Radiation source assembly and apparatus for layer-by-layer formation of three-dimensional objects

A method for operating an apparatus to manufacture a three-dimensional object from a particulate material, the apparatus comprising a build bed surface of particulate material, and one or more radiation source assemblies for pre-heating and/or for consolidating particulate material on the build bed surface, the or each radiation source assembly comprising:

• a plurality of light-emitting diodes arranged in an array spanning the width of the build bed surface and comprising a plurality of individually addressable groups, each light-emitting diode being operable to emit a respective beam of radiation towards the build bed surface;
• and
• one or more collimators, arranged to collimate the beams of radiation of the plurality of light-emitting diodes to produce one or more collimated beams of radiation, and to direct said collimated beams of radiation towards the particulate material on the build bed surface;
• wherein the method comprises at least one of the steps of:
• moving the radiation source assembly across the build bed surface while operating one or more of the plurality of light-emitting diodes so as to preheat the particulate material;
• and/or
• depositing a radiation absorbent material (RAM) onto a layer of particulate material on the build bed surface by moving one or more droplet deposition heads across the build bed surface;
• and/or
• consolidating the particulate material in the layer where the RAM has been deposited by moving the or a further radiation source assembly across the build bed surface while operating one or more of the plurality of light-emitting diodes.