GD&T 福特汽车形位公差培训资料.ppt

GD&T 福特汽车形位公差培训资料.ppte ! e ! GD&T Introduction GD&T Introduction 2 Slide 2 1. Definition 1. Definition ? GD&T: Geometric Dimensioning and Tolerancing ? GD&T is a method for precisely defining the geometry of mechanical parts. It introduces tools which allow mechanical designers, fabricators, and inspectors to plex geometrical descriptions which are not otherwise able to be described in a defined language . Customer Customer 用户用户 Manufacturing Including. Supplier Manufacturing Including. Supplier 制造包括供应商制造包括供应商 Product&Tool Design Product&Tool Design 产品产品/ /模具设计模具设计 Engineering Engineering Drawing Drawing 工程图纸工程图纸Ф A B CM MM Geometric Characteristic Material Condition symbol Primary Datum Second Datum Tertiary Datum Geometric Tolerance 2. General Tolerancing and Principles 1) Definition ? Dimension Tolerance 公差:尺寸变化允许范围,等于最大极限和最小极限的差。? Geometric Tolerance 形位公差: 与部件的几何特征相关的公差形状、轮廓、定向、定位、跳动? Reference Dimension 参考尺寸:没有公差的尺寸,仅供参考,加括号或跟随 REF 。? Virtual Condition ( 实效状态) :指实际要素具有最大实体尺寸且相应中心要素的形位误差等于形位公差时的状态。以控制匹配部件的间隙或建立量具的要素尺寸。? External VC= MMC 尺寸+ Geometric Tolerance ? Internal VC= MMC 尺寸– Geometric Tolerance 2) Material Conditions 2) Material Conditions Material Conditions Symbol Maximum Material Condition Least Material Condition Regardless of Feature None M L? Regardless of Feature 独立原则( RFS): A geometric tolerance or datum reference applies at any increment of size of the feature within its size tolerance Note: No additional positional or form tolerance is available; no matter what the size. ( 形位公差与尺寸公差各自独立, 彼此无关, 分别满足各自的公差原则。 Envelope Principle (包容原则): 用最大/小实体来限定被测要素的实体。? The surface of the feature shall not extend beyond a boundary of MMC. If the feature is produced at its MMC limit of size. No form variation is permitted. ( 被测要素实体不得超越最大实体理想边界) ? The surface of the feature shall not extend a boundary of LMC. (被测要素实体不得超越最小实体理想边界) ? Where it is desire to permit a surface of a feature to exceed the boundary of MMC, a local note is