Evolving the Landscape of Polymer Laser Powder Bed Fusion: Expanding Frontiers in Process and Materials

Laser Based Powder Bed Fusion of Polymers (PBF-LB/P) is one of the pioneering Additive Manufacturing (AM) processes, using a laser to selectively consolidate a powder feedstock into threedimensional (3D) components. The technique functions by depositing a thin layer of powder in the build plane of the system, laser scanning the cross-sectional area of the geometry, and repeating this cycle in a layer-by-layer fashion to fabricate a component. This allows the production of complex geometries unattainable by conventional processing while inheriting mechanical properties resembling those of traditional plastic fabrication.

Conventional PBF-LB/P systems utilise a CO₂ laser to consolidate the powder. This study aims to investigate the utility of a fibre laser source for processing polymer powders. The functionality of the fibre laser in the process was extensively studied through three primary investigations. The first study focuses on developing the relevant process knowledge and understanding of laser processing of polymer powders, describing the critical influential factors for developing an experiment capable of defining the fibre laser utility. The second investigation relates the critical elements of the first study, delivering an experimental infrastructure designed for testing the main hypothesis. The third and final exploration establish the functionality of the fibre laser in the process, utilising the laser source in the experimental infrastructure for producing components, which were scrutinised concerning the success of the production.

To investigate the fibre laser utility in the process, an open architecture system is constructed. The open architecture allows access to all relevant process settings and parameters. This is achieved by utilisation of the tools developed throughout the Open Additive Manufacturing Initiative, presenting the open architecture for several industrially relevant AM processes.

The main driver and hindrance for fibre laser processing of polymers is the wavelength of 1080 nm,
delivered by the laser. This wavelength does not match the agitation frequency of the polymer constituent elements or compounds, leading to low energy absorption by the polymer. The wavelength, however, allows for the small spot size and considerable Rayleigh length of the laser.

A metric for the requirement of an optical absorber was examined and quantified by fibre laser processing polymer powder, utilising the experimental infrastructure. The study investigated the use of two different coloured powders of the same type of PA11 polymer, where one is the pure white type, and the other contains the optical absorption quality by being coloured black. A minimum concentration of 5% black powder in a mix of white and black is sufficient for producing
high-fidelity components.

From the exploration of the utility of fibre lasers in PBF-LB/P, it is concluded that the laser source can deliver satisfactory detail resolution, comparable to what is found in the industry. The fibre laser aid the utilisation by providing key parameters not offered by the conventional CO₂ laser source. These are the ease of beam delivery, high beam quality, and considerable Rayleigh length, enabling the fine details achieved herein.