Abstract: Electron beam powder bed fusion may be performed using waste powder from laser beam powder bed fusion by pre-heating a build chamber using stepped increases of electron beam current. To perform the pre-heating without smoking the powder, a plurality of predetermined interim temperatures, ranging from an ambient, resting temperature of the build chamber to a predetermined preheated temperature, are determined. A build plate within the build chamber is exposed to a plurality of streams of electrons, one at a time, while the build plate is surrounded by the waste powder. Each stream of electrons has a progressively increasing current, with the current being increased each time an actual temperature of the build chamber reaches or exceeds the next predetermined interim temperature. The actual temperature of the build chamber is monitored during the pre-heating, to compare the actual temperature of the build chamber to the plurality of predetermined interim temperatures.