Rapid Prototyping Journal, Volume 21, Issue 1, January 2015.
Purpose The purpose of this paper is to analyze the bulk energy transport processes in the build chamber environment before and during laser sintering (LS) to provide a basis for effective and accurate thermal control for LS process. This leads to improved mechanical properties and geometrical tolerances for LS products and may be applied to optimize operation cycle times for the LS process. Design/methodology/approach Computational models with two levels of complexity were built to explore the heat transfer mechanisms in the LS process. In a 1D model, the powder performed as a semi-infinite solid and heater flux to the powder surface was modeled with a heater control law. A 2D fluid/solid finite-element model of the build chamber and powder bins provided insight into the thermal processes in the build chamber. Findings Numerical 1D simulations were verified with measurements from sensors embedded in the build chamber powder bed. Using a 2D model, computed powder surface temperatures during the warm up and build phases were verified with an infrared camera. Convective currents in the build chamber and non-uniformities in the distribution of temperature over the radiant heater surface were found to be substantial contributors to non-uniformities in powder bed surface temperature. Research limitations/implications Limited heat sources were analyzed. No 3D model was built. Assumptions to decrease the part bed temperature difference were not tested. Originality/value These simulation and experimental results may be used to enhance thermal control and operation efficiency during the LS process and to improve LS product mechanical properties.
Purpose The purpose of this paper is to analyze the bulk energy transport processes in the build chamber environment before and during laser sintering (LS) to provide a basis for effective and accurate thermal control for LS process. This leads to improved mechanical properties and geometrical tolerances for LS products and may be applied to optimize operation cycle times for the LS process. Design/methodology/approach Computational models with two levels of complexity were built to explore the heat transfer mechanisms in the LS process. In a 1D model, the powder performed as a semi-infinite solid and heater flux to the powder surface was modeled with a heater control law. A 2D fluid/solid finite-element model of the build chamber and powder bins provided insight into the thermal processes in the build chamber. Findings Numerical 1D simulations were verified with measurements from sensors embedded in the build chamber powder bed. Using a 2D model, computed powder surface temperatures during the warm up and build phases were verified with an infrared camera. Convective currents in the build chamber and non-uniformities in the distribution of temperature over the radiant heater surface were found to be substantial contributors to non-uniformities in powder bed surface temperature. Research limitations/implications Limited heat sources were analyzed. No 3D model was built. Assumptions to decrease the part bed temperature difference were not tested. Originality/value These simulation and experimental results may be used to enhance thermal control and operation efficiency during the LS process and to improve LS product mechanical properties.