An additive manufacturing system for producing a three-dimensional article includes a print engine, a post-fabrication powder removal apparatus, a transport mechanism, and a controller. The post fabrication removal apparatus includes a rotary frame defining an internal receptacle cavity, a plurality of clamps coupled to a corresponding plurality of actuators, a clamping plate coupled to a lift apparatus, and an agitation device mounted to the clamping plate. The controller is configured to perform the following steps: (1) Operate the transport mechanism to transport the build box to the internal receptacle cavity. (2) Operate the plurality of actuators to engage the build box with the plurality of clamps to secure the build box to the rotary frame. (3) Operate the rotary frame to rotate the build box until unfused powder begins to exit the build box. (4) Operate the agitation device to facilitate pouring of the unfused powder from the build box.