EP1917877A1 - Metal product - Google Patents

Abstract

The metal product is produced by a casting process. The product has a base structure with a number of frame sections connected together to a frame. The product has a filling structure with a number of grid sections connected together to a grid structure. The base structure defines a spatial base shape of the product and the filling structure is partially filled by a spatial area defined by the frame. An independent claim is also included for a method for the production of a product made of metal.

Description

Technical area

The invention relates to a product made of metal, wherein the product is produced by means of a casting process. Furthermore, the invention relates to a method for producing such a product.

State of the art

Metal products can be found in many places and in different designs. Many functional items of daily use such. As stands, pedestals, racks, key chains, letter-makers, candlesticks, fittings, toys, Tools etc. are made of metal. But also decorative objects such. As statues or jewelry such as brooches, pendants, finger rings, etc. are often made of metal.

There are also many possibilities for producing such products. These include z. As machining, erosion, forming or dividing machining processes (turning, milling, drilling, grinding, pressing, stamping, forging, casting, etc.) but also other methods such as the joining of several items by means of welding, soldering, screws, rivets, etc.

But just because such products are made of metal, which has a high specific gravity compared to many other materials, they are typically heavy in relation to their size, even if the products themselves are rather small in the range of a few Centimeters. In addition, such products are usually rather expensive, since on the one hand relatively much material is required for their production and on the other hand, the materials used are relatively expensive compared to plastics, for example. These disadvantages apply in particular to products which are made of solid material.

Furthermore, many of the metalworking methods given above are associated with a high manufacturing outlay and correspondingly high production costs. Sometimes certain types of metalworking are necessary for the production of certain products and can not be replaced by other processing methods, or only with great effort.

Presentation of the invention

The object of the invention is to provide a product belonging to the technical field mentioned above, which can be produced in relation to its size with little material and has a correspondingly low weight.

The solution of the problem is defined by the features of claim 1. According to the invention, the metal product comprises a basic structure having a plurality of scaffolding sections connected to one another. Furthermore, it comprises a filling structure with a plurality of grid sections connected to one another to form a grid structure. In this case, the basic structure defines a spatial basic shape of the product, and the filling structure at least partially fills a spatial area defined by the framework. In principle, it would be conceivable to produce such products, for example, by connecting the individual framework sections or grid sections by means of soldering or welding, but this is extremely complicated and may therefore not be possible at all, for example if the product has sub-millimeter structures. Apart from casting, most other processing methods are not suitable for this. The product is therefore produced according to the invention by means of a casting process.

By a product is not made of solid metal, but with the inventive basic structure of a plurality of interconnected with a scaffold framework sections, the appearance of the product can be defined with little effort and produced with correspondingly little material. Nevertheless, the framework-like structure of the basic structure gives the product a three-dimensional basic stability and a clearly defined external appearance, which can already be recognized from a distance. The filling structure according to the invention with the grid sections connected to a grid structure in turn not only increases the rigidity, but also the load capacity and durability of the product, and this with very low material consumption and correspondingly low weight of the product. This is especially true when the grid sections form triangles, which is preferably the case. In this way, the stability of the product can be further increased despite limited material costs. By filling the basic structure of the product with the filling structure, the three-dimensional appearance of the product is further underlined without having to continuously fill the outer or inner boundary surfaces or the spatial area of the product defined and demarcated by the framework.

In this way, the weight and the required amount of material and thus the production costs compared to a correspondingly massive object of comparable size can be reduced to a fraction each.

In addition, it is possible with a casting process to realize extremely complex structures of the product, which would not be possible with other processing methods.

This is especially true for lost model casting and lost die casting methods in which a plaster mold is made using a previously made model, thereby destroying the model. Thereafter, the liquid metal is poured directly into the plaster mold and when removing the cooled product in the mold this is destroyed. As a result, for example, products can be cast which have undercuts and complex, three-dimensional structures with holes, etc. The product is therefore preferably produced by means of a direct casting process with lost model and lost shape.

The framework sections and the grid sections are preferably elongated, d. H. Their longitudinal extent is a multiple of their transverse extent and they have along their longitudinal extent in each case a constant cross-section. The sections are, for example, rod-shaped, wherein they can not only be straight but can also have curvatures. For example, it may be elliptical or circular arc sections. A product is advantageously designed such that a cross-sectional area of the framework sections is greater than a cross-sectional area of the grid sections. As a result, the basic structure of the product becomes more stable and can be emphasized a little more, the overall stability of the product is hardly affected by the somewhat filigree design of the filling structure.

While the invention may in principle be products of any size, it is preferably comparatively small objects with a size in the range of a few millimeters to a few centimeters, in particular with a size of less than eight centimeters. In this case, the size of an object is considered to be the largest extent of the object in one of the three spatial directions. Are correspondingly fine in such Products, including scaffolding and lattice sections. The framework sections therefore have a cross-sectional area of at most 0.7 mm ² , preferably between 0.3 mm ² and 0.7 mm ^2, and the grid sections have a cross-sectional area greater than 0.25 mm ² , preferably between 0.25 mm ² and 0.5 mm ² . In addition, the shape of the cross-sectional areas of the framework and grid sections is basically irrelevant, but they are preferably circular or circular disk-shaped, since such forms can be better planned and implemented.

A product according to the invention can be produced from the most arbitrary metals such as iron, copper, aluminum, lead, etc. However, in a preferred embodiment of the invention, the product is made of a noble metal such as silver, gold or platinum. Due to the comparatively high material costs of precious metals, the lower material requirement in the final price of the product is most noticeable.

Corresponding alloys which are suitable for casting such an article must have a comparatively high and long flowability so that such fine structures can also be poured off cleanly and without errors. The alloys must be such that no cracks or solidification voids occur during the casting on cooling.

Although it is possible that the product consists of several individual parts, which in turn have been produced by means of a casting process as described above. In a preferred embodiment of the invention, however, the product is poured in one piece. As a result, additional production steps such as the assembly of the items can be avoided and the manufacturing cost can be kept low.

The configuration of the filling structure can be used to determine how much of the spatial area defined by the framework is to be filled in, ie how large the ratio of the volume of the grid sections to the volume of this spatial area should be. This ratio is hereinafter also referred to as degree of filling. For example, if the grid sections are placed close to each other so that the grid is made up of many, is closely spaced grid sections, the above ratio is greater than when the grid sections are far apart and correspondingly fewer grid sections are present in the spatial area.

However, since the weight and the material requirement increases with this ratio, but the stability of the product decreases with this ratio, it is necessary, depending on the desired properties to find a suitably coordinated value for the degree of filling.

In order to keep the material requirement low with sufficient physical stability, the degree of filling in a preferred embodiment of the product according to the invention is at most about 15%, ie. H. the filling structure fills the spatial area defined by the framework to a maximum of 15%. Particularly preferred is a degree of filling between about 1% and 9%.

For the casting of an object, a sprue (also referred to as a main sprue) is typically provided on the model to be molded, through which the liquid metal passes during the casting process into the plaster mold and is distributed in the plaster mold. This channel typically has a relatively large cross section compared to the cross sections of the product itself, so that the metal can reach all areas of the plaster mold without excessive cooling and the plaster mold can be poured off with optimum results. This runner, which is typically connected to the product after cooling and forming of the product, is typically separated. Normally, the corresponding joints are reworked so that it is no longer possible to see from the end product where the sprue was originally connected to the product.

In a preferred embodiment of the invention, however, the pouring channel is not removed after casting, but forms a peripheral frame structure in addition to the filling structure and the basic structure. The cross-sectional area of this frame structure is significantly greater than the cross-sectional areas of the framework and grid sections, and is preferably over 1 mm ² .

This frame structure can be left as it is, or it can be provided with other elements. For example, it may be designed to carry one or more gems.

1. a) mittels eines Stereolithographie-Verfahrens wird aus einem lichtaushärtendem Kunststoff, insbesondere aus einem Kunstharz wie z. B. Epoxydharz, ein Modell des Erzeugnisses angefertigt (sogenanntes "Rapid Prototyping"),
2. b) aus dem Modell wird eine Gipsform des Erzeugnisses angefertigt,
3. c) mittels eines Gussverfahrens, insbesondere eines Direktgussverfahrens, wird die Gipsform abgegossen,
4. d) eine räumliche Grundform des Erzeugnisses wird durch eine Grundstruktur definiert, welche eine Mehrzahl von miteinander zu einem Gerüst verbundene Gerüstabschnitte umfasst,
5. e) und ein von dem Gerüst definierter räumlicher Bereich des Erzeugnisses wird zumindest teilweise mit einer Füllstruktur ausgefüllt, welche eine Mehrzahl von miteinander zu einer Gitterstruktur verbundene Gitterabschnitte umfasst.

The inventive method for producing a metal product is defined by the features of claim 10. It includes the following steps

1. a) by means of a stereolithography process is made of a lichtaushärtendem plastic, in particular of a synthetic resin such. B. epoxy resin, a model of the product made (so-called "rapid prototyping"),
2. b) a plaster mold of the product is made from the model,
3. c) by means of a casting process, in particular a direct casting process, the plaster mold is poured off,
4. d) a basic spatial form of the product is defined by a basic structure which comprises a plurality of framework sections connected to one another in a framework,
5. e) and a spatial region of the product defined by the framework is at least partially filled with a filling structure which comprises a plurality of grid sections connected to one another to form a grid structure.

However, before the model can be made, the product must first be designed. This is typically done with a CAD (computer aided design) program. Thereafter, the correspondingly generated data is converted into a specific format, for example the STL format, which can be read and processed by a stereolithography machine. Based on these data, the model is then made using a stereolithography process of a light-curing plastic.

Studies have shown that wax-based stereolithography machines are not suitable for making models in which the framework sections have cross-sectional areas between 0.25 mm ² and 0.7 mm ² . The usable light-curing plastics are known from the prior art and are not described in detail here. However, care must be taken that the resin used is as good as possible to incinerate, ideally to 100%, with it after the plaster mold has burnt out, there are as little or no residues of the plastic as possible.

Further, it has been found that such models can not be made with any commercially available on the market stereolithography resin-based machine. For example, the Viper si2 SLA® stereolithography machine from 3D Systems, which is consequently also used to manufacture the models, was found to be good.

In a preferred embodiment of the invention, the plaster mold is made from the model as follows: the model is attached to a wax tree, this being done manually in particular, because this requires a lot of experience and skill. Next, the model including wax tree is embedded in plaster, dried the plaster mold, the wax tree in a steam bath and then burned out the plaster mold. The wax of the wax tree runs in the steam bath completely from the plaster mold and when burning out the plaster mold, which takes place in a rotary kiln for a period of about 16 hours, the resin is almost completely burned. Last remains, which may remain in the plaster mold, must be carefully removed, for example, with a suitably equipped suction, so that the plaster mold can be completely filled with the liquid metal and the product has no or as little flaws.

The plaster used for making the mold is known from the prior art and will not be explained in detail here. However, a fine-grained plaster should be used, so that even the finest structures are displayed correctly. Thus, the narrow cross-sections and very fine contours leak clean, ie optimally flows through the liquid metal and filled with it, the plaster mold is preferably poured at a temperature between 700 ° C and 750 ° C. The plaster mold is typically not heated specifically for this, but the casting takes place with advantage directly after burning out of the plaster mold in the still hot from burning shape, as soon as it has reached the correct temperature.

While, as previously mentioned, the sprue is typically removed after cooling of the cast-off plaster mold, in a preferred variant of the invention it is left on the product. This frame structure gives the product even more stability and can at the same time serve to decorate the product. This effect can be further enhanced by providing this frame structure optionally with one or more gemstones.

Finally, the product can still be subjected to a surface treatment. For example, the products are still being polished.

From the following detailed description and the totality of the claims, further advantageous embodiments and feature combinations of the invention result.

Brief description of the drawings

Fig. 1

zeigt ein erfindungsgemässes Erzeugnis aus sechs würfelförmigen Untereinheiten;

Fig. 2

zeigt eine der würfelförmigen Untereinheiten aus welchen das Erzeugnis auf Fig. 1 aufgebaut ist;

Fig. 3

zeigt ein weiteres Ausführungsbeispiel eines erfindungsgemässen Erzeugnisses in Form eines Würfels;

Fig. 4

zeigt ein weiteres Ausführungsbeispiel eines erfindungsgemässen Erzeugnisses in Form eines Herzens;

Fig. 5

zeigt ein weiteres Ausführungsbeispiel eines erfindungsgemässen Erzeugnisses in Form eines Dreiecks und

Fig. 6

zeigt ein weiteres Ausführungsbeispiel eines erfindungsgemässen Erzeugnisses in Form eines weiteren, dreidimensionalen Dreiecks, bei welchem der Eingusskanal als Teil des Erzeugnisses ausgebildet ist.

The drawings used to explain the embodiment show:

Fig. 1

shows an inventive product of six cube-shaped subunits;

Fig. 2

shows one of the cube-shaped subunits from which the product is constructed on Fig. 1;

Fig. 3

shows a further embodiment of an inventive product in the form of a cube;

Fig. 4

shows a further embodiment of an inventive product in the form of a heart;

Fig. 5

shows a further embodiment of an inventive product in the form of a triangle and

Fig. 6

shows a further embodiment of an inventive product in the form of another, three-dimensional triangle, in which the sprue is formed as part of the product.

Basically, the same parts are provided with the same reference numerals in the figures.

Ways to carry out the invention

In Fig. 1, an inventive product, in this case, a cross 1 is shown. This is composed of six cube-shaped subunits 2. Such a cube-shaped subunit is shown in Fig. 2 in an enlarged illustration. Four of the subunits 2 are arranged in series and the other two are arranged on opposite sides of one of the two middle subunits 2, so that overall the cross 1 results. The subunits 2 are in this case lined up in such a way that two adjacent subunits 2 each have a common side surface.

The edges 3 of such a cube-shaped subunit 2 form the structures previously referred to as scaffolding sections. These have a circular disk-shaped cross-section with a cross-sectional area between 0.3 mm ² and 0.7 mm ² . The room diagonals 4 of the cube with the edges 3 are the previously referred to as grid sections structure and also have a circular disk-shaped cross-section. However, the cross-sectional area is smaller here, namely between 0.25 mm ² and 0.5 mm ² .

Ie. All edges 3 of each subunit 2 form the basic structure or the framework of and the spatial diagonals 4 in turn form the filling structure or the lattice structure of the cross 1.

For an example of a white gold alloy suitable for casting a product according to the invention, reference is made to the alloy AU 750/3157 Pd directed the company Metalor. This alloy comprises as main constituents 75% gold, 7% palladium and 10% silver. Also suitable as the yellow gold alloy AU 750/152 S Metalor with the main components 75% gold, 12.5% silver and 12.5% copper proved. The percentages for these alloys are each weight percentages. Again, it will be apparent to one skilled in the art that these percentages are not to be construed as immutable, but may be varied according to the particular requirements of the particular application, ie, the specific design of the product to be molded.

FIG. 3 shows a further exemplary embodiment of a product according to the invention, which has the shape of a cube 10. The cube 10 comprises six side surfaces 11 each with rounded corners 12. The edges of the side surfaces 11 and the arcuate corner portions 16 of the edges form the backbone, i. H. the framework sections 13 of the cube 10, which define the outer shape of the product, here just the cubic shape of the cube 10. The interior of the cube 10 and the side surfaces 11 are filled by the grid sections 14. The grid sections 14 in this example form a regular, cubic grid and give the cube 10 a correspondingly stable structure.

A peculiarity in this embodiment is that each of the side surfaces 11 comprises at least one socket 15, which is designed to receive a gemstone, such as a diamond. The number and arrangement of the sockets 15 on the side surfaces 11 in this case corresponds to the number and arrangement of the eyes of a normal cube. The individual sockets are in this case preferably in an intersection of the grid sections 14 in the side surfaces 11.

In other embodiments, no such sockets or one or more such sockets may be provided at all in either one of the outer and inner surfaces of the product.

To determine the degree of filling, the volume of the cube 10 must first be determined. With a side length of the cube 10 of about 20 mm in length, the cube 10 encloses a volume of about 8000 mm ³ . Furthermore, the volume of the grid sections 14 must be determined. In the example shown, these have a cross-sectional area of 0.5 mm ² on. From a side surface 11 of the cube 10 each lead nine grid sections 14 (ie without the grid sections 14, which lie in the side surfaces 11 itself) to the respective opposite side surface 11. In three pairs of opposing side surfaces 11 results in 27 grid sections 14 a about 20 mm times 0.5 mm ² . This results in a total volume of the grid sections 14 within the cube 10 of approximately 270 mm ³ . The degree of filling F is calculated therefrom by dividing the volume of the grid sections 14 by the volume of the cube 10: $$\mathrm{F}=270/8000{\mathrm{<figure-callout\; id="3"\; label="mm"\; filenames="imgf0001.png"\; state="\{\{state\}\}">mm</figure-callout>}}^3=\mathrm{3.4.}$$

Ie. only about 3.4% of the volume of the cube 10 is actually filled with material. The inaccuracies resulting, for example, from the fact that the corners of the cube are rounded or that the intersections of the lattice sections 14 have each been considered in triplicate, were neglected in this calculation.

4 shows a further exemplary embodiment of a product according to the invention, here in the form of a heart 20. The heart 20 comprises an upper, non-planar, heart-shaped framework section 23.1 and a lower, non-planar, heart-shaped framework section 23.2, which adjoin the heart peaks 21 as well as in the large bow areas 22 touch. These arc regions 22 may, for example, also have sections which belong to both the upper and the lower frame section 23.1 and 23.2. The two heart-shaped frame sections 23.1, 23.2 are designed such that they each define a heart-shaped, curved surface. These surfaces are filled by the (in this case heart-shaped) grid sections 24.1. The individual heart-shaped grid sections 24.1 touch each other, so that a relatively high stability can be achieved. One of these heart-shaped grid sections 24.1 is also completely filled and occupied by three gems 25. For further stabilization, the grid structure of the heart 20 also includes straight grid sections 24.2, which fill the space spanned by the two curved surfaces.

Fig. 5 shows a further embodiment of a product according to the invention. This has the shape of a triangle 30. It again comprises an upper, triangular frame section 33.1 and a lower, triangular frame section 33.2, which define the triangular shape as such. The filling structure in this example comprises a plurality of circular grid sections 34.1 connecting the lower to the upper device sections 33.1 and 33.2, a plurality of bar-shaped grid sections 34.2 which also serve as a connection between the two stand sections 33.1 and 33.2 and a plurality of bar-shaped ones Grid sections 34.3, which each fill the triangular areas defined by scaffolding sections 33.1, 33.2. The triangle 30 has on one of its side surfaces further on a bracket 35, with which the triangle is fastened, for example, to a necklace.

Fig. 6 shows another, also triangular example of a product according to the invention. The outer shape of this product is also a triangle 40. The core of the triangle 40 in this case is formed from a triangular, upper framework section 43.1, a triangular, central framework section 43.2 and a triangular, lower framework section 43.3, which lie in parallel planes in each case. The upper and the lower framework section 43.1, 43.3 have the same shape and size, are the same orientation in space and the middle frame section 43.2 is slightly larger than the other two, but is also the same orientation and is located centrally between them. The grid structure of the triangle 40 comprises a plurality of rod-shaped grid sections 44. These fill both the outer surfaces of the core of the triangle 40 formed by the three frame sections 43.1, 43.2, 43.3 and the interior of the core bounded by these outer surfaces.

As a special feature, the triangle comprises a frame 45, which is connected by means of pyramid-shaped connecting pieces 46 at several points with the central frame section 43.2. The frame 45 has not been attached thereto after the manufacture of the core, but has been made simultaneously with the core and integral therewith. The frame 45 is the sprue, which serves for the coarse distribution of the liquid metal within the mold during casting and has a correspondingly larger cross section than the framework sections 43.1, 43.2, 43.3 and the grid sections 44. The connecting pieces 46 in turn are the so-called supply channels, through which when pouring the liquid metal from the sprue into the different sections of the core is passed. Both the The sprue and the supply channels are typically completely removed after cooling of the molded article, whereas this is not necessary in the invention. Depending on the application, the supply channels and the sprue are left as part of the product.

In addition, the frame 45 has a plurality of sockets 48, which are each occupied by a gemstone 49.

Also on the triangle 40, a bracket 47 is provided which serves to secure the triangle 40 to another object.

In all the examples described above, the cross-sectional areas of the framework and grid sections can be freely selected within the limits set forth above and optimized for the particular application of the products, so that both the physical stability of the products in the desired range and the external appearance of the products meets the respective requirements.

Depending on the specific design of the framework or the grid structure, the stability of the products can be further influenced. If, for example, a high degree of stability is to be achieved with respect to compressive or tensile forces occurring perpendicularly to the main side surfaces, a cubic lattice structure appears advantageous. On the other hand, with compressive or tensile forces which do not attack perpendicularly to any of the major side surfaces of a product, a triangular-based lattice structure appears to be more suitable.

In summary, it should be noted that the invention allows the production of products made of metal, which compared to similar products of comparable size have a low weight and in which for their production comparatively little material is needed. Accordingly, the products have a low weight and are inexpensive to manufacture. However, despite their low material consumption, the products have relatively high physical stability and strength.

The products produced in this way, as mentioned above, can fulfill a wide variety of functions. You can z. B. as shown in Fig. 3 may be formed as a stand or base, or they may also as shown in Figures 4, 5 and 6, as Decor objects may be formed, which are suitable for example as a necklace pendant, brooches, statues, finger rings, other jewelry or just to set up. Many other designs such as racks, key chains, letter-makers, candle holders, fittings, tools, models of buildings, etc., but also z. B. Toys such as chess pieces, dominoes, toy models of automobiles, etc. are possible.

Claims (12)

A product (1) made of metal, the product being produced by means of a casting process, characterized in that the product has a basic structure with a plurality of framework sections (3) connected to one another and a filling structure with a plurality of grid sections connected to one another to form a lattice structure (4), wherein the basic structure defines a basic spatial form of the product and the filling structure at least partially fills a spatial area defined by the framework. Product according to claim 1, wherein it is produced by means of a lost-cast and lost-mold direct casting process. Product according to one of claims 1-2, wherein the framework sections (3) and the grid sections (4) are elongated and each have a constant cross-section along their longitudinal extent, wherein a cross-sectional area of the framework sections (3) is greater than a cross-sectional area of the grid sections ( 4). Product according to one of claims 1-3, wherein a size of the product is in the range of a few millimeters to a few centimeters, the framework sections (3) have a cross-sectional area of at most 0.7 mm ² , preferably between 0.3 mm ² - 0.7 mm ² , and the grid sections (4) have a cross-sectional area over 0.25 mm ² , preferably between 0.25 mm ² - 0.5 mm ² , and the cross-sectional areas of the frame sections (3) and the grid sections (4) are in particular circular disk-shaped. A product according to any one of claims 1-4, wherein it is made of precious metal. Product according to one of claims 1-5, wherein it is poured in one piece. Product according to one of claims 1-6, wherein the filling structure fills the spatial region defined by the framework to a maximum of 15%, preferably between 1% and 9%. A product according to any one of claims 1-7, wherein the product comprises, in addition to the filling structure and the basic structure, a peripheral frame structure (45) which has been used as a pouring channel during the pouring of the product and in particular has a cross-sectional area greater than 1 mm ² . A product according to claim 8, wherein the peripheral frame structure (45) carries at least one gemstone (49). Process for producing a metal product (1), in particular a product (1) according to one of claims 1 to 9, comprising the following steps: a) by means of a stereolithography process is made of a light-curing plastic, in particular a synthetic resin such. Epoxy resin, a model of the product made, b) a plaster mold of the product is made from the model, c) by means of a casting process, in particular a direct casting process, the plaster mold is poured off, characterized in that d) a basic spatial form of the product (1) is defined by a basic structure which comprises a plurality of framework sections (3) connected to one another to form a framework, e) and a surface spanned by the framework and / or a spatial region of the product defined by the framework is at least partially filled with a filling structure which comprises a plurality of grid sections (4) connected to one another to form a grid structure. The method of claim 10, wherein the plaster mold is made by attaching the model to a wax tree, the model including wax tree embedded in plaster, dried the plaster mold, the wax tree is melted in a steam bath and the plaster mold is then burned out. A method according to any one of claims 10-11, wherein a runner (45) is left on the product (1) and optionally provided with at least one gemstone (49).

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