An additive manufacturing apparatus includes a vat with multiple chambers and at least one of the chambers is a resin chamber configured to receive a radiant-energy-curable resin. A build surface is defined by the resin chamber within the vat, wherein at least a portion of the build surface is transparent. The additive manufacturing apparatus includes a stage that is positioned facing the vat and the build surface and the stage is configured to hold a stacked arrangement of one or more cured layers of the radiant-energy-curable resin. A method is provided for operating the additive manufacturing apparatus such that successive chambers of resin are cured. While a chamber of resin is being cured, another chamber can participate in other steps such as unloading or loading of resin. Optionally a stage cleaning step can be conducted while an unloading or loading of resin is conducted in one of the resin chambers.