Optimizing directed energy deposition of polymers through melt pool temperature control: impact on physical properties of polyamide 12 parts

Abstract

The method of Directed Energy Deposition of polymers (DED-LB/P) was extended to allow control over the melt pool temperature using a pyrometer. DED-LB/P was used to build test specimen of polyamide 12 (PA12), orthogonal and parallel to the long side. Samples prepared under temperature control show superior mechanical properties over those generated without. The temperature of the melt pool allows to tune the quality of the built part. A too low temperature leads to a porous part on account of insufficient powder fusion, and a too high temperature leads to holes by formation of volatiles. The mechanical properties can be related to the porosity, the molecular mass of PA12 did not change substantially, the distribution width however increased with temperature. The best processing conditions were at 220 °C leading to a build part with a porosity of 0.6%, a Youngs modulus of 550 MPa and a fracture-strain of 15% with an ultimate strength of almost 28 MPa.