DE102015008918B4 - Process for the additive manufacturing of three-dimensional components - Google Patents

Abstract

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 in that the fusing 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.

Description

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

Such procedures are known, for example, from EP 1 296 788 B1 or DE 10 2013 108 111 A1 Usually, 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 the laser at the points where material application is desired. This process is repeated until the desired component is produced, whereby complex three-dimensional structures are also possible through the layer-by-layer construction. US 6,605,795 B1 and the US 7,765,022 B2 Such procedures are known.

However, it has been shown that the need to apply another layer of powder after each layer, which also has to be smoothed out, is very time-consuming and results in relatively large amounts of powder that are not even fused to the component. It goes without saying that the residual powder in the known processes is produced in particularly large quantities when the component to be manufactured has a relatively large number of cavities and recesses in relation to its base area.

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

The application of material using an arc, known as deposition welding, is also known, but this has not yet achieved great importance in the context of additive manufacturing processes. A major problem, particularly when machining workpieces to produce the component in a vacuum, is that an arc in a vacuum often jumps uncontrollably, which in turn is detrimental to the quality of the component being produced.

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.

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.

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 produced layers of the component on the one hand and rapid material application with precise guidance of the processing point on the other. It has been shown that when guided by a laser or electron beam, the arc no longer tends to explode uncontrollably, even under vacuum conditions, so that the position of a melt pool at the processing point can be guided precisely on the one hand, but on the other hand does not extend too deeply into the workpiece that has already been produced.

In a particularly preferred embodiment of the invention, the arc is focused and/or additionally ionized using the laser beam. This measure can further increase the quality of the material application.

In principle, it is possible to supply the metallic material as a powder. On the one hand, it is possible to apply the metallic material as a powder layer by layer to the already produced layers of the component in a known manner and then to melt it where a material application is desired using the laser and/or electron beam-controlled arc. To avoid unnecessary accumulation of metal powder, which is not actually necessary to produce a material application, 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.

In a particularly preferred embodiment of the invention, the metallic material is supplied as a wire.

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.

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

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

This variant offers the advantage that few parts are required to carry out the process within the vacuum chamber, with the wire melting at the tip taking place directly with the help of the arc generated there. The wire is preferably movable in the feed direction and in the opposite direction, so that the arc can be controlled by moving it back and forth. To refine the process, the forward and backward movement can also be used to specifically remove drops at the tip of the wire and minimize the heat input into the component.

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

The arc can be generated with a direct current or with an alternating current. This can influence the magnetic fields created by the welding current and have a positive effect on the so-called arc blows, spatter and the like.

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

• 1 einen Längsschnitt einer Vorrichtung zur additiven Herstellung eines metallischen Bauteils;
• 2 einen Längsschnitt einer weiteren Ausführungsform einer Vorrichtung zum additiven Herstellen von dreidimensionalen metallischen Bauteilen.

Two embodiments of the invention are described in more detail below with reference to the accompanying drawings. They show:

• 1 a longitudinal section of a device for the additive manufacturing of a metallic component;
• 2 a longitudinal section of another embodiment of a device for the additive manufacturing of three-dimensional metallic components.

In 1 a device 10 is shown with which a method for 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 the component to be moved in the X, Y and Z directions. The component 12 is produced layer by layer in the sense of additive manufacturing, ie in the 1 In the embodiment shown, a number of layers have already been applied, with the current material layer 16 applied not being shown to scale for illustrative purposes. The first layer can be built up on a substrate previously introduced into the chamber 14.

A vacuum pump 18 evacuates the interior of the vacuum chamber 14 to the pressure values customary in the field of thermal processing methods in a vacuum.

The energy input required to melt the supplied metallic material in the applied material layer 16 is provided by an arc 20 which is built up 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, which itself only has a relatively low light output, approximately 100 watts in the embodiment shown, which itself would not be suitable for melting the material in order to form the applied layer 16.

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

The wire 28 is fed to the processing unit by means of a very simplified wire feed 30. The arc is fed to the welding point on the melt pool 26, whereby 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 in such a way that the arc 20 can form between a wire end 36 and the workpiece 12 at the point of the melt pool 26. The wire feed 30 is suitable for moving the wire in both directions, i.e. towards the melt pool 26, but also away from the melt pool, in order to be able to control the arc 20 on the one hand and to ensure a 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 avoid melting of previously produced material layers under the current material layer 16. It is also 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.

The current flow in the wire 28 between a connection point 38 of the power source and the arc 20 also results in the wire heating 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 smaller.

In 2 another device 10 is shown, which in many structural details corresponds to the previously presented device 10 according to 1 and has therefore been given the same reference numerals in the area of matching 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 the electrode tip 136 of which and the molten bath 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 bath. The wire is fed 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 located outside the vacuum chamber, with supply lines 135 being led into the interior of the chamber through corresponding vacuum-tight feedthroughs.

In order to be able 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, with a coil 152 winding around the wire 28 in a spiral shape to generate eddy currents in the wire. The eddy currents ensure that the wire is heated, so that the heat input applied 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 (12)

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 in that the fusing 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. procedure according to claim 1 , characterized in that the arc (20) is focused and/or additionally ionized by means of the laser (22) and/or electron beam. procedure according to claim 1 or 2 , characterized in that the metallic material is supplied as a powder. procedure according to claim 3 , characterized in that the metallic powder is applied layer by layer to a previously applied layer of the component and then the desired sections are fused. procedure according to claim 3 , characterized in that the metallic powder is swirled in a gas stream and the gas stream is fed to the processing point. procedure according to claim 1 or 2 , characterized in that the metallic material is supplied as a wire (28). procedure according to claim 6 , characterized in that the wire (28) is supplied as a consumable electrode for forming the arc (20) between the wire (28) and the component (12). procedure according to claim 7 , characterized in that the wire (28) is moved in the feed direction and in the opposite direction to control the arc (20). procedure according to claim 8 , characterized in that by moving the wire (28) back and forth, drops of molten metal are detached from a wire end (36) and the heat input into the layers already produced is minimized. procedure according to claim 6 , characterized in 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. Method according to one of the preceding claims, characterized in that the arc (20) is generated with a direct current or an alternating current. Method according to one of the preceding claims, characterized in 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.

Images