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 producinghigh-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. <br/

Process optimisation of PA11 in fiber-laser powder-bed fusion through loading of an optical absorber

Industrial laser processing is rapidly shifting towards fiber lasers with wavelengths between 780nm and 2200nm. This can be largely contributed to the excellent beam properties and, ease of operation. However, for Additive Manufacturing of polymers, CO2 lasers at wavelengths of 10,6µm are pre- dominantly used. CO2 lasers provide unmatched energy absorption by the C-H bonds of Polyamide (PA). To remedy this, the current study investigates using a high-power fiber laser (1080nm) for consolidating PA11 mixed with a black optical absorber. Several compositions are produced by mixing commercially available white and black powder. Aiming at finding the optimum optical absorber loading and the corresponding process parameters, allowing the highest possible compo- nent fidelity, while achieving the lightest hue of grey possible to allow for later colouring. The experiment is conducted on an in-house developed Open Architecture Laser Powder-Bed Fusion system. The parts are examined through, surface roughness, and mechanical characterisation.Mechanical Engineerin

Simple sensor manufacturing by Laser Powder Bed Fusion of conductive polymer blends

The efficacy of manufacturing conductive plastic components by the Material Extrusion (MEX) method has been shown previously by Grønborg et al. [1]. To increase the effectiveness of additive manufacturing of these sensors a study utilising Polymer Laser Powder Bed Fusion (L-PBF) technique has been undertaken. The study investigates; the conductive networks created during manufacturing and the influence of processing parameters on the conductivity of the parts. The test specimen has been manufactured on the Open Architecture Polymer L-PBF system developed at the Technical University of Denmark. Utilising the capability of full-scale process control, and the implemented high-power fiber laser to achieve consolidation of the powder. The feedstock material has been designed to allow high energy absorption at the fiber laser wavelength (1080 nm), and thermal properties to comply with the L-PBF process. A conductive network manufactured by the Polymer L-PBF process is demonstrated. The parts produced have been tested by measuring the material's conductivity at the initial unaltered state, and further investigated by SEM micrographs to conclude on the stability of the manufactured parts.</p