Uncertainties in dimensional measurements due to thermal expansion

J. E. Muelaner, D. Ross-Pinnock, G. Mullineux, P. S. Keogh

Research output: Chapter or section in a book/report/conference proceedingChapter in a published conference proceeding

Abstract

Thermal expansion is a source of uncertainty in dimensional measurements, which is often significant and in some cases dominant. Methods of evaluating and reducing this uncertainty are therefore of fundamental importance to product quality, safety and efficiency in many areas. Existing methods depend on the implicit assumption that thermal expansion is relatively uniform throughout the part and can therefore be corrected by scaling the measurement result. The uncertainty of this scale correction is then included in the uncertainty of the dimensional measurement. It is shown here that this assumption is not always valid due to thermal gradients resulting in significant shape changes. In some cases these are the dominant source of dimensional uncertainty. Methods are described to first determine whether shape change is significant. Where shape changes are negligible but thermal expansion remains significant then the established methods may be used. This paper describes the application of the Guide to the expression of Uncertainty in Measurement (GUM) uncertainty framework which provides an approximate solution for thermal expansion due to non-linearity and a non-Gaussian output function. The uncertainty associated with this approximation is rigorously evaluated by comparison with Monte Carlo Simulation over a wide range of parameter values. It is often necessary to estimate the expected uncertainty for a measurement which will be made in the future. It is shown that the current method for this is inadequate and an improved method is given.

Original languageEnglish
Title of host publicationLaser Metrology and Machine Performance XII - 12th International Conference and Exhibition on Laser Metrology, Machine Tool, CMM and Robotic Performance, LAMDAMAP 2017
PublisherEUSPEN
Pages133-143
Number of pages11
ISBN (Electronic)9780956679093
Publication statusPublished - Jan 2017
Event12th International Conference and Exhibition on Laser Metrology, Coordinate Measuring Machine and Machine Tool Performance, LAMDAMAP 2017 - Wotton-under-Edge, UK United Kingdom
Duration: 15 Mar 201716 Mar 2017

Conference

Conference12th International Conference and Exhibition on Laser Metrology, Coordinate Measuring Machine and Machine Tool Performance, LAMDAMAP 2017
Country/TerritoryUK United Kingdom
CityWotton-under-Edge
Period15/03/1716/03/17

ASJC Scopus subject areas

  • Engineering(all)
  • Atomic and Molecular Physics, and Optics

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