ADDITIVE MANUFACTURING PROCESS WITH HYDRATION

Description

[0001] The invention relates to an additive manufacturing method for machine components with integrated hardening. The invention also relates to a computer program product with which the method according to the invention can be carried out. Furthermore, the invention relates to a control unit having such a computer program product and a manufacturing device equipped with a corresponding control unit.

[0002] From the publication DE 10 2004 008 054 A1, a method for producing a three-dimensional object is known, in which a metal powder layer is created. A laser beam acts on the metal powder layer to melt it. A metal powder composition is used, which includes an iron-based powder material, a nickel and / or nickel alloy powder material, a copper and / or copper alloy powder material, and a graphite powder material.

[0003] From CN 103 635 305 A it is known to apply a curable material in successive layers, wherein one or more predetermined areas are selectively cured after or during the application of a layer, wherein the predetermined areas are connected to one or more areas of the underlying layer.

[0004] From DE 10 2018 201 854 A1 it is known to form a component using a metal powder containing carbon and nitrogen by means of laser sintering and to carry out hardening by nitriding or a temperature treatment during or after the laser sintering.

[0005] From DE 10 2014 216 313 A1 it is known to provide a body with an additively applied hardened layer.

[0006] In various technical fields, the goal is to produce machine components subject to high mechanical stress using additive manufacturing. In particular, the aim is to also produce machine components that require high levels of hardness using additive manufacturing. At the same time, the goal is to simplify the production of such mechanically highly stressed machine components while simultaneously increasing the design freedom for such machine components. The invention is based on the object of providing a method for producing sophisticated machine components using additive manufacturing.

[0007] The problem is solved by the method according to the invention with the features of claim 1, which is directed to producing a machine component by additive manufacturing. The method comprises a first step in which at least one material layer is provided. For this purpose, the material layer can be applied essentially flatly in a work area by at least one dispensing device. In a second step, the material layer is irradiated with a laser. The laser irradiation melts the material layer locally. The locally melted area solidifies automatically after laser irradiation through heat release. In the second step, the material layer is traced by the laser essentially in a pattern and irradiated accordingly. The material layer applied in the first step comprises a base material.

[0008] According to the invention, the material layer also comprises a hardening agent that can be added to the base material. In the first step, the hardening agent is added locally to the base material in an adjustable manner, resulting in a locally variable proportional composition of the material layer in terms of base material and hardening agent. The addition of the hardening agent is adjustable in such a way that it is possible to specify the amount of hardening agent added to the base material at a selectable location on the surface of the material layer. In particular, this allows a concentration gradient for the hardening agent to be set within a plane defined by the material layer. This results in a locally variable proportional composition of the material layer in terms of base material and hardening agent.Further according to the invention, the hardening agent is at least enclosed in the base material in the second step, in which the material layer is irradiated with the laser. The local melting of the material layer, in particular the base material, thus creates a thermal, chemical, and physical state in which the hardening agent is at least embedded, i.e., enclosed, in the molten base material upon solidification.

[0009] By enclosing the hardening agent in the base material, at least some hardening is prepared. The higher the local concentration of hardening agent, the stronger the hardening can be. This accelerates the production of a machine component that requires hardening. By adjusting the amount of hardening agent, the hardening of the machine component to be manufactured can be carried out in a predeterminable manner. In particular, areas in which increased or reduced hardening is desired can be determined essentially arbitrarily. For example, carburizing is thus unnecessary, since the distribution of the carbon to be incorporated in the metal results from the diffusion behavior in the carburizing atmosphere.Overall, the method according to the invention provides a possibility that allows the rapid production of hardened machine components by additive manufacturing and offers a high degree of design freedom due to the adjustability of a local hardness.

[0010] In one embodiment of the claimed method, in the second step, in which the material layer is irradiated with the laser, the hardener can be at least partially dissolved in the base material. The thermal energy locally introduced by the laser enables diffusion of the enclosed hardener into the base material. For example, atoms of the hardener can be embedded in elemental form in an atomic lattice of the base material. At least partial diffusion of the hardener into the base material can shorten a subsequent diffusion process.

[0011] In a further embodiment of the claimed method, a dispensing quantity of the hardening agent can be locally adjusted. For this purpose, a dispensing device, through which the hardening agent is added to the base material, can be controlled accordingly. For example, an opening duration, opening width, and / or delivery pressure can be adjusted at a dispensing nozzle of the dispensing device. Consequently, the local distribution of the hardening agent can be specified by a simple parameter of a corresponding manufacturing device. Furthermore, a layer thickness of the material layer can be adjusted to influence the desired hardness distribution.

[0012] Furthermore, the method can comprise a third step in which the machine component is hardened. The machine component, which in the first and second steps is constructed from several laser-irradiated material layers, is exposed to an environment with an adjustable process temperature, for example a hardening furnace. In the third step, the machine component is heated to a temperature at which diffusion of the hardening agent dissolved in the base material occurs. Because, as already outlined in the first and second steps, the distribution of the hardening agent can be specifically specified by locally adjustable addition to the base material, diffusion distances for the hardening agent in the base material can be shortened. A diffusion distance is understood to be the distance that the hardening agent has to travel by diffusion until a desired concentration distribution in the machine component is reached.Shortening the diffusion distances allows the desired distribution or concentration distribution of the hardening agent to be achieved with a reduced process time, to which the machine component is exposed to the environment at the process temperature. Furthermore, a shortened process time for diffusion allows the occurrence of edge oxidation on the surface of the machine component to be reduced or even completely avoided. This, in turn, reduces the tendency for tooth root fracture or tooth flank fracture in gears, for example. Overall, the hardening process, and thus the entire production of the machine component, can be accelerated with increased quality. Alternatively or additionally, the same diffusion distance can be achieved with the same process time at a lower process temperature. This allows energy savings in the production of the machine component.

[0013] Furthermore, the hardening agent can be in the form of carbon powder or carbon liquid. This refers in particular to a powder or a liquid containing elemental carbon. An example of a carbon powder can be graphite powder, for example; a carbon liquid is a liquid with graphite powder dissolved therein. Due to their easy dosing, carbon powder and carbon liquid allow the precise local addition of essentially elemental carbon to the base material. Carbon powder can be mixed with the base material, which is also essentially a powder, in a dispensing device. The carbon liquid, in turn, is bound by the powdered base material, thus enabling a precise distribution of carbon on the material layer.

[0014] In a further embodiment of the claimed method, the base material can be an iron-based alloy, i.e., essentially a steel, a manganese alloy, or a nickel-based alloy. Such materials can be advantageously melted in powder form by laser irradiation and produce a high-quality microstructure using appropriate additive manufacturing processes. Furthermore, proven and reliable additive manufacturing processes exist for such materials, such as selective laser melting.

[0015] Furthermore, the claimed method, in particular the first and second steps, can be repeated for a plurality of material layers. Thus, a concentration gradient for the hardening agent can be established not only within a plane of a material layer, but also across multiple material layers perpendicular to their planes. The distribution of the hardening agent can thus be adjusted three-dimensionally within the machine component. Since the distribution of the hardening agent corresponds to the hardness distribution in a finished machine component, a high degree of design freedom is ensured for the machine component.

[0016] Furthermore, in the claimed method, the intensity of the laser can be adjusted, allowing the thermal energy introduced into the material layer by the laser to be specified. The intensity of the laser can be specified during the second step, in which the material layer is irradiated, in such a way that diffusion of the hardening agent into the base material is at least initiated. This allows the hardness of the machine component to be adjusted during additive manufacturing, and a subsequent diffusion step can be shortened or eliminated if necessary. Accordingly, the design freedom achieved with the claimed method with regard to hardness distribution is further increased.

[0017] In a further embodiment of the claimed method, the material layer can comprise a first and a second material, which can form the material layer in a locally distributed manner in an adjustable manner. This allows, for example, sections located essentially inside the machine component to be manufactured to be made of a simple first material that has only a reduced suitability for hardening. However, sections located further out, for which hardening is required, can be made, for example, of a second material that is well suited to hardening. This improves overall material utilization and simultaneously increases cost efficiency.

[0018] The underlying problem is also solved by the computer program product according to the invention with the features of claim 13. The computer program product is designed to be executed in a memory and a computing unit of a control unit and can be stored in a non-volatile memory. The computer program product is designed to receive design data for additive manufacturing of a machine component, which also includes information about a locally desired hardness of the machine component. The computer program product is also designed to determine control commands therefrom, which can be output to a dispensing device for a hardening agent and a laser. The dispensing device and the laser belong to a manufacturing device for additive manufacturing, for example, a system for selective laser melting.The computer program product is designed to carry out at least one of the methods outlined above. The computer program product can be embodied as software or hard-wired, or a combination thereof. Hard-wired here means, for example, a chip, an integrated circuit, or an FPGA. Furthermore, the computer program product can be monolithic or modular. Monolithic means that the computer program product can be executed solely on one hardware platform. Modular means that the computer program product comprises at least two subprograms that can be executed on different hardware platforms and that, during intended operation, interact via a data connection to implement the claimed method.This can be achieved, for example, by a control unit in a manufacturing device that is equipped with a subprogram and is connected, for example, to a computer cloud on which another subprogram is executed.

[0019] The described problem is also solved by the control unit according to the invention with the features of claim 14. The control unit has a computing unit and a memory configured to control a manufacturing device. According to the invention, the control unit is equipped with a computer program product according to one of the embodiments described above. Alternatively or additionally, the control unit can be configured to carry out at least one embodiment of the method outlined above.

[0020] The problem is also solved by the manufacturing device according to the invention with the features of claim 15, which has a dispensing device for a base material suitable for additive manufacturing. The manufacturing device also has a dispensing device for a hardening agent that can be added to the base material. Furthermore, the manufacturing device comprises a laser by which the base material can be locally melted. The manufacturing device as a whole is designed for the additive manufacturing of machine components. According to the invention, the manufacturing device is provided with a control unit designed according to one of the embodiments presented above.

[0021] A machine component (not falling within the scope of the claims) can be constructed from multiple material layers and comprise a base material that is joined by laser irradiation. This means that the base material is transformed from a powdery state into a coherent workpiece by laser irradiation. This can be the case, for example, if the machine component is manufactured using additive manufacturing, in particular by selective laser melting. A hardening agent is dissolved in the base material, resulting in a locally variable proportional composition of the material layer in terms of base material and hardening agent, which locally determines the hardness of the machine component. Dissolved means, for example, that the atoms of the hardening agent are embedded in an atomic lattice of the base material.The machine component has a first region in which a first hardness is present. Furthermore, the machine component has a second region in which a second hardness is present. The first and second regions are adjacent to one another. This creates a transition from the first hardness to the second hardness at a common region boundary. The transition from the first hardness to the second hardness is essentially designed as a discrete step. Such a discrete step can be produced, for example, by a method according to one of the embodiments outlined above. The diffusion paths for the hardening agent in the machine component are shortened, which in turn enables high concentration gradients for the hardening agent. These in turn lead to essentially step-like hardness transitions in the machine component.However, the machine component can also be any other machine component that needs to be hardened during production using known processes.

[0022] Furthermore, the machine component can be designed as an externally toothed gear, an internally toothed ring gear, or a rack. In particular, the machine component can also be designed as any other component with teeth. In the manufacture of such machine components, the hardness and its distribution across the machine component represent a key design aspect. A corresponding machine component can therefore be easily adapted to the resulting design requirements through an essentially arbitrarily specified hardness distribution. In particular, tooth root fracture or tooth flank fracture can be prevented in this way. The machine component therefore exhibits increased mechanical performance and a longer service life, and thus reliability.

[0023] The invention is explained in more detail below using individual embodiments in the figures. The figures are to be read as complementary to one another, insofar as identical reference numerals in different figures have the same technical meaning. The scope of the invention is defined in the appended set of claims. They show in detail:

[0024] FIG 1 schematically shows a structure of a manufacturing device for carrying out an embodiment of the claimed method; FIG 2 schematically shows the structure of a material layer during an embodiment of the claimed method; FIG 3 schematically shows a sequence of an embodiment of the claimed method; FIG 4 schematically shows an embodiment of a machine component; FIG 5 a schematic view of a further embodiment of the machine component.

[0025] In FIG 1 A schematic diagram of a manufacturing device 90 is shown, with which an embodiment of the claimed method 100 can be carried out. The manufacturing device 90 comprises a doctor blade 32, with which a base material 30, which is essentially a metal powder, is applied in a first step 110 in a work area 14. A hardening agent 42 is added to the base material 30 via a dispensing device 40. The dispensed quantity of the hardening agent 42 can be adjusted via a dispensing nozzle 44 of the dispensing device 40. The hardening agent 42 can be in the form of a carbon liquid or a carbon powder. Together, the base material 30 and the hardening agent 42 form a material layer 12. The dispensing device 40 is designed to be movable, so that a concentration of the hardening agent 42 in the plane of the material layer 12 can be adjusted essentially at will.The material layer 12 is provided in its entirety in the first step 110 of the method 100.

[0026] In a second method step 120, the material layer 12 is irradiated by a laser 20. For this purpose, a laser beam 25 with an adjustable intensity 26 is directed onto the material layer 12. The laser 20 locally heats the material layer 12, causing the base material 30 to melt. The laser 20 is controlled such that the irradiated material layer 12 further builds up a machine component 10 to be manufactured. After the laser beam 25 passes over the material layer 12, the base material 30 solidifies and at least encloses hardening material 42. The locally present concentrations of hardening agent 42 in the melted and solidified base material 42 allow a hardness of 72 to be set in the machine component 10 to be manufactured. The irradiation of the material layer 12 takes place in the claimed method 100 in the second step 120. By further heat input by means of the laser 20, a FIG 1 Diffusion 48 of the hardening agent 42 into the base material 30 (not shown in detail) can be induced. The manufacturing device 90, in particular the laser 20 and the dispensing device 40, are controlled by a control unit 50 designed to output control commands 55. The control commands 55 are generated by a computer program product 80 that is stored executably in the control unit 50.

[0027] FIG 2 shows schematically a structure of a material layer 12, as it is present during or after irradiation with a laser 20 according to a second step 120 of the claimed method 100. The material layer 12 has a base material 30, which is essentially present as grains 36. The hardening agent 42, which is also present as grains 46, is enclosed in the base material 30. Heat energy 28, which is introduced into the material layer 12, causes a diffusion 48 of the hardening agent 42. The hardening agent 42 is in FIG 2 essentially elemental carbon, which remains in the material layer 12 in the second step 120. The hardening agent 42 is incorporated into the base material 30 by the diffusion 48 and thus locally hardens the base material 30. The thermal energy 28, which causes the diffusion 48, can be supplied in the second step 120 by the laser 20 and / or in the form of process heat, for example, a hardening furnace, in a third step 130. Because the hardening agent 42 can be applied essentially arbitrarily in the claimed method 100, the further diffusion distances that must be covered to achieve a desired target state of the machine component 10 to be manufactured can be minimized. Starting from the target state, a hardening process can follow, which includes heating and quenching.

[0028] In FIG 3 1 shows a schematic sequence of an embodiment of the claimed method 100, with which a machine component 10 is to be produced. In a first step 110, a material layer 12 is provided. The material layer 12 comprises a base material 30, to which a hardening agent 42 is added. The hardening agent 42 is applied to the material layer 12 by means of a dispensing device 40. The dispensing device 40 can be controlled such that a dispensed amount of the hardening agent 42 can be adjusted locally, i.e., at different positions within the plane of the material layer 12. As a result, essentially any desired distribution of concentrations of hardening agent 42 can be achieved. In a second step 120, the material layer 12 is irradiated with a laser 20, by which the material layer 12 is locally melted. As a result, the hardening agent 42 is enclosed at least in the base material 30.The first and second steps 110, 120 are repeated, as indicated in the return loop 140, until the machine component 10 to be manufactured has been produced in its basic form by means of additive manufacturing. This is followed by a third step 130, in which the machine component 10 thus obtained is exposed to an environment in which thermal energy 28 is supplied to it, for example, through a hardening furnace. This causes diffusion 48 of the hardening agent 42 in the base material 30. This can result in a desired final state in the machine component 10.

[0029] An embodiment of a machine component 10 is shown in FIG 4 In detail, FIG 4 an externally toothed gear 16, which is essentially made of a plurality of stacked material layers 12. The material layers 12 are manufactured using a method 100 according to one of the embodiments outlined above.

[0030] FIG 5 shows a detailed view of a surface of a machine component 10, such as in FIG 4 The machine component 10 has a first region 31 in which a first hardness 35 is present. Adjacent to this, a second region 33 is formed in which a second hardness 37 is present. Furthermore, FIG 5 Above, a diagram 70 showing a progression of the existing hardness 72 along the reference line 71 in the horizontal plane in the plane of the drawing. In the first region 31, the hardness 72 is essentially constant within a value range of the first hardness 35. At a boundary 47, there is a transition 38 of the hardness 72. The transition 38 from the value range of the first to the second hardness 35, 37 is essentially formed as a step 39. The machine component 10 in FIG 5 is manufactured using a method 100 according to one of the embodiments described above. This also allows virtually discrete spatial distributions of hardness 72 to be achieved in the machine component 10. As a result, the hardness 72 in the corresponding first and second regions 35, 37 can be specifically adapted to the design requirements of the machine component 10.

Claims

1. Process (100) for additive manufacturing of a machine component (10), comprising the steps of: a) providing at least one material layer (12); b) irradiating the material layer (12) with a laser (20) to effect local melting of the material layer (12); characterized in that in step a) a hardening agent (42) is added to a base material (30) of the material layer (12) in locally adjustable fashion, wherein the addition of the hardening agent (42) is adjustable to the extent that it is specifiable how much hardening agent is added to the material layer (12) of the base material (30) at a selectable site on the surface, with the result that a locally changeable fractional composition of the material layer (12) in terms of the base material (30) and the hardening agent (42) is brought about, and in step b) the hardening agent (42) is at least embedded in the base material (30) by the irradiation with the laser (20).

2. Process (100) according to Claim 1, wherein a subsequent hardening is prepared by the the embedding of the hardening agent (42) in the base material (30) and in a further step (c) the machine component (10) constructed from a plurality of laser-irradiated material layers (12) in step (a) and (b) is hardened by supplying thermal energy.

3. Process (100) according to Claim 1 or 2, characterized in that in step a) a concentration gradient for the hardening agent (42) in a plane defined by the material layer (12) is adjusted.

4. Process (100) according to any of Claims 1 to 3, characterized in that after step b) the machine component comprises a first region having a first hardness and a second region having a second hardness, wherein the first region and the second region are adjacent to one another with the result that a transition from the first hardness to the second hardness occurs at a common boundary between regions, wherein the transition from the first hardness to the second hardness is in the form of a discrete step.

5. Process (100) according to any of Claims 1 to 4, characterized in that the hardening agent (42) is added to the base material (30) using a dispensing apparatus, wherein an opening duration, opening extent and / or conveying pressure may be adjusted on a dispensing nozzle of the dispensing apparatus to effect local adjustment of the dispensing quantity of the hardening agent (42).

6. Process (100) according to any of Claims 1 to 5, characterized in that in step b) the hardening agent (42) is at least partially dissolved in the base material (30) .

7. Process (100) according to Claim 6, characterized in that an intensity of the laser (20) to initiate a diffusion of the hardening agent (42) into the base material (30) is adjustable.

8. Process (100) according to any of Claims 1 to 7, characterized in that a dispensing quantity of the hardening agent (42) is locally specifiable.

9. Process (100) according to any of Claims 1 to 8, characterized in that in a further step c) a hardening of the machine component (10) to effect a diffusion (48) of the hardening agent (42) in the base material (30) is performed.

10. Process (100) according to any of Claims 1 to 9, characterized in that the hardening agent (42) is in the form of carbon powder or carbon liquid.

11. Process (100) according to any of Claims 1 to 10, characterized in that the base material (30) is an ironbased alloy, a manganese alloy or a nickel-based alloy.

12. Process (100) according to any of Claims 1 to 11, characterized in that at least the steps a) and b) are repeatedly performed for a plurality of material layers (12) .

13. Computer program product (80) that may be executed in a memory of a control unit (50) and is configured for issuing commands (55) to at least one dispensing apparatus (40) for a hardening agent (42) and to a laser (20), characterized in that the computer program product (80) is configured for executing at least one process (100) according to any of Claims 1 to 12 such that upon execution of the computer program product (80) in the control unit (50) the control unit (50) causes a dispensing apparatus for a base material (30), the dispensing apparatus (40) for the hardening agent (42) and the laser (20) to execute the steps of the process (100) according to any of Claims 1 to 12.

14. Control unit (50) comprising a processor and a memory (54) for controlling a manufacturing apparatus (90), characterized in that the control unit (50) is provided with a computer program product (80) according to Claim 13 and is configured such that upon execution of the computer program product (80) in the control unit (50) the control unit (50) causes a dispensing apparatus for a base material (30), the dispensing apparatus (40) for the hardening agent (42) and the laser (20) to execute the steps of the process (100) according to any of Claims 1 to 12.

15. Manufacturing apparatus (90) comprising a dispensing apparatus (40) for a base material and a dispensing apparatus (40) for a hardening agent (42) and a laser (20) for additive manufacturing of machine components (10), characterized in that the manufacturing apparatus (90) includes a control unit (50) according to Claim 14.