Measurement System Analysis (MSA)

Every process has variations, and measurement is a process. Variations can be systematic or random. In Six Sigma , Measurement System Analysis (MSA) is used to evaluate measurement results.

Objective
  • Assessment of measurement uncertainty
  • Validation of measurement data
  • Meet standards requirements
  • Meet delivery agreements
  • Make better decisions
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Procedure:

Purpose of the measurement system

▪ Should the measurement system be used for process monitoring?
▪ Should the measurement system be used for quality assurance?
▪ Which parts should be evaluated with it?
▪ What are the tolerances?

Select the method

MSA Type 1 – Determination of bias (accuracy) and repeatability (precision)
MSA Type 2 – Determination of repeatability and reproducibility
MSA Type 3 – Similar to MSA-Type 2 but without operator influence

Obtain reference parts (if needed)

Sometimes traceability is required by standards or supply agreements. Obtain reference parts to evaluate the accuracy of measurements.

Evaluate the capability of the measuring instrument

Calculate the following metrics:
▪Cg
▪Cgk
▪%P/T
▪%GRR

The term MSA comes from AIAG (Automotive Industry Action Group). The MSA guidelines describe various methods to assess different aspects of measurement system capability:

▪ MSA Type 1 – Determination of bias (accuracy) and repeatability (precision)
▪ MSA Type 2 – Determination of repeatability and reproducibility
▪ MSA Type 3 – Similar to Type 2 but without operator influence (automated measurement systems)
▪ MSA Type 4 – Determination of the measurement system’s linearity
▪ MSA Type 5 – Determination of the measurement system’s stability
▪ MSA Type 6 – For gauge testing
▪ MSA Type 7 – Related to ISO 22514-7 (Bowker Test)

Terms and Definitions:
▪ Bias (Offset): Bias is the systematic measurement error by which the average value deviates. It is a measure of the measurement system’s accuracy.
▪ Repeatability: Repeatability is determined by repeatedly measuring the same part by the same operator using the same measurement instrument.
▪ Reproducibility: Different operators measure the same part. The standard deviation of the measurements obtained by different operators is the measure.
▪ Linearity: Linearity of a measurement system refers to the accuracy and precision of the system across the entire measurement range.
▪ Stability: Stability is a measure of the accuracy and precision of a measurement system over time. (Measurement systems need to be recalibrated periodically.)
▪ Resolution: Resolution is the smallest difference that a measurement system can reliably distinguish.

Messsystemanalyse MSA Lean Six Sigma

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