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1、Geometric Dimensioning and Tolerancing (GD另一方 面,它也體現了被測要素的功能要求.5What is GD&T?The Geometric Tolerance is the amount which true elements are permitted to vary from an ideal element. 指被測實際要素對其理想要素的變動量.6Introduction(3)公差的分類Classification of Tolerance (1). 尺寸公差Dimension Tolerance (2). 表面形貌公差(表面粗糙度)Surfac
2、e Tolerance (Roughness) (3). 形狀和位置公差Geometric Tolerance7Introduction(4)In 1966, the first united standard was published by the American National Standards Institute (ANSI), known as ANSI Y14.5. It was updated in 1973,1982,1994. 形位公差標準的演變歷程: 最先應用于軍事 工業, 以美國與英國應用最為廣泛,各種不同 的組織相繼出版了各種不同的標準.1966年, 第一部統一的
3、標準- ANSI Y14.5出版,並經 歷1973,1982和1994三次改版. 8Introduction(5)優點: Advantages:n有利于增強彼此之間的交流Improves communicationsn有利于產品的設計Better product designsn有利于零件制造公差的盈餘Production tolerances increased9專門術語Terminology101.尺寸要素 & 非尺寸要素Feature-of-size and Featuren由一定大小的尺寸確定的要素稱為 尺寸要素A feature-of-size is one cylindrical
4、of spherical surface or a set of parallel surfaces, each of which is associated with a size dimension.n平面. 直線等沒有大小的要素稱為 非尺寸要素A feature is a general term applied to a physical portion of a part, such as a surface, hole, or slot. 11ABCDE非尺寸要素Feature: D,E 尺寸要素Feature-of-size: A,B,CExplain:122.理想邊界狀態Vir
5、tual Conditionn由設計給定的具有理想形狀的極限包 容面, 稱為理想邊界狀態.Virtual condition is the theoretical extreme boundary of a feature-of-size generated by the collective effects of MMC and any applicable geometric tolerances.133.盈餘公差Bonus Tolerancen盈餘公差是指實際尺寸偏離最大實體尺寸 的大小.A bonus tolerance equal to the amount that the fea
6、ture-of- size departs from MMC. Feature sizeStraightness Tol.Bonus Tol.Total Tol. 20.5MMC0.200.220.40.20.10.320.30.20.20.420.20.20.30.520.10.20.40.620.0LMC0.20.50.7 14Geometric characteristicsymbolModifierDenotes shapeof Tolerance zoneModifierDenotes Material conditionDatum referencesTolerance value
7、4.形位公差框格Feature Control Frame155.附加符號Modifying symbolsTerm Abbreviation SymbolMaximum Material Condition MMC M Least Material Condition LMC LRegardless of Feature size RFS S166.理論正確尺寸Basic DimensionsA basic dimension is a numerical value used to describe theoretically exact characteristics of a feat
8、ure or datum target.理論正確尺寸:在設計過程中用來確定 要素的精確位置,在檢測過程中作為計 算形位誤差的依據.26.017分類 & 原則Classification and Rules18五大類共13小項(對稱度除外)(Except for Symmetry)分 類 Classification 19基本原則(1-1) Fundamental Rules n Rule #1 (Envelope rule)For features-of-size, where only a size dimension is specified, the surfaces shall not
9、 extend beyond a boundary (envelope) of PERFECT FORM AT MMC.nRule #1 (包容原則)n尺寸公差與形位公差相互有關的一種要求 .采用包容要求的尺寸要素其實際輪廓 應遵守最大實體邊界,即其體外作用尺寸 不超出最大實體尺寸,且其局部實際尺寸 不超出最小實體尺寸.20Applied to an external feature-of-sizeApplied to an internal feature-of-size基本原則(1-2) Fundamental Rules 21基本原則(2) Fundamental Rules nRule
10、 #2 (獨立原則)獨立原則就是圖樣上給定的各個尺寸和形 狀.位置要求都是獨立的,應該公別滿足各 自的要求.獨立原則是尺寸公差和形位公差相互關系 遵循的基本原則.22nRule #3 (位置度公差應用原則)對于位置度公差,基準要素為尺寸要素時, 基准符號后必須接有 S , L , M 等符號.nRule #2 (Tolerance of position rule) For tolerance of position, S , L , or M must be specified in the feature control frame with respect to the toleranc
11、e value, datum reference, or both, as applicable.S,L,or M must be specified If the datum is a feature-of-size基本原則(3) Fundamental Rules 23nRule #4 (除位置度以外幾何公差之應用原則 )對于位置度以外的幾何公差,沒有特殊標識 的以RFS(不相關原則)處理.nRule #3 (Other than tolerance of position rule)For other than a tolerance of position, RFS applies w
12、ith respect to the tolerance, datum reference, or both, where no modifier is specified. MMC must be specified in the feature control frame when it is appropriate and desired. RFS applies RFS applies MMC is specified基本原則(4) Fundamental Rules 24定義 與 應用 Definition and Application251.Form ControlsForm c
13、ontrols never use a datum reference.261.1 Flatness 1.1.1 Definitionn實際被測要素對理想平面的允許變動.A flatness tolerance is the amount which surface elements are permitted to vary from a true plane.距離為平面度公差值t的兩平行平面 之間的區域.A flatness tolerance zone is the distant between two parallel plane spaced apart a distance eq
14、ual to the flatness tolerance value.270.1wide flatness tolerance zoneThe surface must lie between two parallel planes 0.1 apartLimits set by Rule #11.1.2 Application1.1 Flatness281.2 Straightnessn根據不同的設計要求,直線度公差可以有幾種不 同形狀的公差帶. A straightness control has a different tolerance zone depending upon its
15、application to a feature or to a feature-of-size.1.2.1 Definitionn實際被測要素(線要素)對理想直線的允許變動. A straightness tolerance is the amount which line elements are permitted to vary from a true line.291.2 Straightness1.2.2 Straightness of Features301.2 Straightness1.2.3 Straightness of Feature-of-size311.2 Straightness1.2.4 Straightness of Feature-of-size(MMC)321.3 Circularity在同一正截面上.半徑差為圓度公差值的同心 圓之間的區域.A circularity tolerance zone is two concentric circles spaced apart a radial distance equal to the circularity tolerance value.1.3.1 Definitionn實際被測要素對理想圓的允許變動. A circularity tolerance is the a
