Aerodynamic beam generator for large particles

Details Aerodynamic beam generator for large particles Aerodynamic beam generator for large particles

1999-09-10

2002-02-19

Nguyen, Kiet T. (Department: 2881)

Radiant energy

Electrically neutral molecular or atomic beam devices and...

C250S288000, C436S173000

Reexamination Certificate

active

06348687

ABSTRACT:

BACKGROUND
The present invention relates generally to material fabrication, and more specifically to generating a tightly focused beam of large material particles as are useful for additive fabrication techniques.
Aerodynamic focusing of large particles is a technology which can be applied to various direct fabrication technologies, including direct laser fabrication (LENS), hot spray, and cold spray processing. The LENS process uses a laser to melt a small puddle on a working surface. Growth material in the form of large (>10 &mgr;m) particles is then added to the puddle, some of which melts therein and becomes incorporated into the component being grown. In cold spray processing, rapid deposition of a wide range of materials occurs when large particles are delivered against a growth surface at velocities in the 400-1000 m/sec regime. Hot spray processing passes the particles through a laser, which melts the particles before the hit the growth surface. All of the above processes are capable of providing special material properties to the final component.
A primary difficulty which appears in all known direct fabrication technologies is to direct the material being added to the precise point where it is needed, thereby obtaining a finely detailed product. Unfortunately, current methods of supplying powders to the growth surface produce broad and unfocused patterns of powder distribution, whereas the desired distribution is narrow (e.g., <1 mm), and focused to a specific region.
The most common approach toward obtaining a spray of particles is to pass a carrier gas in which a series of particles is entrained through a simple expansion nozzle. The result is a wide and diverging plume of relatively slow particles. This plume can be narrowed by removing the outer regions of the plume with a particle diverter (e.g., a cone-shaped aperture with a hole at the apex), but this approach reduces the flux of particles to the extent that a fabrication process based thereon is impracticably slow.
There is therefore a need for a source of beams of large solid particles with velocity vectors accurately directed, or focused, along a single direction. Useful patterns of particles can be line-like (one-dimensional) or plane-like (two-dimensional) in the direction of motion.
SUMMARY OF THE INVENTION
The present invention is a device to generate tightly focused beams of large (1 &mgr;m<<L<<100 &mgr;m) material particles. These particles can be generated in quantity, and with velocities ranging from a few feet per second to supersonic velocities with appropriate post-focusing acceleration. Such particle beams are of considerable importance for additive fabrication techniques, where the particles are directed precisely against the spot on a workpiece where they are to be added, whereupon an energetic influence (laser heating, heating due to impact deformation, etc.) causes the particle to merge with the structure of the workpiece. A single line-like beam source can deliver on the order of a cubic centimeter of particles per minute to a growing component, a value considerably in excess of those characteristic of present direct additive fabrication techniques with the further benefit of minimal overspray resulting in much higher efficiency in material usage.


REFERENCES:
patent: 5270542 (1993-12-01), McMurry et al.
patent: 5565677 (1996-10-01), Wexler et al.
patent: 5681752 (1997-10-01), Prather
patent: 5998215 (1999-12-01), Prather et al.

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