MAGNETOHYDRODYNAMIC DEPOSITION OF METAL IN MANUFACTURING

• US 20170252821A1
• Filed: 03/06/2017
• Published: 09/07/2017
• Est. Priority Date: 03/03/2016
• Status: Active Grant

• Current Assignee: Desktop Metal, Inc.
• Original Assignee: Desktop Metal, Inc.
• Inventors: Sachs, Emanuel Michael, Gibson, Mark Gardner, Hoisington, Paul A., Fontana, Richard Remo
• Granted Patent: US 10,201,854 B2
• Time in Patent Office: Days
• CPC Class Codes: B05B 5/025 Discharge apparatus, e.g. electrostatic spray guns
• CPC Class Codes: B22F 10/00 Additive manufacturing of workpieces or articles from metallic powder apparatus or devices therefor B22F12/00
• CPC Class Codes: B22F 10/22 Direct deposition of molten metal
• CPC Class Codes: B22F 10/32 of the atmosphere, e.g. composition or pressure in a building chamber
• CPC Class Codes: B22F 10/38 to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
• CPC Class Codes: B22F 12/10 Auxiliary heating means
• CPC Class Codes: B22F 12/17 to heat the build chamber or platform
• CPC Class Codes: B22F 12/20 Cooling means
• CPC Class Codes: B22F 12/53 Nozzles
• CPC Class Codes: B22F 12/70 Gas flow means
• CPC Class Codes: B22F 12/90 Means for process control, e.g. cameras or sensors
• CPC Class Codes: B22F 2009/0892 casting nozzle; controlling metal stream in or after the casting nozzle
• CPC Class Codes: B22F 2202/06 Use of electric fields
• CPC Class Codes: B22F 2203/03 for feed-back
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/003 Apparatus, e.g. furnaces in general F27B
• CPC Class Codes: B22F 3/115 by spraying molten metal, i.e. spray sintering, spray casting
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B41J 2/14 : Structure thereof only for on-demand ink jet heads
• CPC Class Codes: B41J 2002/041 : Electromagnetic transducer
• CPC Class Codes: B41J 2202/04 : Heads using conductive ink
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

Devices, systems, and methods are directed to applying magnetohydrodynamic forces to liquid metal to eject liquid metal along a controlled pattern, such as a controlled three-dimensional pattern as part of additive manufacturing of an object. The magnetohydrodynamic force can be pulsed to eject droplets of the liquid metal to provide control over accuracy of the object being fabricated. The pulsations can be applied in fluid chambers having high resonance frequencies such that droplet ejection can be effectively controlled over a wide range of frequencies, including high frequencies suitable for liquid metal ejection at rates suitable for commercially viable three-dimensional fabrication.

Claims

1. A nozzle for jetting liquid metal, the nozzle comprising:

a housing defining at least a portion of a fluid chamber having an inlet region and a discharge region;

one or more magnets disposed relative to the housing with a magnetic field of the magnet directed through the housing; and

electrodes defining at least a portion of a firing chamber within the fluid chamber between the inlet region and the discharge region, wherein electric current is conductible from the electrodes into the firing chamber at least at a point substantially adjacent to a discharge orifice of the discharge region, and the electric current intersects the magnetic field in the firing chamber at the point substantially adjacent to the discharge orifice to eject liquid metal from the discharge orifice.

2. The nozzle of claim 1, wherein a volume of the fluid chamber between the firing chamber and the discharge orifice is less than about ten percent of a total volume of the fluid chamber.

3. The nozzle of claim 1, wherein the volume of the firing chamber is greater than about 50 percent of the total volume of the fluid chamber.

4. The nozzle of claim 1, wherein the fluid chamber has an axial length of greater than about 2 mm and less than about 2 cm.

5. The nozzle of claim 1, wherein at least one of the electrodes is integrally formed with a portion of the housing defining at least a portion of the fluid chamber such that the at least one electrode and the portion of the housing defining at least one of the fluid chamber are formed of the same material.

6. The nozzle of claim 5, wherein at least one of the electrodes is integrally formed with a portion of the housing defining at least the discharge region of the fluid chamber such that the at least one electrode and the portion of the housing defining the discharge region are formed of the same material.

7. The nozzle of claim 1, wherein the housing is a rod of electrically conductive material and electric current is conductible between the electrodes along an axis parallel to an axial dimension of the rod.

8. The nozzle of claim 1, wherein the firing chamber includes a substantially rectangular cross-section in a plane perpendicular to a direction of travel of liquid metal from the inlet region toward the discharge region, and electric current from the electrodes is conductible into liquid metal along the substantially rectangular cross-section.

9. The nozzle of claim 1, further comprising a filter disposed along the fluid chamber and spaced apart from the discharge region.

10. The nozzle of claim 1, wherein at least one of the electrodes is formed of tantalum, niobium, or a combination thereof.

11. An additive manufacturing system, the system comprising:

a nozzle including a housing, one or more magnets, and electrodes, the nozzle defining a fluid chamber having an inlet region and a discharge region, the one or more magnets directing a magnetic field through the housing, and the electrodes defining at least a portion of a firing chamber in the fluid chamber between the inlet region and the discharge region, wherein electric current is conductible from the electrodes such that the electric current intersects the magnetic field in the firing chamber at a point substantially adjacent to a discharge orifice of the discharge region;

a robotic system mechanically coupled to the nozzle;

an electrical power source in electrical communication with the electrodes; and

a controller in electrical communication with the robotic system and the electrical power source, the controller configured to

move the robotic system to position the discharge region of the nozzle in a controlled three-dimensional pattern, and

based on the position of the discharge region along the controlled three-dimensional pattern, to actuate the power source to deliver pulsed current to the electrodes to eject liquid metal from the discharge region to form a three-dimensional object.

12. The system of claim 11, wherein the frequency of the pulsed current is less than about 5 kHz at a maximum speed of movement of the discharge region.

13. The system of claim 11, wherein the pulsed current has a frequency based on speed of movement of the nozzle.

14. The system of claim 11, wherein the pulsed current has a frequency based on one or more features of the three-dimensional pattern.

15. A method of additive manufacturing, the method comprising:

providing a liquid metal in a fluid chamber at least partially defined by a housing, the fluid chamber having an inlet region and a discharge region;

directing a magnetic field through the housing;

moving the discharge region in a controlled three-dimensional pattern; and

based on the position of the discharge region along the controlled three-dimensional pattern, conducting a pulsed electric current into the liquid metal in a firing chamber within the fluid chamber between the inlet region and the discharge region, wherein the pulsed electric current is at a frequency less than a resonant frequency of the liquid metal in the fluid chamber, and the pulsed electric current is in a direction intersecting the magnetic field in the firing chamber such that pulsation of electric current ejects liquid metal from the discharge region to form a three-dimensional object.

16. The method of claim 15, wherein the pulsed electric current is conducted into liquid metal in the firing chamber substantially adjacent to the discharge region.

17. The method of claim 15, wherein the resonant frequency of the liquid metal in the fluid chamber is greater than about 10 kHz.

18. The method of claim 15, wherein the volume of the firing chamber is greater than about 50 percent of the volume of the fluid chamber.

19. The method of claim 15, wherein electrical resistivity of the liquid metal is substantially similar to electrical resistivity of material defining the firing chamber.