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.