半径和控制半径

半径和控制半径 电子发烧友 电子技术论坛 半径和控制半径 Radius and Controlled Radius 半径 Radius 半径是从圆心到圆弧或圆的面的一条直线。半径的符号是R。符号R A radius is a straight line extending from the center to the surface of an arc 使用时，就产生了由两条圆弧(最小半径和最大半径)定义的公差带。 or a circle. The symbol for a radius is “R”. When the “R” symbol is used, it 零件表面必需位于公差带内。 create a zone defined by two arcs(the minimum and maximum radii). The part surface must lie within this zone. 控制半径 控制半径是不准许平直和相反的半径。控制半径的符号为CR。当CRControlled Radius 使用时，就产生了由两条圆弧(最小半径和最大半径)定义的公差带。 A controlled radius is a radius with no flats of reversals allowed. The 零件表面位于新月型的公差带内，并且不是平直和相反圆弧。 symbol for controlled radius is “CR”. When the “CR” symbol is used, it creates a tolerance zone defined by two arcs (the minimum and maximum radii). The part surface must be within the crescent-shaped tolerance zone and be an arc without flats or reversals. 6 6 电子发烧友 电子技术论坛 电子发烧友 电子技术论坛 统计公差符号 Statistical Tolerancing Symbol 统计公差符号表示被应用的尺寸公差是由统计方法建立的.。当这个符号用The statistical tolerancing symbol denotes that the dimension of 在图纸上时，零件形体用统计制程管制进行生产。该符号用注记标在后面， tolerancing to which it is applied was established by statistical methods. 如下图所示: When this symbol is used on a drawing, the part feature should be manufactured using statistical process controls. The symbol is accompanied by a note as shown in the example below. 形体定义为统计公差时，生产时用统计制程管制。 统计公差符号适用于尺寸公差或一个形位公差控制的公差值。 FEATURES IDENTIFIED AS STATISTICALLY TOLERANCED SHALL BE PRODUCED WITH STATISTICAL PROCESS CONTROLS. The statistical tolerance symbol may be applied to a dimensional tolerance or to the tolerance value of a geometric control. 7 7 电子发烧友 电子技术论坛 电子发烧友 电子技术论坛 形体控制框 Feature Control Frame 形体控制框包括: The feature control frame consists of: 1. 控制特性(几何特性) 1. Type of control (geometric characteristic) 2. 公差带尺寸 2. Tolerance zone size. 3. 公差带修正表示: 3. Tolerance zone modifiers denote: , The tolerance zone shape (). , 公差带形状 (). , The diameter () symbol denotes a cylindrical tolerance zone. , 直径 () 符号表示圆柱公差带。 球径 () 符号表示球形公 The spherical diameter () symbol denotes a spherical 差带 , 公差应用以下条件 tolerance zone. , The conditions under which tolerance applies () () 4. 选用参考基准和参考基准修正 5. 参考基准修正 4. Datum references if applicable and any datum reference modifiers. 5. Datum references modifiers. 电子发烧友 电子技术论坛 8 8 电子发烧友 电子技术论坛 一般规则 General Rules 规则1:单独形体尺寸规则 Rule #1 Individual Feature of Size Rule 常常参考为包容原则和在MMC时的理想形状。 Often referred to as the “envelope principle” or “perfect form at MMC” 规则1 规定在仅指定尺寸公差的地方,尺寸界限也控制形体界限 Rule #1 states where only a tolerance of size is specified, the limits of size 规则1 例子 also control the limits of form. Rule #1 Example The Envelope Principle 包容原则 The examples above are affected by Rule #1 (or the envelope principle) as 以上都是规则1的例子(或包容原则)，详述见a，b，c三段 described in paragraphs a, b,& c. a:形体上各表面，不得超出在最大实体下的边界。该边界是图纸所要表达 a: The surface(s) of a feature shall not extend beyond a boundary (envelope) 的实际几何形状。如果形体已达到最大实体状态尺寸，那么形体形状就不 of perfect from at MMC. This boundary is the true geometric form 准许有任何偏差。 represented by the drawing. No variation in form is permitted if the feature 9 is produced at its MMC limit of size. 电子发烧友 电子技术论坛 9 电子发烧友 电子技术论坛 General Rules (Cont.) 一般原则(续) The Envelop Principle (Cont.) 包容原则(续) b. where the actual local size of a feature has departed from MMC toward LMC, a b:在特征实际尺寸偏离最大实体状态趋向最小实体状态的地方，准许特征 variation in form is allowed equal to the amount of such departure. 在等于此偏离量的范围内变动。 C. there is no requirement for a boundary of perfect from at LMC. Thus, a C:对在最小实体状态时的理想边界没有要求。因此，当达到尺寸的最小实 feature produced at its LMC limit of size is permitted to vary from true form to the 体状态时，准许特征形状至最大实体状态下所准许的理想边界之间做变 maximum variation allowed by the boundary of perfect form at MMC 动。 Rule #1 only applies to the size. Rule #1 does not affect the location, orientation, or 规则1仅适应于尺寸，并不影响个特征间的位置，方向或相互关系。因 interrelationship between features of size. Therefore, the relationship between individual 此，单个特征间的相互关系必须定义以避免图纸要求的不足;通常用几 features must be defined to avoid incomplete drawing speciations; geometric tolerances 何公差来控制特征间的位置，方向和相互关系。 are often used to Control the location, orientation, or interrelationship between features. 如何不考虑规则1 How to Override Rule #1 通过控制形体轴(或面)的直线度，可以不考虑规则1。见35页例子。 Rule #1 can be overridden by applying a straightness control to an axis (or plane) of a feature of size. An example is shown on page 35. 规则1的例外 Exception to Rule #1 规则1有两个例外: There are two exceptions to Rule #1: 1, 非刚性零件 1. Non-rigid parts 2，原料尺寸，比如薄片，管材等 2. Stock sizes, such as sheets, tubing. etc. 规则2 (所有适用的几何公差规则) Rule #2 (All applicable geometric tolerances rule) 独立原则应用时，对于公差状态，参考基准或两者都没有实体状态调整。 RFS applies, to the tolerance condition, datum references, datum references, or both, where no material condition modifier is specified. 10 10 电子发烧友 电子技术论坛 电子发烧友 电子技术论坛 一般原则(续) General Rules (Cont.) 螺纹 Screw Treads 螺纹上规定的方向，位置的公差及参考基准，都是应用在螺纹节圆轴线上Each tolerance of orientation, tolerance of position or datum reference for a 的。在例外的情形，需要应用在螺纹上特定的特征(比如大径或小径)screw thread applies to the axis of the tread derived from the pitch cylinder. 上，应该放在特征控制框下方或靠近基准特征符号处，如: Where an exception to this practice is necessary, the specific feature of the screw thread (such as MAJOR DIA or MINOR DIA) shall be stated under the feature control frame or adjacent to the datum feature symbol, as applicable. 齿轮和齿条 齿轮，齿条上规定的方向，位置公差及参考基准，必须指明是应用 Gears and Splines 在齿轮或齿条上哪一个特征上的(比如大径，节径或小径)。这些说明文Each tolerance of orientation, tolerance of position or datum reference 字标在特征控制框或基准特征符号的下面，如: specified for features, such as gears and splines, must designate the specific feature of the gear of spline to which each applies (such as MAJOR DIA,PITCH DIA, (PD), or MINOR DIA). This information is stated under the feature control frame or under the datum feature symbol, as applicable. 11 11 电子发烧友 电子技术论坛 电子发烧友 电子技术论坛 基准 Datums 参考基准坐标系 Datum Reference Frame 零件设计最重要的那些基准特征，或者这些特征上指定的部分被选用来定Sufficient datum features, those most important to the design of a part, or 位零件，由此而产生的三个相互垂直的平面通称为参考基准坐标系(看designated portions of these features are chosen to position the part in 下图)。这个参考坐标系是理论上的，而不是零件上的。因此，建立一种relation to a set of three mutually perpendicular planes, jointly called datum 方式从实际零件特征来模拟理论参考坐标系是非常必要的。 reference frame (see figure below). This reference frame exists in theory only and not on the part. Therefore, it is necessary to establish a method of simulating the theoretical reference frame from the actual features of the part (fig). This simulation is accomplished by positioning specifically identified features in contact with appropriate datum simulators, in a stated order of precedence, to restrict motion of a part and to relate the part adequately to the datum reference frame. 12 12 电子发烧友 电子技术论坛 电子发烧友 电子技术论坛