Laser metal wire deposition

Abstract

A wire dispenser for a laser metal wire deposition machine comprises a longitudinal duct for guiding a wire from a proximal end to a distal end of the duct. A nozzle unit is connected to the distal end of the duct and has a through bore for receiving the wire from the distal end of the duct and for discharging the wire adjacent to a laser metal wire deposition site. The nozzle unit includes a cooling circuit for a cooling liquid.

Claims

1. A wire dispenser for a laser metal wire deposition machine, the wire dispenser comprising: a longitudinal duct for guiding a wire from a proximal end to a distal end of the duct; and a nozzle unit connected to the distal end of the duct and having a through bore for receiving the wire from the distal end of the duct and for discharging the wire adjacent to a laser metal wire deposition site; wherein the nozzle unit includes a cooling circuit for a cooling liquid; the nozzle unit includes a metal front block positioned laterally of a front portion of the through bore of the nozzle unit and a rear cooling portion positioned laterally of a rear portion of the through bore of the nozzle unit and rearwardly of the front block; the rear cooling portion of the nozzle unit contains the cooling circuit; the metal front block and the rear cooling portion form a sleeve-like device which is removably fitted onto a metal nozzle which contains the through bore for the wire; the metal nozzle is of a replaceable type which is removable from the distal end of the duct; the sleeve-like device has a sleeve bore extending from a rear face of the rear cooling portion to a front face of the front block and the metal nozzle is seated in the sleeve bore; and the longitudinal position of the metal nozzle in the sleeve bore is such that a front tip of the metal nozzle is within a range of plus 1 millimeter to minus 5 millimeters from the front face of the front block.

2. The wire dispenser according to claim 1, wherein the rear cooling portion has a circumferential line of contact with the metal nozzle.

3. The wire dispenser according to claim 1, wherein a volume of metal of the metal front block is greater than a volume of metal of a part of the metal nozzle which is seated within the metal front block.

4. The wire dispenser according to claim 1, wherein the metal nozzle obstructs the sleeve bore.

5. The wire dispenser according to claim 1, wherein the cooling circuit of the nozzle unit has an inlet and an outlet at a rear face of the nozzle unit, and a coolant liquid inlet pipe is connected to the inlet and a coolant liquid outlet pipe is connected to the outlet.

6. The wire dispenser according to claim 1, wherein a cooling jacket having a cooling circuit is positioned around the duct, and the cooling circuit of the cooling jacket is connected to the cooling circuit of the nozzle unit.

7. A laser metal wire deposition machine comprising a laser unit defining a laser beam axis; and a wire dispenser, the wire dispenser including a longitudinal duct for guiding a wire from a proximal end to a distal end of the duct; and a nozzle unit connected to the distal end of the duct and having a through bore for receiving the wire from the distal end of the duct and for discharging the wire adjacent to a laser metal wire deposition site; wherein the nozzle unit includes a cooling circuit for a cooling liquid; the nozzle unit includes a metal front block positioned laterally of a front portion of the through bore of the nozzle unit and a rear cooling portion positioned laterally of a rear portion of the through bore of the nozzle unit and rearwardly of the front block; the rear cooling portion of the nozzle unit contains the cooling circuit; the metal front block and the rear cooling portion form a sleeve-like device which is removably fitted onto a metal nozzle which contains the through bore for the wire; the metal nozzle is of a replaceable type which is removable from the distal end of the duct; the sleeve-like device has a sleeve bore extending from a rear face of the rear cooling portion to a front face of the front block and the metal nozzle is seated in the sleeve bore; and the longitudinal position of the metal nozzle in the sleeve bore is such that a front tip of the metal nozzle is within a range of plus 1 millimeter to minus 5 millimeters from the front face of the front block; and wherein the through bore of the nozzle unit of the wire dispenser defines a wire dispensing axis; and the laser beam axis and the wire dispensing axis meet at the laser metal wire deposition site.

8. The laser metal wire deposition machine according to claim 7, wherein the wire dispenser is provided as part of an arm which is attached to a side of the laser unit.

9. The laser metal wire deposition machine according to claim 7, wherein a gas chamber contains the laser unit, the wire dispenser and a jig for supporting a workpiece.

10. A wire dispenser for a laser metal wire deposition machine, the wire dispenser comprising: a longitudinal duct for guiding a wire from a proximal end to a distal end of the duct; a metal nozzle connected to the distal end of the duct and having a through bore for receiving the wire from the distal end of the duct and for discharging the wire adjacent to a laser metal wire deposition site; and a thermal control device in the form of a sleeve which is removably fitted onto the metal nozzle; wherein the thermal control device includes a cooling circuit for a cooling liquid; a nozzle unit includes the metal nozzle and the thermal control device; the nozzle unit includes a metal front block positioned laterally of a front portion of the through bore of the nozzle unit and a rear cooling portion positioned laterally of a rear portion of the through bore of the nozzle unit and rearwardly of the front block; the rear cooling portion of the nozzle unit contains the cooling circuit; the metal front block and the rear cooling portion form the sleeve which is removably fitted onto the metal nozzle; the metal nozzle is of a replaceable type which is removable from the distal end of the duct; the sleeve has a sleeve bore extending from a rear face of the rear cooling portion to a front face of the front block and the metal nozzle is seated in the sleeve bore; and the longitudinal position of the metal nozzle in the sleeve bore is such that a front tip of the metal nozzle is within a range of plus 1 millimeter to minus 5 millimeters from the front face of the front block.

11. The wire dispenser according to claim 10, wherein the sleeve bore of the thermal control device has a rear bore portion which is in thermal contact with a rear portion of the metal nozzle and a front bore portion which surrounds a tapered front portion of the metal nozzle with an annular gap therebetween.

12. The wire dispenser according to claim 11, wherein the rear bore portion is in thermal contact around a full circumference of the rear portion of the metal nozzle.

13. The wire dispenser according to claim 10, wherein the thermal control device is asymmetrically positioned around the metal nozzle.

14. The wire dispenser according to claim 10, wherein: the front face of the metal front block comprises a first portion which is substantially perpendicular to the longitudinal axis of the metal nozzle and which surrounds the front tip of the metal nozzle and a second portion which is rearwardly inclined and is offset laterally relative to the longitudinal axis of the metal nozzle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Some embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:—

(2) FIGS. 1A to 1C show a manufacturing cell of the prior art for performing laser metal wire deposition (LMDw) on a fan case mount ring. FIG. 1A is an overall perspective view, and FIGS. 1B and 1C are more-detailed perspective views.

(3) FIG. 2 is a diagrammatic representation of a prior art tool configuration at an LMDw site.

(4) FIG. 3 is a diagrammatic representation of an LMDw machine, in which the wire dispenser is shown in cross-section.

(5) FIGS. 4-8 show another example wire dispenser. FIG. 4 is a perspective front view.

(6) FIG. 5 is a side view. FIG. 6 is a plan view. FIG. 7 is a longitudinal sectional view. FIG. 8 is longitudinal sectional view similar to FIG. 7 but with some of the sectional detail depicted in solid to make some of the internal features easier to see.

(7) While the presently claimed invention is susceptible to various modifications and alternative forms, some embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description of these embodiments are not intended to limit the invention to the particular forms disclosed. On the contrary, the invention covers all modifications, equivalents and alternatives falling within the spirit and the scope of the present invention as defined by the appended claims. In addition the invention covers not only individual embodiments but also combinations of the embodiments described.

DESCRIPTION

(8) FIG. 3 shows, in diagrammatic form, an example LMDw machine, wherein nozzle tip cooling is retro-fitted onto an existing metal (e.g. copper) nozzle 5.

(9) As shown in FIG. 3, the nozzle 5 is arranged to discharge a metal wire 4 along a wire dispensing axis 41 towards an LMDw site 16 on a workpiece 14 which is mounted on a jig 15. For the sake of visual clarity, only portions 4A, 4B of the wire 4 are shown, although in reality the wire 4 is continuous and extends to the LMDw site 16.

(10) A laser unit 2 is used to emit a laser beam 21 along a laser beam axis 22 to intersect with the wire 4 at the LMDw site 16.

(11) The nozzle 5 has a through bore 51 which has a front portion 511 and a rear portion 512. The wire 4 extends through the bore 51.

(12) A rear portion 52 of the nozzle 5 has a cylindrical outer surface and a front portion 53 has a tapered outer surface which leads to a front tip 54.

(13) The nozzle 5 forms part of a nozzle unit 6. The other component of the nozzle unit 6 is a thermal control device 7 which serves to cool the nozzle 5 and to shield the nozzle 5 from the heat radiated from the LMDw site 16 and from laser light reflected from the workpiece 14. To assist with reflecting away the laser light, the external surface of the thermal control device 7 may be polished to make it reflective.

(14) The thermal control device 7 is made of metal (e.g. copper) and has a sleeve-like shape with a sleeve bore 71 which extends from a rear face 72 to a front face 73 of the device 7. The nozzle 5 is received in the sleeve bore 71. In FIG. 3, for reasons of clarity of depiction, a gap is shown between the rear portion 52 of the nozzle 5 and a rear bore portion 74 of the sleeve bore 71. In reality, the rear bore portion 74 of the sleeve bore 71 forms a close fit with the rear portion 52 of the nozzle 5 to provide thermal conduction between the nozzle 5 and the device 7.

(15) A front bore portion 75 of the sleeve bore 71 is spaced away from the tapered front portion 53 of the nozzle 5 and an annular gap 61 is present therebetween.

(16) The thermal control device 7 has the form of a body which is separated into a solid-metal front block 76 and a hollow rear cooling portion 77. The rear cooling portion 77 is hollow because is contains an internal passageway 771 which functions as a cooling circuit having an inlet 771A and an outlet 771B. A coolant liquid inlet pipe 78 is soldered to the inlet 771A and a coolant liquid outlet pipe 79 is soldered to the outlet 771B. Each pipe 78, 79 has an internal diameter of 4 mm and an external diameter of 6 mm.

(17) A longitudinal duct 8 has a proximal (inlet or rear) end 81 for receiving the wire 4 and a distal (outlet or front) end 82 for discharging the wire 4. The distal end 82 is releasably connected (e.g. screw threadedly connected) to the rear portion 52 of the nozzle 5 and is arranged to feed the wire 4 into the through bore 51 of the nozzle 5.

(18) The wire 4 may be advanced (fed forwards) by any suitable mechanism (not shown) such as pinch rollers or a pneumatic wire delivery mechanism.

(19) A cooling jacket 83 with a cooling circuit 84 is positioned around a main tube 85 of the duct 8. The cooling circuit 84 may be connected to the cooling circuit 771 so that they function as one circuit, or the two cooling circuits 84, 771 may function independently.

(20) The nozzle unit 6 (comprising the nozzle 5 and the thermal control unit 7) and the duct 8 form a wire dispenser 9.

(21) The wire dispenser 9 is supported at one side of the laser unit 2 by means of a support arm 23 which extends from the laser unit 2 to any convenient part of the wire dispenser 9.

(22) It is desirable for the mass (the thermal mass) of metal of the front block 76 of the thermal control unit 7 to be large enough to act as an effective heat sink. Thus, the mass of metal of the front block 76 may be selected to be greater (e.g. at least two times greater, or at least three times greater) than the mass of the metal of that part of the nozzle 5 present inside the front portion 75 of the sleeve bore 71 provided inside the front block 76.

(23) Heat absorbed by the front block 76 may pass rearwardly to the rear cooling portion 77, and then be carried away by the cooling circuit 771. Heat absorbed at and adjacent to the front tip 54 of the nozzle 5 may pass via the rear portion 52 of the nozzle 5 to the rear cooling portion 77, and then be carried away by the cooling circuit 771.

(24) For a laser unit 2 emitting a 6 kW laser beam 21, the inlet temperature of the coolant liquid (e.g. water) received by the cooling circuit 771 may be 20° C. (plus or minus 2° C.) and the flow rate of the coolant may be 0.2 to 0.3 m.sup.3/hour.

(25) In this way, the temperature of the nozzle 5 may be controlled to be kept below the temperature at which the metal of the front tip 54 of the nozzle 5 might start to melt.

(26) The wire dispenser 9, laser unit 2 and the jig 15 (with its workpiece 14) form a machine which is typically contained inside a chamber or tent (not shown) which is filled with an inert gas such as argon during the deposition process on the workpiece 14.

(27) Because of the effective tip cooling of the nozzle 5 provided by the thermal control unit 7, the nozzle 5 can be prevented from melting for long periods such that the need to replace a melted nozzle can be largely eliminated. This increases the productivity of the LMDw machine. For example, time is not wasted in venting the argon and re-filing the chamber or tent with argon when changing a damaged (melted) nozzle.

(28) It is also envisaged that the effective tip cooling will mean that the power of the laser beam 21 may be increased which would increase productivity by increasing the deposition rate. The feed rate of the wire 4 would be increased commensurately.

(29) The thermal control unit 7 is asymmetrically shaped relative to the nozzle 5, with the majority of the body of the unit 7 being above the nozzle 5 and remote from the workpiece 14. Thus, the nozzle 5 should not be restricted in being able to approach closely the workpiece 14 during the deposition process.

(30) A top front corner of the body of the thermal control unit 7 is chamfered to reduce the risk of clashing with the laser beam 21. The front face 73 has a first portion 731 around the sleeve bore 71 which is perpendicular to the axis 41 and a second (upper) portion 732 which is above the first portion 731 and inclined rearwardly.

(31) FIGS. 4-8 show a version of a wire dispenser 9 which forms another embodiment.

(32) FIG. 4 is a perspective front view. FIG. 5 is a side view. FIG. 6 is a plan view. FIG. 7 is a longitudinal sectional view. FIG. 8 is longitudinal sectional view similar to FIG. 7 but with some of the sectional detail depicted in solid to make some of the internal features easier to see.

(33) FIGS. 7 and 8 show a variation compared with the wire dispenser 9 of FIG. 3. In FIGS. 7 and 8, the sleeve bore 71 of the thermal control unit 7 is not cylindrical along its full length. The rear bore portion 74 is cylindrical, but the front bore portion 75 is tapered in the forward direction to match the tapering of the front portion 53 of the nozzle 5.

(34) FIGS. 7 and 8 also show how the nozzle tip 54 is substantially flush with the first portion 731 of the front face 73. Alternatively, the nozzle tip 54 may protrude slightly or be recessed slightly.

(35) In relation to the embodiment of FIGS. 4 to 8, it may be seen that the nozzle 5 is effectively shielded by the thermal control unit 7.

(36) The nozzle tip 54 is cooled by being surrounded with the cooling effect provided by the thermal control unit 7, and the nozzle 5 may be prevented from melting. By supplying chilled water to the thermal control unit 7 at a suitable temperature and flow rate, the desired amount of cooling may be achieved taking into account the power of the laser beam 21.

(37) From FIGS. 4 to 8, it may also be seen that the internal passageway (cooling circuit) of the thermal control unit 7 is provided in the form of a chamber 771C in the rear cooling portion 77. The inlet pipe 78 extends to the front of the chamber 771C, and the outlet pipe 79 vents the rear of the chamber 771C.