13.06.2013 10:47 Age: 11 yrs
Category: Fachartikel

Full reliability in case of crash

Airbags are a matter of life and death. They must function one hundred percent - that also applies to the individual components, even if it is "only" a welded and repeatedly punched steel tube.


Full reliability in case of crash

 In the thumb-thick steel tube the pyrotechnic propulsion unit is located; its pressure must lead through four or more holes into the airbag and nowhere else, this must under no circumstances tear the tube. Weld Seams shall therefore not just be in the right position, but must be 100 percent tight. Consequently, the inspection of the position and cracks must also be 100 percent reliable. Such reliable tubes are produced by König Metall in Gaggenau, near Karlsruhe / Germany.


The owner-managed medium-sized company with 470 employees produces approximately half of each sheet metal and tube components mainly for the automotive industry, including exhaust pipes for combustion engines and combustor tubes for airbag systems, at least 10 million units per year in 14 variants, but König Metall also produces manufacturing equipment by itself, e.g. for the combustor tubes. CEO of the company is Hans-Jörg Leuze. He must ensure that only 100-percent tested products leave the factory on time and regularly.

Hans-Jörg Leuze describes an important aspect of its responsibility: "We are always working against deadlines" Longer downtimes cannot be afforded by König Metall. Not only the production equipment, but also the test equipment must be completely reliable in two ways:  It may not fail and must not make errors. If there are still problems, Hans-Jörg Leuze says: "I am the instance where all problems meet".

König Metall forms the combustor tubes from about sheet of about 1 mm thickness and welds them with high frequency. At one end of the holes are punched, they must not sit in the weld. In addition, the longitudinal seam must be free of cracks and other defects.

Three testing items are performed:

- Position of the weld seam before punching

- Position of the weld seam after punching

- cracks

For a long time König Metall has plagued with optical systems for position detection: A camera records the colours around the weld, and an evaluation unit calculates the position of the weld seam - actually a simple method that has only one flaw: it does not work.

König Metall realized that there were at least two to five percent false positive error messages; that means those discharged parts were actually fine. An expensive affair. Providers of camera based systems could not solve the problems and gave up one by one. Consequently, König Metall had to find a reliable method and a reliable supplier. A proven technology for Weld Seam Detection and Testing is the Eddy Current Technology - successfully utilized by Roland Electronic from Keltern / Germany with about a quarter century of experience in detection of weld seams. Nevertheless, Roland Electronic found out that colours of the seam are not reliable in  detection of the location of the weld seam.

Apparently some weld seams were stitching up to two millimetres in addition to the information provided by the Roland systems. Apparently means to locate the position by the colour of the weld seams. In Keltern this impression was not new: they had long time been under the impression that appearances were deceiving.

Samples of welded tubes were analysed in depth. Lo and behold, the Eddy Current Technology determined the correct weld seam position, optical control by eye and camera was wrong. The colours "slipped" up to 2 mm - for whatever reason. König Metall decided to decide for this reliable technology. Hans-Jörg Leuze comments: "The error rate of the position detection with eddy current is well below one percent."

Tuncay Özbek, Regional Sales Manager at Roland Electronic, is not surprised: "We have mastered the Eddy Current Technology for a long time. It is neither dirt nor influences caused by changing light conditions. Only strong electric and magnetic fields should be avoided." And further he explains: "The tube rotates in our system about its longitudinal axis, the probe rests over. We detect the beginning and end and calculate thereby the position."

 The product is therefore fine, but what about the supplier? How is the service from Roland Electronic? Hans-Jörg Leuze is simply thrilled: "Roland has adapted the system to our needs and integrated into the system, we were able to test it for several weeks and had initially only to buy the sensors that were specially adapted for us and the rest of the system we could return. We had to pay only when we had finished the test with a positive result. The test installation was crucial for us. "That was in 2008. And after the first plant many other were built.

 "Those who are interested can test their parts in our Application Laboratory for free," adds Tuncay Özbek. These tests provide in advance the certainty that tubes can be detected reliably and the process conditions can be met.

 And how about the After-Sales-Service? Hans-Jörg Leuze: "We had once a problem in the evening of December the 23th. On the morning of 24th, the Christmas Eve, the development manager himself came by to install new software. I think that says it all about the service." Between Keltern and Gaggenau are less than 100 km of distance; since it is no problem to be here. How does it look over long distances? Tuncay Özbek explains us:

"Although we have worldwide representatives, in tricky cases we prefer to send someone from our headquarter. The staff there is even better trained. Finally, we can reach most customers within 24 hours."

Hans-Jörg Leuze comes immediately with a statement: "Customers are for Roland machine builders that integrate the systems into their plants; end users are the users of those facilities. We build our own manufacturing equipment, so we are customer and end user in the same time." Roland Electronic and König Metall know each other, understand each other, and appreciate one another. Original statement from the CEO Leuze: "A good product - a model partnership."


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