Additive Manufacturing (AM) is emerging as a mainstream manufacturing technology, and demand for large part manufacturing is getting stronger. Direct Metal Deposition (DMD) is a DED technology based on laser and powder metal application using a closed-loop-feedback control system. This presentation will give an overview of the DMD technology highlighting its capability to scale up to large size parts. The focus will be DM3D’s new multi-nozzle DMD technology capable of printing parts up to 10ft in diameter, 10ft in height and 5000 lbs. in weight. The multi-nozzle DMD technology doubles the part throughput with a further possibility of quadrupling it. Other challenges such as residual stress and distortion related to large scale AM will be discussed in detail. Simulation approaches to mitigate such challenges will be demonstrated through example parts. Finally, a case study involving 3D printing of a very large size real-world part, namely NASA’s RS 25 engine nozzle will be discussed. Benefits and risks of 3D printing such parts that are more than 9ft in height and weighs more than 3500Lbs will be highlighted.