METHOD AND APPARATUS FOR MANUFACTURING 3D METAL PARTS

Abstract

A method of manufacturing a metallic part in a weldable material by solid freeform fabrication comprising generating three dimensional model of the part, slicing the three dimensional model into a set of parallel, sliced layers and then dividing each layer into a set of one-dimensional pieces and, with reference to layered weld-bead geometry data, forming a computer-generated, direction specific, layered model of the part. The method also comprises uploading the layered model into a welding control system and directing the welding control system to deposit a sequence of one-dimensional weld beads of the weldable material onto the supporting substrate in a pattern required to form a first layer of the layered model and depositing a second welded layer onto the previous deposited layer in a configuration the same as the second layer, and repeating each successive weld bead until the entire part is completed. The method further includes displacing the atmosphere within the immediate vicinity of the heat source with an inert gas atmosphere which produces a required flow rate, and in which that inert atmosphere contains a maximum oxygen concentration, wherein the inert gas is delivered by an apparatus through a matrix of individual gas diffusers; and engaging an induction heating and closed loop cooling apparatus synergic to a welding control system and pre-heating the substrate material including the deposited weld beads, relevant to the type of weldable material, wherein induction heating and cooling cycles are applied constantly or pulsed from the first layer to the final layer, where optimal heating and/or cooling cycles of the weldable material are relative to the final desired part shape and microstructure.

Claims

1. A method of manufacturing a metallic part in a weldable material by solid freeform fabrication unrestricted in size and open to the ambient atmosphere, wherein the method comprises: generating a computer-generated, three dimensional model of the part, slicing the computer-generated three dimensional model into a set of computer- generated, parallel, sliced layers and then dividing each layer into a set of computer-generated, virtual, one-dimensional pieces and, with reference to layered weld-bead geometry data, forming a computer-generated, direction specific, layered model of the part, uploading the direction specific, layered model of the part into a welding control system able to control the position and activation relative to a support substrate, of an electric arc delivered by a high energy tungsten arc welding torch, a plasma transferred arc welding torch, and/ or a gas metal arc welding torch, and a system for feeding a consumable wire placed in an open area build space relevant to the substrate unrestricted in size and open to the ambient atmosphere for generating molten metal, directing the welding control system to deposit a sequence of one-dimensional weld beads of the weldable material onto the supporting substrate in a pattern required to form a first layer of the computer-generated, direction specific, layered model of the part, depositing a second welded layer by sequencing one- dimensional weld beads of the weldable material onto the previous deposited layer in a configuration the same as the second layer of the computer-generated direction specific layered model of the part, and repeating each successive weld bead layer of the computer-generated, direction specific, layered model of the part until the entire part is completed; wherein the method further includes: displacing the atmosphere within the immediate vicinity of the heat source and the molten metal with an atmosphere of inert gas which produces a required flow rate, and in which that inert atmosphere contains a maximum oxygen concentration, wherein the inert gas is delivered by an apparatus through a matrix of individual gas diffusers and includes a gas manifold compartment that is 80 to 180 mm wide and 180 to 400 mm long or that is of a cylindrical shape up to 400 mm in diameter; and engaging an induction heating and closed loop cooling apparatus synergic to a welding control system and pre-heating the substrate material including the deposited weld beads, relevant to the type of weldable material, wherein induction heating and cooling cycles are applied constantly or pulsed from the first layer to the final layer, where optimal heating and/ or cooling cycles of the weldable material are relative to the final desired part shape and microstructure.

2. A method according to claim 1, wherein the weldable material is a weldable metal, or a weldable alloyed metal, of ferrous or non-ferrous nature.

3. A method according to claim 2, wherein the weldable material is carbon steel or carbon manganese alloys, nickel or nickel alloys, stainless steels, aluminium or aluminium alloys, titanium or alloyed titanium, ferrous or non-ferrous, or a mixture of dissimilar weldable materials.

4. A method according to claim 1, wherein the inert gas is one of argon, helium, hydrogen, nitrogen, or a mixture of these.

5. A method according to claim 1, wherein the inert gas shielding the electric arc and heat-affected material is argon or an argon mixture, and where the flow rate of the argon or argon mixture is constant or pulsed and above 20 liters per minute, and wherein the distribution of the inert gas is delivered through a series of gas diffusers.

6. A method according to claim 1, wherein the required flow rate is greater than 20 1/min.

7. A method according to claim 1, wherein the maximum oxygen concentration is less than 500 ppm oxygen.

8. A method according to claim 1, wherein there are less than 25 individual gas diffusers.

9. Production apparatus for a part made of a weldable material by solid freeform fabrication, where there is no enclosure or reactor required, and the part is built in an unrestricted build environment open to the ambient atmosphere by an apparatus which distributes an inert gas flow, the production apparatus including: a robotic multiple-axis mechanism controlling the position and movement of a welding torch with a wire feeder relative to a stationary support substrate placed upon a fixed support, the welding torch being an electric arc welding process, a tungsten arc welding torch, a gas metal arc welding torch, or a plasma transferred arc welding torch; a support mechanism controlling the position and movement of the welding torch and the wire feeder relative to the support substrate, and an actuator controlling the position and movement relative to the support mechanism; and a control system able to read a computer-generated, three dimensional, direction specific, layered model of the part and employ the computer-generated model to control the position and movement of the robotic multiple-axis mechanism, and the operation of the welding torch and wire, feeder such that a part is built by welding in a layer-by-layer sequence according to one-dimensional slices of the weldable material onto the substrate structure in agreement with the computer- generated, three dimensional, direction specific, layered model of the part; the apparatus also including a localised purging apparatus and an induction heating and closed loop cooling apparatus.

10. Apparatus according to claim 9 wherein the localised purging apparatus includes a manifold filled with argon or argon mixture as inert gas, and a gas inlet, where the gas inlet is equipped with means for regulating the gas flow rate.

11. Apparatus according to claim 9 wherein the induction heating apparatus is capable of heating the substrate and subsequent weld bead layers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] One embodiment of the manufacturing method and apparatus of the present invention is shown in the schematic drawing of FIG. 1. FIG. 1 shows the construction of a metallic part 10 by welding a piece of weldable material onto a first layer by an electric arc welding process that melts a wire consumable of the weldable material using a weld bead layering technique to provide freeform fabrication.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0040] With reference to FIG. 1, illustrated is a computer 12 providing feedback signals A,B,C,D,E for the control of a robot power supply 14, a welder power supply 16, an activating solenoid valve 36, an induction heating apparatus 32 and a solenoid controller 18. The welder power supply 16 also provides power and control for a wire feeder 20. Wire is fed via F to a welding torch 22 that is a part of the robot 24, which in this form is an electric arc transferred plasma welding torch. An electric arc may alternatively be transferred via a tungsten inert gas welding torch, again with a wire feeder 20 of similar weldable material. Further, an electric arc may be transferred via a wire consumable using a gas metal inert welding torch.

[0041] The gas supply system includes a shielding gas feed cylinder 40 supplying an 8/2 solenoid valve 36 to activate the gas going to a purge apparatus 30, via a further solenoid splitter valve 38. Feedback signals provide suitable control via the solenoid controller 18.

[0042] The metallic part 10 being welded in the layer-by-layer process described above is layered on a suitable substrate 26 supported by a substrate cooling bed 28. A purge apparatus 30 is positioned above the metallic part 10 to shield the deposited weld in the manner generally described above. Actuators for the robot 24 and the torch, and for the purge apparatus 30, are shown located outside the boundary limits of the build area, the substrate 26, and a high energy heat source 32.

[0043] The substrate 26 and subsequent metal layering is pre-heated and maintained using an induction heating apparatus 32, which is synergic controlled during the metal layering operation. Induction heating during the process enhances increased metal deposition and provides a means of distortion control for the final part 10.

[0044] The substrate 26 in this embodiment includes cooling channels (not shown) to further control the temperature of the metal part 10. The cooling apparatus 34 is closed loop in nature and is connected to the substrate via fittings which circulate coolant through the cooling channels. Cooling offers the advantage of decreasing the time between layers, thus decreasing overall build times for a completed 3D printed part.

[0045] This embodiment of the method and apparatus of the invention provides a high deposition method and apparatus for manufacturing 3D metal parts, which includes localised atmospheric protection and solid freeform fabrication unrestricted in size and open to the ambient atmosphere, in particular for the manufacture of parts made of carbon manganese alloys, aluminium alloys, nickel alloys, stainless steels and titanium alloys.

[0046] As mentioned above, the apparatus has no restriction to build or part size, or area size, and is open to the ambient atmosphere, wherein the molten weld pool and neighbouring area is shielded by the localised apparatus used for distributing a generous but controlled laminar inert gas flow. Gas flow distribution is located above the build area and given a design such that the gas distribution flows evenly and equally around the weld pool area and solidifying molten metal.

[0047] Many modifications may be made to the embodiment of the invention described in relation to FIG. 1 without departing from the spirit and scope of the invention.