Laser debinding of parts produced through material extrusion additive manufacturing

Abstract

A novel cost effective material extrusion additive manufacturing method for metals and ceramics employs filaments embedded with powdered granules which are shaped, debinded, and sintered sequentially until completion of the part. One well known drawback of the technology lies in the time-consuming debinding process, which often requires handling toxic agents (e.g. acetone, cyclohexane, nitric or oxalic acids), as well as complex heating profiles. Debinding is traditionally done after shaping the part, and little investigation has been made to develop the technology to debind locally, in situ, without the use of toxic consumables. Here, we show that full debinding can be achieved efficiently on the bulk of the printed part through an application of local energy by applying it selectively on the top surface, layer by layer, along the 3D volume of as built green parts. A low intensity infra-red laser is integrated in a custom-built machine to create a hybrid device that combines traditional filament extrusion additive manufacturing with in-situ debinding. The results show that the main binder matrix of a Highly Filled (HF) commercially available stainless steel 316L filament can be removed efficiently along the full volume of the part via laser ablation of the organic mass. Defects, surface roughness and topography deviations can be minimized compared to other traditional thermal debinding methods, further showcasing the capability of building consecutive layers on top of a previously debinded layer. We report improvements in debinding time by a magnitude of 248 % compared to traditional thermal debinding, of 595 % compared to solvent debinding at 45 °C, and 943 % compared to solvent debinding at room temperature. The effect of debinding with the use of lasers in-situ, layer by layer, and the effect in the layer adhesion of fully debinded parts, is investigated through optical and electron microscopy, as well as quantifying the binder mass loss. Debinding in-situ offers new routes to reduce processing times of parts produced through FFF.