A three-dimension printer comprising: a print bed for supporting an object to be printed; a printer bar extending along a transverse axis; and a printer bar carriage assembly supporting the printer bar with respect to the print bed to move longitudinally above the print bed at a predetermined height above a print surface over the print bed ; characterized in that : the printer bar supports a plurality of independently controllable, transversely separated electron sources for generating electron beams directed toward the print bed and an electron deflector assembly for transverse deflection of the electron beams ; the printer further comprises a powder handling system for applying powder at the print surface over the print bed ; the printer further comprises a controller communicating with the electron sources and printer bar carriage assembly to scan the electron sources over powder on the print bed to selectively fuse the powder at the print surface into a printed object according to a program stored in a non-transient medium; the electron sources and electron deflector assembly are arranged such that a transverse range of deflection measured at the print surface of at least one of the electron sources overlaps with a transverse range of deflection measured at the print surface of an adjacent electron source ; and the electron beams are constrained to move substantially only in the transverse direction with respect to the printer bar . a print bed for supporting an object to be printed; a printer bar extending along a transverse axis; and a printer bar carriage assembly supporting the printer bar with respect to the print bed to move longitudinally above the print bed at a predetermined height above a print surface over the print bed ; characterized in that : the printer bar supports a plurality of independently controllable, transversely separated electron sources for generating electron beams directed toward the print bed and an electron deflector assembly for transverse deflection of the electron beams ; the printer further comprises a powder handling system for applying powder at the print surface over the print bed ; the printer further comprises a controller communicating with the electron sources and printer bar carriage assembly to scan the electron sources over powder on the print bed to selectively fuse the powder at the print surface into a printed object according to a program stored in a non-transient medium; the electron sources and electron deflector assembly are arranged such that a transverse range of deflection measured at the print surface of at least one of the electron sources overlaps with a transverse range of deflection measured at the print surface of an adjacent electron source ; and the electron beams are constrained to move substantially only in the transverse direction with respect to the printer bar . the printer bar supports a plurality of independently controllable, transversely separated electron sources for generating electron beams directed toward the print bed and an electron deflector assembly for transverse deflection of the electron beams ; the printer further comprises a powder handling system for applying powder at the print surface over the print bed ; the printer further comprises a controller communicating with the electron sources and printer bar carriage assembly to scan the electron sources over powder on the print bed to selectively fuse the powder at the print surface into a printed object according to a program stored in a non-transient medium; the electron sources and electron deflector assembly are arranged such that a transverse range of deflection measured at the print surface of at least one of the electron sources overlaps with a transverse range of deflection measured at the print surface of an adjacent electron source ; and the electron beams are constrained to move substantially only in the transverse direction with respect to the printer bar . <EOS>