23 Measurement Systems Analysis for detail study.ppt

Content teach you what is MSA

1. © ABSL Power Solutions
2007
© STM Quality Limited
STM Quality
Limited
Measurement Systems
Analysis
TOTAL QUALITY MANAGEMENT
M.S.A.

2. © STM Quality Limited
STM Quality
LimitedOutline and Objectives
Introduce Measurement Systems
Assess Measurement Systems Performance
Understand Measurement System Variation

3. © STM Quality Limited
STM Quality
LimitedRequirements for M.S.A.
•TS16949 Clause 7.6.1. states:
•Statistical studies shall be conducted to analyse the
variation present in the results of each type of
measuring and test equipment system. This
requirement shall apply to measurement systems
referenced in the control plan. The analytical methods
and acceptance criteria used shall conform to those in
customer reference manuals on measurement
systems analysis. Other analytical methods and
acceptance criteria may be used if approved by the
customer.

4. © STM Quality Limited
STM Quality
LimitedProcess Control
People
Methods
Material
Equipment
Environment
A Typical Process
Input
PROCESS
Process / System
Product
Output
Identifying
Improvement
Opportunities
Accurate Measurement
using Measurement System Analysis

5. © STM Quality Limited
STM Quality
LimitedNew Process Acceptance
Observed Process
Variation
Actual Process
Variation
Production Gauge
Variation

6. © STM Quality Limited
STM Quality
Limited
Assessing
Measurement Systems
Location variation
–Bias
–Stability
Width variation
–Linearity
–Repeatability, Reproducibility

7. © STM Quality Limited
STM Quality
Limited
Determining and Assessing
Bias
Bias is the difference between
the observed average of
measurement and the
reference value.
The reference value, also
known as the accepted
reference value or master
value, is a value that serves as
an agreed-upon reference for
the measured values. A
reference value can be
determined by averaging
several measurements with a
higher level of measuring
equipment.
Reference
Value
Observed
Average Value
Bias

8. © STM Quality Limited
STM Quality
Limited
Determining and Assessing
Stability
Stability (or drift) is the total
variation in the measurements
obtained with a measurement
system
•on the same master or part
when measuring a single
characteristic
•over an extended
time period
Reference Value
Time

9. © STM Quality Limited
STM Quality
Limited
Determining and Assessing
Linearity
Linearity is the difference in the bias values through the
expected operating range of the gauge.
Reference
Value
50mm
Observed
Average Value
Smaller
Bias
200mm
Reference
Value
Observed
Average Value
Larger
Bias

10. © STM Quality Limited
STM Quality
LimitedDetermining Repeatability
Repeatability is the variation
in measurements obtained
•By one appraiser
•with one measurement
instrument
•when used several times
•while measuring the
identical characteristic
•on the same part Repeatability

11. © STM Quality Limited
STM Quality
LimitedDetermining Reproducibility
Reproducibility is the variation
in the average of the
measurements made
•by different appraisers
•using the same measuring
instrument
•when measuring the
identical characteristic
•on the same part
Reproducibility

12. © STM Quality Limited
STM Quality
Limited
Preparing For A
Measurement System Study
Variable Gauge Study (Average and Range Method)
The average and range method of gauge study breaks the gauge
error into repeatability and reproducibility.
Optimum conditions:
•3 operators;
•3 trials;
•10 parts.
Study of the results can provide information concerning the causes
of the measurement error.
If reproducibility is large compared to repeatability then;
•The operator is not properly trained in how to use and read the
gauge;
•Graduations on the gauge are not clear.

13. © STM Quality Limited
STM Quality
Limited
Determining and Assessing
Repeatability and Reproducibility
There are three methods:
Range Method;
Average and Range Method;
Analysis of Variation Method (ANOVA).

14. © STM Quality Limited
STM Quality
Limited
Determining and Assessing
Repeatability and Reproducibility
Range Method
Gives a quick approximation of measurement variability. It does not
decompose the variability into repeatability and reproducability.
Conducted with 2 appraisers and 5 parts;
Each appraiser measures each part once;
Evaluate the range at each part;
Estimate the variation between the measurement results over the
average Range (R/d2);
Gauge R&R = 99%-area under the normal distribution curve
(2*2,576*variation).
(not sufficient for PPAP and QS-9000 clause 4.11.4)

15. © STM Quality Limited
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Determining and Assessing
Repeatability and Reproducibility
Average and Range Method
Evaluates Repeatability and Reproducibility separately;
Conducted typically with three appraisers and 10 parts;
Each appraiser measures each part three time in a random order;
Evaluation graphical or numerical;
EV (equipment variation) (99%- norm. distr.)
AV (appraiser variation) (99%- norm. distr.)
R&R (R&R)² = EV² + AV² (99%- norm. distr.)
Part Variation PV (99%- norm. distr.)
Total VariationTV² = (R&R)² + PV²(99%- norm. distr.)

16. © STM Quality Limited
STM Quality
Limited
Determining and Assessing
Repeatability and Reproducibility
Analysis of Variation Method
Evaluates Repeatability and Reproducibility separately;
Evaluates Interaction between appraiser and part;
Conducted typically with three appraisers and 10 parts;
Each appraiser measures each part three time in a random order;
Evaluation graphical or numerical;
EV (equipment variation) (99%- norm. distr.)
AV (appraiser variation) (99%- norm. distr.)
R&R (repeatability, reproducibility and interaction (I)
R&R (R&R)² = EV² + AV²+I²(99%- norm. distr.)
Part Variation PV (99%- norm. distr.)
Total Variation TV² = (R&R)² + PV²(99%- norm. distr.)

17. © STM Quality Limited
STM Quality
Limited
Determining and Assessing
Repeatability and Reproducibility
If repeatability is large compared to reproducibility, the reasons may
be:
The instrument needs maintenance;
The gauge should be redesigned to be more rigid;
The clamping or location for gauging needs to be improved;
There is excessive part variation.
If reproducibility is large compared to repeatability, then possible
causes could be:
The appraiser needs to be better trained in how to use and read the
gauge instrument;
Calibrations on the gauge dial are not clear;
A fixture of some sort may be needed to help the appraiser use the
gauge more consistently.