Experimental parameter identification for part-scale thermal modeling of selective laser sintering of PA12

Abstract

Thermal management is a critical issue for Selective Laser Sintering (SLS) of polymers, as the thermal history within the powder bed has a significant impact on the produced part quality. Numerical simulations can calculate the thermal history of a build, as well as residual stress, distortion, lack of fusion, and powder aging effects. Model parameters including heat input from the laser and IR heaters, and the thermal boundary conditions on the model surfaces, are needed to perform a physics based SLS part-scale simulation. In this work, specially designed in situ thermal monitoring experiments are performed at The University of Texas at Austin (UT-Austin) for parameter identification in the development of a part-scale thermal model of the SLS process. The machine has PID controlled heating units in the build box and build chamber, and is also equipped with a high-speed thermal camera to monitor and control the build surface temperature. A series of high temperature plastic tubes with thermocouples attached were inserted into the powder bed to provide in situ volumetric temperature monitoring during the preheating, building, and cooling phases of the SLS process. High-speed thermal imaging data and thermocouple readings are presented to provide insight into the thermal response and to identify the heat input for the thermal model. A convection coefficient value of 10 W/m2/∘C is identified for all surfaces in the model by a post-process heating experiment. The power input of the laser and the IR heater are in situ measured and applied as an activation temperature of the material in the model to simulate the heat input. The thermal model can simulate the thermal history of the SLS process with average error within 11%.