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The assembly of the Iter reactor is underway. It is on the site of the international program that the components of the Tokamak from hundreds of factories on three continents are assembled. Iter Organization is responsible for the integration and assembly of the elements delivered to the site by the seven members of the program. However, the assembly of these elements is not just a simple interlocking set the components are complex and numerous, and the tolerances very tight, of the order of a millimeter.
An analysis from digital elements is necessary to ensure that the components can integrate perfectly. The essential prerequisite is the collection of data by metrologists. Their goal: to provide accurate data to reverse engineering specialists after measuring each part to verify its compliance. In these two phases, metrology and reverse engineering, PolyWorks software is used.
"I had already used Poly Works Inspector on a major project before coming to Iter. I wanted to continue using this software that allows us to acquire large point clouds directly in the software," says Lionel Poncet, an engineer in Iter's metrology group. "Other software on the market is limited in analyzing large numbers of points. We preferred PolyWorks Inspector, which meets the need for rapid analysis on data containing a large number of points," adds Hani Gagueche, CAD designer in charge of reverse engineering.
The installation of the cryostat base in the Tokamak assembly well was carried out in May 2020: it took it for Iter and its partners teams 10 years to design, build, deliver, assemble and weld the base of this cryostat. Some 6 meters high by 30 meters in diameter, 1,250 tons to move and position: the integration of the cryostat base required 3D measurements and reconstructions to adjust the whole.
"In the field of metrology, we use PolyWorks directly with our laser scanning equipment. Once the object is scanned, we have a point cloud and a polygonal model that is very precise and of very good quality thanks to the tools available at the very moment of acquisition," explains Lionel Poncet. "Once the data is received, thanks to the reports in our possession indicating critical assembly areas, we launch analyses that take into account the components as built and the components around which we know the dimensions to ensure that it works well together. For the base of the cryostat, we quickly realized that there were very critical areas, identified thanks to PolyWorks, and that a tool was needed to move this component to the millimeter for about thirty centimeters. Several tools were developed in-house, PolyWorks allowed us to choose the most suitable, "adds Hani Gagueche. And Lionel Poncet to specify that, in this case, PolyWorks made it possible to optimize the installation sequence, and this in less than 12 hours.
While the installation of the cryostat base was not easy, even more complex challenges await metrology and retro engineering specialists: the components to come are certainly smaller but the area is now congested and the tolerances even tighter. And the deadlines to carry out the operations are short!
Complex operations
"This summer, the installation of the first sector of the Tokamak vacuum chamber on its pre-assembly tool was delicate," confirms Hani Gagueche. Magnets, heat shield and vacuum chamber sector had to be assembled with a set of only 20 millimeters at the most critical places. In order to plan for sensor integration, we had to reposition these elements in relation to each other thanks to PolyWorks renderings."
"The prestressing rings were also completely scanned,"explains Lionel Poncet. A model has been created to be integrated into the CAD in anticipation of future assembly packages. Correction coils were also scanned using PolyWorks. On the model obtained, we must design wedges to fit the future interfaces. We also need to characterize and measure a number of pipes to verify that there will be no collision with future components that need to arrive. This also allows us to know the interface for future welding and cutting. »
Beyond internal teams, subcontracting companies also use PolyWorks when it comes to acquiring point clouds. "PolyWorks Inspector is a universal module dedicated to metrology that allows a multi-device connection. It is available in standard or premium mode, allowing to carry out dense point cloud post-processing with the possibility of obtaining, in real time, "quality" indications on data acquisition. Beyond the logical metro aspect, the software allows, for example, the obtaining of clearance maps, "argues Thibaut Hehlen, sales manager at PolyWorks Europa, a subsidiary of InnovMetric, the publisher of Poly Works. "Thanks to software like PolyWorks, we are able to do watchmaking with trucks," says Hani Gagueche. To make available certain 3D reconstructions made for critical cases, reverse engineering specialists use PolyWorks Modeler, a modeling & reverse engineering solution. "This module allows us to reconstruct surfaces from very precise meshes and provide a CAD file that is accessible to everyone, even when users do not have Poly Works or powerful computers. The many Catia users on the Iter program can thus have access to the files we have produced," explains Hani Gagueche.
The new automatic surface calculation algorithm from PolyWorks Modeler will soon be tested by the Iter teams. This algorithm could save a significant amount of time in terms of rebuilding time!
Featured photo: Positioning of the cryostat before lowering into the Tokamak well for final assembly.
