Method for the additive manufacturing of a workpiece by fused deposition with structural reinforcement by injection molding of channel-like hollow structures

Abstract

Method for the additive manufacturing of a workpiece (200) according to the fused deposition modeling method, wherein the workpiece (200) to be manufactured is built up layer by layer from a first plastic (K1), wherein during the build-up of the workpiece (200) the layers (210) with overlapping voids (211) are formed, so that channels (212) extending through the layers (210) are formed, wherein it is provided that the positions of the voids (211) are varied from layer (210) to layer (210) so that undercut offsets result between the superimposed voids (211), and / or that the shapes and / or sizes of the voids (211) are varied from layer (210) to layer (210) so that channels (212) with undercut channel contours result from the superimposed voids (211), characterized by the fact that the channels (212) formed with undercut channel geometries are injected with a second plastic (K2), thereby forming corresponding reinforcing elements (215) which extend through the relevant layers (210) and connect these layers (210) to each other and achieve a positive locking anchoring effect between the relevant layers (210), wherein the second plastic (K2) has a higher strength than the first plastic (K1), and wherein the first plastic (K1) and the second plastic (K2) are thermoplastics and the temperature of the second plastic (K2) during injection molding of the channels (212) is 5 K to 20 K above a melting temperature of the first plastic (K1), so that during injection molding the first plastic (K1) melts and a material-bonded connection can form.

Description

[0001] The invention relates to a method for the generative manufacturing of a workpiece using the fused layer method.

[0002] The generative or additive manufacturing of all types of workpieces is becoming increasingly important. A common method of generative manufacturing is the fused deposition method (FFF method or fused filament fabrication). In this method, the workpiece to be manufactured is gradually built up from a plastic, particularly a thermoplastic, in a computer-controlled manner (e.g., based on CAD data of the workpiece). The plastic, provided e.g. as a thread (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, each of which is traversed line by line with the print head, resulting in a layered or layer-by-layer structure. The deposited plastic cools, hardens, and bonds with the previously applied plastic.

[0003] In workpieces produced using this type of 3D printing process, a pronounced anisotropy develops. This means that a finished workpiece exhibits different mechanical properties depending on its direction. Within a layer, the strength and impact strength are comparatively high. Perpendicular to the layers, the strength and impact strength are significantly lower, so that the workpiece usually fails at the interfaces between the layers when subjected to mechanical stress.

[0004] WO 2016 / 083797 A1 describes a plastic filled with dimensionally shaped glass flakes for printing workpieces. Angled glass flakes protruding above the surface of a first printed layer provide a rough surface, allowing a second printed layer applied to the first layer to adhere better.

[0005] DE 10 2014 110 505 A1 proposes the use of 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 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, which has a central filament and structures protruding outward from it. To form the three-dimensional object, the starting material can be extruded through an extrusion nozzle. Afterward, before the matrix material solidifies, the initially folded structures can expand radially outward, forming a scaffold that reinforces the matrix material and improves the surface for the deposition of the next layer.

[0007] WO 2016 / 146374 A1 relates to a method for producing a 3D-printed object, in particular including a functional component. The invention also relates to such a task per se, which can be achieved, for example, with such a method. The invention further relates to a 3D printer that can be used, for example, in such a method for producing a 3D-printed object, in particular including a functional component.

[0008] DE 10 2015 115 793 A1 relates to a method suitable for producing both complex and stable objects of various sizes. It comprises producing an object structure using a generative manufacturing process and / or by means of an injection molding process, as well as producing a fiber-reinforced resin layer in at least one partial area of ​​the object structure.

[0009] US 2017 / 0 197 359 A1 relates to a product and a method for producing ceramic and / or ceramic hybrid materials by producing a printed die. The printed die, which is produced by three-dimensional printing or additive manufacturing processes, has both an external and an internal geometry.

[0010] The invention is based on the object of specifying a method for generative manufacturing or production of a workpiece according to the melt layer method, which does not have, or at least only to a reduced extent, at least one disadvantage associated with the prior art.

[0011] The problem is solved by the subject matter of the invention claimed in the independent patent claim.

[0012] The problem is solved by the subject matter of the invention claimed in the independent patent claims. Further developments and refinements of the invention arise analogously for all subject matter of the invention from the dependent patent claims, the following description of the invention, and the figures.

[0013] The method according to the invention provides that during the (layer-by-layer) construction of the workpiece, i.e. during the manufacture of the workpiece or during the printing process, the layers made from a first plastic are formed with overlapping voids or free spaces, i.e. when the layers are created, voids are also created which then lie on top of one another when they are layered, so that channels are created which extend through or extend through the layers in question and which are then, i.e. during the construction of the workpiece, injected with a second plastic.

[0014] With the molten layer method, it is possible to incorporate hollow structures, and in particular channel-like hollow structures, into the workpiece to be produced by creating corresponding empty spaces or free spaces in each layer, e.g. by interrupting the plastics application. This is used according to the invention to form channels or reinforcement channels in the workpiece which extend over several layers (see below) or, if necessary, through all layers and which are finally filled by injecting another material component (a second plastic or, if necessary, metal), thereby forming corresponding reinforcement elements which extend through the layers in question and connect these layers to one another. During injection molding, undercut cavities orChannel geometries are filled so that the resulting reinforcing elements can achieve an effective anchoring effect between the respective layers. The cross-section of the channels should not be too large, but on the other hand, not too small. For example, the channels can have an average cross-sectional area of ​​0.25 mm. 2 to 40.00 mm2, preferably from 1.00 mm2 to 20.00 mm2, have.

[0015] These reinforcing elements provide structural reinforcement to the workpiece, improving strength perpendicular to the layers and eliminating or at least reducing existing anisotropy. Furthermore, compressive strength, shear strength, flexural strength, and other properties are also improved in other directions. Such reinforcing elements can be incorporated throughout the workpiece or only in areas subject to particularly high stress.

[0016] The hollow structures are formed by injecting the second plastic component during the additive manufacturing of the workpiece. This means that channels can be continuously created and injected during the additive manufacturing of the workpiece until the workpiece is finished. This includes various variants. For example, a channel can be injected whenever it is to be closed with the next layer. A channel, especially a longer one, can also be injected in sections, for example, at regular intervals after a certain number of layers have been created. The injected plastic can harden through cooling and / or chemical reaction.

[0017] The channels or the reinforcing elements arranged therein can extend through or across at least two, preferably at least five and in particular at least ten layers.

[0018] The positions of the voids can be varied from layer to layer, resulting in undercut offsets between the overlapping voids and thus undercut channel contours. Likewise, the shapes and / or sizes of the voids can be varied from layer to layer, resulting in channels with undercut channel contours from the overlapping voids. Furthermore, the channels in a workpiece can be identical or different. In principle, it is possible to design each channel, and thus also the reinforcement element formed within it, differently.

[0019] The first plastic is preferably a thermoplastic. The second plastic, which functions as a reinforcement material, is also preferably a thermoplastic. The first plastic and / or the second plastic can, however, also be a thermoset (e.g., a synthetic resin). The first plastic and the second plastic are preferably different or at least differently specified plastics; however, the first plastic and the second plastic can also be identical. Both the first plastic and, in particular, the second plastic can comprise reinforcing fibers, in particular short and / or long fibers formed from common fiber materials. Instead of a second plastic, a low-melting metal alloy (e.g., a tin alloy) can also be used to inject the channels. A low-melting metal alloy is, in particular, a metal alloy that has a melting temperature that is approximately (e.g.,+ / - 10 K) of the processing temperature and preferably the melting temperature of the first plastic.

[0020] The processing temperature (melting or reaction temperature) of the second plastic can be below the processing temperature of the first plastic. However, it is preferably provided that the temperature of the second plastic during injection into the channels is slightly, e.g., by 5 K to 20 K or by 5 K to 10 K, above the processing temperature or melting temperature of the first plastic. As a result, the first plastic melts during injection, allowing a material bond to form. It is also preferably provided that the second plastic has greater strength, in particular compressive and tensile strength, than the first plastic in order to enable clear mechanical improvements.

[0021] Preferably, the workpiece is manufactured or constructed based on a CAD model of the workpiece, with the channels formed by the voids being pre-defined in the CAD model, which is achieved through appropriate pre-design or modeling. The implementation can be accomplished by a control device (see below).

[0022] 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 particularly good crash performance.

[0023] The invention offers the following advantages (not an exhaustive list): - at the interfaces between the layers, the stiffness, strength and impact or fracture toughness are increased; - manufacturing-related anisotropies are eliminated or at least reduced, thereby improving the mechanical workpiece properties and simplifying the workpiece or component design (design and calculation) - sometimes even almost isotropic workpiece or component properties can be achieved; - local reinforcement adapted to the load path is possible, which enables both load-adapted workpiece or component structures and very high levels of lightweight construction; - expanded range of applications for correspondingly manufactured components, particularly 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-limiting manner with reference to the schematic figures. The features shown in the figures and / or explained below may, even independently of specific combinations of features, be general features of the invention and may further develop the invention accordingly. Fig. 1 illustrates the method according to the invention and shows an apparatus according to the invention for carrying out the method. Fig. 2 shows in several sectional views further reinforcement variants according to the invention, which can be used with the device from Fig. 1 can be produced.

[0025] Fig. 1 shows a device 100 for the additive manufacturing of a workpiece 200 using the melt layer method. The device 100 has a print head 120, which extrudes molten first plastic K1 through a nozzle (extrusion nozzle) 125, thereby building up or depositing the workpiece 200 layer by layer. The layer thickness of the layers 210 is, for example, in a range from 0.005 mm to > 1.0 mm. A thermoplastic K1 is used, in particular, to build up the workpiece 200. The plastic K1 can comprise reinforcing fibers F. A feed system 130 for the first plastic material K1 is assigned to the print head 120. The device 100 further has an injection molding head 140 with an injection molding nozzle 145, which is arranged downstream of the print head 120 in the travel direction R and is arranged, in particular, in the direct vicinity of the print head 120. The injection molding head 140 is provided with a feeding or supply system 150 for feeding orSupply with a second plastic material K2. The print head 120 and the injection molding head 140 are movably mounted or mounted on a common carrier or gantry system 110.

[0026] During the creation or printing of the workpiece layers 210, superimposed voids 211 of different sizes and diameters are formed. The superimposed voids 211 are connected to one another, creating channel-like hollow structures 212 that extend through the respective layers 210 in the build direction and have undercut channel contours. The voids 211 are created, for example, according to a predetermined pattern that may already be created in the CAD model of the workpiece 200. The channels 212 formed by the superimposed voids 211 function as reinforcement channels and are injected with a second plastic K2 by the injection molding head 140 during the workpiece build, thereby creating reinforcement elements 215 that are integrated into the workpiece 200. This means that the reinforcement elements 215 are created or formed directly in the workpiece 200.This can be clearly seen in the detailed view, where the left channel 212 is not yet sprayed.

[0027] The channels 212 can be filled with the second plastic K2 after a predetermined number of layers 210 have been formed, whereby it can be determined in advance when which channel 212 is to be filled. The channels 212 are not filled with the first plastic K1 by the print head 120. Nevertheless, the plastics K1 and K2 can be identical (see above). A thermoplastic K2, which can also contain reinforcing fibers, is preferably used for the reinforcing elements 215. In principle, several different plastics can also be used to fill the channels 212 (analogous to multi-component injection molding).

[0028] Due to the alternating undercut channel contours, a positive anchoring effect is achieved with the injected reinforcing elements 215 across the interfaces (between the layers 210), which stably holds the respective layers 210 together. The number, arrangement, cross-sectional areas, and geometries or contours of the channels 212 and the reinforcing elements 215 created therein influence the mechanical properties of the workpiece 200. This also allows the mechanical properties to be adapted to the technical requirements. Fig. 2 shows analogous to Fig. 1 shows further reinforcement variants according to the invention with different channel geometries or contours. The sectional views show injected and still empty channels 212. In the Fig.In the variant shown in Figure 2c, the channels 212 overlap and form a continuous cavity structure. The reinforcing elements 215 form a corresponding reinforcing structure. List of reference symbols 100 device 110 Portal, support system 120 print head 125 nozzle 130 feeding system 140 injection molding head 145 injection molding nozzle 150 feeding system 200 workpieces 210 layer, position 211 blank space 212 channel 215 Reinforcing element F Reinforcing fibers K1 first plastic K2 second plastic R travel direction

Claims

[1] Method for the generative production of a workpiece (200) according to the melt layer method, wherein the workpiece (200) to be produced is built up layer by layer from a first plastic (K1), wherein during the construction of the workpiece (200) the layers (210) are formed with superimposed voids (211) so that channels (212) extending through the respective layers (210) are formed, wherein it is provided that the positions of the empty spaces (211) are varied from layer (210) to layer (210), so that undercut offsets result between the superimposed empty spaces (211), and / or that the shapes and / or sizes of the empty spaces (211) are varied from layer (210) to layer (210), so that channels (212) with undercut channel contours result from the superimposed empty spaces (211), characterized by , that the channels (212) formed with undercut channel geometries are injected with a second plastic (K2), whereby corresponding reinforcing elements (215) are formed which extend through the respective layers (210) and connect these layers (210) to one another and which achieve a positive anchoring effect between the respective layers (210), wherein the second plastic (K2) has a higher strength than the first plastic (K1), and wherein the first plastic (K1) and the second plastic (K2) are thermoplastics and the temperature of the second plastic (K2) when injecting the channels (212) is 5 K to 20 K above a melting temperature of the first plastic (K1), so that during injection the first plastic (K1) melts and a material-to-material connection can form. [2] Method according to claim 1, characterized bythat the channels (212) extend through at least two, preferably at least five and in particular at least ten layers (210). [3] Method according to one of the preceding claims, characterized by that the workpiece (200) is constructed based on a CAD model of this workpiece (200), wherein the channels (212) formed by the empty spaces (211) are created in the CAD model.

Images