US Patent 7854885 Method of making an article

A method of making an article having at least one re-entrance surface includes the steps of (a) forming a layer of metal powder on a base, (b) selectively laser fusing portions of the layer, and (c) repeating steps (a) and (b) to form the article, each step (a) being performed on the preceding layer characterised in that prior to performing step (a) in a layer which will initiate the formation of a re-entrant feature reversibly bonding at least some of the unfused underlying powder such that it is stable under the application of the laser.