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ISO/TS 16949:2009(E) and AIAG MSA 4 th edn. (2010). Martin Gibson CStat, CSci, MSc, MBB AQUIST Consulting gg1000@waitrose.com. 1. Making sense of MSA. Do you know how accurate and precise your measurement and test equipment are?
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ISO/TS 16949:2009(E) andAIAG MSA 4th edn. (2010) Martin Gibson CStat, CSci, MSc, MBB AQUIST Consulting gg1000@waitrose.com RSS Destructive Testing MSA 1
Making sense of MSA • Do you know how accurate and precise your measurement and test equipment are? • Do you suspect that good work is sometimes condemned as bad simply because of uncertainty in the measurement system; is bad work ever released as good? • Do you know the cost of non-capable measurement systems? • Do you realise how important it is to understand measurement systems uncertainty? • Does your auditor share your understanding of measurement systems? • What can you do about it? RSS Destructive Testing MSA 2
ISO/TS 16949:2009(E)7.6.1 Measurement System Analysis • Statistical studies shall be conducted to analyse the variation present in the results of each type of measuring and test equipment system. • ... applies to measurement systems in the control plan. • ... analytical methods and acceptance criteria used shall conform to those in customer reference manuals on MSA. • Other analytical methods and acceptance criteria may be used if approved by the customer. Questions: • What is the operational definition of statistical studies? • Do organisations, auditors, quality mangers understand statistical studies? • Why do auditors ask?, “Can you show me GR&R studies for each type of measuring and test equipment system referenced in the control plan?” RSS Destructive Testing MSA 3
ISO/TS 16949 Scheme Update IF SMMT Webinar, 5 Nov. 2013 Common problems found in ISO/TS16949 audits • Calibration and MSA (7.6 and 7.6.1) • Definition of Laboratory scope • Control of external laboratories • Traceability to national or international standards • MSA not done for all types of measuring systems • MSA only considering gauge R and R Questions: • Why is MSA regarded as GR&R? RSS Destructive Testing MSA 4
Ford Motor Company MSA requirements (2009) 4.35 (ISO/TS 16949 cl. 7.6.1) All gauges used for checking Ford components/parts per the control plan shall have a gauge R&R performed in accordance with the appropriate methods described by the latest AIAG MSA to determine measurement capability. • Variable gauge studies should utilize 10 parts, 3 operators & 3 trials • Attribute gauge studies should utilize 50 parts, 3 operators & 3 trials Questions: • Are some Customers leading the thinking? • Why just limited to products? • What are your Customer expectations? RSS Destructive Testing MSA 5
Measurement System Variation Observed Variation = Process Variation + Measurement System Variation Bias Accuracy Linearity Calibration Measurement System Variation Stability Repeatability Precision Gauge R&R Reproducibility RSS Destructive Testing MSA 6
AIAG MSA 4th edn. (2010) • Accuracy, Bias, Stability, Linearity, Precision, Repeatability, Reproducibility, GR&R • Attributes, Variables, & non-replicable data considered • Variables GR&R study • 10 parts, 3 operators, 3 measurements • Parts chosen from 80% of tolerance • Destructive testing requires 90 parts from a homogeneous batch • Three analytical methods: • Range – basic analysis, no estimates of R&R • Average & Range – provides estimates of R&R • ANOVA – preferred, estimates of parts, appraisers, parts*operators interaction, replication error due to gauge Question: • Do organisations, auditors, quality mangers understand MSA? RSS Destructive Testing MSA 7
AIAG ANOVA Models • Crossed vs. Nested • Y ijk= μ + Operator i+ Part j+ (Operator*Part) ij+ ε k(ij) • Y ijk = + Operator i + Part j(i) + (ij)k • Crossed vs. Nested? • See Barrentine, Moen, Nolan & Provost, Bower, Burdick, Skrivanek • Fixed vs. mixed effects models? • Software? • MTB V16+ includes fixed, mixed effects, enhanced models, pooled standard deviation approach not included. • SPC for Excel – fixed effects • Other software packages? Question: • Do organisations, auditors, quality mangers understand ANOVA? RSS Destructive Testing MSA 8
% Contribution • ndc • % Study Variation • % Tolerance • > 9% Unacceptable • < 5 Unacceptable • > 30% Unacceptable • > 30% Unacceptable • 2-9% Acceptable • 5-10 Acceptable • 11-30% Acceptable • 11-30% Acceptable • < 1% Good • > 10 Good • < 10% Good • < 10% Good GR&R Variables Data Acceptance Criteria • % Contribution • Measurement System Variation as a percentage of Total Observed Process Variation using variances (additive) • % Study Variation • Measurement System Standard Deviation as a percentage of Total observed process standard deviation (not additive) • % Tolerance • Measurement Error as a percentage of Tolerance • Number of Distinct Categories (ndc) • Measures the resolution of the scale • Do organisations, auditors, quality mangers understand the metrics?
Non-replicable GR&R case study (Anon, 2002) • Ensure that all the conditions surrounding the measurement testing atmosphere are: • defined, standardized and controlled • appraisers should be similarly qualified and trained • lighting should be adequate and consistently controlled • work instructions should be detailed and operationally defined • environmental conditions should be controlled to an adequate degree • equipment should be properly maintained and calibrated, failure modes understood, etc.
Non-replicable GR&R case study (Anon, 2002) • If the overall process appears to be stable & capable, and all the surrounding pre-requisites have been met, it may not make sense to spend the effort to do a non-replicable study since the overall capability includes measurement error – if the total product variation and location is OK, the measurement system may be considered acceptable. • Ironically high Cp / Cpk gives poor ndc! Question: • Do organisations, auditors, quality mangers understand this concept? AIAG FAQs response: • If your process is stable and capable, the spread of this acceptable process distribution includes your measurement error. There may be no need to study your measurement error from a purely "acceptability" viewpoint.’
Questions for Making sense of MSA • What is the operational definition of statistical studies? • Do organisations, auditors, quality mangers understand statistical studies? • Why do auditors ask for GR&R studies? • Why is MSA regarded as GR&R? • Are (some) Customers leading the thinking? • Why is MSA limited to products? • Do you know your Customer expectations? • Do organisations, auditors, quality mangers understand? • MSA, ANOVA, crossed vs. nested, fixed vs. mixed models, metrics, high Cp/Cpk gives low ndc? • Is MSA seen just as a QMS requirement or a true part of continuous improvement? RSS Destructive Testing MSA 12
References • AIAG Measurement System Analysis, 4th edn., (2010) • Anon. Non-replicable GR&R case study, (circa 2002) • Barrentine, Concepts for R&R Studies, 2nd edn., ASQ, (2003) • Bower, A Comment on MSA with Destructive Testing, (2004) ; see also keithbower.com • Gorman & Bower, Measurement Systems Analysis and Destructive Testing, ASQ Six Sigma Forum Magazine, (August 2002, Vol. 1, No. 4) • Burdick, Borror & Montgomery, A review of methods for measurement systems capability analysis; JQT, 35(4): 342-354, (2003) • Burdick, Borror & Montgomery, Design & Analysis of Gauge R&R Studies, SIAM, ASA, (2005) • Moen, Nolan & Provost, “using a Nested Design for quantifying a destructive test” in Improving Quality Through Planned Experimentation, McGraw-Hill; 1st edn., (1991) • Skrivanek, How to conduct an MSA when the part is destroyed during measurement, moresteam.com/whitepapers/nested-gage-rr.pdf