《機(jī)械專業(yè)英語》課件第3章

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LEARNTOSPEAKNEWWORDSANDEXPRESSIONSNOTES

EXERCISES

READINGMATERIALPROFESSIONALWORDSANDPHRASESUnit3TEXT ConventionalMillingVSClimbMillingTherearetwomethodsofmilling，i.e.conventionalorupmillingandclimbordownmilling．

Inconventionalmilling，thecutterrotatesagainstthedirectionoffeed．Thismethodhaslongbeenregardedastheonlypracticalwaytousemillingcutters.Notlongago,climbmillingwasrecognizedasanacceptablemethodofoperation.Inclimbmilling，thecutterrotatesinthedirectionoffeed．

Theadvantagesofclimbmillingareasfollows:(1)?Feedcanfrequentlybedoubledoverconventionalmilling.(2)?Metalscanberemovedfastwithoutvibration.(3)?Finishcanbeconsiderablyimproved．

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Toollifemaybeprolonged．Fig.3Twomethodsofmilling(a)?Conventional(up)milling；(b)?Climb(down)milling

Bothconventionalmillingandclimbmillingarebeingemployed，becauseclimbmillingisnotapplicabletoanymillingjob．Climbmillingcanbeappliedonlywhenthemachineisofaheavy-dutytypeandbacklashhasbeeneliminated．Climbmillingisnotrecommendedforuseoncastironorforgings.Therefore,conventionalmillingremainsusefulinmillingwork． LEARNTOSPEAKMr.Liu: Goodafternoon,Mr.Xiong.Mr.Xiong: Goodafternoon,Mr.Liu.Mr.Liu: Ihavesometroublewithheattreatment.Couldyoutellme?Mr.Xiong: Whataretheproblems?Mr.Liu: Doyouknowwhatisthefunctionofheattreatment?Mr.Xiong: Yes.IthinkIsee.Heattreatmentisamethodbywhichtheheattreatercanchangethephysicalpropertiesofamaterial.Mr.Liu: Howmanytypesofheattreatmentarethere?

Mr.Xiong: Therearethreemainoperationsintheheattreatmentofsteel:hardening,temperingandannealing.

Mr.Liu: Howishardeningoperationdone?

Mr.Xiong: Thehardeningoperationconsistsofheatingthesteelaboveitscriticalrangeandthenquenchingitinasuitablemediumsuchaswater,brine,oil,orsomeotherliquid.Havingbeenhardened,themetalmustbegivenatemperingtreatmentwhichconsistsofreheatingthehardenedsteeltoatemperaturebelowthecriticalrange,thusproducingtherequiredphysicalproperties.Mr.Liu: Andwhatiscriticaltemperature?Mr.Xiong: Itisthetemperatureatwhichacertainchangetakesplaceinthephysical??conditionofthesteel.Mr.Liu: Whatisthepurposeofannealing?Mr.Xiong: Itcansoftenawork-pieceandrelieveinternalstressesproducedbymachining.Mr.Liu: Thankyoutellingmeaboutthese.Mr.Xiong: I’mgladtohavebeenofsomeservice.

conventionalmilling逆銑climbmilling 順銑upmilling 逆銑downmilling 順銑regard…as 認(rèn)為……是inasimilarway 同樣inthisway 這樣berecognizedas 被認(rèn)為是toollife 刀具壽命，刀具耐用度heavy-duty 重型的castiron 鑄鐵asfollows 如下heattreatment 熱處理heattreater 熱處理工作者physicalpropertiesofamaterial 材料的物理性能physicalpropertiesofamaterial 材料的物理性能hardenedsteel 淬硬鋼criticalrange 臨界點(diǎn)internalstress 內(nèi)應(yīng)力criticaltemperature 臨界溫度

1．Therearetwomethodsofmilling，i.e.conventionalorupmillingandclimbordownmilling．銑削方法有兩種：逆銑(即反向銑削)與順銑(即同向銑削)。

“or”可以表示“即”的意義，引出一個(gè)同位語。例如:Thecuttingspeedmustbereducedinthefirst,orroughingcut．在初切(即粗切)時(shí)，切削速度必須降低。

2．Inconventionalmilling，thecutterrotatesagainstthedirectionoffeed．逆銑時(shí)，銑刀旋轉(zhuǎn)方向與進(jìn)給方向相反。

“againstthedirectionof…”的含義是“與……的方向相反”。NOTES

3．Thismethodhaslongbeenregardedastheonlypracticalwaytousemillingcutters.這種銑削方法長期以來一直被認(rèn)為是使用銑刀的唯一切實(shí)可行的方法。

tov.短語可以用來修飾名詞。這里的“touse”用來修飾前面的“way”。又例如：

Conventionalmillingisnottheonlywaytousemillingcutters.逆銑不是使用銑刀的唯一方法。

4．Inclimbmilling，thecutterrotatesinthedirectionoffeed．順銑時(shí)，銑刀順著進(jìn)給方向旋轉(zhuǎn)。

“inthedirectionof…”的含義是“沿著……的方向”。

5．Climbmillingcanbeappliedonlywhenthemachineisofaheavy-dutytypeandbacklashhasbeeneliminated．只有在機(jī)床具有相當(dāng)?shù)膭傂郧议g隙也已消除的情況下，才能使用順銑。

“be+of+抽象名詞”可以表示“具有”或“屬于”等意義。句中“isofaheavy-dutytype”的含義是“是重型的(剛性好的)”。再看下面兩個(gè)句子：

Thesesupportsareofgreatrigidity.這些支架具有很大的剛性。

Thismachineisnotofaheavy-dutytype.這臺機(jī)器不屬于重型的。

EXERCISES1．DiscussthefollowingquestionsinEnglish:(1)?Whatistheconventionalmilling?(2)?Whatistheclimbmilling?(3)?Whatarethedifferencesbetweentheconventionalmillingandtheclimbmilling?2．UseEnglishforreplacingChineseoruseChineseforreplacingEnglish.(1)進(jìn)給方向(2)銑刀(3)粗切(4)?Methodofoperation(5)?Thedirectionoffeed(6)?PracticalwayREADINGMATERIAL RoughingandFinishingCut

Itiscustomary，inshoppractice,totakeatleasttwocutsmakeajobsmoothandaccurate．

Thefirstcuttotakeistoremoveexcessmetalfromthesurfaceofthework-pieceasrapidlyaspossible．Todothis，thecutshouldbeasdeepandthefeedascoarseasthework-pieceandthemachinetoolwillstand．Cuttingspeedshouldbeadjusteddownward,ifnecessary，topermitthis．Thefirst，orroughing，cutshouldbedeepenoughtosizethejob,withasuitableallowanceforafinishingcut,inonepasswheneverpossible．

Whenyouintendtoadjustthecuttingspeedorthefeedtoincreasetherateoftheproductiononamachinetool,itisadvisabletoincreasethefeedeventhoughthespeedmustbereducedsomewhat．Toincreasethefeedratherthanthecuttingspeedwillincreaseproductionwithoutacorrespondingincreaseinpowerconsumptionandtoolwear．

Thepurposeofthelast，orfinishing，cutistofinishawork-piecesmoothandaccurate.Toaccomplishthis，thecutshouldbeshallowandthefeedfineandcuttingspeedshouldbeincreasedmuchhigherthanfortheroughingcut.

Roughingandfinishingoperationsareusuallynotperformedonthesamemachine.Itisacommonpractice，forexample，torough-turnwork-piecesonalathe,and