Abstract: A powder bed fusion apparatus arranged to irradiate a powder bed using a charged particle beam is provided, the apparatus comprising a neutralising particle source operable to provide neutralising particles of an opposite charge to the charged particle beam, and a neutralising particle focusing system arranged to weakly focus a beam of the neutralising particles from the neutralising particle source on to the powder bed in the vicinity of the irradiation position of the charged particle beam on the powder, such that the neutralising particles neutralise charging of the powder bed by the charged particle beam. A method of additive manufacture using a powder bed fusion apparatus is also provided, wherein a part is formed as a series of layers, each layer being formed by scanning the charged particle beam over a layer of the powder bed to melt the powder according to a predetermined pattern.

Abstract: A method of additive layer manufacture includes the steps of successively depositing layers of fusible powder material in overlying relationship and introducing energy, such as by an electron beam, into each deposited layer to selectively melt material in the layer so as to fuse the melted material together and to already fused material of a layer thereunder in order to produce a three-dimensional solid article in successive cross-sectional layers. In order to monitor layer quality, structured light defining a fringe pattern is projected onto each deposited layer before and/or after melting of material in that layer and the fringe pattern on each layer is imaged from a perspective different from that of the projection so as to reveal disturbance of the pattern by topographical features of the layer.

Abstract: A method of charge mitigation in additive layer manufacturing is provided, which uses a charged particle beam (103) to fuse metal powder (122) within a metal powder bed (123) to form a product layer-by-layer, the method comprising using a charged particle beam optical system to form a charged particle beam, to steer the charged particle beam to be incident on a powder bed of metal powder and to scan over the powder bed to fuse powder into a desired layer shape. While steering the charged particle beam, the method comprises using a neutralising particle source (160) to generate neutralising particles of an opposite charge to the charged particles in the vicinity of the charged particle beam such that the neutralising particles are attracted to the charged particles of powder in the powder bed. An additive layer manufacturing apparatus (100) is also provided.

Abstract: A method of forming a product using additive layer manufacture is provided. The method comprises forming the product as a series of layers, each layer being formed by fusing powder deposited as a powder bed by scanning the powder bed using a charged particle beam to form a desired layer shape. For each layer, the powder is fused by melting successive areas of the powder bed by scanning the charged particle beam using a combination of a relatively long-range deflector and a relatively short-range deflector, wherein the relatively long-range deflector deflects the charged particle beam over a larger deflection angle than the short-range deflector. Also provided are a corresponding charged particle optical assembly, and an additive layer manufacturing apparatus.

Abstract: A method of additive layer manufacture includes the steps of successively depositing layers of fusible powder material in overlying relationship and introducing energy, such as by an electron beam, into each deposited layer to selectively melt material in the layer so as to fuse the melted material together and to already fused material of a layer thereunder in order to produce a three dimensional solid article in successive cross-sectional layers. In order to monitor layer quality, structured light defining a fringe pattern is projected onto each deposited layer before and/or after melting of material in that layer and the fringe pattern on each layer is imaged from a perspective different from that of the projection so as to reveal disturbance of the pattern by topographical features of the layer.

Abstract: A method of charge mitigation in additive layer manufacturing is provided, which uses a charged particle beam (103) to fuse metal powder (122) within a metal powder bed (123) to form a product layer-by-layer, the method comprising using a charged particle beam optical system to form a charged particle beam, to steer the charged particle beam to be incident on a powder bed of metal powder and to scan over the powder bed to fuse powder into a desired layer shape. While steering the charged particle beam, the method comprises using a neutralising particle source (160) to generate neutralising particles of an opposite charge to the charged particles in the vicinity of the charged particle beam such that the neutralising particles are attracted to the charged particles of powder in the powder bed. An additive layer manufacturing apparatus (100) is also provided.

Abstract: A method of forming a product using additive layer manufacture is provided. The method comprises forming the product as a series of layers, each layer being formed by fusing powder deposited as a powder bed by scanning the powder bed using a charged particle beam to form a desired layer shape. For each layer, the powder is fused by melting successive areas of the powder bed by scanning the charged particle beam using a combination of a relatively long-range deflector and a relatively short-range deflector, wherein the relatively long-range deflector deflects the charged particle beam over a larger deflection angle than the short-range deflector. Also provided are a corresponding charged particle optical assembly, and an additive layer manufacturing apparatus.

Abstract: A method of producing an array of islands (12) on concentric tracks (13) on a rotating substrate by selective exposure of an electron-sensitive surface of the substrate to an electron beam comprises directing the beam onto a point (A) on the surface within a zone of action of the beam and deflecting the beam in the sense (31) of substrate rotation to remain on the point until the point (A?) has received an electron dose from the beam. The beam is then redirected onto a further point (B or T) at a spacing from the preceding point (A?) and dosed by the beam in similar manner. The redirection and deflection procedure is repeated for at least one substrate revolution, preferably several revolutions, so that points are dosed along at least one of the tracks (13a), preferably several of the tracks (13a to 13j).