Pneumatic jetting of metal for additive manufacturing
Devices, systems, and methods are directed to the pneumatic ejection of liquid metal from a nozzle moving along a controlled three-dimensional pattern to fabricate a three-dimensional object through additive manufacturing. The metal is movable into the nozzle as a valve is actuated to control movement of pressurized gas into the nozzle. Such movement of metal into the valve as pressurized gas is being moved into the nozzle to create an ejection force on liquid metal in the nozzle can reduce or eliminate the need to replenish a supply of the metal in the nozzle and, therefore can facilitate continuous or substantially continuous liquid metal ejection for the fabrication of parts.
1. A system for pneumatically jetting liquid metal, comprising:
a nozzle defining a volume and including an open discharge orifice;
a media source configured to deliver metal to the volume of the nozzle;
a heater configured to heat the metal such that the metal that exits the discharge orifice is liquid metal from a meniscus of liquid metal formed at the open discharge orifice;
a source of pressurized gas in fluid communication with the volume of the nozzle through a first port;
a first valve configured to selectively permit flow of pressurized gas from the source of pressurized gas to the volume of the nozzle through the first port;
wherein when the first valve is in a first position pressurized gas flows to the volume of the nozzle such that a pneumatic force is exerted on the liquid metal in the volume of the nozzle so as to eject an amount of liquid metal through the discharge orifice; and
wherein when the first valve is in a second position the flow of pressured gas to the volume of the nozzle is interrupted such that ejection of the liquid metal is interrupted.
2. The system for pneumatically jetting liquid metal of claim 1 , further comprising a second port in fluid communication with the volume of the nozzle and configured to, when the first valve is in the second position, vent the pressurized gas from the volume of the nozzle to an environment having a lower pressure than a pressure in the volume of the nozzle.
3. The system for pneumatically jetting liquid metal of claim 1 , wherein the nozzle includes at least one baffle disposed in the volume of the nozzle and oriented to direct sediment in the liquid metal toward a reservoir portion of the volume of the nozzle.
4. The system for pneumatically jetting liquid metal of claim 3 , wherein the at least one baffle is a plurality of parallel baffles.
5. The system for pneumatically jetting liquid metal of claim 2 further comprising a source of hydraulic inertance having a resistance that dissipates in the presence of a continuous flow of pressurized gas from the volume of the nozzle to the environment having a lower pressure.
6. The system for pneumatically jetting liquid metal of claim 2 further comprising a source of variable hydraulic impedance disposed between the volume of the nozzle and the environment having a lower pressure.
7. The system for pneumatically jetting liquid metal of claim 1 further comprising:
an electric power source configured to apply an electric current to intersect a magnetic field extending through the liquid metal whereby a magnetohydrodynamic force ejects the liquid metal from the discharge orifice.
8. The system for pneumatically jetting liquid metal of claim 7 further comprising a controller configured to cause pneumatic jetting of the liquid metal in a first area designated as requiring high accuracy and configured to cause magnetohydrodynamic jetting of the liquid metal in a second area designated as a requiring low accuracy.
9. A method of pneumatically jetting liquid metal, comprising:
delivering metal from a media source to a volume of a nozzle, the nozzle including an open discharge orifice;
heating the metal such that the metal that exits the discharge orifice is liquid metal from a meniscus of liquid metal formed at the open discharge orifice;
providing a source of pressurized gas in fluid communication with the volume of the nozzle via a first port;
operating a first valve to permit pressurized gas to flow from the source of pressurized gas to the volume of the nozzle such that a pneumatic force is exerted on the liquid metal in the volume of the nozzle so as to eject an amount of liquid metal through the discharge orifice; and
operating the first valve to interrupt the flow of pressured gas to the volume of the nozzle such that ejection of the liquid metal is interrupted.
10. The method of pneumatically jetting liquid metal of claim 9 , further comprising the step of:
when the first valve is in the second position, venting the pressurized gas from the volume of the nozzle through a second port to an environment having a lower pressure than a pressure in the volume of the nozzle.
11. The method of pneumatically jetting liquid metal of claim 9 wherein the nozzle includes at least one baffle disposed in the volume of the nozzle and oriented to direct sediment in the liquid metal toward a reservoir portion of the volume of the nozzle.
12. The method of pneumatically jetting liquid metal of claim 11 , wherein the at least one baffle is a plurality of parallel baffles.
13. The method of pneumatically jetting liquid metal of claim 10 wherein a source of hydraulic inertance has a resistance that dissipates in the presence of a continuous flow of pressurized gas from the volume of the nozzle to the environment having a lower pressure.
14. The system for pneumatically jetting liquid metal of claim 10 wherein a source of variable hydraulic impedance disposed between the volume of the nozzle and the environment having a lower pressure.
15. The method of pneumatically jetting liquid metal of claim 9 , further comprising the step of:
applying an electric current to intersect a magnetic field extending through the liquid metal whereby a magnetohydrodynamic force ejects the liquid metal from the discharge orifice.
16. The method of pneumatically jetting liquid metal of claim 15 wherein a controller is configured to cause pneumatic jetting of the liquid metal in a first area designated as requiring high accuracy and configured to cause magnetohydrodynamic jetting of the liquid metal in a second area designated as a requiring low accuracy.
17. A liquid metal jetting printer for fabricating a three-dimensional object according to a three-dimensional model, comprising:
a build chamber enclosing a build plate, a nozzle and robotics configured to movably position the build plate and the nozzle with respect to one another;
the nozzle defining a volume and including a first port, a second port and an open discharge orifice;
a source of pressured gas in fluid communication with the volume of the nozzle;
a valve configured to selectively allow and interrupt movement of pressured gas from the source of pressurized gas to the volume of the nozzle;
a media source including a drive train configured to feed metal through a heater to the discharge orifice of the nozzle;
a control system configured to cause the robotics to move the build plate and nozzle with respect to one another and selectively operate the valve to control the pneumatic ejection of liquid metal, from a meniscus of liquid metal formed on the open discharge orifice, to form a three-dimensional pattern according to the three-dimensional model.
18. The liquid metal jetting printer of claim 17 further comprising at least one of a baffle, a source of hydraulic inertance, a source of hydraulic impedance and an electrical power source configured to create a magnetohydrodynamic force to eject liquid metal from the discharge orifice of the nozzle.