Developed at the University of Sheffield, Diode Area Melting (DAM) represents a novel development in Laser Powder Bed Fusion (L-PBF) technologies. This method diverges from traditional mirror galvanometer-controlled laser techniques by employing an array of low-powered diode lasers, each with a power output of less than 5 watts. In contrast to traditional L-PBF, which employs high-powered fibre lasers with outputs exceeding 100 watts at speeds ranging from 300 to 3000 mm/s, DAM operates these diode lasers at significantly reduced speeds of 1 to 10 mm/s.
The essence of this research involves exploring the interactions between multiple diode lasers and powder materials within the DAM process. It focuses on forming single tracks and two-dimensional layers, crucial for constructing three-dimensional final parts. The study investigates how the quantity of lasers affects the melt pool size and cooling rates, utilising multiple lasers arranged in a linear array. In the modelling phase, the study utilises up to six lasers arranged in a linear array and employs Finite Element Method (FEM) simulations, analytical approaches, and thermal camera measurements to analyse the intricate dynamics of the multiple laser-powder interactions within the DAM process.
In the processing of Ti6Al4V, the experimental findings shows that a single laser achieves a cooling rate of 778 K/s, which decreases to 191 K/s when employing six lasers, closely resembling the slower cooling rates observed in some casting processes. Furthermore, a single layer of Ti6Al4V processed using DAM demonstrates lower residual stresses, with a reduction in stress noted as the number of lasers is increased and the scanning speed is decreased. Microstructural analysis indicates the presence of both α + β crystal structures, with variations mainly influenced by scanning speed. These enhancements, along with the ability of DAM to process larger areas through the use of multiple lasers, potentially improve both efficiency and throughput, marking an important shift from conventional L-PBF methods. Consequently, leading to important benefits for large-scale production with enhanced part quality and reduced need for post-processing.
