Two-Dimensional Characterization of Window Contamination in Selective Laser Sintering

Most Laser Sintering machines suffer from an issue where it is hypothesized that hot gases produced during the laser sintering process collect on the Zinc selenide (ZnSe) window separating the build chamber from the environment. This contamination has previously been shown to reduce delivered laser power by up to 10%, and necessitate frequent cleaning and replacement of the windows. A power meter was constructed in order to perform ex-situ measurements of laser attenuation at various locations on the window. Identical builds were performed using fire-retardant nylon 11 on a DTM Sinterstation 2500, and the windows were measured before and after each build. Results indicate that contamination is not uniform on the window, and may cause a variation in laser attenuation up to 3.5%±0.25% depending on scanning location. It is also shown here that the contamination patterns are not repeatable from build to build, even if performed on the same machine.