Abstract: A fused filament fabrication printer has a fixed extrusion module having multiple printheads having print tips. The fixed arrangement of the printing heads allows the close spacing of multiple print tips in a printhead unit, and the simple routing of multiple plastic or metal filaments to the individual printing heads. The closely spaced print tips in the printhead unit share common components. An exemplary printhead unit has four printing heads which share a common heating block and heating block temperature sensor. The heating block incorporates a group of four print tips evenly spaced along a line. Each printing head has a separate filament which is controlled and driven by its own stepper motor through the heating block to one of the print tips. Printing of a part is by control of individual stepper motors which drive filaments through the heating block and through one of the printing tips.