In order to sufficiently incorporate the HAp fillers into the polymers, the prepared mixtures were subjected to co-rotating twin-screw extrusion. A Thermo Fisher Scientific twin-screw extruder (D = 20 mm, L/D = 40) with special mixing zones was used. The extrusion parameters were selected separately for PLA and PCL based materials due to the significant differences in material properties. PLA-based materials were extruded at a screw speed of 200 rpm and a set temperature of 180 °C across all heating zones. The actual melt temperature ranged from 180°C to 190°C depending on the material type. Pure PCL and PCL-based composites were extruded at a screw speed of 100 rpm with a set temperature of 90 °C in all heating zones and 80 °C at the die head. For the composites, the actual melt temperature exceeded 100 °C. All extrudates were cooled on an air track and then wound onto a winder (Thermo Fisher Scientific). To prepare the extruded materials for further processing, they were regranulated using a Brabender pelletiser.