《尺寸注法.ppt》由会员分享，可在线阅读，更多相关《尺寸注法.ppt（33页珍藏版）》请在三一办公上搜索。
1、第 11 章 尺寸标注,尺寸是设计思想的重要组成部分,尺寸也是图样的重要组成部分。,11.1 概念:,尺寸:用特定单位所表示的长度值。图样上的尺寸是表示机件的理想状态的大小,图样上的尺寸也是机件的最后完工的大小。,在图样上尺寸的标注是以尺寸线、尺寸界线、数字表示的。,尺寸线:表示所要表示的对象的长度,用细实线表示,带有起迄标注。,在机械图样中推荐使用箭头,尺寸界线:表示尺寸范围的界线,用细实线。,H-字体高度,d-图中粗实线的宽度,数字:,11.2 基本注法:,线性尺寸:,角度尺寸:,圆和圆弧尺寸:,小尺寸:,其它尺寸:,11.3 尺寸标注的基本原则:,标注方法应符合国家标准的规定 尺寸标注应
2、具有完整性尺寸标注应清晰尺寸标注的合理性,要正确无误的反映机件的设计要求要考虑到尺寸标注后其加工的可行性和经济性要考虑到尺寸标注后其测量的方便性和准确性,支座的尺寸标注:,11.4 简化注法:,简化原则:力求制图方便信息检索迅速不致引起误解正确表达设计要求,11.5 典型零件的尺寸标注:,轴类零件,盘盖类零件,22,Dimensioning 零件图的尺寸标注,Datum features尺寸基准的选择Direct specifications of important dimensions重要的尺寸直接注出 Avoiding close dimension chains避免出现封闭的尺寸链Pr
3、oducing dimensions in accordance with machining sequence标注尺寸应符合加工顺序Only one link allowed between machined and non-machined surfaces同一个方向只能有一个非加工面与加工面联系 Exercises 练习题,请点击相应标题显示其内容,请点击鼠标左键显示后面内容,Datum features 尺寸基准的选择,When selecting a datum,one must consider the part position,function,assembling,posit
4、ion setting and measurement.Therefore,datum features should be determined according to the designs requirements,machining conditions,and measurements.在选择尺寸基准时,必须考虑零件在机器或部件中位置、作用、零件之间的装配关系以及零件在加工过程中的定位和测量等要求。因此,基准应根据设计要求、加工情况和测量方法确定。,Design datum This class includes datum planes or datum lines used t
5、o locate a given part inside other parts.设计基准 是用于确定零件在部件中工作位置的基准面或线。,Process datum This class includes datum plane or datum line used to machine or measure the parts.工艺基准 是零件在加工、测量时的基准面或线。,Determining datum features 尺寸基准的确定,请点击鼠标左键显示后面内容,Datum features 尺寸基准的选择,This section focuses on some general is
6、sues of dimensioning and some commonly used structures so that the dimensions will not only meet the design requirements but also other requirements to facilitate machining,measurement and inspection.使所标注的尺寸既能满足设计要求,又符合生产实际,便于加工、测量和检验。,Select the bottom surface D as thedatum for the dimension of the
7、 centerheight of the brackets axle hole.标注支架轴孔的中心高，应以底面D为基准,The dimensions of the two threaded holes select datum face B、C.底板两螺孔的定位尺寸,以B、C为基准,It is easy to use datum Eto measure the depth of the threaded hole.以E为基准测量螺孔的深度比较方便,Process datum工艺基准,Design datum设计基准:B、C、D,Length datum 长度基准 B,D Height datu
8、m 高度基准zzzz,Width datum宽度基准 C,Process datum 工艺基准:E,Bracket 支架,The dimensions of thethreaded holes select datum face C.螺孔的定位尺寸以C为基准,请点击鼠标左键显示后面内容,Direct specifications of important dimensions重要的尺寸直接注出,Important dimensions include the ones used to mount other parts,key relative positions and any other
9、information related to the function of the part.All of them should be directly specified when drawing parts.重要尺寸是指与其他零件相配合的尺寸、重要的相对位置尺寸、影响零件使用性能的其他尺寸，这些尺寸都应在零件图上直接注出。,Bracket 支架,The center height of the axle hole is an important dimension.So it should be directly specified.轴孔的中心高是重要尺寸应直接注出,Appropria
10、te 标注合理,Inappropriate 标注不合理,As shown in Fig,dimensions A,B,C and L form a close dimension chain.Since L=A+B+C,if dimension L has a constant error,dimensions for A，B and C must have very little error,which may lead to difficulties in machining.Therefore,close dimension chains should be avoided and th
11、e dimension with less importance should be removed.图中的尺寸A、B、C和 L 构成一个封闭的尺寸链。由于L=A+B+C，若尺寸L的误差一定,则A、B、C每个尺寸的误差就要定得很小。这样，就会使加工困难，所以应当避免封闭的尺寸链，将一个不重要的尺寸去掉。,Avoiding close dimension chains避免出现封闭的尺寸链,请点击鼠标左键显示后面内容,Avoiding close dimension chains避免出现封闭的尺寸链,Process datum 工艺基准,Length datum 长度基准,Height and w
12、idth datum高度、宽度基准,Length subsidiary datum 长度辅助基准,The close dimension chains should be avoided and the dimension with less importance should be removed.避免封闭的尺寸链，将轴的一个不重要尺寸去掉,(1)Dimensions should also be specified in accordance with machining sequence 标注尺寸应符合加工顺序,请点击鼠标左键显示后面内容,Producing dimensions in
13、accordance with machining sequence 标注尺寸应符合加工顺序,Precise dimensions 标注合理,Imprecise dimensions 标注不合理,Determine the location of the escape according to the dimension 36,and then machine the escape.按尺寸36mm定退刀槽的位置,加工退刀槽尺寸4mm,Turn the external diameter 18 and chamfer the end of the shaft.用车刀加工18mm的外圆和轴端倒角,
14、a)Escape加工退刀槽,b)External diameter加工外圆,(2)Dimensions should be specified for easy inspection 标注尺寸应便于测量,请点击鼠标左键显示后面内容,Producing dimensions in accordance with machining sequence 标注尺寸应符合加工顺序,Precise dimensions 标注合理,Imprecise dimensions 标注不合理,Dimensioning C is not convenient for measurement.尺寸C不便于测量,请点击鼠
15、标左键显示后面内容,Only one link allowed between machined and non-machined surfaces 同一个方向只能有一个非加工面与加工面联系,Imprecise dimensions 标注不合理,If dimensions are specified with three non-machined surfaces linked to A,it would be difficult to ensure the precision of linked dimensions 8,34 and 42 while machining the surfa
16、ce.三个非加工面B、C和D都与加工面A有联系,那么在加工A面时,就很难同时保证三个联系尺寸8,34和42的精度,Precise dimensions 标注合理,There are three non-machined surfaces along the height line:B,C,and D,in which only surface B and machined surface A have a link of dimension 8,which is appropriate.沿铸件的高度方向有三个非加工面B、C 和D，其中只有B 面与加工面A有尺寸8的联系，这是合理的,请点击题目显
17、示其内容,Exercises 练习题,1.Find out imprecise dimensions and correct it.找出标注不合理的尺寸，并更正之。,2.Fully dimension the drawing of bearing bracket，take the、as the design datum.注出轴承架全部尺寸,已知.为设计基准。,1.Find out imprecise dimensions and correct it.找出图中标注错误的尺寸，并按正确方法标注尺寸。,请点击鼠标左键显示后面内容,2,Fixing of bearing bracket轴承架安装图,2.Fully dimension the drawing of bearing bracket，take the、as the design datum.注出轴承架全部尺寸,已知.为设计基准。,Precise dimensions 标注合理,Imprecise dimensions 标注不合理,请点击鼠标左键显示解答内容,
