Extruder for metal material and 3D printer using the same

An extruder for a metal material, the extruder comprising:

• a cylinder having a receiving space in which a solid metal material is provided;
• a nozzle extending from a lower end of the cylinder;
• an upper coil comprising a first coil and a second coil, the first coil surrounding an upper portion of an outer surface of the cylinder and the second oil surrounding a lower portion of the outer surface of the cylinder, wherein the first coil and the second coil produce a first magnetic field and a second magnetic field passing through the cylinder and are configured to melt the solid metal material provided inside the cylinder to form a liquid metal material;
• and
• a lower coil comprising a third coil and a fourth coil, the third coil surrounding an outer surface of the nozzle, and the fourth coil directly surrounding the third coil, wherein the third coil is provided between the fourth coil and the nozzle, and the fourth coil is provided at an equal height as the third coil and the nozzle,
• wherein the third coil produces a coil third magnetic field passing through the nozzle and is configured to control an extruded shape of the liquid metal material inside the nozzle,
• wherein the fourth coil produces a fourth magnetic field passing through an extruded metal material to induction-heat the extruded metal material.