Method for the additive manufacturing of a workpiece by fused deposition with structural reinforcement by reinforcing elements or reinforcing yarn

Abstract

A method for the additive manufacturing of a workpiece (200) using the fused deposition modeling (FDM) method, wherein the workpiece (200) to be manufactured is built up layer by layer from plastic (K) and rod-shaped reinforcing elements (300) are introduced into the workpiece (200) during the build-up of the workpiece (200), which penetrate several layers (210) and connect them together, characterized in that the plastic (K) is applied to the workpiece (200) with a print head (120) and the rod-shaped reinforcing elements (300) are introduced with a placement head (140) following the print head (120), such that the rod-shaped reinforcing elements (300) are introduced vertically and / or obliquely into the respective uppermost layers (210) with the placement head (140) and the respective layers (210) are connected to each other by the rod-shaped reinforcing elements (300) during their introduction. to be donated.

Description

[0001] The invention relates to a first method for the additive manufacturing of a workpiece according to the fused deposition method according to the preamble of claim 1 and a second method for the additive manufacturing of a workpiece according to the preamble of claim 4.

[0002] The additive manufacturing of workpieces of all kinds is becoming increasingly important. A common additive manufacturing process is fused filament fabrication (FFF). In this method, the workpiece is built up gradually from a plastic, especially a thermoplastic, under computer control (e.g., based on CAD data of the workpiece). The plastic, supplied as a filament, is heated until it reaches a liquid or semi-liquid state and extruded through at least one nozzle of a print head. The workpiece is manufactured in individual work planes, which are traversed line by line by the print head, resulting in a layer-by-layer build-up. The deposited plastic cools, hardens, and bonds with the previously applied plastic.

[0003] Workpieces manufactured using this 3D printing process exhibit pronounced anisotropy. This means that a manufactured workpiece displays different mechanical properties depending on its orientation. Within a single layer, the strength and impact resistance are comparatively high. Perpendicular to the layers, the strength and impact resistance are significantly lower, so that under mechanical stress, the workpiece typically fails at the interfaces between the layers.

[0004] WO 2016 / 083797 A1 describes a plastic filled with dimensioned glass flakes for printing workpieces. Angled glass flakes protruding from the surface of a first printed layer provide a rough surface, thus improving the adhesion of a second printed layer applied to the first.

[0005] In DE 10 2014 110 505 A1, it is proposed to use powdered solid particles as adhesion promoters, which are sprinkled onto a previously applied polymer composition, which in particular has just left the extrusion die.

[0006] US Patent 2016 / 0012935 A1 describes a method for the additive manufacturing of a three-dimensional object and a suitable starting material. The starting material comprises a fiber embedded in a matrix material, featuring a central filament and outwardly projecting structures. To form the three-dimensional object, the starting material can be extruded through a die. Before the matrix material solidifies, the initially folded structures expand radially outward, forming a scaffold that reinforces the matrix material and improves the surface for the deposition of the next layer.

[0007] The closest patent, US 2017 / 0182712 A1, describes a process for the generative or additive manufacturing of a component by layer-by-layer application of a meltable plastic. Among other things, one process variant is described (see...). Fig. 6), in which the component is reinforced using wire, yarn or plastic thread or the like, as well as a process variant (see Fig. 8), in which the component is reinforced by means of pin-like elements. When a plastic layer is produced, the wire, yarn, plastic thread or the pin-like elements are inserted into the produced layer with an overhang and, when the next plastic layer is laid down, are formed over it so that the two plastic layers in question are positively joined.

[0008] Regarding the state of the art, reference is also made to the 3D printing process described in US 2017 / 0232674 A1.

[0009] The invention is based on the objective of providing a method for the additive manufacturing or production of a workpiece using the fused deposition modeling method, which does not have at least one disadvantage associated with the prior art, or at least has only a reduced one.

[0010] The problem is solved by the methods claimed in the independent patent claims. Further developments and embodiments of the invention are described in the dependent patent claims, the following description of the invention, and the figures.

[0011] The invention is based on the unified idea of ​​connecting the layers or strata produced successively during the additive manufacturing of a workpiece by means of reinforcing elements (of a type described in more detail below) that penetrate several layers, thereby structurally reinforcing the workpiece. This improves the strength perpendicular to the layers or strata in order to eliminate or reduce existing anisotropy. Furthermore, compressive strength, shear strength, flexural strength, and the like are also improved in other directions. The reinforcing elements can be incorporated anywhere in the workpiece or only in areas subject to particularly high stress.

[0012] The first method according to the invention provides that during the build-up of the workpiece, i.e., during the manufacturing of the workpiece or even during the printing process, rod-shaped reinforcing elements (pins) are inserted into the workpiece, penetrating several layers and connecting them together. The rod-shaped reinforcing elements are inserted vertically and / or obliquely into the respective uppermost layers (su). The layers in question are essentially pinned together by the rod-shaped reinforcing elements, which significantly improves the cohesion of the layers. The rod-shaped reinforcing elements then penetrate two or at least two, preferably three or at least three, and particularly five or at least five adjacent layers. The layer thickness is, for example, in the range of 0.005 mm to ≥ 1.0 mm (i.e., greater than or equal to 1.0 mm). The rod-shaped reinforcing elements have a corresponding length.

[0013] The rod-shaped or rod-like reinforcing elements can be made of metal (e.g., steel, aluminum, or magnesium), glass, carbon, ceramic, or plastic (including fiber-reinforced plastic). The rod-shaped reinforcing elements are dimensionally stable and preferably have a diameter of ≤ 0.5 mm (i.e., less than or equal to 0.5 mm). The rod-shaped reinforcing elements can also be nail-like, e.g., with a point and a flattened end.

[0014] The rod-shaped reinforcement elements are inserted with a setting head following or downstream of the print head that dispenses or applies the plastic to the workpiece, in particular directly or immediately after the plastic has been deposited, such that the rod-shaped reinforcement elements are inserted vertically and / or obliquely into the respective uppermost layers with the setting head and the layers in question are pinned together by the rod-shaped reinforcement elements (300) when they are inserted.

[0015] The setting head can inject the rod-shaped reinforcement elements, e.g., using compressed air, or press or drive them in, e.g., using an electromechanically driven hammer. The setting head can incorporate an ultrasonic exciter (ultrasonic device) that uses vibration to locally melt the plastic at the insertion point (injection or impact point) of the workpiece, thus facilitating the penetration of the rod-shaped reinforcement elements. The vibration can be transmitted to the workpiece via a sonotrode. To further facilitate insertion, the rod-shaped reinforcement elements can also be heated, e.g., by induction.

[0016] The second method according to the invention provides that during the construction of the workpiece, at least one endless reinforcing yarn is embroidered into the workpiece, which penetrates several layers and connects them together.

[0017] The reinforcing yarn (or thread) can be a single fiber (reinforcing fiber) or a roving (fiber bundle) and can be made of plastic or plastic fibers, carbon or carbon fibers, glass or glass fibers, natural fiber or natural fibers, mineral fiber or mineral fibers, metal or metal fibers, and / or the like. Unlike the reinforcing elements, the reinforcing yarn is not dimensionally stable but rather dimensionally unstable or flexible. The reinforcing yarn preferably has a diameter of <_ 0.3 mm (i.e., less than or equal to 0.3 mm).

[0018] The reinforcing thread is stitched in using an embroidery or sewing head following or after the print head, which has at least one needle-like tool, particularly directly after the plastic has been laid down. The stitching is carried out by the needle-like tool repeatedly piercing the uppermost layers vertically and / or obliquely (at an angle), whereby the reinforcing thread is drawn into the stitches and the respective uppermost layers by the needle-like tool and then forwarded to the next stitch, so that the stitching creates a seam through which the affected layers are essentially stitched or sewn together, significantly improving the cohesion of the layers. By alternating the angle of the needle-like tool (and using a corresponding needle guide), a V-shaped stitch can be created, which is particularly strong.

[0019] The needle-like tool can be heated to facilitate insertion. Preferably, heating the needle-like tool at the insertion point on the workpiece causes local melting of the plastic. The molten plastic then embeds the inserted reinforcing yarn, creating a stable bond.

[0020] The plastic used to build the workpiece, particularly meltable plastics, may contain reinforcing fibers, especially short and / or long fibers made from common fiber materials, which exhibit a preferred orientation when the plastic is laid down. When the rod-shaped reinforcing elements are inserted or the reinforcing yarn is stitched in, these reinforcing fibers are locally displaced and / or realigned at the insertion or insertion points according to the insertion or insertion axis. During this alignment, the reinforcing fibers are also pressed through the interfaces between adjacent layers, creating a bridging effect that strengthens the cohesion of the layers.

[0021] The invention can be applied in particular to the manufacture of a motor vehicle component. Motor vehicle components manufactured according to the invention can also exhibit good crash performance.

[0022] A suitable device (3D printer) for the additive manufacturing of a workpiece according to the invention comprises at least the following components: - a print head with which the workpiece to be manufactured can be built up layer by layer, i.e. layer by layer, from plastic; and - a setting head or embroidery head, which is connected downstream of the print head, with which rod-shaped reinforcing elements or at least a reinforcing yarn can be introduced or embroidered into the workpiece during the assembly of the workpiece, as explained above; - and, if necessary, a control device that can control the print head and the type head or embroidery head, in particular, that can control the process according to procedure.

[0023] The invention offers the following advantages (not an exhaustive list): - at the interfaces between the layers, stiffness, strength and impact or fracture toughness are increased; - Manufacturing-related anisotropies are eliminated or at least reduced, thereby improving the mechanical properties of the workpiece and simplifying the workpiece or component design, in particular the layout and calculation - in some cases, almost isotropic workpiece or component properties can even be achieved; - Local load path-oriented reinforcement is possible, which enables both stress-appropriate workpiece or component designs and allows for very high lightweight construction levels; - expanded range of applications for appropriately manufactured components, especially in automotive engineering, preferably also as a replacement for conventionally manufactured metal parts (e.g. die-cast parts) and plastic parts (e.g. injection-molded parts).

[0024] The invention is explained in more detail below by way of example and in a non-restrictive manner with reference to the schematic figures. Fig. Figure 1 illustrates the first method according to the invention and shows a device for carrying out this method. Fig. Figure 2 illustrates the second method according to the invention and shows another device for carrying out this method. Fig. Figure 3 shows a needle-like tool for the device made of Fig. 2. Fig. Figure 4 shows a V-shaped embroidery stitch, which was created using the device made of Fig. 2 is manufactured.

[0025] Fig. Figure 1 shows a device 100 for the additive manufacturing of a workpiece 200 using the fused deposition modeling (FDM) method. The device 100 has a printhead 120 which extrudes molten plastic K through a nozzle 125, thereby building up the workpiece 200 layer by layer. A feed system 130 for the plastic material is associated with the printhead 120. The device 100 also has a placement head 140 located downstream of the printhead 120, or following it in the direction of travel R, and is arranged in close proximity to the printhead 120. The printhead 120 and the placement head 140 are movably mounted on a common support or gantry system 110. With the setting head 140, rod-shaped reinforcing elements 300 are continuously inserted into the workpiece 200 during the ongoing production of the workpiece 200, in particular before the uppermost layer (or row) laid immediately before.The track) 210 has hardened, with the rod-shaped reinforcing elements 300 penetrating several layers 210 and permanently connecting or pinning them together. This is very clearly visible in the detailed illustration.

[0026] The rod-shaped reinforcing elements 300 are, for example, shot or driven into place. In doing so, the reinforcing fibers F, which may be contained in the plastic material K, are also realigned at the relevant points, resulting in an additional reinforcing effect. Further layers can be applied to the top layer 210 of the workpiece 200 in an analogous manner; that is, rod-shaped reinforcing elements 300 are also inserted here. A feeding system 150 for feeding the rod-shaped reinforcing elements 300 is associated with the setting head 140. The setting head 140 can have an ultrasonic exciter 145, which causes local melting of the plastic K on the workpiece 200 to facilitate the insertion of the rod-shaped reinforcing elements 300.

[0027] The in Fig. Device 100 shown in Figure 2 has an embroidery head 160 instead of the previously described setting head. During the ongoing layer-by-layer construction of the workpiece 200, the embroidery head 160 continuously embroiders or sews an endless reinforcing thread 400 into the workpiece 200, penetrating and bonding several layers 210. This is clearly illustrated in the detailed drawing. A feed system 170 for supplying the reinforcing thread 400 is associated with the embroidery head 160.

[0028] The embroidery head 160 has at least one needle-like tool 161, as shown schematically in the Fig. Figure 3 shows the needle-like tool 161, which is formed with a holder 162, a shaft 163, and a tip 164. The yarn 400 is guided along the outside in a loop 410 and then held in place by friction at the point of entry, so that the yarn loop remains in the point of entry. The needle-like tool 161 can also be configured differently. The embroidery head 160 can also have a heating device 165 for heating the needle-like tool 161. The needle-like tool 161 can also be heated directly, e.g., by means of a heating wire coil.

[0029] When embroidering, the needle-like tool 161 can be alternately tilted to create the desired effect. Fig. The V-shaped stitching shown in section 4 can be created. The rod-shaped reinforcement elements 300 can also be inserted in a V-shape. Reference symbol list 100 Device 110 Portal, support system 120 printhead 125 nozzle 130 Feeding system 140 Set head 145 ultrasound exciters 150 feeding system 160 Stickkopf 161 Tool, needle 162 holders 163 shaft 164 Peak 165 Heating system 170 Feeding system 200 workpieces 210 layer, location 300 reinforcement elements 400 reinforcing yarn 410 loop F Reinforcing fibers K plastic R direction of travel

Claims

[1] Method for the generative production of a workpiece (200) according to the melt layer method, wherein the workpiece (200) to be manufactured is built up layer by layer from plastic (K) and during the construction of the workpiece (200) rod-shaped reinforcing elements (300) are introduced into the workpiece (200), which penetrate several layers (210) and connect them to one another, characterized by that the plastic (K) is applied to the workpiece (200) with a pressure head (120) and the rod-shaped reinforcing elements (300) are introduced with a setting head (140) following the pressure head (120), such that the rod-shaped reinforcing elements (300) are introduced vertically and / or obliquely into the respective uppermost layers (210) with the setting head (140) and the respective layers (210) are pinned to one another by the rod-shaped reinforcing elements (300) when they are introduced. [2] Method according to claim 1, characterized bythat the rod-shaped reinforcing elements (300) are made of metal, glass, carbon, ceramic or plastic. [3] Method according to claim 1 or 2, characterized by that the setting head (140) has an ultrasonic exciter (145) which causes local melting of the plastic (K) by vibration on the workpiece (200). [4] Method for the generative production of a workpiece (200) according to the molten layer method, wherein the workpiece (200) to be manufactured is built up layer by layer from plastic (K) and during the construction of the workpiece (200) at least one endless reinforcing yarn (400) is stitched into the workpiece (200), which penetrates several layers (210) and connects them to one another, characterized byin that the plastic (K) is applied to the workpiece (200) with a print head (120) and the reinforcing yarn (400) is embroidered with an embroidery head (160) which follows the print head (120) and has at least one needle-like tool (161), in such a way that the needle-like tool (161) repeatedly pierces vertically and / or obliquely into the respective uppermost layers (210), wherein the reinforcing yarn (400) is drawn into the punctures and the respective uppermost layers (210) with the needle-like tool (161) and is pulled further to the respective next puncture, so that the embroidery creates an embroidery seam by means of which the respective layers (210) are embroidered with one another. [5] Method according to claim 4, characterized by that the needle-like tool (161) is heated. [6] Method according to claim 4 or 5, characterized bythat a V-shaped cross-sectional embroidery seam is produced with the reinforcing yarn (400) by alternately slanting the needle-like tool (161). [7] Method according to one of the preceding claims, characterized by that the plastic (K) has reinforcing fibers (F) which are realigned at the insertion points or puncture points when the rod-shaped reinforcing elements (300) are inserted or when the reinforcing yarn (400) is embroidered.

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