March 2008 eNews

Laser scanning at Audi: recording reality’s digital fingerprint

The scene is a long hall. A laser scanner is making a discreet buzz, constantly rotating on its own axis. One minute later, the results are displayed on a computer monitor: an accurately detailed representation of the long hall, the labyrinth of pipes over various thicknesses on the wall, the production machines in the area, in Fish-Eye-Optic, grayscale, and in 3-D.

When completed, this “cloud” consists of 8 million points from the Laser Scanner LS 880 from FARO.

Audi in Györ, Hungary, which employs 5,000 people in the motor and TT model production, have been using the laser scanner since mid-2003.

Attila Perge, team coordinator, CAD-Team in the Factory Planning department, thinks highly of his decision to purchase it: “At the time this was the best device on the market. We chose this scanner, due to the 360°-image which is delivered. Also, the scan speed and the resolution were unbeatable.”

Spheres at reference points

The scanner is mounted on a trolley, offering a mobile measurement station — including notebook and power supply. To scan, the laser is positioned over a point marked on the floor of the workspace. Eight-mm thread bolts are positioned around the surrounding area, specific spheres coated white with a 14.5cm diameter are screwed onto the bolts. These special spheres are the reference points allowing the scans to be positioned relative to one another.

A minimum of three spheres is necessary to reference a scan. An external surveying firm measured the exact coordinates of the reference bolts. After 4.5 minutes and a rotation through 360° of the laser on its axis, the scan is complete and is automatically saved.

“Including the setup and stowing of the equipment, a scan takes approximately 15 minutes, which means that in one day up to 40 scans can be completed,” says Perge.

In a complete production hall, including all of the machines, up to 500 scans can be necessary.

From the point cloud to CAD data

The point cloud, produced through a scan, records the distance from the scanner for every measured point. In order to work with the data, it is first filtered and transformed. To achieve this, FARO offers the software tool FARO Scene, with which the data can be prepared to export into a CAD system. The reference spheres are manually recognized.

Linked to the hall survey data, the scan can then be correctly positioned within the hall. The area to be modeled is selected within the point cloud, and the data exported into the CAD system. In Audi’s case, this is a Bentley Microstation. On the basis of the points, objects can be realized in the CAD system. FARO Scene supports beside Microstation other systems such as AutoCAD, CATIA, I-Deas, PDS, IGrip, PDMs and RobCad.

Why are scans performed? Perge answers: “Naturally to create a basis documentation of the actual builds beforehand, then to scan during and following the modification.”

This allows the actual status of a project to be presented in the CAD system. Also wing designers may evaluate whether the proposed modifications can proceed or if additional changes are necessary. For example, during the construction of a new hall, the course of the pipe work must be altered. A scan can be performed and the designer can import the data of the modified area into Microstation to compare the new object data to the planned data and modify the planned data.

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