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Flexible and open-source tool for accurate reconstruction using industrial X-ray computed tomography

Periodic Reporting for period 1 - FlexCT (Flexible and open-source tool for accurate reconstruction using industrial X-ray computed tomography)

Reporting period: 2017-12-01 to 2019-11-30

The ability to perform accurate CT measurements is a critical requirement for non-destructive inspection of high precision components, for example in the aerospace, automotive, and medical industries. Furthermore, the acceptance of components made by advanced manufacturing techniques, e.g. AM and composite manufacturing, depends on the ability to control the quality of such components. Quality control demands robust measurement technology with known performance. The geometrical calibration procedure and compensation technique developed in this fellowship contributes to the robustness of CT, catalyzing its widespread acceptance for critical inspection tasks. The end users of the geometrical calibration and compensation techniques are users of CT instruments, whether CT research laboratories, CT calibration service providers, medical users of CT, or industrial users of CT (e.g. manufacturers). Entities that demand accurate measurements by CT benefit from the deliverables of this fellowship. In order to ensure that the impact of the research is broad, the researcher has made contact with standards development committees to pursue standardization of the developed geometrical calibration and compensation techniques.
The work carried out under the Marie Skłodowska Curie Actions Individual Fellowship (MSCA-IF) FlexCT project under grant agreement 752672, henceforth ‘the project’, advances the state-of-the-art in X-ray computed tomography (CT). The research performed in the project resulted in the development of dedicated procedures that can be easily implemented by users of CT to achieve high accuracy measurements by reducing the effects of instrument misalignments.
A method for the calibration of CT instrument misalignments was developed and applied to the measurement of simulated and experimental instrument geometries. The results are shown to be robust under diverse implementations and for various magnitudes of instrument misalignments. The implementation of the geometrical calibration procedure on simulated instrument geometries is described in more detail in [P3], while the implementation on an experimental instrument is described in [P4]. A graphical user interface has been created for implementing the geometrical calibration procedure in a user-friendly environment.

A software correction method was developed to compensate for the measured instrument misalignments. The compensation procedure consisted of adapting the tomographic reconstruction algorithm to the actual (measured) instrument geometry. Implementation of the software correction method on simulated instrument misalignments is described in [P5], while the implementation on an experimental instrument is described in [P6].

The procedures for geometrical calibration and software correction are made available to users of CT instruments by way of MATLAB scripts. Several dissemination activities were organized to communicate the results of the work, namely a short lecture to an external company and two conference seminars. The combination of the geometrical calibration and software correction methodologies were combined into a full CT measurement pipeline, which was described in [P2]. Other research related to the quality of dimensional measurements by CT was also performed under the scope of the project. The sensitivity of CT dimensional measurements to error motions of the sample rotation stage was investigated and the results were presented at a conference [P1]. The project has allowed the researcher has gain valuable experience in project management, in organizing seminars, and in establishing collaboration with external parties. Furthermore, the hosting of the researcher at Materialise NV has provided him with exposure to additive manufacturing, a field of research that is in high demand given its potential in the manufacturing industry. The researcher contributed to the establishment of formal collaboration between Materialise NV and Volume Graphics GmbH, a company dedicated to software for analysis of CT data. The collaboration was formalized in an official announcement at FormNext, a leading exhibition of additive manufacturing technology and capabilities. Furthermore, the researcher collaborated with experts at Materialise NV and at KU Leuven in the CT inspection of plastic and metal additively manufactured components [P7].

Publications from action:

[P1] Ferrucci M et al. 2018 Sensitivity of CT dimensional measurements to rotation stage errors 8th Conference on Industrial Computed Tomography (Wels, Austria)

[P2] Dewulf W, Ferrucci M, et al. 2018 Enhanced dimensional measurement by fast determination and compensation of geometrical misalignments of X-ray computed tomography instruments CIRP Annals 67 (1), 523-526

[P3] Ferrucci M et al. 2018 Measurement of the X-ray computed tomography instrument geometry by minimization of reprojection errors—Implementation on simulated data Precision Engineering 54, 7-20

[P4] Ferrucci M et al. 2018 Measurement of the X-ray computed tomography instrument geometry by minimization of reprojection errors—Implementation on experimental data Precision Engineering 54, 107-117

[P5] Ametova E, Ferrucci M, et al. 2018 Software-based compensation of instrument misalignments for X-ray computed tomography dimensional metrology Precision Engineering 54, 233-242

[P6] Ametova E, Ferrucci M, et al. 2018 Software-based compensation of CT instrument misalignments – experimental study 9th Conference on Industrial Computed Tomography (Padova, Italy)

[P7] Yang L, Mertens R, Ferrucci M, et al. 2019 Continuous graded Gyroid cellular structures fabricated by selective laser melting: Design, manufacturing and mechanical properties Materials & Design 162, 394-404
The research performed in this fellowship supports European industrial policy objectives concerning development of the manufacturing capacity in Europe. In particular, the research addresses the following objectives as outlined in the European Commission technical report entitled Factories of the future: Multiannual roadmap for the contractual PPP under Horizon 2020:

1. To raise the share of manufacturing in EU GDP from 16 % to 20 % by 2020;
2. To raise industrial investment in equipment from 6 % to 9 % by 2020; and
3. To invest in “R & I to integrate and demonstrate innovative technologies for advanced manufacturing systems” such as “high-tech manufacturing processes for both current and new materials or products, including 3D printing, nano- and microscale structuring.”