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1、1-11a-p1Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSProcess Capability AnalysisOverview Brief1-11a-p2Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSCollect Timely DataProcess St
2、able/Consistent? (SPC)Process Acceptable? (Capability, Z)Develop measures with respect to standardsIdentify standards (specs) that address customer requirements (CTQs)YesNo*YesANALYZE PHASEUse “Special Cause Strategy” (How to improve an unstable system)Act quickly to search for the cause: What was D
3、IFFERENT? Which X just exerted its influence?“Message is in a SINGLE point”Use “Common Cause Strategy” (How to improve a stable system)Investigate relationships among inputs (Xs) and output (Y) via:Multi-Vari Study(Stratification)Experimentation (DOE)Disaggregation (Break into components)“Message is
4、 in ALL the points”MEASURE PHASEFocus, Define, Process Map, C&E, FMEA, etc.Evaluate Measurement System (MSA)IMPROVE PHASEPlan & Implement Short-Term Remedy (Immediate Containment) Plan & Implement Long-Term RemedyVerify Impact/Success (Before Vs After)Plan & Implement Long-Term RemedyVerify Impact/S
5、uccess (Before Vs After)CONTROL PHASEModify Control Plans: Hold GainsComplete Hand-Off ActivitiesEnsure New Procedures Are Used and Are EffectiveMonitor for Innovation & Improvement OpportunitiesMonitor Ever-Changing Customer Needs and RequirementsNo* =This data from an unstable, unpredictable proce
6、ss can still be used for a “Pseudo-Capability Study” - A rough “Before Vs After” guess at how much progress may be possible if we succeed in improving the “approximate Z(lt)” (using “Overall StdDev”) to Z(st).Developed by W. Scott Lasater - GEICSDEFINE1-11a-p3Week 1: Introduction to Process Capabili
7、tyGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSWhat sorts of data do you see being collected around your area?(List them below)_Attributes DataVariables Data1-11a-p4Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSHow To G
8、et Capability Indices Via Minitab(1) Variables Data(2) Attributes data.A Quick Look1-11a-p5Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSOpen file “Capab_v.mtw”. Characterize process capability. LSL= 40 and USL= 100What type of data is thi
9、s (Attribute or Variables)? VariablesZshort term= 4.67 Zlong term= 3.74Your capability study on “Percent Late Shipments” over the past four weeks has revealed at total of 400 “late” out of a total of 4000 shipments.Characterize process capability.What type of data is this (Attribute or Variables)? A
10、ttribute Zshort term= 2.782 Zlong term= 1.282Important Note: X-bar chart shows unstable process - may even be 2 different processes.1-11a-p6Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSMinitab Command: Six Sigma/Process Report/Single Colu
11、mn Output/Subgroup size subgroup(see next pages for details)Capability for Variables DataOpen file “Capab_v.mtw”. Characterize process capability. LSL= 40 and USL= 100What type of data? Variables DataZshort term= 4.67 Zlong term= 3.74Important Note: X-bar chart shows unstable process - may even be 2
12、 different processes.1-11a-p7Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICS.then click OK.1-11a-p8Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSReport #11-11a-p9Week 1: Introduct
13、ion to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSNote: X-bar chart shows unstable process, may be 2 different processesReport #21-11a-p10Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSYour capability
14、 study on “Percent Late Shipments” over the past four weeks has revealed at total of 400 “late” out of a total of 4000 shipments.Characterize process capability.What type of data? Attribute DataZshort term= 2.782 Zlong term= 1.282Example1 Defect = 1 late shipment4001 Unit = 1 shipment40001 opportuni
15、ty for defect per unit1Capability for Attributes Data1-11a-p11Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICS.then click OK.1-11a-p12Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICS
16、Note: ZBench = ZstTriangle shows that Zst is somewhere slightly less than 3.1-11a-p13Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSNote: Zst = “Zbench” = 2.782Zshift is assumed 1.5 for attribute dataZlt will be 1.5 worse than Zst. Thus, Zl
17、t = 2.782 -1.5 = 1.282Z(ST)=2.78and, thus,Z(LT)=1.281-11a-p14Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSExample:If a process has 10% reject rate, we would say it has a capability ofZ(LT)=1.28 andZ(ST)=2.78Z-Table for Attribute Data:%Rej
18、ected to Z(LT),thenZ(LT)+1.5=Z(ST)1-11a-p15Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSProcess Capability: The Concepts Behind The Calculations1-11a-p16Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W.
19、 Scott Lasater - GEICSY = Weight (lbs)220160100Process = Hose1 Drop = 1 Unit of OutputHistogram is .a pile of individual valuesDotplot : : : : . : . : : : : : : : : : : : : : . : . . :.: :.:.:.:.:.: : : : : . : . . -+-+-+-+-+-+-C1 100 125 150 175 200 2251-11a-p17Week 1: Introduction to Process Capab
20、ilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICS5 ft4 ft3 ft2 ft1 ft0 ftTimeWhat has changed?Centering? _Spread? _4.03.02.0Time1-11a-p18Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSDot Plots1st Observation2nd Observa
21、tion1.11.01.151.21.251.31.351.41.05Suppose we have a manufacturing line that is producing shafts.Diameters range from 1.0 to 1.4 inches. As we make a measurement of a shaft, we record the value with a dot on the above scaleEx:1st Observation = 1.4 inches2nd Observation = 1.1 inches1-11a-p19Week 1: I
22、ntroduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSAnd Suppose we continue sampling until 150 shafts have been measuredWhat Statements Can You Make About Our Process ? : :. . . :. : : : . :. .: : :. :.: .:.:.:.: .Dot Plots1.11.01.151.21.251.31.351.41.05
23、1-11a-p20Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICS : :. . . :. : : : . :. .: : :. :.: .:.:.:.: .Dot Plots1.11.01.151.21.251.31.351.41.05Now imagine the same data, grouped into intervals with bars used to represent how the data “looks”
24、.1-11a-p21Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSData represented just with the dots is called a Dot PlotUsing data represented in the above “bar format” is called a HistogramHistogram Distribution1.11.051.035302520151050Frequency1.
25、151.21.251.3 1.351.41-11a-p22Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSSo How Are We Doing?Are We Capable of Doing What the Customer Requires?7.7%92%What % will fall out here (outside the boundary)?LSLLSL1-11a-p23Week 1: Introduction t
26、o Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSHistogramNow weve combined the Histogram with our Lower and Upper Specifications.Question #1 : What are Specifications ? Where do they come from ?Question #2: What can you say about our process now ?1.11.01.151.21.2
27、51.31.351.41.05Upper SpecificationLower Specification.0012.01-11a-p24Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSHistogramSuppose the customer has given us new specifications !Question: What can you say about our process now ?1.11.01.151
28、.21.251.31.351.41.05Lower Specification1.1Upper Specification1.31-11a-p25Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSUCL and LCL versus USL and LSLUpper Control Limits = UCLLower Control Limits = LCLUpper Specification Limits = USLLower
29、Specification Limits = LSLIf a point falls beyond the UCL or LCL does this mean we aremaking a defective item for the customer ? UCLLCLTIMEY-axis(Response)1-11a-p26Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSUCL and LCL versus USL and LS
30、LUpper Control Limits = UCLLower Control Limits = LCLUpper Specification Limits = USLLower Specification Limits = LSLIs The Process Below Making Defective Items ? UCLLCLTIMEY-axis(Response)USLLSL1-11a-p27Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasa
31、ter - GEICSUCL and LCL versus USL and LSLUpper Control Limits = UCLLower Control Limits = LCLUpper Specification Limits = USLLower Specification Limits = LSLIs The Process Below Making Defective Items ? UCLLCLTIMEY-axis(Response)USLLSL1-11a-p28Week 1: Introduction to Process CapabilityGeneral Electr
32、ic ProprietaryDeveloped by W. Scott Lasater - GEICSThe Goal . . .1-11a-p29Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSPHASE ONE - Unpredictable Performance- VARIATION (SPECIAL / NATURAL CAUSES)- UNPREDICTABLE (HOURLY, DAILY)- DETECT AND
33、ELIMINATE SPECIAL CAUSES PHASE TWO - Stability- IN CONTROL- NATURAL VARIATION ONLYTimeHow We Progress Toward The GoalNot “capable” of getting all the water output into the clowns mouth?Which Approach To Use?Special Cause Strategy?Common Cause Strategy?1-11a-p30Week 1: Introduction to Process Capabil
34、ityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSIN CONTROL, BUT NOT CAPABLE(Variation from common causes excessive)IN CONTROL AND CAPABLE(Variation from common causes reduced)TimeHow We Progress Toward The GoalSIZELOWERSPECIFICATIONLIMITUPPERSPECIFICATIONLIMITNow it is “capable”
35、of getting all the water output into the clowns mouth - with extra elbow room for unexpected shifts & drifts (i.e., someone bumps your arm).Which Approach To Use?Special Cause Strategy?Common Cause Strategy?1-11a-p31Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W
36、. Scott Lasater - GEICSVariables Data0% RejectedTargetAttributes DataThe Goal Is .1-11a-p32Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICS(1) Pretending that I stay perfectly centered, is it even possible for this van to fit in there? (.A s
37、pread width issue)(2) Now, taking into consideration my past steering (centering) performance, am I able to make it without bumping the walls/boundaries (the customer specifications)?(.Both spread and centering issues)Its sort of like trying to drive a U-Haul moving van/truck through a tunnel.Z(Shor
38、t Term)Z(Long Term)“Short Term” Capability VS “Long Term” PerformanceLater, well discuss the importance and implications of consistency (stability over time) and the lack thereof. Spread: How would my estimating/predicting ability be affected if my trucks body had been unexpectedly expanding and con
39、tracting on occasion? Centering: How would my estimating/predicting ability be affected if my steering had been shifting significantly and unexpectedly every once in a while? 1-11a-p33Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICS LSLUSL1.
40、11.3 Capable? YesNoMeetingSpecifications? Capable? YesNoMeetingSpecifications? Capable? YesNoMeetingSpecifications? Capable? YesNoMeetingSpecifications? Z(ST)= Z(LT)= Z(ST)= Z(LT)= Z(ST)= Z(LT)= Z(ST)= Z(LT)= “Visual Estimates” of Sigma Levels:1-11a-p34Week 1: Introduction to Process CapabilityGener
41、al Electric ProprietaryDeveloped by W. Scott Lasater - GEICSNotes:1-11a-p35Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSCapability AnalysisRoadmapVariables Data(i.e., Continuous Data)Part 1StartEvidence of Inadequate Measurement Units?Spr
42、ead Stable? R or MR Chart show reasonable degree of Statistical Control?Calculate Z(st) or CpCentering Stable? X or X-Bar Chart show reasonable degree of Statistical Control?Histogram, NML Plot, and NML Test Indicate Normality?Calculate Z(Lt) or CpkData is too discrete. Control Charts and Capability
43、 Indices unreliable. Need to improve Meas. Process.YESTake necessary steps to address special causesTake steps to address special causes & calculate rough guess of “Pseudo-Capability” = Z(Lt)(see comments in Figure 1.1)NONOYESYESNOYESNOConsider another distribution to describe the process. Need tran
44、sformation? See Next Page. Call BB,MBBHas activity of Sources of Variation been thoroughly considered relative to subgrouping structure?YES1-11a-p36Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSAppendix #1Probability and Area Under a “Norm
45、al Distribution” Curve (1) via Minitab(2) Normal Tables (i.e., Z-Tables)1-11a-p37Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSNormal Distribution (Lower Tail Areas)I have the Z value = -1.42, and need “area” (Lower Tail Area)Area=0.0778 Z
46、= -1.4201-11a-p38Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSNormal Distribution (Lower Tail Areas)I have the Z value = +1.42, and need “area” (Lower Tail Area)Area=0.9222 Z=+1.4201-11a-p39Week 1: Introduction to Process CapabilityGeneral Electric ProprietaryDeveloped by W. Scott Lasater - GEICSThe Card Drop Exercise(modified)(1) Determine the “%Rejects” for each process step(2) Determine Capability (Z) for each process step. (Optional)
