A post-build powder removal system includes a work bed, a platform wall having at least one powder evacuation port, and an evacuation port sealing system operable for selectively closing and opening the powder evacuation port. The platform wall cooperates with the work bed to define a powder chamber. The evacuation port sealing system includes an external sleeve slidingly fitted onto the exterior surface of the platform wall such that the external sleeve is slideable in a first direction closing the at least one powder evacuation port and slideable in an opposite second direction opening the at least one powder evacuation port.