浅析影响机械加工精度的主要因素

浅析影响机械加工精度的主要因素摘要:文章介绍了影响机械加工精度的几个重要因素。在诸多误差因,机床的几何误差、工艺系统的受力变形和受热变形占有突出的位置,通过了解这些误差因素是如何影响加工误差的工达到质量要素中,可以使工件的加求。Pickto:thispaperintroducesseveralimportantfactorsaffectingmachiningprecision.Inmanyerrorfactors,theforceddeformationofthegeometricerrorofthemachinetool,processsystemandheatdeformationhasaprominentposition,byknowinghowtheerrorfactorsaffectmachiningerror,canmaketheworkpieceprocessingtomeetthequalityrequirements.关键词:加工精度;误差;工艺系统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随着国民经济实力和科学技术水平的提高,社会要求提高产品的质量。而加工精度是衡量零件加工质量的重要指标,所以保证零件的加工精度很重要。这就要求我们来了解影响机械加工精度的因素,从而提高加工精度。在加工过程中工艺系统会产生各种误差,这些误差与工艺系统本身的结构状态和切削过程有关,产生加工误差的主要因素有:Withtheimprovementofnationaleconomicstrengthandscientificandtechnologicallevelandsocialrequirementstoimprovethequalityoftheproducts.Themachiningaccuracyisoneoftheimportantindicatorstomeasurepartsprocessingquality,soit'sveryimportanttoguaranteethepartsmachiningprecision.Thisrequiresustounderstandthefactorsthatinfluencethemachiningprecisionandimprovethemachiningaccuracy.Intheprocessofmachiningprocesssystemcanproduceallkindsoferror,theerrorandprocessstructurestateofthesystemandthecuttingprocess,amajorfactorintheproductionofmachiningerrorare:

//1加工原理误差1processingprincipleerror加工过程由于采用了近似的加工方法,近似的传动或近似的刀具轮廓而产生的加工误差。Machiningprocesswithapproximatemethod,approximatetransmissionorsimilarcuttercontourmachiningerror.1.1采用近似的加工运动造成的误差1.1USEStheapproximationofthemachiningerrorcausedbymotion在许多场合,为了得到要求的工件表面,应采用完全准确的运动联系。但,致使,反而难以达到较高的加工精度,有时甚至是不可能做到。如,由于其导程t=πm,式中有π这个无理因子,,就存在原理误差。,必须在工件或刀具的运动之间建立一定的联系。从理论上讲是采用理论上完全准确的加工原理有时使机床或夹具极为复杂制造困难在车削或磨削模数螺纹时在用配换齿轮来得到导程数值时Onmanyoccasions,inordertogettherequirementsoftheworkpiecesurface,mustbebetweentheworkpieceortoolmovementtoestablishaconnection.Intheory,shouldbecompletelyaccuratemovementofthecontact.Butusingtheorycompletelyaccurateprocessingprinciplemachineorjigisverycomplex,sometimescausingtrouble,butdifficulttoachievehighmachiningaccuracy,sometimesevenimpossible.Asinthethreadturningorgrindingmoduleleadt=PIm,becauseofitstypein/PItheirrationalfactor,inusewithgeartogetleadvalue,thereisaprincipleerror.1.2采用近似的刀具轮廓造成的误差1.2byusingapproximatecontourerrorcaused用成形刀具加工复杂的曲面时,要使刀具刃口做得完全符合理论,有时非常困难,往往采用圆弧、直线等简单近似的线型代,为了滚刀的制造方便,多用基本蜗杆来代替渐开线基本蜗杆,从而曲线的轮廓替理论曲线。如用滚刀滚切渐开线齿轮时阿基米德基本蜗杆或法向直廓产生了加工原理误差。Withformingcuttingtoolswhenmachiningcomplexcurvedsurface,tomakethecutterbladeisdonecompletelyconformtothetheoreticalcurvecontour,sometimesisverydifficult,oftenusethesimplesuchascircular,linearapproximationofthelinearcurveinsteadoftheory.Ifusehobbinginvolutegear,thegearhobtohobmanufactureisconvenient,multi-purposeArchimedeswormorbasicnormalstraightoutlinebasicworminsteadofinvoluteworm,toproducetheprocessingprincipleerror.2机床几何误差及磨损其对加工精度的影响

//2machinetoolgeometricerrorandweartheireffectsonmachiningaccuracy加工中刀具相对于工件的成形运动一般都是通过机床完成的,因此工件的加工精度在很大程度上取决于机床的精度。机床制造误差对工件加工精度影响较大的有:主轴回转误差、导轨误差和传动链误差。Processingthecuttingtoolrelativetotheworkpieceformingsportsareusuallydonebymachine,sotheworkpiecemachiningaccuracydependslargelyontheaccuracyofmachinetools.Hadagreaterinfluenceonthemanufactureerrorofworkpiecemachiningaccuracyofmachinetoolare:theerrorofspindle,guideandtransmissionchainerrors.2.1主轴回转误差2.1thespindlerotationerror主轴的回转误差直接影响被加工工件的形状和位置精度,可分解为径向跳动、轴向跳动和角度摆动。由于存在误差敏感方向,加工不同表面时,主轴的径向跳动所引起的加工误差也不同。例如,在车床上加工外圆或内孔时,主轴的径向跳动将引起工件的圆度误差,但对于端/面加工没有直接影响。车端面时,主轴的轴向跳动将造成工件端面的,以及端面相对于内;车螺纹时,会造成不大。主轴的角径向跳动对加工误差的影响相似,主,而且平面度误差、外圆的垂直度误差螺距误差。主轴的轴向跳动对加工外圆或内孔的影响度摆动对加工误差的影响与主轴要区别在于主轴的角度摆动不仅影响工件加工表面的圆度误差影响工件加工表面的圆柱度误差。Spindlerotationerrorofshapeandpositiondirectlyaffectthemachiningprecision,canbedecomposedintoradialrunoutandaxialpulsationandswingAngle.Duetoerrorsensitivedirection,differentsurfaceprocessing,mainshaftrunoutofthemachiningerrorcausedbydifferent,too.Cylindricalholesaremachinedonlathes,forexample,orinthehole,thespindlerunoutwillcausetheworkpieceroundnesserror,butforendfaceprocessinghavenodirectimpact.Surfacing,theaxialpulsationofthespindlewillcausetheflatnesserrorofworkpieceendface,andfacerelativetotheinternalandexternalcircularverticalityerror;Whenthreading,cancausepitcherror.Axialpulsationofthespindleofmachiningcylindricalorinnerholeoftheimpactisnotbig.SpindleswingAngleonthemachiningerrorandtheinfluenceofthespindlerunouthassimilareffectontheprocessingerror,themaindifferenceisthatthespindleswingAnglenotonlyaffectstheroundnesserrorofworkpiecemachiningsurface,andtheinfluenceonthesurfaceofthe

//workpieceprocessingcylindricityerror.2.2导轨误差2.2guideerror导轨在机床中起导向和承载作用,它既是确定机床主要部件相对位置的基准,也是运动的基准。它的各项误差直接对形状精度产生影响。导轨在水平面内的直线度误差将直接反映在被加工工件表面的法线方向敏感方向)上,对加工精度的影响最大。导轨在垂直平面内(误差的直线度误差对加工精度影响很小,一般可忽略不计。前后导轨的平,刀尖的运动轨迹为一条行度误差会使工作台在运动过程中产生摆动空间曲线,使工件产生形状误差。Playsaroleofguidanceandbearingguidetrackinmachinetool,itistodeterminetherelativepositionofmaincomponentsofmachinetoolbase,isalsoabenchmarkofthemovement.It'seacherroraffectshapeprecisiondirectly.Guiderailstraightnesserrorintheplaneofthehorizonwillbedirectlyreflectedinthenormaldirectionoftheworkpiecesurfaceprocessed(errorsensitivedirection),thebiggestimpactonmachiningaccuracy.Guideintheverticalplanestraightnesserroronmachiningprecisionoftheeffectisverysmall,generallynegligible.Beforeandafter/theparallelismerrorofguidewayworkbenchduringexercisecausesswing,tiptrajectoryforaspacecurve,theworkpieceformerrorisproduced.2.3传动链误差2.3thetransmissionchainerror切削过程中,工件表面的成形运动,是通过一系列的传动机构来实及蜗杆等。这,这些误了传动链的传动误差。传动机构越多,传动路线越长,则传动现的。传动机构的传动元件有齿轮、丝杆、螺母、蜗轮些传动元件由于其加工、装配和使用过程中磨损而产生误差差就构成误差越大。机床传动链误差是影响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、夹具的制造误差及磨损3manufacturingerrorofcuttingtool,jigandwear刀具误差对加工精度的影响随刀具的种类不同而不同。一般刀具(如车刀(如钻头、铰刀工零件的尺寸精度;成形刀具(成形刀差,主要影响被加工面的形状精度。而刀具的磨损会直接影响刀具相对被加工表面的位置,造成被加工零件的尺寸误差,夹具有正确的位置,因此夹具加工精度(特别是位置精度)有很大影响。夹具、镗刀及铣刀等)的制造误差,对加工精度没有直接的影响;定及槽铣刀等)的尺寸误差,直接影响被加以及齿轮滚刀等)的误尺寸刀具、拉刀、成形铣刀的作用是使工件相对于刀具和机床具的制造误差对工件的的制造误差由定位误差、夹紧误差、夹具的安装误差、导引误差、分度误差以及夹具的磨损组成。夹具的磨损会引起工件的定位误差。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工艺系统受力变形引起的误差4processforcedeformationerrorcausedbythesystem工艺系统是一弹性系统,在加工时由于切削力、夹紧力和传动力等作用会产生相应变形破坏了刀具和工件间的正确位置,从而产生加工误差。Processsystemisaflexiblesystem,intheprocessbecauseofthecuttingforce,clampingforceandmomentumeffectwillproducecorresponding

//deformationdamagethecorrectpositionbetweenthecutterandworkpiece,theresultingmachiningerror.4.1切削过程中受力点位置变化引起的加工误差4.1intheprocessofcuttingmachiningerrorcausedbythestresspointlocationchange切削过程中,工艺系统的刚度随切削力着力点位置的变化而变化,引起系统变形的差异,使被加工表面产生形状误差。Stiffnessofthecuttingprocess,aprocesssystemalongwiththechangeofcuttingforcefocuspositionchanges,causesthedifferenceofthedeformationsystem,maketheprocessedsurfaceshapeerror.4.2切削力大小变化引起的加工误差——误差复映4.2cuttingforcechangestothesizeofthemachiningerror-errorrerun工件的毛坯外形虽然具有粗略的零件形状,但它在尺寸、形状以及表面层材料硬度上都有较大的误差。毛坯的这些误差在加工时使切削深度不断发生变化,从而导致切削力的变化,进而引起工艺系统产生/相应的变形,使得零件在加工后还保留与毛坯表面类似的形状或尺寸误差。当然工件表面残留的误差比毛坯表面误差要小得多。这种现象称为“误差复映规律”,所引起的加工误差称为“误差复映”。除切削力外,传动力、惯性重力、夹紧力等其它作用力也会使工形发生变化,从而引起加工误差,影响加工精度。艺系统的变Artifactsoftheblankshape,althoughhastheroughshapeofparts,butitonthesize,shape,materialandsurfacehardnesshaslargererror.Blankerrorintheprocessingofthesemakesthecuttingdepthchangesconstantly,resultinginthechangeofcuttingforce,resultinginprocesssystemtoproducecorrespondingdeformation,makethepartsaftermachiningalsoretainstheshapeorsizesimilartothatoftheblanksurfaceerror.Ofcourseresidualerrorofworkpiecesurfaceerrorismuchsmallerthantheblanksurface.Rerunthephenomenonknownasthe"errors",causedbythemachiningerroriscalled"rerun"error.Inadditiontothecuttingforce,momentum,inertia,gravity,clampingforceandotherforcechangealsocanmakedeformationoftechnologicalsystem,thuscauseprocessingerror,affectthemachiningaccuracy.5工艺系统受热变形引起的误差5processsystemoferrorsduetothermaldeformation

//机械加工中,工艺系统在各种热源的作用下产生一定的热变形。、材料的不同,使工部分的变形产生差异,从而破坏了刀具与工,产生加工,热变形引起的加工误差误差的40%～70%。由于工艺系统热源分布的不均匀性及各环节结构艺系统各件的准确位置及运动关系误差。尤其对于精密加工占总加工Mechanicalprocessing,thetechnologysystemundertheactionofallkindsofheatsourcestoproducethermaldeformation.Duetoprocesssystemofheatdistributioninhomogeneityandeverylinkofstructure,materialisdifferent,makethedeformationofeachpartofprocesssystem,underminingthepositionofthecuttingtoolandworkpieceandthemotionrelationship,havemachiningerror.Especiallyforprecisionmachining,themachiningerrorcausedbythethermaldeformationofmachiningerrorof40%~70%.5.1机床热变形对加工精度的影响5.1machinetoolthermaldeformation'sinfluenceonthemachiningaccuracy机床受热源的影响,各部分温度将发生变化,由于热源分布的不均/匀和机床机构的复杂性,机床的各部件发生不同程度的热变形,破坏了机床各部件原有的相互位置关系,影响加工精度。不同类型的机床由于热源不同,对加工精度影响也不同。Machinetoolisinfluencedbyheatsource,temperaturewillchangetheparts,becauseofthecomplexityoftheunevendistributionofheatsourceandmachinetoolmechanism,machinetoolpartsofvaryingdegreesofthermaldeformation,damagetheoriginalpositionrelationofmachinetoolparts,affectthemachiningaccuracy.Differenttypesofmachinetoolsbecauseoftheheatsourceisdifferent,havedifferentinfluenceonmachiningaccuracy.5.2刀具热变形对加工精度的影响5.2toolingthermaldeformation'sinfluenceonthemachiningaccuracy尽管在切削加工中传入刀具的热量只有3%～5%,但由于刀具的尺寸和热容量小,故仍有很高的温升,从而引起刀具的热伸长并造成加;对于,使加工表面,刃部的温度高达700℃～800℃,刀具热伸长量可达0.03mm～工误差。粗加工时刀具的热变形对加工精度的影响可忽略不计加工要求较高的零件,刀具的热变形对加工精度影响较大产生形状误差。例如用高速钢刀具车削时

//Althoughincomingcuttingtoolinmachiningheatonly3%~5%,butduetothesizeofthecuttingtoolandtheheatcapacityissmall,sothereisstillaveryhightemperature,thatcausethetool'sthermalelongationandcauseprocessingerror.Roughmachiningcutter'sthermaldeformation'sinfluenceonthemachiningaccuracycanbeneglected;Higherrequirementsforprocessingcomponents,affectedbythethermaldeformationofmachiningaccuracyofcuttingtool,makestheprocessingsurfaceformerror.Whenusingahighspeedsteelcuttercutting,forexample,thetemperatureofthebladeisashighas700℃~800℃,toolthermalelongationcanbeupto0.03mm~0.05mm。0.05mm.5.3工件热变形对加工精度的影响5.3hotdeformation'sinfluenceonthemachiningprecisionofworkpieces工件的热变形主要是由切削热引起的,热变形情况与加工方法和是否均匀受热有关。/Artifactsofthethermaldeformationismainlycausedbycuttingheat,thethermaldeformationisrelatedtowhetherprocessingmethodanduniformheat.5.3.1工件均匀受热5.3.1workpieceevenlyheated对于一些简单的均匀受热工件、磨轴类件的外圆,待加工后,如车冷却到室温