An explosive device, such as a munition or a part of a munition, has an explosive material surrounded by a casing that has one or more voids within the casing. The one or more voids define sizes and shapes of the fragments that the casing breaks into when the explosive material is detonated. The casing may be made using an additive manufacturing process, with the one or more voids fully between an inner surface of the casing and an outer surface of the casing. The voids may substantially define the size and shape of fragments making up a majority of the volume of the casing, such as 75% or more of the volume of the casing. The voids may change direction within the casing, for example branching and intersecting to define a plurality of rectangular (parallelepiped) or other shaped fragments.