Method of monitoring and influencing an additive layer manufacturing process

Abstract

A method of monitoring and influencing an additive layer manufacturing process, in which selective fusing of powder material in successively applied layers is carried out to manufacture a three-dimensional article, comprises delivery to a work space, for example in a vacuum chamber () of electron beam additive layer manufacturing apparatus (), of a quantity of the powder material in excess of that required to form a layer of a given volume in a build zone of the space and spreading the powder material within the work space by a spreader () to form the layer in the build zone and also an accumulation of excess powder material in an accumulation zone adjoining the build zone. Spreading is repeated to form successive such layers and accumulations and the volume of each accumulation is determined by imaging, along an optical path (B), of a structured light pattern which has been projected along an optical path (A), onto the respective accumulation from an imaging direction different from the projection direction so as to result in distortion of the pattern by the accumulation. The imaged pattern is then able to be evaluated to derive the volume of the accumulation from the distortion and the determined volumes of the accumulations are utilised to influence the additive layer manufacturing process.