Researchers 3D Print Customized Sensors with Integrated Electronics

Demonstration model of customized sensor at different production stages: CAD concept (top left), after integration of the electronic components (top right) and as a finished demonstration model (bottom).

Researchers at the Center for Additive Production at the Fraunhofer Institute for Manufacturing Engineering and Automation (IFAM) have successfully 3D printed customized sensors for the first time. The team was supported by colleagues from the plastics processing machine manufacturer Arburg GmbH & Co. KG and the sensor and automation company Balluff GmbH.

The “Electronic Function Integration in Additively Manufactured Components” research project ran for 18 months, led by Stefan Pfeffer. The research involved printing the sensor casing in plastic so that it could be manufactured in any shape. A plastic with high dielectric strength and flame-retardant properties was required for the sensor casing. The team opted for semi-crystalline plastic polybutylene terephthalate (PBT), which is used as standard injection molding material for the production of electronic casings. However, this type of material had not yet been used for 3D printing.

The plastic was fed in granulate form into Arburg‘s “freeformer” industrial additive manufacturing (AM) system, which uses a material preparation unit with a special plasticizing screw. After melting the standard granulate, the freeforming process (which uses no molds) followed. A high-frequency nozzle closure discharged tiny plastic droplets, which could be precisely positioned with the aid of a movable part carrier.

This enabled the freeformer to create three-dimensional components with cavities layer by layer, into which components could be inserted during the printing process. To make this possible, the freeformer automatically interrupted the process at each respective layer, so that the coil, circuit board and plug could be precisely integrated. In a separate process, a dispenser was then used to produce the silver conductor tracks inside the casing. To complete the process, all that was needed was to overprint the cavities and then put them in polyurethane.

The team produced more than 30 demonstration models of customized sensors and tested them. The components had to be able to withstand temperature changes and vibrations, be waterproof and pass an electrical insulation test. By optimizing the design and manufacturing process, the tests were ultimately completed successfully.