More than 98% of filaments used for fused filament fabrication (FFF) on 3D printers are produced on single screw extruders; which although being excellent pressure generation and volumetric displacement instruments, are not suitable for producing filaments with a homogenous mixture of fillers, performance improving additives or incompatible materials. A process is presented utilizing an 11mm Co-rotating twin screw extruder which allows one to compound and produce filaments in “one step” for applications like bone grafting, medical implants, recycling and personalized medicine where uniform distribution of additives is critical to performance. A coextrusion method with multiple co-rotating twin screw extruders to produce a filament with distinctly different inner and outer layers is also presented.