An investigation of rapid prototyping of sand casting molds by selective laser sintering

Among the layer fabrication techniques, selective laser sintering (SLS), is widely used for manufacturing various products made of different materials (i.e., polycarbonates, nylons, polyamides, sand casting, metal powders, and others). The SLS of precoated foundry sands allows the aggregation of adjacent particles, which are then cemented by furnace heat treatment. Moreover, geometrically complex molds and cores not obtainable with conventional methods can be realized by this method. In this article, the optimization of laser parameters is reported for fabricating transitory molds for foundry applications. Lasercron sand, a quartz sand with a thin phenolic resin coating often used for SLS applications, was tested. The CO2 and diode lasers were used for this study. After some preliminary tests, experimental design techniques were applied to investigate the influence of some processing parameters, i.e., laser power, scan speed, and scan spacing (hatch). Their interactions were evaluated using response surface methodology and analysis of variance. The laser irradiation effects on the adhesion between grains and layers, the quality and accuracy of the surfaces, and the sintered thickness were evaluated. The optimum combinations of processing parameters were selected and the operating window was defined. Simple cylindrical-shaped specimens were fabricated as a validation of that window.