MAGNETOHYDRODYNAMIC FORMATION OF SUPPORT STRUCTURES FOR METAL MANUFACTURING

• US 20170252825A1
• 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: Fontana, Richard Remo, Gibson, Michael Andrew
• Granted Patent: US 10,639,717 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. Porosity of one or more predetermined portions of objects fabricated from an accumulation of liquid metal droplets ejected using magnetohydrodynamic force can be controlled to form interfaces between support structures and parts within the object. Higher porosity along the interfaces, as compared to porosity along the support structures and the parts, can be useful for facilitating separation of the parts from the support structures.

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 three-dimensional pattern; and

delivering electric current between electrodes at least partially defining 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 the liquid metal from the discharge region; and

based on the position of the discharge region along the controlled three-dimensional pattern, controlling porosity of one or more predetermined portions of an accumulation of the ejected liquid metal on a build plate or on a previously deposited layer of metal.

2. The method of claim 1, wherein controlling porosity of the one or more predetermined portions of the accumulation of the ejected liquid metal includes forming an interface between a support structure and a three-dimensional object in the accumulation, the support structure and the three-dimensional object having lower porosity than the interface.

3. The method of claim 2, wherein the interface, the support structure and the three-dimensional object are formed of the same material.

4. The method of claim 2, wherein the interface is frangible relative to the three-dimensional object.

5. The method of claim 4, further comprising separating the three-dimensional object from the support structure through application of one or more of a compressive force and a shear force to the interface.

6. The method of claim 1, wherein controlling porosity of the one or more predetermined portions of the accumulation of the ejected liquid metal includes changing velocity of the liquid metal ejected from the discharge region.

7. The method of claim 6, wherein changing the velocity of the liquid metal ejected from the discharge region includes changing a magnitude of the electric current delivered into the liquid metal in the firing chamber.

8. The method of claim 6, wherein delivering electric current into the liquid metal in the firing chamber includes pulsing the electric current.

9. The method of claim 6, wherein changing the velocity of the liquid metal ejected from the discharge region includes changing at least one of a magnitude and a duration of a pulse of the electric current.

10. The method of claim 1, wherein controlling porosity of the one or more predetermined portions of the accumulation of the ejected liquid metal includes changing temperature of the liquid metal ejected from the discharge region.

11. The method of claim 10, wherein changing the temperature of the liquid metal ejected from the discharge region includes reducing the temperature of the ejected liquid metal to increase porosity of a predetermined portion of the accumulation of the ejected liquid metal on the build plate or on the previously deposited layer of metal.

12. 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 housing in a controlled three-dimensional pattern;

delivering electric current into a liquid metal in a firing chamber at least partially defined by electrodes, the delivered electric current intersecting a magnetic field in the liquid metal in the firing chamber to eject the liquid metal from the discharge region in fluid communication with the firing chamber; and

based on the position of the discharge region along the controlled three-dimensional pattern, controlling porosity of one or more predetermined portions of an accumulation of the ejected liquid metal on a substrate or on a previously deposited layer of metal.

13. The computer program product of claim 12, wherein controlling porosity of the one or more predetermined portions of the accumulation of the ejected liquid metal includes changing velocity of the liquid metal ejected from the discharge region.

14. The computer program product of claim 13, wherein changing the velocity of the liquid metal ejected from the discharge region includes changing a magnitude of the electric current.

15. The computer program product of claim 13, wherein delivering electric current into the liquid metal in the firing chamber includes pulsing the electric current.

16. The computer program product of claim 15, wherein changing the velocity of the liquid metal ejected from the discharge region includes changing at least one of a magnitude and a duration of the pulse of the electric current.

17. The computer program product of claim 12, wherein controlling porosity of the one or more predetermined portions of the accumulation of the ejected liquid metal includes changing temperature of the liquid metal ejected from the discharge region.

18. The computer program product of claim 17, wherein changing the temperature of the liquid metal ejected from the discharge region includes reducing the temperature of the ejected liquid metal to increase porosity of a predetermined portion of the accumulation of the ejected liquid metal on the substrate or on the previously deposited layer of metal.