111al process capability strategies.ppt

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1、Process Capability Analysis,Overview Brief,Collect Timely Data,Process Stable/Consistent?(SPC),Process Acceptable?(Capability,Z),Develop measures with respect to standards,Identify standards(specs)that address customer requirements(CTQs),Yes,No*,Yes,ANALYZE PHASE,Use“Special Cause Strategy”(How to i

2、mprove an unstable system)Act quickly to search for the cause:What was DIFFERENT?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)Exp

3、erimentation(DOE)Disaggregation(Break into components),“Message is in ALL the points”,MEASURE PHASE,Focus,Define,Process Map,C&E,FMEA,etc.,Evaluate Measurement System(MSA),IMPROVE PHASE,Plan&Implement Short-Term Remedy(Immediate Containment)Plan&Implement Long-Term RemedyVerify Impact/Success(Before

4、 Vs After),Plan&Implement Long-Term RemedyVerify Impact/Success(Before Vs After),CONTROL PHASE,Modify Control Plans:Hold GainsComplete Hand-Off ActivitiesEnsure New Procedures Are Used and Are EffectiveMonitor for Innovation&Improvement OpportunitiesMonitor Ever-Changing Customer Needs and Requireme

5、nts,No,*=This data from an unstable,unpredictable process 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-GEICS,DEFINE,Wh

6、at sorts of data do you see being collected around your area?,(List them below),_,Attributes Data,Variables Data,How To Get Capability Indices Via Minitab,(1)Variables Data(2)Attributes data,.A Quick Look,Open file“Capab_v.mtw”.Characterize process capability.LSL=40 and USL=100What type of data is t

7、his(Attribute or Variables)?VariablesZshort term=4.67 Zlong term=3.74,Your 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)?Attribut

8、e Zshort term=2.782 Zlong term=1.282,Important Note:X-bar chart shows unstable process-may even be 2 different processes.,Minitab Command:Six Sigma/Process Report/Single Column Output/Subgroup size subgroup,(see next pages for details),Capability for Variables Data,Open file“Capab_v.mtw”.Characteriz

9、e process capability.LSL=40 and USL=100What type of data?Variables DataZshort term=4.67 Zlong term=3.74,Important Note:X-bar chart shows unstable process-may even be 2 different processes.,.then click OK.,Report#1,Note:X-bar chart shows unstable process,may be 2 different processes,Report#2,Your cap

10、ability 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=1.282,Example1 Defect=1 late shipment4001 Unit=1 shipment40001 opportunity

11、for defect per unit1,Capability for Attributes Data,.then click OK.,Note:ZBench=ZstTriangle shows that Zst is somewhere slightly less than 3.,Example:If a process has 10%reject rate,we would say it has a capability ofZ(LT)=1.28 andZ(ST)=2.78,Z-Table for Attribute Data:%Rejected to Z(LT),thenZ(LT)+1.

12、5=Z(ST),Process Capability:The Concepts Behind The Calculations,Y=Weight(lbs),220,160,100,Process=Hose,1 Drop=1 Unit of Output,Histogram is.a pile of individual values,Dotplot,:.:.:.:.:.:.:.:.:.:.:.:.-+-+-+-+-+-+-C1 100 125 150 175 200 225,Dot Plots,1st Observation,2nd Observation,1.1,1.0,1.15,1.2,1

13、.25,1.3,1.35,1.4,1.05,Suppose 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 inches,And Suppose we continue sampling unt

14、il 150 shafts have been measuredWhat Statements Can You Make About Our Process?,:.:.:.:.:.:.:.:.:.:.:.,Dot Plots,1.1,1.0,1.15,1.2,1.25,1.3,1.35,1.4,1.05,:.:.:.:.:.:.:.:.:.:.:.,Dot Plots,1.1,1.0,1.15,1.2,1.25,1.3,1.35,1.4,1.05,Now imagine the same data,grouped into intervals with bars used to represe

15、nt how the data“looks”.,Data represented just with the dots is called a Dot PlotUsing data represented in the above“bar format”is called a Histogram,Histogram Distribution,Histogram,Now weve combined the Histogram with our Lower and Upper Specifications.Question#1:What are Specifications?Where do th

16、ey come from?Question#2:What can you say about our process now?,Histogram,Suppose the customer has given us new specifications!Question:What can you say about our process now?,1.1,1.3,UCL and LCL versus USL and LSL,Upper Control Limits=UCLLower Control Limits=LCL,Upper Specification Limits=USLLower

17、Specification Limits=LSL,If a point falls beyond the UCL or LCL does this mean we aremaking a defective item for the customer?,TIME,Y-axis(Response),UCL and LCL versus USL and LSL,Upper Control Limits=UCLLower Control Limits=LCL,Upper Specification Limits=USLLower Specification Limits=LSL,Is The Pro

18、cess Below Making Defective Items?,UCL,LCL,TIME,Y-axis(Response),USL,LSL,UCL and LCL versus USL and LSL,Upper Control Limits=UCLLower Control Limits=LCL,Upper Specification Limits=USLLower Specification Limits=LSL,Is The Process Below Making Defective Items?,UCL,LCL,TIME,Y-axis(Response),USL,LSL,The

19、 Goal.,PHASE ONE-Unpredictable Performance,-VARIATION(SPECIAL/NATURAL CAUSES),-UNPREDICTABLE(HOURLY,DAILY),-DETECT AND ELIMINATE SPECIAL CAUSES,PHASE TWO-Stability,-IN CONTROL,-NATURAL VARIATION ONLY,How We Progress Toward The Goal,Not“capable”of getting all the water output into the clowns mouth?,W

20、hich Approach To Use?Special Cause Strategy?Common Cause Strategy?,IN CONTROL,BUT NOT CAPABLE,(Variation from common causes excessive),IN CONTROL AND CAPABLE,(Variation from common causes reduced),How We Progress Toward The Goal,Now it is“capable”of getting all the water output into the clowns mouth

21、-with extra elbow room for unexpected shifts&drifts(i.e.,someone bumps your arm).,Which Approach To Use?Special Cause Strategy?Common Cause Strategy?,Variables Data,0%Rejected,Target,Attributes Data,The Goal Is.,(1)Pretending that I stay perfectly centered,is it even possible for this van to fit in

22、there?(.A spread 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.

23、,Z(Short Term),Z(Long Term),“Short Term”Capability VS“Long Term”Performance,Later,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 c

24、ontracting 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?,Notes:,Capability AnalysisRoadmapVariables Data(i.e.,Continuous Data)Part 1,Start,Evidence of Inadequate Measurement Units?,S

25、pread Stable?R or MR Chart show reasonable degree of Statistical Control?,Calculate Z(st)or Cp,Centering Stable?X or X-Bar Chart show reasonable degree of Statistical Control?,Histogram,NML Plot,and NML Test Indicate Normality?,Calculate Z(Lt)or Cpk,Data is too discrete.Control Charts and Capability

26、 Indices unreliable.Need to improve Meas.Process.,YES,Take necessary steps to address special causes,Take steps to address special causes&calculate rough guess of“Pseudo-Capability”=Z(Lt)(see comments in Figure 1.1),NO,NO,YES,YES,NO,YES,NO,Consider another distribution to describe the process.Need t

27、ransformation?See Next Page.Call BB,MBB,Has activity of Sources of Variation been thoroughly considered relative to subgrouping structure?,YES,Appendix#1,Probability and Area Under a“Normal Distribution”Curve(1)via Minitab(2)Normal Tables(i.e.,Z-Tables),Normal Distribution(Lower Tail Areas),I have the Z value=-1.42,and need“area”(Lower Tail Area),Normal Distribution(Lower Tail Areas),I have the Z value=+1.42,and need“area”(Lower Tail Area),The Card Drop Exercise(modified),(1)Determine the“%Rejects”for each process step(2)Determine Capability(Z)for each process step.,(Optional),