A method of forming 3d objects

A method for forming a 3D object, comprising running a computerised controller with reference to data which defines 3D shape parameters of an object in terms of notional slices such that the controller:

• uses the data to control an applicator to spray material comprising metallic powder at a substrate, and then at the object when part-formed, in adjacent lines to build the object out of progressively applied layers corresponding to the slices, wherein at least some of the layers have an initial inwardly tapered outer surface;
• and
• for at least some such layers causing the controller to use the data to cause the applicator to be spray perpendicular to the taper to fill in the taper.