Method of monitoring and influencing an additive layer manufacturing process
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. 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.
1 . 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, the method comprising:
delivering to a work space 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 work space;
spreading the powder material within the work space to form the layer in the build zone and to additionally form a ridge-shaped accumulation of excess powder material in an accumulation zone adjoining the build zone;
repeating the step of spreading to form successive such layers and accumulations;
determining an at least approximate volume of each accumulation by imaging of a structured light pattern which has been projected onto a confronting face of the respective ridge-shaped accumulation, the imaging being from a direction different from a direction of the projection so that distortion of the projected pattern by the accumulation is produced in the imaged pattern, and by evaluating the imaged pattern to derive from the pattern distortion the at least approximate volume of the accumulation responsible for the distortion; and
influencing the additive layer manufacturing process in dependence on the determined volumes of the accumulations.
2 . The method according to claim 1 , wherein the step of influencing is carried out in relation to powder material used or for use in the additive layer manufacturing process.
3 . The method according to claim 2 , wherein the step of influencing comprises influencing at least one of delivery of powder material to and spreading of powder material in the work space.
4 . The method according to claim 3 , wherein the step of influencing comprises adjusting a parameter of powder layer formation in the build zone.
5 . The method according to claim 4 , wherein the parameter is a rate of powder material distribution to form the layer.
6 . The method according to claim 1 , comprising the step of comparing the determined at least approximate volume of each accumulation with the given volume of the layer to obtain a measurement of powder material consumption by each layer, wherein the additive layer manufacturing process is influenced as a function of the obtained measurements of powder material consumption.
7 . The method according to claim 6 , wherein the manufacturing process includes delivering to the work space further powder material for use in formation of the successive layers and the step of influencing comprising regulating the delivery as a function of the obtained measurements of powder material consumption.
8 . The method according to claim 7 , wherein the delivery of further powder material is regulated with respect to timing of the delivery.
9 . The method according to claim 7 , wherein the delivery of further powder material is regulated with respect to the amount of further powder material in the delivery.
10 . The method according to claim 9 , comprising determining from the measurements of powder material consumption supplementary amounts of powder material needed to form further such layers.
11 . The method according to claim 10 , wherein the determined supplementary amounts of powder material are also those needed to form further such accumulations.
12 . The method according to claim 1 , wherein the structured light pattern is projected simultaneously onto both a surface of a formed layer of the powder material and an adjoining accumulation of excess powder material left after formation of that layer, an image is produced of the pattern on both the layer surface and the accumulation and the pattern distortion in the image is evaluated to not only determine the volume of the accumulation of excess powder, but also to identify defects in the layer surface.
13 . The method according to claim 12 , wherein the pattern is projected onto the layer surface and the accumulation by a common projecting system and the projected pattern on the layer surface and the accumulation is imaged by a common imaging system.