An automatic loading unit for bending pins supporting bars, adapted for systems for manufacturing three-dimensional lattice-like structures or frames derived from electro-welded metal grids, characterized in that it cooperates in coordination to service a machine for bending electro-welded metal grids and/or to serve to a bending machine that is included in a system for the continuous production of three-dimensional lattice-like frames derived from said grids, having a frame-supported station and a magazine for bending pins supporting bars, wherein - the frame-supported station rests on the floor on two shoulders, of which one is proximate to the bending machine to be served, said shoulders being mutually connected in an upward region by an adapted lattice girder system that is capable of supporting a rectilinear sliding guide, which is horizontal and longitudinal with respect to the bending machine, on which an upper carriage slides which is provided with a clamp or clamps or other means for the automatic grip of the ends of the bars, which are directed downward, and moved by an adapted motion transmission system and associated motor, two other guides (14, 18) being arranged on the two shoulders, in a downward position with respect to the sliding guide, said two other guides (14, 18) being horizontal and perpendicular to the sliding guide, the two ends of the structure for supporting the magazine for supporting the bars sliding on command said two other guides (14, 18); and wherein - the magazine for bending pins supporting bars is preferably of the horizontal type and has a plurality of side-by-side stations, each provided with a plurality of idle rollers for the longitudinal sliding of the bars, the magazine being movable automatically in both directions at right angles to the guide and to the bending machine, the seats on the stations that accommodate the bars of the magazine being therefore individually arrangeable in the horizontal direction and on the same longitudinal working axis of the bending machine to be served, in order to facilitate the movement of the bars longitudinally and coaxially to the bending machine from the magazine to the machine and vice versa by means of said upper carriage. - the frame-supported station rests on the floor on two shoulders, of which one is proximate to the bending machine to be served, said shoulders being mutually connected in an upward region by an adapted lattice girder system that is capable of supporting a rectilinear sliding guide, which is horizontal and longitudinal with respect to the bending machine, on which an upper carriage slides which is provided with a clamp or clamps or other means for the automatic grip of the ends of the bars, which are directed downward, and moved by an adapted motion transmission system and associated motor, two other guides (14, 18) being arranged on the two shoulders, in a downward position with respect to the sliding guide, said two other guides (14, 18) being horizontal and perpendicular to the sliding guide, the two ends of the structure for supporting the magazine for supporting the bars sliding on command said two other guides (14, 18); and wherein - the magazine for bending pins supporting bars is preferably of the horizontal type and has a plurality of side-by-side stations, each provided with a plurality of idle rollers for the longitudinal sliding of the bars, the magazine being movable automatically in both directions at right angles to the guide and to the bending machine, the seats on the stations that accommodate the bars of the magazine being therefore individually arrangeable in the horizontal direction and on the same longitudinal working axis of the bending machine to be served, in order to facilitate the movement of the bars longitudinally and coaxially to the bending machine from the magazine to the machine and vice versa by means of said upper carriage.