US Patent 9561626 Controlling build chamber temperature

A build chamber of a three-dimensional printer uses directed heat to preheat a region within the chamber where a build will be initiated, and then uses circulating, heated air to maintain a target temperature for the entire build volume after the build is initiated. A fixed heating element and blower may advantageously be used for both heating steps, and preheating may be accomplished more quickly by initially directing heat at the locus of build initiation rather than diffusing heat throughout an entire build volume.