Methods for the additive manufacturing of three-dimensional components

Abstract

Method for the additive manufacturing of three-dimensional, metallic components (12), wherein the components (12) are built up layer by layer or section by melting a supplied, metallic material with the component (12) under vacuum conditions, characterized in that the melting of the metallic material with the component (12) at a processing point is carried out by means of an electric arc (20), wherein the electric arc (20) is guided by means of a laser (22) and / or electron beam.

Description

[0001] The present invention relates to a method for the additive manufacturing of three-dimensional metallic components, wherein the components are built up layer by layer or section by fusing a supplied metallic material with the component under vacuum conditions.

[0002] Such methods are known, for example, from EP 1 296 788 B1 or DE 10 2013 108 111 A1. Typically, starting from a substrate, which can also be used in the present invention, the material is applied layer by layer by applying a powder layer in individual steps, which is then fused with the substrate using a laser at the locations where material deposition is desired. This process is repeated until the desired component is produced, with even complex three-dimensional structures being possible through the layer-by-layer construction. Such methods are also known from US Pat. Nos. 6,605,795 B1 and 7,765,022 B2.

[0003] However, it has been shown that the application of an additional layer of powder after each layer, which also has to be smoothed, is, on the one hand, quite time-consuming and, on the other hand, results in relatively large quantities of powder that are not even fused to the component. It is understood that the residual powder is generated in particularly large quantities with the known processes when the component to be manufactured has a relatively large number of cavities and recesses relative to its base area.

[0004] When using laser beams to melt the material in additive manufacturing, there is also a problem that the relatively high heat input of a laser beam, which can have a light output of up to 4 kW, can cause previously produced material layers to be melted again under the layer currently being processed, which is undesirable in terms of producing high-quality components.

[0005] The application of material using an arc, known as cladding, is also known, but has not yet achieved significant significance in additive manufacturing processes. A major problem, particularly when machining workpieces to produce components in a vacuum, is that arcs in a vacuum often jump uncontrollably, which in turn is detrimental to the quality of the component being manufactured.

[0006] The object of the present invention is to improve a method of the type mentioned at the outset in such a way that the quality of the components produced is improved.

[0007] According to the invention, the object is achieved in that, in a method of the type mentioned at the outset, the melting of the metallic material with the component is carried out at a processing point by means of an arc, wherein the arc is guided by means of a laser and / or electron beam.

[0008] It has been shown that the combination of an arc, which provides the main melting power for melting and fusing the supplied metallic material with the component, and a laser, or possibly an electron beam, which guides the arc, enables a particularly good combination of low heat input into the previously created layers of the component on the one hand, and rapid material deposition with precise guidance of the processing point on the other. It has been shown that with the guidance of a laser or electron beam, the arc no longer tends to uncontrolled explosion, even under vacuum conditions, so that the position of a molten pool at the processing point can be precisely guided, but on the other hand, it does not extend too deeply into the already produced workpiece.

[0009] In a particularly preferred embodiment of the invention, the arc is focused and / or additionally ionized using the laser beam. This measure can further improve the quality of the material deposition.

[0010] In principle, it is possible to supply the metallic material as a powder. On the one hand, there is the option of applying the metallic material as a powder in successive layers to the already produced layers of the component in a conventional manner and then fusing it where material deposition is desired using a laser and / or electron beam controlled arc. To avoid unnecessary accumulation of metal powder, which is not actually required to create a material deposit, it can be advantageous to swirl the metallic powder in a gas stream and then direct the gas stream to the processing point. It has been shown that this measure results in significantly less excess powder, which is particularly advantageous when the process is carried out in a vacuum chamber.

[0011] In a particularly preferred embodiment of the invention, it is provided that the metallic material is supplied as a wire.

[0012] The wire can be fed laterally or coaxially with respect to the laser and / or electron beam, whereby the wire can be fed cold or, if necessary, preheated to the solidus temperature range.

[0013] The wire can be fed, for example, through a feedthrough in the wall of a vacuum chamber via a pressure stage system or via a wire supply within the vacuum.

[0014] Preferably, the wire is supplied as consumable electrons to form the arc between the wire and the component.

[0015] This variant offers the advantage that few parts are required to carry out the process within the vacuum chamber, with the melting of the wire at the tip occurring directly with the help of the arc generated there. Preferably, the wire is movable in both the feed and reverse directions, so that the arc can be controlled by moving it back and forth. To refine the process, the forward and backward motions can also be used to selectively detach droplets from the tip of the wire and minimize heat input into the component.

[0016] Alternatively, a non-consumable electrode can be used to form the arc, with the wire being fed to the resulting processing point. Here, too, the position of the fixed electrode can, of course, be variably controlled to control the arc.

[0017] The arc can be generated with either direct current or alternating current. This can influence the magnetic fields generated by the welding current, thus positively influencing the resulting arc blows, spatter, and the like.

[0018] Preferably, the method is carried out in such a way that the processing point is formed stationary in a vacuum chamber, while the component is moved relative to the processing point during the material application.

[0019] Two embodiments of the invention will be discussed in more detail below with reference to the accompanying drawings. They show: Fig. 1 shows a longitudinal section of a device for the additive manufacturing of a metallic component; Fig. 2 a longitudinal section of a further embodiment of a device for the additive production of three-dimensional metallic components.

[0020] In Fig. 1, a device 10 is shown, with which a method for the additive manufacturing of a metallic component 12, which is shown here as a workpiece under construction, can be carried out in a vacuum chamber 14. The component 12 or workpiece is mounted on a table (not shown in detail), which enables movement of the component in the X, Y and Z directions. The component 12 is produced layer by layer in the sense of additive manufacturing, ie in the Fig. In the embodiment shown in Figure 1, a number of layers have already been applied, with the current applied material layer 16 not shown to scale for illustrative purposes. The first layer can be built up on a substrate previously introduced into the chamber 14.

[0021] A vacuum pump 18 evacuates the interior of the vacuum chamber 14 to the pressure values ​​customary in the field of thermal processing processes in a vacuum.

[0022] The energy input required to melt the supplied metallic material into the applied material layer 16 is provided by an arc 20, which is established between a wire 28 supplied as metallic material and the workpiece 12. Since an arc tends to change its position uncontrollably under vacuum conditions, a laser 21 is arranged outside the chamber. This laser itself has only a relatively low light output, approximately 100 watts in the illustrated embodiment, which would not be suitable for melting the material to form the applied layer 16.

[0023] A laser beam 22 from laser 20 is directed through an entrance window 24 in the wall of vacuum chamber 14 to a processing location on component 12, where a molten pool 26 forms due to the arc 20. Ventilation (not shown) on the inside of entrance window 24 prevents metal vapors from condensing there. Laser beam 22 serves to position arc 20 at the desired processing location and is also suitable for focusing and further ionizing the arc. In this way, it is possible to control the melting energy generated by arc 20 with a comparatively small and low-power laser and to produce a high-quality component 12.

[0024] The wire 28 is fed to the processing point at the molten pool 26 by means of a wire feed 30 (illustrated in a very simplified manner). It is fed through a vacuum feedthrough 32 in the wall of the vacuum chamber 14 into the interior of the vacuum chamber and is fed, for example, by driven friction rollers. To form the arc, a direct current source 34 is arranged outside the vacuum chamber, the negative polarity of which is connected to the wire 28 and the positive polarity of which is connected to the workpiece 12. The voltage and power of the current source 34 are designed such that the arc 20 can form between a wire end 36 and the workpiece 12 at the location of the molten pool 26. The wire feed 30 is suitable for moving the wire in both directions, i.e.towards the molten pool 26, but also away from the molten pool, in order to be able to control the arc 20 on the one hand and to ensure targeted detachment of molten metal at the wire end 36 on the other hand and to keep the energy input into the workpiece 12 as minimal as possible in order to prevent previously produced material layers from melting beneath the current material layer 16. It is also readily possible to use an alternating current source to generate the arc instead of a direct current source 34, which can have a positive effect on the magnetic fields generated by the welding current and the associated so-called arch blows and metal splashes.

[0025] The current flow in the wire 28 between a connection point 38 of the power source and the arc 20 also causes the wire to heat up, which has an overall positive effect with regard to a reduced heat input into the workpiece 12 because the arc power for melting and applying the metallic material can thus be set lower.

[0026] In Fig. 2 shows a further device 10 which in many structural details corresponds to the previously presented device 10 according to Fig.1 and has therefore been provided with the same reference numerals in the area of ​​identical components. A difference in this embodiment is that the wire 28 itself is not designed as a consumable electrode to form the arc, but rather a non-consumable, fixed electrode 128 is provided, between whose electrode tip 136 and the molten pool 26 the arc 20 is formed. The wire 28 is otherwise fed in the manner described above with the aid of a wire feed 30, which in turn can enable the wire 28 to be fed in or withdrawn from the molten pool. The wire is guided through a vacuum feedthrough 32 into the interior of the vacuum chamber. The arc 20 is in turn applied by means of a direct current source 134, the negative polarity of which is connected to the welding electrode 128 and the positive polarity of which is connected to the workpiece 12.The power source 134 is again located outside the vacuum chamber, with supply lines 135 being led into the chamber interior through corresponding vacuum-tight feedthroughs.

[0027] In order to preheat the wire 28 in this embodiment, an inductor 150 is provided, the power supply of which is arranged outside the vacuum chamber 14. A coil 152 for generating eddy currents in the wire 28 is wound helically around the wire 28. The eddy currents heat the wire, so that the heat input by the arc 20 can be kept low in order to minimize the melting of previously applied material layers below the applied material layer 16.

Claims

[1] Method for the additive production of three-dimensional metallic components (12), wherein the components (12) are built up layer by layer or section by fusing a supplied metallic material with the component (12) under vacuum conditions, characterized by that the melting of the metallic material with the component (12) is carried out at a processing point by means of an arc (20), wherein the arc (20) is guided by means of a laser (22) and / or electron beam. [2] Method according to claim 1, characterized by that the arc (20) is focused and / or additionally ionized with the aid of the laser (22) and / or electron beam. [3] Method according to claim 1 or 2, characterized by that the metallic material is supplied as a powder. [4] Method according to claim 3, characterized bythat the metallic powder is applied layer by layer to a previously applied layer of the component and then the desired sections are fused. [5] Method according to claim 3, characterized by that the metallic powder is swirled in a gas stream and the gas stream is fed to the processing point. [6] Method according to claim 1 or 2, characterized by that the metallic material is supplied as a wire (28). [7] Method according to claim 6, characterized by that the wire (28) is supplied as a consumable electrode for forming the arc (20) between the wire (28) and the component (12). [8] Method according to claim 7, characterized by that the wire (28) is moved in the feed direction and in the opposite direction to control the arc (20). [9] Method according to claim 8, characterized bythat by moving the wire (28) back and forth, drops of molten metal are detached from one wire end (36) and the heat input into the layers already produced is minimized. [10] Method according to claim 6, characterized by that the arc (20) is formed between a non-consumable electrode (128) and the component (12) and the wire (28) is fed to the processing point formed thereby. [11] Method according to one of the preceding claims, characterized by that the arc (20) is generated with a direct current or an alternating current. [12] Method according to one of the preceding claims, characterized by that the processing point is formed stationary in a vacuum chamber (14), while the component (12) is moved relative to the processing point during the material application.

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