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German Researchers Make Metal Objects With RFID Inside

Fraunhofer's engineers demonstrate how to use selective laser sintering to integrate a standard passive tag within metal items as they are manufactured.
By Andrew Curry
Dec 04, 2009The places where RFID tags can be placed are almost limitless. One exception has been the challenge of integrating an RFID inlay within an object composed of metal. That's because the high temperatures required to melt and shape metal can destroy the components making up an RFID tag.

However, researchers at the Fraunhofer-Institute for Manufacturing and Advanced Materials (IFAM), in Bremen, Germany, indicate they've come up with a solution enabling them to embed a standard RFID tag within a metal object as that item is being manufactured. The technique makes use of a 20-year-old process called selective laser sintering, and IFAM engineer Claus Aumund-Kopp says his team has successfully built metal parts that include an RFID tag inside. The researchers presented their work at EuroMold 2009, a trade fair focused on mold making and tooling, held this week in Frankfurt.

Fraunhofer's researchers used selective laser sintering (SLS) to produce these metallic objects, shown next to a sample of the RFID tag integrated within each item.
Working with metal powder and a laser, it is possible to produce parts straight from a 3-D model generated with a computer-aided design (CAD) application. The process is painstaking: Powder is laid down in layers 20 microns (0.0008 inch) in thickness—approximately a quarter the width of a human hair—and a laser melts it in the shape of the desired part. Layer by thin layer, the metallic object emerges from the powder. "The chip is inserted into the part when we have reached a certain height," Aumund-Kopp explains.

Traditionally, RFID tags have been unusable in parts heated above 100 degrees Celsius (212 degrees Fahrenheit), though some tag manufactures have developed versions able to withstand temperatures as high as 1,093 degrees Celsius (2,000 degrees Fahrenheit) by encasing the RFID inlays in protective materials (see William Frick & Co.'s Gen 2 UHF Tags Take the Heat for Manufacturing Apps). In metal casting or laser fusion, however, temperatures can exceed 1,400 degrees Celsius (2,552 degrees Fahrenheit).

With Fraunhofer's process, Aumund-Kopp says, only a tiny bit of the material is ever heated, because of the gradual, partial nature of the process. That allows his team to use standard RFID tags that would be destroyed in traditional metal casting. "They're standard chips, with a standard glass cover," Aumund-Kopp says. "The trick is, the laser doesn't directly hit the chip, or hits it for such a minimal time that the chip isn't destroyed in the process."

Even more important, Aumund-Kopp adds, the Fraunhofer team discovered that the chips can be completely embedded within a metal part and still function. "We have found chips which are completely covered and are still readable," he states. "This is really new—usually, you need a gap where the electromagnetic fields can couple." The findings came as a pleasant surprise to the researchers, he says, and have created a puzzle for the future. "We can't explain it ourselves. We need to do some more tests."

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