ng bb 27 process capability

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  • 1. UNCLASSIFIED / FOUO UNCLASSIFIED / FOUONational Guard Black Belt Training Module 27 Process Capability UNCLASSIFIED / FOUO UNCLASSIFIED / FOUO

2. UNCLASSIFIED / FOUOCPI Roadmap Measure 8-STEP PROCESS 6. See 1.Validate2. Identify3. Set 4. Determine 5. Develop7. Confirm 8. StandardizeCounter-the PerformanceImprovement RootCounter-Results SuccessfulMeasuresProblem Gaps Targets CauseMeasures& Process ProcessesThroughDefine MeasureAnalyzeImprove Control 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 2 3. UNCLASSIFIED / FOUO Learning Objectives Learn prerequisites for conducting process capability studies Learn how Cp and Cpk are calculated and how to interpret the Minitab output Learn how to handle continuous and attribute data UNCLASSIFIED / FOUO 3 4. UNCLASSIFIED / FOUO Process Capability What Is It? Mostmeasures have some target value and acceptable limits of variation around the target usually set by the customer The extent to which the expected values fall within these customer specification limits determines how capable the process is of meeting its requirements Consider key measures of process performance in: Help Desk Responsiveness Job Acceptance Rate Customer Queue Time Service Treatment (complaints) Service Cost / Order On-Time DeliveryProcess Capability UNCLASSIFIED / FOUO 4 5. UNCLASSIFIED / FOUO Process Capability Cp Ratioof total variation allowed by the specification to the total variation actually measured from the process Use Cp when the mean can easily be adjusted (i.e., transactional processes where resources can easily be added with no or minor impact on quality) AND the mean is monitored (so process owner will know when adjustment is necessary doing control charting is one way of monitoring) Typicalgoals for Cp are greater than 1.33 (or 1.67 for safety items) If Cp < 1, then the variability of the process is greater than the specification limitsProcess CapabilityUNCLASSIFIED / FOUO 5 6. UNCLASSIFIED / FOUO Process Capability Cp Allowed variation (spec.)(USL - LSL) Cp orCp Normal variation of the process699.7% of values-3 +3 Process WidthLSLT USLProcess Capability UNCLASSIFIED / FOUO 6 7. UNCLASSIFIED / FOUO A Metaphor for Cp Parking Vehicles 1 Cp measures the width of the vehicle in the street and compares it to the width of the parking place without parking the vehicle. Cp < 1 Cp 1Cp >> 1Process Capability UNCLASSIFIED / FOUO 7 8. UNCLASSIFIED / FOUO Process Capability Cpk This index accounts for the dynamic mean shift in the process the amount that the process is off target USL xx LSL C pk Min or 3 3 Calculate both values and report the smaller number Process Capability UNCLASSIFIED / FOUO 8 9. UNCLASSIFIED / FOUOProcess Capability Cpk, CPU, CPL Mostcommon calculation of Process Capability Ratio of the range between the sample mean and the nearest specification to 3 standard deviations. Usewhen the mean cannot be easily adjusted (i.e., Cycle times, customer satisfaction indices, etc.) Typicalgoals for Cpk are greater than 1.33 (or 1.67 if safety related) For Cpk Std. Deviation estimates use: Rbar/d2[short term] (calculated from Xbar-R chart) Process CapabilityUNCLASSIFIED / FOUO 9 10. UNCLASSIFIED / FOUO A Metaphor for Cp Parking Vehicles 1 +/- 3 (Voice of Process)Cp 1.3 +/- 3 (Voice of Process)Voice of Customer+/- 3 (Voice of Process)For Cp, it doesnt matter where the process is relative to the specifications,only the width of the process to the width of the specifications. Process CapabilityUNCLASSIFIED / FOUO 10 11. UNCLASSIFIED / FOUO A Metaphor for Cpk Parking Vehicles 2Cpk 1.3 +/- 3 (Voice of Process)Cpk 1.3 : the process has room to move before exceeding a customer specification. In other words, at least the driver and/or the passenger can get out of the HMMWV .Process CapabilityUNCLASSIFIED / FOUO 11 12. UNCLASSIFIED / FOUO A Metaphor for Cpk Parking Vehicles 2+/- 3 (Voice of Process)Cpk 0 Specifications (Voice of Customer) Cpk 0: The center of the process is on (or equal to) a customer specification (either side)! Process CapabilityUNCLASSIFIED / FOUO 12 13. UNCLASSIFIED / FOUO A Metaphor for Cpk Parking Vehicles 2 Specifications (Voice of Customer)Cpk -1 +/- 3 (Voice of Process) Cpk -1: The center of the process is outside the customer specifications (either side)! Process CapabilityUNCLASSIFIED / FOUO 13 14. UNCLASSIFIED / FOUO Uses of Capability Analysis Performed on existing processes as a means of establishing a baseline of current operations (so its possible to tell when improvement has occurred) When done periodically, is a means of monitoring change (good or bad) of a process for whatever reason (system, personnel, environment, etc.) Can be done on any process that has a target spec. established (target spec. is needed for the values in numerator), and has a capable measuring system (needed for valid values in denominator)Process Capability UNCLASSIFIED / FOUO 14 15. UNCLASSIFIED / FOUO Process Capability CPU CPU indicates capability against an Upper Specification Limit. In the next example, the average delivery time of a Pizza Company is within the 30 minute requirement. However, the histogram shows that quite a few deliveries are exceeding the 30 minute upper spec. limit The CPU figure of 0.139 confirms that the process is incapable (Quality Tools>Capability Sixpack>NormalNote: This exercise is based ona different dataset than previousslides so different, unrelatedresults can be expected.Process Capability UNCLASSIFIED / FOUO 17 18. UNCLASSIFIED / FOUOMinitab Exercise (Cont.)1. Double click on C-5 Delivery Time to Place it in the box for Single column2. In the Subgroup size Box, type a 1 since our Sample size is one3. For Upper Spec type in 30 minutes (given)4. Click on OK Note: For Process Capability you must have at least 1 Spec LimitProcess Capability UNCLASSIFIED / FOUO 18 19. UNCLASSIFIED / FOUO Minitab Exercise (Cont.)Process Capability Sixpack of Delivery TimeI ChartCapability Histogram 40USL UCL=37.71 On both the I ChartS L 30 S pecificationsIndividual ValueU 30 _ X=29.12 and the Moving Range Chart, the points are 201 2855 82 109 136 163 190 217 244 LCL=20.53 randomly distributed 24 26 28 30 3234 36 Moving Range Chart between the control Normal Prob Plot 10UCL=10.55 limits, D: 1.947, P : < 0.005Aimplying a stable process .Moving Range 5 __ MR=3.23 0 LCL=01 2855 82 109 136 163 190 217 244 2025 3035 Last 25 Observations 35 The points Capability Plot O v erall Within on Within Last 25the Observations chart make aS tDev 2.86364 S tDev 2.68251Values 30 random scatter, with pno *CpC pk*0.1 O v erall P P pk 0.11 25trends or shifts, which alsoS pecs C pm *245 250255 Observation260265 indicates process stability.Process CapabilityUNCLASSIFIED / FOUO 19 20. UNCLASSIFIED / FOUO Minitab Exercise (Cont.) Process Capability Sixpack of Delivery Time I ChartCapability Histogram The data in the Capability Histogram 40 USL UCL=37.71 approximately follow the normal curve. On the S pecificationsIndividual ValueU S L 30 normal 30probability plot, the points extend _X=29.12 outside the 95% confidence interval and have a p-value < 0.05, which indicates that our LCL=20.53 20 data is non-normal82. 109 136 163 190 217 2441 28 55242628 30 3234 36Moving Range ChartNormal Prob Plot Since the data is non-normal, we have UCL=10.55 A D: 1.947, P : < 0.00510 consulted our MBB who conducted a moreMoving Range thorough analysis that indicated we are still 5 __ OK using a normal probability analysis. MR=3.23 0LCL=012855 82 109 136 163 190 217 244 2025 3035Last 25 ObservationsCapability Plot 35Within Within O v erallS tDev 2.86364S tDev 2.68251Values Cpk is 0.1 30 Cp* Pp *O v erallC pk0.1 P pk 0.11 25 Is our process capable? S pecsC pm * 245 250255260265Observation Process CapabilityUNCLASSIFIED / FOUO 20 21. UNCLASSIFIED / FOUO Process Capability CPL CPL indicates capability against a Lower Specification Limit Army Lodging has been getting complaints about its slow elevators and decided to collect data to investigate. In this example, the speed of an elevator computer is unacceptable below 150 cm/sec. The CPL of 1.48 indicates the process is capable of meeting the specifications if it continues within the same range of variationProcess Capability UNCLASSIFIED / FOUO 21 22. UNCLASSIFIED / FOUO Process Capability CPL (Cont.) Cpl= X - LSL3s _Process Capability UNCLASSIFIED / FOUO 22 23. UNCLASSIFIED / FOUO Process Capability Cpk Cpkis the index used when a process has a two-sidedspecification ArmyLodging is concerned that the temperatures of itsguest rooms may vary too widely. In this example, thetemperature of a guest room needs to be between 62 and70 degrees Fahrenheit for the guest to be comfortable.We determine Cpk by calculating both CPU and CPL Cpk is the smaller of the two! You can see that while almost no rooms are too cold, somerooms are too hot which is reflected in the Cpk of 0.36(which is much less than 1) Process Capability UNCLASSIFIED / FOUO 23 24. UNCLASSIFIED / FOUO Process Capability Cpk (Cont.) Cpk = Cpl or Cpu (whichever is smaller)_ _ ,Process CapabilityUNCLASSIFIED / FOUO 24 25. UNCLASSIFIED / FOUO Process Capability Cpk __ USL x x LSLCpk Minor 3s 3s Calculate both values and