As we all know IATF 16949 requires us to carry out Measurement System Analysis to analyse the variation present in the results of each type of inspection, measurement and test equipment system identified in the control plan.

IATF clause:-

  • 7.1.5.1.1 Measurement system analysis.

The NOTE attached clarifies focus on:- Prioritization of MSA studies should focus on critical or special product or process characteristics.

IATF Annex B: Bibliography – supplemental automotive then gives us a number of different approaches such as AIAG MSA , ANFIA AQ024 MSA or VDA Volume 5 Capability of  Measuring Systems  

Measurement System Analysis (MSA)

Measurement Systems are so much more than the measuring instruments and Gages that are used for measuring. 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 fixture that locates and orientates the part being measurement
  • The software that performs calculations and outputs the result

The reading that you obtain is influenced by each one of the above. The extent to which each of the above 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 in the process of measurement.

Why MSA

A measurement system tells you in numerical terms important information about the part that you measure. 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 reading of a parameter only to the extent that your measurement system can allow.

For example, a process may have total tolerance to an extent of 30 microns. The measurement system that you use to measure this process, however, may have an inherent variation (error) of 10 microns. This means that you are left with only 20 microns as your process tolerance. The measurement system variation is eating into your process tolerance.

How does MSA differ from calibration?

Calibration is a process to compare the measuring instrument against standards of known value and uncertainty, and correct the difference if any. 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 assess, measure and document all the factors affecting the measurement process, and try to minimize their effect.

The complete process used to obtain measurement.

(Man, Machine, Material, Method, Environment).

Discrimination

The number of groups within the process data that the measurement system can discern is used as a quality check of the measurement system; if the number of categories is low, or the measurement samples are clustered compared to a relatively large tolerance zone the measurement system might be poor.

If the measurement system’s discrimination is inadequate, it may not be possible to accurately measure process variation or quantify measurements for individual parts.

The ability of the gauge to detect changes in the characteristic being measured and discriminate between measurement values is very important. The amount of change from the reference value that an instrument can detect and faithfully indicate helps us to understand if the discrimination is acceptable.

Discrimination looks at the measuring equipment and is typically considered to be the smallest graduation on the scale of the instrument.

When should MSA be applied

A measurement systems analysis study may also be required when:

  • There is a new manufacturing process
  • There is a new product to manufacture
  • There are customer concerns
  • There are internal quality issues
  • There is a change in process capability
  • There is a change in skill level

The study will aim to identify the elements of the total process variation which is due to the measurement system and the element which is due to actual part variation.

How will MSA benefit my organisation

MSA helps reduce both the type of risks associated with measurement of a process and making decisions, the risk of False Alarm and the risk of Missed Opportunities.

Industry Forum are able to offer  training and support related to MSA so if you are intrested and would like to find out more then please contact us at courses@industryforum.co.uk