Strong together: Laser and print technologies

As if by magic, letters, a part number, and a QR code appear on the white label. No ink, paint, or other consumables are in sight. No material is removed. Rather, a CO2 laser exposes the surface coating of the adhesive label. Its color changes to a full black where the concentrated light comes into contact. The needle-sharp label is smear-proof, scratch-proof, and can be individualized at a push. The system from HERMA exposes and adheres up to 200 laser-activated labels per minute. The CO2 laser is supplied by Koenig & Bauer Coding GmbH, which specializes in industrial labeling technology. The company also offers similar color-changing laser labeling for plastic packaging.

Fast, flexible product labeling is an absolute must in fully automated process chains of Industry 4.0. It is the basis for products taking individual routes through the production chains to shipping—while the quality is monitored and documented seamlessly. The laser-activated labels are a clean, low-maintenance, reliable, machine-readable solution. Their true strengths are especially obvious in industries with high hygiene standards and in labeling on flexible, highly stressed surfaces.

Individualized sensors and contacting

Apart from individual article codes, sensors are also an interface between the digital and real worlds in the cyber-physical systems of Industry 4.0. Close-meshed sensor networks are the basis of fully automated factories and plants. In the Fraunhofer lighthouse project “Go Beyond 4.0”, six institutes have teamed up to promote the direct integration of sensors into automotive and aircraft components and lighting systems. To do this, they also combine elements of print technology with modern laser processes.

The Fraunhofer scientists use inkjet, pad and dispenser printing methods to print extremely thin electronic layers on components. To prepare these print processes, they structure the surfaces specifically with laser ablation and prime them with polymer insulation layers. After conductive inks have been applied, further laser processes are used. First, they dry the wet electronics layer and remove all solvents and auxiliary materials. This is followed by laser heat treatment to melt the micro and nano particles made from silver, gold, or other conductive materials that are dissolved in the ink. Laser heat treatment is not only faster, more flexible, and more energy efficient than oven dryers. The combination of flexible print processes in which the shape, width, and thickness of the electronics layer can be freely varied, also with highly flexible laser processes, allows maximum freedom in the design of the electronics. And because traces and contacts with tiny amounts of particles can be printed exactly where they are needed, consumption of expensive precious metals is also reduced; especially with contacts that, in the past, have been fully gold-plated in galvanic processes.

Many potential applications

The Fraunhofer Institute for Laser Technology, ILT, has used additive manufacturing to make strain gauge strips. Colleagues at the Fraunhofer Institute for Machine Tools and Forming Technology, IWU, use it to integrate electronic modules and mechatronic functions in car doors—including sensors, switches, LEDs, and traces. Robots guide the print heads and lasers over the components. Consequently, manual contacting and cabling of automobiles and aircraft can now be automated. But researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials, IFAM, are going one step further. They are working on integrating heating wires into composites of aircraft wings with print-laser processes. This could prevent wings icing up and save passengers a lot of chaos in winter. Even direct integration of pressure and temperature sensors in carbon and fiber glass structures of the fuselage and wings seems feasible. Thus, the combination of print and laser technologies in aircraft manufacture would really lead to a world “Beyond 4.0”.