For some pretty reasonable reasons, 3D printing of metal components lags a bit behind that of polymers. The best metal components I’ve seen look pretty rough, while some high-end plastic parts are optically smooth. Still, progress is being made:

Amaze project aims to take 3D printing ‘into metal age’

Tungsten alloy components that can withstand temperatures of 3,000C were unveiled at Amaze’s launch on Tuesday at London’s Science Museum.

Tungsten. Yow. Lots of rockets use tungsten alloys in the throats due to the hardness and heat resistance of the metal. But manufacturing tungsten components is amazingly difficult for those same reasons. If these 3D tungsten parts of are adequate strength and smoothness, there just might be a revolution in small rocket engines.

I wonder if 3D printing can make tungsten components that have silver mixed in. Back when I worked on booster sep motors for the Shuttle at UTC, NASA became interested in tungsten throat inserts that were “silver infiltrated.” By mixing silver in with the tungsten, the thermal conductivity of the tungsten could be substantially improved. And while tungsten can take a hell of a lot of heat, it will merrily melt if brought to the combustion temperature of mundane solid propellants. By increasing the thermal conductivity, hot-spots in the tungsten can be smoothed out. The result would be a more survivable – and more reusable, thus cheaper –  throat insert. This might not be of much value for a, say, Sidewinder air-to-air missile… but it might be pretty good for a Sidewinder model rocket using high-end amateur rocket motors.