Laser powder bed fusion (L-PBF) has drawn increasing attention as additive manufacturing technique for industrial production over the last years. However, the existing machine technology constitutes certain limitations in terms of scalability of both melting rate and build envelope. The present work contributes to a future overcoming of these restrictions via development and practical evaluation of a novel L-PBF process. Instead of deflecting a single laser spot via a galvanometer scanner, a fixed array of several adjacent spots generated by individual fiber-coupled diode laser systems is applied by a working head, while beam positioning is carried out by a system of linear drives.
In a suchlike system, the melting rate can be increased by adding spots to the array instead of adapting laser power and/or size of individual spots. Due to a local shielding gas system mounted to the working head, constant processing conditions in the interaction zone can be achieved, enabling increased scalability of the build envelope independently from the optical system
After the development of a suitable laboratory system, fundamental investigations are carried out for stainless steel 316L, evaluating the correlations between process parameters and melting track stability, melting depth profile and shape of solidified melt. Subsequent experiments demonstrate the feasibility to generate sample parts with high density (> 99,5 %). Furthermore, surface quality, dimensional accuracy, detail resolution and mechanical properties are evaluated. Achievable processing times are compared to the conventional L-PBF process for both experimentally validated parameters as well as theoretical upscaling.
Laser Powder Bed Fusion of Stainless Steel with High Power Multi-Diode-Laser-Array
The present work addresses the development a new exposure concept for Laser Powder Bed Fusion (L-PBF) based on a multispot-array generated by several fiber-coupled diode laser systems. A first demonstrator machine is developed, allowing for a systematic evaluation of the correlation between process parameters and resulting part quality. It is shown that parts with relative density of more than 99,5 % can be manufactured by that means.