unit-5-Conventional-Machining-Process

UNIT5ConventionalMachiningProcesses第5讲Canyougivemealistofmachiningprocesses?TurningBoringMillingDrillingGrindingPlanning…车削、镗削、铣削、钻削、磨削、刨削…3luckyMethodsandMachinesTurningandlathe（车削和车床）MillingandMillingMachine（铣削和铣床）DrillingandDrillPress（钻削和钻床）5.1IntroductionConventionalmachiningisthegroupofmachiningoperationsthatusesingle-ormulti-pointtoolstoremovematerialintheformofchips.Metalcuttinginvolvesremovingmetalthroughmachiningoperations.Machiningtraditionallytakesplaceonlathes,drillpresses,andmillingmachineswiththeuseofvariouscuttingtools.Mostmachininghasverylowset-upcostcomparedwithforming,molding,andcastingprocesses.However,machiningismuchmoreexpensiveforhighvolumes.Machiningisnecessarywheretighttolerancesondimensionsandfinishesarerequired.5.1译文传统机械加工是一组利用单刃或者多刃刀具以切屑形式去除材料的加工方式。金属切削意味着通过机械加工去除金属。传统的机械加工都是利用不同的刀具在车床、钻床和铣床上进行的。与成型加工、锻压和铸造工艺相比，大多数机械加工的生产准备成本都较低，然而如果是大批量生产，其成本要高得多。当对零件的尺寸公差和光洁度要求较高时，机械加工是很有必要的。5.2TurningandLatheTurningisoneofthemostcommonofmetalcuttingoperations.Inturning,aworkpieceisrotatedaboutitsaxisassingle-pointcuttingtoolsarefedintoit,shearingawayexcessmaterialandcreatingthedesiredcylindricalsurface.Turningcanoccuronbothexternalandinternalsurfacestoproduceanaxially-symmetricalcontouredpart.Partsrangingfrompocketwatchcomponentstolargediametermarinepropellershaftscanbeturnedonalathe.Apartfromturning,severalotheroperationscanalsobeperformedonlathe.marinepropellerWords&expressionsaxially['æksiəli]adv.轴向地symmetrical[si'metrikəl]a.对称的cylindrical[si'lindrikl]a.圆柱形的contoured['kɔntuəd]a.显示轮廓的，与某种形体轮廓相吻合的译文:在金属切削加工操作中，车削是最常见的一种。在车削过程中，工件绕其轴线回转，单刃车刀沿工件进给，切除掉多余的材料，最后形成要求的圆柱形表面。车削可以加工外面和内表面以形成具有轴对称的成形工件。从怀表的零件到大直径的船用螺旋桨轴都可以在车床上加工。除了车削，还有另外几种加工操作都可以在车床上进行。Boringandinternalturning.Boringandinternalturningareperformedontheinternalsurfacesbyaboringbarorsuitableinternalcuttingtools.Iftheinitialworkpieceissolid,adrillingoperationmustbeperformedfirst.Thedrillingtoolisheldinthetailstock,andthelatteristhenfedagainsttheworkpiece.Whenboringisdoneinalathe,theworkusuallyisheldinachuckoronafaceplate.Holesmaybeboredstraight,tapered,ortoirregularcontours.Boringisessentiallyinternalturningwhilefeedingthetoolparalleltotherotationaxisoftheworkpiece.5.2TurningandLatheWords&expressionstailstock['teilstɔk]n.尾座chuck[tʃʌk]n.卡盘，夹头译文:利用镗杆或合适的内圆车刀可以进行镗削和车内圆。如果工件毛坯是实心的，首先要钻孔。钻头安装在尾架上，后者向工件进给。如果在车床上进行镗削加工，工件通常装夹在卡盘或者花盘上。镗出的孔可以是直孔、锥孔或者不规则轮廓。当将刀具沿工件的回转轴线平行进给时，镗削实际上就是车内圆。5.2TurningandLathefaceplatechuckFacing.Facingistheproducingofaflatsurfaceastheresultofatool’sbeingfedacrosstheendoftherotatingworkpiece.Unlesstheworkisheldonamandrel,ifbothendsoftheworkaretobefaced,itmustbeturnedaroundafterthefirstendiscompletedandthenthefacingoperationrepeated.Thecuttingspeedshouldbedeterminedfromthelargestdiameterofthesurfacetobefaced.Facingmaybedoneeitherfromtheoutsideinwardorfromthecenteroutward.Ineithercase,thepointofthetoolmustbesetexactlyattheheightofcenterofrotation.5.2TurningandLatheBecausethecuttingforcetendstopushthetoolawayfromthework,itisusuallydesirabletoclampthecarriagetothelathebedduringeachfacingcuttopreventitfrommovingslightlyandthusproducingasurfacethatisnotflat.Inthefacingofcastingorothermaterialsthathaveahardsurface,thedepthofthefirstcutshouldbesufficienttopenetratethehardmaterialtoavoidexcessivetoolwear.5.2TurningandLatheWords&expressionsmandrel['mændrəl]n.车床心轴clamp[klæmp]v.夹紧，夹住carriage[‘kæridʒ]n.大刀架，拖板penetrate['penitreit]v.穿透，渗透toolwear刀具磨损译文:车端面可以加工出一个平面，它是当车刀沿回转工件的端面横向进给的结果。除非工件固定在心轴上，如果工件两端都要车端面，必须将一端加工完成后，将工件调头，重复进行车端面加工。车削速度必须由所加工表面的最大直径来决定。车端面可以由外向内也可以由中心向外进行。无论哪种情况，刀尖必须准确地与回转中心对正。由于切削力有将车刀推离工件的趋势，通常最可行的就是在车端面时将拖板卡紧在床身上以避免车刀轻微移动造成加工表面不平整。在对具有硬质表面的铸件或其他材料进行车端面加工时，首次切深要足以穿透硬质材料从而避免过度的刀具磨损。5.2TurningandLatheParting.Partingistheoperationbywhichonesectionofaworkpieceisseveredfromtheremainderbymeansofcutofftool.Becausecuttingtoolsarequitethinandmusthaveconsiderableoverhang,thisprocessislessaccurateandmoredifficult.Thetoolshouldbesetexactlyattheheightofaxisofrotation,bekeptsharp,haveproperclearanceangles,andbefedintotheworkpieceataproperanduniformfeedrate.5.2TurningandLatheWords&expressionsremainder[ri'meində]剩余物，余数overhang['əuvə'hæŋ]vt.悬于...之上n.伸出;突出uniform['ju:nifɔ:m]a.相同的,一致的n.制服;军服clearanceangles后角译文:切断是一种利用切断刀（割刀）将工件的一部分与其剩余部分脱离的加工方法。由于切断刀非常薄而且处于悬臂状态，因此这种加工方法不太精确而且加工起来常常比较困难。切断刀必须准确地对正回转轴，保持锋利，具有合适的后角，以合适、不变的进给率沿工件进给。5.2TurningandLatheThreading.Threadingcanbeconsideredasturningsincethepathtobetravelledbythecuttingtoolishelical.However,therearesomemajordifferencesbetweenturningandthreading.Whileinturning,theinterestisingeneratingasmoothcylindricalsurface,inthreadingtheinterestisincuttingahelicalthreadofagivenformanddepthwhichcanbecalculatedfromtheformulae.5.2TurningandLathehelical[‘helikəl]a.螺旋状的译文:车螺纹可以看作是车削，只是车刀所形成的加工轨迹是螺旋线。但二者也存在一些不同之处。车削主要考虑能否生成光滑的圆柱形表面，而车螺纹注重的是能否切出具有按公式计算出来的规定形状和深度的螺旋线。第6讲Therearetwobasicrequirementsforthreadcutting.•Anaccuratelyshapedandproperlymountedtoolisneededbecausethreadcuttingisaform-cuttingoperation.Theresultingthreadprofileisdeterminedbytheshapeofthetoolanditspositionrelativetotheworkpiece.