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 (12) of electron beam additive layer manufacturing apparatus (10), 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 (17) to form the layer in the build zone and also an accumulation of excess powder material in an accumulation zone adjoining the build zone.

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 (12) of electron beam additive layer manufacturing apparatus (10), 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 (17) to form the layer in the build zone and also an accumulation of excess powder material in an accumulation zone adjoining the build zone.