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Msa 91

The document discusses how to perform a measurement system analysis (MSA) which involves evaluating a measurement system's capability, performance, and uncertainty. An MSA includes reviewing measurement data collection methods and tools, quantifying the measurement system's effectiveness by analyzing variation in data and determining its source. It also discusses evaluating measurement data for bias, stability, and linearity. The document outlines determining attribute vs variable data types, using master samples as standards, and how to perform a Gage R&R study including calculating repeatability, reproducibility, and variation percentages to evaluate a measurement system's accuracy.

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32 views1 page

Msa 91

The document discusses how to perform a measurement system analysis (MSA) which involves evaluating a measurement system's capability, performance, and uncertainty. An MSA includes reviewing measurement data collection methods and tools, quantifying the measurement system's effectiveness by analyzing variation in data and determining its source. It also discusses evaluating measurement data for bias, stability, and linearity. The document outlines determining attribute vs variable data types, using master samples as standards, and how to perform a Gage R&R study including calculating repeatability, reproducibility, and variation percentages to evaluate a measurement system's accuracy.

Uploaded by

kucenkomail
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as TXT, PDF, TXT or read online on Scribd
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How to Perform Measurement System Analysis (MSA)

MSA is a collection of experiments and analysis performed to evaluate a measurement


system’s capability, performance and amount of uncertainty regarding the values
measured. We should review the measurement data being collected, the methods and
tools used to collect and record the data. Our goal is to quantify the
effectiveness of the measurement system, analyze the variation in the data and
determine its likely source. We need to evaluate the quality of the data being
collected in regards to location and width variation. Data collected should be
evaluated for bias, stability and linearity.

During an MSA activity, the amount of measurement uncertainty must be evaluated for
each type of gage or measurement tool defined within the process Control Plans.
Each tool should have the correct level of discrimination and resolution to obtain
useful data. The process, the tools being used (gages, fixtures, instruments, etc.)
and the operators are evaluated for proper definition, accuracy, precision,
repeatability and reproducibility.

Data Classifications
Prior to analyzing the data and or the gages, tools or fixtures we must determine
the type of data being collected. The data could be attribute data or variable
data. Attribute data is classified into specific values where variable or
continuous data can have an infinite number of values. More detailed definitions
can be found below.

The Master Sample


To perform a study, you should first obtain a sample and establish the reference
value compared to a traceable standard. Some processes will already have “master
samples” established for the high and low end of the expected measurement
specification.

The Gage R&R Study


For gages or instruments used to collect variable continuous data, Gage
Repeatability and Reproducibility (Gage R & R) can be performed to evaluate the
level of uncertainty within a measurement system. To perform a Gage R & R, first
select the gage to be evaluated. Then perform the following steps:

Obtain at least 10 random samples of parts manufactured during a regular production


run
Choose three operators that regularly perform the particular inspection
Have each of the operators measure the sample parts and record the data
Repeat the measurement process three times with each operator using the same parts
Calculate the average (mean) readings and the range of the trial averages for each
of the operators
Calculate the difference of each operator’s averages, average range and the range
of measurements for each sample part used in the study
Calculate repeatability to determine the amount of equipment variation
Calculate reproducibility to determine the amount of variation introduced by the
operators
Calculate the variation in the parts and total variation percentages
The resulting Gage R & R percentage is used as a basis for accepting the gage.
Guidelines for making the determination are found below:

The measurement system is acceptable if the Gage R & R score falls below 10%
The measurement system may be determined acceptable depending upon the relative
importance of the application or other factors if the Gage R & R falls between 10%
to 20%
Any measurement system with Gage R & R greater than 30% requires action to improve
Any actions identified to improve the measurement system should be evaluated for
effectiveness

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