System and method for controlling flow through a 3D printer

A 3D printer, comprising:

• an ejector configured to receive a build material, wherein the ejector comprises a nozzle that is configured to eject the build material therefrom, and wherein the build material comprises metal;
• a valve positioned upstream from the nozzle, wherein the valve is configured to control flow of the build material into or through the ejector, wherein the valve comprises:
• a body having an inlet, an outlet, and a narrow portion between the inlet and the outlet, wherein a diameter of the narrow portion is smaller than a diameter of the inlet, the outlet, or both;
• a cooler positioned at least partially around the narrow portion, wherein the cooler is configured to cool the build material to below a melting point of the build material to form a solid plug within the body to prevent the build material from flowing therethrough;
• and
• a heater positioned radially inward or radially outward from the cooler, wherein the heater is configured to re-heat the build material to above the melting point to allow the build material to flow therethrough;
• and
• a substrate positioned below the nozzle, wherein the build material lands on the substrate and cools and solidifies thereon to form a 3D object.

A method for controlling a flow of a build material through a 3D printer, the method comprising:

• actuating a valve into a closed position to prevent the build material from flowing into or through an ejector of the 3D printer, wherein the valve comprises a cooler positioned at least partially around the build material, wherein actuating the valve into the closed position comprises cooling the build material to below a melting point of the build material using the cooler to form a solid plug to prevent the build material from flowing therethrough;
• actuating the valve into an open position to permit the build material to flow into or through the ejector, wherein the valve also comprises a heater positioned radially inward or radially outward from the cooler, and wherein actuating the valve into the open position comprises re-heating the build material to above the melting point of the material using the heater to allow the build material to flow therethrough;
• and
• ejecting a drop of the build material through a nozzle of the ejector onto a substrate, wherein the drop cools and solidifies thereon to form a 3D object.