3-D Printing of Low Density Thermoplastic Materials

Christopher Campbell

Sandia National Laboratories

Current research efforts regarding the production of thermoplastic parts for use as systems components in ND applications are centered around the use of various additive manufacturing (AM) techniques as alternatives to injection molding (IM) for parts used in these applications. Though IM is known to produce void-free high-quality parts due to the high pressures the technique can impart to the molded object, AM techniques are attractive for several reasons including low overhead costs, the ability to produce different complex parts subject to changing design requirements in a short time span, and a lack of contamination from mold-release compounds.
The research presented in this poster will focus on the application of two thermal printing processes, selective laser sintering (SLS) and fused deposition modeling (FDM), toward the production of low density thermoplastic materials. Specifically, three methods were investigated for each of these processes to achieve this goal: 1.) Incorporation of glass microballoons (GMBs) into the thermoplastic feedstock, 2.) using the porosity imparted to the material during the printing process to achieve a target density, and 3.) printing polymethylpentene (PMP) which is a semi-crystalline polymer with a low native density (0.84 g/cm3). Our most significant finding was that although GMB filled thermoplastics were incompatible with milling to produce powders for SLS printing, they performed excellently in FDM printing resulting in printed part densities as low as 0.68 g/cm3 with only 7-8% non-reinforced porosity imparted by this printing technique. Based on this work, we conclude that an attractive avenue toward 3 D printing of low density materials is provided by FDM as this technique inherently contributes a low amount of porosity to the material in addition to the fact that production of the feedstock is amenable to fragile fillers (GMB).

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.