DE102017202681A1 - Tool for the production of cast models - Google Patents

Abstract

Tool for the production of cast models, in particular of Lost-Foam Schäumlingen, wherein the tool is at least partially formed from sand.

Description

The present invention relates to a tool for the production of cast models as well as a use of an additive manufacturing method.

The casting models in question are, for example, positive models, as used in Lost Foam casting. Here, a (positive) model (foaming), for example, molded foamed polystyrene, embedded in a molding material, usually made of quartz sand, and the resulting "cavity" is poured with liquid metal. The model is thermally decomposed by the molten metal. When casting is thus for each casting to provide a corresponding positive model that does not exist after the casting process (lost model). Such models or foams, which are often composed of several parts, sometimes have extremely complex geometries. For the production of the models or the model segments, for example, in the production of cylinder heads, shell tools made of aluminum are used. These are extremely expensive to manufacture, since they not only have to map the complicated geometry of the model, but z. B. also allow the injection of the aforementioned polystyrene to produce the positive model. This has the disadvantage that an adaptation of a geometry of the tools is extremely complicated and expensive or possibly not possible at all meaningful.

Object of the present invention is therefore to provide a tool for the production of cast models and a use, which are significantly cheaper and more flexible at the same time.

This object is achieved by a tool according to claim 1 and by a use according to claim 8. Further advantages and features will become apparent from the dependent claims and the description and the accompanying figure.

According to the invention, a tool for producing cast models, in particular Lost Foam foams, at least partially formed or formed from sand. The tool is according to a preferred embodiment, in particular a shell tool, as it is used for the production of positive models or foams in the field of lost foam casting. With such a shell tool, for example, a model segment is formed. The final model is composed of several such model segments, sized, etc. The various process steps of the lost foam casting process are known in the art and are therefore not repeated here. The known tools are made of aluminum and therefore not or only to a small extent adaptable to any changes in geometry, for example, if the casting model is to be changed. Advantageously, the tool is here at least partially formed or formed of sand, whereby the cost can be significantly reduced and whereby a significantly higher flexibility is given. In this case, the area formed from the sand is, in particular, an inner contour of the tool which forms the (positive) model, at least in sections or sections. The background is that this area formed from the sand is cost-effective and quick as well as easily changeable and adaptable both in its manufacture. It is particularly advantageous here that the region formed from the sand only serves to produce casting models, for example from (expanded) polystyrene (EPS) and is not designed or has to be designed for contact with liquid metal. The non-sand molded portion of the tool is made of aluminum, for example, according to one embodiment. Alternatively, the tool is also completely formed or formed of sand. Preferably, the tool comprises one or more support frames, for example made of aluminum, in or into which the at least partially sand-molded tool is inserted or used, and which are designed, the tool z. B. to give additional stability.

According to a preferred embodiment, the area formed from the sand is produced by means of an additive manufacturing process. This allows for a very fast production and on the other hand, the realization of extremely complex geometries, which may also have undercuts, etc. Conveniently, for example, a 3D printer, such as e.g. is known for printing cast cores made of sand, used for at least partially producing the tool. In this context, it should be mentioned that the sand is a corresponding molding sand or a sand that is suitable for additive manufacturing. In this case, the method basically proceeds in such a way that, for example, a sand contacted with an activator and particles associated therewith are contacted with a binder. By at least partially curing the binder, a layered structure of a three-dimensional shape can be realized. The particles are, for example, particles of ceramic, metal, plastic, carbohydrate, etc.

Alternatively, the tool can be made completely or partially in hot-box or cold-box method from sand, for example by means of a core shooter. Both methods are known in principle to the person skilled in the art and will not be explained further here. This approach may allow even faster and cheaper production, However, if necessary, only at higher quantities. The geometric freedoms are significantly lower than z. B. in additive manufacturing. In particular, if only a smaller or less complex region of the tool is to be formed from sand, as for example in the "insert" explained in more detail below, this approach can be advantageous.

Conveniently, the tool has an inner contour, wherein the inner contour is at least partially formed from the sand. As already mentioned, the inner contour is that region of the tool which, at least in regions, forms the casting model or the model segment.

According to a preferred embodiment, the tool comprises an upper shell and a lower shell, wherein at least one of the shells is completely formed from the sand. Such a tool is designed or designed in particular for producing a model segment. Optionally, both mold halves can be completely formed from the sand. Background is basically that, for example, inner contour sections, which should certainly not be changed, for example, are formed as a permanent form, while areas that are expected to require an adjustment, are made of the sand, in particular by means of the additive manufacturing process. The design as a shell tool has the background that the positive models are usually assembled from model segments, wherein the model segments segmentally or layer by layer join the later model. In other words, a large number of model segments yields the later model. The individual model segments or foams are produced in the aforementioned shell tools. Starting material for the production of the models is aluminum casting, for example, an expandable polystyrene raw material (EPS) added with a blowing agent (pentane). The basic procedure and the further process steps are known to the person skilled in the art and are therefore not repeated here. The shell tools, completely or at least partially formed from sand, are preferably arranged for better action in (aluminum) support frame.

Alternatively, it is precisely the use or the use of an additive manufacturing method that makes it possible to completely generate the entire model, so that the generation of individual model segments may possibly even be dispensed with.

Possible additive manufacturing processes are z. Laser-sintering (LS), fused-layer modeling (FLM, identical to FDM), Multi-Jet Modeling (MJM), Poly-Jet Modeling (PJM), Layer Laminated Manufacturing (LLM), Digital Light Processing (DLP) and Thermal transfer sintering (TTS).

According to one embodiment, the tool comprises an insert, wherein the insert is formed from the sand or at least partially formed from the sand. Expediently, the insert is designed and / or embodied such that it predominantly forms only an inner contour of the tool and has no holes or feed channels for the model material, as a result of which the complexity can be significantly reduced. The insert is advantageously designed such that it can be inserted into the tool and fixed in this.

Conveniently, the insert is formed or arranged changeable. This is based on the idea, if necessary, to shape only those areas of the tool made of sand, which are expected to be subject to change. This can advantageously further reduce the price of the tool.

Conveniently, the tool is completely or partially formed as a disposable tool. Conveniently, the tool, in particular the shell tool comprising the upper shell and the lower shell, made entirely from the sand, in particular by means of an additive manufacturing process, wherein the tool can be used at least once for spraying a model or model segment. Conveniently, subsequently, the "spent" tool may be fed to a recovery process so that the components may be used to create a new tool.

Advantageously, the tool allows the cost of change, especially in the early stages of the project, to be significantly reduced. The testing of the components is thus facilitated. When using additive manufacturing processes, in particular the high degree of design freedom is advantageous. A realization of undercuts is thus possible for example at any time. In addition, cost savings can be noted over the reduced time required in the manufacture of tools made of sand, for example by means of an additive manufacturing process or in hot-box or cold box process, compared to the conventional production of tools made of aluminum. For example, the tools have a multiplicity of small and smallest holes or feed channels, over which the model material, in particular the expandable material which forms the later model, is injected. These are eroded in tools made of metal, such as aluminum, time-consuming. In particular, in the production of prototypes and experimental parts, for example in the field of cylinder head production of z. B. 3-, 4-, 6- and 8-cylinder engines, the at least partially formed from sand tools can therefore be used efficiently. It is understood that the use of the tools is not limited to the aforementioned examples. The same applies with regard to the casting method used. For example, Lost Foam casting has been used, but the tools can also be used for other casting processes based on the use of lost models.

Due to the reduced modification work, the life of the series tools can be advantageously extended. In addition, the investment costs of the tools are reduced. The investment costs are reduced by imaging very early assemblies in small numbers in sand rather than conventionally in aluminum shell tools. The procurement process of aluminum shell tools can start later. The same applies to geometric changes that currently need to be tested in series tools and often can not remain in the series production.

Furthermore, the invention relates to a use of an additive manufacturing method for at least partially producing a cast model tool made of sand.

For use, the features mentioned in connection with the tool apply analogously and accordingly and vice versa.

Further advantages and features will become apparent from the following description of an embodiment of a tool with reference to the accompanying figure.

• 1: eine schematische Ansicht eines Werkzeugs in einer Schnittdarstellung nebst Gussmodell.

It shows:

• 1 : A schematic view of a tool in a sectional view along with cast model.

1 shows a schematic representation of a tool 20 , in particular a shell mold, comprising an upper shell 24 and a lower shell 26 , The tool forms a mold cavity 28 or forms an inner contour 22 , wherein the inner contour 22 an outer shape of one through the tool 20 producible cast model 40 or a model segment 42 represents, as shown schematically in the lower half of the picture. With the reference number 30 is a schematic use 30 represented, which z. B. from a sand, in whole or in part, is shaped. Depending on the embodiment, the upper shell 24 and the lower shell 26 made entirely of sand, in particular by means of an additive manufacturing process. Alternatively, the upper shell 24 or the lower shell 26 only in the region of the inner contour or only in sections in the region of the inner contour 22 made of sand, in particular by means of an additive manufacturing process. The remaining areas of the tool 20 can be made of aluminum, for example. Next alternative is also only, as already mentioned, the use 30 shaped from the sand. Background is basically the provision of a low-cost and flexible tool, in particular shell mold, for the production of cast models or model segments, as z. B. be used in the field of Lost Foam casting.

LIST OF REFERENCE NUMBERS

20

Tool

22

inner contour

24

Upper shell

26

subshell

28

mold cavity

30

commitment

40

Cast model, (positive) model, foamy

42

Model segment, foamy

Claims (8)

Tool (20) for producing cast models (40), in particular Lost Foam foams (42), wherein the tool (20) is at least partially formed from sand. Tool (20) after Claim 1 wherein the portion formed from the sand is made by an additive manufacturing method. Tool (20) after Claim 1 or 2 wherein the tool (20) has an inner contour (22), and wherein the inner contour (22) is at least partially formed from the sand. A tool (20) according to any one of the preceding claims, comprising an upper shell (24) and a lower shell (26), and wherein at least one of the shells (24; 26) is formed entirely of the sand. A tool (20) according to any one of the preceding claims, comprising an insert (30), and wherein the insert (30) is formed from the sand. Tool (20) after Claim 5 wherein the insert (30) is changeable or arranged. Tool (20), wherein the tool (20) is formed wholly or partially as a disposable tool. Use of an additive manufacturing method for at least partial production of a cast model tool (20) made of sand.

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