Energy use and productivity assessment of laser welding for a digitalized production in thin film food packaging

In food packaging thin films of layered polymeric materials are used as containers, wrapping elements, as well as insulators. The legislation changes in the EU mandate a better usage of resources and recycling of these materials that correspond to a large fraction of polymeric material consumption in the world. The next generation of packaging materials are expected to incorporate fewer layers and less colouring elements for easier recyclability. Moreover, the energy usage in the production cycles should be reduced. The flow pack technology used in the packaging industry conventionally employs rotary welding tools that provide the required joint via simultaneous application of heat and pressure. The welding process requires a constantly heated rotary tool, which is also a bottleneck in terms of weld size and geometry variations. Laser welding can provide the required flexibility as a fully integrated digital tool. On the other hand, the weldability of thin films transparent polymers requires a careful assessment mechanical strength, process productivity, as well as energetic consumption. In this work, welding of two commercially used flow pack materials namely PET+LDPE and BOPP is studied with laser solutions from NIR to MIR range using solid-state laser technologies namely diode and fiber lasers with and without absorbent layers. The weld strength and energy consumption were assessed and compared to the conventional welding operation with the rotary weld heads. The results show that laser welding can provide a process with a higher energetic efficiency and improved strength with relatively moderate power levels. While the productivity of the conventional process appears to be higher, the employed moderate laser powers (i.e. ≤250 W) should allow for process scalability for industrial production.