ng bb 24 measurement system analysis - continuous

Download NG BB 24 Measurement System Analysis - Continuous

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  • 1. UNCLASSIFIED / FOUO UNCLASSIFIED / FOUONational Guard Black Belt TrainingModule 24 Measurement System Analysis (MSA)Continuous Data UNCLASSIFIED / FOUO UNCLASSIFIED / FOUO

2. UNCLASSIFIED / FOUOCPI Roadmap Measure 8-STEP PROCESS 6. See 1.Validate2. Identify 3. Set4. Determine5. Develop 7. Confirm8. StandardizeCounter-the Performance ImprovementRoot Counter- ResultsSuccessfulMeasuresProblem GapsTargetsCause Measures & ProcessProcessesThroughDefineMeasure Analyze ImproveControl TOOLSProcess MappingACTIVITIES Map Current Process / Go & SeeProcess Cycle Efficiency/TOC Identify Key Input, Process, Output Metrics Littles Law Develop Operational Definitions Operational Definitions Develop Data Collection PlanData Collection Plan Validate Measurement System Statistical Sampling Collect Baseline Data Measurement System Analysis Identify Performance Gaps TPM Estimate Financial/Operational Benefits Generic Pull Determine Process Stability/CapabilitySetup Reduction Complete Measure Tollgate Control ChartsHistogramsConstraint IdentificationProcess Capability Note: Activities and tools vary by project. Lists provided here are not necessarily all-inclusive.UNCLASSIFIED / FOUO 3. UNCLASSIFIED / FOUO Learning Objective Understand how to conduct and interpret a measurement system analysis using Continuous Data Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 3 4. UNCLASSIFIED / FOUO Acceptable Measurement SystemsProperties that all acceptable measurement systems musthave: The measurement system must be in control (onlycommon cause variation) Variability of the measurement system must be small in relation to the process variation Variability of the measurement system must be small compared with the specification limits (the tolerance) The increments of the measurement must be small relative to the smaller of: the process variability or the specification limits Rule of thumb: increments are to be no greater than 1/10th of the smaller ofprocess variability or specification limits Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 4 5. UNCLASSIFIED / FOUO Measurement System Study- Prep Plan the approach: Select number of appraisers, number of samples and number of repeat measures Use at least 2 appraisers and 5 samples, where eachappraiser measures each sample at least twice (all usingsame device) Select appraisers who normally do the measurement Select samples from the process that represent its entireoperating range. Label each sample discretely so the label isnot visible to the operator. Check that the instrument has a discrimination that is equal to or less than 1/10 of the expected process variability or specification limitsMeasurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 5 6. UNCLASSIFIED / FOUO Measurement Study Prep (cont.) Assure that the gage/instrument has been maintained and calibrated to traceable standards Parts are selected specifically to represent the full process variationParts should come from both outside the specs (high side and low side) and from within the specification rangeMeasurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 6 7. UNCLASSIFIED / FOUO Running the Measurement Study In order to run the MSA: Each sample should be measured 2-3 times by each operator Make sure the parts are marked for ease of data collection but remain blind(unidentifiable) to the operators Be there for the study and record any unplanned influences. Randomize the parts continuously during the study to preclude operators influencing the test The first time evaluating a given measurement process, let the process run as it would normally run Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 7 8. UNCLASSIFIED / FOUO Running the Study GuidelinesBecause in many cases we are unsure of how noise canaffect our measurement system, we recommend thefollowing procedure: Have the first operator measure all the samples once inrandom order Have the second operator measure all the samples once inrandom order Continue until all operators have measured the samplesonce (this is Trial 1) Repeat the previous two steps each time for the requirednumber of trials Use a form to collect information Analyze results Determine follow-up action, if anyMeasurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 8 9. UNCLASSIFIED / FOUO Exercise: Run MSA in Minitab Can we trust our measurement system? The maintenance function at an ANG airlift wing is evaluating avendors non-destructive testing (NDT) method that claims to bebetter, faster and less expensive Faster NDT reduces overall cycle time for inspections of airframe,hence an Upper Specification Limit Faster is better, but too fast an NDT cycle time might mean aninadequate time for the penetration of the dyes into hairlinefractures, hence the Lower Specification Limit USL minus LSL = Tolerance SL minus Mean Response = One Sided Tolerance This MSA evaluates the ability of the measurement system todetect changes in overall NDT inspection cycle timeMeasurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 9 10. UNCLASSIFIED / FOUO MSA Example in Minitab Ten parts were selected that represent the expected range ofthe part type variation. Three inspectors measured the tenparts, three times per part, in a random order.This data set is Gage3.mtw.Column Name DescriptionC1 Part Part NumberC2OperatorTest Operator numberC3ResponseCycle Time for inspection Above is the description of the data from Minitab Is it short form? Long form?Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 10 11. UNCLASSIFIED / FOUOData Set = Gage3.mtwStat>Quality Tools>Gage Study>Gage R&R Study (Crossed) Note: Gage R&R Study (Crossed) is the most commonly used method for Variables (Continuous Data). It is used when the same parts can be tested multiple times, i.e. NON DESTRUCTIVE TESTS. GR&R (Nested) MSA is for DESTRUCTIVE TESTING.. Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 11 12. UNCLASSIFIED / FOUOGage R&R in MinitabEnter the variables (circled fields) in the above dialogue box and keepthe ANOVA method of analysis checked. The main difference betweenANOVA and Xbar and R is that ANOVA will estimate an operator bypart interaction. The ANOVA method is the preferred method. Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 12 13. UNCLASSIFIED / FOUOGage R&R in Minitab (Cont.)Gage R&R Study (Crossed)dialog boxAfter enteringthe variablesin this dialog box,click on Optionsto view theoptions dialog boxOptions dialog box Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 13 14. UNCLASSIFIED / FOUOGage R&R in Minitab Options Options dialog box.6.0 is the default for the number of sd inthe Study variation. This is the Z valuerange that calculates a 99.73% potentialStudy Variation based on the calculatedStandard Deviation of the variation seenin the parts chosen for the study.Alternatively, you may see texts use 5.15sd, that corresponds to 99%.The Spec Limits for the process are 10.75as the USL and 8.75 as the LSL. You caneither enter these in the appropriateboxes (be sure to click on Enter at leastone specification limit), OR you canenter the Process tolerance (Upperspec Lower spec = 10.75 8.75 = 2.0)by clicking and entering 2.0 in Upperspec Lower spec. (Either way givesthe same results.)The Process Sigma has been 0.195. Enter .195 in the DialogBox for Historical standard deviation.Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 14 15. UNCLASSIFIED / FOUO Interpreting Acceptability IfProcess Tolerance and Historical Sigma values are not used in Minitab, a critical assumption is then made that the sample parts chosen for the study, truthfully exhibit the true process variation. In this case, the acceptability of the measurement system is based upon comparison only to the part variation seen in the study. This can be a valid assumption if care is taken in selecting the study sample parts. Oneelement of criteria whether a measurement system is acceptable to analyze a process is the percentage of the part tolerance or the operational process variation that is consumed by measurement system variation.Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 15 16. UNCLASSIFIED / FOUOMinitab Gage R&R - Six-PackGage R&R (ANOVA) for Response Lets look at these six Reported by :G age name:D ate of study :charts one at a time Tolerance: M isc:Components of VariationResponse by Part100 % Contribution% Study Var10.00Percent% Process% Tolerance9.75 50 9.500 Gage R&RRepeat Reprod Part-to-Part 1 23 456 7 89 10PartR Chart by Operator 1 2 3 Response by OperatorUCL=0.10730.10 10.00Sample Range_9.750.05R=0.0417 9.500.00LCL=01 2 3 OperatorXbar Chart by Operator 1 2 3Operator * Part Interaction 10.0010.00 O perator Sample Mean1__ AverageUCL=9.84222X=9.7996 9.759.75LCL=9.75693 9.509.501 2 34 567 8 9 10 Part Measurement System Analysis (MSA) - ContinuousUNCLASSIFIED / FOUO 16 17. UNCLASSIFIED / FOUO Gage R&R - RelationshipsAmeasurement process is said to be consistent when the results foroperators are Repeatable and the results between operators areReproducibleAgage is valid to detect part-to-part variation when the variability ofoperator measurements is small relative to process variability or thetolerance range The percent of process variation consumed by the measurement (%R&R) is then determined once the measurement process is consistentand can detect part-to-part variation Measurement System Analysis (MSA) - Continuous UNCLASSIFIED / FOUO 17 18. UNCLASSIFIED / FOUO Six Pack #1 Components of Variation Focuson the 3 Bars to the right in each cluster. These represent the % of total variance contributed from the data. Gage R&R is the total variation in our measurement system broken into repeatability and reproducibility. T


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