Patent Application
20210354184
The present invention relates to a method for manufacturing a product with a spatially structured surface from a semi-finished product, a semi-finished product for plastic forming thereof into a product with a spatially structured surface, and such a product.
Semi-finished products are to be understood as intermediate goods which consist of a raw material and which have already been brought into a basic geometric shape. In particular, semi-finished products within the meaning of the present application are plates, shells and/or discs made of metal, plastic, wood, artificial stones and/or mixtures thereof.
A spatially structured surface is to be understood as a surface that is characterized by different depths and heights, creases, bumps and/or elevations compared to a smooth unmachined surface.
In order to produce products with a spatially structured surface from a semi-finished product, it is usually necessary to perform a corresponding forming operation, which is usually introduced into the semi-finished product by means of deep drawing or mechanical folding processes. Products with such surfaces are also sometimes milled from the solid. However, as the spatial structure increases, the necessary forming energy increases strongly, which means that considerable forces are introduced into the semi-finished product, especially in the case of complex or pronounced geometries of the product. This can be a disadvantage, particularly in the case of semi-finished products made from composite plates, since the multilayer structure should not be destroyed in order to ensure the function of the composite plate even after forming. In the case of solid plates, the main disadvantage is that with increasing thickness, even greater amounts of energy are required to process the semi-finished product accordingly.
To counter this problem, in the prior art several separate semi-finished parts are usually assembled to form a complete product. Occasionally, cuts are also made in the semi-finished product to interrupt a force flow in the material of the semi-finished product. In both cases, the approach is to interrupt force flows in the semi-finished product by means of cut edges.
In many cases, the production of the cuts is quite complex and often such cut edges are also undesirable. This is the case, for example, when the spatially structured surface is intended to create specific visual impressions while at the same time fulfilling functional tasks, such as the impermeability or function of a full-surface covering, a facade part, cabinet element or the like. In such cases, it is particularly desirable for the product to have a surface that is as uniform as possible and free of gaps.
With this background, it is the task of the invention to demonstrate a considerably simplified method for manufacturing a product with a spatially structured surface and a semi-finished product for plastic forming of the same into a product with a spatially structured surface.
The solution of the task is achieved with the method according to claim 1 and the semi-finished product according to claim 16 as well as the product according to claim 32. Advantageous further embodiments of the invention are described in the respective subclaims.
The method according to the invention is therefore characterized by the fact that a patterned target bending location is created in the semi-finished product, and that the semi-finished product is then subjected to a pressure over its surface which is dosed in such a way that the pressure causes plastic deformation of the semi-finished product along the target bending location, so that a product with an overall spatially structured surface is produced.
The method according to the invention thus initially starts with the generation of a relatively complexly shaped target bending location in the semi-finished product. In general, the target bending location is a local reduction of the bending stiffness of the semi-finished product generated in any way, e.g. by weakening the thickness, but always along a pattern. This can be a regular and/or irregular pattern. The pattern of the structural weakenings or the target bending location can consist of any known basic geometries and/or of free geometries. It may be patterns within patterns. It can consist of linear, non-linear, of intersecting and/or non-intersecting lines, polylines, splines, circles, etc. Logos, fonts, drawings are also possible.
It is particularly important that a more complex shape of the target bending location is produced compared with a simple, e.g. linear shape, along which a relatively large-area plastic deformation then occurs in a subsequent method step of pressure application or forming, which can be carried out all the more quickly for this. In this way, the spatially structured surface can be produced very simply and quickly.
The plastic forming process therefore only has to be performed to overcome the locally reduced bending stiffness in the target bending location and no longer to overcome the bending stiffness of the original semi-finished product without target bending location. This means that considerably simpler and lower-energy forming processes can be used.
In this context, pressure is generally understood to mean a force per unit area applied to the semi-finished product during forming, which acts on at least one surface of the semi-finished product. It is important that this two-dimensional application of force results in a pressure gradient in the semi-finished product which leads to forming. Depending on how pronounced the target bending locations are, the pressure required for plastic forming can be correspondingly low. The application of the pressure or the associated forming can be carried out by using any suitable means. For example, a differential pressure device may be used. Also, the applied pressure can be a negative or positive pressure.
In particular, it is advantageous that the forming process does not have to be set up exactly to the geometry of the patterned target bending location, as is the case, for example, with the deep-drawing process or a pressing process. In particular, no special stamp geometries or molded parts have to be produced in order to produce the desired shape of the semi-finished product. Rather, it is the case that the various partial surfaces simply form along the pattern of the target bending location when the appropriate forming work is applied. The shape of the pattern of the target bending location does not have to correspond exactly to the partial surfaces to be produced. Rather, the pattern provides a basic structure along which the partial surfaces are formed. The spatially structured surface is therefore to be regarded as the sum of the partial surfaces that are formed on the basis of the inserted target bending location.
The specific introduction of a patterned target bending location is based on the knowledge that the relatively complex structure of the target bending location can be introduced into the undeformed semi-finished product with relatively little effort before the forming process. At the same time, the local plastic deformation that occurs along this patterned target bending location leads to the formation of a spatially stabilized surface in virtually a single step, despite any weakening of the cross section. This is also due to the fact that a larger number of partial surfaces are formed during forming as a result of the patterned target bending location. These form a mutually stabilizing, spatial surface structure of offset partial surfaces that compensates for the original cross-sectional weakening. If care is taken to ensure that the target bending location does not cut through or perforate the semi-finished product, the result is still a closed surface even after forming.
In other words, the patterned target bending location forms a folding structure with a spatially multi-structured surface during forming, which results in a high strength of the product due to the spatial stabilization of the folding structure created in this way. This is greater than the strength that would be achieved with only a single fold of a conventional target bending location.
The patterned target bending location is further produced by arranging at least one recess, which preferably extends from a surface of the semi-finished product in the direction of the interior of the semi-finished product or vice versa, in the semi-finished product. The recess can be formed by a recess of any desired cross-section. For example, a V-shape, a U-shape, a rectangular shape, a semicircular shape, etc. is conceivable.
It is particularly advantageous if at least one recess is at least partially linearly and/or several recesses are arranged along an imaginary line. The recesses can therefore be at least partially groove-like. In this way, patterned target bending locations can be created in the semi-finished product in a simple manner.
At least one linear recess can be at least partially rectilinear and/or curved, in particular spiral. Linear recesses with a straight course are particularly easy to manufacture.
It is also conceivable that several recesses are arranged along at least one at least straight and/or partially curved line in the semi-finished product. Thus, with several recesses aligned in such a specific manner, a patterned target bending location can also be created in a simple manner.
Advantageously, at least one recess is created in the semi-finished product in such a way that its depth and/or width changes at least partially along the pattern of the target bending location. For example, the recess can be more pronounced or less pronounced in the edge region of the surface of the semi-finished product than in the central region of the semi-finished product. Alternatively, and/or additionally, specific individual lines, curves of the recess or a subset of recesses may be more pronounced or weaker than lines, curves or subsets of recesses at other locations on the semi-finished product. This has the advantage that the subsequent contour of the product with a spatially structured surface can thus be specified even more precisely, since the extent of the forming correlates with the intensity with which the recess is formed.
Due to the structural weakenings with different depths and/or widths introduced in this way, the reduced cross sections of the semi-finished product have correspondingly reduced stiffnesses with a progression along the pattern of the target bending location. In the subsequent forming process, there are correspondingly different resistances in the pattern of the target bending location which have to be overcome to “buckle out” along the weakenings. Depending on the residual cross section, therefore, a different defined critical forming pressure is required. Areas with a small residual cross section will buckle early at low forming pressures, areas with a larger residual cross section only at higher forming pressures. Thus, the course of the forming process or the setting of the forming geometry can be controlled by a specific arrangement but also by the shaping of the structural weakenings as a function of the residual cross section. This enormously increases the design scope, ensures the reproducibility of the shapes and enables smooth transition areas within the structure weakening geometry. Critical forming areas can be localized by numerical analysis and early failure can be prevented by appropriate selection of the geometries of the recess or the target bending location.
The patterned target bending location can be at least partially designed as a spiral structure. The spiral structure can be angular and/or round. In any case, conically bulged products can be produced in a very simple manner.
Also, the patterned target bending location can be designed at least partially as a meshed structure, preferably with an open-cell and/or closed-cell structure. By meshed structure is meant in general a pattern composed of several lines (straight as non-straight) and/or points. Thus, the meshed structure can be created by one or more appropriately shaped line-shaped recesses or also by a plurality of punctiform and/or short line-shaped recesses set along imaginary lines. The areas correspondingly outlined by the recess or recesses can be compared to cells or meshes of a net. During forming, the surfaces defined in this way ensure that a number of partial surfaces, which move out of the original shape (which can be a flat surface but also a simple shell shape) of the semi-finished product and are angled towards each other, are formed.
In this context, the meshed structure of the patterned target bending location can at least partially have a closed-cell and/or open-cell structure. The closed-cell structure has the advantage over an open-cell structure that the mesh structure is defined by a weakened cross-section along the complete circumferential line of the cell. Thus, during forming, it is relatively well ensured that relatively clearly defined partial surfaces angled towards each other are formed. The open-cell structure has the advantage that, especially in relatively close-meshed patterns, not too many recesses meet in a node. A mixture of both structures combines their advantages.
A particularly suitable meshed structure is a polyhedral pattern, which can, for example, be made up of triangles or contain triangles. Thus, any variations of polygons can be present in the pattern. By using polyhedral patterns, so-called stealth surfaces can be created in the product.
Preferably, the recess is formed thermally, mechanically, chemically and/or by applying material next to the target bending location. Thermal manufacturing may be understood to mean, for example, a melting or baking of the recess. Mechanical manufacturing may be understood to mean, for example, a machining, displacement or similar process. Chemical manufacturing, for example by etching, is also conceivable. The machining processes include processes with a geometrically determined cutting edge, such as screwing, drilling, countersinking, milling and broaching, as well as those with a geometrically undetermined cutting edge, such as grinding honing, lapping, beam machining and sliding machining. A displacing process is understood to mean, for example, the pressing of a profile or geometry into a surface of the semi-finished product. The advantage here is the cost-effective use of such processes for processing the semi-finished product. The term material application covers all processes which apply an additional layer, coating or other object to the surface which results in an increase in the bending stiffness at the point in question—i.e. next to the bending location.
Advantageously, overpressure and/or underpressure is applied to at least one surface of the semi-finished product. In particular, the pressure can be applied variably, uniformly and/or alternately. A variable pressure is generally understood to mean a time-dependent pressure gradient which occurs during forming. In particular, the variable pressure can exhibit gradual, uniform and/or abrupt pressure changes. The pressure change can be either purely in the overpressure or underpressure range, or alternating from the overpressure to the underpressure range or vice versa. A variable pressure has the advantage that the plastic forming can be controlled or triggered more precisely.
Further, a pressure medium is used to apply the pressure. This can be a fluid, a foam, a sand, a plate with an elastic surface and/or the like. The fluid can be compressible, such as a gas, gas mixture, in particular air, or incompressible, such as a liquid, in particular water, or an oil, in particular a hydraulic oil. The use of a fluid, has the advantage that a locally constant pressure is achieved over the surface of the semi-finished product. As no pressure peaks are formed, the forming of the semi-finished product is more predictable and gentle on the material.
It may be useful to apply a protective cover to at least one of the first surface and/or the second surface of the semi-finished product before applying pressure to the semi-finished product. By a protective cover is meant, in very general terms, a sheet or layer which makes it possible to prevent the pressure medium from coming into direct contact with the semi-finished product surface in question during the forming process. This can have several advantages. Firstly, it can ensure that the pressure medium does not escape during forming through any perforations that may be present in the semi-finished product. Secondly, wetting or direct contact in general between the pressure medium and the semi-finished product surface can be avoided. The protective cover is preferably applied after insertion of the target bending location and before forming of the semi-finished product.
It may be useful for the semi-finished product to be formed against a damping means. The damping means can be an elastic object which comes into contact with the semi-finished product during the entire forming process or only towards the end of the forming process. The damping means can be arranged statically or carried along during the forming process. Advantageously, excessive forming of the semi-finished product in places or over large areas can be avoided and the forming process as a whole can be better controlled. This is particularly helpful if the forming takes place at high strain rates, quickly and/or generated by high amounts of energy.
In a preferred further development, the semi-finished product and/or a pressure medium is heated in such a way that the plastic forming of the semi-finished product is favored. The heating can have a purely material-related influence on the bending stiffness of the semi-finished product, which is the case, for example, when a softening temperature is reached, or a reaction-related influence, which means that when the temperature limit is reached a chemical process takes place which reduces the bending stiffness of the semi-finished product.
Preferably, two layers of the semi-finished product are joined together to manufacture the product in such a way that sufficient pressure for forming can be applied between the two layers of semi-finished product. In this case, plastic deformation occurs in accordance with the target bending location, which is introduced on at least one surface of the multilayer semi-finished product. The advantage here is that for example a cushion-like surface structure can be produced with little effort.
On the equipment side, the problem can be solved with a semi-finished product for plastic forming into a product with a spatially structured surface which has a patterned target bending location with at least one recess. The advantages already described above with regard to the method are achieved here.
Preferably, the at least one recess of the patterned target bending location extends from a surface of the semi-finished product in the direction of the interior of the semi-finished product or vice versa. Also, the target bending location may further comprise a second recess extending from a second surface of the semi-finished product towards a first surface of the semi-finished product or vice versa. The second recess may thereby comprise a single recess or a plurality of recesses. Preferably, the second recess may also comprise a pattern, such as a polyhedral pattern. In order to support the forming process, the second recess can be arranged congruently with the first recess in the semi-finished product. This results in a cross-sectional weakening that is effective from both sides. Alternatively, it can also be arranged offset to it. In this way, additional kinks can be created in the surface of the semi-finished product. As previously described, the target bending location also comprises both the first and the second recesses in the sense of this further embodiment. It is essential to the invention that the target bending location provides the basic pattern for the subsequent spatially deformed surfaces of the product.
In an expedient manner, the patterned target bending location has at least one recess which is linear and has an at least partially rectilinear and/or curved, in particular spiral, course.
The patterned target bending location can also have several recesses arranged along an at least partially rectilinear and/or curved line. Then several specifically aligned recesses form the patterned target bending location in its entirety.
Advantageously, the patterned target bending location has at least one recess whose depth and/or width changes at least partially along the pattern. For example, the recess can be more pronounced or less pronounced in the edge region of the surface of the semi-finished product than in the central region of the semi-finished product. Alternatively, and/or additionally, specific individual lines, curves of the recess or a subset of recesses may be more pronounced or less pronounced than lines, curves or subsets of recesses at other locations on the semi-finished product. This has the advantage that the subsequent contour of the product with a spatially structured surface can thus be specified even more precisely, since the extent of the forming correlates with the intensity with which the recess is formed.
It is further advantageous that the target bending location has at least one recess in the form of a perforation. The perforation can be continuous or only partially continuous. The perforation can be introduced both along a specific fold or a corner of a polyhedron. The perforation can be introduced perpendicularly or inclined with respect to the semi-finished product surface. If the perforation is not continuous, it can be present both from one surface and from both surfaces of the semi-finished product. It is always advantageous that the perforation, as part of the target bending location, represents a particularly simple weakening of the bending stiffness.
A cross-section of the recess can also be designed in such a way that when the semi-finished product reaches a defined forming angle α at the recess, further forming of the semi-finished product is inhibited by the formation of a touch contact in the cross-section of the recess. A touch contact can be understood, for example, as a stop of two flanks of the recess. For example, this can be done by the recess having a U-shaped or V-shaped cross section, which is formed accordingly. This has the advantage that not only the start of the forming is initiated by the recess, but also the end of the forming is predetermined by the recess.
The semi-finished product is advantageously made of a thermally, chemically and/or mechanically activatable plastic. By activatable plastic is meant a plastic that is plastically deformed by thermal, chemical and/or mechanical influence. It can therefore be a thermoplastic, for example. The use of reactive plastic has the advantage that the bending stiffness of the target bending location can be at least temporarily reduced or increased by a specific chemical reaction.
According to an advantageous further development, the semi-finished product comprises a composite material having at least an outer layer and a core layer, the patterned target bending location being arranged in at least one of the layers. A suitable composite material may have an outer layer and/or a core layer of metal, ceramic, glass, stone (natural stone and/or artificial stone), plastic and/or wood or mixtures thereof. For example, a known and well-suited composite material has two outer layers of aluminum and a core layer of a polymer plastic, a well-known trade name for which is Alucobond. Composite materials generally have the advantage that different material properties can be bundled. For example, they can have high bending stiffness, high flatness and weather resistance in the outer layer with an overall light weight due to a lightweight core layer.
Preferably, the first and/or second recess of the target bending location penetrates an outer layer at least partially. This is particularly advantageous in the case of a material in the outer layer that is particularly resistant to bending, as it makes forming much easier.
It can also be useful if the semi-finished product has two interconnected semi-finished product layers, at least one of the semi-finished product layers having a target bending location. It may be useful for the manufacture of the same that a suitable means for introducing the pressure is arranged on at least one semi-finished product layer. This may be a fluid filler neck for supplying the pressure medium. After plastic forming, the pressure medium can be discharged from the multilayer semi-finished product. The pressure medium can be, for example, air, which is temporarily pressed into the empty space between the semi-finished product layers or sucked out to such an extent that a pressure sufficient for plastic forming is generated. In all the cases described, the patterned target bending location can be formed in whole or in part on at least one of the surfaces of a semi-finished product layer.
Alternatively, the two layers of semi-finished product can be connected by a frame-like bar running around the edge, so that a defined initial distance is established between the two layers. A deformed structure (convex, concave, mixed convex-concave) can then be produced by applying overpressure or underpressure or alternating overpressure and underpressure. In order to be able to introduce the overpressure, for example with a fluid, between the two semi-finished product layers, a valve can be arranged in the frame-like bar.
Accordingly, a semi-finished product, which already has an internal cavity in its initial state, can also be formed. At least one spacer can also be introduced into such a cavity. If a vacuum is then generated, the respective spacer presses into the semi-finished product and in this way generates an additional deformation effect by the spacer limiting the deformation at the point.
The patterned target bending locations can be located on all main surfaces of the two semi-finished product layers. However, any combination of surfaces on which a patterned target bending location is formed is conceivable. In a preferred further development, the patterned target bending location is formed on both inward-facing semi-finished product layers. This has the advantage that the patterned target bending locations are not visible from the outside.
Finally, the solution to the problem is also achieved with a product having a spatially structured surface which has been produced from a semi-finished product as described above and/or by such a method. Here, too, the advantages described above are achieved.
The invention is explained in more detail below with reference to several embodiments shown in the drawings. Therein schematically show:
The semi-finished product 1 shown in
Since the meshed target bending location 4 has a polyhedral pattern in the plan view of the plate-shaped semi-finished product 1 (in this example, made up of several triangles), a correspondingly spatially structured surface in the form of a polyhedrically structured spatial pattern will also be formed as a result of the forming process. This will therefore consist of a large number of polyhedron surfaces angled towards each other, also in spatial dimension.
In the embodiment shown in
In the drawing shown in
The forming itself is performed by generating pressure between the two layers of semi-finished products 1a and 1b, which are still flat and lying on top of each other in the initial situation. For this purpose, for example a liquid or gaseous pressure medium 14 is pressed between the two layers of semi-finished products 1a and 1b. Based on the highly simplified example, this results in a product 10 with a cushion-like shape, the surfaces of which are structured or folded in a multiple and meshed manner.
As can be seen in the example shown in
As shown in
If a vacuum is introduced between the two semi-finished product layers 1a and 1b, the deformation pattern shown in
Alternating overpressure and underpressure can result in alternating inward and outward indentations in the semi-finished product layers 1a and 1b along the patterned target bending locations 4 and their recesses 5, as can be seen from the dashed line indicated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 218 842.4 | Nov 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/079723 | 10/30/2019 | WO | 00 |
