Temperature-Controlled Selective Laser Sintering

A control scheme for laser sintering has been developed which maintains sintering powder at constant temperature by actively controlling laser power. It uses a sensor to monitor the temperature of powder at the focus of a moving laser beam. The control scheme corrects for variations ofthermal conductivity and powder reflectivity due to the proximity of previously sintered material, as well as for statistical fluctuations. The sensor also serves as a useful diagnostic, and is used to confirm model predictions ofthe variation of powder temperature with process parameters. A second temperature-controlled laser beam, concentric with the first, but of larger spot size, can be used to locally heat the powder around the sintering powder. This is shown to reduce curling as well as the balling or agglomeration of molten material