A control loop for extrusion of a metallic build material such as bulk metallic glass measures a force required to extrude the build material, and uses this sensed parameter to estimate a temperature of the build material. The temperature, or a difference between the estimated temperature and a target temperature, can be used to speed or slow extrusion of the build material to control heat transfer from a heating system along the feedpath. This general control loop may be modified to account for other possible conditions such as nozzle clogging or the onset of crystallization.