lesson25 Third-Angle Projection

UnitElevenLesson25Third-AngleProjection教学目标及要求1.掌握课文中有关视图方面的专业词汇和专业术语；2.结合视图的相关专业知识阅读课文，提高翻译能力。重点1.视图的专业词汇和专业术语；2.翻译课文：第三角投影法的六视图；六视图中尺寸的标注；必要的视图。难句分析及翻译的基本技巧Part（Ⅳ）科技英语疑难结构及其翻译三、That结构教学思路设计时间分配（共100min）：1.讲解课文中的专业词汇和术语；2.讲解课后生词、大声朗读；3.翻译课文，注意穿插相关专业知识；4.分析难点句型，讲解相关语法和翻译技巧；5.学生答疑。ContentsBackgroundKnowledgeNewWordsandPhrasedTextAnalysisQuestionsGlossaryofTermsLanguagePoints&TranslatingTechniquesReadingMaterialsSummaryReferencesBackgroundKnowledge投影法简介第一角画法是将机件置于第Ⅰ角内，使机件处于观察者与投影面之间（即保持人→物→面的位置关系）而得到正投影的方法。我们以前讨论的投影画法都是第一角画法。第三角画法是将机件置于第Ⅲ角内，使投影面处于观察者与机件之间（即保持人→面→物的位置关系）而得到正投影的方法，如图所示。从图可以看出，这种画法是把投影面假想成透明的来处理的。顶视图是从机件的上方往下看所得的视图，把所得的视图就画在机件上方的投影面（水平面）上。前视图是从机件的前方往后看所得的视图，把所得的视图就画在机件前方的投影面（正平面）上。BackgroundKnowledge第一角画法第三角画法BackgroundKnowledge另外，ISO国际标准中规定，应在标题栏附近画出所采用画法的识别符号。第一角画法的识别符号为下图（a）所示，第三角画法的识别符号为下图（b）所示。我国国家标准规定，由于我国采用第一角画法，因此，当采用第一角画法时无须标出画法的识别符号。当采用第三角画法时，必须在图样的标题栏附近画出第三角画法的识别符号（如下图（b）所示）。(a)(b)NewWordsandPhrasedTerms：view视图projection投影perpendicular垂直draw制图arrange排列top顶端front正面align排列成一行rear后面adjacent接近的，毗邻的description绘制arrowhead箭头left-sideview左侧（视）图right-sideview右侧（视）图hiddenline(dottedline,dashedline)虚线beoutof(the)perpendicular倾斜fromtoptotail(toe)从头到尾，整个frontandrear在前后inaccordancewith按照lineupwith排成一行TextTheSixViewsAnyobjectcanbeviewedfromsixmutuallyperpendiculardirections,asshowninFigurea.Thesesixviewsmaybedrawnifnecessary,asshowninFigureb.Thesixviewsarealwaysarrangedasshown,whichistheAmericanNationalStandardarrangement.Thetop,front,andbottomviewsalignvertically,whiletherear,left-side,front,andright-sideviewsalignhorizontally.TodrawaviewoutofplaceisaseriouserrorandisgenerallyregardedasoneoftheworstpossiblemistakesindrawingThesixviewsTextNoteThatHeightisshownintherear,left-side,front,andright-sideviews;Widthisshownintherear,top,front,andbottomviews;Depthisshowninthefourviewsthatsurroundthefrontview—namely,theleft-side,top,right-side,andbottomviews.Eachviewshowstwooftheprincipaldimensions.Notealsothatinthefourviewsthatsurroundthefrontview,thefrontoftheobjectfacestowardthefrontview.Text1.AdjacentViewsareReciprocalIfthefrontviewinFigureThesixviewsisimaginedtobetheobjectitself,theright-sideviewisobtainedbylookingtowardtherightsideofthefrontview,asshownbythearrowRS.Likewise,iftheright-sideviewisimaginedtobetheobject,thefrontviewisobtainedbylookingtowardtheleftsideoftheright-sideview,asshownbythearrowF,thesamerelationexistsbetweenanytwoadjacentviews.Text2.NecessaryViewsAdrawingforuseinproductionshouldcontainonlythoseviewsneededforaclearandcompleteshapedescriptionoftheobject.Theseminimumrequiredviewsarereferredtoasthenecessaryviews.Inselectingviews,thedraftershouldchoosethosethatbestshowessentialcontoursorshapesandhavetheleastnumberofhiddenlines.TextAsshowninFigureThesixviews,threedistinctivefeaturesofthisobjectneedtobeshownonthedrawing:①roundedtopandhole,seenfromthefront;②rectangularnotchandroundedcorners,seenfromthetop;③rightanglewithfilletedcorner,seenfromtheside.Thethreeprincipaldimensionsofanobjectarewidth,height,anddepth.Intechnicaldrawing,thesefixedtermsareusedfordimensionstakeninthesedirections,regardlessoftheshapeoftheobject.Theterms“length”and“thickness”arenotusedbecausetheycannotbeappliedinallcases.Thetop,front,andright-sideviews,arrangedclosertogether,areshowninFigure25-1.Thesearecalledthethreeregularviewsbecausetheyaretheviewsmostfrequentlyused.三视图Text3.AlignmentofViewsErrorsinarrangingtheviewsaresocommonlymadebystudentsthatitisnecessarytorepeatthis:TheviewsmustbedrawninaccordancewiththeAmericanNationalStandardarrangementshowninFigureThesixviews.美国国家标准FigurePositionofviewsashowsanoffsetguidethatrequiresthreeviews.Thesethreeviews,correctlyarranged,areshowninFigurePositionofviewsb.Thetopviewmustbedirectlytotherightofthefrontview—notoutofalignment,asinFigurePositionofviewsc.Also,neverdrawtheviewsinreversedpositions,withthebottomoverthefrontortheright-sidetotheleftofthefrontview(Positionofviewsd),eventhroughtheviewsdolineupwiththefrontview.TextPositionofviewsQuestionsWhatisthethree-angleprojection?Whatarethedifferencesbetweenthree-angleprojectionandfirst-angleprojection?Listthesixprincipalviewsofanobject.Inadrawingthatshowsthetop,front,andright-sideview,whichtwoviewsshowdepth?Whichviewshowsdepthvertically?Whichviewshowsdepthhorizontally?Whatarethethreeprincipaldimensionsofanobject?GlossaryofTerms1.three-angleprojection2.third-angleprojection3.first-angleprojection4.drafting5.mechanicaldrawing6.standarddrawing7.standardcomponents(parts)标准件8.thesheet,drawingsheet,drawingpaper图样9.drawer,draftsman10.workingdrawing工作图，生产图11.detaildrawing,partdrawing12.sketch（layout,outline)13.assemblydrawing14.designdrawing15.blueprint16.engineeringdrawing,structuredrawing工程图，17.machineparts,mechanicaldevice,components零件，部件18.titleblock19.sectionalview20.orthographicprojection21.thetopview22.thefrontview主视投影（正视图，正面图）23.thesideview24.thebottomview25.frontview26.rear(back)view27.side(end)view28.three-viewdrawing29.profile,section(full-,half-,offset-,brokenout~,rotating~,inclined~,compoun