Produkt-Neuheit

Effective mechanisms for automated process control are of crucial importance for future manufacturing processes and require reliable monitoring of process variables. To this end, Fraunhofer IST, in collaboration with the Institute of Surface Technology (IOT) at the Technical University of Braunschweig, has developed tool-integrated sensor systems for in-process measurement of cutting forces and temperatures during the machining process.

Thin-film temperature sensors on indexable inserts
To measure temperatures in the contact area between the chip and the workpiece, a chromium sensor layer was used, sandwiched between two sputtered, electrically insulating aluminum oxide (Al₂O₃) layers.

Temperature-compensated cutting force measurement
To measure the cutting force, piezoresistive thin-film sensors were developed and positioned on a backing plate beneath the indexable insert. A new sensor design, consisting of a manganin-based force sensor and an underlying diamond-like carbon (DLC)-based temperature sensor, enables in-situ temperature compensation of the force sensor even under high and locally concentrated temperature gradients.

Real-Time Process Control
To demonstrate the potential of the new thin-film sensor, a real-time process control system for the cutting process was implemented. The goal was to maintain the cutting force within a defined target range while the cutting depth varied due to an artificially created step on the workpiece. This was achieved using a Python algorithm that utilized data from the thin-film sensor to adjust the feed rate during the process.

Outlook
The newly developed thin-film system for force measurements enables precise measurements in hard-to-reach and heavily loaded areas. The real-time process control demonstrates the competitiveness of the thin-film sensor compared to a force measurement platform that is more difficult to integrate and more expensive. Together with the temperature sensor presented here, it thus points to a promising path toward the digitalization and automation of production processes. Thanks to the possibility of integration close to the point of operation and the flexibly adaptable design, the sensor systems can also be used in a wide variety of other temperature-sensitive processes.

https://www.ist.fraunhofer.de/en/expertise/sensor-technology.html