Particle shape and layer density
Assuming a similar composition, literature shows the non-negligible impact of particles’ physical characteristics such as size, shape and size distribution on the finished components. For instance, aluminium particles’ shape influences how much oxidation each particle can readily pick up . In addition to non-uniform illumination, non-uniform oxides distribution generates 1) non-uniform particle melting and 2) pores. This is undesirable for the development of multiple layer parts. In contrast, SLS/SLM processing of aluminium powders with spherically shaped particles results in the formation of a homogeneous and dense layer . They facilitate high layer packing density since they exhibit low interparticle friction and high mobility .
Particle size and size distribution
Investigating readily available powders, Karapatis  found that critical criteria are D10, D50 and D90. D10 represents the particle diameter corresponding to 10% cumulative (from 0 to 100%) undersize particle size distribution. In other words, if particle size D10 is 7.8um, we can say 10% of the particles in the tested sample are smaller than 7.8 micrometer, or the percentage of particles smaller than 7.8 micrometer is 10%.
- D10 < layer thickness; ie 10% of the particles are smaller than the layer thickness;
- D90 < layer thickness, ie 90% of the particles are smaller than the layer thickness;
- D50 ≥ 10×D10, ie 50% of the particles are 10 times coarser than the 10% finer grains;
- D90 ≤ 19×D10, ie the coarsest particles are in a 1:19 ratio with finer particles.
 I. Chang and Y. Zhao, Advances in Powder Metallurgy - Properties, Processing and Applications. Woodhead Publishing, 2013.
 E. O. Olakanmi, “Selective laser sintering/melting (SLS/SLM) of pure Al, Al–Mg, and Al–Si powders: Effect of processing conditions and powder properties,” J. Mater. Process. Technol., vol. 213, no. 8, pp. 1387–1405, Aug. 2013.
 N. P. Karapatis, G. Egger, P. Gygax, and R. Glardon, “Optimization of Powder Layer Density in Selective Laser Sintering,” in Proc. Of the 9th Solid Freeform Fabrication Symposium, 1999, pp. 255–264.
 E. Louvis, P. Fox, and C. J. Sutcliffe, “Selective laser melting of aluminium components,” J. Mater. Process. Technol., vol. 211, no. 2, pp. 275–284, Feb. 2011.
 R. K. Mcgeary, “Mechanical Packing,” J. Am. Ceram. Soc., vol. 58, no. 1931, 1955.
 R. M. German and S. J. Park, Mathematical relations in particulate materials processing. John Wiley & Sons, Inc, 2008, p. 419.
 P. Karapatis, “A sub-process approach of selective laser sintering,” Ecole Polytechnique Federale de Lausanne, 2002.