Lean与六西格玛培训第7课：Process Capbility

Process Capability Analysis,Intelligent, Creative and Sustainable Solutions that Elevate Brands and Accelerate Performance Throughout the Global Retail Supply Chain,May 2015,Kenny,Operational ExcellencePanyu / China,Module Objectives,Understand Capability StudyShort Vs Long Term StudyUnderstand the Implication of Capability Study,Capability Analysis Aims to Answer.,ARE OUR CUSTOMERS EXPECTATIONS BEING MET?       How are we doing? How well could we be doing?           What can we expect tomorrow, next week?         Which supplier is giving us the best quality?,Capability,A process is capable if it is able to produce a good quality product consistently,Specification,Lower and upper specification limits define the customers view of the spread acceptable of a product attribute or a process result.,Lower Specification Limit (LSL),Specification width or                 tolerance width,Upper Specification Limit (USL),Any products that build beyond the spec limits are considered scraps or reworks.,A Statistic Look of Capability Study,No Capable,Capable,Process Capability Indices,Cp Potential Capability Also called “process entitlement” or the “best” your process could ever hope to perform in the short-term,Total tolerance range just enough to cover +/- 3 sigma if Cp=1,For one sided specification, one sided Cp is defined,Since s always unknown, then,Cp = Cpk when the process is well centered.,Cpkuse the mean, not only the tolerance band to estimate capability therefore taking account of off-centredness.  The term “min (Cpk(l), Cpk(u)” is stated as the shortest numerical distance between the mean and the nearest spec limit.,Process Capability Indices,Cpk = min Cpu, Cpl,Example,In semiconductor manufacturing, gate oxide might be specified for: Lower Spec Limit = 210 Angstroms Target thickness = 240 Angstroms Upper Spec Limit = 270 AngstromsIf we assume that the process data indicates that the mean thickness is actually 247 Angstroms with standard deviation of 5 angstroms.,Warm up Exercise : The Application of Cp & Cpk,3 suppliers being tested of the same products on one of the critical parameter. (3 factories worksheet) Whats the respectively Cp & Cpk for these 3 factories considered the spec of 26.533 ? Whats the best supplier that you would like to work with? Why? (Hint: Please estimate the defectives rate base on the normal curve characteristic)Is there the relationship in between the Cpk and defectives rate?,A,B,C,Repeat the exercise but with Minitab,3 suppliers being tested of the same products on one of the critical parameter. (3 factories worksheet) Whats the respectively Cp & Cpk for these 3 factories considered the spec of 26.533 ? Whats the best supplier that you would like to work with? Why? (Hint: Please estimate the defectives rate base on the normal curve characteristic)Is there the relationship in between the Cpk and defectives rate?,A,B,C,Whats the minimum Cpk requirements on each supplier ? Why?,0,1     2    3,-3   -2    -1,Standard Normal Distribution when m = 0 and s = 1.,Standard Normal Distribution,This transform converts any normal distribution into a “standard” normal distribution.,The Z Transformation,REAL World,Z World,Example : Compute the Z score of spec limits,2.25 sigma away from the mean on the left,2.75 sigma away from the mean on the right,-2.25,2.75,5,15,Estimate the defectives rate from the Z-score by Minitab,Find the probability of X < 5 (or Z < -2.25) using Minitab,CalcProbability DistributionsNormal,1 - 0.99702 = 0.00298,%Defective = (0.0122245+0.00298)*100% = 1.5205% DPPM = 15,205,Process Capability Study for Discrete Data,Example,Example,Long Term Process Capability :Total variation including shifts and driftsPp and Ppk,Short Term Process Capability :Only random or short-term variationCp and Cpk,Rational Sub-grouping & Long Term Capabilities Study,Long Term vs Short Term,Short Term,Short Term,Short Term,Short Term,Short Term,Short Term,Short Term,Long Term,To have good estimation of Short Term and Long Term, collect data in subgroup over time (cover all the foresee-able variations). Example :    Worksheet : SubgroupUSL : 15LSL : 4,EXAMPLE (4),Long Term vs Short Term,StatQuality ToolsCapability AnalysisNormal,Long Term vs Short Term,Long Term vs Shor