Hi!Introduction to Geometric Dimensioning and Tolerancing Objective: To impart the basic knowledge of „Geometric Dimensioning and Tolerancing (GDT)‟. Develop an awareness of GDT concepts and explain how the techniques are used to understand, control, and help reduce variation in the overall (---) process. Agenda: 1. Think About • • • • • • • • Product Requirements Dimensional Management What is GDT? Why is GDT required? How it is different from conventional drawings, Which Standards are used? Definitions Virtual Condition 2. Geometric Dimensioning & Tolerancing (GDT) Agenda (Continued) : 2. Geometric Dimensioning & Tolerancing (GDT) (Continued) • Bonus Tolerance • Datum Symbology • Datum Referencing • Six Degrees of Freedom • Datum Shift 3. From GD&T to practical gauges Squeak.Product Design : Product Requirement Aesthetic ( Fit and Finish) Safety Durability & Operability Requirements (Functional) NVH and Buzz. Rattle (Product experience) Cost. (and Cost and Cost >>>) Manufacturing Process Capability Timeline Constraint . Product Design : Engineering Changes proposed -24 -18 -12 -6 0 Launch 6 Timeline . . Safety etc. As tolerances are functional and achieved using Stack Up – it eliminates unnecessary tighter tolerances.) Stack Up analysis to optimize tolerances.Product Design : How to achieve the Requirements? Locating and Attachment as per Functional Requirement (Fit and Finish. Assembly. FnF Inspection etc will continue. Part Capability. .Product Design : Dimensional Management Process Technical Design Review Concept Locating Strategy Tolerance Analysis FnF Requirement (Loop) Technical Design Review & GDT Signoff Engineering Release Gage Concept & Design Tooling Concept & Design Gage R&R. Tolerance Analysis Worst case analysis Root Sum Square (RSS) 3. Qualification (Gaging) .Dimensional Management: Dimensional Management 1. Geometric Dimensioning & Tolerancing Datum (Locating & Attachment Strategy) Tolerances 2. Geometric Dimensioning & Tolerancing : Geometric Dimensioning & Tolerancing . symbols and mathematical structure of GDT is used for describing the manufacturing tolerance zones to express the “Design (Functional) Intent” of parts or assemblies.Geometric Dimensioning & Tolerancing : What is Geometric Dimensioning & Tolerancing? GDT is the language from Design to Manufacturing and Inspection defining how to qualify the part.“say exactly what they mean”. The concepts. It is an international graphic engineering language formed to allow engineers . The goal of GDT is to Improve Communication !! . Geometric Dimensioning & Tolerancing : Important Engineering language Graphic language Mathematical structure “to say exactly what we mean” about the “Design (Functional) Intent” The goal of GDT is to Improve Communication !! . Geometric Dimensioning & Tolerancing : Why Geometric Dimensioning & Tolerancing? The reason for the importance of this subject is – ? . 4 0.6 0.0 Tolerance .7 0.Geometric Dimensioning & Tolerancing : .2 0.5 0.3 0.9 1.8 0.because it saves Money.1 0. Money 0. Functional philosophy for Tolerancing – studies product function in the design stage for “Functional Tolerancing”. Same language for Designer. 2. assumptions and the controversies. Functional approach provides larger tolerance in “Other zones”. Manufacturer & Inspector. ambiguity.Geometric Dimensioning & Tolerancing : 1. Improves Communication Reduces subjective interpretation. Tool to express “what they mean exactly”. Better Product Design 3. “Bonus” or extra Manufacturing Tolerance – savings in cost. Increased Production Tolerances . Functional Performance Properly applied GD&T assures assembly.” . (Parts produced at different locations & assembled somewhere else – “outsourcing”) GDT provides a method of maintaining coordination between functional design features. Coordinated Datum Locations / Functional Tolerancing “Maximizing production tolerances without sacrificing Quality and Reliability. manufacturing processes & inspection practices (coordinated datum locations). 5. and functional performance of all mating details. interchangeability.Geometric Dimensioning & Tolerancing : 4. 5M . ANSI.1994 . ISO We will refer the ASME Y14.Geometric Dimensioning & Tolerancing → Standards : GDT Standards ASME. JIS. GDT → Definitions : Definitions . . geometric characteristic. location. Tolerance The total amount a specific dimension is permitted to vary. The tolerance is the difference between the maximum and minimum limits. or surface texture of a part or part feature.GDT → Definitions : Dimension A numeric value expressed in appropriate units of measure and used to define the size. or location of a feature or datum target. profile. It is the basis from which permissible variations are established (by tolerances). usually without tolerance. . orientation. used for information purposes only. Reference Dimension A dimension.GDT → Definitions : Basic Dimension A numerical value used to describe the theoretically exact size. Equal Bilateral Tolerance A tolerance in which equal variation is permitted in both directions from the specified dimension.25 .0 25 +/. 50 +0.25/.0.GDT → Definitions : Unilateral Tolerance A tolerance in which variation is permitted in one direction from the specified dimension. such as a surface. or slot. . Feature Physical portion of a part.GDT → Definitions : Datum A theoretically exact point. axis. pin. hole. Datum Feature An actual feature of a part that is used to establish a datum. tab.from which the Geometric Characteristics of a part are established. or plane derived from the true geometric counterpart of a datum feature . . or set of two opposed elements or opposed parallel surfaces associated with a size dimension. or plane established by inspection equipment. Feature of Size. or a mandrel (Datum Feature Simulator). One cylindrical or spherical surface. such as the following simulators: a surface plate. axis.GDT → Definitions : Simulated Datum A point. a gage surface. GDT → Definitions : Part (Workpiece) V Block is used to simulate Datum which is Axis of the part Simulated Datum Datum Feature Simulator ( V Block) (Surface on Gage or Fixture Locator) . minimum hole diameter or maximum shaft diameter.GDT → Definitions : Maximum Material Condition The condition in which a feature of size contains the maximum amount of material within the stated limits of size -.for example. M WHEN THE PART WEIGHS THE MOST! . GDT → Definitions : . L WHEN THE PART WEIGHS THE LEAST! .GDT → Definitions : Least Material Condition The condition in which a feature of size contains the least amount of material within the stated limits of size -.for example. maximum hole diameter or minimum shaft diameter. GDT → Definitions : GDT → Definitions : Regardless of Feature Size S * The term used to indicate that a geometric tolerance or datum reference applies at any increment of size of the feature within its size tolerance. * No longer required to indicate “regardless of feature size” (See rule #2 ASME Y14.5M-1994). GDT → Definitions : Regardless of Feature Size Actual Locating Hole A RFS Pin Spring GDT → Definitions : Actual Mating Envelope (a) For an External Feature - A similar perfect feature counterpart of smallest size that can be circumscribed about the feature so that it just contacts the surface at the highest points. .A similar perfect feature counterpart of largest size that can be inscribed within the feature so that it just contacts the surface at the highest points.GDT → Definitions : Actual Mating Envelope (b) For an Internal Feature . GDT → Definitions : True Geometric Counterpart The theoretically perfect boundary (virtual condition or actual mating envelope) or best-fit (tangent) plane of a specified datum feature.feature A (Smallest circumscribed cylinder) Work piece Datum axis A (Axis of true geometric counterpart) Datum feature A . A Datum feature simulator True geometric counterpart of datum . GDT → Definitions : Tolerance Zone The zone which the tolerance value represents. . GDT → Definitions : Tolerance Zone . .GDT → Virtual Condition : Virtual Condition A constant boundary generated by the collective effects of a size feature‟s specified MMC or LMC material condition and the geometric tolerance for that material condition. Virtual Condition is the „Worst Case‟ envelope of boundary that occurs due to the combination of tolerances. GDT → Virtual Condition : Ø 6 +/.1 Virtual Condition Tolerance Zone Ø 1 What will be the Dia. of it ? Guess ?! . GDT → Virtual Condition : . GDT → Virtual Condition : . GDT → Virtual Condition : . GDT → Virtual Condition : . 5 Virtual Condition = MMC .GDT → Virtual Condition : Shaft O Positional tolerance referred @ MMC No Positional tolerance @ MMC O 12. features of size require: PERFECT FORM AT (MMC) .GDT → Rules : Rules Rule #1 Individual Feature of Size Where only a tolerance of size is specified. the limits of size of an individual feature prescribe the extent to which variations in its geometric form as well as size are allowed. In other words. GDT → Bonus Tolerance : Bonus Tolerance – (Consider effect of MMC) Ø 6 +/.1 MMC = 6 + 1 = 7 (For Shaft) = MMC + Position Tolerance VC =7+1=8 Part Size Virtual Condition Position Tolerance Bonus Tolerance Effective MMC 7 6 8 1 1 0 1 1 2 LMC 5 1 2 3 . Zone . Zone Axis Matching Virtual Condition Ø 8 Tolerance Zone Ø 1 Outside Tol.GDT → Bonus Tolerance : Bonus Tolerance – (Consider effect of MMC) Ø 6 +/.1 Axis in Tol. 5 Datum Feature Symbol M ABM Material Modifier (Datum) C .GDT → Symbology : Feature Control Frame Material Modifier (Tolerance) Datum Reference Frame 1M A B C Geometric Characteristic Symbol Tolerance Secondary Datum Diameter Symbol 0. C .0 when produced at Maximum Material Condition with respect to Datum A.GDT → Symbology : How to „Read‟ it? 1M A B C The Feature is at a Circular Position tolerance zone of Ø 1. B. GDT → Datum : Datum Referencing . GDT → Datum : Six Degrees of Freedom Z Axis Rotational Y Axis Linear X Axis Linear X Axis Rotational Y Axis Rotational Z Axis Linear . GDT → Datum : Six Degrees of Freedom TERTIARY DATUM PLANE SECONDARY DATUM PLANE 90º o 90º 90º PRIMARY DATUM PLANE . GDT → Datum : Six Degrees of Freedom 3-2-1 THIRD DATUM PLANE PART PAR T 3 Fixed FIRST DATUM PLANE PART PART PART PART SECOND DATUM PLANE 1 Fixed Fixed 2 . The part is oriented and immobilized relative to the three mutually perpendicular planes i. .e.GDT → Datum : Datum Reference Frame Sufficient datum features are chosen to position the part in relation to a set of „Three mutually Perpendicular ‟ planes. jointly called a datum reference frame. the datum reference frame in a selected order of precedence. 2. Functional Datum (Recommended) The actual features which locate and attach a part / assembly to its next part / assembly (on functional basis).GDT → Datum : 1. . Non-Functional Datum Features used to locate a part or assembly to a Gage based on convenience not function. GDT → Datum : Plane Surface Datum Features . GDT → Datum : Plane Surface Datum Features . GDT → Datum : Cylindrical Datum Features . GDT → Datum : Cylindrical Datum Features . GDT → Datum : Inclined Datum Features a . 1 0M A BM C .GDT → Datum : Inclined Datum Features 9.8 ± 0.8 ± 0.1 0M A B 15. Datum Precedence : Effect of Datum Precedence and MMC * See Below . Datum Precedence : Datum Precedence @ A then B Datum feature B True geometric counterpart of Datum feature B (Perpendicular to datum Axis A) Datum feature B (Secondary) Datum axis A True geometric counterpart of datum feature A Without Perpendicularity tolerance . Datum Precedence : Datum Precedence @ B then A Datum feature A (Secondary) Datum feature B (True geometric counterpart of Datum feature B) Datum feature B (Primary) Datum axis A True geometric counterpart of datum feature A (VC Counter part hole Considering diametrical Tolerance and perpendicularity) . Gage @ RFS : T A Taper pin locates the datum irrespective of the feature size . Gage @ MMC : A . Datum Shift : . Datum Shift : When Gaging a Part with a datum FOS referenced at MMC -Gage is of Fixed size (i. Virtual Condition) Gage Size (VC) 8 Ø 10 ± 1 Ø1 M A B 7±1 1M A BM C Gage Size (VC) 5 A .e. center plane can vary ± 1. center axis can vary ± 1.Datum Shift : 10 ± 1 @ Position 1 @ MMC Bonus @ LMC of 11 is 3 i.5 .e.5 Datum Plane 7 ± 1 @ Position 1 @ MMC Bonus @ LMC of 8 is 3 i.e. Datum Plane .Datum Shift : Datum B is produced at MMC (Ø9) and centered to Gage Pin (Ø8) . Slot is produced at MMC (6) and centered to Gage feature (5). Datum Shift : Datum B is produced at MMC (Ø9) and centered to Gage Pin (Ø8) . Slot is produced at LMC (8) and centered to Gage feature (5). Datum Plane . Bonus Tolerance).e. Slot is produced at LMC (8) and offset from Datum plane by 1.Datum Shift : Datum B is produced at MMC (Ø9) and centered to Gage Pin (Ø8) .5 (i.5 Datum Plane . 1. 1.5 Datum Plane . Bonus Tolerance).Datum Shift : Datum B is produced at LMC (Ø11) and centered to Gage Pin (Ø8) . Slot is produced at LMC (8) and offset from Datum plane by 1.5 (i.e. e. Slot is produced at LMC (8) and offset from Datum plane by 1. Datum B) by 3 .5 Datum Shift for Slot is the Bonus tolerance of Hole.Datum Shift : Datum B is produced at LMC (Ø11) and offset from Datum axis by 1.0 Datum Plane 1.5 in opposite direction.5 (i.e.5 3. The slot center is offset from hole center (i. Bonus Tolerance). 1. .g. assembly.GDT → Datum → Sub Datum: Datum and Sub Datum Sub Datum is important for Data Correlation (for functions e. Fit and Finish) Tolerance Analysis for the Assembly. GDT → Datum → Sub Datum: Glove Box Datum . GDT → Datum → Sub Datum: Sub Datum for Glove Box on IP Substrate . Thank you! Thank you! . GDT → Symbology : Datum Feature Symbol A AB Datum Target Symbols 25 25 A1 12 A1 10 X 20 A1 A1 . GDT → Symbology : E G F K J H Ø Ø Ø . GDT → Symbology : As Shown on Drawing A1 120 A1 25 Means This: PART POINT CONTACT Datum Target Point . GDT → Symbology : As Shown on Drawing A1 Means This: 120 LINE CONTACT PART A1 LOCATING PIN Datum Target Line . GDT → Symbology : As Shown on Drawing 12 A1 Means This: 15 PARTIAL SURFACE CONTACT 15 PART DATUM BLOCK . GDT → Symbology : . 5 A B M C M Ø Diameter Symbol 0M A BM C 0M A B All-around Symbol Datum Feature Symbol Basic Dimension .GDT → Symbology : Other Modifiers Datum Target ↔ Between Symbol 0.