Machines that Can Feel

Sensitive Machine Components with Laser Technology

(PresseBox) ( Hannover, )
Scientists use a trick to make the slightest strain on parts of a tooling machine visible. They can measure stress on the fly, or recognize a dull cutting tool at an early stage. The Laser Zentrum Hannover e.V. (LZH) will show how this stress gauge works at this year's Hannover Messe, from April 8th to 12th.

How can information on the condition of a tooling machine or process forces and vibrations be monitored during the manufacturing process, and even more important, how can this information be used for process optimization? This information can be measured using sensor modules with gentelligent (genetic + intelligent) components, which help a machine "feel". This is the goal of a special research area "653" under the leadership of the Institute for Production Engineering and Machine Tools, University of Hannover, together with the LZH.

However, it is not simple to build such sensors. Tooling machines are usually very rigid, so that processing stresses cause only minimal deformation or distortion. In order to be able to measure these deformations precisely, the engineers used a "trick". They placed strain gauges in the bottom of grooves in the machine components, where stresses are highest, and where stress gauges can make the most precise measurements. However, up to now, it was not possible to place strain gauges in the bottom of grooves, as they are very difficult to access, and structures are usually complicated. Photolithographic sensors can only be used for flat surfaces, and strain gauges on foils, which are fixed to the machine using adhesives, are not suitable for the rough conditions in manufacturing processes.

The group "Laser-Micromachining" at the LZH used a laser structuring process to develop an innovative sensor for complex, three-dimensional tooling components. An isolating layer and a sensor layer are coated directly onto the tooling component, and the sensor is then structured using an ultrashort pulsed laser, with lateral resolutions from 10 to 100 µm. A laser scanner is used to ensure a fast structuring process. Since masks are not necessary, these high-quality thin-film sensors can be economically produced in small and medium-sized lots.

First prototypes of these laser structured sensors have already been integrated in the Z-axis slides of a tooling machine. Strain tests have shown that the sensors can measure even the smallest stresses, down to 0.001%.

Visitors to the LZH Stand at the Hannover Messe (Hall 17, Stand E 67) can test the function of these laser structured strain gauges themselves.

The work took place within the framework of the SFB project "Gentelligent Components in Life Cycle", and have been financed by the German Research Foundation (DFG) since July, 2005.
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