1. A gauge R&R study involves measuring sample parts with different appraisers using the same gauge to determine measurement system variability. 2. Key steps include selecting appraisers, obtaining a representative sample of 10 parts, measuring the parts in random order over multiple trials while recording the results, and calculating various variations to determine if the measurement system is acceptable. 3. Acceptance criteria for gauge R&R is less than 10% for good systems and 10-30% for systems that may need evaluation depending on the application. The study quantifies repeatability, reproducibility and overall gauge R&R variation.

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BY – PPT4U
SUB - MSA

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MEASUREMENT SYSTEM

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Definition :-
To Analyze the effect of errors(factors) involved in
measurement.
 Measurement :- Measurement is a process by which
we can assign a numerical value to characteristics of a
product.
 System:- System is the collection of Operations,
procedures, Gauge and equipment's to assign a
number to the characteristics being measured.
 Analysis:- Analysis is a study of system that effect the
process.

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The factors of measurement system that could effect
the measurement system
Measurement
System
Man
MethodEnvironment
Instrument/Equipment
/GaugeItem of
Interest(Characteristics)

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1. Item of Interest :-Product which is being measured for a characteristics
(Mass, Volume, Temp, Length, Width etc.)
2.Man :- The person who will check/ verify the product called Appraiser
in this study.
3.Instruments :-The device by which we assign a numerical value for a
product characteristics.
4. Method :- The procedure by which we check the product
characteristics , Handling of Instrument, Specific place where Verification
will be Done.

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5. Environment :- The conditions in which we conduct the
measurement process may be :-
a) Temperature & Humidity level of environment where
measurement is being conduct.
b) Lightening
c) Vibrations

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The parameters of the measurement process
are
Input : Component to be
measured
Process factors : Equipment, Inspector
etc.
Output : Measured value

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Measurement System Errors

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Repeatability
Reproducibility

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REPEATABILITY
The variation in measurements obtained
With one measuring instrument
When used several times
By one appraiser
While measuring the identical characteristics
On the same part

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REPRODUCIBILITY
 The variation in the average of the measurements made
 By different appraisers
 Using the same measuring equipment.
 While measuring the identical characteristics
 On the same part

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All Instruments & equipments
becomes under this Study, Which
gives us a numerical value or
number to a product
characteristics
E.g – V. Caliper, micrometer, Dial
Indicators, Temp. Indicators. Etc.
Type of Measurement System Analysis
All Gauges & Visual
inspection becomes
under this study.
Which gives us only
decision for Good or
Not Good to product
characteristics .
For AttributesFor Variables

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GAGE REPEATIBILTY AND
REPRODUCIBILITY STUDY- (GAGE R & R
STUDY)

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Appraisers should be selected from those who normally
operate the instrument.
Sample parts must be selected from the process and they
should represent its entire operating range.
Instrument must have a discrimination (resolution) that
allows at least one-tenth of the expected process variation of
the characteristic.
The measurement method is well defined.
Measurements should be made in a random order.

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Conducting the R & R Study
Select ten parts from the process at random, preferably
one part from every days production.
Identify them with a serial number that cannot be
observed by the appraisers.
Select tow or three appraisers, who normally operate the
measuring system.
Measure the parts randomly so that all the appraisers
measure all the parts for two or three times (trial).
Record the observations

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1. Select two or three appraisers who use the measurement system.
2. Obtain a sample of 10 parts that represent actual or expected range of
process variation.
3. Number parts 1 through 10 so that numbers are not visible to appraisers.
4. Identify and Mark the place where measurement to be taken to eliminate
within part variation
5. Measure 10 parts in random order by appraiser A, with an observer
recording results.
6. Repeat step 5 with other appraisers conceal other appraisers readings.
7. Repeat step 5 and 6 using a different random order of measurement.
8. Calculate the average and ranges for all readings for each appraiser.
9 Using attached GR&R report, enter part averages and range averages.
10. Calculate repeatability - equipment variation.
11. Calculate reproducibility - appraiser variation.
12. Calculate GR&R and convert to percentage.
13. Calculate part variation and convert to percentage.
14. Calculate total variation.
Gauge R&R Study Steps:

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 Calculate the variations due to different factors,
according to the formulae given.
 A measurement system with R & R % of 10% or less is
considered good.
 A measurement system with R & R % between 10% to
30% may have to be evaluated for acceptance,
considering the criticality of the part.

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FORMULAE
• Xa bar, Xb bar, Xc bar = Average of all the measurements
made by A, B&C respectively
• Ra bar, Rb bar, Rc bar = Average of the range of the trails
made on 10 parts by A, B & C respectively
• Rp = Maximum part average – Minimum part average
• R- bar = (Ra bar + Rb bar + Rc bar ) / No. of Operators
• X-bar Diff = Max X-bar – Min X-bar
• UC LR = R-bar * D4 D4 = 3.27 for 2 trails
= 2.58 for 3 trails
• LC LR = R-bar * D3 D3 = 0 for 2 & 3 trails

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 Homogenize the data for Range
 Calculate R-bar, X-bar Diff and Rp only after
homogenizing
 Equipment Variation (EV) = R-bar * K1
(K1 = 4.56 for 2 trails
= 3.05 for 3 trails)
 Appraiser Variation (AV)
= SQRT { (X-bar Diff * K2 )2
– [ EV2
/ (nr)]}
(K2 = 3.65 for 2 operators
= 2.70 for 3 operators)

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(n : No. of parts
r : No. of trails)
 Repeatability & Reproducibility ( R &R)
= SQRT { (EV2
+ A V2
) }
 Part Variation (PV) = Rp * K3
n K3 n K3 n K3
2
3
4
3.65
2.70
2.30
5
6
7
2.08
1.93
1.82
8
9
10
1.74
1.67
1.62

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Total Variation (TV) = SQRT { (R&R2
+ PV2
) }
%EV = (EV/TV)* 100
%AV = (AV/TV) * 100
%R&R = (R&R/TV) * 100
%PV = (PV/TV) * 100

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11.0 Attribute Gage Study (Alternate) Method
a. Method of conducting Study
1. Obtain 50 components which are 50% OK, 25% marginally ok and 25% marginally
not OK.
2. Identify the components with numbers and note master readings in the Attribute
Study data sheet.
3. Select the appraisers for giving the decision (A,B & C)
4. Using the appraiser ‘A’, carryout the trial ‘A1’ and carryout the same with appraiser
‘B’ & ‘C’ for the trials ‘B1’ & ‘C1’
5. Repeat the step 4 for the trials A2,A3,B2,B3,C2&C3 for the appraiser’s A,B &

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