Subscribe options

Select your newsletters:

Please enter your email address:

@

Your email address will only be used for the purpose of sending you the ITER Organization publication(s) that you have requested. ITER Organization will not transfer your email address or other personal data to any other party or use it for commercial purposes.

If you change your mind, you can easily unsubscribe by clicking the unsubscribe option at the bottom of an email you've received from ITER Organization.

For more information, see our Privacy policy.

News & Media

Latest ITER Newsline

  • Top management | ITER Council appoints new Director-General

    Convening in an extraordinary session in Paris, the ITER Council has appointed Pietro Barabaschi as the next Director-General of the ITER Organization. Mr Barab [...]

    Read more

  • On site | Open Doors for ITER families

    In a first at ITER, the gates of the monumental worksite opened on Saturday 17 September for a family-only Open Doors Day event, reserved for the families of st [...]

    Read more

  • Manufacturing | Russia ships four gyrotron sets

    Twenty-four electromagnetic wave generators called gyrotrons are at the heart of electron cyclotron resonance heating—the system on ITER that will ini [...]

    Read more

  • Fusion world | Science to resume at Wendelstein 7-X

    Improved equipment on Wendelstein 7-X will permit the stellarator device to achieve new scientific heights in a campaign planned to begin this autumn. Science a [...]

    Read more

  • ITER International School | On operation scenarios and control

    The 11th ITER International School concluded successfully in San Diego, USA, on 29 July after five days of lectures and discussions on the development of tokama [...]

    Read more

Of Interest

See archived entries

Welded attachments

Follow the laser projections

How do you position 150,000 welded attachments on to a vacuum vessel the size of a house, each one needing to be accurately placed to less than a 4 mm target?

Laser templating is tested on a mockup of the ITER vacuum vessel at Walter Tosto in Chieti, Italy, by a team composed of ITER Organization and European Domestic Agency specialists. Not only will this innovative technique help assembly contractors place each of the vacuum vessel's 150,000 welded attachments precisely, but it will be key to producing unique identification numbers for quality control and inspection. (Click to view larger version...)
Laser templating is tested on a mockup of the ITER vacuum vessel at Walter Tosto in Chieti, Italy, by a team composed of ITER Organization and European Domestic Agency specialists. Not only will this innovative technique help assembly contractors place each of the vacuum vessel's 150,000 welded attachments precisely, but it will be key to producing unique identification numbers for quality control and inspection.
Traditional methods of marking and laying out—either by measuring from existing features, or using a template—do not work well on the ITER vacuum vessel; the complex curved shape and sheer quantity of attachments mean these old techniques are time-consuming and inherently inaccurate and error-prone.

After investigating several alternatives, a team composed of ITER and European Domestic Agency (Fusion for Energy) specialists evaluated laser templating as the most appropriate technology for use during construction—a technique that does not burn a marking on to the component, but instead projects a pattern onto it with a safe, low-power laser. The welder then simply positions the component according to the projection.

Although the use of the system is simple, the technology required to accurately project a component position onto a curved surface is complex.

First, we need to know the shape of the vacuum vessel. This is done by using a large-volume laser scanning system that is very accurately measures a mesh of points on the component—and the ITER vacuum vessel will have millions of scan points. These "point clouds" are then converted into a digital 3D model.

In a spare room in the basement of ITER Headquarters, Stéphanie Panayotis (ITER vacuum vessel engineer) and Guy Sandford (ITER construction engineer) refine the design of the laser projections to improve the ergonomics and accuracy of positioning a welding gun. (Click to view larger version...)
In a spare room in the basement of ITER Headquarters, Stéphanie Panayotis (ITER vacuum vessel engineer) and Guy Sandford (ITER construction engineer) refine the design of the laser projections to improve the ergonomics and accuracy of positioning a welding gun.
Second, the projector needs to know where the component is. For this, a technique called stereophotogrammetry is used, in which a pair of cameras look for circular markers stuck on the component. Through image processing, the circular markers are detected in each camera—and because the angle and position of the cameras are known, the position of the projector can be determined through triangulation. With the component and projector position known, the laser beam is then scanned over the correct angles to create a projection on the component in the correct location. If the welder or the tool blocks the projection, projector is moved to a better location and the system realigns itself automatically.

Laser templating has some massive advantages for quality too. Each projection will have a unique weld number projected at the same time, substantially reducing the chance that the welder will put the wrong component in the wrong place. And after installation, quality control can be improved by easily locating components for inspection.

After the attachments are welded to the vacuum vessel, laser templating will be useful for aligning the sensors and components attached to them. And for the 75 km of in-vessel cabling that must be posed, the benefits of using the laser templating system to indicate the complex routing of the cables are obvious.

As with all novel technologies, there are relatively few suppliers of laser templating systems. As operation of the equipment in a realistic environment was critical, the ITER/Fusion for Energy team evaluated two systems using a vacuum vessel mockup at Walter Tosto* (Chieti, Italy). Having performed quantitative metrology checks, and qualitative ease-of-use tests, the system provided by Extend 3D (Munchen, Germany) was determined to be best suited for ITER's use.

The system is currently being used for process development and qualification by the Dynamic consortium, which has been awarded the TAC2 machine assembly contract, in preparation for the arrival of the first vacuum vessel sector.

*Walter Tosto is part of the AMW consortium, which is supplying the five sectors of the ITER vacuum vessel under European procurement.


return to the latest published articles