Laser processed thin films to detect machine tool stress

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Laser micromachining can deliver higher levels of stress measurement accuracy in machine tools, researchers have found.

Using an ultrashort pulsed laser, with lateral resolutions from 10 to 100µm, an isolating layer and its sensor layer, which are coated directly onto a tooling component, are structured. A mask is not necessary and the laser allows for rapid structuring to create the thin-film sensor.  

These laser structured thin-film sensors can act as strain gauges and because they are small can be placed in the bottom of grooves in machine tools. These grooves are where machine tool stresses are highest, and where stress gauges can make the most precise measurements. The first prototypes of these laser structured sensors have been added to 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 per cent.

Stresses during machine tool operations can be caused by an incorrect machining process for the workpiece, a worn tool that needs replacing or by structural problems with the machine tool itself. 

The work on these thin-film strain gauges has been carried out by the Institute for Production Engineering and Machine Tools at the University of Hannover and Lazer Zentrum Hannover. The research has been funded by the German Research Foundation since 2005.