《機械專業(yè)英語》課件第6章

Unit6TEXTLEARNTOSPEAKNEWWORDSANDEXPRESSIONSNOTESEXERCISES

READINGMATERIALPROFESSIONALWORDSANDPHRASES TheDesignofJigsandFixtures

Holdingdevicesmaybeclassifiedasjigsorfixtures.Ajigisawork-piecelocatingandholdingdevicewhichpositionsandguidesorcontrolsacuttingtool.Afixtureisawork-piecelocatingandholdingdeviceusedwithmachinetools,inspection,weldingandassembly.Itdoesnotcontrolthepositionofthetoolorinstrumentwhichisbeingused.Inmanyinstancesgaugeblocksmaybeprovidedforsettingthedepthorpositionofthecuttingtool.TEXTFig.6-1Drillingjig

Thedesignerapproachesthedesignprojectbyfirstbecomingfullyawareofallcriticaldimensionsandsurfaces.Ifpossible,heshouldalsoknowhowthepartfitsintothemainassembly.Onceheisfamiliarwiththespecialfunctionalrequirementsanddimensions,hecollectsthedatawhichmayhaveaneffectonhisdesign.Datasuchastypeofmaterial,physicalproperties,weight,andthecharacteristicsoftherawmaterial.Otherinformationwhichcouldaffectthetypeoffixturetobebuiltistheproductionquantities,lotsizes,etc.

Nextthedesignerdetermineswhetherfixturesalreadyintheplantcanbealteredandusedforhisjob.Hemustalsoconsiderthepossibilityandadvisabilityofusingstandardholdingdevicessuchasvises,parallelsandclamps.

Onceitisdecidedthataseriesofoperationsaretobedonewithnewlydesignedfixtures,thedesignercombinesasmanyoperationsintoonefixtureaspossible.Fig.6-2Millingfixture LEARNTOSPEAKMr.Zhang: Goodmorning,Mr.Cheng.Mr.Cheng: Goodmorning,Mr.Zhang.Mr.Zhang: Whatareyoudoing?Mr.Cheng: Iammachiningawork-piece.Mr.Zhang: What’sthis?Mr.Cheng: Itisafixture.Mr.Zhang: Whatcanitdo?Mr.Cheng: Wecanuseittolocateandholdthework-piecewhenitismachined.Mr.Zhang: Isthefixtureonlybeusedtomachine?Mr.Cheng: No.Infacttherearemanykindsoffixtureandtheycanalsobeusedforinspection,weldingandassembly.Mr.Zhang: Whatareitsadvantages?Mr.Cheng: Wecanimprovetheproductprecisionandreducetimeassumptionoflocatingthework-piece.Mr.Zhang: It’sverykindofyoutotellmeaboutthese.Mr.Cheng: That’sallright.classifiedas 分為locatingandholdingdevice定位和夾緊裝置gaugeblock 量塊criticaldimension 重要尺寸physicalproperty 物理性能rawmaterial 原材料

NOTES1．Holdingdevicesmaybeclassifiedasjigsorfixtures.夾持裝置可以分為鉆模和夾具。

beclassifiedas 分為

像這類后面用as引出的補語的動詞還有：

characterize…as 表示……的特征為

consider…as 認為……是

define…as 把……定義為

describe…as 把……描繪成

regard…as 認為……是

use…as 把……用作2．Thedesignerapproachesthedesignprojectbyfirstbecomingfullyawareofallcriticaldimensionsandsurfaces.設計師首先通過全面了解零件的關鍵尺寸和表面來決定設計方案。

becomeawareof發(fā)覺，了解

“firstbecomingfullyawareofallcriticaldimensionsandsurfaces”這一V-ing短語與“by”一起構(gòu)成介詞短語，修飾謂語動詞，表示方法、手段。3．Datasuchastypeofmaterial,physicalproperties,weight,andthecharacteristicsoftherawmaterial.像材料的類型、物理性能、重量以及原材料的特性等。

這一部分雖然以大寫字母開始，以句號結(jié)束，但不是句子，而是前面句中data的同位語，作進一步的說明。

4．Nextthedesignerdetermineswhetherfixturesalreadyintheplantcanbealteredandusedforhisjob.接著，設計師確定廠里已有的夾具是否能改動一下，以供使用。

Next(本句中用作adv.)有兩種用法：

(1)?adj.其次的，下(一個的)。例如：

Thework-pieceismovedtothenextstation.工件送到下一個工位。

(2)?adv.其次，然后。例如：

Nexttheholeisreamed.然后鉸孔。

5．Hemustalsoconsiderthepossibilityandadvisabilityofusingstandardholdingdevicessuchasvises,parallelsandclamps.他還必須考慮是否可能或值得利用虎鉗、平行墊鐵和壓板等標準夾持裝置。

這里的“parallel”是名詞，意為“平行墊鐵”?！癱lamp”也是名詞，意為“壓板”、“夾鉗”。EXERCISES1．PutthefollowingintoChinese:(1)?Jigsandfixtures(2)?Markout(3)?Atrialwork-piece(4)?Interchangeable(5)?Erroraccumulate(6)?Thecuttingforce(7)?Thedegreeoffreedom(8)?Thethreemutuallyperpendicular(9)?Thenecessityofmakingprecisionjigs(10)?Positionthework-piecewithrespectthemachinemovement

2．Readthetextcarefullyandanswerthefollowingquestions:

(1)?Whatisajig?

(2)?Whatisthedifferencebetweenthejigsandfixtures?

(3)?Whythework-piecemustbemarkedoutbeforemachinestart?

(4)?Canyousaysomeadvantagesofjigsandfixtures?Givesomeexamples.

(5)?Whatisthedegreeoffreedom?

3．TranslatethefollowingEnglishintoChinese:

Jigsareworkholderswhicharedesignedtohold,locateandsupportawork-piecewhileguidingthecuttingtoolthroughoutitscuttingcycle.Fixturesandjigsarealikebecausetheybotharedevicestoensurethatthework-pieceiscorrectlylocatedandclamped.Buttherestillaresomedifferencesbetweenthem.Unlikejigs,fixturesdonotguidethecuttingtool,butrather,provideameanstoreferenceandalignthecuttingtooltothework-piece.Forthemostpart,fixturesaredesignedtowithstandmuchgreaterstressedandtoolforcesthanjigs,andarealwayssecurelyclampedtothemachine.READINGMATERIAL

IntroductiontoMachineDesign

Machinedesignistheapplicationofscienceandtechnologytodeviseneworimprovedproductsforthepurposeofsatisfyinghumanneeds.Itisavastfieldofengineeringtechnologywhichnotonlyconcernsitselfwiththeoriginalconceptionoftheproductintermsofitssize,shapeandconstructiondetails,butalsoconsidersthevariousfactorsinvolvedinthemanufacture,marketinganduseoftheproduct.

Peoplewhoperformthevariousfunctionsofmachinedesignaretypicallycalleddesigners,ordesignengineers.Machinedesignisbasicallyacreativeactivity.However,inadditiontobeinginnovative,adesignengineermustalsohaveasolidbackgroundintheareasofmechanicaldrawing,kinematics,dynamics,materialsengineering,strengthofmaterialsandmanufacturingprocesses.

Asstatedpreviously,thepurposeofmachinedesignistoproduceaproduct,whichwillserveaneedforman.Inventions,discoveriesandscientificknowledgebythemselvesdonotnecessarilybenefitpeople;onlywhentheyareincorporatedintoadesignedproductwillabenefitbederived.Itshouldberecognized,thereforethatahumanneedmustbeidentifiedbeforeaparticularproductisdesigned.

Machinedesignshouldbeconsideredtobeanopportunitytouseinnovativetalentstoenvisionadesignofaproduct,toanalyzethesystemandthenmakesoundjudgmentsonhowtheproductistobemanufactured.Itisimportanttounderstandthefundamentalsofengineeringratherthanmemorizemerefactsandequations.Therearenofactsorequationswhichalonecanbeusedtoprovideallthecorrectdecisionsrequiredtoproduceagooddesign.Ontheotherhand,anycalculationsmademustbedonewiththeutmostcareandprecision.Forexample,ifadecimalpointismispla