A print-head assembly for effecting fused deposition modelling, comprising of a pair of extruder blocks, each respectively adapted to receive a thermoplastic filament, and respectively extrude the thermoplastic filament such that the thermoplastic filament material is in heat transfer communication with a thermal block. The thermal block including a heating element that serves to heat and increase the temperature of the thermal block to a temperature sufficient to cause phase change of the pair of thermoplastic filaments. The print-head assembly further including a pair of nozzles that are rendered in fluid communication with a respective thermoplastic filament , each nozzle of the pair of nozzles differing in diameter, with the nozzle having a larger diameter being utilized for low accuracy bulk infilling operation and the nozzle having a smaller diameter being utilized for relatively accurate infilling operation.