The project focused on advancing a high‑frequency eddy‑current inspection technique for three‑dimensional functional printing, specifically jet‑dispensing processes. A novel inline measurement and control system was created that couples newly designed eddy‑current sensors with laser profile scanners and infrared spot heaters. The sensors provide real‑time feedback on the quality of printed conductive structures on continuous traces and on complex 3D surfaces. By integrating this feedback into closed‑loop control, the system can adjust the jet‑dispensing parameters and the selective thermal post‑treatment during the same production run, thereby reducing defect rates and eliminating the need for separate oven steps. The result is a single‑machine solution capable of producing industrial‑grade functional elements with high yield.
Key technical achievements include the development of algorithms that compensate for disturbances such as variations in the contact angle between the jet dispenser and the substrate. Modeling work showed that a contact angle between 0° and 30° does not influence the print outcome, allowing the process model to be simplified and made more robust. The eddy‑current system was integrated into a robot‑based demonstrator that uses a UR10e arm equipped with jet‑dispensing and IR‑spot tools, while data acquisition is handled by an industrial PC with Beckhoff expansion cards. Control logic written in Structured Text is portable across PLC platforms, and a web‑based interface allows operators to configure and monitor the process. The demonstrator successfully characterized a range of conductive materials and demonstrated the ability to regulate printing, drying, and sintering steps in real time.
The project also produced a new generation of inline sensors and firmware that can be deployed in other manufacturing contexts such as smart textiles, automotive electronics, energy‑storage devices, and displays. By providing continuous, non‑destructive inspection, the technology enables rapid changeovers and recipe adjustments under tight cost constraints, thereby minimizing downtime.
Collaboration was carried out between SURAGUS GmbH, a Dresden‑based small‑medium enterprise specializing in high‑frequency eddy‑current sensors and test systems, and the Fraunhofer Institute for Machine Tools and Forming Technology (IWU). SURAGUS supplied the sensor hardware, firmware, and software development, while IWU contributed expertise in sensor integration, process control algorithm design, and robotic system implementation. The partnership leveraged the close geographic proximity of the two organizations, allowing frequent on‑site exchanges and rapid iteration of prototypes. The project ran during 2019, with deliverables reported in a final report issued in October 2019. Funding was provided through German research programmes, supporting the development of advanced inline inspection technologies for additive manufacturing.