The normal spectral absorptance of a number of metal, ceramic and polymer powders susceptible to be utilised for selective laser sintering (SLS) technique was experimentally determined. The measurements were performed with two laser wavelengths of 1.06μm and 10.6μm obtained by using two lasers – Nd‐YAG and CO2 respectively. The change in the powder absorptance with time during laser processing was also investigated. The effect of the absorptance characteristics on the sintering process is discussed.

The particularities of the selective laser processing of singlecomponent metal powder layers were investigated, especially the occurrence of the balling-processes under different processing conditions. During laser processing, sintered, semi-sintered/semi-melted or completely melted cakes can be formed. Size and shape of the laser processed parts can change depending on the energy and time parameters of the laser irradiation and on the properties of initial powder layers.

This paper discusses how the estimation of the temperature field in the powder bed in selective laser sintering is a key issue for understanding sintering/binding mechanisms and for process optimisation. Carried out within a European research project, funded by INTAS (No. 99-1559, 2000-02), a model of independent small thermal contacts to calculate the effective contact conductivity in Ti powder bed was developed. This paper won the Emerald Literati Awards' Outstanding Paper 2004 (http://www.emeraldinsight.com/literaticlub/winners).Coupled metallographic examination and heat transfer numerical simulation are applied to reveal the laser sintering mechanisms of Ti powder of 63-315?µm particle diameter. A Nd:YAG laser beam with a diameter of 2.7-5.3?mm and a power of 10-100?W is focused on a bed of loose Ti powder for 10?s in vacuum. The numerical simulation indicates that a nearly hemispherical temperature front propagates from the laser spot. In the region of a-Ti just behind the front, heat transfer is governed by thermal radiation. The balling effect, formation of melt droplets, is not observed because the temperature increases gradually and the melt appears inside initially sintered powder which resists the surface tension of the melt. (Emerald Publishing Group Limited