METHOD FOR PRODUCING A COMPOSITE BODY AND COMPOSITE BODY

Description

[0001] The present invention relates to a method for producing a composite body from at least two sub-bodies, wherein at least one of the sub-bodies is produced by an additive manufacturing process, and wherein the at least two sub-bodies are exposed to a solvent atmosphere in a chamber so that a surface of the sub-bodies is smoothed. The at least two sub-bodies are positioned in the chamber such that they touch at at least one joining surface, and thus a metallurgical bond is formed between the at least two sub-bodies at the at least one joining surface by means of the solvent atmosphere. The invention further relates to a composite body produced according to the method.

[0002] Various additive manufacturing or 3D printing processes are known. The objects to be produced are usually built up layer by layer by a printing device. This typically involves the targeted solidification of a material that is initially liquid or loose. Common advantages of these processes include simple, decentralized production and a short time between design and finished product. This is particularly beneficial for the production of prototypes.

[0003] Many additive manufacturing processes require post-processing of the manufactured parts. For example, support structures may need to be removed, or a very rough surface resulting from the manufacturing process may need to be smoothed. One known method for smoothing is to expose parts produced using additive manufacturing to an etching or solvent atmosphere in a suitable chamber. The efficiency of this process can be increased by treating several manufactured parts simultaneously with such an atmosphere.

[0004] For example, such a method is known from DE 10 2015 115 821 A1, which teaches in particular how to treat several bodies simultaneously and to arrange the bodies apart from each other and from the inner walls of the chamber.

[0005] Additive manufacturing processes generally share the disadvantage that, due to the limited volume of the printing device, only bodies of a limited size can be produced. To circumvent this disadvantage, it is known to divide larger bodies into smaller sub-bodies, which are printed individually and later assembled. However, the assembly step is usually very complex and therefore time-consuming and expensive, especially for sub-bodies with intricate structures. US patent applications 2005 / 0026134 A1 and 2012 / 0288672 A1 disclose the joining of two sub-bodies after they have been exposed to a solvent atmosphere. US patent applications 2014 / 0252674 A1 and 2005 / 0208271 A1 disclose the joining of sub-bodies, each of which has a lattice structure.

[0006] The object of the present invention is therefore to provide a method for manufacturing a composite body and a composite body in which an additional step of joining the partial bodies can be saved.

[0007] The problem is solved by a method and a composite body with the features of the independent patent claims.

[0008] In the method for producing a composite body from at least two sub-bodies manufactured using an additive manufacturing process, the at least two sub-bodies are exposed to a solvent atmosphere in a chamber, so that one surface of the sub-bodies is smoothed. The at least two sub-bodies are positioned in the chamber such that they touch at at least one joining surface, and thus a material-bonded connection is formed between the at least two sub-bodies at the at least one joining surface by means of the solvent atmosphere. According to the invention, it is proposed that the at least two sub-bodies be joined together in a form-fitting manner at the at least one joining surface.

[0009] The solvent atmosphere at least partially breaks chemical bonds on the surface of the component parts. This allows the molecules on the surface to rearrange or be removed, thereby reducing surface roughness. Furthermore, this process creates a metallurgical bond between the component parts at the joining surface. A separate joining step for the component parts can thus be eliminated. For example, a component part manufactured using an additive manufacturing process can be joined in this way to at least one component part manufactured using an injection molding process and / or to at least one other component part manufactured using an additive manufacturing process.

[0010] It is conceivable that the components are first placed in the chamber and then the solvent atmosphere is introduced. Alternatively, the components are introduced into a chamber already containing a solvent atmosphere. The solvent atmosphere could be, for example, an aerosol, particularly a mist, i.e., a mixture of an atomized solvent and, for example, air. It is also conceivable to use solvent vapor in pure form or as a gas mixture, again, for example, with air.

[0011] The chamber can be heated to a temperature of 25 to 100 °C, for example, to accelerate the reaction. Preferably, however, the process takes place at room temperature. The solvent atmosphere can be created, for example, by spraying or atomizing the solvent, such as with an ultrasonic atomizer. Controlled evaporation of the solvent is also conceivable.

[0012] Due to the health hazard and potential explosion risk, the chamber is preferably hermetically sealed while the solvent atmosphere is present. It is conceivable that the solvent atmosphere is extracted before the chamber is opened at the end of the process.

[0013] The positive-locking connection of the sub-bodies at the joining surface improves the subsequent cohesion of at least two sub-bodies. Furthermore, this method simplifies the production of a homogeneous composite body. The positive-locking connection can be achieved, for example, by forming the joining surface between the sub-bodies with boundary surfaces of unit cells in a lattice structure of the sub-bodies.

[0014] If the sub-bodies each have a lattice structure, they touch, for example, along the lattice bars of the lattice structure. These lattice bars can, for example, form the edges of unit cells of the lattice structure. The described positive locking can refer to the parallel alignment of the lattice bars. A multitude of joining surfaces can consist of a multitude of pairs of lattice bars aligned in parallel.

[0015] It offers particular advantages if at least one of the component parts is manufactured using a powder-based 3D printing process. Unlike other 3D printing methods, this allows the component parts to be printed without additional support structures. This eliminates the need for subsequent support structure removal.

[0016] In powder-based 3D printing processes, the objects to be printed are built up layer by layer from a powder. This usually begins with the bottom layer, where, for example, a binder applied to a layer of powder hardens and bonds the powder together. The next layer of powder is then applied and also treated with the binder. It is also possible to harden and bond the powder by selectively heating it.

[0017] The printed body is always surrounded by a loose powder environment that protects and supports it. Following this process, the body typically has a rough surface, which is smoothed in the solvent atmosphere as part of the inventive process. Naturally, both or all of the at least two sub-bodies can be produced using the powder-based 3D printing process.

[0018] It is also advantageous if at least one of the two sub-bodies is manufactured with a lattice structure. The lattice structure allows for a large volume to be filled with minimal material. Furthermore, the elasticity of the sub-bodie can be precisely controlled by the lattice structure. This is particularly advantageous in upholstery applications. Ideally, the joining surface of the sub-bodies in the assembled body is no longer discernible, at least not by virtue of any inhomogeneous elasticity. Both or all of the at least two sub-bodies can be manufactured with a lattice structure. Preferably, the lattice structure of the sub-bodies is identical.

[0019] It is advantageous if the at least two sub-bodies are positioned in the solvent atmosphere in such a way that they contact each other at a multitude of joining surfaces, where the multitude of joining surfaces corresponds to a multitude of boundary surfaces of the unit cells of the sub-bodies' structure. This ensures that the structures of the sub-bodies complement each other to form the most uniform structure possible of the assembled body. This improves the homogeneity, particularly with regard to the body's elasticity. The described structure can be any structure composed of a multitude of identical unit cells, i.e., the smallest space-filling building blocks. In particular, the structure is a lattice structure. The boundary surfaces separate the individual unit cells from one another. They do not necessarily have to be filled with material. For example, interconnected lattice bars can also form the edges of a boundary surface.

[0020] Preferably, this aspect is already taken into account during the design or subdivision of the body into sub-bodies before the sub-bodies are manufactured. For example, the lattice structure of the body is separated into the sub-bodies along the boundary surfaces of the unit cells of the structure (so-called "cell-conformal cutting").

[0021] It is also advantageous if the individual components are joined in such a way that a uniform lattice structure of the composite body is created. As already described, this can improve the homogeneity, particularly with regard to the elasticity of the body.

[0022] Especially when the body serves as padding or part of padding with which a subsequent user has direct contact, inhomogeneities in elasticity can be uncomfortable for the user and thus detrimental to the product's economic success. This must be avoided.

[0023] Advantages arise if the at least two sub-bodies are manufactured with at least one connecting element, in particular a connecting joint. Additionally or alternatively, it is advantageous if the at least two sub-bodies can be folded together via the connecting element so that the two sub-bodies abut each other with their corresponding joining surfaces. This ensures flawless assembly of the sub-bodies along the at least one joining surface. In particular, the freedom of movement of the sub-bodies relative to each other can be restricted by one or more joints in such a way that the sub-bodies can only be assembled into the body in one manner. In particular, "folding" the sub-bodies into the body is conceivable. The connecting joint(s) can also be manufactured using the additive manufacturing process. If necessary, the joint can be...The joints can be removed again after the body parts have been joined to form the body.

[0024] In the case of a particularly wide body that exceeds the width of the printing device, it is conceivable to divide the body into at least two printable sub-bodies, which may be connected by the described connecting joint(s). In particular, two connecting joints may be provided.

[0025] Furthermore, it is advantageous if the at least two sub-bodies are made of a thermoplastic, in particular polyamide 12 (PA12), and / or an elastomer, in particular TPU. On the one hand, this simplifies the production of the sub-bodies. On the other hand, after joining the sub-bodies, this results, for example, in an elastically deformable but dimensionally stable body, which can be used in particular as padding.

[0026] Examples of elastomers include vulcanizates of natural or silicone rubber. The abbreviation TPU stands for thermoplastic polyurethane. Polyurethanes are plastics or synthetic resins produced by a polyaddition reaction of dialcohols or polyols with polyisocyanates. Upholstery and thermal insulation materials, in particular, can be advantageously manufactured from foamed TPU. The thermoplastic properties are especially beneficial in the production of products made from these materials.

[0027] It offers particular advantages if the solvent atmosphere contains chloroform, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, hexafluoroisopropanol, pyridine, and / or benzyl alcohol. These solvents are capable of dissolving TPU in particular and are therefore suitable for smoothing the surface of the components and creating a metallurgical bond between them. It is also conceivable to use a mixture of different solvents in the solvent atmosphere. As already described, an aerosol and / or vapor can be generated from these solvents to create the solvent atmosphere.

[0028] The composite body according to the invention is composed of at least two sub-bodies, wherein at least one of the sub-bodies is manufactured using an additive manufacturing process. It is characterized in that it is manufactured according to a method described above. As already described, the body has the advantage that the sub-bodies are joined together during the surface smoothing of the sub-bodies, thus eliminating an additional assembly step during the manufacturing process. Furthermore, the body can have a size that exceeds the build volume of a printing device for an additive manufacturing process. It is conceivable that the body is composed of a plurality of sub-bodies.

[0029] The body has, for example, a lattice structure, wherein the lattice structure is preferably homogeneous over the entire extent of the body. For example, motifs of the lattice structure repeat at regular intervals. The body is made, for example, of an elastomer, and in particular of TPU. The body is designed, in particular, as padding or part of padding with homogeneous elasticity.

[0030] Further advantages of the invention are described in the following exemplary embodiments. These show: Figure 1 a two-dimensional diagram of the partial bodies before assembly, Figure 2 a two-dimensional scheme of the production of the body according to the inventive method, Figure 3 a three-dimensional scheme of the partial bodies before assembly, and Figure 4 a three-dimensional scheme of the composite body.

[0031] In the following description of the figures, the same reference symbols are used for features that are identical and / or at least comparable in the various figures. The individual features, their design, and / or mode of action are usually only explained in detail upon their first mention. If individual features are not explained again in detail, their design and / or mode of action corresponds to the design and mode of action of the already described features with the same or identical effect.

[0032] Figure 1 shows in a two-dimensional scheme two partial bodies 1 which form a body 2 according to the invention (see Figures 2 and 4 ) are joined together in the method according to the invention. The two-dimensional representation serves to illustrate the principle. As a rule, body 2 will have a three-dimensional shape. As in the Figure 1As shown, the two sub-bodies 1 exhibit a matching lattice structure. In this example, the lattice structures have hexagonal unit cells 3, from which the lattice structure is built. Less symmetrical unit cells can also be used. A combination of different lattice motifs as the smallest unit of the lattice is also conceivable.

[0033] The subbodies 1 are bounded in such a way that only complete unit cells 3 are present in the lattice structure. In other words, the subbodies 1 are bounded by boundary surfaces 4 of the unit cells 3. Likewise, a joining surface 5 or a plurality of joining surfaces 5 is provided where the subbodies 1 touch during the process (see also Figure 2 ), formed by a multitude of boundary surfaces 4 of the unit cells 3.

[0034] Figure 2Figure 1 shows a two-dimensional diagram illustrating the inventive method for producing the composite body 2. The at least two partial bodies 1, produced using an additive manufacturing process, are placed in a chamber 6 such that they touch at at least one joining surface 5. A solvent atmosphere 7 is present in the chamber 6. The solvent atmosphere 7 smooths the surface of the partial bodies 1. Furthermore, a material-bonded connection is formed between the partial bodies 1 at the at least one joining surface 5, thereby producing the composite body 2. The precisely matched shape of the partial bodies 1, defined by the boundary surfaces 4 of the unit cells 3, allows the partial bodies 1 to be positively joined.

[0035] The composite body 2 has, in particular, a continuous and homogeneous lattice structure. Ideally, at least one joining surface 5 is no longer recognizable after completion of the process. The solvent atmosphere 7 can be produced in the manner already described. For safety, the chamber 6 is hermetically sealed, for example, during the presence of the solvent atmosphere 7. The component bodies 1 can, for example, be placed in the chamber 6 on supports (not shown) or suspended from hooks (not shown).

[0036] The Figures 3 and 4Figure 1 shows a three-dimensional model of the component body 1 and the assembled body 2. Body 2 has a cuboid shape, with one longitudinal dimension of body 2 exceeding the width of a suitable 3D printing device. For this reason, body 2 is divided into two component bodies 1 before production, each of which is manufactured in a separate 3D printing device.

[0037] When separating body 2 into sub-bodies 1, care is taken to ensure that the unit cells 3 are preserved during the separation process. This guarantees that the sub-bodies 1 can later be assembled in a form-fitting manner. Both sub-bodies 1 and body 2 exhibit a three-dimensional lattice structure. This lattice structure allows for targeted control of the elasticity of body 2. Material-saving manufacturing is possible. The assembled body 2 is suitable, for example, as padding. As in Figure 4As shown, the individual parts of the composite body 2 are no longer recognizable.

[0038] The present invention is not limited to the embodiments shown and described. Modifications within the scope of the claims are possible, as is a combination of the features, even if they are shown and described in different embodiments. Reference symbol list

[0039] 1. Subbody 2. Body 3. Unit cell 4. Boundary surface 5. Joining surface 6. Chamber 7. Solvent atmosphere

Claims

1. Method for producing a composite body (2) from at least two partial bodies (1), wherein at least one of the partial bodies (1) is produced in an additive manufacturing process, wherein the at least two partial bodies (1) are exposed to a solvent atmosphere (7) such that one surface of the partial bodies (1) is smoothed, wherein the at least two partial bodies (1) are placed in the chamber (6) in such a way that they touch at least one joining surface (5) and wherein the solvent atmosphere (7) leads to the creation of a cohesive connection between the at least two partial bodies (1) on the at least one joining surface (5) characterized in that the at least two partial bodies (1) are joined together in a positive-fitting manner on the at least one joining surface (5).

2. Method according to one of the preceding claims, characterized in that at least one of the partial bodies (1) is produced in a powder-based 3D printing process.

3. Method according to one of the preceding claims, characterized in that at least one of the partial bodies is produced with a lattice structure.

4. Method according to one of the preceding claims, characterized in that the at least two partial bodies (1) are placed in the solvent atmosphere (7) in such a way that they touch at a plurality of joining surfaces (5), the plurality of joining surfaces (5) corresponding to a plurality of boundary surfaces (4) of the unit cells (3) of the structure of the partial bodies (1).

5. Method according to one of the preceding claims, characterized in that the partial bodies (1) are joined in such a way that a uniform lattice structure of the assembled body (2) is formed.

6. Method according to one of the preceding claims, characterized in that the at least two partial bodies (1) are produced with at least one connecting element, in particular a connecting joint, and / or are folded together via the connecting element, so that the two partial bodies (1) rest against one another with their corresponding joining surfaces (5).

7. Method according to one of the preceding claims, characterized in that the at least two partial bodies (1) are produced from a thermoplastic, in particular polyamide 12 and / or an elastomer, in particular TPU.

8. Method according to one of the preceding claims, characterized in that the solvent atmosphere (7) contains chloroform, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulphoxide, hexafluoroisopropanol, pyridine and / or benzyl alcohol.

9. Composite body (2) composed of at least two partial bodies (1), with at least one of the partial bodies (1) being produced in an additive manufacturing process, wherein the body (2) is produced according to a method of one of the preceding claims.