POLYMER POWDER OF CONTROLLED PARTICLE SIZE DISTRIBUTION

A powder for use in selective laser sintering, from which prototype articles and masters for molds may be formed, is disclosed. The powder is formed by spray drying a polymer emulsion to yield a distribution of particles of substantially spherical shape. The powder is then air classified to remove excessively small particles from the distribution; the powder may also be screened to remove large particles therefrom, as well. The resulting distribution of particles sizes, by volume, preferably has a mean particle size of between about 20.mu. and about 50.mu., with preferably less than about 5 % (by volume) of its particles with a size of less than about 15.mu. and less than about 2 % (by volume) of its particles with a size of greater than about 75.mu.. The powder is subjected to selective laser sintering to produce an article of approximately 55 % to 75 % of theoretical density. The article may be used as a prototype article or part, or as a pattern or master for a mold.