1. 1 2 3 INDIAN INSTITUTE OF TECHNOLOGY ROORKEE PROJECT REPORT 2016
MSA 1
SANJAY KUMAR DEO
INDIAN INSTITUTE OF TECHNOLOGY ROORKEE 2
PROJECT REPORT 2016
MEASUREMENT SYSTEM ANALYSIS 3
PROJECT GUIDEs
Mr. R a m d u r a i
Mr. G u n j e s h K u m a r
Mr. S a r f r a z A h m e d

2. OBJECTIVE OF THE PROJECT AND PROJECT STUDY/COURSE
OBJECTIVE AND STUDY:
1. Determine which measurement system
will be studied ACCORDING TO MSA PLAN AND THE STUDY OF GAGE R & r.
2. Establish test procedure IN DIFFERENT DEPARTMENTS FOR GAGE R & r.
3. Establish the number of sample parts, the number of repeated readings, and the number of operators that will be used.
4. Choose operators and sample parts.

3. Measurement as a Process
As in any process, regardless of the nature of data collected or generated, measurement systems must demonstrate
Stability through time, or control
Minimal variation as a proportion of specifications, or capability
Minimal variation as a proportion of process variation
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4. Measurement as a Process
MEASUREMENT PROCESS
Equipment
Standard
Procedure
Operator
Measurement
Ambient
Environmental Characteristics
Product or Process to be Measured
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5. Definition of Terms
A Measurement System Analysis (MSA) is a specially designed experiment that seeks to identify the components of variation in the measurement.
Reference Value
The theoretically or agreed upon correct value of the characteristic being measured, traceable to some standard
Resolution
The smallest increment, or unit of measure, available from a measurement process
Generally at least 1/10th of the specification range
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6. Definition of Terms Precision Accuracy (Bias)
The degree of agreement (or variability) between individual measurements or test results from measuring the same specimen(s)
Accuracy (Bias)
The difference between the average of the measurement error distribution and the reference value of the specimen measured
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7. Precision vs. Accuracy Precision Accuracy
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8. Measurement Error Distribution of repeated measures on a single
specimen or part
Precision
- Repeatability
- Reproducibility
Accuracy
(Bias)
Reference Value
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9. Possible Sources of Process Variation
Stability
Linearity
Long-term
Process Variation
Short-term
Variation
w/i sample
Actual Process Variation
Repeatability
Calibration
Variation due
to gage
to operators
Measurement Variation
Observed Process Variation
We will look at “repeatability” and “reproducibility” as primary contributors to measurement error

10. Measurement System Terminology Discrimination - Smallest detectable increment between two measured values. Accuracy related terms True value - Theoretically correct value. Bias - Difference between the average value of all measurements of a sample and the true value for that sample. Precision related terms Repeatability - Variability inherent in the measurement system under constant conditions Reproducibility - Variability among measurements made under different conditions (e.g. different operators, measuring devices, etc.) Stability - distribution of measurements that remains constant and predictable over time for both the mean and standard deviation. Linearity - A measure of any change in accuracy or precision over the range of instrument capability.

11. Possible Causes of Bias
MSA for Attribute or Categorical Data
Bias
True
Value or
Standard
Bias
Observed
Average
Possible Causes of Bias
Sensor not properly calibrated
Improper use of sensor
Unclear procedures
Human limitations
Bias is the difference between the observed average of measurements and the true average. Validating accuracy is the process of quantifying the amount of bias in the measurement process. Experience has shown that bias and linearity are typically not major sources of measurement error for continuous data, but they can be.
In service and transaction applications, evaluating bias most often involves testing the judgment of people carrying out the measurements.
Example
A team wants to establish the accuracy of its process to measure defects in invoices. First, they gather a “standard” group of invoices and have an “expert” panel establish the type and number of defects in the group. Next, they have the standard group of invoices measured by the “normal” measurement process. Differences between averages the measurement process came up with, and what the known defect level was from the expert panel represented the bias of the measurement process.
Bias
MSA for Continuous Processes 11 .PPT

12. Possible Causes of Poor Repeatability
MSA for Attribute or Categorical Data
Repeatability
Repeatability
Possible Causes of Poor Repeatability
Equipment
Gage instrument needs maintenance
The gage needs to be more rigid
People
Environmental conditions (lighting, noise)
Physical conditions (eyesight)
Repeatability is the variation in measurements obtained when one operator uses the same measurement process for measuring the identical characteristics of the same parts or items.
Repeatability is determined by taking one person, or one measurement device, and measuring the same units or items repeatedly. Differences between the repeated measurements represent the ability of the person or measurement device to be consistent.
Possible causes of the lack of repeatability are listed on the slide.
Repeatability
MSA for Continuous Processes 12 .PPT

13. Possible Causes of Poor Reproducibility
MSA for Attribute or Categorical Data
Reproducibility
Reproducibility
Mean of
the measurements
of Operator B
of Operator A
Possible Causes of Poor Reproducibility
Measurement procedure is not clear
Operator is not properly trained in using and reading gage
Operational Definitions not established
Reproducibility is very similar to repeatability. The only difference is that instead of looking at the consistency of one person, you are looking at the consistency between people.
Reproducibility is the variation in the average of measurements made by different operators using the same measurement process when measuring identical characteristics of the same parts or items.
Possible causes of poor reproducibility include: measurement process is not clear, operator not properly trained in using the measurement system, and operational definitions are not clear nor well established.
Reproducibility
MSA for Continuous Processes 13 .PPT

14. Measurement Capability Index - P/T
Precision to Tolerance Ratio
Addresses what percent of the tolerance is taken up by measurement error
Includes both repeatability and reproducibility
Operator x Unit x Trial experiment
Best case: 10% Acceptable: 30%
Measurement Capability Index - P/T
Usually expressed as percent
Note: 5.15 standard deviations accounts for 99% of Measurement System (MS) variation. The use of 5.15 is an industry standard.

15. Measurement Capability Index - % GR&R
Addresses what percent of the Observed Process Variation is taken up by measurement error
%R&R is the best estimate of the effect of measurement systems on the validity of process improvement studies (DOE)
Includes both repeatability and reproducibility
As a target, look for %R&R < 30%
Measurement Capability Index - % GR&R
Usually expressed as percent

16. MEASUREMENT SYSTEM ACCEPTANCE CRITERIA

17. Measurement Systems Capability
LSL
USL
5.15E
(USL - LSL)
Measurement
Error Distribution
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