A joule heating mechanism for high-speed fused filament fabrication

Abstract

Extrusion-based additive manufacturing, known as fused filament fabrication (FFF), is one the most accessible methods of rapid prototyping, capable of handling a wide variety of engineering thermoplastics. Productivity limitations hinder the further application of FFF to both prototyping and production. An FFF system consists of three synchronized processes: heat conduction into the feedstock, gantry speed, and extrusion of the feedstock by a pinch wheel mechanism. Each one of these processes can become a rate-limiting factor for prints. This work explores resistive joule heating as a method to increase heat transfer into an electrically conductive composite feedstock. This requires usage of an electrically insulating liquefier in order to co-locate both conduction and joule heating. A prototype mechanism was designed and fabricated including an anodized aluminum liquefier capable of printing. This was tested and no significant difference in print times were noted because of a failure in the system due to a current jump around the joule heating section. Although physical tests were not a success, a LabVIEW VI was created for future testing. In addition, modeling was performed to conclude that a 2.85mm PLA filament would be used in the range of 80-100V and 0.2-0.25A with a joule heating length of 0.75cm in the system in order to reach an extrusion rate of 200 cm³ /hr.