专业英语5-6市公开课获奖课件省名师优质课赛课一等奖课件.ppt

单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,*,本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。,单击此处编辑母版标题样式,本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。本资料仅供参考，不能作为科学依据。谢谢。本资料仅供参考，不能作为科学依据。,机 械 工 程 专 业 英 语,Unit 7 Tolerances and Fits,1/35,Tolerance,Allowance,Nominal size,Deviation,Bilateral Tolerance(Unilateral Tolerance),Basic deviation,Tolerance zone,BHS,BSS,2/35,1,Introduction,2,Tolerances,3,Fits,4,ISO System of Limits and Fits,3/35,Any manufacturer should have a thorough knowledge of the tolerances to increase the quality and reliability of a manufactured part with the least expense.,Deviations,of actual surfaces are divided into four groups to enable assessment,prescription and checking of the permitted inaccuracy during production:,1.Dimensional deviations;,（尺寸偏差）,2.Shape deviations;,（形状偏差）,3.Position deviations;,（位置偏差）,4.Surface roughness deviations;,（表面粗糙度偏差）,1,introduction,4/35,It is quite sufficient that the actual dimension of the part is found between two limit dimensions and permissible deviation is kept with production to ensure correct functioning of engineering products.,在很多情况下，零件实际尺寸介于两个极限尺寸之间，在制造过程中一直维持一个允许偏差以确保工程零件所含有功效。,Unnecessarily tight tolerances lead to high cost of manufacture resulting from more expensive manufacturing methods and higher,reject rates,.,无须要紧公差会造成因为昂贵制造方法和较高废品率所带来高制造成本。,1,introduction,5/35,Definitions.,Tolerance is the difference between the maximum and minimum size limits of a part.,Size(,尺寸,).,The size of an object or its mate is known as,nominal,basic,or design size,.,Allowance(,允差,).,The difference between the largest allowable shaft size and the smallest hole diameter is termed as the allowance.The quality of the fit is characterized by the allowance value.,Fit(,配合,).,Clearance,interference,or transition fit,refer to how the object fits an assembly.,Tolerances,2,6/35,Nominal Size(basic size)(,名义尺寸，基本尺寸,).,It is the designation used for general identification and usually expressed in common fractions.It is an exact,theoretical,size of a part from which limit dimensions are computed.The nominal size of a part should be selected from the preferred dimension series indicated by the national standard.,是用于识别一个表示，通惯用简分数形式给出。它表示一个零件准确理论尺寸，依据名义尺寸能够计算出极限尺寸。零件名义尺寸应该从国家标准要求优先尺寸系列中选取。,Limit size(,极限尺寸,).,It includes upper limit size and lower limit size which are allowable extreme size of a part.,Actual size(,实际尺寸,).,It is the measured size of the finished part.,Tolerances,2,7/35,Deviations(,偏差,).,The upper and lower deviations obtained by subtracting basic size from limit size.,Allowance(,允差,).,The intentional difference between the maximum material limits of mating parts.,This is a minimum clearance(positive allowance)or maximum interference(negative allowance)between mating parts.,配合零件最大极限尺寸间差值，它是配合零件之间最小间隙量（正允差）或最大过盈量（负偏差）。,Tolerances,2,8/35,Bilateral Tolerances(,双边公差,).,A bilateral tolerance is a tolerance in which variation is permitted in both directions from a specified dimension.,双边公差允许相对于基本尺寸沿两个方向变动。,The actual size of the object may be larger or smaller than the stated size limitation if there can be equal variation in both directions.The plus and minus limitations combine to form a single value.,假如在两个方向上含有相同变动量，零件实际尺寸就有可能大于或小于标注尺寸极限。正负极限就组成一个数值。,Tolerances,2,9/35,Unilateral Tolerances(,单边公差,).,A unilateral tolerance is a tolerance in which variation is permitted only in one directions from a specified dimension.,单边公差是指相对于名义尺寸只能沿一个方向变动。,Unilateral tolerance expression has the advantage that they are easier to check on drawings and that the change in the tolerance can be made with the least,disturbance,to other dimensions.,单边公差表示方式优点是用它来检验图纸比较方便。,Tolerances,2,10/35,How mating parts or assemblies fit together with component parts,is referred to,as fit,which includes clearance fit,interference fit,or transition fit,see Fig.7.3.,Fit is general range of tightness resulting from the application of a specific combination of allowance and tolerances in the design of mating parts.,Fits,3,The types of fitting,Clearance fit,间隙配合,Interference fit,过盈配合,Transition fit,过渡配合,11/35,Clearance fit.,it is a fit enabling a clearance between the hole and shaft in the coupling.The lower limit size of the hole,is greater or at least equal to,the upper limit size of the shaft.,Interference fit.,It is a fit always ensuring interference between the hole and shaft in the coupling.The upper limit size of the hole is smaller or at least equal to the lower limit size of the shaft.,Transition fit.,It is a fit where(depending on the actual sizes of the hole and shaft)both clearance and interference may occur in the coupling.Tolerance zones of the hole and shaft partly or completely interfere.,Fits,3,12/35,下偏差,公差带,+0.008,-0.008,+0.008,+0.024,-0.006,-0.022,公差带图,：,作用：直观地表示出了,公差大小及公差带相对于零线位置。,50,+0.024,+0.008,50,-0.006,-0.022,0,0,基本尺寸,50,例,:,500.008,上偏差,13/35,Clearance fit,Fit with clearance(including minimum clearance zero).,Maximum clearance,Minimum limit of size,Maximum limit of size,Minimum clearance,Maximum clearance,The tolerance zone of hole is above that of the shaft.,Minimum limit of size,Maximum limit of size,14/35,Interference fit,Minimum interference,Maximum interference,The tolerance zone of hole is below that of the shaft.,Fit with interference(including minimum Interference zero),Maximum limit of size,Minimum limit of size,Maximum,interference,15/35,Transition fit,Fit having clearance of interference.,The tolerance zone of hole overlaps that of the shaft.,16/35,The ISO system of tolerances and fits can be applied in tolerances and deviations of smooth parts and for fits created by their coupling.It is used particularly for cylindrical parts with round,sections,.Tolerances and deviations in this standard can also be applied in smooth parts of other sections.,ISO,公差和配合体系能够用于光滑零件公差和偏差以及连接件配合确实定，尤其用于圆形截面圆柱形零件。该体系中公差和偏差也能够用于其它形状截面零件。,4,ISO System of Limits and Fits,17/35,Similarly,the system can be used for coupling(fits)of cylindrical parts and fits with parts having two parallel surface(e.g.fits of keys in grooves).The term“shaft”,used in this standard has wide meaning and serves for,specification,of all outer elements of the part,including those elements which do not have cylindrical shapes.Also,the term“hole”can be used for specification of all inner elements regardless of their shape.,一样地，该标准还能够应用于圆柱形零件连接（配合）及含有两平行表面零件配合（如键和键槽配合）。标准中采取“轴”这一词有广泛含义，它用于说明零件全部外部元素，包含那些不是圆柱形表面元素。而“孔”这个词则能够指不考虑形状零件全部内部元素。,4,ISO System of Limits and Fits,18/35,In order to meet the requirements of various production branches for accuracy of the product,the system ISO implements 20 grades of accuracy.Each of the tolerances of this system is marked“IT”with attached grade of accuracy(IT01,IT0,IT1 IT18).,Note:,IT is an acronym for,International Tolerance.,为了满足不一样生产部门对产品精度需求，,ISO,标准要求了,20,级精度等级。,4,ISO System of Limits and Fits,19/35,The tolerance zone is defined as,annular zone,（环形区域）,limited by the upper and lower limit dimensions of the parts.The tolerance zone is therefore determined by the,amount of,the tolerance and its position related to the basic size.The position of the tolerance zone,related to the basic size(zero line),is determined in the ISO system by a so-called,basic deviation,.,公差带是上极限尺寸和下极限尺寸间环形区域。所以，公差带由公差值及其与基本尺寸相对位置所决定。,ISO,标准中公差带相对于基本尺寸（零线）位置是由基本偏差决定。,4,ISO System of Limits and Fits,20/35,21/35,The system ISO defined 28 classes of basic deviations for holes.These classes are marked by capital letters(A,B,C ZC).The tolerance zone for the specified dimensions is prescribed in the drawing by a tolerance mark,which consists of a letter marking of the basic deviation and a numerical marking of the tolerance grade(e.g.H7,H8,D5,etc.).,对于孔，,ISO,标准定义了,28,类基本偏差，由大写字母,(A,B,C),表示。在图样中要求尺寸（设计尺寸）公差带是经过公差代号表示，它由表示基本偏差字母和表示公差等级数字组成。,Though the general sets of basic deviations and tolerance grades can be used for prescriptions of hole tolerance zone by their mutual combinations,in practice only a limited range of tolerance ones is used.,4,ISO System of Limits and Fits,22/35,Though the,general sets,of basic deviations and tolerance grades can be used for prescriptions of hole tolerance zone by their mutual combinations,in practice only a limited range of tolerance ones is used.,尽管基本偏差和公差等级,全部集合,能够经过相互组合确定孔公差带，不过在实际应用中，只采取公差带中一小部分。,4,ISO System of Limits and Fits,23/35,Basic deviation,R,S,T,P,C,D,EF,FG,CD,E,H,Y,A,B,G,JS,K,M,N,U,V,X,Z,ZA,ZB,ZC,F,Basic size,zero line,0,+,-,Hole,J,0,+,r,a,fg,d,ef,cd,b,h,js,j,k,m,n,p,s,t,u,x,z,za,zb,zc,g,e,c,f,v,y,Basic size,zero line,0,-,Shaft,0,24/35,Although there can be generally coupled parts without any tolerance zones,only two methods of coupling of holes and shafts,namely basic hole system and basic shaft system,are recommended due to constructional,technological and economic reasons.,尽管存在没有公差带普通装配零件，基于结构、技术和经济原因，只推荐两种孔和轴配合方法，即基孔制和基轴制。,Basic hole system(BHS):,A system of fits in which the design size of the hole is the basic size and,the allowance,if any,is applied to the shaft.,Basic shaft system(BSS):,A system of fits in which the design size of the shaft is the basic size and,the allowance,if any,is applied to the hole.,4,ISO System of Limits and Fits,25/35,BHS:,When specifying the tolerance for a hole and cylinder and determining their dimensions,you should begin calculating by assuming either the minimum hole or maximum shaft size if they are to fit together well.,当给一个孔或圆柱面指定公差和决定尺寸时，需要假设最小尺寸孔或最大尺寸轴配合良好，并进行计算。,The desired clearances and interferences in the fit are achieved by combinations of various shaft tolerance zones with the hole tolerance zone“H”.,配合中所需要间隙和过盈量能够经过不一样轴公差带与代号为“,H”,孔公差带组合来实现。,4,ISO System of Limits and Fits,26/35,basic size,25 H7/g6,basic dev.,for the hole,IT grade,for the hole,basic dev.,for the shaft,IT grade,for the shaft,tolerance zone,Basic.Dev.,BHS,27/35,allowance:0.003,the minimum hole size(basic size):1.500,tolerance:0.002,What is the maximum diameter of the shaft?(clearance fit or interference fit),4,ISO System of Limits and Fits,hole,C,min,shaft,Allowance of the fit corresponds to,maximum material condition,(,C,min,).,hole,shaft,Allowance of the fit corresponds to,maximum material condition,(,I,max,).,28/35,To calculate the maximum diameter of the shaft,assume,an allowance of 0.003,and subtract that from the basic hole size.Arbitrarily selecting,a tolerance of 0.002,for both the hole and shaft gives a maximum hole(1.502)and minimum shaft(1.495).The minimum clearance fit is the difference between the smallest hole(1.500)and the largest shaft(1.497)or 0.003.,By adding the allowance to the basic hole size,the maximum shaft size of an interference fit is obtained.To convert basic hole size to basic shaft size,we subtract the allowance for a clearance fit or add it for an interference fit.,4,ISO System of Limits and Fits,29/35,tolerance zone,Basic.Dev.,Basic.Dev.,BHS,BSS,basic size,basic size,hole,tolerance zone,shaft,hole,shaft,tolerance zone,30/35,Any manufacture should have thorough knowledge of the tolerances and fits to increase the quality and reliability of a manufactured part with the least expense.The increase,compatibility,（交换性）,of a certain product with mating parts by difference manufacturers makes it more,viable,in market competition.Moreover,a knowledge of tolerances and fits is essential for manufacturing with least material wastage,and hence good tolerancing principles followed by manufacturers are essential in,reaping,profits.,制造商应该具备公差和配合全方面知识以期在最小成本下提升产品质量和可靠性。由不一样制造商生产包含配合件产品交换性越好其市场竞争力越强。另外，在制造过程中要使材料浪费率最低，公差和配合知识尤为主要，制造商要取得最大利益，必须要恪守合理确定公差标准。,4,ISO System of Limits and Fits,31/35,Tolerance on the Fit,Tolerance on the fit is defined as the sum of the tolerance on the hole and tolerance on the shaft.,C,min,C,max,I,max,I,min,C,max,I,max,clearence,interference,t,ransi,tion,32/35,For a nominal diameter of 25 mm and for a fit specification of H7/j5 determine the following:,Type of the tolerancing system,Tolerance on the hole,Tolerance on the shaft,Upper and lower limits of the hole(,D,max,D,min,),Upper and lower limits of the shaft(,d,max,d,min,),Type of the fit,Tolerance on the fit,Allowance,Example,33/35,a),H7/j5,Basic Hole System,b),D,=25 mm,from the given table:,nominal size,H7,j5,+,-,c),34/35,d),e),f),Interference fit.,g),Tolerance on the fit:,or,h),Allowance=,I,max,=5,m,m.,35/35,