3D printing process

Abstract

3D printing process (M3) with the following steps: Local injection (M31) of a plasma at a working area of ​​a 3D printing device (10), wherein the plasma has a comprising a surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride; and Laser sintering or laser melting (M32) of a powder mixture (Ps) in a selective laser sintering process or a selective laser melting process in the working area of ​​the 3D printing device (10), wherein the powder mixture (Ps) comprises a sintering component selected from the group consisting of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations and metallic alloys.

Description

TECHNICAL AREA OF INVENTION

[0001] The invention relates to a method for 3D printing, in particular for the production of components with improved material properties in the aerospace sector. TECHNICAL BACKGROUND

[0002] Stereolithography (SLA), selective laser sintering (SLS), and selective laser melting (SLM) belong to the group of additive manufacturing processes and are commonly referred to as "3D printing." These processes generate data sets based on geometric models, which are then used in a specialized additive manufacturing system to produce objects of predefined shapes from shapeless materials such as liquids and powders, or from shape-neutral semi-finished products like strips, wires, or webs, using chemical and / or physical processes. 3D printing processes employ additive manufacturing, in which the starting material is built up layer by layer in predefined shapes.

[0003] 3D printing processes are currently widespread in the production of prototypes and in rapid product development (RPD), where a resource-efficient process chain is used for the on-demand production of customized components in small and large series. 3D printing processes find diverse applications in civil engineering, architecture, dental technology, toolmaking, implantology, industrial design, the automotive industry, and the aerospace industry.

[0004] 3D printers, and especially laser sintering devices, use a computer-aided design (CAD) system on the one hand and a blasting system on the other. The blasting system performs the additive layer-by-layer build-up of the object to be printed based on the digital manufacturing model provided by the CAD system. A three-dimensional CAD model of the object to be printed undergoes a processing procedure, known as "slicing," to generate the control data necessary for the blasting system. In this process, the CAD model is digitally sliced ​​into layers of a predefined uniform thickness with layer normals along the build direction of the blasting system. These layers then form the basis for controlling the energy beam at the surface of the starting material in the blasting system. A conventional layer slicing algorithm maps the CAD model onto a tiled surface model, resulting in a large number of closed curves.Surface polygons are created, which define the so-called "slices" between two model sections that are successive perpendicular to each other through the setup direction of the blasting system.

[0005] Such surface models can be stored, for example, in the STL format commonly used for stereolithography, which describes the surface geometry of the three-dimensional object to be printed as raw data of unstructured triangular textures. The blasting system reads the surface model data and converts it into a corresponding control pattern for the laser beam in an SLA, SLS, or SLM manufacturing process.

[0006] 3D printing processes such as SLA, SLS, or SLM offer considerable design freedom in the production of complex three-dimensional components and elements with regard to their geometric shape and structure. A similar degree of freedom would be desirable in shaping the specific material properties of the printed components and elements.

[0007] Several prior art applications attempt to create this freedom: CN 103,567,352 A discloses a composition for selective laser sintering of pre-coated sand particles, comprising raw sand, a binder, a curing agent, and a lubricant. CN 1,309,514 C discloses a metal powder composition for selective laser sintering, comprising 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. US 5,182,170 A discloses a laser sintering process in which the sintered materials react with the ambient atmosphere. US 6,814,926 B2 discloses a powder mixture for selective laser sintering comprising a steel alloy, a binder, and high-temperature resistant particles.Document US 2014 / 0134334 A1 discloses a 3D extrusion process in which a surface coating is applied to the extruded filaments in front of the extrusion head.

[0008] The publications: DE 199 09 882 A1, DE 10 2010 055 201 A1, US 2007 / 0 110 608 A1, US 2007 / 0 290 409 A1, WO 01 / 56 736 A2 and DE 69 511 881 T2 disclose further prior art. SUMMARY OF THE INVENTION

[0009] One of the objectives of the invention is therefore to find solutions for objects produced using additive manufacturing processes with improved material properties, in particular by using selective laser sintering processes, selective laser melting processes or stereolithography processes.

[0010] These and other tasks are solved by a 3D printing process with the features of claim 1.

[0011] According to one aspect, a first 3D printing process therefore comprises the steps of mixing a sintering component, selected from the group of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations and metallic alloys, with at least one surface coating component, selected from the group of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride, in a powder mixture, and laser sintering or laser melting of the powder mixture in a selective laser sintering process or a selective laser melting process.

[0012] According to one aspect, a second 3D printing process comprises the steps of generating a protective gas atmosphere in a 3D printing device, wherein the protective gas of the protective gas atmosphere contains a surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide, and cerium fluoride, and of laser sintering or laser melting of a powder mixture in a selective laser sintering process or a selective laser melting process. The powder mixture contains a sintering component selected from the group consisting of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations, and metallic alloys.

[0013] The 3D printing method according to the invention comprises the steps of locally injecting a plasma into a working area of ​​a 3D printing device, wherein the plasma has a surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride, and of laser sintering or laser melting of a powder mixture in a selective laser sintering process or a selective laser melting process in the working area of ​​the 3D printing device, wherein the powder mixture has a sintering component selected from the group consisting of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations and metallic alloys.

[0014] According to one aspect, a powder mixture for use in a 3D printing process comprises a sintering component selected from the group of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations and metallic alloys, and at least one surface coating component selected from the group of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride.

[0015] A key aspect of the invention is to modify a conventional 3D printing process by introducing reactants into the printing process in situ that improve or alter the material properties of the finished printed object. This causes a local change in the material properties of the starting material for the 3D printing process during the printing operation.

[0016] 3D printing processes are particularly advantageous because they enable the production of three-dimensional components using traditional forming methods, without requiring specialized tooling tailored to the component's shape. This allows for highly efficient, material-saving, and time-saving manufacturing processes for parts and components. Such 3D printing processes are especially beneficial for structural components in the aerospace industry, where a wide variety of components, tailored to specific applications, are used. These components can be produced using 3D printing processes at low cost, with short lead times, and with minimal complexity in the required manufacturing equipment.

[0017] Advantageous designs and further developments result from the additional sub-claims as well as from the description with reference to the figures.

[0018] According to one embodiment of the 3D printing process, laser sintering or laser melting can be carried out under a protective gas atmosphere. In one embodiment, the protective gas of the protective gas atmosphere can comprise a surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide, and cerium fluoride.

[0019] According to one embodiment of the 3D printing process, the powder mixture can have at least one surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride.

[0020] According to one embodiment of the 3D printing process according to the invention, the sintering components can each be selected from the group consisting of gold, platinum, palladium, nickel, chromium, iron, aluminium, molybdenum, beryllium, copper, magnesium, cobalt, tin or an alloy thereof.

[0021] According to one embodiment of the powder mixture, the sintering component can be selected from the group consisting of gold, platinum, palladium, nickel, chromium, iron, aluminium, molybdenum, beryllium, copper, magnesium, cobalt, tin or an alloy thereof.

[0022] The above embodiments and further developments can be combined with one another as appropriate. Further possible embodiments, further developments, and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention. BRIEF SUMMARY OF THE FIGURES

[0023] The present invention will be explained in more detail below with reference to the exemplary embodiments shown in the schematic figures. These figures show: Fig. 1. A schematic illustration of a 3D printing device, Fig. 2 a schematic illustration of exemplary details of a 3D printing device of the Fig. 1 for carrying out the method according to the invention, Fig. 3 A schematic illustration of exemplary details of a 3D printing device of the Fig. 1 according to a further embodiment, Fig. 4 A schematic illustration of exemplary details of a 3D printing device of the Fig. 1 according to a further embodiment, Fig. 5 a schematic illustration of exemplary details of a 3D printing device of the Fig. 1 according to a further embodiment, Fig. 6 a block diagram of an initial 3D printing process, Fig. 7 a block diagram of a second 3D printing process, and Fig. 8 a block diagram of the 3D printing process according to the invention.

[0024] The accompanying figures are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain the principles and concepts of the invention. Other embodiments and many of the aforementioned advantages become apparent with reference to the drawings. The elements of the drawings are not necessarily shown to scale. Directional terminology such as "above," "below," "left," "right," "over," "below," "horizontal," "vertical," "front," "back," and similar terms are used for explanatory purposes only and are not intended to limit the general public to specific embodiments as shown in the figures.

[0025] In the figures of the drawing, identical, functionally equivalent and similarly acting elements, features and components - unless otherwise stated - are each provided with the same reference symbols. DESCRIPTION OF EXAMPLES OF EXECUTION

[0026] 3D printing processes within the meaning of this application encompass all additive manufacturing processes in which objects of predefined shape are produced from shapeless materials such as liquids and powders, or from shape-neutral semi-finished products such as strip, wire, or web-shaped material, using chemical and / or physical processes in a special additive manufacturing system, based on geometric models. 3D printing processes within the meaning of this application employ additive processes in which the starting material is built up layer by layer in predetermined shapes. 3D printing processes include, in particular, stereolithography (SLA), selective laser sintering (SLS), and selective laser melting (SLM).

[0027] Fig. Figure 1 shows a schematic illustration of a 3D printing device 10. The 3D printing device 10 can be, for example, a system for selective laser sintering, a system for selective laser melting, or a stereolithography system. In the following, the 3D printing device 10 will be explained using SLS as an example.

[0028] An energy source, for example a CO2 laser 1, emits an energy beam selectively onto a specific part of the surface of powdered material Ps, which rests on a work platform 3a in a working chamber 3. For this purpose, an optical deflection device or scanner module 2, such as a movable or tiltable mirror, can be provided, which deflects the laser beam L onto a specific part of the surface of the powder Ps depending on its tilt position.

[0029] At the point of impact of the laser beam L, the powder Ps is heated, causing the powder particles to melt locally and form an agglomerate upon cooling. Based on a digital manufacturing model provided and, if necessary, prepared by a CAD system, the laser beam L scans the powder surface. After the selective melting and local agglomeration of the powder particles in the surface layer of the powder Ps, excess, non-agglomerated powder Pd can be transferred to an excess container 5. The work platform 3a is then lowered, and fresh powder Pr is transferred from a powder reservoir 4 with a reservoir platform 4a into the work chamber 3 using a leveling roller 6 or another suitable doctor blade or roller device.The powder Pr from powder reservoir 4 can be preheated to a working temperature just below the melting temperature of the powder using infrared light to accelerate the melting process.

[0030] In this way, a three-dimensional sintered or "printed" object B is created from agglomerated powder in an iterative, generative build-up process. The surrounding powder serves to support the part of object B built up to that point, so that no external support structure is necessary. Through the continuous downward movement of the work platform 3a, object B is created layer by layer.

[0031] The entire printing device 10 can be housed in a casing 7, in which an atmosphere conducive to the laser sintering process can be generated by a suitable supply device 8. For example, a vacuum can be created in the casing 7. Alternatively, a passivating atmosphere with an inert gas mixture such as argon and / or nitrogen can also be generated by the supply device 8.

[0032] In the Fig. Figures 2 to 5 are exemplary schematic illustrations of details of the 3D printing device 10. Fig. 1 in the area of ​​Chamber 3. The ones in the Fig. The embodiments shown in Figures 2 to 5 illustrate specific precautions that can be taken in selective laser sintering or selective laser melting processes to improve the material properties of three-dimensional objects B produced in such processes. It should be clear that features and feature groups of objects produced in one of the Fig. The exemplary embodiments described in sections 2 to 5 can also be applied to the other exemplary embodiments.

[0033] Fig. Figure 2 shows the working chamber 3, in which an injection nozzle 9 is additionally arranged. A plasma can be selectively injected into the 3D printing device 10 via the injection nozzle 9, particularly at a working area in the working chamber 3 on the surface of the powder Ps. The injected plasma can be enriched with lubricants, electrolytes, or other surface-active components to improve the material properties during the laser sintering or laser melting of the powder Ps for the production of the 3D object B. The plasma can contain at least one surface coating component that can achieve the desired material improvements through thermal chemical reactions during laser sintering or laser melting.Such surface coating components can be selected from the group of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride.

[0034] Fig. Figure 3 shows the working chamber 3, in which a protective gas containing surface coating components can be introduced into the housing 7 via the supply device 8 to create a protective gas atmosphere A in the vicinity of the laser sintering or laser melting process in the 3D printing device 10. Similar to in Fig. 2. The protective gas serves to improve the material properties of the powder Ps during the 3D printing process.

[0035] In Fig. Figure 4 shows the working chamber 3 with a powder mixture P which, in addition to the sintered material, already shows surface coating components mixed in. Fig. Figure 5 shows the working chamber 3, in which both the powder mixture P of the Fig. 4 as well as via the feed device 8 of the Fig. Three surface coating components can be added to the 3D printing process to improve material properties.

[0036] The Fig. 6, Fig. 7 and Fig. Figure 8 each shows a block diagram of a schematic sequence of a 3D printing process, which takes place in a 3D printing device such as the 3D printing device in Fig. 1 can be implemented. The various 3D printing processes M1, M2, and M3 presented can each draw on corresponding considerations, as they relate to the Fig. 2 to 5 have been explained.

[0037] In a first 3D printing process M1, a step M11 is performed in which a sintering component, selected from the group of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations and metallic alloys, is combined with at least one surface coating component, selected from the group of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride, in a powder mixture P. This powder mixture P is then subjected in a step M12 to laser sintering or laser melting in a selective laser sintering process or selective laser melting process.Laser sintering or laser melting can be carried out under a protective gas atmosphere, for example, a protective gas atmosphere in which the protective gas used also contains a surface coating component selected from the group of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride.

[0038] In a second 3D printing process M2, a protective gas atmosphere is first generated in a 3D printing device 10 in step M21. The protective gas of the protective gas atmosphere contains a surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide, and cerium fluoride. Finally, laser sintering or laser melting can be carried out under this protective gas atmosphere in step M22, in which a powder mixture Ps is subjected to a selective laser sintering process or a selective laser melting process. The powder mixture Ps can contain a sintering component selected from the group consisting of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations, and metallic alloys.Here too, the powder mixture Ps can contain at least one surface coating component in addition to the sintering component, which is selected from the group of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride.

[0039] In the 3D printing process M3 according to the invention, a plasma is locally injected into a 3D printing device in step M31. This injection can be selectively performed at a working area of ​​a 3D printing device 10 on a powder surface of a powdered starting material for 3D printing a 3D object. The plasma comprises a surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide, and cerium fluoride. At the point where the plasma is locally injected into the 3D printing device 10, a powder mixture Ps is then laser sintered or laser melted in a selective laser sintering process or a selective laser melting process in step M32.The powder mixture Ps includes a sintering component selected from the group of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations and metallic alloys.

[0040] In all 3D printing processes M1, M2, and M3, the sintering component can be selected from, for example, the group consisting of gold, platinum, palladium, nickel, chromium, iron, aluminum, molybdenum, beryllium, copper, magnesium, cobalt, tin, or an alloy thereof. The selection of aluminum or an aluminum alloy as the sintering component can be particularly advantageous, as aluminum is very prone to unwanted oxidation in conventional 3D printing processes due to its high reactivity with its environment.

[0041] The 3D printing processes M1, M2, and M3 can improve the material properties of object B: For example, the sintered particles of the powder mixture can be coated with a surface finish during the laser sintering or laser melting process to prevent unwanted oxidation. Alternatively or additionally, the sintered particles of the powder mixture can be more easily carburized or nitrided, particularly in 3D printing processes with steel and steel alloys or aluminum and aluminum alloys.

[0042] Furthermore, the addition of surface treatment materials during the 3D printing process can improve the lubrication or electrical conductivity properties of the printed object B. Lubricating particles such as graphene, graphite, carbides, or sulfides can contribute to this. Electrical conductivity can generally be improved by conductive additive particles, which can significantly enhance the contact conductivity, particularly on the surface of printed objects B.

[0043] Especially in the production of press-fit bushings made of aluminum or aluminum alloys using laser sintering or laser melting processes, the contact points on the outside of the press-fit bushings can be made significantly more reliable by using lubricating and / or electrical conductivity-enhancing additives during the 3D printing of the press-fit bushing.

[0044] The described methods can be used in all areas of the transport industry, for example for road vehicles, rail vehicles or watercraft, but also in engineering and mechanical engineering in general.

[0045] In the preceding detailed description, various features have been summarized in one or more examples to improve the clarity of the presentation. However, it should be clear that the above description is merely illustrative and in no way limiting. It serves to cover all alternatives, modifications, and equivalents of the various features and embodiments. Many other examples will be immediately and directly clear to the person skilled in the art based on their technical knowledge, given the above description.

[0046] The exemplary embodiments were selected and described to best illustrate the principles underlying the invention and its practical applications. This enables those skilled in the art to optimally modify and utilize the invention and its various exemplary embodiments with regard to the intended purpose. In the claims and the description, the terms "including" and "comprising" are used as neutral language terms for the corresponding terms "comprehensive." Furthermore, the use of the terms "a," "a," and "an" is not intended to fundamentally exclude multiple features and components described in this way. LIST OF REFERENCE MARKS 1 laser 2 Optical deflection device 3 Chamber of Labor 3a Work platform 4 Powder reservoirs 4a Reservoir platform 5 excess containers 6 leveling roller 7 cases 8 Feed device 9 injection nozzle A protective gas atmosphere B Printed object L laser beam M1 procedure M11 Procedure step M12 Procedure step M2 procedure M21 Procedure step M22 Procedure step M3 procedure M31 Procedure step M32 Process step P Powder mixture Excess powder Pr Reservoir Powder P.S. Tool powder

Claims

[1] 3D printing process (M3) with the following steps: Local injection (M31) of a plasma at a working area of ​​a 3D printing device (10), wherein the plasma has a comprising a surface coating component selected from the group consisting of boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, cesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride; and Laser sintering or laser melting (M32) of a powder mixture (Ps) in a selective laser sintering process or a selective laser melting process in the working area of ​​the 3D printing device (10), wherein the powder mixture (Ps) comprises a sintering component selected from the group consisting of ceramic materials, ceramic material combinations, metallic materials, metallic material combinations and metallic alloys. [2] 3D printing process (M3) according to claim 1, wherein the sintering component is selected from the group consisting of gold, platinum, palladium, nickel, chromium, iron, aluminium, molybdenum, beryllium, copper, magnesium, cobalt, tin or an alloy thereof.

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