淺析影響機(jī)械加工精度的主要因素

淺析影響機(jī)械加工精度的主要因素摘要:文章介紹了影響機(jī)械加工精度的幾個重要因素。在諸多誤差因,機(jī)床的幾何誤差、工藝系統(tǒng)的受力變形和受熱變形占有突出的位置,通過了解這些誤差因素是如何影響加工誤差的工達(dá)到質(zhì)量要素中,可以使工件的加求。Pickto:thispaperintroducesseveralimportantfactorsaffectingmachiningprecision.Inmanyerrorfactors,theforceddeformationofthegeometricerrorofthemachinetool,processsystemandheatdeformationhasaprominentposition,byknowinghowtheerrorfactorsaffectmachiningerror,canmaketheworkpieceprocessingtomeetthequalityrequirements.關(guān)鍵詞:加工精度;誤差;工藝系統(tǒng)Keywords:machiningprecision;Error;ProcesssystemAbstract:Thisarticleintroducedinfluencemachine-finishingprecisionseveralimportantattributes.Inmanyerroneousfactors,enginebed'sgeometricalerror,thecraftsystem'sstressdistortionandtheheatingdistortionholdtheprominentposition,throughunderstoodtheprocessingerror,mayenabletheworkpiecetheprocessingtoachievethequalityrequirement.Abstract:Thisarticleintroducedinfluencemachine-finishingprecision

/severalimportantattributes.Inmanyerroneousfactors,enginebed'sgeometricalerror,thecraftsystem'sstressdistortionandtheheatingdistortionholdtheprominentposition,throughunderstoodtheprocessingerror,mayenabletheworkpiecetheprocessingtoyourthequalityrequirement.Keywords:workingaccuracy;error;craftsystemKeywords:theworkingaccuracy;Theerror;Craftsystem隨著國民經(jīng)濟(jì)實(shí)力和科學(xué)技術(shù)水平的提高,社會要求提高產(chǎn)品的質(zhì)量。而加工精度是衡量零件加工質(zhì)量的重要指標(biāo),所以保證零件的加工精度很重要。這就要求我們來了解影響機(jī)械加工精度的因素,從而提高加工精度。在加工過程中工藝系統(tǒng)會產(chǎn)生各種誤差,這些誤差與工藝系統(tǒng)本身的結(jié)構(gòu)狀態(tài)和切削過程有關(guān),產(chǎn)生加工誤差的主要因素有:Withtheimprovementofnationaleconomicstrengthandscientificandtechnologicallevelandsocialrequirementstoimprovethequalityoftheproducts.Themachiningaccuracyisoneoftheimportantindicatorstomeasurepartsprocessingquality,soit'sveryimportanttoguaranteethepartsmachiningprecision.Thisrequiresustounderstandthefactorsthatinfluencethemachiningprecisionandimprovethemachiningaccuracy.Intheprocessofmachiningprocesssystemcanproduceallkindsoferror,theerrorandprocessstructurestateofthesystemandthecuttingprocess,amajorfactorintheproductionofmachiningerrorare:

//1加工原理誤差1processingprincipleerror加工過程由于采用了近似的加工方法,近似的傳動或近似的刀具輪廓而產(chǎn)生的加工誤差。Machiningprocesswithapproximatemethod,approximatetransmissionorsimilarcuttercontourmachiningerror.1.1采用近似的加工運(yùn)動造成的誤差1.1USEStheapproximationofthemachiningerrorcausedbymotion在許多場合,為了得到要求的工件表面,應(yīng)采用完全準(zhǔn)確的運(yùn)動聯(lián)系。但,致使,反而難以達(dá)到較高的加工精度,有時甚至是不可能做到。如,由于其導(dǎo)程t=πm,式中有π這個無理因子,,就存在原理誤差。,必須在工件或刀具的運(yùn)動之間建立一定的聯(lián)系。從理論上講是采用理論上完全準(zhǔn)確的加工原理有時使機(jī)床或夾具極為復(fù)雜制造困難在車削或磨削模數(shù)螺紋時在用配換齒輪來得到導(dǎo)程數(shù)值時Onmanyoccasions,inordertogettherequirementsoftheworkpiecesurface,mustbebetweentheworkpieceortoolmovementtoestablishaconnection.Intheory,shouldbecompletelyaccuratemovementofthecontact.Butusingtheorycompletelyaccurateprocessingprinciplemachineorjigisverycomplex,sometimescausingtrouble,butdifficulttoachievehighmachiningaccuracy,sometimesevenimpossible.Asinthethreadturningorgrindingmoduleleadt=PIm,becauseofitstypein/PItheirrationalfactor,inusewithgeartogetleadvalue,thereisaprincipleerror.1.2采用近似的刀具輪廓造成的誤差1.2byusingapproximatecontourerrorcaused用成形刀具加工復(fù)雜的曲面時,要使刀具刃口做得完全符合理論,有時非常困難,往往采用圓弧、直線等簡單近似的線型代,為了滾刀的制造方便,多用基本蝸桿來代替漸開線基本蝸桿,從而曲線的輪廓替理論曲線。如用滾刀滾切漸開線齒輪時阿基米德基本蝸桿或法向直廓產(chǎn)生了加工原理誤差。Withformingcuttingtoolswhenmachiningcomplexcurvedsurface,tomakethecutterbladeisdonecompletelyconformtothetheoreticalcurvecontour,sometimesisverydifficult,oftenusethesimplesuchascircular,linearapproximationofthelinearcurveinsteadoftheory.Ifusehobbinginvolutegear,thegearhobtohobmanufactureisconvenient,multi-purposeArchimedeswormorbasicnormalstraightoutlinebasicworminsteadofinvoluteworm,toproducetheprocessingprincipleerror.2機(jī)床幾何誤差及磨損其對加工精度的影響

//2machinetoolgeometricerrorandweartheireffectsonmachiningaccuracy加工中刀具相對于工件的成形運(yùn)動一般都是通過機(jī)床完成的,因此工件的加工精度在很大程度上取決于機(jī)床的精度。機(jī)床制造誤差對工件加工精度影響較大的有:主軸回轉(zhuǎn)誤差、導(dǎo)軌誤差和傳動鏈誤差。Processingthecuttingtoolrelativetotheworkpieceformingsportsareusuallydonebymachine,sotheworkpiecemachiningaccuracydependslargelyontheaccuracyofmachinetools.Hadagreaterinfluenceonthemanufactureerrorofworkpiecemachiningaccuracyofmachinetoolare:theerrorofspindle,guideandtransmissionchainerrors.2.1主軸回轉(zhuǎn)誤差2.1thespindlerotationerror主軸的回轉(zhuǎn)誤差直接影響被加工工件的形狀和位置精度,可分解為徑向跳動、軸向跳動和角度擺動。由于存在誤差敏感方向,加工不同表面時,主軸的徑向跳動所引起的加工誤差也不同。例如,在車床上加工外圓或內(nèi)孔時,主軸的徑向跳動將引起工件的圓度誤差,但對于端/面加工沒有直接影響。車端面時,主軸的軸向跳動將造成工件端面的,以及端面相對于內(nèi);車螺紋時,會造成不大。主軸的角徑向跳動對加工誤差的影響相似,主,而且平面度誤差、外圓的垂直度誤差螺距誤差。主軸的軸向跳動對加工外圓或內(nèi)孔的影響度擺動對加工誤差的影響與主軸要區(qū)別在于主軸的角度擺動不僅影響工件加工表面的圓度誤差影響工件加工表面的圓柱度誤差。Spindlerotationerrorofshapeandpositiondirectlyaffectthemachiningprecision,canbedecomposedintoradialrunoutandaxialpulsationandswingAngle.Duetoerrorsensitivedirection,differentsurfaceprocessing,mainshaftrunoutofthemachiningerrorcausedbydifferent,too.Cylindricalholesaremachinedonlathes,forexample,orinthehole,thespindlerunoutwillcausetheworkpieceroundnesserror,butforendfaceprocessinghavenodirectimpact.Surfacing,theaxialpulsationofthespindlewillcausetheflatnesserrorofworkpieceendface,andfacerelativetotheinternalandexternalcircularverticalityerror;Whenthreading,cancausepitcherror.Axialpulsationofthespindleofmachiningcylindricalorinnerholeoftheimpactisnotbig.SpindleswingAngleonthemachiningerrorandtheinfluenceofthespindlerunouthassimilareffectontheprocessingerror,themaindifferenceisthatthespindleswingAnglenotonlyaffectstheroundnesserrorofworkpiecemachiningsurface,andtheinfluenceonthesurfaceofthe

//workpieceprocessingcylindricityerror.2.2導(dǎo)軌誤差2.2guideerror導(dǎo)軌在機(jī)床中起導(dǎo)向和承載作用,它既是確定機(jī)床主要部件相對位置的基準(zhǔn),也是運(yùn)動的基準(zhǔn)。它的各項(xiàng)誤差直接對形狀精度產(chǎn)生影響。導(dǎo)軌在水平面內(nèi)的直線度誤差將直接反映在被加工工件表面的法線方向敏感方向)上,對加工精度的影響最大。導(dǎo)軌在垂直平面內(nèi)(誤差的直線度誤差對加工精度影響很小,一般可忽略不計(jì)。前后導(dǎo)軌的平,刀尖的運(yùn)動軌跡為一條行度誤差會使工作臺在運(yùn)動過程中產(chǎn)生擺動空間曲線,使工件產(chǎn)生形狀誤差。Playsaroleofguidanceandbearingguidetrackinmachinetool,itistodeterminetherelativepositionofmaincomponentsofmachinetoolbase,isalsoabenchmarkofthemovement.It'seacherroraffectshapeprecisiondirectly.Guiderailstraightnesserrorintheplaneofthehorizonwillbedirectlyreflectedinthenormaldirectionoftheworkpiecesurfaceprocessed(errorsensitivedirection),thebiggestimpactonmachiningaccuracy.Guideintheverticalplanestraightnesserroronmachiningprecisionoftheeffectisverysmall,generallynegligible.Beforeandafter/theparallelismerrorofguidewayworkbenchduringexercisecausesswing,tiptrajectoryforaspacecurve,theworkpieceformerrorisproduced.2.3傳動鏈誤差2.3thetransmissionchainerror切削過程中,工件表面的成形運(yùn)動,是通過一系列的傳動機(jī)構(gòu)來實(shí)及蝸桿等。這,這些誤了傳動鏈的傳動誤差。傳動機(jī)構(gòu)越多,傳動路線越長,則傳動現(xiàn)的。傳動機(jī)構(gòu)的傳動元件有齒輪、絲桿、螺母、蝸輪些傳動元件由于其加工、裝配和使用過程中磨損而產(chǎn)生誤差差就構(gòu)成誤差越大。機(jī)床傳動鏈誤差是影響表面加工精度的主要原因之一。Formingonthesurfaceofthecuttingprocess,theworkpiecemovement,isimplementedthroughaseriesoftransmissionmechanism.Transmissionmechanismofthetransmissionelementisthegear,screw,nutandwormgearandworm,etc.Thesetransmissioncomponentsduetowearandtearduringitsfabrication,assemblyanduseandproduceerror,theerrorwillconstitutethetransmissionchainoftransmissionerror.Transmissionmechanism,themorethelongertherouteoftransmission,thetransmissionerrorislarger.Machinetooltransmissionchainerroris

//oneofthemostimportantfactorstoaffectthemachiningaccuracyofthesurface.3刀具、夾具的制造誤差及磨損3manufacturingerrorofcuttingtool,jigandwear刀具誤差對加工精度的影響隨刀具的種類不同而不同。一般刀具(如車刀(如鉆頭、鉸刀工零件的尺寸精度;成形刀具(成形刀差,主要影響被加工面的形狀精度。而刀具的磨損會直接影響刀具相對被加工表面的位置,造成被加工零件的尺寸誤差,夾具有正確的位置,因此夾具加工精度(特別是位置精度)有很大影響。夾具、鏜刀及銑刀等)的制造誤差,對加工精度沒有直接的影響;定及槽銑刀等)的尺寸誤差,直接影響被加以及齒輪滾刀等)的誤尺寸刀具、拉刀、成形銑刀的作用是使工件相對于刀具和機(jī)床具的制造誤差對工件的的制造誤差由定位誤差、夾緊誤差、夾具的安裝誤差、導(dǎo)引誤差、分度誤差以及夾具的磨損組成。夾具的磨損會引起工件的定位誤差。Toolerror'sinfluenceonthemachiningaccuracyvarieswiththekindsofcuttingtools.Generaltool(suchasturningtool,boringtoolandcutter,etc.)ofthemanufacturingerrorandinfluenceonmachiningaccuracyisnotdirectly;Sizeofthecuttingtool(e.g.,drill,reamer,broachandslottingcutter,etc.)thesizeoftheerror,anddirectlyaffectthemachining/partsdimensionalaccuracy;Formingtools(formingknife,formingmillingcutterandthegearhob,etc.)oftheerror,andmainlyaffectthemachiningsurfaceshapeaccuracy.Andtoolwearwilldirectlyaffectthecuttingtoolrelativelocationonthesurfaceoftheprocessed,sizeerrorcausedbymachiningparts,fixtureoftheroleistomaketheworkpiecerelativetothecuttingtoolandmachinetoolhasthecorrectposition,sothefixturemanufacturingerrorofworkpiecemachiningaccuracy(especiallythelocationaccuracy)hasverybigeffect.Fixturemanufacturingerrorbythepositioningerror,clampingerror,theinstallationerrorofthejig,guidanceerror,indexingandfixtureofwearandtear.Clampwearcancausethepositioningerrorofworkpiece.4工藝系統(tǒng)受力變形引起的誤差4processforcedeformationerrorcausedbythesystem工藝系統(tǒng)是一彈性系統(tǒng),在加工時由于切削力、夾緊力和傳動力等作用會產(chǎn)生相應(yīng)變形破壞了刀具和工件間的正確位置,從而產(chǎn)生加工誤差。Processsystemisaflexiblesystem,intheprocessbecauseofthecuttingforce,clampingforceandmomentumeffectwillproducecorresponding

//deformationdamagethecorrectpositionbetweenthecutterandworkpiece,theresultingmachiningerror.4.1切削過程中受力點(diǎn)位置變化引起的加工誤差4.1intheprocessofcuttingmachiningerrorcausedbythestresspointlocationchange切削過程中,工藝系統(tǒng)的剛度隨切削力著力點(diǎn)位置的變化而變化,引起系統(tǒng)變形的差異,使被加工表面產(chǎn)生形狀誤差。Stiffnessofthecuttingprocess,aprocesssystemalongwiththechangeofcuttingforcefocuspositionchanges,causesthedifferenceofthedeformationsystem,maketheprocessedsurfaceshapeerror.4.2切削力大小變化引起的加工誤差——誤差復(fù)映4.2cuttingforcechangestothesizeofthemachiningerror-errorrerun工件的毛坯外形雖然具有粗略的零件形狀,但它在尺寸、形狀以及表面層材料硬度上都有較大的誤差。毛坯的這些誤差在加工時使切削深度不斷發(fā)生變化,從而導(dǎo)致切削力的變化,進(jìn)而引起工藝系統(tǒng)產(chǎn)生/相應(yīng)的變形,使得零件在加工后還保留與毛坯表面類似的形狀或尺寸誤差。當(dāng)然工件表面殘留的誤差比毛坯表面誤差要小得多。這種現(xiàn)象稱為“誤差復(fù)映規(guī)律”,所引起的加工誤差稱為“誤差復(fù)映”。除切削力外,傳動力、慣性重力、夾緊力等其它作用力也會使工形發(fā)生變化,從而引起加工誤差,影響加工精度。藝系統(tǒng)的變Artifactsoftheblankshape,althoughhastheroughshapeofparts,butitonthesize,shape,materialandsurfacehardnesshaslargererror.Blankerrorintheprocessingofthesemakesthecuttingdepthchangesconstantly,resultinginthechangeofcuttingforce,resultinginprocesssystemtoproducecorrespondingdeformation,makethepartsaftermachiningalsoretainstheshapeorsizesimilartothatoftheblanksurfaceerror.Ofcourseresidualerrorofworkpiecesurfaceerrorismuchsmallerthantheblanksurface.Rerunthephenomenonknownasthe"errors",causedbythemachiningerroriscalled"rerun"error.Inadditiontothecuttingforce,momentum,inertia,gravity,clampingforceandotherforcechangealsocanmakedeformationoftechnologicalsystem,thuscauseprocessingerror,affectthemachiningaccuracy.5工藝系統(tǒng)受熱變形引起的誤差5processsystemoferrorsduetothermaldeformation

//機(jī)械加工中,工藝系統(tǒng)在各種熱源的作用下產(chǎn)生一定的熱變形。、材料的不同,使工部分的變形產(chǎn)生差異,從而破壞了刀具與工,產(chǎn)生加工,熱變形引起的加工誤差誤差的40%～70%。由于工藝系統(tǒng)熱源分布的不均勻性及各環(huán)節(jié)結(jié)構(gòu)藝系統(tǒng)各件的準(zhǔn)確位置及運(yùn)動關(guān)系誤差。尤其對于精密加工占總加工Mechanicalprocessing,thetechnologysystemundertheactionofallkindsofheatsourcestoproducethermaldeformation.Duetoprocesssystemofheatdistributioninhomogeneityandeverylinkofstructure,materialisdifferent,makethedeformationofeachpartofprocesssystem,underminingthepositionofthecuttingtoolandworkpieceandthemotionrelationship,havemachiningerror.Especiallyforprecisionmachining,themachiningerrorcausedbythethermaldeformationofmachiningerrorof40%~70%.5.1機(jī)床熱變形對加工精度的影響5.1machinetoolthermaldeformation'sinfluenceonthemachiningaccuracy機(jī)床受熱源的影響,各部分溫度將發(fā)生變化,由于熱源分布的不均/勻和機(jī)床機(jī)構(gòu)的復(fù)雜性,機(jī)床的各部件發(fā)生不同程度的熱變形,破壞了機(jī)床各部件原有的相互位置關(guān)系,影響加工精度。不同類型的機(jī)床由于熱源不同,對加工精度影響也不同。Machinetoolisinfluencedbyheatsource,temperaturewillchangetheparts,becauseofthecomplexityoftheunevendistributionofheatsourceandmachinetoolmechanism,machinetoolpartsofvaryingdegreesofthermaldeformation,damagetheoriginalpositionrelationofmachinetoolparts,affectthemachiningaccuracy.Differenttypesofmachinetoolsbecauseoftheheatsourceisdifferent,havedifferentinfluenceonmachiningaccuracy.5.2刀具熱變形對加工精度的影響5.2toolingthermaldeformation'sinfluenceonthemachiningaccuracy盡管在切削加工中傳入刀具的熱量只有3%～5%,但由于刀具的尺寸和熱容量小,故仍有很高的溫升,從而引起刀具的熱伸長并造成加;對于,使加工表面,刃部的溫度高達(dá)700℃～800℃,刀具熱伸長量可達(dá)0.03mm～工誤差。粗加工時刀具的熱變形對加工精度的影響可忽略不計(jì)加工要求較高的零件,刀具的熱變形對加工精度影響較大產(chǎn)生形狀誤差。例如用高速鋼刀具車削時

//Althoughincomingcuttingtoolinmachiningheatonly3%~5%,butduetothesizeofthecuttingtoolandtheheatcapacityissmall,sothereisstillaveryhightemperature,thatcausethetool'sthermalelongationandcauseprocessingerror.Roughmachiningcutter'sthermaldeformation'sinfluenceonthemachiningaccuracycanbeneglected;Higherrequirementsforprocessingcomponents,affectedbythethermaldeformationofmachiningaccuracyofcuttingtool,makestheprocessingsurfaceformerror.Whenusingahighspeedsteelcuttercutting,forexample,thetemperatureofthebladeisashighas700℃~800℃,toolthermalelongationcanbeupto0.03mm~0.05mm。0.05mm.5.3工件熱變形對加工精度的影響5.3hotdeformation'sinfluenceonthemachiningprecisionofworkpieces工件的熱變形主要是由切削熱引起的,熱變形情況與加工方法和是否均勻受熱有關(guān)。/Artifactsofthethermaldeformationismainlycausedbycuttingheat,thethermaldeformationisrelatedtowhetherprocessingmethodanduniformheat.5.3.1工件均勻受熱5.3.1workpieceevenlyheated對于一些簡單的均勻受熱工件、磨軸類件的外圓,待加工后,如車?yán)鋮s到室溫