Method for additive production of components using metal-plastic powder mixtures

Abstract

In particular, the proposed solution relates to a method for the additive production of a component (B), in which a powdered printing material is applied in layers. A metal-plastic powder mixture having a metal portion (10) and a plastic portion (11) is used as a printing material. After the application of the metal-plastic powder mixture, before the at least partially remaining metal fractions (10) of the applied metal-plastic powder mixture are connected by heat input to form a section of the component (B) to be produced having the solid metal structure (4, 4A-4E), the metal fractions (10) of the applied metal-plastic powder mixture are connected by heat input to form the metal structure (4, 4A-4E). The plastic portion of the metal-plastic powder mixture is at least partially evaporated by heat input.

Description

Technical Field

[0001] The proposed solution relates in particular to a method for additive manufacturing of a component. Background Art

[0002] It is also known that powdered printing materials are used in the additive manufacturing of components and components are created in layers. The powdered printing material is applied in layers to the printing platform of the 3D printing device. Generally, additive manufacturing of components that should be composed of plastic materials and metals in proportions is not without difficulties. It is particularly important here that the melting points of plastics and metals are very different from each other. In order to form a solid or solid section of the component to be manufactured made of metal, the metal printing material is melted or sintered. However, the temperature required for this sometimes significantly exceeds the melting temperature of the plastic, so that the applied plastic material may be destroyed. Summary of the invention

[0003] The object of the present solution is therefore to provide an improvement in the additive manufacturing of components made of metal and plastic.

[0004] This object is achieved by the method according to claim 1 or 14 and by the 3D printing device according to claim 15 or the use according to claim 17 .

[0005] According to a first aspect of the proposed solution, a metal-plastic powder mixture having a metal portion and a plastic portion is used as the printing material. After the metal-plastic powder mixture is applied, the plastic portion is at least partially evaporated (and thus partially removed) by heat input before the at least partially remaining metal portion of the applied metal-plastic powder mixture is connected by heat input.

[0006] The basic idea of ​​the proposed solution is therefore a method in which a metal-plastic powder mixture is used in order to apply a metal component and a plastic component together during the printing process, but then to remove the plastic component by evaporation, so that the remaining metal can be connected, i.e., for example, melted or sintered (to form a section of a solid metal structure with a component to be produced). In this case, by evaporating the plastic component, the metal component can be exposed in a locally limited manner. In other words, by the for example locally limited and targeted evaporation of the plastic component of the applied metal-plastic powder mixture, only a metal-containing, plastic-free powder is provided, so that, for example, in a subsequent process step, only the metal component remaining locally can be melted or sintered, without the plastic being melted or sintered together.

[0007] In principle, the at least partial, in particular only partial, i.e. locally limited, evaporation of the plastic component is carried out only after a plurality of (at least two) layers of the metal-plastic powder mixture have been applied, and in this case in particular in a plurality of applied layers. Thus, in this embodiment variant, the plastic component is evaporated only after a plurality of layers of the metal-plastic powder mixture have been applied. The evaporation of the plastic component can also be carried out in layers, i.e. layer by layer, or across a plurality of layers.

[0008] In at least one embodiment variant, it is provided that before the metal portion remaining at least partially is connected, at least one additional layer of a metal-plastic powder mixture is applied to the area (one or more layers) of the applied metal-plastic powder mixture (in which the plastic portion has been evaporated in the first process step to form a metal structure). Here, the application of at least one additional layer of a metal-plastic powder mixture can be used for shrinkage compensation. Therefore, due to the evaporation of the plastic portion (if necessary in a defined and locally limited area and compared with the adjacent area), less material is present. By applying one or more additional layers of a metal-plastic powder mixture, the corresponding reduction in the layer thickness can be compensated again. In this case, it can also be provided that the connection of the metal portion is carried out in the subsequent second process step, that is, the connection of the metal portion is carried out only after the plastic portion has also been evaporated in at least one applied additional layer in advance. Therefore, the metal portion of the additional layer can also be connected together in the second process step. Therefore, the metal portion of one or more applied additional layers is also melted or sintered together, for example, in order to produce a larger metal structure. Here, at least one (additional) applied additional layer can be measured with respect to the volume of its metal portion, so that the volume of evaporated plastic material is compensated.

[0009] A first laser beam of a first wavelength is used, for example, for evaporation of a plastic component, while a second laser beam of a second wavelength is used for connecting a metal component, wherein the second wavelength is smaller than the first wavelength. Here, it is utilized that, depending on the wavelength, plastic materials and metals generally absorb laser beams in different intensities. Therefore, plastic materials, especially polymers, for example, absorb laser beams of smaller wavelengths (for example, ≤1µm) significantly worse than metals. At the same time, laser beams of larger wavelengths (for example, ≥6µm or ≥8µm) are reflected by metals and are therefore not absorbed, while plastic materials, especially polymers, absorb such laser beams as necessary through the additives provided here. Therefore, for example, with the aid of a first laser beam generated by a first laser with a larger wavelength (for example, a CO2 laser), plastic materials can be evaporated in a targeted manner, while the corresponding first laser beam has no effect or almost no effect on the metal component of the applied metal-plastic powder mixture. In addition, by means of a laser beam of a smaller wavelength, for example, a green or blue laser beam generated by a second laser (which is not absorbed by plastic materials but absorbed by metals), the connection of metal components by melting or sintering can be achieved.

[0010] In an embodiment variant, a plastic material is provided for the plastic portion of the metal-plastic powder mixture, which plastic material ashes under the influence of the metal melt adjoining thereto. Thus, if necessary, a polymer, for example, is provided as a plastic material by adding corresponding additives, which ashes in the region adjoining the metal melt under the influence of the high temperature of the adjoining metal melt in order to produce a metal structure based on the metal portion, so that the metal melt is thermally isolated from the adjoining printed region of the component by the gray region adjoining the metal melt.

[0011] In principle, the metal-plastic powder mixture can have metal-plastic particles, in particular, consist of metal-plastic particles. In this case, at least a portion of the metal content of the metal-plastic powder mixture is formed by a plurality of metal cores of the metal-plastic particles, and at least a portion of the plastic content of the metal-plastic powder mixture is formed by a plastic sheathing surrounding each metal core. Thus, a plurality of metal-plastic particles are provided, each of which has a metal core and a plastic sheathing surrounding the metal core. The use of corresponding metal-plastic particles facilitates the application of a printing material having metal and plastic in a single printing process, wherein the proposed solution and the different further processing of the plastic and metal portions provided here in subsequent process steps make it possible to form the desired plastic and metal structures of the component to be manufactured.

[0012] In a variant embodiment, the metal structure of the component to be manufactured is formed with the relevant metal content and is additionally provided for connecting the plastic content of the applied metal-plastic powder mixture, at least partially without evaporation, but in particular by melting, sintering or polymerization. Therefore, in this variant embodiment, it is provided that not only an at least partially continuous metal structure is formed from the metal content of the component to be manufactured that is initially present in powder form, but also a plastic structure in which no connection of the powdered metal content is achieved. This includes, for example, a variant in which the metal core of the applied metal-plastic powder mixture is embedded in the plastic structure without connection, and only melted, sintered or polymerized plastic material is present between the metal cores. The metal cores are then embedded in the plastic structure, but are not connected to each other. For example, the plastic structure of the component can be formed by a solidified polymer matrix.

[0013] Here, as already explained above, a targeted connection of powdered plastic portions can be carried out by corresponding laser beams to form a solid plastic structure. Here, in addition to melting or sintering, (additional) polymerization can also be set, especially in the case of a metal-plastic powder mixture that already contains a polymer. Polymerization is particularly understood here as polymerization being excited by laser so that the molecular weight of the formed polymer is greater than the molecular weight of the initial material, which, for example, will return to the plastic sheath of the metal-plastic particles applied and thus printed in a layered manner. For polymerization, the plastic portion can be formed by a thermoplastic polymer, in which a shorter polymer chain is connected to a longer polymer chain. Here, the activation of this mechanism can be either carried out directly by using the energy introduced by the laser beam, or by at least one additive contained in the plastic portion, which is activated by the laser beam and acts as a linking mechanism (Verketter). In addition, thermosetting polymers can be used, especially in combination with a light activator, which is used, for example, in a resin for stereolithography 3D printing (SLA).

[0014] In both cases, the additives used for linking can be activated by heat or light reactions.

[0015] In a variant embodiment, for the component to be manufactured, an anchoring structure is formed by the connected metal portions of the applied metal-plastic powder mixture, which is embedded in the plastic section (formed by the interconnected plastic portions) in the finished component. The anchoring structure is connected to the metal structure subsequently generated by other metal portions that are also interconnected, so that the metal structure and the anchoring structure form a metal solid anchored in the plastic material. Therefore, the anchoring structure, for example, engages the section made of plastic material from the rear on the finished component, so that the metal structure is produced without distortion during the manufacturing process, and is positioned and locked in the plastic material as required. By first forming the anchoring structure (the metal structure is then, for example, melted onto it), distortion during manufacturing can be minimized or even completely avoided. Here, the anchoring structure first manufactured is smaller in size than the metal structure to be manufactured, and the metal structure is additionally fixed in the plastic material in a form-locking manner by the anchoring structure.

[0016] In the component to be produced, for example, at least one metal insert, at least one conductor track or at least one circuit can be formed with connected, initially powdered metal portions. Thus, in the process of the proposed solution, corresponding components made of plastic, in particular polymers, can be printed relatively easily with corresponding metal components. The 3D printing process improved according to the proposed solution makes it possible to produce components with metal components, in particular with relatively complex geometries, without requiring special tools, in particular casting molds, for this purpose.

[0017] The above-described use of laser beams of different wavelengths to connect the printed plastic material and the printed metal is obviously independent of the evaporation of the applied plastic portion described above to provide regions in which only a powdered metal portion is still present, which can then be melted or sintered, for example, without plastic material. Therefore, a further aspect of the proposed solution, independent of this, provides a method for additive manufacturing of a component, wherein plastic material and metal are used for the layer-by-layer construction of the component, and a first laser beam of a first wavelength is used to form the plastic structure (and thus the first solid section) from the applied plastic material, and a second laser beam of a second wavelength is used to form the metal structure (and thus the second solid section) from the applied metal, which second wavelength is smaller than the first wavelength.

[0018] According to the second aspect of the proposed solution, it is not mandatory to apply the plastic material and the metal by means of a metal-plastic powder mixture, each comprising a metal core surrounded by a plastic sheath. However, this is considered advantageous in principle in order to also utilize the above-mentioned advantages of the first aspect of the proposed solution.

[0019] The proposed solution also includes a 3D printing device for additive manufacturing of a component, which is suitable for carrying out one of the proposed methods. In particular, the proposed 3D printing device can be configured to use a metal-plastic powder mixture having a metal portion and a plastic portion as printing material and to evaporate the plastic portion of the metal-plastic powder mixture at least partially by heat input after applying the metal-plastic powder mixture before connecting, in particular melting or sintering, the at least partially remaining (non-evaporated) metal portion of the applied metal-plastic powder mixture by heat input using the 3D printing device (for example in a subsequent process step and using a laser different from the laser used to evaporate the plastic portion).

[0020] Furthermore, it is considered to be advantageous in principle to use a metal-plastic powder mixture in an additive manufacturing process, which has metal-plastic particles, in particular consisting of corresponding metal-plastic particles, each with a metal core and a plastic sheath surrounding the metal core. In practice, corresponding metal-plastic powder mixtures have not yet been used for additive manufacturing of components.

[0021] In particular, it is considered advantageous in this case if the plastic sheath is formed by a polymer. The use of polymers is particularly suitable here in view of the different absorption capacities of laser beams generated as a function of wavelength and striking the respective material compared to metals. Thus, only the polymer portion or the metal portion of the applied powder is heated in a targeted manner by a laser beam of a specific wavelength or a specific wavelength range. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The figures show by way of example possible implementation variants of the proposed solution.

[0023] Figure 1 shows multiple layers of an additively applied metal-plastic powder mixture with metal-plastic particles;

[0024] Figure 2 Absorption-wavelength diagrams of different materials are shown with emphasis on two lasers and their wavelengths for different materials of the metal-plastic powder mixture;

[0025] FIG. 3A to FIG. 3F Different phases in an embodiment variant of the proposed method are shown, wherein in the Figure 2 Using two different lasers, a plastic structure and a metal structure for the component to be produced are produced in a 3D printing device;

[0026] Figure 4 A produced component is shown, in which a metal structure accessible from the surface side is anchored in a polymer matrix via an anchoring structure. DETAILED DESCRIPTION

[0027] Figure 1 The printed layers S1, S2 and S3 of a component to be additively manufactured during a 3D printing process are schematically shown. A metal-plastic powder mixture consisting of metal-plastic particles 1 is used to produce the layers S1, S2 and S3. The metal-plastic particles 1 of the powder mixture each have a metal core 10 which is completely encapsulated by a plastic sheath 11. The metal-plastic particles 1 are particularly Figure 1 The circular cross section visible in the cross-sectional view of and the spherical shape thus produced for example are only exemplary. Of course, other cross-sectional shapes may also be provided.

[0028] During the printing process, the metal-plastic particles 1 are used to apply the metal portion with respect to the metal core 10 and the plastic portion with respect to the plastic sheath 11 in each layer S1, S2 and S3 on the printing platform of the 3D printing device. Thus, the plastic material is printed with the plastic sheath 11, and the metal material is printed with the metal core 10 at the same time. Here, the plastic material for the plastic sheath 11 can be formed by a polymer, for example. The polymer sheath 11 will also be discussed later.

[0029] If with the help of Figure 2 As shown in FIG. D of FIG. 1 , in which the absorption capacity for different materials is plotted as a function of wavelength, different materials absorb (laser) light with different strengths depending on the wavelength. This is used to selectively input heat into different materials of the metal-plastic granules 1. Thus, for example, a first laser LP is provided, for example in the form of a CO2 laser, which generates a laser beam with a relatively high wavelength in the range of 8-12 μm. Due to the relatively low absorption capacity of metals (such as stainless steel or structural steel) in this wavelength range, but the high absorption capacity of polymers, the first laser LP can be used to input heat in a targeted manner into the polymer. The laser beam of the first laser LP with a wavelength in the range of, for example, 10 μm is reflected by the metal and is therefore not absorbed, but is absorbed by the polymer material in the polymer sheath 11. In principle, the corresponding absorption capacity of the polymer can also be adjusted by means of additives added to the polymer material.

[0030] The second laser LM in turn generates a laser beam of a smaller wavelength, for example, in the range of 0.4 µm-0.6 µm. For example, the second laser LM is a laser for generating green or blue laser light. Such a laser beam of a smaller wavelength is well absorbed by metals and is therefore suitable for heating them. However, the polymer material of the polymer sheath 11 is transparent to laser light of this wavelength. Thus, the metal core 10 and the polymer sheath 11 of the already applied metal-plastic powder mixture can be selectively connected, in particular melted or sintered (or (further) polymerized in the case of polymer materials) in a 3D printing device by means of different lasers LP and LM.

[0031] FIG. 3A to FIG. 3E An exemplary sequence of the proposed method is shown in order to construct different solid sections made of polymer material on the one hand and metal on the other hand in a component B to be produced using metal-plastic particles 1. Figure 3A The first process step is applied according to Figure 1 After a layer S1, S2 or S3 or a plurality of layers S1, S2 and S3 of a powder containing metal-plastic particles 1 has been applied, a part of the polymer encapsulation 11 can be selectively influenced by one or more lasers LP. In this case, the respective lasers LP can be operated with different powers, or a single laser LP for inputting heat into the polymer material of the polymer encapsulation 11 can always generate a laser beam of the same wavelength, but be operated with different powers depending on how the polymer material is to be processed in a specific area. Thus, for example, in Figure 3A It is provided that the component sections shown are divided into three regions or groups G1 , G2 , G3 .

[0032] In the first region G1, the laser LP is operated at a relatively low power in order to melt, sinter or (further) polymerize the polymer material of the polymer sheaths 11 so that the individual polymer sheaths 11 are connected to each other and form a corresponding Figure 3B After solidification or cooling, the metal cores 10 are embedded in the polymer matrix of the polymer structure 3 thus formed, without being connected to one another (and therefore without forming any conductive paths).

[0033] For the G2 region adjoining the G1 region, the polymer material of the polymer sheath 11 is evaporated in layers by means of the laser LP. For this purpose, the laser LP is operated with a higher power than for the production of the polymer structure 3 in the region G1. The evaporation of the polymer sheath 11 in the region G2 is finally carried out according to Figure 3D As a result, only the plastic-free metal core 10 is still present in this region G2 .

[0034] However, in this case, due to the evaporation of the polymer sheath 11, the volume of the polymer sheath 11 is reduced from the volume of the corresponding layers S1, S2 and S3, and the printed material shrinks locally. In order to compensate for the shrinkage, according to Figure 3C , one or more additional layers 100 with additional metal-plastic particles 1 are applied in the region G2, in which the polymer sheath 11 was previously evaporated. The shrinkage is thus compensated by the additional layer or layers. The polymer sheath 11 of the additional layer 100 is evaporated again in the region G2 using the laser LP, so that only the metal core 10 is then present again in the region G2. The shrinkage that occurs due to the evaporation of the polymer sheath 11 is thus compensated by the (optional) application of the additional layer 100, wherein only the metal core 10 or the metal powder formed with the metal core 10 is present in the region G2.

[0035] Subsequently, according to Figure 3E The loose metal powder formed by the exposed metal core 10 is sintered or melted by means of an additional second laser LM. The laser beam generated by the second laser LM is transparent to the polymer material, so that deeper layers are not destroyed by transmission. Figure 3F In the region G2 , a metal structure 4 is formed which, after appropriate cooling, forms a solid section made of metal in the component to be produced. This solid section is present adjacent to the solid section made of polymer material in the region G1 .

[0036] In principle, variants are also conceivable in which the polymer material used is of such a type that it ashes in the environment of the metal melt produced by means of the laser LM and the ash produced thereby then provides thermal insulation from the metal melt. Thus, for example, it is also possible in the region G1 to form a previously produced section made of plastic material or a corresponding plastic structure 3 which at least partially ashes under the influence of the subsequently produced metal melt in order to form thermal insulation from the metal melt for the metal structure 4 to be produced.

[0037] With the generated metal structure 3 , for example, metal inserts, conductor tracks or circuits can be defined in the finished component B.

[0038] Figure 4The finished component B is shown, in which the produced metal structure 4E is present in the polymer matrix of the polymer structure 3. In the polymer structure 3, the metal structure 4E (here accessible on the top side by way of example) is anchored in a form-locking manner in the polymer material of the polymer structure 3 via additional anchoring structures 4A, 4B, 4C and 4D made of metal. The respective anchoring structures 4A to 4D are produced here by molten metal in a relatively small area, in particular in an area smaller than the metal structure 4E, in order to avoid deformation of the component B due to twisting. Then, in a further printing process, the metal structure 4E is melted onto the first produced anchoring elements or anchoring structures 4A to 4D (in FIG. 3 by way of example, in cross section, they are designed in a T-shaped manner). In this case, the metal structure 4E can form, for example, conductor tracks in the finished component B.

[0039] In principle, different lasers LM and LP for selectively further processing metal or plastic portions in a printing material containing metal-plastic particles 1 can generate laser beams in a time-staggered manner and thus in different process stages, and in this process, in particular, bring about the connection of the corresponding plastic sheaths 11 or metal cores 10 to one another in layers. However, corresponding connections can also be provided across a plurality of layers.

[0040] Reference numerals list

[0041] 1 powder

[0042] 10 metal core

[0043] 100 additional layers

[0044] 11Polymer sheath

[0045] 3Polymer structure / polymer segment

[0046] 4. 4E Metal Structure

[0047] 4A-4D Anchoring Structure

[0048] D absorption diagram

[0049] G1, G2, G3 areas

[0050] LM, LP lasers

[0051] S1, S2, S3 layers

Claims

1. A method for additively manufacturing a component (B), wherein: The invention relates to a method for applying a powdered printing material in layers, characterized in that a metal-plastic powder mixture having a metal portion (10) and a plastic portion (11) is used as printing material, and that after the metal-plastic powder mixture is applied, the plastic portion (11) is at least partially evaporated by heat input before the at least partially remaining metal portion (10) of the applied metal-plastic powder mixture is connected by heat input.

2. The method according to claim 1, characterized in that The metal portion (10) which remains at least partially after the evaporation of the plastic portion (11) is melted or sintered.

3. The method according to claim 1 or 2, characterized in that: After the application of a plurality of layers (S1, S2, S3) of the metal-plastic powder mixture and in the plurality of applied layers (S1, S2, S3), at least partial evaporation of the plastic portion (11) is carried out.

4. The method according to any one of claims 1 to 3, characterized in that Before the at least partially remaining metal portion (10) is connected, at least one additional layer (100) of the metal-plastic powder mixture is applied to the region (G2) of the applied metal-plastic powder mixture in which the plastic portion (119) was evaporated in a first process step.

5. The method according to claim 4, characterized in that After the plastic portion (11) has also been previously evaporated in at least one applied additional layer (100), the metal portion (10) is connected in a subsequent second process step, so that the metal portion (11) of the additional layer (100) is also connected in the second process step.

6. The method according to any one of the preceding claims, characterized in that The plastic portion (11) is evaporated using a first laser beam with a first wavelength, and the metal portion (10) is connected using a second laser beam with a second wavelength, wherein the second wavelength is smaller than the first wavelength.

7. The method according to any one of the preceding claims, characterized in that A plastic material is provided for the plastic portion ( 11 ) of the metal-plastic powder mixture, which incinerates when influencing the metal melt adjoining it.

8. The method according to any one of the preceding claims, characterized in that The metal-plastic powder mixture comprises metal-plastic particles (1), and in the metal-plastic powder mixture at least a part of the metal content is formed by a plurality of metal cores (10) of the metal-plastic particles (1), each of which is surrounded by a plastic sheath (11) forming a part of the plastic content.

9. The method according to any one of the preceding claims, characterized in that The metal structure (4, 4E; 4A-4D) of the component (B) to be produced is formed with the connected metal portions (11), and it is additionally provided that the plastic portions (11) of the applied metal-plastic powder mixture are connected at least in places without evaporation, but in particular by melting, sintering or polymerization.

10. The method according to claims 8 and 9, characterized in that The plastic encapsulation (11) of a plurality of metal-plastic particles (1) of the applied metal-plastic powder mixture is connected to one another, thereby forming a plastic section (3) of the component (B) to be produced which has metal particles (10) embedded therein but not connected to one another.

11. The method according to claims 6 and 10, characterized in that Before forming a section with a metallic structure (4, 4E; 4A-4D) by generating a metal melt, a plastic section (3) is first formed, wherein the plastic material in ashes in a region of the plastic section adjoining the metal melt by influencing the metal melt.

12. The method according to any one of claims 8 to 10, characterized in that For a component (B) to be produced, anchoring structures (4A-4D) are formed by connected metal portions (10) of an applied metal-plastic powder mixture, which are embedded in a plastic section (3) formed by interconnected plastic portions (11) and are connected to a metal structure (4E) subsequently produced from further metal portions (10) also connected to one another.

13. The method according to any one of the preceding claims, characterized in that At least one metal insert, at least one conductor track or at least one circuit is formed in the component (B) to be produced using the connected metal portion (10).

14. Method for additive manufacturing of a component (B), in particular according to any one of the preceding claims, wherein: The component is constructed in layers using plastic material and metal, characterized in that a first laser beam with a first wavelength is used to form a plastic structure (3) from the applied plastic material, and a second laser beam with a second wavelength is used to form a metal structure (4; 4A-4E) from the applied metal, wherein the second wavelength is smaller than the first wavelength.

15. A 3D printing device for additively manufacturing a component (B), wherein: The 3D printing device is configured to apply a powdered printing material in layers, and is characterized in that the 3D printing device is configured to use a metal-plastic powder mixture having a metal portion (10) and a plastic portion (11) as printing material, and is also configured to, after applying the metal-plastic powder mixture, at least partially evaporate the plastic portion (11) of the metal-plastic powder mixture by heat input before connecting the at least partially remaining metal portion (10) of the applied metal-plastic powder mixture by heat input using the 3D printing device.

16. The 3D printing device according to claim 15, characterized in that: The 3D printing device comprises a first laser (LP) for at least partially evaporating the plastic portion (11) and a second laser (LM) for joining the metal portion (10).

17. Use of a metal-plastic powder mixture in an additive manufacturing process, the metal-plastic powder mixture comprising metal-plastic particles (1), the metal-plastic particles each comprising a metal core (10) and a plastic sheath (11) surrounding the metal core (10).

18. The use according to claim 17, characterized in that The plastic sheath (11) is formed from a polymer.

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