Autonomous Fixture Plates Integrate Advanced Measuring Room

The measuring area of the VW Crafter production plant in Września Poland is a model for future-oriented technology, equipped with optical and tactile measuring systems as well as the autonomous transportation fixture plates, which transport all sheet metal body parts and their measuring fixtures, including complete roadworthy vehicles, to the measuring cells without any mechanical guidance system.

The VW Crafter is available in a wide range of variants. From groundbreaking in 2014, only 23 months went by until the plant in Września was able to celebrate the start of production. Werner Steinert, who has been in VW service for 25 years, took over the management of QS analysis and measurement systems at the Września plant. “The opportunity to plan your measuring room according to the most modern criteria only comes once in a lifetime,” explained the measuring technician. During his career Steinert was active in many different plants; he supported toolmakers and production staff in the derivation and interpretation of measurement results, was involved in establishing cubing centers in German and European VW plants, and provided valuable start-up support with regard to measuring technology in distant countries such as Indonesia, Brazil, Argentina and Russia.

Volkswagen wanted to use this extensive experience in the Group’s latest production facilities, which is why Werner Steinert was entrusted with the task of building a central measuring room according to modern standards for car body construction. Individual components and assemblies, whether from suppliers or manufactured internally, up to complete vehicles were to be tested there to ensure a final product of the highest quality.

Werner Steinert reported: “In principle, I was able to implement what is being discussed at a broad level in the VW Group. In this respect, ideas from my colleagues from more than 80 vehicle-building plants have also been incorporated.” Thus, the new measuring room is a central unit with two areas, component qualification on one hand and conformity testing on the other. “The working environment is ideal, and my team consists of qualified young people who are very efficient,” praised the head of measurement technology. “We have the best prerequisites for achieving an outstanding level of metrology.”

The layout of the measuring room is characterized by six large measuring stations, three of which are equipped with optical measuring technology and robot automation. They are supplied with parts to be measured by a total of nine transport measuring plates, which glide through the hall without the need of a driver or a rail system. Werner Steiner proudly points out that in Września the highest concentration of optical measurement technology is available throughout the VW Group. He adds, “I am also not aware of any other manufacturers that have already implemented optical measurement technology to this extent and similar to this. We are able to digitize a complete VW Crafter car body completely within two hours.

High flexibility required
Due to the great diversity of parts, the measuring stations have to be equipped very flexibly. That is why Werner Steinert paid particular attention to the transport system: “From the very beginning, I visualized transport plates, which were mounted with measuring fixtures and parts by my staff and then sent to the appropriate measuring station. They should be able to go their own way, without having to rely on rails. “

A system fulfilling these demands was not even available on the market at that time. Werner Steinert contacted a tried and tested partner, Witte Barskamp KG, who had already supplied several VW plants with fixturing technology and grid plates for measuring and transporting. “From past experience, I was sure that Witte would be able to manage this project in the short space of time until the start of production,” Steinert was convinced.

On the basis of their patented aluminum sandwich plates, the specialists in clamping technology developed a concept that met Volkswagen’s approval. Managing Director Andreas Witte explains: “Our sandwich plates offer the highest precision and rigidity with a comparatively low weight and a height which is still regarded as a normal step height. Plates can be designed according to size and load as required and equipped with necessary additional elements.”

Witte developed an individually designed horizontal aluminum sandwich plate with air-bearing steering roller units and electric friction wheel drive for the VW Crafter measuring room. The special design and dimensions of the plate ensures a complete structure, which withstands loads of up to 2500 kg, torsion-resistant even when lifting and lowering in the measuring area.

Eight plates in size 400 x 2400 x 8000 mm and a ninth with a length of 4500 mm were developed, manufactured and delivered to Września according to the current VW specification. Their high-precision 100-grid layout enables positioning of fixtures for all body parts to be measured.

The decisive innovation is inside the aluminum sandwich plate system where Witte designers were able to integrate all components of the electronic control and drive and safety technology, two compressors with low-maintenance compressed air storage for lifting and lowering the plate and 48V batteries which power the friction wheel drive and all other electrical components. The rechargeable batteries are charged primarily via ground stations in the measuring cells.

Right and left duplex drives enable controlled longitudinal travel forwards and backwards, as well as cornering and turning around the drive axis. “The latter is enormously space-saving,” says Werner Steinert. “Space sometimes gets quite tight, especially when several plates are travelling at the same time.  The biggest challenge was finding an alternative to a rail guiding system like Steinert requested, which after intensive consultation resulted in a transponder based system. For this purpose, all routes between set-up and measuring stations had to be marked with memory chips. These approximately 2€ sized chips were set into the floor and covered with paint so that they are not visible. An antenna is located in the sandwich plates at the front and rear, which registers information from the nearest transponder chips. In addition, an integrated gyro compass ensures correct orientation. Thus, the plate equipped with a Siemens control system always knows where it is and can drive autonomously to its destination.
Partial automation provides great flexibility
However, the driving operation is only partially automated. No movement takes place without previous selection for the appropriate measuring area or set-up position via the control terminal at the face end of the plate by the measuring technician responsible, who then gives the command to go by pressing a button. CEO for measuring technology Steinert explains: “As long as the drive commands remain the responsibility of my employees, we are much more flexible. We can quickly rearrange processes and reconfigure the plates if necessary.”
Safety precautions, which comply with legal requirements as well as with VW guidelines are also integrated. Thus, a self-releasing safety laser scanner is located at each corner of the sandwich plate, which automatically monitors the surrounding horizontal protect and move areas near the ground. If the scanner detects a possible obstacle, the plate reduces speed to a standstill. If the area becomes free again, it will automatically continue. For Werner Steinert this is an ideal solution. “Despite the automatic drives, my employees move around quite relaxed in the hall because they know that the system works.”

The measuring room was finished in time for the start of production. In conversation with Werner Steinert, his enthusiasm for the result is perceivable: “The overall system with the optical measuring technology is forward-looking. It is an important building block in the progressive digitization of our production world. The fact that everything will not be fully automated in the future is demonstrated by our partially automated transport system. The fact that our employees are responsible for loading the measuring area allows us to operate in a highly flexible manner, and our expensive measuring machines provide continuous results without major failure or waiting times. “

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