Development of Digital-Metrological Twins for emerging measurement technology in advanced manufacturing

Advanced manufacturing enables novel design and production techniques for industrial products with complex freeform geometries paired with an increasing demand for fast and contactless measurements in industrial quality control. Current simulation-based methods to determine the measurement uncertainty using Digital-Metrological Twins (D-MTs) do not yet cover these developments. In the light of digital transformation, this JRP will develop reliable model descriptions, suitable parametrisation methods and guidance for traceable measurements of complex freeform geometries and the use of versatile optical sensors in coordinate metrology supporting sustainable innovation in advanced industrial applications throughout Europe.

In a changing field of advanced manufacturing and with emerging demands for new technology, assembly concepts and paradigm shift in design, the need for adequate measurement technologies and methods to assess the quality of freeform geometries are of increasing importance. Trends in manufacturing industry include the use of cyber-physical production systems (CPPS) to address the change in customer demand and for technological advancements alike. Raised requirements to match tight tolerances play an increasingly important role. Therefore, the knowledge of measurement uncertainties is of utmost importance for the evaluation of production quality, cost savings and environmentally friendly production.

Recent developments in sensors and sensor systems in industrial quality control have enabled the substitution of classical tactile coordinate measuring machines (CMMs) by more versatile multi-sensor CMMs with different, interchangeable sensors. Similar developments can be observed for machine tools (MTs). Particularly optical sensors have gained popularity as they can be used to capture large areas of parts’ surfaces in a fast and cost-efficient manner and are suitable for measurements of delicate parts that cannot be probed tactilely. The rapidly growing number of machines which utilize contactless sensors demands models that cover the numerous error sources typical to these systems.

Furthermore, the required time efficiency in industrial metrology fosters the use of simulation-based uncertainty evaluation (e. g. Digital-Metrological Twins) as they are already available for a limited spectrum of measurement tasks. The quality of the results on the one hand strongly depends on the quality of the models available for the description of the measurement device, the measurement process, the specimen under test and their mutual interaction. On the other hand, the parametrisation of the used models is crucial for the traceability, and thus, reliability of the measurement results at industrial level.

The establishment of traceable parametrisation of the implemented D-MTs when using either tactile or/and optical measurements requires the selection of suitable calibrated measurement standards, and additional optical measurement instruments, as well as the definition of measurement procedures and appropriate strategies. The D-MT parameters are related to geometric errors (position and orientation errors as well as motion errors), thermal drifts, loads, dynamic errors, probing systems etc., with respect to the description given in the ISO 10360 series for CMMs and ISO 230-1 for MTs. The identification procedures and strategies of all those D-MT parameters will be carried out by optical/tactile probing of the selected physical measurement standards, regarding a number of optimised poses in the working range.

According to ISO 23247-1:2021, the digital twin could ideally be designed to mirror almost every aspect of a process. Nonetheless, in practice not all the parameters of the physical system are of the same interest, and therefore parameters with negligible influence in the process do not have to be replicated in the D-MT. Only the parameters that are relevant to influence the measurement uncertainty or the tolerances of manufactured parts in the case of multi-axis MTs should be considered. The reduction of the D-MT model implemented requires to quantify the effect of each considered error assessed during the parametrisation. This allows to identify the minimum number of model parameters for D-MT of the multi-axis MT, and to adjust the measurement procedure.

The conformance of the reduced D-MT will be tested by estimating the measurement uncertainty of tactile/optical CMMs when measuring a number of freeform artefacts manufactured with enhanced precision multi-axis MTs applying developed D-MT.

The specific objectives are the following:

1. selection of most appropriate measurement standards with prismatic and freeform geometries, as well as measurement instruments traceable to the SI metre definition that will be used for the identification of the D-MTs parameters related to the geometric errors with regards to well-defined measurement procedures and strategies. Additional parametrisation strategies will be also investigated for identifying parameters of the D-MTs related to thermal drift, dynamic errors, probing systems, etc.
2. development of adequate mathematical models for D-MTs of a selected machine tools (MTs) applicable for determination of the uncertainty of freeform measurements using both optical and tactile sensors. The underlying sources of errors need to be identified and considered in the mathematical model for the uncertainty evaluation using the D-MTs. The D-MT of MTs should include geometrical-kinematical model of the machine tool, thermal drift, etc., will be used for simulation-based uncertainty evaluation and will make use of the physical and virtual artefacts.
3. determine the parameters of the implemented D-MT for the multi-axis MT to guarantee the traceability to the SI metre definition, in particular for applications on prismatic/freeform geometries. The identification of all parameters of the D-MT model request the use of traceable physical standards with prismatic/freeform geometries and the deployment of additional integrated-sensing systems with respects to well defined measurement procedures and strategies. The reduction of the implemented D-MT model represents a fundamental step that will be carried out to build reduced traceable D-MT model with an optimised number of parameters.
4. testing and verifying the conformance of the reduced traceable D-MT model. As the tests are based on multiple measurements of probing points, the acceptance test has a statistical nature. Two designs of industrial freeform validation specimens will be proposed and manufactured by multi-axis high speed-milling machines, applying knowledge/feedback from the reduced traceable D-MT and selected prevention/compensation approaches. The manufactured industrial freeform validation specimens will be calibrated by traceable tactile CMMs. The reduced traceable D-MTs of MT-integrated optical sensors will be applied as to estimate the measurement uncertainties that will be compared to those obtained with tactile measurements.
5. define strategies and methods to evaluate the performance of the D-MT. The goal is to provide procedures to optimise their usability with respect to the needs and restrictions in advanced manufacturing applications. This particularly addresses the need for computationally efficient implementations as well as time- and cost-efficient methods to parametrise the models of the D-MTs.

References

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Lieu d’exercice : La thèse se déroulera essentiellement sur le campus Arts et Metiers ENSAM de Cluny (71) au LaBoMaP ainsi que quelques périodes courtes au LNE de Paris et LURPA de l’ENS Paris-Saclay. Le cadre du projet européen permettra des échanges scientifiques avec le consortium du projet ainsi que des déplacements en Europe sur la période de thèse.

La thèse proposée s’inscrit dans le cadre de l’EURAMET via le projet EMPIR 23IND12-ADAM « Application of Digital-Metrological Twins for emerging measurement technology in advanced manufacturing »

Machine tools

Geometrical errors

Metrology

Digital twin / virtual machine

Mechanical engineering