanbequicklyinsertedandasquicklyremovedafterthemachiningoperationisperformed.如果工件結(jié)構(gòu)比較簡(jiǎn)單，鉆模可夾持在工件上。然而大多數(shù)情況下，工件由鉆模來夾持，并且把鉆模設(shè)計(jì)成能將工件迅速裝入而在加工后同樣能很快取出。Jigsmakeitpossibletodrill,ream,andtapholesatmuchgreaterspeedsandwithgreateraccuracythanwhentheholesareproducedbyconventionalhandmethods.Anotheradvantageisthatskilledworkersarenotrequiredwhenjigsareused.Responsibilityfortheaccuracyofholelocationistakenfromtheoperatorandgiventothejig.相對(duì)于用常規(guī)的手工方法加工孔，鉆模使得鉆孔、鉸孔和攻絲速度快很多而且精度更高成為可能。另一個(gè)優(yōu)點(diǎn)是采用鉆模時(shí)不需要熟練工人。保證孔定位精度的責(zé)任從操作者身上轉(zhuǎn)移到了鉆模上。Thetermjigshouldbeusedonlyfordevicesemployedwhiledrilling,reaming,ortappingholes.Itisnotfastenedtothemachineonwhichitisusedandmaybemovedaroundonthetableofthedrillingmachinetobringeachbushingdirectlyunderthedrill.Jigsphysicallylimitandcontrolthepathofthecuttingtool.鉆模這個(gè)術(shù)語只用在服務(wù)于鉆孔、鉸孔或攻絲的裝置上。它不固定在使用它的鉆床上，它能在鉆床工作臺(tái)上到處移動(dòng)以使每個(gè)襯套都直接位于鉆頭下。鉆模有形地限制和控制鉆削刀具的路徑。Iftheoperationincludesmachiningoperationslikemilling,planing,shaping,turning,etc.,thetermfixtureshouldbeused.Afixtureholdstheworkduringmachiningoperationsbutdoesnotcontainspecialarrangementsforguidingthecuttingtool,asdrilljigsdo.如果作業(yè)還包括其它象銑削、刨削、成型、車削等機(jī)加工，則應(yīng)采用夾具這一術(shù)語。夾具在機(jī)加工作業(yè)時(shí)夾持工件，但它不象鉆模那樣包含引導(dǎo)切削刀具的特殊布置。TypicalJigsandFixtures

典型的鉆模和夾具Typicaldrilljig.Figure13.2illustratesadrillingjigfordrillingfourholesintheflangeofaworkpiecethathasbeencompletedexceptforthefourholes.典型的鉆模：圖13.2所示為一個(gè)能在某工件的法蘭上鉆四個(gè)孔的鉆模，該工件除了這四個(gè)孔外已全部完成。Theworkpiecehasanaccuratelymachinedbore,andislocatedfromtheboreandtheendface,fromacylindricalpost.Thereisnoneedtocontroltherotationalpositionabouttheaxisofthebore,becauseuptothetimewhentheholesaredrilled,itissymmetricalaboutthataxis.此工件有一精確機(jī)加工的大孔，因此通過一圓柱體采用該孔和工件端面定位。由于直至鉆這些小孔時(shí)，工件都對(duì)稱于大孔軸線，所以沒必要控制圍繞大孔軸線回轉(zhuǎn)的位置。Thefourbushesusedtocontrolthedrillareheldinthedrillplate,which,withthehandnut,isusedtoclamptheworkpieceagainstthebaseofthefixture.四個(gè)控制鉆頭的襯套裝在鉆板里，連同手?jǐn)Q螺母一起用于靠著夾具基座夾持工件。Typicalmillingfixture.Figure13.3illustratesasimplemillingfixtureformillingtheslotintheotherwisecompletedworkpieceshown.Theworkpieceislocatedfromtwoofthefourholesinitsbase,andfromtheundersideofthebase.典型的銑削夾具：圖13.3所示為一用于在圖示其它工序都完成的工件上銑槽的簡(jiǎn)單銑削夾具。此工件采用其基座上四孔中的兩孔和基座的底面定位。Theworkpieceisclampedinposition,andcutterislocatedagainstthesettingblock,whichprovidessettingorcutterpositionanddepthofcut.工件被夾持到位，銑刀靠著提供安裝或銑刀位置及切削深度的安裝臺(tái)定位。Thefixturemustbepositionedrelativetothemachinetable,thisisdonebyengagingthetwotenonsatthebottomofthefixtureintheslotinthemachinetable.ThefixtureissecuredtothemachinetablewithT-bolts,alsoengagingintheslotsinthetable(Fig.13.3).夾具必須相對(duì)于銑床工作臺(tái)定位，這可通過把夾具底部的兩個(gè)凸榫插入工作臺(tái)上的槽中來實(shí)現(xiàn)。夾具用T型螺栓固定于銑床工作臺(tái)，同時(shí)與工作臺(tái)上的槽接合(圖13.3)。slotn.縫,狹槽,位置,水溝,細(xì)長(zhǎng)的孔,硬幣投幣口,狹通道,足跡vt.開槽于,跟蹤n.（名詞）Anarrowopening;agrooveorslit:狹槽，縫：狹窄的開口；槽或狹長(zhǎng)的裂縫：aslotforcoinsinavendingmachine;amailslot.自動(dòng)售貨機(jī)上的投幣口；投信口Agapbetweenamainandanauxiliaryairfoiltoprovidespaceforairflowandfacilitatethesmoothpassageofairoverthewing.（飛機(jī)的）翼縫：主機(jī)翼與輔機(jī)翼之間的溝