MAGNETOHYDRODYNAMIC DEPOSITION RATE CONTROL FOR METAL MANUFACTURING

• US 20170252827A1
• 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, Fontana, Richard Remo
• Granted Patent: US 10,751,799 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. An electric current delivered to produce the magnetohydrodynamic forces can be controlled between a pulsed electric current and a direct electric current to change the rate of liquid metal ejection from a nozzle. For example, the electric current can be switched between a pulsed electric current and a direct electric current based at least in part on a position of the nozzle along the controlled pattern, providing accuracy of liquid metal deposition along portions of the pattern having more detail and providing speed of liquid metal deposition along portions of the pattern having less detail.

Claims

1. 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 pattern; and

delivering electric current between electrodes defining at least a portion of a firing chamber within the fluid chamber between the inlet region and the discharge region, the electric current intersecting the magnetic field in the liquid metal in the firing chamber to eject liquid metal from the discharge region; and

based on the position of the discharge region along the controlled pattern, controlling the electric current between pulsed current and direct current to form an object.

2. The method of claim 1, wherein the controlled pattern is a three-dimensional pattern and the object is a three-dimensional object.

3. The method of claim 1, wherein the electric current is controlled to be pulsed current along a boundary of the object being formed.

4. The method of claim 1, wherein the electric current is controlled to be direct current as the discharge region moves along an excursion within a boundary of the object being formed.

5. The method of claim 1, wherein a frequency of the pulsed current is less than a resonance frequency of the liquid metal in the fluid chamber.

6. The method of claim 1, wherein a frequency of the pulsed current is based on speed of movement of the discharge region.

7. The method of claim 1, wherein a frequency of the pulsed current is based on distance from an edge of the controlled pattern.

8. The method of claim 1, wherein a frequency of the pulsed current is less than about 5 kHz at a maximum speed of movement of the discharge region.

9. The method of claim 1, wherein switching from the pulsed current to the direct current increases a mass flow rate of liquid metal ejected from the discharge region.

10. A computer program product comprising non-transitory computer executable code embodied in a non-transitory computer readable medium that, when executing on one or more processors, performs the steps of:

moving a discharge region of a nozzle in a controlled pattern;

delivering electric current between electrodes defining at least a portion of a firing chamber in fluid communication with the discharge region, the electric current intersecting a magnetic field in a liquid metal in the firing chamber to eject the liquid metal from the discharge region; and

based on the position of the discharge region along the controlled pattern, controlling electric current delivered into the liquid metal in the firing chamber, wherein the electric current is controlled between pulsed current and direct current to form an object.

11. The computer program produce of claim 10, wherein the electric current is controlled to be pulsed current along a boundary of the object being formed.

12. The computer program produce of claim 10, wherein the electric current is controlled to be direct current as the discharge region moves along an excursion within a boundary of the object being formed.

13. The computer program produce of claim 10, wherein a frequency of the pulsed current is based on speed of movement of the discharge region.

14. The computer program produce of claim 10, wherein a frequency of the pulsed current is based on distance from an edge of the controlled pattern.

15. The computer program produce of claim 10, wherein a frequency of the pulsed current is less than about 5 kHz at a maximum speed of movement of the discharge region.

16. An additive manufacturing system, the system comprising:

a nozzle including a housing, a magnet, and electrodes, the housing defining at least a portion of a fluid chamber, the fluid chamber having an inlet region and a discharge region, the magnet disposed relative to the housing with a magnetic field of the magnet extending through the housing, and the electrodes defining at least a portion of a firing chamber within the fluid chamber between the inlet region and the discharge region, the electrodes positioned relative to the magnet such that electric current delivered between the electrodes intersects the magnetic field in the firing chamber;

a robotic system mechanically coupled to the nozzle and movable to position the discharge region;

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

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

move the robotic system to position the discharge region in a controlled pattern,

deliver electric current from the electrodes into a liquid metal in the firing chamber,

based on the position of the discharge region along the controlled pattern, control electric current delivered into liquid metal in the firing chamber, wherein the electric current is controlled between pulsed current and direct current to form an object.

17. The system of claim 16, wherein the electric current is controlled to be pulsed current along a boundary of the object being formed.

18. The system of claim 16, wherein the electric current is controlled to be direct current as the discharge region moves along an excursion within a boundary of the object being formed.

19. The system of claim 16, wherein a frequency of the pulsed current is based on speed of movement of the discharge region.

20. The system of claim 16, wherein a frequency of the pulsed current is based on distance from an edge of the controlled pattern.