MSA

Measurement System Analysis is the most fundamental step for use of other methods like DOE, SPC, etc.

Some definitions:

Measurement - is the assignment of values to material things to represent the relations among them with respect to particular properties.

Gage = any device used to obtain measurements.

Measurement System - is then the collection of instruments , gages, standards, methods, fixtures, software, personnel, environment and assumptions used to quantify a unit of measure.

GRR or Gage R&R - the combined estimate of measurement system repeatability and reproducibility.

Analysis:

During analysis we calculate many items like linearity, bias, repetability, reproducibility, provide graphical analysis...The most common index number for measurement system capability is so called GRR.

When GRR > 30% of tolerance or process variability, the gage must not be used!!!