Temperature history within laser sintered part cakes and its influence on process quality

Abstract

Purpose The temperature distribution and history within laser sintered part cakes is an important aspect regarding the process quality and reproducibility of the polymer laser sintering process. This paper aims to an analysis of the temperature history during the build and cooling phase, which is decisive for powder ageing effects and the development of part quality characteristics. Design/methodology/approach A measurement system for three-dimensional in-process temperature measurements is set up and the influence of different parameters on the inner part cake temperature distribution and history is analyzed. In addition, position dependent temperature histories are finally correlated with powder ageing effects. Findings The main parameters influencing the part cake temperature history are figured out. Temperature inhomogeneities on the powder bed surface are detectable within the part cake, but only for a specific time or additional build height. Heat flux through the build frame results in different cooling rates dependent on z height. A combination of process parameters and build job layout results in individual, position-dependent temperature histories. As a consequence, completely different ageing intensities are found within one part cake. Research limitations/implications Temperature measurements are limited to part-free powder cakes so far. To transfer the results to other boundary conditions and machine types, simulation tools have to be developed and validated. Originality/value For the first time, the inner part cake temperature distribution and history have been measured during all build phases and with a high sensor density. The results of this work help to understand the temperature history dependency of powder and part properties and can therefore be used to develop optimized process controls.