A three-dimensional printing system having a light beam radiating unit is provided, which radiates a light beam onto the powder layer to be sintered or melted, solidifying the powder, a scanning mechanism which redirects and focuses the light beam in a three-dimensional space, a cover that moves integrally with the scanning unit of the light beam, wherein an inlet nozzle and an exhaust manifold ensure inert atmosphere to the process, a powder delivery unit that supplies this material over the object construction area; a powder leveling device leveling the powder delivered from the powder delivery unit to form a powder layer, a powder supply unit for storing and metering material for the delivery unit, constituting a module independent from the system.