For plastic or steel?

Didn't Nasa claimed to have sucessfully print fuel injector for the combustion chamber for shuttle program?

That being said, they still struggle with DMLS or SLA, the local cristalline structure is inconsistent. For instance you have the laser sintering manage to melt through 5 underlayer, which makes the material properties inconsistent. Yet, the material has to be known since they use a very tight safety factor. At least, that's what I recalled from the Turbo Expo 2015.

Other than that they can print inconel if that interest you.