A large format DMLM system using a continuously rotating powder bed

The aircraft engine industry manufactures many ring-like metal parts of large diameter but small cross-sectional area. Designers of these parts require increasingly complex geometries for improved aerodynamic efficiency and cooling while manufacturers of these parts require larger and faster equipment for high productivity and low cost. The combination of these industrial requirements inspired the development of a new Direct Metal Laser Melting (DMLM) architecture, reported here, which incorporates a rotating powder bed. The system coordinates the rotational motion of the powder bed with an ascending laser scanner and recoater to build parts in a helical fashion. A single-point powder feeder delivers metal powder near the inner radius of an annular build volume, and a recoater spreads the powder to the outer radius in a “snow plow” fashion. Because the recoater and laser scanner are installed at different angular positions, they operate independently and simultaneously. Encoder feedback from both the rotational stage and the galvanometers assures accuracy of the laser scan path. A prototype system was built to demonstrate this new concept for an aircraft engine combustor liner (600-mm dia. x 150-mm ht.) and showed continuous laser utilization exceeding 97%. Build rates were shown to triple conventional DMLM systems while powder requirements were decreased by more than 4x.