CONTROLLING QUIESCENT OPERATION OF MAGNETOHYDRODYNAMIC SYSTEMS FOR METAL MANUFACTURING

• US 20170252824A1
• Filed: 03/06/2017
• Published: 09/07/2017
• Est. Priority Date: 03/03/2016
• Status: Abandoned Application

• Current Assignee: Desktop Metal, Inc.
• Original Assignee: Desktop Metal, Inc.
• Inventors: Gibson, Mark Gardner, Hoisington, Paul A., Fontana, Richard Remo
• Application Number:
  US15/451,286
• Publication Number:
  US 20170252824A1
• 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. Electric current delivered to a meniscus of the liquid metal in a quiescent state can be pulsed to reduce the likelihood of formation of an oxidation layer in nozzles associated with these devices, systems, and methods. Such a reduction in the likelihood of formation of an oxidation layer in nozzles can be useful for maintaining integrity of these nozzles between periods of use, such as between formation of parts.

Claims

1. A 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; and

delivering a first electric current into the liquid metal in a firing chamber within the fluid chamber between the inlet region and the discharge region, the first electric current including a fluctuating electric current intersecting the magnetic field in the liquid metal to exert a pulsating force on a meniscus attached to the discharge region, the pulsating force on the liquid metal attached to the discharge region bouncing the meniscus attached to the discharge region.

2. The method of claim 1, wherein the discharge region includes a discharge orifice and a throat, and the meniscus is attached to one or more of the throat and the discharge orifice.

3. The method of claim 1, wherein the pulsating force exerted on the meniscus has a magnitude sufficient to disrupt a metal oxide layer formed on the meniscus, the metal oxide layer including an oxide of the metal of the liquid metal.

4. The method of claim 1, further comprising, based at least in part on a duration of delivery of the first electric current into the liquid metal in the housing, ejecting the liquid metal through the discharge region.

5. The method of claim 4, wherein the liquid metal is ejected from the discharge region for a predetermined period of time.

6. The method of claim 1, further comprising delivering a second electric current into the liquid metal in the firing chamber, wherein the second electric current intersects the magnetic field in the liquid metal to eject the liquid metal through the discharge region to form an object.

7. The method of claim 6, wherein the second electric current includes a pulsed electric current different from the pulsed electric current of the first electric current.

8. The method of claim 6, further comprising moving the discharge region along a controlled pattern corresponding to fabrication of an object, wherein delivering the second electric current into the liquid is based on a position of the discharge region along the controlled pattern.

9. The method of claim 8, wherein the controlled pattern includes a three-dimensional pattern.

10. The method of claim 8, wherein delivering the second electric current into the liquid metal in the firing chamber includes switching between a pulsed electric current and a direct electric current based at least in part on a position of the discharge region along the controlled pattern.

11. A manufacturing system comprising:

a nozzle including a housing, a magnet, and electrodes, the housing at least partially defining a 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 fluid chamber, 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 from the electrodes intersects the magnetic field in the firing chamber;

a robotic system mechanically coupled to the nozzle, the robotic system 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 robotic system and the electrical power source, the controller configured to

move the robotic system to position the discharge region along a controlled pattern of movement corresponding to fabrication of an object,

deliver a first electric current through the electrodes into a liquid metal in the firing chamber, the first electric current including a pulsed electric current intersecting the magnetic field in the liquid metal in the firing chamber to produce a pulsating force on a meniscus of the liquid metal attached to the discharge region, and

along the controlled pattern of movement of the discharge region, deliver a second electric current through the electrodes into the liquid metal in the firing chamber, the second electric current intersecting the magnetic field in the liquid metal to eject the liquid metal through the discharge region to form an object.

12. The system of claim 11, wherein the controller is further configured to deliver a third electric current through the electrodes into the liquid metal in the firing chamber, the third electric current intersecting the magnetic field in the liquid metal to eject the liquid metal through the discharge region at a position of the discharge region away from the controlled pattern.

13. The system of claim 12, wherein the controller is configured to deliver the third electric current based at least in part on a duration of delivery of the first electric current into the liquid metal in the firing chamber.

14. The system of claim 12, wherein the controller is configured to deliver the third electric current between switching from delivery of the first electric current to delivery of the second electric current.

15. The system of claim 12, wherein the controller is configured to deliver the third electric current for a predetermined period of time.

16. The system of claim 12, wherein the controlled pattern includes a three-dimensional pattern.