Machining processes in the field of plastics technology have wide-ranging requirements. The Fraunhofer Institute for Laser Technology ILT has developed and qualified customized processes through to turnkey production systems for welding, cutting, drilling, structuring and marking of plastics.
Laser transmission welding of plastics produces concealed joints with a minimal impact on the components. In this process laser radiation is transmitted through the first joining partner, with the energy absorbed by the second joining partner at the interface between the two. The plastic melts and joins the two components by means of heat conduction. Process development is closely linked to the material selection and the adapted energy deposition strategies. By carefully selecting laser source, beam shape and adapted irradiation strategy, users can join standard transparent and laser-absorbing plastics as well as other combinations.
When the laser wavelength is matched to the optical properties of the plastics, sufficient energy deposition can be achieved, even for optically transparent plastics without absorption enhancing pigments, which are frequently used in medical technology. Special focusing optics with a high numerical aperture allow the energy to be concentrated in the joining plane so that the threshold level required to melt the plastics is reached. The radiation intensity on the component‘s surface is so low that the laser does not damage the components.
Multilayer films are commonly used for packaging technology and the encapsulation of organic electronics. For film applications, which often require very high format flexibility, the use of laser radiation as a welding tool offers particularly key advantages compared to conventional tools with a fixed joining contour. Depending on the process requirements, laser transmission welding or gap welding can be used to connect the films. Moreover, multilayer film composites can be joined that contain barrier layers or metallic components as well as those made out of different plastics.
Laser beam welding can be used to manufacture complex composite fiber components out of several elements as well as to generate hollow structures. With this contact-free process closed reinforcements can be created, which increase component stiffness, as can local points of contact and joining elements to enhance component functionality without requiring complex process steps.
For reasons of cost and stability, lightweight components are generally made up of different materials. The ability to join plastics and metallic components is, therefore, becoming increasingly important. Laser microstructuring of the metal surface creates undercuts into which the plastic can flow in the subsequent joining process. In this respect, lightweight design potential can be leveraged extensively by joining appropriately pretreated metal with fiber-reinforced plastic.
Thanks to its small heat affected zone and high process speed, the laser is an ideal solution for cutting, drilling, structuring and marking of polymers. Depending on the type of material, CO2 lasers as well as solid-state lasers can be used. Based on process developments and qualification studies, industrial manufacturing equipment and components are being planned and built which will find their way into applications in the automotive industry, medical engineering, filter technology and packaging technology.
Process control and monitoring is indispensable for reliable high-performance manufacturing processes. Various pyrometric, CCD and thermal camera-based systems, which are integrated into the purpose-built optical processing head, provide process data for simulations aimed at understanding processes and optimizing their speed and quality.
Fraunhofer Institute for Laser Technology ILT
