CONTROLLING MENISCUS POSITION FOR MAGNETOHYDRODYNAMIC METAL MANUFACTURING

• US 20170252830A1
• 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, Hoisington, Paul A.
• Granted Patent: US 11,338,365 B2
• Time in Patent Office: Days
• CPC Class Codes: B05B 17/04 operating with special methods
• CPC Class Codes: B05B 5/025 Discharge apparatus, e.g. electrostatic spray guns
• CPC Class Codes: B05B 5/043 using induction-charging
• CPC Class Codes: B05B 5/1608 the liquid or other fluent material being electrically conductive
• 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 10/10 Formation of a green body
• CPC Class Codes: B22F 10/22 Direct deposition of molten metal
• CPC Class Codes: B22F 10/38 to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
• CPC Class Codes: B22F 10/43 characterised by material
• CPC Class Codes: B22F 12/10 Auxiliary heating means
• CPC Class Codes: B22F 12/20 Cooling means
• CPC Class Codes: B22F 12/38 Housings, e.g. machine housings
• 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 2202/07 by induction
• 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 directed to exert a pullback force on the liquid metal. The pullback force can be sufficient to draw the liquid metal, in the quiescent state, in a direction toward the nozzle to reduce the likelihood of unintended wetting of surfaces of the nozzle between uses of the nozzle.

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;

delivering a first electric current into the liquid metal in the housing in a quiescent state, the first electric current intersecting the magnetic field in the liquid metal to exert a pullback force on the liquid metal, the pullback force sufficient to draw the liquid metal, in the quiescent state, in a direction from the discharge region toward the inlet region; and

selectively delivering a second electric current into the liquid metal, the second electric current intersecting the magnetic field in the liquid metal to exert a firing force on the liquid metal to eject liquid metal from the discharge region.

2. The method of claim 1, wherein the pullback force sufficient to maintain a meniscus of the liquid metal, in the quiescent state, attached to the discharge region.

3. The method of claim 2, wherein the discharge region has a throat adjacent to a discharge orifice, the pullback force is sufficient to maintain the meniscus within the throat or attached to the discharge orifice.

4. The method of claim 1, further comprising moving the discharge region along a controlled pattern.

5. The method of claim 4, wherein the controlled pattern is a controlled three-dimensional pattern.

6. The method of claim 4, wherein the second electric current is selectively delivered into the liquid current along less than the entirety of the controlled pattern.

7. The method of claim 4, wherein the second electric current is variable based at least upon a position of the discharge region along the controlled pattern.

8. The method of claim 1, wherein the second electric current includes a pulsed electric current, the pulsed electric current ejecting liquid metal droplets from the discharge region.

9. The method of claim 8, wherein selectively delivering the second electric current into the liquid metal includes conducting a firing pulse into the liquid metal in the fluid chamber, and conducting a pullback pulse into the liquid metal in the fluid chamber, the firing pulse and the pullback pulse having opposite polarities, and the pullback pulse having the same polarity as the first electric current.

10. The method of claim 9, wherein the pullback pulse precedes the firing pulse for ejection of a respective droplet.

11. The method of claim 9, wherein the pullback pulse follows the firing pulse for ejection of a respective droplet.

12. The method of claim 1, wherein the second electric current is variable between a pulsed electric current and a direct electric current.

13. The method of claim 1, wherein selectively delivering the second electric current into the liquid metal includes directing the second electric current into the liquid metal between electrodes defining a firing chamber within the fluid chamber between the inlet region and the discharge region.

14. The method of claim 13, wherein delivering the first electric current into the liquid metal includes directing the first electric current into the liquid metal between the electrodes.

15. A manufacturing system comprising:

a nozzle including a housing, a magnet, and electrodes, the housing 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;

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

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

deliver a first electric current into a liquid metal in the housing in a quiescent state, the first electric current intersecting the magnetic field in the liquid metal to exert a pullback force on the liquid metal, the pullback force sufficient to draw the liquid metal, in the quiescent state, in a direction from the discharge region toward the inlet region, and

selectively deliver a second electric current from the electrodes into the liquid metal in the firing chamber, the second electric current intersecting the magnetic field in the liquid metal to exert a firing force on the liquid metal to eject liquid metal from the discharge region.

16. The system of claim 15, further comprising a robotic system mechanically coupled to the nozzle and movable to position the discharge region of the nozzle, wherein the controller is further configured to move the robotic system to position the discharge region along a controlled pattern.

17. The system of claim 16, wherein the second electric current is selectively delivered into the liquid current along less than the entirety of the controlled pattern.

18. The system of claim 16, wherein the second electric current is variable based at least upon a position of the discharge region along the controlled pattern.

19. The system of claim 16, wherein the controlled pattern is a three-dimensional pattern.

20. The system of claim 15, wherein selectively delivering the second electric current includes controlling the second electric current between a pulsed electric current and a direct electric current.