Machine Technology for Laser Powder Bed Fusion

The Fraunhofer Institute for Laser Technology ILT has been developing the additive manufacturing process Laser Powder Bed Fusion (LPBF) since the mid-1990s and, ever since, has been consistently advancing  the entire LPBF process chain. The institute aims to qualify the process for use in industrial production and to  integrate it into existing production processes. To accomplish this, the experts at Fraunhofer ILT work together with customers from industry and research on an interdisciplinary basis.

Since LPBF builds up structure directly from CAD data layer by layer, it can produce highly complex components from metallic materials without using shaping tools, materials that cannot be produced using conventional manufacturing processes such as casting or machining. LPBF can be used to generate novel components with innovative functionalities because previous production-related restrictions are no longer relevant.

Almost all currently available LPBF machines have a movable build platform on which a powder layer is applied by a powder coating unit. The surface of this powder bed is then melted by laser in accordance with the component geometry to be produced. The laser beam required for this is deflected via a galvanometer scanner and focused with a flat field lens (F-theta optics) or a vario optical system. Metallic materials are processed in an inert gas atmosphere, with the gas circuit also performing the task of removing flue gases and process-related spatter.

The components used (beam source, optics, powder applica-tion unit and axis systems) influence various properties of the overall system, such as process speed, downtime, component quality and automation capability. The appropriate selection and combination of individual components for the correspond-ing application is, therefore, decisive for the economical use  of Laser Powder Bed Fusion.

Based on years of experience and competence, Fraunhofer ILT experts can support you individually from your initial idea, through feasibility studies and concept development, all the way to implementing and integrating the systems into your production environment. Not only is our extensive plant equipment, consisting of various commercial systems and highly flexible laboratory systems, at your disposal, but also our profound know-how in the field of laser beam source  and optics development.

Since we cooperate closely with RWTH Aachen University and FH Aachen University of Applied Sciences, you benefit from the bundled competence of the Aachen location in the field  of additive manufacturing. Fraunhofer ILT is therefore your com-petent partner in all areas of additive manufacturing using LPBF.

An essential prerequisite for LPBF to be successfully industria-lized is the scalability of the machine technology – in terms of build volume and productivity. For this purpose, Fraunhofer ILT is developing innovative machine concepts based on mobile processing heads with local shielding gas guidance, concepts that enable simple scaling of the build volume. Multi-beam source systems are used to increase productivity, whereby both classic galvanometer scanners and novel kinematics concepts are being investigated.

The process and cost efficiency of the LPBF process can be increased by using adapted laser and optical systems. Fraunhofer ILT is testing new laser beam sources with short-wavelength light that promote efficient energy coupling, in particular for highly reflective materials such as pure copper. In addition, cost-effective diode laser systems are being qualified for use in LPBF and optical systems developed for adaptive beam shaping, both of which will enable higher build-up rates.

Component distortion and cracking in LPBF can be prevented by suitable preheating. Fraunhofer ILT has preheating systems that reach temperatures of up to 1200 °C and enable sophis-ticated materials susceptible to cracking to be processed crack-free. In addition to conventional build platform heating, novel systems are being developed for direct preheating at the process level. This enables constant preheating conditions to be achieved regardless of the component size.

Reproducible process and component quality is essential for LPBF to enter series production. In order to guarantee this, adapted process monitoring systems are required. Fraunhofer ILT uses pyrometers and camera-based systems to analyze and monitor the LPBF process. It is also investigating platform technologies for integrating measurement data relevant to the process into cloud-based systems and suitable analysis methods.

In addition to our many years of experience and profound know-how in the field of LPBF, you can also benefit from  the extensive equipment at Fraunhofer ILT:

• Various laser beam sources (wavelengths, intensity distributions, multi-kW powers)
• Different optical systems (lenses, scanners, etc.),
• Flexible laboratory machines for testing new types of laser, optical or protective gas systems
• Measurement technology for the characterization of LPBF machines (laser, optics and shielding gas)
• LPBF preheating systems.