Effects of graphite powder on the laser sintering behaviour of polycarbonate

A non-contact infrared temperature sensor was used to monitor the temperature-time relation of a point on the powder bed during laser sintering. The results were translated into a temperature-distance relation of the monitored spot with respect to its distance from the laser beam. The effect of particle size of polycarbonate (PC) powder on the temperature-distance relation was studied. The maximum temperature attained at the monitored spot was found to increase with decreasing size of the PC particles. The phenomenon was probably caused by the higher packing density of the smaller particles, and more laser energy was absorbed near the powder bed surface. The temperature-distance relations of some common additives such as graphite, quartz, silica and talc were also studied, and graphite was found to give the highest temperature distribution. PC/graphite composite powders were blended and sintered under similar conditions. The surface temperature of the powder bed increased greatly with the addition of a small amount (up to 2 per cent) of graphite powder. The result was attributed to the higher absorptance of CO 2 laser energy by the graphite powder.