Inhomogeneous Shrinkage of Polymer Materials in Selective Laser Sintering 298

It is well known that the laser beam of an SLS machine can be controlled almost exactly. The inaccuracy of the mechanical movements of the machines is also much lower than the actual errors of the SLS parts. How can we explain this discrepancy? One answer is the temperature inhomogeneity in the build field and in the part bed. In this article the effect of temperature dependent volume relaxation of pre-sintered polymer parts on the inaccuracy of the SLS process will be discussed. The investigation shows that it depends on the temperature, pressure and time. Measurements of the temperature distribution in an SLS part bed were carried out. By determining coordinate-dependent scaling factors, an empirical method to compensate this nonlinear shrinkage is presented in this article.