The thermal behaviour of resin coated sands for selective laser sintering

Selective Laser Sintering (SLS) of resin coated silica sands is a promising technology for shell-mould casting fabrication. In the scientific literature a deep lack of information is present about this subject. Several aspects have to be studied to correctly analyse this process: the initial sand properties, the contact area among grains, the thermal conductivity dependence on thermal history and the pre-heating effect during hardening. These aspects are discussed by the authors in the current paper and are fundamental for the definition of a new SLS procedure to produce consolidated components directly by a diode laser, without any further oven treatment. Sand hardening depends on several mechanisms: the coating resin flow, its cure and thermal degradation. Best results in terms of mechanical properties of sand components can be obtained if sufficient time is given for resin flow before the cure initiation, without generating the thermal degradation. The pre-heating phase plays a central role for sand agglomeration and has to be correctly taken into account during laser sintering to avoid thermal degradation.