Abstract
The metal injection molding process has used metallic filled polymer composite feedstocks for
years to create parts. However, the free complexity and cost effectiveness of fused filament
fabrication has attracted the usage of the same feedstocks in this new process. Changing the
feedstocks to work in this relatively new forming process has proven challenging, as high powder
volumes in the feedstock lead to a highly non-Newtonian and viscoelastic responses in the
composite melt. In past work, the process of creating a new feedstock involved some trial and error
when mixing the different polymers and powder ratios. This work hopes to add predictability to
the feedstock creation process with a focus on how powder loading effects the feedstock system
in the printing process. A polymer binder system was chosen, and several feedstocks were created
that ranged in titanium powder loading from 0 to 60 vol.% Titanium in steps of 10 vol.%. An
additional feedstock was made that contained 65 vol.% Ti, which was the theoretical critical
loading value of spherical particles. All feedstocks and pure binder components had their thermal
characteristics tested using differential scanning calorimetry to observe melting and crystallization
temperatures, thermogravimetric analysis to reveal degradation temperatures, and rheology
analysis to view the dynamic moduli and complex viscosity. This data was used to evaluate
printing trials that were completed with each feedstock. The print tests involved finding the
“optimal” combination of print speed and layer height for each feedstock and performing a
temperature sweep of the feedstocks using set parameters for each feedstock, as temperature most
effects the rheology of a material. The prints created were then tested for surface abnormalities
and proper diffusion of print layers via roughness and tomography, respectively. The outcome is
that a possible correlation connecting powder loading to the rheology and printing results was
made. In addition, a viscosity limit was found and can be used to create new feedstocks that are
below this limit to aid in the part forming process. Ultimately, with future research into this topic,
it is feasible that a titanium filament can be mass produced that will lead to more possibilities in
part creation and an increased adoption of this manufacturing method.
