US Patent 11760016 Build material particle layering

According to an example, an apparatus may include a recoater, an energy source, a carriage supporting the energy source, and a controller. The controller may control the recoater to spread build material particles into a layer on top of a previously applied layer containing fused build material particles and the carriage to move ahead of the recoater to cause the energy source to apply energy onto build material particles in the previously applied layer prior to the recoater spreading the build material particles onto the previously applied layer. The energy source is to heat the fused build material particles to or maintain the fused build material particles at a temperature above a certain temperature and the recoater is to be controlled to spread the build material particles on top of the previously applied layer prior to the fused build material particles falling below the certain temperature.