There was a news about metal sintering used for an actual market (sorry, memory failing). That reminded me of this video and got me wondering how complicated it was to control the beam focus and energy. To allow for finer and leaner shapes.
Its an example of a piece of technology that depends on numerous contemporary things. You need razor sharp cutting tools to keep the pores open, so it has to be a "post-carbide" era tool. You need a vacuum pump to fill the pores with oil. You need modern non-drying low acidity mineral oils because something like veg oil or whale oil would break down both the bearing and the shaft in a couple years. The powder is heated precisely and under some pressure, a lot more precise than a blacksmiths shop.
Speaking of pressure, reproducible and reliable sintering seems to always require some amount of pressure, which is a problem for 3-d printing, either you're using somewhat exotic process, or the product needed pressure so it is going to be weak.