阅读说明：本技术 同轴金属丝进给多激光金属沉积装置 (Coaxial wire feed multi-laser metal deposition device ) 是由 乔舒亚·A·克鲁斯 于 2018-12-07 设计创作，主要内容包括：一种同轴激光金属沉积头部,其包括金属丝引导件和多个激光光学单元。所述金属丝引导件限定金属丝引导件轴线。所述激光光学单元围绕所述金属丝引导件轴线分布。每个激光光学单元连接到单独的激光器,并且每个激光光学单元限定光束轴线。所述光学单元相对于所述金属丝引导件固定,并且在第一状态下定位成允许每个光束轴线在公共点处与所述金属丝引导件轴线相交。(A coaxial laser metal deposition head includes a wire guide and a plurality of laser optical units. The wire guide defines a wire guide axis. The laser optical units are distributed around the wire guide axis. Each laser optical unit is connected to a separate laser and each laser optical unit defines a beam axis. The optical unit is fixed relative to the wire guide and in a first state is positioned to allow each beam axis to intersect the wire guide axis at a common point.)

1. A coaxial laser metal deposition head comprising:

a wire guide defining a wire guide axis; and

a plurality of laser optical units distributed about the wire guide axis, each laser optical unit connected to a separate laser and each laser optical unit defining a beam axis, the optical units being fixed relative to the wire guide and the optical units being positioned in a first state to allow each of the beam axes to intersect the wire guide axis at a common point.

2. The head of claim 1, wherein the laser optical units are substantially evenly spaced about the wire guide axis.

3. The head according to claim 1, further comprising a mounting plate having:

a central portion having an aperture therethrough, the aperture being substantially concentric with the wire guide axis; and

a plurality of laser support arms aligned with the laser optics, extending outwardly from the central portion, and oriented at an obtuse angle with respect to the central portion,

wherein each of the laser optical units is fixed to one of the arms.

4. The head of claim 3, further comprising an articulated pivot mechanism disposed between and connecting one of the arms and the laser optic unit mounted on the one arm, the pivot mechanism defining a hinge axis and allowing the beam axis to move away from the common point.

5. The head of claim 4, the pivot mechanism including an adjustment screw spaced from the hinge axis, wherein operation of the pivot mechanism rotates the adjustment screw and pivots the laser optical unit about the hinge axis.

6. The head according to claim 5, further comprising a rotary indexing mechanism defining a rotational axis, the rotary indexing mechanism being arranged between and connecting one of the arms and the laser optical unit mounted on the one arm, the rotary indexing mechanism comprising a rotary indexing member and an electric motor drivingly connected with the rotary indexing member.

7. The head according to claim 1, further comprising a position adjustment mechanism disposed between the wire guide and one of the laser optical units.

8. The head of claim 1, wherein the wire guide is a tube for receiving a feed wire.

9. The head of claim 8 further comprising a feed channel connected to the wire guide at an angle to allow the wire guide to receive wire from the feed channel at an obtuse angle.

10. The head according to claim 5, further comprising a thermal shield disposed between the laser optical unit and a work surface.

11. A coaxial wire feed multi-laser metal deposition system comprising:

a head, the head comprising:

a mounting plate having:

a central portion having an aperture therethrough, the aperture defining a first axis substantially perpendicular to the central portion, and

a plurality of laser support arms extending outwardly from the central portion and oriented at an obtuse angle relative to the central portion,

a plurality of laser optical units equal in number to the laser support arms and mounted on each support arm, and each of the laser optical units is connected to a separate laser power supply unit, and each of the optical units defines a laser beam axis,

a wire guide fixed to the central portion and substantially coaxial with the first axis, an

A wire feed tip connected to the mounting plate,

and is substantially concentric with the first axis;

a robotic arm connected to the head; and

a controller connected to the robotic arm and the head.

12. The system of claim 11, wherein the plurality of arms is one of two, three, and four.

13. The system of claim 11, wherein the arms are substantially evenly spaced about the first axis.

14. The system of claim 11, further comprising a wire guide for receiving a feed wire, the wire guide having a wire guide axis substantially coaxial with the first axis, and the wire guide being secured to the central portion.

15. The system of claim 14, further comprising a feed channel connected to the wire guide at an angle to allow the wire guide to receive wire from the feed channel at an obtuse angle.

16. The system of claim 11, further comprising a heat shield disposed between the mounting plate and a work surface.

17. The system of claim 11, wherein the laser beam axis intersects the first axis at a common point under a first condition.

18. The system of claim 17, further comprising an articulation pivot mechanism disposed between and connecting one of the arms and a laser optical unit mounted on the one arm, the pivot mechanism defining a hinge axis and allowing the beam axis to move away from the common point.

19. The system of claim 18, the pivot mechanism including an adjustment screw spaced from the hinge axis, wherein operation of the pivot mechanism rotates the adjustment screw and pivots the laser optic unit about the hinge axis.

20. The system of claim 19, further comprising a rotary indexing mechanism defining an axis of rotation, the rotary indexing mechanism being disposed between and connecting one of the arms and a laser optical unit mounted on the one arm, and the rotary indexing mechanism comprising a rotary indexing member and an electric motor drivingly connected with the rotary indexing member.

Background

Laser metal deposition systems ("LMD systems") are used to build workpieces by depositing molten metal in subsequent layers to form the workpiece into a desired shape. LMD systems may use wire as the metal feed (i.e., "LMDw systems"). The LMDw system focuses the beam of laser light (i.e., the laser beam) on the work surface of the workpiece. The laser beam creates a molten metal pool into which the wire is fed. The wire is typically fed into the path of the laser beam and the melt pool at an acute angle to both the working surface and the laser beam. The coordinated and substantially constant relative motion between the workpiece surface and the laser beam and wire controls the shape of the workpiece to be built. This coordinated movement, which must be accommodated by the ability to properly position the laser and access the wire, is particularly challenging for certain geometries (e.g., corners). The coaxial system simplifies the synergy requirement by feeding the wire at an angle normal to the working surface. Known coaxial systems split the laser beam into three equal lower energy laser beams through laser optics to facilitate metal deposition with challenging geometries. The optics aim three laser beams at a common target, which are at an acute angle to the work surface and are evenly distributed around the axis defined by the wire feed. However, known coaxial systems are limited by laser optics and in some applications are not powerful enough to require more time to build the workpiece than desired. It is desirable to provide a more broadly useful coaxial LMDw system.

Drawings

FIG. 1 is a perspective view of an example embodiment of a coaxial laser metal deposition head.

Fig. 2 is a perspective view of the head of fig. 1.

Fig. 3 is a side view of the head of fig. 1 and an associated work plate.

Fig. 4 is a schematic diagram of an exemplary coaxial wire feed multi-laser metal deposition system including the head of fig. 1.

Fig. 5 is a perspective view of an example arm of the head of fig. 1.

FIG. 6 is an example usable target area of the head of FIG. 1.

Fig. 7 is a perspective view of the head of fig. 1 operating under a second exemplary condition.

Fig. 8 is a perspective view of the head of fig. 1 operating under a third example condition.

Detailed Description

Relative orientations and directions (e.g., upper, lower, bottom, forward, rearward, front, rear, back, lateral, medial, inward, outward, lateral, left, right) are set forth in this specification without limitation, but at least one embodiment of the described structure is depicted for the convenience of the reader. Such an example orientation is from the perspective of a passenger sitting in the seat and facing the instrument panel. In the drawings, like reference numerals designate like parts throughout the several views.

The coaxial laser metal deposition head includes a wire guide and a plurality of laser optical units. The wire guide defines a wire guide axis. The laser optical units are distributed around the wire guide axis. Each laser optical unit is connected to a separate laser and each laser optical unit defines a beam axis. The optical unit is fixed relative to the wire guide and in a first state is positioned to allow each beam axis to intersect the wire guide axis at a common point.

The laser optical units may be substantially evenly spaced about the wire guide axis.

The head may also include a mounting plate having a central portion and a plurality of laser support arms. The central portion may have an aperture therethrough substantially concentric with the wire guide axis. A plurality of laser support arms can be aligned with the laser optics unit and extend outwardly from the central portion, and the plurality of laser support arms can be oriented at an obtuse angle relative to the central portion. Each of the laser optical units may be fixed to one of the arms.

The head may further include a hinge pivot mechanism disposed between and connecting one of the arms and the laser optical unit mounted thereon. The pivot mechanism may define a hinge axis and allow the beam axis to move away from the common point.

The head may include an adjustment screw spaced from the hinge axis. Operation of the pivot mechanism rotates the adjustment screw, causing the laser optical unit to pivot about the hinge axis.

The head may further include a rotary indexing mechanism defining an axis of rotation. The rotary indexing mechanism may be disposed between and connect one of the arms and the laser optical unit mounted on the one arm. The rotary indexing mechanism may comprise a rotary indexing member and an electric motor drivingly connected thereto.

The head may include a position adjustment mechanism disposed between the wire guide and one of the laser optical units.

The wire guide may be a tube for receiving the feed wire.

The head may further include a feed channel connected to the wire guide at an angle to allow the wire guide to receive wire from the feed channel at an obtuse angle.

The head may further comprise a thermal shield arranged between the laser optical unit and the working surface.

The coaxial wire-feed multi-laser metal deposition system can include a head, a robotic arm, and a programmable computing device. The head may also include a mounting plate, a plurality of laser optical units, a wire guide, and a wire feed tip. The mounting board may include a central portion and a plurality of laser support arms. The central portion may have an aperture therethrough. The aperture through the central portion may define a first axis substantially perpendicular to the central portion. The laser support arms may extend outwardly from the central portion and be oriented at an obtuse angle relative to the central portion. The laser optical units may be equal in number to the laser support arms and may be mounted on the respective support arms. Each of the laser optical units may be connected to a separate laser power supply unit, and each of the optical units may define a laser beam axis. The wire guide may be fixed to the central portion and substantially coaxial with the first axis. The wire feed tip may be coupled to the mounting plate and substantially concentric with the first axis. A robotic arm may be connected to the head. A programmable computing device may be connected to the robotic arm and the head.

The plurality of arms of the system may be one of two, three and four.

The arms of the system may be substantially evenly spaced about the first axis.

The system may further comprise a wire guide for receiving the feed wire. The wire guide may have a wire guide axis substantially coaxial with the first axis. The wire guide may be fixed to the central portion.

The system may further include a feed channel connected to the wire guide at an angle to allow the wire guide to receive the wire from the feed channel at an obtuse angle.

The system may also include a heat shield disposed between the mounting plate and the work surface.

The laser beam axis of the system may intersect the first axis at a common point under a first condition.

The system may further include an articulation pivot mechanism disposed between and connecting one of the arms and the laser optical unit mounted on the one arm. The pivot mechanism may define a hinge axis and allow the beam axis to move away from the common point.

The pivot mechanism of the system may include an adjustment screw spaced from the hinge axis. Operation of the pivot mechanism may rotate the adjustment screw to pivot the laser optic unit about the hinge axis.

The system may further comprise a rotary indexing mechanism defining a rotation axis, the rotary indexing mechanism being arranged between and connecting one of the arms and the laser optical unit mounted on the one arm. The rotary indexing mechanism may comprise a rotary indexing member and an electric motor drivingly connected thereto.

An example coaxial laser metal deposition head 10 of a coaxial wire feed multiple laser deposition system 12 is shown in fig. 1-8.

As best shown in fig. 4, the head 10 includes a plurality of laser units 13A, 13B and 13C and a wire feed tip 14. In operation, the head 10 is positioned relative to a work surface 15, which may be defined by a workpiece 16 formed on a work plate 17. To facilitate such positioning, head 10 may be configured for mounting at the end of robotic arm 18. Robotic arm 18 may position head 10 relative to work plate 17. The system 12 may also include a heat shield 19, a wire feeder (not shown), a work plate positioning mechanism (not shown), a system controller 20, and a robot control link 24 between the controller 20 and the robot arm 18, the system controller 20 being a programmable computing device for controlling the operation of the system 12, such as positioning the head 10, positioning the work plate 17, positioning the laser units 13A, 13B, 13C, establishing a wire feed rate of the feed wire 22, in response to computer instructions (i.e., computer software). The controller 20 may include both a memory for storing instructions and a processor for executing instructions. The laser units 13A, 13B, 13C may each be a laser optical unit connected to its own laser power unit 26A, 26B, 26C by an optical fiber 28A, 28B, 28C. Alternatively, the laser units 13A, 13B, and 13C may integrate the laser power units 26A, 26B, 26C. A control cable 30A, 30B, 30C may connect each laser power unit 26A, 26B, 26C with the controller 20.

Head 10 includes a mounting plate 32. The plurality of laser units 13A, 13B, and 13C are fixed to the plate 32. The exemplary number of laser units 13A, 13B, and 13C is three, but alternatively, may be two or four. The wire guide 34 is secured to the mounting plate 32. The wire guide 34 defines a wire guide axis 36, as best shown in fig. 1. The laser units 13A, 13B and 13C may be evenly spaced about the axis 36, for example 120 ° apart for three units 13A, 13B and 13C.

Mounting board 32, best shown in fig. 2, may include a plurality of integrally formed laser support arms 38A, 38B, and 38C, one for each laser unit 13A, 13B, and 13C. The arms 38A, 38B, and 38C may extend radially from a substantially planar central portion 40 of the mounting plate 32. The number of support arms 38A, 38B, and 38C may be equal to the number of laser units 13A, 13B, and 13C. The arms 38A, 38B, and 38C may be at obtuse angles relative to the central portion 40 on the medial sides 42A, 42B, 42C, respectively.

The plate 32 includes a central aperture 44 through the central portion 40, the central aperture 44 being coaxial with the wire guide axis 36. Mounting bosses 46 surround the apertures 44 and may be disposed on the same side of the plate 32 as the inner sides 42A, 42B, 42C.

The wire guide 34 may include a wire feed channel 48 coupled to the wire guide 34 to allow the feed wire 22 to enter the wire guide 34. The channel 48 may be in the form of a tube having an internal passageway that connects to the internal passageway within the wire guide 34. The channel 48 may be connected to the guide 34 at an angle β relative to the wire guide axis 36, where the angle β is an obtuse angle. The angle β facilitates transfer of the feed wire 22 from the channel 48 to the guide 34, helping to reduce the risk of the wire 22 becoming stuck and entangled as the wire 22 is fed to the work surface 15 of the workpiece 16.

First position adjustment mechanisms, such as hinge pivot mechanisms 50A, 50B, 50C, may be disposed between each laser unit 13A, 13B, 13C and the support arms 38A, 38B, 38C. The example hinge pivot mechanisms 50A, 50B, 50C may include axial displacement mechanisms 54A, 54B, 54C, such as micrometer-type fine pitch adjustment screws 54A, 54B, 54C in combination with the hinge 52. An alternative embodiment of an axial displacement mechanism 54 'is shown in fig. 5, which forms part of a pivot mechanism 50' that may be mounted on each arm 38A, 38B, 38C. The displacement mechanism 54 'may include an electrically operated actuator to drive the adjustment screw 55' in response to an electrical command signal from the controller 20.

The hinge 52, best shown in fig. 5, may have a pair of hinge plates 56, with one hinge plate 56 connected to the optical units 13A, 13B, 13C and the other hinge plate 56 connected to the respective arms 38A, 38B, 38C. The hinges 52 on each arm 38A, 38B, 38C define a hinge axis 58A, 58B, 58C about which the optical unit 13A, 13B, 13C can pivot relative to the arm 38A, 38B, 38C. The hinge axis 58A, 58B, 58C may be at an end of the arm 38A, 38B, 38C opposite the position of the axial displacement mechanism 54', 54A, 54B, 54C. These figures show the axial displacement mechanisms 54', 54A, 54B, 54C near the ends of the arms 38A, 38B, 38C that are distal from the central portion 40, and the hinge axes 58A, 58B, 58C near the opposite ends of the arms 38A, 38B, 38C that are proximal to the central portion 40. Alternatively, the axial displacement mechanisms 54', 54A, 54B, 54C may be proximate the ends of the arms 38A, 38B, 38C proximate the central portion 40, and the hinge axes 58A, 58B, 58C may be proximate the ends of the arms 38A, 38B, 38C distal the central portion 40. The hinge 52 may be of any type that allows pivoting about the axes 58A, 58B, 58C, such as a pin hinge and a living hinge. The displacement of the screws 54A, 54B, 54C, 55' causes the optical units 13A, 13B, 13C to pivot about the axes 58A, 58B, 58C.

A second position adjustment mechanism, for example a rotary indexing mechanism such as the example mechanism 60 shown on arm 38A in fig. 5, may also be provided between each optical unit 13A, 13B, 13C and the associated arm 38A, 38B, 38C to provide a second degree of freedom to each unit 13A, 13B, 13C relative to arm 38A, 38B, 38C. The rotary indexing mechanism 60 may comprise a rotary indexing member 64 (e.g. a plate or shaft) arranged between the optical units 13A, 13B, 13C and the arms 38A, 38B, 38C. The indexing member 64 is rotatable about rotational axes 62A, 62B, 62C. The rotational axis 62A, 62B, 62C may be orthogonal to one of the arms 38A, 38B, 38C and the hinge plate 60 on which the rotational indexing mechanism 60 is mounted. The rotary indexing mechanism 60 may include teeth 65 on the outer diameter of the indexing member 64, the teeth 65 engaging a worm (not shown). The rotational position of the indexing member 64 relative to the arm 38A and one of the optical units 13A, 13B, 13C may be changed by manually rotating a worm or by actuating an electric motor, which may be part of the mechanism 60, to drive a screw. An exemplary alternative on-the-shelf rotary indexing mechanism is found in the rotary actuators available from pi (physik instruments) l.p. of austacher, ma, usa, and particularly in the actuator families of their UPR-100, UPR-120 and UPR 160. The rotary indexing mechanism may have a maximum rotational displacement rate of 90 degrees/second to 720 degrees/second.

The adjustment mechanisms 50, 50', 60 may be connected to the controller 20 via a communication link. Fig. 4 shows a plurality of connecting communication cables 67A, 67B, 67C as exemplary links. Alternatively, the communication link may be provided by a multiplexed network or wirelessly (e.g., bluetooth).

The arms 38A, 38B, 38C, best shown in FIG. 2, are provided with a plurality of mounting apertures 66A, 66B, 66C. The apertures 66A, 66B, 66C may include apertures for connecting any of the laser units 13A, 13B, 13C, the pivot mechanisms 50A, 50B, 50C, or the rotary indexing mechanism 60 (e.g., rotary indexing member) to the arms 38A, 38B, 38C. While the apertures 66A, 66B, 66C are shown as through holes, they may alternatively be blind holes, or may be threaded.

Each laser optical unit 13A, 13B, 13C defines a laser beam axis 68A, 68B, 68C, respectively. The laser beams emitted by the optical units 13A, 13B, 13C follow the axes 68A, 68B, 68C. Pivoting the laser optics units 13A, 13B, 13C about the hinge axes 58A, 58B, 58C changes the angles γ a, γ B, γ C between the laser beam axes 68A, 68B, 68C and the wire guide axis 36, respectively.

In a first condition, where γ A, γ B, γ C are common values, the laser beam axes 68A, 68B, 68C all intersect the wire guide axis 36 at a common point 70. The common point 70 may be adjusted along the wire guide axis 36 by uniformly adjusting the pivot mechanisms 50A, 50B, 50C to change the value of γ a, γ B, γ C equally for all optical units 13A, 13B, 13C, in combination with the adjustment of the focal length of the optical units 13A, 13B, 13C. This adjustment of the focal length can be achieved electronically with an electronic focal length actuator (not shown) integrated into each optical unit 13A, 13B, 13C. A rotary indexing mechanism 60 may be used to further change the orientation of the laser beam axes 68A, 68B, 68C relative to the wire guide axis 36.

The heat shield 19 may include a reflector plate 72 and a heat sink portion 74. The heat sink portion 74 may be a cold liquid (e.g., water) having a flow rate selected to maintain the temperature within a predetermined range. The heat sink portion 74 may also be integrated into the mounting plate 32. The reflective plate 72 may include a beam aperture (not shown) to allow passage of the laser beam from the laser optical unit 13A, 13B, 13C along the axis 68A, 68B, 68C to the working surface 15.

Robotic arm 18 may be connected to head 10 by wrist manipulator 76. Manipulator 76 allows multiple degrees of rotational freedom in the orientation of head 10, thereby facilitating selective positioning of common point 70. Such manipulators 76 are commercially available.

The system 12 may be used as a three-dimensional printer to form a metal part, i.e., the workpiece 16, from the feed wire 22. The feed wire 22 is received by the channel 48, fed out of the tip 14 through the guide 34, and onto the work surface 15. The feed rate of the feed wire 22 through the tip 14 may be controlled by commands from the controller 20, which are communicated to a wire feeder (not shown). The feed rate of the feed wire 22 into the melt pool on the work surface 15 (e.g., 1 to 10 meters per minute) may depend on a variety of system parameters, including the diameter of the feed wire 22, e.g., 0.5 to 2.0 millimeters, and the maximum available power range of the laser units 13A, 13B, 13C. These commands may be generated by a controller processor executing instructions stored in a memory of the controller.

The system 12 may be operated in a substantially coaxial mode, wherein all of the laser units 13A, 13B, 13C are directed to a common point 70, wherein the common point 70 is on the working surface 15 and coincides with the melt pool. With the laser beam axes 68A, 68B, 68C thus oriented, the feed wire 22 melts on the work surface 15 to form a weld bead 77, i.e., a layer, on the earlier work surface of the workpiece and, in the case of the first layer, on the work plate 18. The substantially coaxial mode of operation is particularly advantageous for forming complex patterns with head 10.

The use of individual laser units 13A, 13B, 13C allows a larger amount of net laser power to be used. The rate at which the object can be formed by the LMD process, i.e., the rate at which metal can be fed to the work surface 15 and melted, depends on the amount of laser power available to melt the incoming feed wire 22. A head using a single laser rated at 4 kw in combination with a three-way splitter may be limited to being formed at a rate allowed by 4 kw or less of power. The use of separate multiple laser units 13A, 13B, 13C without the need for a beam splitter allows more laser energy to be applied to the working surface 15. For example, where the three laser units 13A, 13B, 13C are each rated at 25 kilowatts, the net energy available at the work surface 15 becomes 75 kilowatts. Alternatively, for example, in forming relatively thin-walled parts, lower power laser units 13A, 13B, 13C may be selected as required by the system formation, for example, laser units having a power range between 1000 watts and 10,000 watts. Multi-laser system 12, while its combined laser is capable of providing more concentrated power than a beam splitting system, can be used to form larger parts in fewer time slices (e.g., one-tenth) than would be required to form a part with a beam splitting system.

The controlled movement of the optical units 13A, 13B, 13C about their respective hinge axes 58A, 58B, 58C and rotation axes 62A, 62B, 62C allows the laser beam axes 68A, 68B, 68C to reach any point within the respective available target areas 78A, 78B, 78C of the example best shown in fig. 6. The target areas 78A, 78B, 78C partially overlap adjacent target areas 78A, 78B, 78C. The target areas 78A, 78B, 78C are shown as not extending beyond the common point 70 to avoid intersecting the feed wire 22 above the common point 70. The only location where the target regions 70A, 70B, 70C all overlap one another is at a common point 70. The target areas 78A, 78B, 78C and the amount of area overlap may be increased by allowing the beam axes 68A, 68B, 68C to move past the common point 70. When the beam axes 68A, 68B, 68C extend past the common point 70, the controller 20 can be programmed to reduce the power to or turn off the laser units 13A, 13B, 13C when their beam axes 68A, 68B, 68C are directed toward the feed wire 22 above the common point 70, thereby avoiding accidental severing of the feed wire 22 or damage to the tip 14. The shield 19 must also be configured to allow possible paths for the laser beam.

By actuating the adjustment mechanisms 50A, 50B, 50C and 60 into alternative non-coaxial arrangements, the point at which the beam axis 68A, 68B, 68C intersects the work surface 15 can be adjusted. For example, as shown in fig. 7, the beam axis 68A may be directed toward the common point 70, the beam axis 68B may be directed toward the second point 80 after the common point 70, and the beam axis 68C may be directed toward the third point 82 after the second point 80, and all three points 70, 80, 82 may be on a common weld bead line 84.

The above trailing spot arrangement allows for the alternating use of individual laser beams, thereby improving control and quality of the metal deposition process. For example, the cooling rate of the molten bath may be controlled to achieve stepped cooling by operating the laser unit 13B directed to the second point 80 at a lower power level than the laser unit 13A directed to the common point 70, and operating the laser unit 13C directed to the third point 82 at a lower power level than the laser unit 13B. Alternatively, the power of the trailing laser units 13A, 13C may be selectively increased to correct for the detected defects in response to a weld bead quality sensor (not shown), such as an X-ray emitter/sensor, detecting the defects in the just-laid weld bead. The weld bead quality sensor is connected to the controller 20 for electronic communication therewith.

In yet another alternative positioning scheme shown in fig. 8, as a default condition, the laser units 13A, 13B, 13C may be selectively positioned to all focus on a common spot 70. In response to detecting a defect in the just laid bead, one of the laser units 13C may direct its beam axis 68C at the defect at the second point 80 on the bead line 84 to re-melt the bead at the defect to correct the defect.

The system 12 may operate according to the following steps. A virtual model of the workpiece 16 is created with the software code. The virtual model may be loaded into the controller 20 and stored in the memory of the controller. The controller 20 is programmed with instructions, also stored in the controller's memory, to build the workpiece 16 according to the virtual model. The feed wire 22 is selected to provide the appropriate gauge and type of metal (e.g., titanium, steel, aluminum) consistent with the design of the workpiece 16. The feed wire 22 is loaded into the wire feeder with one end passing through the wire feed channel 48, into the wire guide 34 and out through the tip 14. Robotic arm 18 positions the head and more particularly head 14 at the beginning of work plate 17. The starting point is selected such that the workpiece 16 will fit on the work plate 17.

The work plate 17 may be fixed to the ground and remain stationary throughout the process of building the workpiece 16. Alternatively, the work plate 17 may be connected to a positioning device, such as a robotic arm, to allow the work plate 17 to move relative to the head 10. Because gravity can be utilized to provide a force that biases a new weld bead against the workpiece 16, relative movement of the workpiece 17 can change the angle between adjacent surfaces of the workpiece 16, allowing more complex shaped workpieces 16 to be built.

The build of the workpiece 16 begins at the start point. The starting point is the initial position of the common point 70. The laser optics units 13A, 13B, 13C may have their beam axes 68A, 68B, 68C all directed to a common point 70. In response to instructions from the controller 20, the laser power units 26A, 26B, 26C are energized, thereby melting the wire 22 and beginning to form the workpiece 16 with a first weld bead as the head 10 moves relative to the work plate 17.

As shown in FIG. 8, and as described above, one of the laser optics units (e.g., 13C) may have its beam axis 68C turned from the common point 70 to re-melt the freshly laid weld bead to correct any defects that may be sensed by the bead quality sensor. The controller 20 may modulate the power to the laser power cells 26A, 26B, 26C as appropriate for the manufacturing requirements. To achieve this modulation, the controller 20 may vary the power distribution among the power cells 26A, 26B, 26C, where each power cell receives a different amount of power than the other power cells, or receives the same power. Thus, the workpiece 16 may be formed at least in part by: one of the laser optical units 13C is repositioned to direct its beam axis 68C to a point 80 on the weld bead line 84 of the workpiece 16 that is different from the point 70 on the weld bead line 84 to which the other laser beam axes 68A, 68B are directed.

As shown in fig. 7, and as described above, beam axes 68A, 68B, 68C may all be directed at different points 70, 80, 82 along line 84 to achieve a managed cooling rate of the freshly laid metal bead (i.e., layer) of metal, and also to correct any detected defects. When operating as shown in fig. 7, the controller 70 may select a different one of the laser optic units 13A, 13B, 13C to have its beam axis 68A, 68B, 68C directed to a common point 70 when there is a change in direction of the opposing head 10 — work plate 17. The ability to reposition axes 68A, 68B, 68C, combined with the ability of wrist manipulator 76 to rotationally reposition head 10, allows system 12 to orient beam axes 68A, 68B, and 68C substantially continuously along line 84 on work surface 15, even if the work surface includes more complex geometric transitions (e.g., sharp corners) that require more complex manipulation of head 10. Thus, the workpiece 16 may be formed at least in part by: one of the laser optical units 13C is repositioned so that its beam axis 68C is directed to a point 82 on a bead line 84 of the workpiece 16, which point 82 is different from the points 70, 80 on the bead line 84 directed by the other laser beam axes 68A, 68B. The workpiece 16 may also be formed by: each laser optical unit 13A, 13B, 13C is selectively repositioned such that the associated laser beam axis 68A, 68B, 68C is directed to a separate (i.e., a distance apart) point 70, 80, 82 on the bead line 84.

The adverb "substantially" as used herein means that there may be deviations from the precise geometry, distances, measurements, quantities, times, etc., described due to imperfections in the material, machining, manufacturing, data transmission, computational speed, etc.

The disclosure has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present disclosure are possible in light of the above teachings, and the disclosure may be practiced otherwise than as specifically described. The separate embodiments explicitly disclosed are exemplary and are not intended to limit the embodiments and combinations of features thereof.