Obtaining uniform single vectors well attached to the substrate is necessary and sufficient for fabrication of complex-shape parts of high quality by selective laser melting. The temperature distribution in the laser/powder interaction zone and the shape of the melt pool is numerically calculated by the proposed model of coupled radiation and heat transfer applicable to single vectors. The analysis of the capillary stability of the segmental cylinder applied to the calculated melt pool estimates the stability of the process depending on the scanning velocity, powder layer thickness, and the material optical and thermal properties