If a heater instead of a beam source is placed above a powder bed, the radiation from the heater will not converge to a point below the heater on the bed. With an increase in the separation between the heater and the bed, the heat energy density at the point will further decrease. Therefore, if the aim is to melt powder, the heater must be in proximity to the bed, which, however, can damage the heater if not shielded. Though, it can work well with a low melting point material such as polymer, for which less heat-induced risk is involved. A heater needs either to move to cover the whole area or to be present everywhere so the whole area will be under its reach. If the heater needs to move, it reminds the movement of an inkjet printhead that covers the whole area without needing the quality of deflecting a beam. An inkjet printhead consists of a number of ink jets. Thus, if the printhead instead consists of a number of small heaters, it will serve the purpose.