Driving understanding of Measurement Systems Performance

Companies within the Aerospace industry have long since recognised that although they compete to gain market share, they also share common challenges. In the past they have created differing techniques and methods to try and achieve the same results. To address this, a group of Aerospace engine manufacturers joined together to create the Aerospace Engine Supplier Quality (AESQ) group. The objective of the group was to discuss and identify opportunities to develop joint requirements for the Aerospace engine supply chain. One of the more tangible results of the group’s activities is the release of a number of industry recognised standards.AS13003 Measurement Systems Analysis requirements were released by the AESQ in Feb 2015 to document the common acceptance criteria to be used when evaluating the performance of measurement systems.Measurement System Analysis (MSA)Measurement Systems are so much more than the measuring instruments and gauges that are used for measurement. The measurement value that we see is a result of the measurement process being carried out by:

The Measuring instrument (Equipment)
The person using the measuring instrument (Appraiser)
The Environment in which the system operates
The Methods used for setup and measurement of the parts
The tooling and fixtures that locate and orientate the part being measurement
The software that performs calculations and outputs the result

The result that you obtain when making a measurement is influenced by each of the above. The extent to which each of the parameters affect the reading may vary from one situation to another. However, each one of these influences can be looked at as factors introducing variation into the process of measurement.Why MSAA measurement system tells you in numerical terms important information about the variation present when a measurement is made. How sure can you be about the data that the measurement system delivers? Is it the real value that you obtain out of the measurement process, or is it the measurement system error that you see?Measurement system errors can be costly, and can affect your capability to obtain the true value of what you measure. It is often said that you can be confident about your measurement of a parameter only to the extent that your measurement system can allow.For example, a process may have total tolerance of 30 microns. The measurement system that you use to measure this parameter, however, may have an inherent variation (error) of 10 microns. This means that you are left with only 20 microns of the parameter tolerance. The measurement system variation is eating into your parameter tolerance.How does MSA differ from calibration?

Calibration is a process used to compare the measuring instrument against standards of known value and uncertainty, and understand the difference between the standard and the actual instrument. Calibration is done under controlled conditions and by specially trained personnel.However on the shop floor, where these instruments are used, the measurement process is affected by many different factors such as method of measurement, appraiser’s influence, environment and the method of locating the part. All these can introduce variation in the measured value. It is important we asses measure and document all the factors affecting the measurement process, and try to minimize their effect.We need to consider the complete process used to obtain measurement – (Appraiser, Machine, Material, Method, and Environment).When should MSA be applied?

How will MSA benefit my organisation?MSA helps reduce both the type of risks associated with measurement of a parameter and making decisions based on the result of the measurement, the risk of False Alarm (a good part being judged to be bad) and the risk of a Miss (a bad part being judged as good) .Industry Forum are pleased to announce the availability of a number training courses in support of the techniques and methods suggested within the AS13003 standard.