UK researchers have developed a new additive manufacturing process known as Diode Area Melting (DAM). This new approach to metal 3D printing which could lead to much faster production rates. Their work supported by funding from an Engineering and Physical Sciences Research Council (EPSRC) allocated impact acceleration grant (IIKE), and conducted primarily at the University of Sheffield, was published in the Science Direct Journal.
The published paper details the development of the new DAM additive manufacturing process which utilizes customized architectural arrays of low power laser diode emitters for high speed parallel processing of metallic feedstock. Individually addressable diode emitters are used to selectively melt feedstock from a pre-laid powder bed. The laser diodes operate at shorter laser wavelengths (808 nm) than conventional SLM fibre lasers (1064 nm) theoretically enabling more efficient energy absorption for specific materials. The melting capabilities of the DAM process were tested for low melting point eutectic BiZn2.7 elemental powders and higher temperature pre-alloyed 17-4 stainless steel powder. The process was shown to be capable of fabricating controllable geometric features with evidence of complete melting and fusion between multiple powder layers.
Additive Manufacturing (AM) is viewed as a disruptive, viable alternative to conventional manufacturing processes, capable of creating geometrically efficient structures with low material wastage. Laser based Selective Laser Melting (SLM) and electron based Electron Beam Melting (EBM) AM systems are increasingly being used in high value sectors to directly manufacture metallic end-use parts from a variety of alloys. During processing, the melting source (deflected laser/electron beam) selectively scans and melts regions of a pre-deposited powder bed. Cross-sections of the part are fused in layers, built up successively to create the complete 3D object. The method of layered fabrication, combined with the high precision of laser melting allows for a greatly expanded design freedom with minimal feedstock waste.
The Diode Area Melting (DAM) method replaces the deflected fibre laser used within SLM with multiple emitters co-located within a customised DL bar. Diode Lasers (DLs) are some of the most efficient devices in converting electrical into optical energy, working at wall plug efficiencies up to 50–80%. The ability to tune the emission wavelength of DLs through choice of semiconductor active material allows DLs to be designed or selected to match the peak absorption wavelength of the powder material being irradiated.
The DAM process is highly scalable for the melting of larger areas in a single pass. DL bars consume a relatively small space and can be stacked easily to either cover a larger melting area or to superimpose laser beams such that the energy density per laser beam spot is increased. The scientists conclude that the current limitations of AM of metals systems (i.e. high purchase costs, high energy consumption and slow production time) may be overcome through the adoption of a diode laser module melting source. Previously, the use of low power diode bars for melting common SLM materials would be easily dismissed as being unable to provide the required energy density to melt these materials. This work has shown that this energy density challenge can be overcome and presents a first step in developing a novel and efficient high speed metallic additive manufacturing process.