G D & T - Overview. Natarajan R. EGS Computers India Private Limited. Director. *

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1 G D & T - Overview Natarajan R Director * EGS Computers India Private Limited

2 Agenda Introduction to GD & T DimXpert for GD & T G D & T by examples Benefits of G D & T

3 What is GD & T? GD&T is a Universal Language for communicating engineering design specifications Includes all symbols, definitions, mathematical formulae and application rules necessary to convey specifications Conveys nominal dimensions and tolerances for a part Independent of Country and native language Approved by ASME, ANSI and DoD Language that designers use to translate design requirements into measurable specifications

4 What is GD&T? Way of communicating dimensional and tolerance requirements Allowable imperfection GD&T practices are governed by standards manuals ASME Y14.5M-2004 ASME Y

5 What is GD&T? ANSI Y14.5M-2004: Application of GD&T Y : Display of GD&T in 3D ASME ISO ISO 1101: Application of GD&T ISO 16792: Display of GD&T in 3D ISO

6 What is GD&T? Plus/Minus Tolerancing Geometric Tolerancing

7 Why use GD & T? It is important for the designer, manufacturer and inspector to understand part dimensions in the same manner GD & T principles result in time and cost savings Ensures adherence to quality criteria Reduces part rejection, mis-interpretation of drawings, reworking, inter-departmental crossfire and art-to-part transformation time Avoids assembly mis-match, failures and quality problems

8 Why use GD & T? Variation is inherent in nature Nothing real is perfect! CAD doesn t manufacture components Actual Manufacturing Processes do!

9 Why use GD & T? The Truth - Cost of Poor Quality (COPQ) Design Quality Progress Magazine Thousands of Hyundai's, Nissans and BMWs are targets of recalls --- Nissan announced the recall of about 116,000 Sentras because of a sensor problem. ASSOCIATED PRESS, Improving productivity by reducing wasteful costs is imperative in today s increasingly tough, competitive environment ultimately affecting a company s survival and its bottom line. Need for a holistic integrated systems solution to the COPQ problem.

10 Why use GD & T? GD & T and Tolerance Analysis target and solve these assembly build quality issues to reduce/eliminate COPQ

11 Upfront Information Saves Money GD & T and Tolerance Analysis during the part design phase permits optimization of the part from both functional and manufacturing perspectives before any tools are cut. COST BENEFIT End result: No surprises Higher Quality Parts Lower Cost Material Flexibility $ DFSS Enables! Cost of poor quality Design Production PRODUCT LIFE CYCLE

Design Methodolgoy with GD & T and Tolerance Analysis Evaluate different design concepts Locating schemes Assembly methods Evaluate manufacturing processes Re-assign Tolerances Loosen if possible,

12 Design Methodolgoy with GD & T and Tolerance Analysis Evaluate different design concepts Locating schemes Assembly methods Evaluate manufacturing processes Re-assign Tolerances Loosen if possible, Tighten if required * Cost Savings Opportunities Relative Cost 30 SPECIAL EQUIPMENT 25 HIGH ACCURACY BORING 20 GENERAL BORING 15 DRILLING mm Cost is Directly Related to Tolerances * SOURCE: British Std. BSI PD

13 How does GD&T Work? Four simple steps: Identify part surfaces to serve as origins and provide specific rules to establish starting point and direction for measurements Convey nominal (ideal) dimensions and orientations from origins to other surfaces Establish boundaries and / or tolerance zones for specific attributes of each surface along with specific rules for conformance Allow dynamic interaction between tolerances (simulating actual assembly possibilities) where appropriate to maximize tolerances

14 Features of Size - Four Fundamental Levels of Control Level 1: Controls size and circularity (for cylinders and spheres) at each cross section only Level 2: Adds overall form control Level 3: Adds Orientation control Level 4: Adds location control Each higher-level tolerance adds a degree of constraint demanded by feature s functional requirement All lower-level controls remain in effect Single feature can be subject to many tolerances simultaneously 14

15 Example 15

16 Resultant Interpretation 16

17 With GD&T 17

18 Explanation 18

19 Geometric Characteristic Symbols 19

20 Modifier Symbols 20

21 How can GD&T make a difference?

22 G D & T Simplified

23 Gear Box Cover Design

24 G D & T Reflecting Fit, Form & Functional Requirements

25 Gripper Assembly

26 Gripper Assembly

27 Gripper Assembly Exploded View

28 Gripper Holder Drawing

29 Gripper Holder Completeness of GD & T

tolerancing of 3D models Visual feedback on dimensional

30 How to develop GD & T schemes? DimXpert Example Intelligent, automated dimensioning and tolerancing of 3D models Visual feedback on dimensional completeness Automatically displays in 2D drawing Integrated with Tolerance Analysis

31 GD & T Scheme for Hydraulic Actuator Flange

32 GD & T Scheme for Hydraulic Actuator Flange

33 Complete 3D GD & T Annotation

34 Completeness of GD & T

35 GD & T Drawing

36 Dimensional Functionality: Schemes Geometric and Plus-minus dimension and tolerance schemes Geometric Plus-Minus

is colored based on its status: Green = Fully constrained Yellow = Under

37 Dimensional Functionality Show Tolerance Status Show Tolerance Status Informs user when the dimension and tolerance scheme is complete Each face is colored based on its status: Green = Fully constrained Yellow = Under constrained Red = Over constrained Native color = Not Recognized by DimXpert Before After

38 Benefits of G D & T Maximizes Tolerances thereby reducing per part cost Ensures unambiguous translation of designs into measurable specification Eliminates re-work and ensures assembly all the time Reduces product development cycle time

39 Thank You!

40 Tolerance Stack Up Analysis - Overview

41 Agenda Introduction to Tolerance Stacks Why Tolerance Stacks? Tolerance Analysis Step by Step Process Review by Example Benefits of Tolerance Stack Up Analysis

42 What is a Tolerance Stack? A method of mathematically predicting the resultant effect of piece part and subassembly tolerances along with assembly process and fixturing variation on a particular build objective of the assembly.

43 What is Tolerance Stack-up Analysis? Worst-case analysis Assumes dimensions vary within the entire range of their tolerance zones and that the accumulation of tolerances will experience all possible variations Performing worst-case analysis using a tolerance graph and hand calculation to determine the smallest permissible gap (G) Gmin = L1 + L2 + L3 + L4 + Ln = L1 + L2 + L3 + L4 = (-60.75) + (-42) + (-50.5) = -0.5 Interference

in real life It is incorrect to think max worst case is when the parts are at

44 What is Tolerance Stack-up Analysis? Worst-case tolerance analysis is dependent on how parts are actually assembled in real life It is incorrect to think max worst case is when the parts are at their largest and min worst case is when they are at their smallest Part Nominal Assembly Worst-case Maximum Worst-case Minimum

45 Dimensional Management Also referred to as dimensional control, dimensional variation management or dimensional engineering A process by which the design, fabrication, and inspection of a product are systematically defined and monitored to meet predetermined dimensional quality goals. An engineering process that is combined with a set of tools that make it possible to understand and design for variation. Aim is to improve first-time quality, performance, service life, and associated costs.

46 Dimensional Management A typical Dimensional Management system consists of the following tools Simultaneous or Concurrent Engineering Teams Written Goals and Objectives Design for Manufacturability and Assembly (DFMA) Geometric Dimensioning and Tolerancing (GD&T) Key Characteristics (KCC/KPC) Statistical Process Control (SPC) Variation Measurement and Reduction Variation Simulation Tolerance Analysis

47 Dimensional Management Historic Build-Test-Fix Method Iterative Loop COPQ Warranty Rework Retool ECO's Overtime Lost Time Etc... Analysis (FEA) Concept Model Design (CAD) Default and Carry over Tolerances Manufacturing Fire Fighting & Trouble Shooting B-T-F Process Customer

48 Dimensional Management New PD Process Functional Gauging & Fixturing Evaluate Geometric sensitivity Functional Datum Structure Logic Concept Model Define Performance Requirement Design (CAD) & Analysis (FEA) 3-D Variation Modeling Manufacturing Process Capability Key Characteristics SPC Evaluate and Optimize Assembly Process Satisfied Customer Smooth Launch Design Evaluation, Optimization & Validation Manufacturing Maintenance Quality Process Manual

49 Why Perform Tolerance Analysis? Analyze and optimize dimensional variability within an assembly system Establish piece part tolerances Reduce product costs by increasing tolerances Identify key tolerance contributors Reduce product cycle time and improve quality Determine if existing design and tooling will meet the build objective requirements (CTQs)

50 Tolerance Vs Variation Tolerance: Engineering specifications that are put in place to define or control the extreme limits of variation from nominal geometry. Defined based on product function Variation: The deviation of a geometric feature property from its nominal. A property of the manufacturing process

51 Tolerance Analysis Process Start Setting Build Objectives Determine method of Analysis Define Vector Loop and Contributor Characterisitics Calculate Variation of BO Calculate Mean Value of BO Optimize for Robustness End

52 Setting Build Objectives Early in the design process Customer Focus - perceptions of quality Benchmarking, Focus Group Meetings Representation from all internal groups Formal buy off - signatures

53 CTQ's Critical To Quality Characteristics Key measurable characteristics of a product or process whose performance standards or specification limits must be met in order to satisfy the customer They align improvement or design efforts with customer requirements.

54 Types of Build Objectives Fit Finish Function

55 Fit Objective Component Mating 100% Assemblability Hole/Pin interface Clearance/Interference Pin Diameter Hole Diameter

56 Finish Objective Aesthetics Gap Flush Speaker grille over flush to the door substrate Centering Consistency Door Substrate Consumer Products Speaker Grille

57 Functional Objective Assembly Function Range of Motion Locks Latches Alignments Guides Latch Latch Engagement

58 Build Objectives XYZ Inc. - Build Objectives, Product XXX Qualify Quantify Function Fit Finish Competition - Benchmarking - Competitive Assess. - QFD - VOC Quality Warranty Costs - Scrap - Down Time - Bottlenecks - Lost Customers

59 Tolerance Analysis Process Start Setting Build Objectives Determine method of Analysis Define Vector Loop and Contributor Characterisitics Calculate Variation of BO Calculate Mean Value of BO Optimize for Robustness End

60 Tolerance Loops (Vector Loops) A systematic method of approaching a tolerance stack, and selecting the contributing tolerances. A tolerance loop allows for the evaluation of not only the stack variation, but also the stack nominal value.

61 Tolerance Loops Establish start and finish points on each side of the objective. Travel from the start point to the finish point in the shortest route, this direction will be called ± 0.02 D1 4 ± D2 3 ± 0.01 D3 B.O. + Finish Point Starting Point

62 Tolerance Loops Go around the tolerance circuit in the opposite direction from previous step, taking the most direct route. Add signs to the nominal values according to their direction. 10 ± ± ± 0.01 B.O. B.O. = D1 D2 D3 D1 + D2 D3 Finish Point Starting Point

63 Tolerance Loops - Steps Start at one side of the objective surface Subtract each dimension that moves to left while adding each dimension that moves to right until the starting objective surface has been reached D1 (-) D2 (+) D3 (+) B.O. (+) Loop Start Surface

64 Example Assembly Equal Bilateral Tolerancing 10 ± ± ± 0.01 B.O. D1 + D2 D3 Finish Point Starting Point

65 Vector Loop Equation D1 + D 2 + D3 + B.O. = 0 B.O. = D1 D 2 D3

66 Tolerance Analysis Process Start Setting Build Objectives Determine method of Analysis Define Vector Loop and Contributor Characterisitics Calculate Variation of BO Calculate Mean Value of BO Optimize for Robustness End

67 Worst Case Analysis Worst case stacks simply sum all the tolerances in the assembly in a linear direction and predicts the maximum variation expected for a particular build objective.

68 Worst Case Analysis Formula Build Objective Variation = T1 + T2 + T3 + T Tn - Ti are the tolerance contributors affecting a particular build objective - Ti are assumed equal bilateral tolerances - n is the number tolerances in the stack

69 Worst Case Analysis Ignores tolerance distribution types Assumes all tolerances at their extreme limits Guarantees 100% assembleability Drives tight piece part tolerances / higher costs Restrict to critical mechanical interfaces

70 Worst Case Example Sum the Nominal Values Sum the Tolerances Nominal Dimensions + Tolerances D1: D2: D3: X = 3 ± or as a range = to

71 Worst Case Example - Mean µ B.O. = µ µ B.O. = = 3 D1 µ D2 µ D3

72 Worst Case Example - Variation 3± 0.045

Example Nominal Dimensions ± Tolerance + -0.820 0.

73 Example Nominal Dimensions ± Tolerance

74 One Dimensional Loop Calculation

75 Flange Gap Study in Sheet Metal

76 Tolerance Stacks Assembly Study

Mechanism Elevator Gear Train M O T O R WO R M G E A R T IP M O V E M E NT Specification: L SL = 0.0000, Nominal= 0.0000, USL = 0.1500 C ontrol L imits: L CL =-0.0023, Mean= 0.0506, UCL = 0.

8 7 8 3 0.9 1 3 4 %<LS L: 0.0 0 0 0 0.0 0 0 0 Cpk: 0.8 5 4 5 0.8 9 3 4 %>US L: 0.9 2 0 0 0.9 2 0 0 %OutS : 0.6 6 0 0 1.1 8 0 0 %OutS : 0.9 2 0 0 0.9 2 0 0 6600 11800 9200 9200 0.0041-0.

77 Mechanism Elevator Gear Train M O T O R WO R M G E A R T IP M O V E M E NT Specification: L SL = , Nominal= , USL = C ontrol L imits: L CL = , Mean= , UCL = % Out of spec.= , C p= , Cpk= , Mean Shift= Distr. Type: Gamma Min.: S td Dev: Max.: Cp: %<LS L: Cpk: %>US L: %OutS : %OutS : Mean: LCL: UCL: LSL LCL Nominal: LSL: USL: Simulation Number Mean Shift: Std Dev: Range: %<LSL: %>USL: %OutS: ppm OutS: Cp: Cpk: Mean σ USL USL UCL ppm OutS : Frequency Measurement %: 10.00%: GEAR 1 BA S E NOMINAL 3 σ LSL ppm OutS : Est. (99.7%) S ample Mean: Measurement Summary B ar Chart for WOR M GEAR TIP MOVEME NT MOTOR WOR M GEAR TIP MOV EMENT S ample S ize: % Conf. Int. in Est. Low. CI Upp. CI

78 Tolerance Stack-Up Analysis

79 Tolerance Stack-Up Analysis

80 Problem Definition Specifying Build Objective

81 Specifying the Vector Loop

82 Incorporating G D & T in Stack Up Calculations

83 Node Tree Definition for Vector Loop

84 Roll Up Calculations

85 Sensitivity Report for Tolerances affecting Assembly Build Objective

86 Predicting PPM

87 Summary of Features Maximum/minimum tolerance stack-up Identifies key contributors Graphically displays result Reduces prototyping and testing for assembly fit Leverages DimXpert Eliminates error-prone hand calculations Enables fast tolerance optimization

Summary of Benefits Eliminates ambiguity

88 Summary of Benefits Eliminates ambiguity in Drawing Generation Confirms to Standards Eliminates re-work Selective Tolerancing controls Cost Eliminates Rejection Reduces per-piece cost Helps understand and correct process deviations Increases profitability

89 Thank You

EGS Computers India Private Limited Chennai, Coimbatore, Trichy

White Paper on Geometric Dimensioning & Tolerancing with Tolerance Stack-Up Analysis EGS Computers India Private Limited Chennai, Coimbatore, Trichy Web: www.egsindia.com info@egs.co.in Tel: 044-2480 3370