Résumé
Selective laser sintering is a layer-by-layer process that allows complex shapes to be processed butrequires specific properties for the powder used to build the final object. The advantages of freecrucible processing and freedom of design makes this process interesting for several applications.Despite the large number of SLS printer available in the market, a deep understanding of the physicalphenomena of this process is still lacking, due to the number of parameters involved, directlyinfluencing the final part’s properties through the microstructure. In this work, glass beads or talc wereadded to Polyamide 12 (PA 12) matrix in order to evaluate these filler’s influence on powder bed. Westarted with PA 12 and glass beads (PA90/GB10 in wt%) untill 70/30 wt%, with a 5 wt% increment. AsSLS operates with CO2 laser working at 10.6μm to melt powders, it is fundamental to investigate howheat will be conducted through the different sintered layer. Various parameters can influence thermalconductivity of filled Polyamide 12 powder bed such as particle shape, aspect ratio, chemicalcomposition, presence of impurities and also the packing of the particles from powder bed. Hence,porosity is such an important parameter as air inside is highly insulating the material and reduces itsthermal conductivity by convection between pores. This convection is also governed by the pores size.(Rayleigh criterion) Several experiments were carried out in order to evaluate the thermal conductivityas a function of porosity which highly depends on how particles are settled, thus how the powder bedis tapped. These results were obtained using a hot wire conductivity meter from Neotim which cangive thermal conductivity through a powder bed. To determine samples porosity, we used a powdertester which returned powder densities for different tapping levels. As we are working with filledpolyamide 12 matrix, a huge drop of flowability has to be considered upon addition of filler whichcan cause issues during the process. Changes of processing parameters could be required due tosignificant modifications of the thermal behavior resulting from the presence of fillers.