Powder distribution device for laser cladding system

Abstract

The invention refers to a powder distribution device for a laser cladding system, to distribute a flow of powder to the powder inlets of a nozzle of a laser head. The device comprises: a straight conduit for the passage of a flow of powder, a chamber fluidly communicated with and outlet end of the conduit, wherein the chamber has a powder accumulation surface placed opposite the outlet end of the conduit, and at least two outlet conduits placed downstream the chamber and fluidly communicated with the chamber. The outlet conduits are arranged to diverge with respect to each other, so as to branch off the powder accumulated in the chamber. The device of the invention accomplishes an equal branching of a powder flow, so that all the powder inlets of a nozzle of a laser head, are supplied with an equal and consistent powder flow, to ensure quality of the metal deposition process.

Description

[0001] POWDER DISTRIBUTION DEVICE FOR LASER CLADDING SYSTEM

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates in general to additive manufacturing technologies, that use metal or ceramic powders to build up pieces, to repair or to coat surfaces.

[0005] More in particular, the present invention refers to a powder distribution device, which distributes a flow of metal or ceramic powder to the powder inlets of a nozzle of a laser head.

[0006] An object of the invention is to provide a powder distribution device, which accomplish an equal branching of a powder flow, so that all the powder inlets of a nozzle of a laser head, are supplied with an equal and consistent flow of powder to ensure quality of the metal deposition process.

[0007] BACKGROUND OF THE INVENTION

[0008] Laser cladding is an industrial process in which a laser beam is focused on a surface of a substrate or a workpiece, while a filler material in the form of a wire or powder is supplied through a nozzle to be melted by the laser beam, such that a melt pool is formed on the substrate where the laser beam meets the filler material.

[0009] In the case of powder as filler material, powder is supplied from a powder feeder which has powder hopper storing the powder, into which a gas is injected creating a pressure in the hopper. Usually nitrogen or argon is used, and occasionally helium. When the powder feeder is switched on: gas and powder are conveyed from a powder feeder to a laser head through a hose, from which it is distributed and injected to a nozzle of the laser head through several inlets. In the case of a coaxial nozzle, it generates a flow of powder in the form of a cone converging with the laser beam; in the case of a multi-jet nozzle, the powder flow from each jet converges together in a point with the laser beam.

[0010] The U.S. patent publications US 2006 / 0266740 A1 , US 2011 / 0089151 A1 describe laser cladding equipment of this type.

[0011] To assure high-quality of the laser cladding process, it is critical that all the powder inlets of the coaxial nozzle or a multi-jet nozzle, are supplied with an equal and consistent flow of powder in terms of flow rate and powder particles velocity.

[0012] However, since powder has to travel along a relatively long distance from the powder feeder to the nozzle, and have to flow through intricated conduits of different cross-sections, frequently velocity of powder particles is reduced or increased with respect to the desired velocity, and the flow of powder may become turbulent. As a result, powder cannot be injected in the desired direction into the nozzle, and powder clogs in the distribution conduits are common.

[0013] Therefore, there is still much room for improvement in this technical field, to ensure an even and consistent powder flow distribution to the nozzle of a laser head.

[0014] DESCRIPTION OF THE INVENTION

[0015] The invention is defined in the attached independent claims, and satisfactorily solves the above-described drawbacks of the prior art, by the provision of a powder distribution device for a laser cladding equipment, wherein the device comprises a straight conduit for the passage of a flow of powder. The conduit has an inlet end and an outlet end, and a constant cross-sectional area between the inlet and outlet ends.

[0016] The powder distribution device further comprises a chamber fluidly communicated with the outlet end of the conduit. The cross-sectional area of the chamber is larger than the cross- sectional area of the conduit, and the chamber has a powder accumulation surface placed opposite the outlet end of the conduit, such that, when used in a practical application, the straight conduits vertically arranged and powder flows with carrier gas through the conduit, powder coming from the outlet end would be deposited and accumulate on the powder accumulation surface, so that a mound of powder in the form of a cone, is formed on the powder accumulation surface.

[0017] The powder accumulation surface may have a recess to facilitate the accumulation of powder to build up the mound of powder. In a practical embodiment of the invention, the depression has a conical configuration coaxially aligned with the axis of the straight conduit.

[0018] The powder distribution device also comprises at least two outlet ducts placed downstream the chamber and fluidly communicated with the chamber. The outlet ducts are arranged to diverge with respect to each other, so as to branch off the powder accumulated in the chamber. All the outlet ducts have the same volume and shape, in order to obtain an equal distribution of powder.

[0019] The formation of this mound of powder and its position, provides the effect that powder is evenly distributed through all the outlet ducts.

[0020] Preferably, both, the straight conduit and the chamber have a cylindrical configuration, and are coaxially arranged. The volume of the straight conduit is larger than the volume of the chamber, preferably the ratio between the volume of the straight conduit and the volume of the chamber is 68%.

[0021] The straight conduit extends along an axis (X), and the outlet ducts extent respectively along axes (Y, Y'). The axes (Y, Y') define the same angle (a) with respect to the axis (X). Preferably, the angle (a) is within the range 30° - 45°.

[0022] The outlet ducts are arranged such that axes (Y, Y') intersect the axis (X) at a point placed above the powder accumulation surface.

[0023] In a preferred embodiment of the invention, the powder distribution device has more than two outlet ducts, for example three of four outlet ducts, equidistantly distributed around the powder accumulation surface.

[0024] Another aspect of the invention refers to a laser cladding system, provided with the powder distribution device of the invention. The laser cladding system conventionally comprises a powder feeder including a powder hopper and powder dispensing means adapted to supply a flow of powder with carrier gas from the powder reservoir. The system also has a laser head including a nozzle having two or more powder inlets, and configured to produce a jet of powder, for example in the form of a cone using a coaxial nozzle converging with a laser beam.

[0025] The powder distribution device is fluidly communicated with the powder feeder, for example by means of a flexible hose, preferably an antistatic flexible hose. The powder distribution device, is configured to branch off the flow of powder supplied by the powder feeder into discrete flows of powder. Two or more tubes are provided communicating each discrete flow of powder with one powder inlet of the nozzle.

[0026] The powder distribution device is placed such that the straight conduit is vertically arranged with respect to ground, in order to straightening the powder particle trajectory. Powder would flow by carrier gas throughout the straight conduit and get accumulated on the powder accumulation surface.

[0027] Having the straight conduit aligned and placed in a vertical position, allow the formation of a conical mound of powder right in the center of the powder accumulation surface, which is turn achieves an evenly distribution of powder to all the outlets.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To complete the description and in order to provide a better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate embodiments of the invention, which should not be interpreted as restricting the scope of the invention, but just as examples of how the invention can be carried out. The drawings comprise the following figures:

[0030] Figure 1.- shows several views of a power distribution device according to the invention, with two output ducts. Figure A is a perspective view wherein the lower part has been represented as a transparent body to allow visualization of its interior; Figure B is a longitudinal cross- sectional view taken along plane A-A in Figure D; Figure C is a cross-sectional view taken at plane B-B in Figure B, Figures D to G are several elevational views, and Figure H is a bottom view.

[0031] Figure 2.- shows an enlarged view of Figure 1B.

[0032] Figure 3.- shows a schematic representation of a laser cladding system incorporating the powder distribution device of the previous figures.

[0033] Figure 4.- shows several views of a power distribution device according to the invention, with three output ducts. Figure A is a perspective view wherein the lower part has been represented as a transparent body to allow visualization of its interior; Figure B is a longitudinal cross- sectional view taken along plane A-A in Figure E; Figure C is a cross-sectional view taken at plane D-D in Figure B, Figures D to F are several elevational views, and Figure G is a bottom view.

[0034] Figure 5.- shows several views of a power distribution device according to the invention, with four output ducts. Figure A is a perspective view wherein the lower part has been represented as a transparent body to allow visualization of its interior; Figure B is a longitudinal cross- sectional view taken along plane A-A in Figure E; Figure C is a cross-sectional view taken at plane B-B in Figure B, Figures D to G are several elevational views, and Figure H is a bottom view.

[0035] PREFERRED EMBODIMENTS OF THE INVENTION

[0036] Figures 1A - 1H and Figure 2 show several views of an exemplary embodiment of a powder distribution device (1) of the invention with two outlet ducts. The device (1) has a rigid tube (2) inside which is formed a straight conduit (3) for the passage of a flow of powder. The straight conduit (3) extends along an axis “X” between inlet and outlet ends (3a, 3b) and it has a cylindrical shape, so that it has a constant cross-sectional area between its two ends.

[0037] The rigid tube (2) has an input end (2a) having a socket or threaded bore (4) adapted for its connection with a hose to receive metal powder as it will be described later on.

[0038] The powder distribution device (1) has a distribution head (5) which is mechanically coupled to an output end (2b) of the rigid tube (2), in this example the distribution head (5) is threaded to the output end (2b).

[0039] The distribution head (5) has a chamber (6) fluidly communicated with the straight conduit (3), and it also has a cylindrical configuration with a diameter larger than the diameter of the straight conduit (3), so that, the cross-sectional area of the chamber (6) is larger than the cross-sectional area of the conduit. The chamber (6) is coaxially arranged with the straight conduit (3).

[0040] Furthermore, the distribution head (5) has, in this case, two outlet ducts (10, 10') placed downstream the chamber (6) and fluidly communicating the chamber (6) with the exterior of the distribution head (5). The outlet ducts (10, 10') have the same volume and the same cylindrical shape, and are arranged to diverge with respect to each other.

[0041] More in detail, the outlet ducts (10, 10') extent respectively along axes (Y, Y'), and each one of these axes (Y, Y') define the same angle (a) with respect to the axis (X). The angle (a) is within the range 30° - 45° in this embodiment.

[0042] The chamber (6) is configured for the accumulation of powder coming from the straight conduit (3) in order to distribute or branch off equally the flow of powder coming from the straight conduit (3) into discrete flows of powder. For that, the chamber (6) has a powder accumulation surface (7) placed opposite the outlet end (2b) of the straight conduit (3). The powder distribution device (1) is meant to be used in a perfectly vertical position as shown in the enlarged view of Figure 2, with the straight conduit (3) placed above the distribution head (5), and metal powder (8) would move by carrier gas only throughout the straight conduit (3), such that metal powder (8) would accumulate on the powder accumulation surface (7) forming a mound (9) of metal power of generally conical shape.

[0043] As represented in Figure 2, the outlet ducts (10, 10') are arranged such their axes (Y, Y') intersect the axis (X) at a point placed above the mound (9) of metal powder, so in this way, as powder continues coming from the straight conduit, powder from the mound (9) of metal powder is distributed by carrier gas in the same amount to the outlet ducts (10, 10').

[0044] To facilitate the formation and for the stability of the mound (9) of metal powder, the powder accumulation surface (7) has a recess or niche (11), for example of conical configuration.

[0045] In the invention, it has been found that a ratio between the length of the straight conduit (3) and its diameter, within the range 3% - 4% is preferred for the intended purpose of equal powder distribution.

[0046] Additionally, a preferred ratio between the volume of the straight conduit and the volume of the chamber is 68%.

[0047] It is critical that powder particles do not lose velocity when they pass through a change of section (change of section from the conduit to the chamber), so the chamber (6) of the distribution head (5) must have a smaller volume than the straight conduit (3).

[0048] It is also important that the volume of the cavity is not excessively smaller so as not to increase the velocity of the particles too much. This is due to the fact that in the conical recess of the chamber, there is a minimum amount of powder, which is deposited so that a small conical mountain (previous slide: the powder rhombus) grows and distributes the rest of the particles that come later. If the particles are moving too fast, the cone-shaped mound is not produced and there is no longer any guarantee that the dust will be distributed evenly.

[0049] Figure 3 shows a laser cladding system (12) incorporating the powder distribution device (1) described previously, disposed in a perfectly vertical position with respect to ground. The system (12) also includes: a powder feeder (13) adapted to supply a flow of powder, and a laser head (14) including a nozzle (15) having two or more powder inlets (16). The powder distribution device (1) is fluidly communicated with the powder feeder (13) by means of a flexible hose (19), preferably an antistatic flexible hose, which is coupled to the inlet end (2a) of the rigid tube (2).

[0050] Two tubes (17, 17') communicates respectively the two outlet ducts (10, 10') with powder inlets (16,16') of the nozzle (15).

[0051] Figure 4 shows an alternative embodiment of a power distribution device (1) with three output ducts (10, 10', 10"), which are all equidistantly distributed around the powder accumulation surface (7) as better shown in Figures 4C & 4G, and all have the same inclination with respect to the axis (X) of the straight conduit (3).

[0052] Figure 5 shows an alternative embodiment of a power distribution device (1) with four outputs ducts (10, 10', 10", 10'") which are all equidistantly distributed around the powder accumulation surface (7) as better shown in Figures 4C & 4H, and all have the same inclination with respect to the axis (X) of the straight conduit (3).

[0053] As shown in all previous figures, the external surface of distribution head (5) has a chamfer or flat surface (18, 18', 18", 18"') for each one of the output ducts, such that each outlet duct ends in a flat surface, which facilitates connection of respective tubes to each output duct as represented in Figure 3.

Claims

CLAIMS1.- A powder distribution device (1) for a laser cladding equipment, the powder distribution device comprising: a straight conduit (3) for the passage of a flow of powder, the straight conduit (3) having an inlet end (3a) and an outlet end (3b), and a constant cross-sectional area between the inlet and outlet ends, a chamber (6) fluidly communicated with the outlet end (3b) of the straight conduit (3), wherein the cross-sectional area of the chamber (6) is larger than the cross-sectional area of the straight conduit (3), and wherein the chamber (6) has a powder accumulation surface (7) placed opposite the outlet end of the straight conduit (3), at least two outlet ducts (10,10') placed downstream the chamber (6) and fluidly communicated with the chamber (6), and wherein the outlet ducts (10,10') are arranged to diverge with respect to each other, so as to branch off powder accumulated in the chamber (6).2.- Powder distribution device according to claim 1, wherein all the outlet ducts (10,10') have the same volume and shape.3.- Powder distribution device according to claim 1 or 2, wherein both, the straight conduit (3) and the chamber (6) have a cylindrical configuration and are coaxially arranged.4.- Powder distribution device according to any of the preceding claims, wherein the powder accumulation surface (7), has a recess (11) for accumulating powder.5.- Powder distribution device according to claim 4, wherein the recess (11) has a conical configuration which is coaxially aligned with the axis of the straight conduit.6.- Powder distribution device according to any of the preceding claims, wherein the straight conduit (3) extends along an axis (X), and the outlet ducts (10,10') extent respectively along axes (Y, Y'), and wherein the axes (Y, Y') define the same angle (a) with respect to the axis (X), and wherein the angle (a) is within the range 30° - 45°.7.- Powder distribution device according to claim 6, wherein the outlet ducts (10,10') arearranged such that axes (Y, Y') intersect the axis (X) at a point placed above the powder accumulation surface (7).8.- Powder distribution device according to claim 3, wherein the ratio between the length of the straight conduit (3) and its diameter, is within the range 3% - 4%.9.- Powder distribution device according to any of the preceding claims, wherein the volume of the straight conduit (3) is larger than the volume of the chamber (6), preferably the ratio between the volume of the straight conduit and the volume of the chamber is 68%.10.- Powder distribution device according to any of the preceding claims, including more than two outlet ducts (10, 10', 10", 10"') equidistantly distributed around the powder accumulation surface (7).11.- Powder distribution device according to any of the preceding claims, wherein the straight conduit (3) is formed in a rigid tube (2), and wherein the chamber (6) and the outlet ducts (10, 10', 10", 10'") are formed in a distribution head (5) which is mechanically coupled to one end (2b) of the rigid tube (2), and wherein the outlet ducts (10, 10', 10", 10'") communicate the chamber (6) with the exterior of the distribution head (5).12.- Powder distribution device according to claim 11, wherein the external surface of the distribution head (5) has a flat surface (18, 18', 18", 18" ) for each one of the output ducts (10, 10', 10", 10"'), such that each outlet duct ends in a flat surface.13.- A laser cladding system (12), comprising: a powder feeder (13) adapted to supply a flow of powder, a laser head (14) including a nozzle (15) having two or more powder inlets (16,16'), and configured to produce a jet of powder, a powder distribution device (1) fluidly communicated with the powder feeder (13) and configured to branch off the flow of powder supplied by the powder feeder (13) into discrete flows of powder, two or more tubes (17,17') for communicating each discrete flow of powder with one powder inlet (16,16') of the nozzle (15), characterized in that, the powder distribution device (1) is the one defined in any of the preceding claims, and wherein the powder distribution device (1) is placed such that the straight conduit (3) is vertically arranged with respect to ground, so that powder may flow throughout the straightconduit (3) and get accumulated on the powder accumulation surface (7).14.- A laser cladding system according to claim 13, further comprising a flexible hose (19) communicating the powder feeder (13) with the powder distribution device (1).

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