A fuel nozzle was grown, because a drill could not reach

The fuel nozzle of the LEAP jet engine is printed in metal, as one piece, with internal passages that a drill cannot reach because they do not open in a straight line.

A laser melts a thin layer of metal powder in the places the part should be solid, the bed drops, and the next layer follows. Leave a region unmelted and it is a channel, even if the channel bends, branches, or spirals. The LEAP nozzle uses that freedom to mix fuel and air in a geometry that used to be an assembly of many parts, each one a compromise with the drill. Tens of thousands of the printed nozzles have gone into engines.

Printing does not abolish defects. Pores, residual stress, and a surface that looks like a stack of contours are the new problems, and they are inspected rather than wished away. The method earns its place only where the shape is worth the trouble — cooling passages, lattices, and this nozzle — not where a billet and a lathe are cheaper, which is most places.