2012 SQC Parrillo M
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Transcript of 2012 SQC Parrillo M
Michael ParrilloASQ; CQE, CRE, CSSGB, CSSBB, CMQ/OE, CQA
http://www.linkedin.com/in/parrilloasq
WHAT IS MSA? A means to determine the percent of variation
between operator, gauge, and process in a measuring procedure.
WHY? Variation exists in all measuring processes.
Operator performance will vary from day to day and operator to operator
Gauge may or may not be adequate for it’s intended use
Process may or may not be adequate for it’s intended use
FISHBONE EXERCISE SWIPE
Standard
Workpiece
Instrument
Person/Process
Environment
FISHBONE EXERCISE
BASICS Definition Uncertainty
Discrimination
Linearity
Stability
True Value
Bias
Reference Value
Repeatability
Reproducibility
UNCERTAINTY Uncertainty is a quantified expression of measurement
reliability that describes the range of a measurement result within a level of confidence.
Estimating uncertainties is a vast subject which in itself can take quite a bit of effort to master. Suggested reading on this subject is ANSI/NCSL Z540.3 (appendix A is particularly helpful), and ISO/IEC Guide to the Expression of Uncertainty in Measurement (GUM). Also, the following documents can be found on the internet free of charge; NIST Technical Note 1297, EA 4/02, and M3003.
TYPE “A” AND TYPE “B” Type “A” uncertainties are quantified by statistic and include
studies such as: Accuracy Linearity Repeatability Reproducibility
Type “B” uncertainties can not be evaluated by statistic and include
Temperature Errors Fixture variation Calibration
UNCERTAINTY BUDGETSource % Uncertainty *Divisor X X²
Repeatability 1.3 1 1.3 1.69
Reproducibility 4.02 1 4.02 16.1604
DUT Certification .03 2 .015 .000225
Total 17.8506
RSS 4.225
**Expanded (K=2) 8.45%
DISCRIMINATION (RESOLUTION) Smallest scale unit of measure for an instrument
10 to 1 rule +/- .005 inch?
.005/10 = .0005 inch
.005/4 = .00125 inch
Requirement varies based on application
Cost of gage must be considered and weighed against ROI (Micrometer-$200, or optical comparator-$15,000)
Disposable toothbrushes – Airplane tires
DISCRIMINATION FOUND ON SPC RANGE CHART
Not recommended If:3 or less values are displayed on the chart orMore that ¼ of the values are 0
NUMBER OF DISTINCT CATAGORIES This number represents the ability of your measurement
device to segment the total range of values.
AIAG recommends a minimum of 5 ndc
If you require more ndc than the study determined Run the study with more parts that represent the
entire range Improve the measurement tool to deliver more
precision
NUMBER OF DISTINCT CATAGORIES
There is a mathematic relation between ndc and
% Total Variation
You will need less than approximately 27% Total Variation to have a minimum of 5 ndc
LINEARITY Collective variation over the range of measurement
If gage gains .1 inch per foot and you measure 6 inches than variation in linearity may be .05 of your range
This “may” be acceptable if tolerance is +/- 1 one inch and total length measured is 6 inches.
This would not be acceptable if total length is over 10 feet
.1 x 10 = 1”
LINEARITY STUDY Choose 5 parts representing the full range of values
Determine each parts reference value
Have best operator randomly measure each part 12 times
Determine bias of each part
Enter data in software to create linearity plot
LINEARITY PLOT
LINEARITY RESULTS Result is a linearity problem
R-Sq is only 71.4% (0 to 100% - Larger better)
Bias line intercepted by regression line (Unacceptable if significantly different than “0”)
Distribution is bimodal (7 data points at value 4 & 6)
STABILITY (Drift) The change in the difference between measurement
value and reference value over time
Electronic instruments may change over time due to the drifting of values
Operators may deviate in methods over time
Temperature may vary over time (or per day)
DETERMINING STABILITY Obtain a part to use as a master reference value
Can be done by averaging repetitive measurements of a master over time
Measure this master 5 times per shift over four weeks until at least 20 subgroups are obtained
Plot the data on Xbar/R Chart
Monitor using standard SPC analysis for special cause
DETERMINING STABILITY
REPEATABILITY Variation in measurements obtained with one
measuring instrument when used several times by an operator while measuring the identical characteristic on the same part (AIAG).
Commonly referred to as Equipment Variation (E.V.)
Variation in the gage
POOR REPEATABILITY Part – Surface, position, consistency of part
Instrument – Repair, wear, fixture, maintenance
Standard – Quality, wear
Method - Variation, technique
Appraiser – Technique, experience, fatigue
Environment – Temperature, humidity, vibration, lighting, cleanliness
Assumptions – Stable
REPRODUCABILITY Variation in the average of the measurements made by
different operators using the same gage when measuring a characteristic on one part
Commonly referred to as Appraiser variation (A.V.)
POOR REPRODUCABILITY Part – Between part variation
Instrument – Between instrument variation
Standard – Influence of different settings
Method – Holding & clamping methods, zeroing
Appraisers – Between appraiser variation, training, skill, experience
Environment – Environmental cycles
Assumptions – Stability of process
R & R ACCEPTABILITY Under 10% - Acceptable
10 – 30% - May be acceptable based on application
Over 30% - Not acceptable
BIAS (ACCURACY) Bias is the difference between observed measurement
and reference value (AIAG)
True value is the actual value of the artifact
Unknown and unknowable
Reference Value is the accepted value of an artifact
Artifacts or reference materials can be used to calibrate instruments or to validate measurement methods.
BIAS (ACCURACY) Possible causes
Out of calibration
Worn or damaged fixture, equipment, instrument
Wrong gage
Environmental conditions
Operator skill level, performed wrong method
http://thequalityportal.com/q_forms.htm
Gage R & R
Study
Worksheet
Note - We received two complaints regarding the calculation used in this form - please refer to the comment in Cell i43. Date:
Gage Number: Part Number:
Gage Cert. Level: Part Name:
Gage Cert. Date: Characteristic:
Gage Build Source: Engineering Level:
Operator: A B C
No Operators: 3 Tolerance: 1.02
Number of Trials: 3 Number of Parts: 10
Trial Part
Operator Number 1 2 3 4 5 6 7 8 9 10 Average
A 1 0.29 -0.56 1.34 0.47 -0.80 0.02 0.59 -0.31 2.26 -1.36 0.19
2 0.41 -0.68 1.17 0.50 -0.92 -0.11 0.75 -0.20 1.99 -1.25 0.17
3 0.64 -0.58 1.27 0.64 -0.84 -0.21 0.66 -0.17 2.01 -1.31 0.21
Average 0.45 -0.61 1.26 0.54 -0.85 -0.10 0.67 -0.23 2.09 -1.31 X-bar 0.19
Range 0.35 0.12 0.17 0.17 0.12 0.23 0.16 0.14 0.27 0.11 R-bar 0.18
Trial Part
Operator Number 1 2 3 4 5 6 7 8 9 10 Average
B 1 0.08 -0.47 1.19 0.01 -0.56 -0.20 0.47 -0.63 1.80 -1.68 0.00
2 0.25 -1.22 0.94 1.03 -1.20 0.22 0.55 0.08 2.12 -1.62 0.12
3 0.07 -0.68 1.34 0.20 -1.28 0.06 0.83 -0.34 2.19 -1.50 0.09
Average 0.13 -0.79 1.16 0.41 -1.01 0.03 0.62 -0.30 2.04 -1.60 X-bar 0.07
Range 0.18 0.75 0.40 1.02 0.72 0.42 0.36 0.71 0.39 0.18 R-bar 0.51
Trial Part
Operator Number 1 2 3 4 5 6 7 8 9 10 Average
C 1 0.04 -1.38 0.88 0.14 -1.46 -0.29 0.02 -0.46 1.77 -1.49 -0.22
2 -0.11 -1.13 1.09 0.20 -1.07 -0.67 0.01 -0.56 1.45 -1.77 -0.26
3 -0.15 -0.96 0.67 0.11 -1.45 -0.49 0.21 -0.49 1.87 -2.16 -0.28
Average -0.07 -1.16 0.88 0.15 -1.33 -0.48 0.08 -0.50 1.70 -1.81 X-bar -0.25
Range 0.19 0.42 0.42 0.09 0.39 0.38 0.20 0.10 0.42 0.67 R-bar 0.33
Part
Average0.17 -0.85 1.10 0.37 -1.06 -0.19 0.45 -0.34 1.94 -1.57 Rp 3.51
R & R 0.30577 %EV 19.8% %EV-TV 17.61% R-Bar 0.3417
Equipment Variation: 0.20186 Part Var: 1.10460 %AV 22.5% %AV-TV 20.04% X-Dif 0.4447
Appraiser Variation: 0.22967 Total Var: 1.14613 %RR 30.0% %RR-TV 26.68% UCLr 0.8815
repeatability 0.04 R&R 0.05937Notes %PV-TV 96.38% LCLr 0.00
reproducibility 0.04 TV 0.22255 ndc 5 Min %RR 26.68% Max Range 1.0200
Criteria < 30% Pass/Fail Pass Stable? No
Per
cent
Part-to-PartReprodRepeatGage R&R
100
50
0
% Contribution
% Study Var
Sam
ple
Ran
ge
0.002
0.001
0.000
_R=0.000533
UCL=0.001743
LCL=0
Harish Pankaj Pramod
Sam
ple
Mea
n
0.08
0.06
0.04
__X=0.04627UCL=0.04727LCL=0.04526
Harish Pankaj Pramod
OperatorPart
PramodPankajHarish151413121110987654321
0.08
0.06
0.04
OperatorPramodPankajHarish
0.08
0.06
0.04
Gage name: V ision Microscope
Date of study : 12-20-06
Reported by: Mike Parrillo
Tolerance: +/- .001 inch
Misc: Accuracy .0001 inch
Components of Variation
R Chart by Operator
Xbar Chart by Operator
Response By Part ( Operator )
Response by Operator
Jacket Line Measurement Analysis, ANOVA
EXAMPLE
EXAMPLEP
erce
nt
Part-to-PartReprodRepeatGage R&R
100
50
0
% Contribution
% Study Var
Sam
ple
Ran
ge
0.0010
0.0005
0.0000
_R=0.0004
UCL=0.001307
LCL=0
Jay Kirte Nick
Sam
ple
Mea
n 0.020
0.016
0.012
__X=0.01593UCL=0.01669
LCL=0.01518
Jay Kirte Nick
OperatorPart
NickKirteJay151413121154321109876
0.020
0.015
0.010
OperatorNickKirteJay
0.020
0.015
0.010
Gage name: V ision Microscope
Date of study : 12-20-06
Reported by: Mike Parrillo
Tolerance: +/- .001 inch
Misc: Accuracy .0001 inch
Components of Variation
R Chart by Operator
Xbar Chart by Operator
Response By Part ( Operator )
Response by Operator
Primary Line Measurement Analysis, ANOVA
ATTRIBUTE STUDY A study comparing categories as opposed to
measurements.
Go/No Go gages, classifications such as good, fair, poor, unacceptable.
Involves human judgment which may vary
ATTRIBUTE STUDY Collect minimum of 30 samples that span the entire
range
Determine reference value of each sample
Have three operators measure each part 3x (Unaware of reference value, or part number). Total inspected 90
ATTRIBUTE STUDY Determine
How often did each appraiser pass the same part
How often did each appraiser fail the same part
How often did appraiser “A” pass and “B” fail
How often did appraiser “B” pass and “A” fail
Compare all appraisers in combinations (A &B, A & C, B & C)
Determine expected CT/GT*RT (CT-Column Total, GT- Grand Total, RT- Row Total)
ATTRIBUTE STUDYAppraiser “A”
Appraiser “B”
Pass Fail Total
Pass CountExpected
248.4
419.6
2828
Fail CountExpected
318.6
5943.4
6290
Total CountExpected
2727
6363
9090
Cohen’s Kappa P observed – p expected/1-p expected
From 0 to 1
0 - no agreement
1 - complete agreement
.80 – 1 Very good
.60 - .80 Good
.40 - .60 Moderate
.20 - .40 Fair
> .20 Poor
Cohen’s Kappa P observed (Agreement) = (24 + 59)/90 = .922
P expected (Agreement) = (8.4 + 43.9)/90 = .576
.922 - .576/1 - .576 = .82
Calculate tables for each combination of appraisers.
Calculate Cohen’s Kappa for each combination of appraisers.
Review results and act appropriately
ATTRIBUTE STUDY If Cohen’s Kappa is under minimum requirement:
Appraiser – Interpretation, eyesight, skill level, method
Organization – Procedure, training, peer/management pressure, fatigue
Bibliography Automotive Industry Action Group (AIAG) (2002).
Measurement Systems Analysis Reference Manual, 3rd edition. Chrysler, Ford, General Motors Supplier Quality Requirements Task Force.
Minitab - Understanding "Number of distinct categories" in Gage R&R output - ID 276
http://thequalityportal.com/q_forms.htm
Michael ParrilloASQ; CQE, CRE, CSSGB, CSSBB, CMQ/OE, CQA
http://www.linkedin.com/in/parrilloasq