A continuous filament additive manufacturing machine for building a part by laying down a continuous mono-filament or composite filament material layer by layer on a tool or substrate. The machine includes a system, such as a robot, operable to move in three degrees of freedom, and a placement module coupled to the system and being configured to deposit the continuous filament material. The placement module includes a guide for guiding the material to the part and an ultrasonic compaction device for compacting the material as it is being deposited from the placement module. The compaction device includes an ultrasonic horn having at least one guide hole through which the material passes before it is laid down and compacted. The ultrasonic horn is ultrasonically vibrated to melt or flow the material and cause the material to fuse and be compacted to the tool or substrate.