Gdt tutorial

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  • Pat McQuistion
  • Quotes from Geo Metric III Foster
  • Quotes from Geo Metric III Foster
  • Quotes from Geo Metric III Foster Pat McQuistion
  • Pat McQuistion
  • Pat McQuistion
  • Pat McQuistion
  • Pat McQuistion
  • Why symbols ? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • Why symbols ? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • Why symbols ? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • Why symbols ? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • Why symbols ? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • Foster’s text
  • Foster’s text
  • Why symbols ? The symbol has uniform meaning. A note can be stated inconsistently, with a possibility of misunderstanding. Symbols are compact, quickly drawn, and can be placed on the drawing where the control applies Symbols can be made by computer or with a template & retain legibility when reproduced. Symbols provide international language. Notes may need to be translated if used in another country.
  • Gdt tutorial

    1. 1. Geometric Dimensioningand Tolerancing (GD&T) MANAGEMENT DESIGNVENDORS SALES PRICING TOOLING PURCHASING PLANNINGCUSTOMERS PRODUCTION SERVICE ROUTING INSPECTION ASSEMBLY PART PRODUCTION COMMUNICATION MODEL
    2. 2. Three Categories of DimensioningDimensioning can be divided intothree categories: •general dimensioning, •geometric dimensioning, and •surface texture.The following providesinformation necessary to begin tounderstand geometricdimensioning and tolerancing(GD&T)
    3. 3. Limit Tolerancing Applied To An Angle Block
    4. 4. Geometric TolerancingApplied To An Angle Block
    5. 5. Geometric Dimensioning & Tolerancing (GD&T)s GD&T is a means of dimensioning & tolerancing a drawing which considers the function of the part and how this part functions with related parts. – This allows a drawing to contain a more defined feature more accurately, without increasing tolerances.
    6. 6. GD&T cont’ds GD&T has increased in practice in last 15 years because of ISO 9000. – ISO 9000 requires not only that something be required, but how it is to be controlled. For example, how round does a round feature have to be?s GD&T is a system that uses standard symbols to indicate tolerances that are based on the feature’s geometry. – Sometimes called feature based dimensioning & tolerancing or true position dimensioning & tolerancings GD&T practices are specified in ANSI Y14.5M-1994.
    7. 7. For Examples Given Table Height Assume all 4 legs will be cut to length at the same time.s However, all surfaces have a degree of waviness, or smoothness. For example, the surface of a 2 x 4 is much wavier (rough) than the surface of a piece of glass. – As the table height is dimensioned, the following table would pass inspection. ors If top must be flatter, you could tighten the tolerance to ± 1/32. – However, now the height is restricted to 26.97 to 27.03 meaning good tables would be rejected.
    8. 8. Example cont’d.s You can have both, by using GD&T. – The table height may any height between 26 and 28 inches. – The table top must be flat within 1/16. (±1/32) .06 .06.06 28 27 26
    9. 9. WHY IS GD&T IMPORTANTs Saves money – For example, if large number of parts are being made – GD&T can reduce or eliminate inspection of some features. – Provides “bonus” tolerances Ensures design, dimension, and tolerance requirements as they relate to the actual functions Ensures interchangeability of mating parts at the assemblys Provides uniformitys It is a universal understanding of the symbols instead of words
    10. 10. WHEN TO USE GD&Ts When part features are critical to a function or interchangeabilitys When functional gaging is desirables When datum references are desirable to insure consistency between designs When standard interpretation or tolerance is not already implieds When it allows a better choice of machining processes to be made for production of a part
    11. 11. TERMINOLOGY REVIEWs Maximum Material Condition (MMC): The condition where a size feature contains the maximum amount of material within the stated limits of size. I.e., largest shaft and smallest hole.s Least Material Condition (LMC): The condition where a size feature contains the least amount of material within the stated limits of size. I.e., smallest shaft and largest hole.s Tolerance: Difference between MMC and LMC limits of a single dimension.s Allowance: Difference between the MMC of two mating parts. (Minimum clearance and maximum interference)s Basic Dimension: Nominal dimension from which tolerances are derived.
    12. 12. LIMITS OF SIZE SIZE DIMENSIONWHAT DOESTHIS MEAN? 2.007 2.003
    13. 13. LIMITS OF SIZEA variation in form is allowedbetween the least materialcondition (LMC) and themaximum material condition(MMC). SIZE DIMENSION ENVELOPE PRINCIPLE MMC (2.007) LMC (2.003) ENVELOPE OF SIZE Envelop Principle defines the size and form relationships between mating parts.
    14. 14. LIMITS OF SIZE ENVELOPE PRINCIPLE LMC CLEARANCEMMCALLOWANCE
    15. 15. LIMITS OF SIZEThe actual size of the feature atany cross section must bewithin the size boundary. ØMMC ØLMC
    16. 16. LIMITS OF SIZENo portion of the feature maybe outside a perfect formbarrier at maximum materialcondition (MMC).
    17. 17. Other FactorsI.e., Parallel Line Tolerance Zones GEOMETRIC DIMENSIONING TOLERANCE ZONES PARALLEL LINES PARALLEL LINES PARALLEL LINESPARALLEL PLANES PARALLEL PLANES PARALLEL PLANESPARALLEL PLANES PARALLEL PLANES CYLINDER ZONE
    18. 18. GEOMETRIC CHARACTERISTIC CONTROLS 14 characteristics that may be controlledTYPE OF TYPE OF CHARACTERISTIC SYMBOLFEATURE TOLERANCE FLATNESSINDIVIDUAL STRAIGHTNESS(No Datum FORMReference) CIRCULARITY CYLINDRICITYINDIVIDUAL LINE PROFILEor RELATED PROFILEFEATURES SURFACE PROFILE PERPENDICULARITY ORIENTATION ANGULARITY PARALLELISMRELATEDFEATURES CIRCULAR RUNOUT(Datum RUNOUTReference TOTAL RUNOUTRequired) CONCENTRICITY LOCATION POSITION SYMMETRY
    19. 19. Characteristics & Symbols cont’d.– Maximum Material Condition MMC– Regardless of Feature Size RFS– Least Material Condition LMC– Projected Tolerance Zone– Diametrical (Cylindrical) Tolerance Zone or Feature– Basic, or Exact, Dimension– Datum Feature Symbol– Feature Control Frame
    20. 20. Feature Control FRAME FEATURE CONTROL FrameGEOMETRIC SYMBOL TOLERANCE INFORMATION DATUM REFERENCES COMPARTMENT VARIABLESTHE RELATIVE TO OF THE FEATURE MUST BE WITHIN CONNECTING WORDS
    21. 21. Feature Control Frames Uses feature control frames to indicate tolerances Reads as: The position of the feature must be within a .003 diametrical tolerance zone at maximum material condition relative to datums A, B, and C.
    22. 22. Feature Control Frames Uses feature control frames to indicate tolerances Reads as: The position of the feature must be within a .003 diametrical tolerance zone at maximum material condition relative to datums A at maximum material condition and B.
    23. 23. Reading Feature Control Framess The of the feature must be within a tolerance zone.s The of the feature must be within a tolerance zone at relative to Datum .s The of the feature must be within a tolerance zone relative to Datum .s The of the feature must be within a zone at relative to Datum .s The of the feature must be within a tolerance zone relative to datums .
    24. 24. Placement of Feature Control Framess May be attached to a side, end or corner of the symbol box to an extension line.s Applied to surface.s Applied to axis
    25. 25. Placement of Feature Control Frames Cont’d.s May be below or closely adjacent to the dimension or note pertaining to that feature. Ø .500±.005
    26. 26. Basic Dimensions A theoretically exact size, profile, orientation, or location of a feature or datum target, therefore, a basic dimension is untoleranced.s Most often used with position, angularity, and profile)s Basic dimensions have a rectangle surrounding it. 1.000
    27. 27. Basic Dimension cont’d.
    28. 28. Form Featuress Individual Featuress No Datum Reference Flatness Straightness Circularity Cylindricity
    29. 29. Form Features ExamplesFlatness as stated ondrawing: The flatness of thefeature must be within .06tolerance zone.Straightness applied to a flat surface: Thestraightness of the feature must be within .003tolerance zone. .003 0.500 ±.005 .003 0.500 ±.005
    30. 30. Form Features ExamplesStraightness applied to the surface of adiameter: The straightness of the feature mustbe within .003 tolerance zone. .003 ∅ 0.500 0.505Straightness of an Axis at MMC: The derivedmedian line straightness of the feature must bewithin a diametric zone of .030 at MMC. ∅ 0.500 0.505 ∅ .030 M 1.010 0.990
    31. 31. Dial Indicator DIAL INDICATOR BEZEL CASE 2 2 4 46 6 8 8 10 10 12 CLAMP PROBE
    32. 32. Verification of Flatness
    33. 33. Activity 13s Work on worksheets GD&T 1, GD&T 2 #1 only, and GD&T 3 – (for GD&T 3 completely dimension. ¼” grid.)
    34. 34. Features that Require Datum Reference s Orientation – Perpendicularity – Angularity – Parallelism s Runout – Circular Runout – Total Runout s Location – Position – Concentricity – Symmetry
    35. 35. Datums Datums are features (points, axis, and planes) on the object that are used as reference surfaces from which other measurements are made. Used in designing, tooling, manufacturing, inspecting, and assembling components and sub- assemblies. – As you know, not every GD&T feature requires a datum, i.e., Flat 1.000
    36. 36. Datums cont’d.s Features are identified with respect to a datum.s Always start with the letter As Do not use letters I, O, or Qs May use double letters AA, BB, etc.s This information is located in the feature control frame.s Datums on a drawing of a part are represented using the symbol shown below.
    37. 37. Datum Reference Symbolss The datum feature symbol identifies a surface or feature of size as a datum. A A A ANSI ASME ISO 1982 1994
    38. 38. Placement of Datumss Datums are generally placed on a feature, a centerline, or a plane depending on how dimensions need to be referenced. A OR A A ANSI 1982 ASME 1994 Line up with arrow only when the feature is a feature of size and is being defined as the datum
    39. 39. Placement of Datumss Feature sizes, such as holes A Ø .500±.005s Sometimes a feature has a GD&T and is also a datum A Ø .500±.005 Ø .500±.005
    40. 40. TWELVE DEGREES OF FREEDOM UPLEFT BACK 6 LINEAR AND 6 ROTATIONAL DEGREES OF FREEDOMFRONT RIGHT DOWN UNRESTRICTED FREE MOVEMENT IN SPACE
    41. 41. Example Datumss Datums must be perpendicular to each other – Primary – Secondary – Tertiary Datum
    42. 42. Primary Datums A primary datum is selected to provide functional relationships, accessibility, and repeatability. – Functional Relationships » A standardization of size is desired in the manufacturing of a part. » Consideration of how parts are orientated to each other is very important. – For example, legos are made in a standard size in order to lock into place. A primary datum is chosen to reference the location of the mating features. – Accessibility » Does anything, such as, shafts, get in the way?
    43. 43. Primary Datum cont’d.– Repeatability For example, castings, sheet metal, etc. » The primary datum chosen must insure precise measurements. The surface established must produce consistent » Measurements when producing many identical parts to meet requirements specified.
    44. 44. Primary Datum Restricts 6 degrees of freedom FIRST DATUM ESTABLISHED BY THREE POINTS (MIN) CONTACT WITH SIMULATED DATUM A
    45. 45. Secondary & Tertiary Datumss All dimension may not be capable to reference from the primary datum to ensure functional relationships, accessibility, and repeatability. – Secondary Datum » Secondary datums are produced perpendicular to the primary datum so measurements can be referenced from them. – Tertiary Datum » This datum is always perpendicular to both the primary and secondary datums ensuring a fixed position from three related parts.
    46. 46. Secondary Datum  Restricts 10 degrees of freedom.SECOND DATUMPLANE ESTABLISHED BYTWO POINTS (MIN) CONTACTWITH SIMULATED DATUM B
    47. 47. Tertiary Datum Restricts 12 degrees of freedom. THIRD DATUM PLANE ESTABLISHED BY ONE POINT (MIN) 90° CONTACT WITH SIMULATED DATUM CMEASURING DIRECTIONS FORRELATED DIMENSIONS
    48. 48. Coordinate Measuring Machine COORDINATE MEASURING MACHINE BRIDGE DESIGN PROBE GRANITE Z SURFACE PLATE DATUM REFERENCE FRAME
    49. 49. Size Datum (CIRCULAR) THIS ON THE DRAWING A MEANS THIS SIMULATED DATUM- SMALLEST PART CIRCUMSCRIBED CYLINDERDATUM AXIS
    50. 50. Size Datum (CIRCULAR) THIS ON THE DRAWING A MEANS THIS SIMULATED DATUM- LARGEST PART INSCRIBEDDATUM AXIS A CYLINDER
    51. 51. Orientation Tolerances – Perpendicularity – Angularity – Parallelisms Controls the orientation ofindividual featuress Datums are requireds Shape of tolerance zone: 2parallel lines, 2 parallel planes, andcylindrical
    52. 52. PERPENDICULARITY:s is the condition of a surface, center plane, or axis at a right angle (90°) to a datum plane or axis. Ex: The perpendicularity of this surface must be within a .005 tolerance zone relative to datum A. The tolerance zone is the space between the 2 parallel lines. They are perpendicular to the datum plane and spaced .005 apart.
    53. 53. Practice Problems Plane 1 must be perpendicular within .005 tolerance zone to plane 2. BOTTOM SURFACE
    54. 54. Practice Problems Plane 1 must be perpendicular within .005 tolerance zone to plane 2 BOTTOM PLANE
    55. 55. Practice Problem 2.00±.01 .02 ToleranceWithout GD & T thiswould be acceptable 2.00±.01 .005 Tolerance Zone .02 Tolerance With GD & T the overall height may end anywhere between the two blue planes. But the bottom plane is restricted to the red tolerance zone.
    56. 56. PERPENDICULARITY Cont’d.s Location of hole (axis) This means ‘the hole (axis) must be perpendicular within a diametrical tolerance zone of .010 relative to datum A’
    57. 57. ANGULARITY:s is the condition of a surface, axis, or median plane which is at a specific angle (other than 90°) from a datum plane or axis. The surface is at a 45º angle with a . 005 tolerance zone relative to datum A.s Can be applied to an axis at MMC.s Typically must have a basic dimension.
    58. 58. PARALLELISM:s The condition of a surface or center plane equidistant at all points from a datum plane, or an axis.s The distance between the parallel lines, or surfaces, is specified by the geometric tolerance. ±0.01
    59. 59. Activity 13 Cont’d.s Complete worksheets GD&T-2, GD&T-4, and GD&T-5 – Completely dimension. – ¼” grid
    60. 60. Material Conditionss Maximum Material Condition (MMC)s Least Material Condition (LMC)s Regardless of Feature Size(RFS)
    61. 61. Maximum Material Conditions MMCs This is when part will weigh the most. – MMC for a shaft is the largest allowable size. » MMC of Ø0.240±.005? – MMC for a hole is the smallest allowable size. » MMC of Ø0.250±.005?s Permits greater possible tolerance as the part feature sizes vary from their calculated MMCs Ensures interchangeabilitys Used – With interrelated features with respect to location – Size, such as, hole, slot, pin, etc.
    62. 62. Least Material Conditions LMCs This is when part will weigh the least. – LMC for a shaft is the smallest allowable size. » LMC of Ø0.240±.005? – LMC for a hole is the largest allowable size. » LMC of Ø0.250±.005?
    63. 63. Regardless of Feature Sizes RFSs Requires that the condition of the material NOT be considered.s This is used when the size feature does not affect the specified tolerance.s Valid only when applied to features of size, such as holes, slots, pins, etc., with an axis or center plane.
    64. 64. Location Tolerances – Position – Concentricity – Symmetry
    65. 65. Position Tolerances A position tolerance is the total permissible variation in the location of a feature about its exact true position.s For cylindrical features, the position tolerance zone is typically a cylinder within which the axis of the feature must lie.s For other features, the center plane of the feature must fit in the space between two parallel planes.s The exact position of the feature is located with basic dimensions.s The position tolerance is typically associated with the size tolerance of the feature.s Datums are required.
    66. 66. Coordinate System Positions Consider the following hole dimensioned with coordinate dimensions:s The tolerance zone for the location of the hole is as follows: 2.000 .750s Several Problems: – Two points, equidistant from true position may not be accepted. – Total tolerance diagonally is .014, which may be more than was intended.
    67. 67. Coordinate System Positions Consider the following hole dimensioned with coordinate dimensions:s The tolerance zone for the location (axis) of the hole is as follows: Center can be anywhere along the diagonal line. 2.000 .750s Several Problems: – Two points, equidistant from true position may not be accepted. – Total tolerance diagonally is .014, which may be more than was intended. (1.4 Xs >, 1.4*.010=.014)
    68. 68. Position Tolerancings Consider the same hole, but add GD&T:s Now, overall tolerance zone is:MMC = .500 - .003 = .497s The actual center of the hole (axis) must lie in the round tolerance zone. The same tolerance is applied, regardless of the direction.
    69. 69. Bonus Tolerances Here is the beauty of the system! The specified tolerance was: This means that the tolerance is .010 if the hole size is the MMC size, or .497. If the hole is bigger, we get a bonus tolerance equal to the difference between the MMC size and the actual size.
    70. 70. Bonus Tolerance Example This means that the tolerance is . 010 if the hole size is the MMC size, or .497. If the .503 hole is bigger, we get a bonus tolerance equal to the difference between the MMC size and the actual size. Actual Hole Size Bonus Tol. Φ of Tol. Zone Ø .497 (MMC) 0 .010 Ø .499 (.499 - .497 = .002) .002 (.010 + .002 = .012) .012 Ø .500 (.500 - .497 = .003) .003 (.010 + .003 = .013) .013 Ø .502 .005 .015 Ø .503 (LMC) .006 .016 Ø .504 ? ?s This system makes sense… the larger the hole is, the more it can deviate from true position and still fit in the mating condition!
    71. 71. .497 = BONUS 0 Hole TOL ZONE .010 Shaft.499 - .497 = BONUS .002BONUS + TOL. ZONE = .012
    72. 72. .501 - .497 = BONUS .004 BONUS + TOL. ZONE = .014.503 - .497 = BONUS .006BONUS + TOL. ZONE = .016
    73. 73. s What if the tolerance had been specified as: Since there is NO material modifier, the tolerance is RFS, which stands for regardless of feature size. This means that the position tolerance is .010 at all times. There is no bonus tolerance associated with this specification.s VIRTUAL CONDITION: The worst case boundary generated by the collective effects of a size feature’s specified MMC or LMC material condition and the specified geometric tolerance. GT = GEOMETRIC TOLERANCE
    74. 74. PERPENDICULARITY Cont’d. Means “the hole (AXIS) must be perpendicular within a diametrical tolerance zone of .010 at MMC relative to datum A.” Actual Hole Bonus Ø of Tol. Size Tol. Zone 1.997 (MMC) 1.998 1.999 2.000 2.001Vc = 2.002 2.003
    75. 75. Activity 13 Cont’d.s Worksheet GD&T 6

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