1、1,Geometric Dimensioning and Tolerancing (GD&T),Lecturer: B Fang,形位公差理念,2,目 錄,簡(jiǎn)介 Introduction 專門(mén)術(shù)語(yǔ) Terminology 分類 & 原則 Classification and Rules 定義與應(yīng)用 Definition and Application,3,簡(jiǎn) 介,Introduction,4,Introduction(1),Many of Industrys problems stem from faulty communications. In todays competitive mark

2、et, it is not enough to make drawings that can be understand. We must make drawings that cannot possibly be MISUNDERSTAND.Using the GD&T is an efficient way.,許多行業(yè)上的糾紛起源于溝通的缺乏. 在當(dāng)今日益激烈的竟?fàn)幹?為讓客戶對(duì)藍(lán)圖不發(fā)生誤解, 運(yùn)用國(guó)際標(biāo)準(zhǔn)的形位公差標(biāo)注是最有效的途徑之一.,5,GD&T is a dual purpose system. First it is set of standard symbols which

3、 are used to define part features and their tolerance zones. Second it is a philosophy of defining a part based on how it functions.,Introduction(2),What is GD&T?,GD另一方面,它也體現(xiàn)了被測(cè)要素的功能要求.,6,What is GD&T?,The Geometric Tolerance is the amount which true elements are permitted to vary from an ideal elem

4、ent.,指被測(cè)實(shí)際要素對(duì)其理想要素的變動(dòng)量.,7,Introduction(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) Surface Tolerance (Roughness) (3). 形狀和位置公差 Geometric Tolerance,8,Introduction(4),In 1966, the first united standard was published by the American National Standards Institute (

5、ANSI), known as ANSI Y14.5. It was updated in 1973,1982,1994.,形位公差標(biāo)準(zhǔn)的演變歷程: 最先應(yīng)用于軍事工業(yè), 以美國(guó)與英國(guó)應(yīng)用最為廣泛,各種不同的組織相繼出版了各種不同的標(biāo)準(zhǔn).1966年,第一部統(tǒng)一的標(biāo)準(zhǔn)- ANSI Y14.5出版,並經(jīng)歷1973,1982和1994三次改版.,9,Introduction(5),優(yōu)點(diǎn): Advantages: 有利于增強(qiáng)彼此之間的交流 Improves communications 有利于產(chǎn)品的設(shè)計(jì) Better product designs 有利于零件制造公差的盈餘 Production to

6、lerances increased,10,專門(mén)術(shù)語(yǔ),Terminology,11,1.尺寸要素 & 非尺寸要素 Feature-of-size and Feature,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 of spherical surface or a set of parallel surfaces, each of which is associated with a size dimension. 平面. 直線等沒(méi)有大小的要素稱為非尺寸要素 A feature is a general term appli

7、ed to a physical portion of a part, such as a surface, hole, or slot.,12,A,B,C,D,E,非尺寸要素Feature: D,E 尺寸要素Feature-of-size: A,B,C,Explain:,13,2.理想邊界狀態(tài) Virtual Condition,由設(shè)計(jì)給定的具有理想形狀的極限包容面, 稱為理想邊界狀態(tài). Virtual condition is the theoretical extreme boundary of a feature-of-size generated by the collective

8、effects of MMC and any applicable geometric tolerances.,14,3.盈餘公差 Bonus Tolerance,盈餘公差是指實(shí)際尺寸偏離最大實(shí)體尺寸的大小. A bonus tolerance equal to the amount that the feature-of-size departs from MMC.,15,Geometric characteristic symbol,ModifierDenotes shape of Tolerance zone,ModifierDenotes Material condition,Datu

9、m references,Tolerance value,4.形位公差框格 Feature Control Frame,16,5.附加符號(hào) Modifying symbols,Term Abbreviation Symbol Maximum Material Condition MMC M Least Material Condition LMC L Regardless of Feature size RFS S,17,6.理論正確尺寸 Basic Dimensions,A basic dimension is a numerical value used to describe theor

10、etically exact characteristics of a feature or datum target.,理論正確尺寸:在設(shè)計(jì)過(guò)程中用來(lái)確定要素的精確位置,在檢測(cè)過(guò)程中作為計(jì)算形位誤差的依據(jù).,26.0,18,分類 & 原則,Classification and Rules,19,五大類 共13小項(xiàng) (對(duì)稱度除外) (Except for Symmetry),分 類 Classification,20,基本原則(1-1)Fundamental Rules,Rule #1 (Envelope rule) For features-of-size, where only a siz

11、e dimension is specified, the surfaces shall not extend beyond a boundary (envelope) of PERFECT FORM AT MMC.,Rule #1 (包容原則) 尺寸公差與形位公差相互有關(guān)的一種要求. 采用包容要求的尺寸要素其實(shí)際輪廓應(yīng)遵守最大實(shí)體邊界,即其體外作用尺寸不超出最大實(shí)體尺寸,且其局部實(shí)際尺寸不超出最小實(shí)體尺寸.,21,Applied to an external feature-of-size,Applied to an internal feature-of-size,基本原則(1-2)Fun

12、damental Rules,22,基本原則(2)Fundamental Rules,Rule #2 (獨(dú)立原則),獨(dú)立原則就是圖樣上給定的各個(gè)尺寸和形狀.位置要求都是獨(dú)立的,應(yīng)該公別滿足各自的要求.,獨(dú)立原則是尺寸公差和形位公差相互關(guān)系遵循的基本原則.,23,Rule #3 (位置度公差應(yīng)用原則) 對(duì)于位置度公差,基準(zhǔn)要素為尺寸要素時(shí),基準(zhǔn)符號(hào)后必須接有 S , L , M 等符號(hào). Rule #2 (Tolerance of position rule) For tolerance of position, S , L , or M must be specified in the fea

13、ture control frame with respect to the tolerance 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,24,Rule #4 (除位置度以外幾何公差之應(yīng)用原則) 對(duì)于位置度以外的幾何公差,沒(méi)有特殊標(biāo)識(shí)的以RFS(不相關(guān)原則)處理. Rule #3 (Other than tolerance of position rule) For o

14、ther than a tolerance of position, RFS applies with 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,25,定義 與 應(yīng)用,

15、Definition and Application,26,1.Form Controls,Form controls never use a datum reference.,27,1.1 Flatness,1.1.1 Definition 實(shí)際被測(cè)要素對(duì)理想平面的允許變動(dòng). 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(qū)域. A flatness tolerance zone is the dist

16、ant between two parallel plane spaced apart a distance equal to the flatness tolerance value.,28,0.1wide flatness tolerance zone,The surface must lie between two parallel planes 0.1 apart,Limits set by Rule #1,1.1.2 Application,1.1 Flatness,29,1.2 Straightness,根據(jù)不同的設(shè)計(jì)要求,直線度公差可以有幾種不同形狀的公差帶. A straigh

17、tness control has a different tolerance zone depending upon its application to a feature or to a feature-of-size.,1.2.1 Definition,實(shí)際被測(cè)要素(線要素)對(duì)理想直線的允許變動(dòng). A straightness tolerance is the amount which line elements are permitted to vary from a true line.,30,1.2 Straightness,1.2.2 Straightness of Featu

18、res,31,1.2 Straightness,1.2.3 Straightness of Feature-of-size,32,1.2 Straightness,1.2.4 Straightness of Feature-of-size(MMC),33,1.3 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(qū)域. A circularity tolerance zone is two concentric circles spaced apart a radial distance equal to the circularity tolerance value.,

19、1.3.1 Definition,實(shí)際被測(cè)要素對(duì)理想圓的允許變動(dòng). A circularity tolerance is the amount which surface elements of the diameter may vary from a theoretical circle.,34,1.3 Circularity,1.3.2 Application,35,1.4 Cylindricity,半徑差為圓柱度公差值的兩同軸圓柱面之間的區(qū)域. A cylindricity tolerance zone is two concentric cylinders spaced apart a

20、 radial distance equal to the cylindricity tolerance value.,1.4.1 Definition,實(shí)際被測(cè)要素對(duì)理想圓柱的允許變動(dòng). A cylindricity tolerance is the amount which surface elements of a cylinder may be allowed to vary from a theoretically perfect cylinder.,36,1.4.2 Application,1.4 Cylindricity,37,2.Orientation Controls,38,

21、2.1 Perpendicularity,A perpendicularity tolerance is the amount which a surface, or axis, or centerplane is permitted to vary from being perpendicular to the datum.,39,2.1 Perpendicularity,2.1.1 Applied to a surface or a planar feature-of-size,40,2.1 Perpendicularity,2.1.2 Applied to a diameter (in

22、one direction only),41,2.1 Perpendicularity,2.1.3 Applied to the axis of a diameter,42,2.1 Perpendicularity,2.1.4 Applied to a surface line element,43,2.2 Angularity,An angularity tolerance is the amount which a surface, centerplane, or axis is permitted to vary from its specified exact angle.,An an

23、gularity control has a different tolerance zone depending upon its application.,44,2.2 Angularity,2.2.1 Applied to a surface or a planar feature-of-size,45,2.2 Angularity,2.2.2 Applied to an axis,46,2.3 Parallelism,A parallelism tolerance is the amount which a surface, centerplane, or axis is permit

24、ted to vary from the parallel state.,A parallelism tolerance zone is two parallel planes or a cylinder depending upon its application.,47,2.3 Parallelism,2.3.1 Parallel planes as a tolerance zone,48,2.3 Parallelism,2.3.2 A cylinder as a tolerance zone,49,3. Location Controls,Location controls should

25、 always be applied to feature-of-size.,50,3.1 Positional tolerance,3.1.1 Definition,The total permissible variation in the location of a feature-of-size about its true position.,51,3.1 Positional tolerance,3.1.2 Requirements,The tolerance of position must be applied to a feature-of-size. Datum refer

26、ences are required. Basic dimensions are used to establish the true location of the feature-of-size from the specified datums and between interrelated feature-of-size. LMC,MMC,or RFS modifiers must be specified in the feature control symbol as prescribed by Rule #2.,52,t =2 (X1-X2)2+(Y1-Y2)2,3.1 Pos

27、itional tolerance,3.1.3 Calculation,53,3.1 Positional tolerance,3.1.4 Application (1),Size Tol Zone 14.0(MMC) .40 14.2 .60 14.5 .90 14.8(LMC) .12,Size Tol Zone 4.00(MMC) .25 4.10 .35 4.20 .45 4.25(LMC) .50,54,3.1 Positional tolerance,3.1.4 Application (2),Size Tol Zone .500(MMC) .010 .501 .011 .502(

28、LMC) .012,Size Tol Zone .500(MMC) .003 .501 .004 .502(LMC) .005,Size Tol Zone .380(MMC) .005 .381 .006 .382 .007 .383(LMC) .008,55,3.1 Positional tolerance,3.1.4 Application (3),Size Tol Zone 30.2(LMC) 0.4 30.3 0.5 30.4(MMC) 0.6,56,3.1 Positional tolerance,3.1.4 Application (4),57,3.1 Positional tol

29、erance,當(dāng)D孔處于MMC :,Size Tol Zone .380(MMC) .005 .381 .006 .382 .007 .383(LMC) .008,當(dāng)D孔處于LMC :,Size Tol Zone .383(LMC) .010,3.1.4 Application (5),58,3.2 Concentricity,3.2.1 Definition,Concentricity tolerance The total amount of allowable variation of a feature-of-size axis to a datum axis.,A Concentri

30、city tolerance zone is a cylindrical, whose axis is coincident with the datum axis, within which the axis of the considered feature-of-size must lie.,59,3.2 Concentricity,3.2.2 Application,60,3.3 Symmetry,A symmetry tolerance is the amount which a center element is permitted to vary.,61,3.3 Symmetry,Old method, can be replaced by position tolerance.,62,4.Runout,Runout is a composite control affecting both form and location relative to a datum axis.,63,4.1 Circular Runout,4.1.1 Definition,Circular Runout is a composite control affecting both the form and location of circular element