In addition to further developments in the field of data processing, powerful sensor systems for measurement data acquisition are also a factor of success for the fourth industrial revolution - Industry 4.0. The integration of commercial sensor systems within the most highly stressed zones of the components or tools is often particularly challenging. One alternative is offered by thin film sensor systems, which are applied directly to the surfaces of components or tools and can thus capture parameters such as strain and temperature distribution in direct contact with the work piece without necessitating changes to the design. Various application-specific sensor systems on components are being developed at Fraunhofer IST within the framework of several publically funded projects.
A multifunctional thin film sensor system on bending and deep drawing tools is being developed within the framework of the Cornet project “SensorFut“. Particularly challenging was the fabrication of a wear-resistant thin film sensor system on a tool surface with complex curvatures so that - as shown in the adjacent figure above - piezo-resistive sensor structures could be combined with thermo-resistive structures in the curved areas. This was achieved with a multifunctional film system which is illustrated schematically in the middle figure. It is based on the DiaForce® film, an amorphous hydrocarbon layer developed by Fraunhofer IST, which is very hard at 24 GPa and at the same time piezo-resistive. Complex structuring methods are used to produce sensor areas made up of chromium structures on the coated tool, which are then connected to the contacting pad via thin traces. At the same time, individual meander structures for temperature measurement are integrated into the film system between two electrical isolation layers.
The multifunctional thin film sensor system described above is also used within the Cornet project “SmartNFR“. The goal is to achieve more efficient fabrication of components made from natural fiber reinforced composites (NFR) through the use of wear-resistant thin film sensors in injection moulding machines. Not only do these innovative composite materials exhibit new functionality with regard to color, strength, and weight, they are also recyclable. They have a broad range of applications, from lightweight design to the automotive industry and common everyday products such as flooring. In the course of the project, the multifunctional thin film sensor system described above was applied to steel inserts in order to measure the temperature distribution and to determine the flow behaviour in the form during the injection molding process. Three of these wear-resistant sensor modules were integrated into an injection molding plant at the Tomas Bata University in Zlin, which is used to fabricate floor panels. The first successful test of the sensor system took place in direct contact with a polypropylene melt containing 30 percent wood fibers (see adjacent figure below).
The described results were achieved within the course of two Cornet projects.
In the “SensoFut“ (Sensorized Future – Sensing of temperature and pressure in harsh environments) project, Fraunhofer IST worked together with the Fraunhofer Institute for Machine Tools and Forming Technology IWU and the Belgian research association Sirris. The project, which ran from 01/01/2013 to 30/06/2015, was funded by the Federal Ministry for Economic Affairs and Energy (BMWi) and the German Federation of Industrial Research Associations (AiF) within the framework of the 13th Cornet Program (Collective Research Networking).
The project “Smart NFR“ (Smart coating systems for process control and increased wear resistance in processing of natural fibre reinforced polymers), which Fraunhofer IST is working on in partnership with the Fraunhofer Institute for Machine Tools and Forming Technology IWU and the Czech university Tomas Bata in Zlin, is funded in the 19th Cornet Call (Collective Research Networking) by the Federal Ministry for Economic Affairs and Energy (BMWi) and the German Federation of Industrial Research Associations (AiF) and runs from 01/06/2016 to 30/11/2018.