Questions and Answers How Relevant Questions Obtain Useful Answers Judson B. Estes Fiat Chrysler Automobiles March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 1 Focus on the 4 C’s Weave the wisdom from many available tool sets into a package of training, certification and project work 1. Collect Currently available facts relevant to problem. Listen for what is already known and suspected. Communicate to entire team the current facts to get on the same page. 2. Contrast A Measurable difference in performance. How do you measure the performance? How Big is the difference? 3. Converge Use Logical Strategies to isolate the candidate cause. What split are you making? How does that narrow the possible causes? 4. Confirm Test the candidate cause to prove it is the true root cause. What is your Statistical Confidence? When can we implement the fix? March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 2 Collect Phase • Describe Problem • Identify Possible Causes • Evaluate Possible Measurements March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 3 Collect Phase Describe the Problem • State the Problem naming the deviation for which you want to find the cause • To help stay on track, ask: – What object (or group of objects) has the deviation? – What deviation does it have? – What do we see, feel, hear, taste, or smell that tells us there is a deviation? – Write a short statement in Object/Deviation format • Use one object and one deviation • Be specific, separate if needed March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 4 Collect Phase Specify the Problem • Describe the deviation factually to increase understanding of the deviation • Ask questions in 4 areas: – WHAT—Identity – WHERE—Location – WHEN—Timing – EXTENT—Size March 2014 IS IS NOT Describe the problem in detail. Tighten IS data. Help eliminate possible causes. Confidential and Proprietary to Fiat Chrysler Automobiles 5 Collect Phase Example PROBLEM SOLVING [1] PROBLEM AREA Problem Statement: Description facts LX low beam bulb infant failure PROBLEM ARPEA NON-PROBLEM AREA (IS observed / reported) (IS NOT observed/reported) WHAT: 1. Object low beam bulb # L0009006 used in LX 300 models LXCH48, LXCP48, LXFP48 . Click here to see VIN list Magnums and 300C's. Also WK, PT use same Pt # low beam bulb, All other bulbs in the Click here to see ID of vehicle, subassemblies, bulb and field warranty performance. 2. Defect LOP 085032 Needs replacement Some examined from Field, Hot shock is the main conclusion from the Sylvania lab report Other potential lab conclusions could have been but were not "cold shock", "high voltage" & "wear out" March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 6 “I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;” -Lord Kelvin March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 7 Contrast Phase Frequency Required 1 0 Current 4 Length (mm) Frequency Required Current -3 -1.5 0 1.5 3 Flushness (mm) March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 8 Contrast Phase Open seams on DR seats resulting in high warranty costs Cloth seats Problem Definition Statement Front seat Driver side Seat back Rear seat Seam A Frequency 71% of returns are driver side seats 92% of returns and narratives are seat cushions Examination of returned product shows seam B accounts for 42 out of 54 claims Seam B BOB/WOW seam WOW cushion March 2014 83% of returns are front seats Passenger side Seat cushion Required 0 90% of returns are leather Leather seats 1 Other strategies See Strategy Diagram Current Width (mm) Find and eliminate the Red X causing open seams on the DR front driver side leather seats 4 Confidential and Proprietary to Fiat Chrysler Automobiles 9 Contrast Phase • What is a BOB and a WOW? – Best of the Best and Worst of the Worst – Not necessarily a good and bad part but really parts that are as different as possible in the way they effect the Customer. – We are looking for contrast in order to see differences March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 10 Contrast Phase example Measure twice and get the same answer on BOB and WOW March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 11 Converge Phase • Once we make sure our measurement system isn’t fooling us then we start generating clues • We then use certain tools to begin to converge on the Red X candidate – Concentration diagram – Component search Stage 1 and 2 – Operation Search – Paired and Group comparisons – Event to Energy transform March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 12 Reactive Problem Solving Hierarchy Use the Right Tool for the Problem TRIZ and Systemology Innovation and Evolution Pure Statistics No Strategy and All Tools Six Sigma Classical and Taguchi Design of Experiments Simple Strategy and Most Tools Multiple Variables and Interactions Shainin Red X Strategies Multiple Strategies, Easy Statistics IS/ IS Not Problem Specifications Distinctions and Changes Ishikawa Fishbone Diagram 5 Whys to the Root Cause March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles Organized Brainstorming Simple Questioning 13 Problem Solving Hierarchy Least Widely Used Hardest to Grasp TRIZ and Systemology More Variables and Interactions Pure Statistics Six Sigma Increased Variation and Environment Changes Classical and Taguchi Design of Experiments Shainin Critical Thinking Ishikawa Fishbone Diagrams Most Widely Used March 2014 5 Whys to the Root Cause Confidential and Proprietary to Fiat Chrysler Automobiles Easiest to Grasp 14 Concentration Diagram example 1 A B C D E F 2 3 4 5 6 7 8 xx xx x x xx xxx xx xxx xxx xxxx x Paint Craters on “B” pillar March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 15 Component Search Stage 2 . • Plotting Stage 2 30 Stage 1 20 * 10 Green Y = lbs. WOW + * + * * + + + * * + 0 BOB Orig. March 2014 1st D/R 2nd D/R 3rd D/R S1 Confidential and Proprietary to Fiat Chrysler Automobiles orig 16 Confirmation Phase • Once we identify the Red X candidate it is now time to use statistics to confirm our candidate. • Some tools types that are used for this: – Six Pack B vs. C – Tukey test – Barrier B vs. C – Spike B vs. C – 5 Penny test – Factorial Experiment (DOE) – Binomial probability March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 17 Six Pack B vs. C • B • C B is the “Better” part or process or sub-assembly or material March 2014 C is the “Current” part or process or sub-assembly or material Confidential and Proprietary to Fiat Chrysler Automobiles 18 Six Pack B vs. C Example 1 The required confidence level is 95%, which therefore requires a sample size of 3 B’s and 3 C’s and an end count of 6. Rank Order B 8.3 B 8.8 B 9.1 C 9.8 C 10.6 C 11.2 March 2014 Run Order B or C 1 C Diameter (mm) 10.6 2 B 8.3 3 C 11.2 4 C 9.8 5 B 9.1 6 B 8.8 The end count equals 6. Therefore, it can be stated with 95% confidence that the B’s are better than the C’s. Confidential and Proprietary to Fiat Chrysler Automobiles 19 Six Pack B vs. C Test Example • Distribution of two groups looks something like this. B 8.0 March 2014 B 8.5 B 9.0 C 9.5 C 10 10.5 Confidential and Proprietary to Fiat Chrysler Automobiles C 11 11.5 20 Reliability by Design March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles Reliability Prediction of Performance Verification of Performance Improvement of Prediction The best Prediction methods are quantative. The best Verification is actual parts and systems in real usage. The best Improvement eliminates all discrepancy between prediction and reality. March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 22 Deterministic Design • Design parameters are deterministic, i.e., they have unique values • CTQ’s are also deterministic, and are calculated as functions of the design variables by transfer functions, Y = f (X1, X2, …, XN) X1 X2 . Design Parameters (X’s) Transfer Function Y = f (X1, X2, … XN) XN CTQ’s (Y’s) Y1 . . . YN Most engineering design is deterministic March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 23 Statistical Design • Design parameters are statistical in nature, with mean values and variation (e.g., standard deviation) • CTQ variations determined by statistical analysis (e.g., Monte Carlo), using the transfer function and statistical variations in design parameters X1 X2 . Design Parameters (X’s) Transfer Function Y = f (X1, X2, … XN) XN Noise Parameters CTQ’s (Y’s) Y1 . . . YN XN1 . . XNn DFSS uses statistical design to understand and control variation March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 24 Statistical Design Why Prototyping Doesn’t Reveal Problems Prototyping: Single Product Copy LSL USL X1 X2 Xn Selected prototype inputs Y=f(X1,X2...) Reality: Multiple Product Copies X2 Y Input variability not captured, defects masked LSL X1 Xn Range of possible inputs USL Y=f(X1,X2...) Y Defects Realistic distribution of product Y (CTQ) • Prototyping does not verify product robustness • It assesses functionality of a single, often hand-selected, sample March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 25 Statistical Design Mechanical Example: Simply Supported Box Beam Baseline Design Performance Requirements: • Applied load: 200 kg/m over 1.5 m • Overhang = LT-L1 = 4.5 m t h • Design margin must be positive, i.e., yield strength > max stress • 6 quality • Low cost WP w P F L1 LT Analysis: Transfer function Margin = Yield strength - Max stress = Yield strength - (Max stress from tensile load + Max stress from bending) Margin March 2014 = F Sy - ____________ 2ht + 2wt - 4t2 - 3hPWp (2LT - 2L1 - Wp) ____________________ wh3 - (w - 2t) (h - 2t)3 Confidential and Proprietary to Fiat Chrysler Automobiles 26 Statistical Design Deterministic Design of Beam F Analysis: Margin = Sy - ____________ 2ht + 2wt - 4t2 Choose values for design parameters and applied loads: Substituting: 3hPWp (2LT - 2L1 - Wp) ____________________ wh3 - (w - 2t) (h - 2t)3 Design Parameter/Load Value Beam length, LT (m) 12 7.5 Support length, L1 (m) Beam height, h (m) 0.75 Beam width, w (m) 0.25 Section thickness, t (m) 0.05 2 89,600 Yield strength, Sy (kg/m ) Uniform load density, P (kg/m) 200 1.5 Uniform load width, Wp (m) Tensile load, F (kg) 100 Margin = + 9,726 kg/m2 Baseline design meets positive design margin requirement, but quality level unknown March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 27 Statistical Design Simply Supported Box Beam F Analysis: Margin = Sy - ____________ 2ht + 2wt - 4t2 - 3hPWp (2LT - 2L1 - Wp) ____________________ wh3 - (w - 2t) (h - 2t)3 Design parameters & applied loads are statistical in nature • Choose mean values and a variability measure (e.g., std deviation) • Consider tolerances Design Parameter/Load Mean Beam length, LT (m) 12 Support length, L1 (m) 7.5 Beam height, h (m) 0.75 Beam width, w (m) 0.25 Section thickness, t (m) 0.05 2 Yield strength, Sy (kg/m ) 89,600 Uniform load density, P (kg/m) 200 Uniform load width, Wp (m) 1.5 Tensile load, F (kg) 100 March 2014 Std Dev Tolerances Lower Upper 0.017 0.013 0.0033 0.0033 0.0025 3,200 3.3 0.07 1.65 0.05 0.04 0.01 0.01 0 7,500 5 0.2 5 Confidential and Proprietary to Fiat Chrysler Automobiles 0.05 0.04 0.01 0.01 0.01 0 5 0.2 5 28 Statistical Design Simply Supported Box Beam F Analysis: Margin = Sy - ____________ 2ht + 2wt - 4t2 3hPWp (2LT - 2L1 - Wp) ____________________ wh3 - (w - 2t) (h - 2t)3 Do a statistical analysis (e.g., Monte Carlo), using transfer function and statistical parameter & load values Results: • Margin mean 9,726 kg/m2 5,466 kg/m2 Probability .040 Mean = 9,726 .030 .020 • Margin std dev • Defect probability 3.8% .010 • Design 3.3 .000 Defects -5,000 0 10,000 20,000 30,000 Design Margin (kg/m2) Design margin may be positive or negative! March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 29 Statistical Design Reaching “6” Design optimization analysis: • Use transfer function to understand the shape of the response surface and the design margin’s sensitivity to each design parameter • Reduce defects by shifting mean values or reducing variances of the most sensitive design parameters • Sensitivities found by partial differentiation of transfer function and evaluation at design point Design Parameter/Load Mean Std Dev Beam length, LT (m) 12 Support length, L1 (m) 7.5 Beam height, h (m) 0.75 Beam width, w (m) 0.25 Section thickness, t (m) 0.05 2 Yield strength, Sy (kg/m ) 89600 Uniform load density, P (kg/m) 200 Uniform load width, Wp (m) 1.5 Tensile load, F (kg) 100 0.017 0.013 0.0033 0.0033 0.0025 3200 3.3 0.07 1.65 March 2014 Sensitivity - 21,003 21,003 180,205 181,676 1,158,739 1 - 393.8 - 42,007 - 11.1 Confidential and Proprietary to Fiat Chrysler Automobiles Margin most sensitive to t, with w and h next 30 Statistical Design Reaching “6” Improving the design margin: • In general, design can be improved by shifting means of the most sensitive parameters or reducing their variabilities • Although t is the most sensitive parameter, we elect to shift the mean of w (next most sensitive) because box beams come in only a few standard thicknesses (the next thicker beam would be too costly and heavy) .040 Beam width, w 0.25 0.30 0.35 • Mean 9,726 17,879 24,518 • Std deviation 5,466 5,124 4,853 • Defect prob, % 3.8 0.024 0.00002 • Design 3.3 5.0 6.5 Probability Design margin results: .030 .020 w = 0.25 Defects w = 0.30 .010 w = 0.35 .000 -5,000 March 2014 0 Confidential and Proprietary to Fiat Chrysler Automobiles 10,000 20,000 30,000 Design Margin (kg/m2) 31 Problem Solving or Problem Prevention • Discussion and Questions ?? March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 32 Statistical Design Electronics Example: Switching Power Supply Vin = 85 - 275 Vac Input Filter Performance Requirements • Output voltage, Vo: 5 V, +/-5% • Input voltage, Vin: 85 - 275 V • 6 quality • Low cost Vo = 5 Vdc, +/-5% Isolated Switching Converter Feedback V Baseline Design o Isolated switching converter/ feedback section • Baseline design combines power MOSFET & control circuit in a 3-pin package • March 2014 OPTO • R2 • PWM IC CTRL R1 Vref I b Confidential and Proprietary to Fiat Chrysler Automobiles R1 33 Statistical Design Deterministic Design of Power Supply Analysis: Transfer function Choose values for design parameters: Substituting: Vo = Vref + R2 ( Vref ____ + Ib R1 ) Design Parameter Value LM 431I ref voltage, Vref (volts) R1 (ohms) R2 (ohms) Bias current, Ib (amps) 2.495 10,000 10,000 5.0E-06 Output voltage = 5.04 volts Baseline design meets 5V, +/- 5% performance requirement, but quality level unknown March 2014 Confidential and Proprietary to Fiat Chrysler Automobiles 34 Statistical Design Switching Power Supply Transfer function (unchanged) • Design parameters are statistical in nature. Choose mean values and a variability measure (e.g., std deviation): • Do a statistical analysis (e.g., Monte Carlo), using the transfer function and the statistical parameter values Results: • Vo mean 5.04 volts 0.059 volts • Vo std dev • Defects/million 188 (5.06) March 2014 ( Vo = Vref + R2 Design Parameter Vref ____ + Ib R1 Mean Std Dev ) Tolerances Lower Upper LM 431I Vref (volts) 2.495 0.0283 0.085 0.085 R1 (ohms) 10,000 33.33 1% 1% 10,000 33.33 1% 1% R2 (ohms) Bias current, Ib (amps) 5.0E-06 1.15E-06 2.00E-06 2.00E-06 .035 Probability Analysis: .026 .017 .009 .000 4.75 4.875 5.00 Volts 5.125 Baseline design meets 5V, +/- 5% performance requirement, but quality level is not 6 Confidential and Proprietary to Fiat Chrysler Automobiles 5.25 35 Statistical Design Reaching “6” Design optimization analysis: • Use transfer function to understand the shape of the response surface and the output voltage’s sensitivity to each design parameter • Reduce defect rate by shifting mean values or reducing variances of design parameters Design Parameter LM 431I Vref (volts) R1 (ohms) R2 (ohms) Bias current, Ib (amps) Mean 2.495 10,000 10,000 5.0E-06 March 2014 Centered .038 Probability • Vo std dev • Defects/million 5.00 volts 0.058 volts 20 (5.61) Sensitivity 2 -0.0002495 0.0002545 10,000 Base Design Mod 1: Center distribution by increasing R1 to 10,160 ohms Results: • Vo mean Std Dev 0.0283 33.33 33.33 1.15E-06 .028 .019 .009 .000 4.75 Confidential and Proprietary to Fiat Chrysler Automobiles 4.875 5.00 Volts 5.125 5.25 36 Statistical Design Reaching “6” (cont’d) Design Mod 2: Mod 1 plus 0.1% resistors to reduce resistor variance Centered Design Mod 3: Mod 2 plus LM 431AI MOSFET to reduce Vref variance Base 0.1% Resistors MOSFET Upgrade 0.1% Resistors .050 Probability Probability .038 .028 .019 .009 .000 4.75 Summary March 2014 4.875 5.00 Volts 5.125 5.25 Mean .037 .025 .012 .000 4.75 Std Dev DPMO 4.875 5.00 Volts Z ST Cost Baseline Design Mod 1: Centered via R 1 5.04 5.00 0.059 0.058 189 20 5.06 5.61 100% 100% Mod 2: 0.1% Resistors Mod 3: LM 431AI 5.00 5.00 0.057 0.041 13 ~0 5.7 7.58 101% 105% Statistical design enables performance, quality & cost prediction during the design process Confidential and Proprietary to Fiat Chrysler Automobiles 5.125 5.25 37

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