零件图的尺寸标注.ppt

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 Producing 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, position 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 to 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 issues 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 the datum for the dimension of the center height 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 E to 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 datum 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 the threaded 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 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,Appropriate 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 the 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 width 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 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,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 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,Precise dimensions 标注合理,Imprecise dimensions 标注不合理,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,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 surface. 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,请点击题目显示其内容,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。,本 小 节 结 束,谢谢您的认真学习！,退出,前一页,1. Find out imprecise dimensions and co