Patent Description:
Additive Manufacturing (AM) also known as cladding, surfacing and 3D printing has been used for many years to solve engineering challenges from surface treatment of production parts to repair of worn parts for resale as re-manufactured parts. AM has become a worldwide focus of interest, development, and investment in virtually every industrial and military manufacturing sector. Increasingly, this focus is broadening to include AM processes that exhibit higher productivity, as measured by the mass of material produced per unit of time.

The higher rate deposition AM processes fall into a class called "direct energy deposition (DED)", which can be characterized by material type and the type of energy source used. Material types can be further refined to powder and wire. Energy sources include laser beam, electron beam, plasma and electric arc. The most productive wire-based systems include gas metal arc welding (GMAW), electron beam (EBW) wire deposition, and laser beam (LBW) wire deposition. Each of these DED, AM solutions has its own set of productivity constraints, which are usually related to the method of energy delivery to the AM wire. EBW is hampered by vacuum requirements; GMAW is challenged by arc physics; and laser solutions are currently limited by the laser power delivery capability of available optical devices.

Currently available laser beam wire deposition optical devices and systems, such as known from <CIT>, require one or more transmissive, laser beam delivery optical elements. Because transmissive optical elements are comparatively fragile and are frequently hampered by process contamination, these elements limit the power that can predictably be delivered for melting the wire used in the additive manufacturing process. Another common limitation of the laser wire additive manufacturing process is the unidirectional nature of the process when a laser beam is delivered onto only one side of the AM wire. To address this, certain prior art systems utilize "coaxial" delivery of the laser beam to the AM wire rather than off-set delivery.

Coaxial wire feed heads allow for omnidirectional material deposition by supplying wire through the center of an optical system, normal to the work plane, potentially simplifying the laser directed energy deposition (L-DED) process. Using this technology, AM "builds" and repairs no longer require complex motion to ensure that the wire feed maintains a specific heading relative to the direction of travel to obtain process consistency. However, currently available optical systems still require the use of transmissive optical elements which limit the consistency and amount of laser power that can be delivered to the process, in turn restricting the maximum material deposition rates achievable. These heads also require the use of protective transmissive window(s) that are prone to contamination and thermal distortion, potentially limiting process robustness. Accordingly, there is an ongoing need for a coaxial laser beam wire deposition device that includes optics that overcome the limitations of the prior art.

The following provides a summary of certain example implementations of the disclosed inventive subject matter. This summary is not an extensive overview and is not intended to identify key or critical aspects or elements of the disclosed inventive subject matter or to delineate its scope. However, it is to be understood that the use of indefinite articles in the language used to describe and claim the disclosed inventive subject matter is not intended in any way to limit the described inventive subject matter. Rather the use of "a" or "an" should be interpreted to mean "at least one" or "one or more".

The invention provides an apparatus according to claim <NUM>. positioned within the optical housing at a predetermined angle, wherein the shielded conduit is adapted to receive the wire therein. The apparatus may further include at least one gas inlet formed in the optical housing, wherein the gas inlet is adapted to receive pressurized gas therethrough, and wherein the pressurized gas provides shielding at a work surface involving the wire. The apparatus may further include a plate for supporting the first reflective optic, wherein the supportive plate is adapted to provide cooling water to the interior of the optical housing and wherein the supportive plate includes a plurality of spokes formed therein for allowing reflected laser light to pass therethrough. The apparatus may further include a wire alignment device disposed with the optical housing, wherein the wire alignment device is operative to position the wire coaxially with the laser beam and perpendicular to a work surface. The first reflective optic may be a conical mirror or a toroidal mirror and the second reflective optic may be a toroidal mirror.

The apparatus may comprise an optical housing, wherein the optical housing includes an upper portion, wherein the upper portion is adapted to connect to a laser, and wherein the laser directs a laser beam into and through the optical housing; a middle portion connected to the upper portion; and a lower portion connected to the middle portion; a conduit disposed within the optical housing at a predetermined angle, wherein the conduit passes through the upper, middle, and lower portions of the optical housing; the wire disposed within the conduct; ; a nozzle connected to the lower portion of the housing for receiving the wire from the conduit; an alignment mechanism disposed within the nozzle, wherein the alignment mechanism reorients the wire exiting the lower portion of the optical housing into a position coaxial with the laser beam and perpendicular to a work surface; the first and second reflective optics are disposed within the middle portion of the housing. apparatus may further include at least one gas inlet formed in the optical housing, wherein the gas inlet is adapted to receive pressurized gas therethrough, and wherein the pressurized gas provides shielding at the work surface. The apparatus may further include at least one water inlet and at least one water exit for allowing cooling water to flow into and through the optical housing for cooling the first reflective optic. The apparatus may further include a plate for supporting the first reflective optic, wherein the supportive plate is adapted to provide cooling water to first reflective optic, and wherein the supportive plate includes a plurality of spokes formed therein for allowing reflected laser light to pass therethrough. The first reflective optic may be a conical mirror or a toroidal mirror and the second reflective optic may be a toroidal mirror.

It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein and may be implemented to achieve the benefits as described herein. Additional features and aspects of the disclosed system, devices, and methods will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the example implementations. As will be appreciated by the skilled artisan, further implementations are possible without departing from the scope of the claims. Accordingly, the drawings and associated descriptions are to be regarded as illustrative and not restrictive in nature.

The accompanying drawings, which are incorporated into and form a part of the specification, schematically illustrate one or more example implementations of the disclosed inventive subject matter and, together with the general description given above and detailed description given below, serve to explain the principles of the disclosed subject matter, and wherein:.

Example implementations are now described with reference to the Figures. Reference numerals are used throughout the detailed description to refer to the various elements and structures. Although the following detailed description contains many specifics for the purposes of illustration, a person of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the disclosed inventive subject matter. Accordingly, the following implementations are set forth without any loss of generality to, and without imposing limitations upon, the claimed subject matter.

Laser-based wire-feed systems, such as Laser Metal Deposition-wire (LMD-w) systems, feed wire through a nozzle, wherein the wire is melted by a laser. The nozzle incorporates inert gas shielding in either an open environment (gas surrounding the laser), or in a sealed gas enclosure or chamber. This process provides higher deposition rates as compared with powder bed and blown powder DED AM processes. However, as described above, the transmissive optics used with these systems create significant limitations with regard to the consistency and amount of laser power that can be delivered to an additive manufacturing process. The disclosed technology eliminates the power limitations of coaxial laser wire AM DED and provides substantially higher metal deposition rates during additive manufacturing.

Commercially available coaxial wire feed heads typically include laser power limitations of 6kW, which restrict the maximum deposition rate to <NUM><NUM>/hr (<NUM> lb/hr) for stainless steel with a density of <NUM>/cm<NUM>. With a <NUM> wire diameter, wire feed speeds of approximately <NUM>/min (<NUM> in/min) are required. Standard wire feeders can supply wire at rates up to <NUM>/min (<NUM>,<NUM> in/min) or greater. However, with additional laser power available, higher wire feed speeds are possible. If wire feed speeds of <NUM>/min (<NUM> in/min) or <NUM>/min (<NUM> in/min) are utilized at higher laser powers, travel speed deposition rates of <NUM><NUM>/hr and <NUM><NUM>/hr, or in stainless steel <NUM> lb/hr and <NUM> lb/hr, respectfully, are potentially achievable (<NUM> wire diameter and <NUM>/cm<NUM> density).

Example implementations of the disclosed system and apparatus are capable of accommodating the laser power levels required for the above listed deposition rates. The system and apparatus are capable of handling laser powers up to <NUM> kW by removing transmissive optics including cover windows that are prone to shift or damage at long-term high-power tasks. This increased power allows for increased energy delivery to the work surface and increased material deposition rates. A fully reflective and water-cooled design, in conjunction with an aerodynamic window, provides a stable laser beam at high laser powers and eliminates the need for protective transmissive windows. The fully reflective design also makes the system wavelength independent, allowing it to be compatible with many laser types and adaptable fiber connector mounts allow the system to be used with many commercially available lasers products.

With reference to the example implementations shown in <FIG>, the disclosed technology provides a system and more particularly, an apparatus that utilizes two paired reflective, rather than transmissive, beam delivery optics to accomplish coaxial delivery of virtually unlimited laser power to the AM wire. The reflective optical elements of the invention (i.e., a conical or toroidal mirror and a toroidal mirror) are much more stable and have much higher resistance to laser damage and distortion than transmissive beam delivery elements. Furthermore, the reflective focus optics in the invention are sufficiently distant from the AM process zone and are protected by an aerodynamic window such that contamination of the optical region of the device is greatly reduced or largely eliminated.

With reference to <FIG>, <FIG> depicts a cross-sectional view of an example implementation of a coaxial laser/wire optical system and apparatus for use in additive manufacturing processes; <FIG> depicts a close-up view of the nozzle component of the system and apparatus of <FIG>; <FIG> depicts a perspective view of the nozzle component of the system and apparatus of <FIG>, wherein the system and apparatus is fully assembled; <FIG> depicts an alternate perspective view of the nozzle component of the system and apparatus of <FIG>, wherein the system and apparatus is fully assembled; <FIG> depicts a perspective view of the spoked support plate, central support, and lower housing portion of the system and apparatus of <FIG>; and <FIG> depicts a perspective view of the conical mirror, spoked support plate, central support, lower housing portion, and reflective nozzle of the system and apparatus of <FIG>, wherein the diverging laser beam is shown entering the optical housing and the coaxial focusing laser beam is shown passing downward through the lower housing portion.

In the example implementation shown in the Figures, coaxial laser-wire apparatus or feed head <NUM> includes optical housing <NUM>, which includes upper housing portion <NUM>, middle housing portion <NUM>, and lower housing portion <NUM>, which are connected to one another by a series of connectors <NUM>. Upper housing portion <NUM> includes chamber <NUM> formed centrally and longitudinally therein and one or more purge gas inlets/ports <NUM> through which gas may be supplied to the interior of optical housing <NUM>. Middle housing portion <NUM> includes chamber <NUM> formed centrally and longitudinally therein as well as cooling water inlet <NUM> and cooling water exit <NUM>. Lower housing portion <NUM> includes chamber <NUM> formed longitudinally therein around central support <NUM>. Reflective nozzle <NUM>, also referred to as a coaxial gas shielding nozzle, is connected to lower housing portion <NUM> and includes nozzle chamber <NUM> formed centrally and longitudinally therein. A portion of chamber <NUM> is constricted to form annular aerodynamic window <NUM> for preventing contaminants and debris from entering optical housing <NUM> and damaging the internal components thereof.

Wire feedstock or wire <NUM> is fed into conduit <NUM> (also referred to as a wire feed liner), which passes in an angular manner through upper housing portion <NUM>, middle housing portion <NUM>, and lower housing portion <NUM>. Conduit <NUM> includes a protective copper sheathing on the outer surfaces thereof in areas that contacting laser beam <NUM>, which assists in reflecting laser beam <NUM> and preventing wire <NUM> and conduit <NUM> from absorbing laser light. In example implementations, conduit <NUM> can accept any round wire up to a diameter of <NUM> (<NUM> in). Conduit <NUM> delivers wire <NUM> directly through optical housing <NUM> while minimizing transitions and preventing wire feeding complications. Wire <NUM> exits conduit <NUM> at the upper portion of nozzle <NUM>, passes into and through wire steering (wire alignment) mechanism <NUM>, out of the bottom portion of nozzle <NUM> (see <FIG>), and onto a work surface. Wire steering mechanism <NUM> is located within chamber <NUM> and operates to position wire feedstock <NUM> perpendicular or normal to a work surface. Wire steering mechanism <NUM> is manually adjustable for directing or positioning wire <NUM>, as necessary or desired. This device can be used to align wire <NUM> with laser beam <NUM> and maximize equal heating. Wire <NUM> can be tilted inside a ball type joint (see <FIG>) included in wire steering mechanism <NUM> and locked into position upon proper alignment. The inclusion of an internal wire management system provides a high degree of dimensional stability for wire <NUM> and facilitates inclusion of annular aerodynamic window <NUM> as a contaminant rejection solution.

Connector <NUM> is attached to the top of upper housing portion <NUM> for receiving a commercially available fiber laser which directs diverging laser beam <NUM> into chamber <NUM>. In example implementations, the fiber connection accepts QBH <NUM> and QBH <NUM> connections, although other connection types are possible. Diverging laser beam <NUM> first encounters conical (or toroidal) mirror <NUM>, which is located on top of support plate <NUM>, centered thereon with locating pin <NUM>, and supported within optical housing <NUM> by central support <NUM>. Conical (or toroidal) mirror <NUM> is cooled by water entering and exiting optical housing <NUM> through cooling water inlet <NUM> and cooling water exit <NUM> respectively. As best shown in <FIG>, support plate <NUM> includes first spoke <NUM> that includes first channel <NUM>, second spoke <NUM> that includes second channel <NUM>, third spoke <NUM>, and cavity <NUM>. Cooling water flows toward cavity <NUM> through first channel <NUM> and away from cavity <NUM> through second channel <NUM>. Laser beam <NUM> then expands radially outward where it then encounters toroidal mirror <NUM> (also referred to as a ring reflective optic). As the laser beam travels radially outward, its irradiance decreases substantially such that it is safely reflected by the protective sheathing provided on conduit <NUM>, which guides the AM wire. Toroidal mirror <NUM> then redirects the laser energy into coaxial focusing laser beam <NUM> which surrounds the outer diameter of wire <NUM> near the bottom of nozzle <NUM>. The specific design of toroidal mirror <NUM> permits laser irradiance on the outside surface of the AM wire to be controlled along the length of the beam-wire interaction region, thereby permitting a high degree of control of wire melting efficiency. Thus, wire <NUM>, laser beam <NUM> and shielding gas all arrive at a highly controllable processing zone and melt the AM wire onto a work surface.

Removing absorbed heat from reflective optics is still a concern at high power levels; therefore, water cooling is utilized to extend reflective optic life and improve performance. Water cooling passages <NUM> and <NUM> are illustrated in FIGS and <NUM>. Inert coaxial purge gas is supplied to the laser beam path for maintaining positive pressure inside optical housing <NUM> to prevent contamination and to assisting with overall cooling. Nozzle <NUM> directs the coaxial gas to the work plane and supplies primary shielding against build-up. Coaxial gas flows down the laser beam path through a narrowing gap (i.e., annular aerodynamic window <NUM>). This reduction in cross sectional area increases flow velocities in localized areas, thereby helping to resist and expel any contaminants generated on the work surface during the AM process.

All literature and similar material cited in this application, including, but not limited to, patents, patent applications, articles, books, treatises, and web pages, regardless of the format of such literature and similar materials, are expressly incorporated by reference in their entirety. In the event that one or more of the incorporated references and similar materials differs from or contradicts this application, including but not limited to defined terms, term usage, described techniques, or the like, this application controls.

As previously stated and as used herein, the singular forms "a," "an," and "the," refer to both the singular as well as plural, unless the context clearly indicates otherwise. The term "comprising" as used herein is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. Although many methods and materials similar or equivalent to those described herein can be used, particular suitable methods and materials are described herein. Unless context indicates otherwise, the recitations of numerical ranges by endpoints include all numbers subsumed within that range. Furthermore, references to "one implementation" are not intended to be interpreted as excluding the existence of additional implementations that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, implementations "comprising" or "having" an element or a plurality of elements having a particular property may include additional elements whether or not they have that property.

The terms "substantially" and "about" used throughout this specification are used to describe and account for small fluctuations, such as due to variations in processing. For example, these terms can refer to less than or equal to ±<NUM>%, such as less than or equal to ±<NUM>%, such as less than or equal to ±<NUM>%, such as less than or equal to ±<NUM>%, such as less than or equal to ±<NUM>%, such as less than or equal to ±<NUM>%, such as less than or equal to ±<NUM>%, and/or <NUM>%.

Claim 1:
An apparatus for use in laser wire additive manufacturing, comprising:
(a) an optical housing (<NUM>) adapted to receive a laser beam (<NUM>) therein and a wire (<NUM>) therein, wherein the wire (<NUM>) is adapted for use in additive manufacturing;
(b) a first reflective optic (<NUM>) for receiving and reflecting the laser beam (<NUM>); and
(c) a second reflective optic (<NUM>) for receiving laser light reflected by the first reflective optic (<NUM>), wherein the second reflective optic (<NUM>) directs the laser light received from the first reflective optic (<NUM>) onto the wire (<NUM>) in a cylindrical configuration such that the wire (<NUM>) and the cylinder of laser light are coaxial with regard to one another within a portion of the optical housing (<NUM>);
charecterised by, the apparatus further comprising:
an aerodynamic window (<NUM>) disposed within the optical housing (<NUM>) for preventing contaminants from damaging the reflective optics.