Identification of Key Temperature Measurement Technologies for the Enhancement of Product and Equipment Integrity in the Light Controlled Factory

Abstract

Thermal effects in uncontrolled factory environments are often the largest source of uncertainty in large volume dimensional metrology. As the standard temperature for metrology of 20˚C cannot be achieved practically or economically in many manufacturing facilities, the characterisation and modelling of temperature offers a solution for improving the uncertainty of dimensional measurement and quantifying thermal variability in large assemblies.Technologies that currently exist for temperature measurement in the range of 0-50˚C have been presented alongside discussion of these temperature measurement technologies' usefulness for monitoring temperatures in a manufacturing context. Particular aspects of production where the technology could play a role are highlighted as well as practical considerations for deployment.Contact sensors such as platinum resistance thermometers can produce accuracy closest to the desired accuracy given the most challenging measurement conditions calculated to be ~0.02˚C. Non-contact solutions would be most practical in the light controlled factory (LCF) and semi-invasive appear least useful but all technologies can play some role during the initial development of thermal variability models. Main textIn large volume metrology, thermal effects make a significant contribution to the uncertainty of measurements. Large structures that are often 20 m in length or greater are currently being assembled in factory environments where there can be thermal gradients of around 3-5˚C from floor to ceiling at any given time. Over a 24 hour cycle, the variation in ambient temperature can be as much as 15˚C.Whilst dimensional measurements in industry are sometimes taken alongside ambient temperature measurements which are used for linear scaling within the metrology software, this is often a sole measurement at one point in space, at one instance.One potential solution to the problem of thermally induced uncertainty is to model the thermal characteristics of the measurand. This can be achieved by monitoring the temperature and using this data to update a computational model that can more accurately predict the thermal and gravitational effects of the environment. The computational model makes use of the nominal CAD geometry of the measurand, alongside finite element analysis and tolerancing software.

Traceability of On-Machine Tool Measurement: A Review

“…In addition, repeatability can also be a big challenge for a traceable on-MT measurement, where non-controlled shop floor environment becomes a major uncertainty source. Researchers have recognized that environmental temperature has a significant impact on the thermal error of the machine tool and, therefore, on any metrology activity performed on it [ 14 , 15 , 16 , 17 , 18 , 19 ]. Hence, time- and space-dependent thermal effects become the dominant uncertainty source for the measurement of large scaledevices [ 8 , 20 ].…”

“…The uncertainty increases proportionally with temperature differences and component size. Therefore, for large components measured in a thermally unstable production environment, thermal effects can represent a high percentage of the total measurement uncertainty [ 8 , 14 , 16 , 114 , 184 , 185 ].…”

Review of industrial temperature measurement technologies and research priorities for the thermal characterisation of the factories of the future

“…This particular review extends and further details key temperature measurement technologies that have been identified for use in the Light Controlled Factory [1]. These are mature technologies that are suitable for measurement in the 0 -50˚C.…”

“…[1] compares the temperature sensing capability of each of the temperature measurement technologies reviewed in terms of their characteristics. Specifications of particular temperature measurement technologies will vary to some extent so this table provides more of a general guide to their relative merits.…”

Traceability on Machine Tool Metrology: A Review

“…The influence increases proportionally with temperature differences and component size. Therefore, particularly for large components tested in a thermally unstable production environment, thermal effects can represent a high percentage of the total measurement uncertainty [8,12,13,[190][191][192].…”