A three-dimensional (3D) printer includes a heated printing surface and a multi-tool extrusion assembly. The multi-tool extrusion assembly includes a barrier extrusion assembly and a metal extrusion assembly. The barrier extrusion assembly includes: a first inlet adapter to receive a barrier material; a first torque-and-pinch assembly, coupled to the first inlet adapter, to receive the barrier material; and a first hot-end assembly, coupled to the first torque-and-pinch assembly, to receive the barrier material and extrude the barrier material to form an outer retaining barrier on the heated printing surface. The metal extrusion assembly includes: a second inlet adapter to receive a metal; a second torque-and-pinch assembly, coupled to the second inlet adaptor, to receive the metal; and a second hot-end assembly, coupled to the second torque-and-pinch assembly, to extrude the metal to form an inner metal filing on the heated printed surface within the outer retaining barrier.