Double-checking for cleanliness

Spotless surfaces are of prime importance in the plastics and metal processing industries, as dust and dirt can impair the function and adhesive properties of parts. A portable measuring device, the KombiSens, can detect both types of contamination.

Greasy fingerprints on wineglasses, ketchup on the table, crumbs on the floor – anyone with a clean disposition would be disgusted. But spotless surfaces are not the prerogative of housework maniacs; they are essential in numerous sectors of industry such as car manufacturing or metal processing, where dirt can have an adverse affect on gluing and painting processes or impair a component’s function.

When manufacturers are planning to coat a surface, they carry out regular spot checks to determine how clean their parts are. Many of these analysis methods fail to reveal defective cleaning until some time has elapsed – and meanwhile production has continued with the faulty workpieces. Researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart have developed an easy-to-use test device for checking cleanness during the production process. KombiSens detects both dust and grease on surfaces.

The portable device combines two measuring principles. In the highlighting process, the surface is illuminated at almost zero degree angle from the side. Any particles resting on it appear bright, and an image processing camera plus analysis software counts them from above and measures their size. The second process shortly afterwards illuminates the surface from above and detects the intensity of the reflected light. If the device is calibrated with a clean surface beforehand, the changed light intensity indicates the degree of contamination.

“The KombiSens detects particles and smears in the micron range on a surface measuring only 5 x 5 millimeters,” says group leader Kai Wegener, summing up the performance of his device. “It finds dust particles within seconds, and grease marks in just a few milliseconds, allowing any fundamental deficiencies in the cleaning method to be quickly identified.”

In order to characterize the nature of the grease or particles, however, the samples still have to undergo a microscopic or chemical examination. “The device is a useful addition to existing analysis methods because it provides quick results,” Wegener emphasizes. “On the other hand, the slower methods are more accurate.”

The KombiSens prototype is currently being validated by customers of Mafac, a cleaning company from Alpirsbach in the Black Forest. The Esslingen-based company Advanced Clean Production GmbH plans to start manufacturing the device later this year. Other interested parties can discover more at the stand presented by the Fraunhofer Alliance for Cleaning Technology in Hall B1 at the parts2clean trade fair, which takes place in Friedrichshafen, Germany, on October 26-28.