Additive manufacturing (AM) using metal materials can be used to manufacture metal parts with complex shapes that are difficult to manufacture with subtractive processing. Recently, numerous commercial AM machines for metallic materials have been developed. The primary types of AM using metallic materials are powder bed fusion or direct energy deposition. Other types using metallic materials have not been adequately studied. In this study, the use of the material extrusion (ME) type of AM is investigated. The aim is to use metallic materials not only for fabricating metal parts but also for adding various properties to base materials, e.g., electric conductivity, thermal conductivity, weight, strength, and color of plastics. ME is appropriate for use with various materials by mixing different types of filler. However, there is a problem in that the high density of metal fillers generates unstable extrusion. Therefore, ultrasonic vibration was used for assisting extrusion. A prototype system was developed using an extrusion nozzle vibrated by an ultrasonic homogenizer. The experimental results showed that the ultrasonic vibration allows materials to be extruded smoothly. Three dimensional (3D) shapes could be built by multi-layer deposition with a thixotropic polymer containing a highly concentrated steel powder. As one application, a 3D-shaped object was fabricated as a sintered object. After the vibration effect in the extrusion process of steel powder and clay was confirmed, a 3D object built by the proposed method was sintered through a baking process.

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