EP3616806B1 - Method for producing a model form core blank, a model form core and an investment casting molds and a casting method for producing a cast piece with a hollow structure - Google Patents

Description

The invention relates to a method for producing a model mold core blank according to claim 1, a method for producing an investment casting mold according to claim 2 and a casting method for producing a cast part with a cavity structure according to claim 14.

Casting methods for producing components are known from the prior art. In these, a casting mold is filled with a material and removed after it has solidified or solidified. Particular challenges arise in the formation of undercuts on and cavity structures in the component.

Components that are complex in terms of casting technology are therefore manufactured using what is known as investment casting, in which lost models and lost molds are used to create the component to manufacture. After the investment casting process has been completed, both the model of the component and the casting mold are destroyed.

The model can be made from wax, for example, and used to create a casting mold from a ceramic. The casting mold is designed in particular as a lost mold in the form of a single-use ceramic coating of the model. After the wax has been removed from the casting mold, a cavity remains that can be filled with the material of the component to be manufactured. After filling and hardening, the mold is destroyed and the component removed.

In order to be able to form cavity structures in the component, cores are used around which the wax model is manufactured. After the wax has been removed from the ceramic coating, these cores remain in the cavity of the ceramic coating and then correspondingly also form a cavity in the component. The core is later removed from the component using mechanical or chemical processes.

Particularly for the manufacture of turbine blades, in WO 2015/051916 A1 a method is described in which a core is first produced according to a 3D model in a first CNC method. The core is then positioned in a processing holder in order to subsequently be coated with a wax body blank. It is, so to speak, a process for the production of a model core blank.

The wax body blank is then processed in a second CNC process in such a way that a lost wax model of the component is created around the core. Up to this point, the process can be described as a process for producing a model mold core. The model mold core produced in this way therefore has a lost core and the lost model.

The disadvantage of the method for producing the model mold core blank and the model mold core is that the position of the core relative to the lost model cannot be achieved reliably with sufficient precision. This creates scrap. The later the defective positioning of the core, which can hardly be ascertained from the outside, is recognized in the lost model, the higher the costs of the rejects. In the various production stages, therefore, considerable effort has to be made in order to prevent incorrect positioning of the cavity structures in the final component.

The in the proceedings of WO 2015/051916 A1 Further steps can no longer compensate for the incorrect positioning of the core that occurred up to the production of the model mold core. According to the method, a ceramic mold is applied to the lost model immediately afterwards. So that the ceramic mold is still positioned relative to the core even after the lost model has been removed, the ceramic mold is previously connected to the processing holder on which the core was also positioned and fixed. The method leading up to this point is therefore a method for producing an investment casting mold.

The disadvantage of this investment casting mold is that an expensive processing holder is required that can withstand later firing processes and metal casting. In addition, there may be an incorrect positioning of the lost core in the ceramic mold, which makes either the investment casting mold as such or the component cast later unusable.

Regarding the procedure according to WO 2015/051916 A1 Finally, it includes filling the ceramic mold with the inner core with molten metal, while the lost core and the ceramic shell are still connected to the processing holder. After the metal has solidified into a solid component, the ceramic form and the core are removed.

The disadvantage of this work step is that the processing holder is exposed to the casting temperatures of the metal. The processing holder can be deformed here, so that the relative positioning between the ceramic mold and the core changes. In addition, the processing holder must be made of high-temperature-resistant materials, which makes it expensive and means increased effort when accommodating it in processing machines.

One method of providing a mold for turbine blades is disclosed in FIG EP 3 251 790 A2 famous. In this case, a model core is first made by first gluing sleeves into parallel holes on one side of a ceramic block. With these sleeves, the ceramic block is then placed on an annular holder that engages with a pin in one of the sleeves. According to one embodiment, the ceramic block can be removed from the ring-shaped holder at any time, or it can be placed in a machine tool with it. Alternatively, it is also disclosed that the ceramic block is glued to the ring-shaped holder. After machining the ceramic block to A model core is encapsulated with wax and then the wax is machined.

The object of the invention is therefore to develop process steps that contribute to reliable, reproducible and, above all, precise positioning of a lost core relative to a ceramic form of an investment casting mold, the process steps being as little complex as possible and quick and inexpensive to perform. In particular, this should also prevent rejects from the core production to the finished component.

Main features of the invention are specified in claim 1 and claims 2 and 14. Refinements are the subject of claims 3 to 13 and 15 and the description.

The invention relates to a method for producing a model mold core blank, which is particularly suitable for producing a cast part with a cavity structure, using a 3D model (three-dimensional model) of digital geometry coordinates of the cast part. In this method, a ceramic blank is positioned on a processing holder and a fixation is established between the ceramic blank and the processing holder. The cubature of the ceramic blank is preferably larger than a core element to be produced from it. A core element is then manufactured, a lost core being manufactured from the ceramic blank based on the 3D model in a first CNC manufacturing process while the fixation continues, the machining holder being fixed in a CNC machine for performing the first CNC manufacturing process . The lost core is preferably a cavity model of the cavity structure.

The method is supplemented by the fact that a stabilization frame is produced from the ceramic blank during the first CNC production process and while the fixation continues, the stabilization frame supporting the lost core, in particular at at least one support point which is arranged at a distance from the machining holder. By means of such stabilization frames, very fine lost cores can be made available, which are neither deformed nor damaged during their own production or during subsequent production steps. The stabilizing frame can lie at least partially outside of the model blank. In this area, it will not interfere with further processing of the model blank.

According to the method, a removal of one or more support points between the stabilizing frame and the lost core is provided after the production of the lost core and before the production of the model blank, this preferably in the first CNC production process. The lost core is thus kept stable during machining in the first CNC manufacturing process and particularly fine contours can be formed on the lost core. The support points are preferably connecting webs which are preferably narrower and / or thinner than the adjoining area of the lost core.

Thereafter, the method provides for making a model blank by casting model material around the lost core and allowing the model material to solidify while the fixation continues. The cubature of the model blank is preferably larger than a lost model to be produced from it, the lost model preferably being a positive model of the cast part if the outer contour of the lost model is produced by a material-removing process such as turning, milling, laser cutting, etc. Conversely, the cubature of the model blank is preferably smaller than a lost model to be produced from it, the lost model preferably being a positive model of the casting if the outer contour of the lost model is produced on the model blank by a material application process such as 3D printing.

Optionally, the stabilizing frame is removed after the production of the lost core and before the production of the model blank, preferably after the removal of one or more support points, and furthermore preferably in the first CNC production process. This is particularly suitable for lost cores that have sufficient inherent stability.

In another variant, the stabilizing frame is not removed before the model blank is produced. The stabilizing frame can then also support the lost core during the production of the model blank and optionally also during the production of the lost model. The stabilizing frame can be arranged at least partially in the model blank. However, it should be outside the lost model. Support points of the stabilization frame can then extend through the lost model to the lost core. This also stabilizes lost cores of unstable design during the further process steps, prevents changes in shape and prevents damage.

The advantage of the method according to the invention is that the lost core has a defined position relative to the machining holder. This avoids positioning problems which could otherwise arise from a subsequent fixation of an already manufactured core element with a lost core on a machining holder. This is because each time a core element is clamped in a machining fixture, stress deformations of the core element can occur. The alternative production of a fixation by gluing takes a long time, and curing tensions in the adhesive can also lead to positional deviations between the core element and the processing holder. Even small deviations in the area of the fixation can lead to larger position deviations away from the fixation. All of this is avoided according to the invention.

1. a) Positionieren eines Keramikrohlings an einem Bearbeitungshalter und Herstellen einer Fixierung zwischen dem Keramikrohling und dem Bearbeitungshalter;
2. b) Herstellen eines Kernelements, wobei ein verlorener Kern aus dem Keramikrohling basierend auf dem 3D-Modell in einem ersten CNC-Herstellungsverfahren gefertigt wird während die Fixierung fortbesteht, wobei der Bearbeitungshalter in einer CNC-Maschine zur Durchführung des ersten CNC-Herstellungsverfahrens festgelegt ist;
3. c) Herstellen eines Modellrohlings durch Gießen von Modellwerkstoff um den verlorenen Kern herum und Erstarrenlassen des Modellwerkstoffs während die Fixierung fortbesteht. Zusätzlich sieht das Verfahren ein Herstellen einer Außenkontur eines verlorenen Modells aus und/oder auf dem Modellrohling basierend auf dem 3D-Modell in einem zweiten CNC-Herstellungsverfahren umfasst, während die Fixierung fortbesteht, wobei der Bearbeitungshalter in einer CNC-Maschine zur Durchführung des zweiten CNC-Herstellungsverfahrens festgelegt ist.

The invention also relates to a method for producing an investment casting mold, in which the following steps are carried out. A method for producing a model mold core in which the following steps are carried out: Carrying out the method for producing a model mold core blank, which is particularly suitable for producing a cast part with a cavity structure, using a 3D model of digital geometry coordinates of the cast part, comprising the following steps:

1. a) positioning a ceramic blank on a processing holder and producing a fixation between the ceramic blank and the processing holder;
2. b) manufacturing a core element, a lost core being manufactured from the ceramic blank based on the 3D model in a first CNC manufacturing process while the fixation continues, the machining holder being fixed in a CNC machine for performing the first CNC manufacturing process;
3. c) Producing a model blank by casting model material around the lost core and allowing the model material to solidify while the fixation continues. In addition, the method includes producing an outer contour of a lost model and / or on the model blank based on the 3D model in a second CNC production process, while the fixation continues, the machining holder in a CNC machine for performing the second CNC -Manufacturing process is specified.

In this method, a ceramic form is applied to the outer contour of the lost model and a positioning connection of the ceramic form is formed with at least one connection point on the core element. Finally, the lost model is removed from the ceramic mold.

The advantage here is that the core element and the lost shape have a high degree of relative positional accuracy to one another by means of the positioning connection. The processing holder has no direct connection to the ceramic mold. This allows it to be removed. The positioning connection should be designed in such a way that the removal of the processing holder has no influence on the relative positioning between the ceramic mold and the lost core. As a result, an inexpensive processing holder can be used that does not have to withstand baking or sintering temperatures or casting temperatures during component production. In addition, reusable machining holders can be used, in particular also those which are made at least in part or completely from tool steel.

The method for manufacturing an investment casting mold can be supplemented by the fact that a stabilization frame is manufactured from the ceramic blank during the first CNC manufacturing process and while the fixation continues, the stabilization frame supporting the lost core, in particular at at least one support point that is spaced apart from the processing holder is arranged. By means of such stabilization frames, very fine lost cores can be made available, which are neither deformed nor damaged during their own production or during subsequent production steps. The stabilizing frame can lie at least partially outside of the model blank. In this area, it will not interfere with further processing of the model blank.

According to the method for producing an investment casting mold, removal of one or more support points between the stabilization frame and the lost core is optionally provided after the production of the lost core and before the production of the model blank, this preferably in the first CNC production process. The lost core is thus kept stable during machining in the first CNC manufacturing process and particularly fine contours can be formed on the lost core. The support points are preferably connecting webs which are preferably narrower and / or thinner than the adjoining area of the lost core.

A machining process, in particular a milling process, and / or a generative manufacturing process such as, for example, 3D printing, selective laser melting or laser sintering, can be used as the first CNC manufacturing process. The preferred method is the milling method.

As an alternative to the process step "Production of a model blank by casting model material around the lost core and allowing the model material to solidify while the fixation continues", a 3D printing process can also be provided in which a model material, for example wax, on and / or is printed around the lost core while the fixation continues. Such 3D printing processes allow particularly complex geometries. With such material-applying processes, either the model blank can be produced, or the whole or at least parts of the outer contour of the lost model can be produced directly.

According to an optional addition to the method, it can be provided that the machining holder is positioned in the executing CNC machine before the first CNC manufacturing method is carried out and before the machining holder is fixed. The advantage here is that the machining holders can be connected to the ceramic blank away from the CNC machine. This reduces machine downtimes, especially if several machining holders have a uniform geometry.

In a special variant of the method, the machining holder has a coupling piece for receiving in a zero point fixing system, the coupling piece being received in a zero point fixing system of the performing CNC machine when the first CNC manufacturing process is carried out. This enables machining holders to be changed quickly in the CNC machine with high positioning precision at the same time. A zero point fixing system is characterized in particular by the fact that no exact positioning has to take place during the production of the fixation. The coupling piece only has to be roughly positioned and the alignment of the coupling piece in the zero point fixing system then takes place automatically during fixing. In particular, defined correlating positioning surfaces contribute to correct positioning in a zero point fixing system, in particular both on the part of the coupling piece and on the part of the zero point fixing system.

Zero point fixing systems in the context of this document are zero point clamping systems and other holding mechanisms (adhesion, gluing, negative pressure, etc.). Zero point clamping systems fix by means of clamping forces. Zero point clamping systems can also be combined with other holding mechanisms so that clamping and other holding forces are used for fixation.

A model wax is particularly suitable as the model material. The model material should have a lower melting temperature than the core element.

According to a special embodiment of the method, a sprue model is formed when the model blank is produced. Such a sprue model will later form a sprue in the ceramic investment casting mold during the production of a ceramic investment casting mold. At the same time, it can be used as an outlet for removing the lost model and / or the lost core. The sprue model is optionally conical. A funnel-shaped sprue then results.

In this application, the abbreviation CNC stands for computer-aided numerical control or manufacturing steps which, in particular, are computer-aided and automated.

The surfaces of the core element can optionally be coated after the first CNC manufacturing process. As a result, the surfaces can be made particularly smooth.

To produce the model blank, the lost core can for example be placed in a model molding tool and the model blank can be formed around the lost core by filling / injecting model material such as wax, thermoplastic or the like into the space between the lost core and the inner walls of the model molding tool.

The ceramic blank can first be brought into the desired blank shape by injection molding, transfer molding or casting of a suitable liquid of ceramic material. The starting material can comprise one or more ceramic powders, a binder and, optionally, additives that can be introduced into a correspondingly shaped blank molding tool. After the ceramic material has hardened to form a "green compact", the blank molding tool can be removed, for example opened, in order to remove the green compact.

After the green compact is removed from the blank mold, it should be fired at a high temperature in one or more steps to remove the volatile binder and to sinter and cure the ceramic blank. As a result, it achieves a strength and dimensional accuracy that are sufficient for use in the casting of metallic material such as a titanium, nickel or cobalt-based alloy.

Optionally, as an introductory process step, the 3D model of the digital geometry coordinates of the cast part can be adapted in order to take into account a correction of manufacturing-related deviations in shape, for example shrinkage or material stresses.

The invention also includes a model mold core blank which is produced by a method for producing a model mold core blank, as described above and below. The advantages of the process are also inherent in the model mold core blank. In particular, it can be manufactured with high precision, process reliability, and inexpensively.

The invention also relates to a method for producing a model mold core, in which the method for producing a model mold core blank, as described above and below, is carried out, and the production of an outer contour of a lost model from and / or based on the model blank comprises on the 3D model in a second CNC manufacturing process, while the fixation continues, wherein the machining holder is set in a CNC machine for performing the second CNC manufacturing process.

The advantage of this is that the lost core assumes a defined position on the machining holder and, as a result, the lost model is also correctly positioned relative to the machining holder and thus also to the lost core.

For this purpose, according to the method, the machining holder is preferably positioned before the second CNC manufacturing method is carried out and before the machining holder is fixed in the CNC machine performing the process. Machining holders with defined geometry can be positioned particularly easily, quickly and precisely in the CNC machine (s) performing the work. During the execution of process steps for which a CNC machine is not required, this CNC machine can be released and used for other purposes.

In a particularly preferred embodiment of the method, the machining holder has a coupling piece for receiving in a zero point fixing system, the coupling piece being received in a zero point fixing system of the performing CNC machine when the second CNC manufacturing process is carried out. This enables the machining holder to be received particularly precisely and quickly in the CNC machine.

The first CNC manufacturing process is preferably a material-removing process, more preferably a cutting process, and particularly preferably a milling process.

The second CNC manufacturing process is preferably either a material-removing process, more preferably a cutting process, and particularly preferably a milling process, or an application process such as 3D printing. The second CNC manufacturing process can also combine removing and depositing processes. This allows different areas of the lost model to be produced particularly efficiently.

The optional stabilizing frame can lie at least partially outside of the lost model. It then has at least partially no contouring influence on the component to be produced later, which in particular will be based on the positive body of the lost model.

The subject matter of the invention also includes a model mold core which is produced according to the method for producing a model mold core, as described above and below. The advantages of the process are also inherent in the model mold core. In particular, it can be manufactured with high precision, process reliability, and inexpensively.

For this purpose, the method can optionally be supplemented by a step in which the fixation between the processing holder and the core element and the separation of the core element from the processing holder take place before or after removing the lost model from the ceramic mold, ie in particular after the application of the ceramic mold or after the lost model has been removed from the ceramic mold, and particularly preferably before the implementation of a casting process for producing the cast part in the investment casting mold.

The ceramic form can be applied to the outer contour of the lost model, for example, by repeated immersion in a ceramic slip, with excess slip flowing off after each immersion, sanding with ceramic stucco and air drying. In this way, several ceramic layers can be built up, which form the ceramic shape in the manner of a molded shell on the outer contour. The resulting arrangement can then be fed to a steam autoclave in order to remove the lost model, so that the ceramic mold with the lost core arranged therein remains as an investment casting mold.

The method can be supplemented by the optional step of firing the arrangement comprising the core element and the ceramic mold before or after the core element is separated from the processing holder. This removes volatile binder and sintered and cured the assembly. As a result, the investment casting mold produced in this way achieves a strength and dimensional accuracy that are sufficient for use in the casting of metallic material such as a titanium, nickel or cobalt-based alloy.

In one variant of the method, when the outer contour of the lost model is produced from the model blank, a sprue model is also formed, in particular from the model blank. This step can include the complete elaboration of the sprue model from the model blank or, if provided, the post-processing of a coarser sprue model already formed on the model blank. Such a sprue model will later form a sprue in the ceramic investment casting mold during the production of a ceramic investment casting mold. At the same time, the sprue can be used as an outlet for removing the lost model and / or the lost core. The sprue model is optionally conical. A funnel-shaped sprue then results.

The subject matter of the invention also includes an investment casting mold which is produced by the method for producing an investment casting mold, as described above and below. The advantages of the process are also inherent in the investment casting mold. In particular, it can be manufactured with high precision, process reliability and inexpensively, with the lost core in particular being correctly positioned and held in the ceramic mold. Sprue structures and ventilation structures for the casting process can then be attached to the investment mold. Alternatively, separate sprue structures can also be used on the lost model as well as ventilation structures for the later casting process are attached so that they are connected to the investment casting mold or are part of it.

The invention also relates to a casting method for producing a casting with a cavity structure, in which a method for producing an investment casting mold, as described above and below, is carried out, and in which molten metal is poured into the ceramic mold around the lost core , solidification of the molten metal to form a solid component, and removal of the ceramic mold and the lost core from the solid component take place. Based on the method, the solid component has cavity structures that are positioned very precisely in the solid component so that, for example, there are no weak points that could render the solid component unusable. In particular, the lost core is removed from the cavity structure of the component. The lost core is preferably removed from the solid component by water-based or chemical washing or other techniques. If the core element also has an optional stabilizing frame, this is also removed from the fixed component.

The casting method preferably comprises the optional step of releasing the fixation between the processing holder and the core element and separating the core element from the processing holder at the latest before the molten metal is poured into the ceramic mold. In this way, an inexpensive processing holder can be used, which at least does not have to withstand the casting temperatures of the molten metal.

The casting process is particularly suitable when the molten metal is a titanium, nickel or cobalt-based alloy. With such expensive components, high costs can be achieved by reducing rejects and component damage in accordance with the method.

Optionally, the investment casting mold is preheated before the molten metal is poured. This can have a positive effect on crystal formation and avoid cracks in the investment mold due to thermal stresses due to sudden temperature changes.

The metal melt preferably solidifies polycrystalline, and particularly preferably monocrystalline. A high component strength is achieved in this way.

Fig. 1

einen Keramikkernrohling an einem Bearbeitungshalter;

Fig. 2

ein Kernelement mit einem verlorenen Kern und einem Stabilisierungsrahmen an einem Bearbeitungshalter;

Fig. 3

einen verlorenen Kern an einem Bearbeitungshalter;

Fig. 4

einen verlorenen Kern an einem Bearbeitungshalter, wobei der verlorene Kern in einem zweiteiligen Modellformwerkzeug zur Herstellung eines Modellrohlings angeordnet ist;

Fig. 5

einen verlorenen Kern an einem Bearbeitungshalter, wobei der verlorene Kern in einem Modellrohling angeordnet ist;

Fig. 6

einen verlorenen Kern an einem Bearbeitungshalter, wobei der verlorene Kern in einem verlorenen Modell angeordnet ist;

Fig. 7

ein verlorenes Modell und einen verlorenen Kern, die von einer keramischen Form einer Feingussform eingehüllt sind; und

Fig. 8

ein Gussteil mit einem festen Bauteil und einer Hohlraumstruktur.

Further features, details and advantages of the invention emerge from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. Show it:

Fig. 1

a ceramic core blank on a machining holder;

Fig. 2

a core member with a lost core and a stabilizing frame on a machining holder;

Fig. 3

a lost core on a work holder;

Fig. 4

a lost core on a machining holder, the lost core being arranged in a two-part model molding tool for producing a model blank;

Fig. 5

a lost core on a machining holder, the lost core being arranged in a model blank;

Fig. 6

a lost core on a machining holder, the lost core being arranged in a lost model;

Fig. 7

a lost pattern and a lost core encased in a ceramic mold of an investment casting mold; and

Fig. 8

a casting with a solid component and a cavity structure.

the Figures 1 to 7 show a possible chronological sequence of process results after various process steps have been carried out. Technical features that have reference symbols, about which statements have already been made in a previous figure, are in some cases not described again. Rather, the preceding parts of the description apply accordingly.

First of all, in Fig. 1 a ceramic core blank 10 which is fixed to a machining holder 50 via a two-sided fixation 51. The fixation 51 can be formed, for example, by gluing or clamping. In the present case, the two sides of the fixation 51 are opposite one another and the ceramic core blank 10 is arranged between the two sides. The processing holder 50 has a coupling piece 52 and a processing bridge 53. The processing bridge 53 extends between the two sides of the fixation 51 and is connected to the coupling piece 52 or formed in one piece with it. The coupling piece 52 is designed for inclusion in a zero point fixing system of CNC processing machines.

The cubature of the ceramic core blank 10 is preselected or prefabricated in such a way that a core element 11 to be produced from the ceramic core blank 10 by material removal or ablation with a lost core 12 lies within this cubature.

Thus, according to the method, it is first necessary to position the ceramic blank 10 on the processing holder 50 and to establish the fixation 51 between the ceramic blank 10 and the processing holder 50 in order to follow the method result Fig. 1 to get.

In Fig. 2 is a possible consequence of the initial situation Fig. 1 after or during the production of the core element 11, the lost core 12 from the ceramic blank 10 (see Fig. 1 ) is manufactured according to a 3D model in a first CNC manufacturing process, for example a CNC milling process, while the fixation 51 continues. At the same time, a (temporary) stabilizing frame 15 is made from the ceramic blank 10 (see FIG Fig. 1 ) manufactured in the first CNC manufacturing process while the fixation 51 continues. The (temporary) stabilization frame 15 supports the lost core 12 via support points 16. The support points 16 are each arranged at a distance from the fixation 51. The support points 16 are connecting webs or pins, each of which is narrower than the adjoining area of the lost core 12.
When the first CNC manufacturing process is being carried out, the machining holder 50 is fixed with the coupling piece 52 in a CNC machine for its implementation.

After completing the first CNC manufacturing process, there remains Fig. 3 the lost core 12 of the core element 11, which extends between the two sides of the fixture 51. It can be seen that the stabilizing frame 15 was removed after the production of the lost core 12, in particular after it was removed from the support points 16.

In the area of the fixation 51, the ceramic core blank 10 (see Fig. 1 ) not processed in order not to weaken the fixation 51 and not to damage the processing holder 50. This unprocessed area of the ceramic core blank 10 (see Fig. 1 ) can also be referred to as the fusing area. At this stage, the core element 11 also has two connection points 13, to which a ceramic mold 81 (see FIG Fig. 7 ) will connect.

According to Fig. 4 is the arrangement according to Fig. 3 It is further used in such a way that the lost core 12 continues to be fixed to the processing holder 50 via the fixation 51 and is stored in a model molding tool 30 for producing a model blank 20 (see FIG Fig. 5 ) is arranged. The model molding tool 30 has a first and a second mold half 31, 32 and is supported by positioning surfaces 33 on the processing holder 50, in particular on the coupling piece 52 and on the processing bridge 53 Model molding tool 30 out. In this way, a tool cavity 35 is formed around the lost core 11. A model sprue 34, which is formed by the model molding tool 30, opens into this tool cavity 35 from above.

The after Fig. 4 The initial situation shown is suitable for the production of a model blank 20 (see Fig. 5 ) by casting model material through the model sprue 34 into the tool cavity 35, that is to say in particular around the lost core 12 located in the tool cavity 35. The model material can be a model wax, for example. The model material should have a lower melting temperature than the core element 11. The model material is then allowed to solidify. The fixation 51 still exists. Correspondingly, the lost core 12 is positioned in a defined position relative to the model blank 20.

The cubatures of the model blank 20 and the tool cavity 35 are each larger than a lost model 21 to be produced from them (see Fig. 6 ).

After removing the model molding tool 30 according to the method status after Fig. 4 the arrangement remains in accordance with Fig. 5 . In Fig. 5 it can be seen how the core element 11 with the lost core 12 is still fixed on the machining holder 50 via the fixation 51. However, the lost core 12 is now also arranged in the model blank 20 made of the model material. This results in a model mold core blank 1. Corresponding to the model sprue 34 of the model molding tool 30, a production-related sprue point 24 also remains on the model blank 20.

With the aid of a corresponding recess in the tool cavity 35, a conical sprue model 23 is also recognizable through the model blank 20.

To follow from the state Fig. 5 to the one after Fig. 6 To achieve this, it is necessary to produce an outer contour 22 of the lost model 21 from the model blank 20, which is carried out according to the 3D model in a second CNC production process, while the fixation 51 continues. For this purpose, the machining holder 50 with the coupling piece 52 can again be fixed in a CNC machine for carrying out the second CNC manufacturing method after it has been positioned. This is particularly easy by using a zero point fixing system. According to the method, the lost core 12 still occupies a defined position on the machining holder 50 and, as a result, the lost model 21 is also correctly positioned relative to the machining holder 50 and thus also to the lost core 12. The lost core 12, together with the lost model 21, forms a model mold core 2.

The second CNC manufacturing process is a material-removing process, preferably a cutting process and particularly preferably a milling process being used.

Should the model blank 20 alternatively have a smaller cubature in whole or in part than the later lost model 21, the outer contour 22 of the lost model 21 is to be produced in these areas by a material-applying process, for example in a (CNC) 3D printing process.

The model mold core 2, namely the lost model 21 and the lost core 12 arranged therein, can now be separated from the processing holder 50, because the goal of arranging the lost core 12 exactly in the lost model 21 has been achieved and will not be adversely affected in the next steps . The fixation 51 is as shown in Fig. 7 can be recognized in particular by the fact that the lost core 12 is separated from the fixing area. The fixing area can remain on the processing holder 50. The fixing area can be removed from this later if necessary.

Fig. 7 also shows how the lost model 21 and the lost core 12 are encased in a ceramic mold 81 of an investment casting mold 80. Only the ends of the lost core 12 look out of the ceramic mold 81. For this purpose, the ceramic mold 81 was applied to the outer contour 22 of the lost model 21 in accordance with the method. The ceramic form 81 can be applied to the outer contour 22 of the lost model 21, for example, by repeated immersion in a ceramic slip, with excess slip flowing off after each immersion, along with sand Ceramic stucco and air drying is done. In this way, several ceramic layers can be built up, which form the ceramic mold 81 in the manner of a molded shell on the outer contour 22. According to the method, it is provided that a positioning connection 82 of the ceramic mold 81 with the two connection points 13 on the core element 11 is established so that the lost core 12 is firmly connected to the ceramic mold 81. For this purpose, the lost core 12 with the connection points 13 protrudes from the lost model 21. The model mold core 2 can be held at these overhangs during the production of the ceramic mold 81, the connection points 13 should be kept free.

Optionally, casting and / or ventilation structure parts can be attached to the lost model 21 before the ceramic mold 81 is applied. These are then preferably connected to the ceramic mold 81 when it is applied.

It can be seen that a sprue 83, which is part of the ceramic mold 81, was also formed with the aid of the sprue model 23.

The lost model 21 can now be removed from the ceramic mold 81, for example by melting it out, with the molten model material being able to run off through the sprue 83. For this purpose, the arrangement according to Fig. 7 for example, be fed to a steam autoclave in order to remove the lost model 21. The ceramic mold 81 with the lost core 12 arranged therein remains as the investment casting mold 80.

If the investment casting mold 80 is not yet sufficiently stable for the subsequent method steps, it can first be fired.

As soon as the investment casting mold 80 is completed, the casting process can be prepared and carried out. The preparation usually includes a change of work location and positioning in a casting device. The investment casting mold 80 is optionally preheated before casting. According to the method, molten metal is then poured through the sprue 83 into the ceramic mold 81 and around the lost core 12. The molten metal can be, for example, a titanium, nickel or cobalt-based alloy. After the molten metal has solidified to form a solid component 102 (see Fig. 8 ) the ceramic mold 81 and the lost core 12 can be removed from the fixed component 102, in particular in a destructive manner. The ceramic shape is typically broken open and / or milled. The lost core 12 can be, for example, by chemical reactions For example, dissolved in water or otherwise dissolved, dissolve and then run out of the remaining cavity structures 101 in the solid component 102.

What remains is a casting 100 as shown in FIG Fig. 8 it is shown that a solid component 101 as well as a cavity structure 102 has in the solid component 101. According to the method, the lost model 21 is therefore a positive model of the cast part 100 and the lost core 12 is a model of the cavity structure 101.

The geometries to be generated in the manufacturing process, in particular the lost core 12 and the lost model 21, are based on the geometry data of the later cast part 100. The geometries to be generated can be determined by using a 3D model of digital geometry coordinates of the cast part 100. If necessary, the geometries to be generated are adapted with respect to the digital geometry coordinates of the cast part 100. This allows shrinkage, component stress and the like to be taken into account in order to finally obtain a physical cast part 100, the shape of which corresponds to the 3D model of digital geometry coordinates of the cast part 100.

The invention is not restricted to one of the embodiments described above, but can be modified in many ways.

In a different variant, it is possible, for example, to add a stabilizing frame 15 with support points 16 based on the process status Fig. 2 to maintain. The stabilizing frame 15 can then support the lost core 12 during the production of the model blank 20 and optionally also during the production of the lost model 21. The stabilizing frame 15 can be arranged at least partially in the model blank 20. However, it can also be at least partially outside the model blank 20. However, the stabilizing frame 15 should be arranged outside the lost model 21. Support points 16 of the stabilization frame 15 can then protrude through the lost model 21 as far as the lost core 12. As a result, lost cores 12 of unstable design are also stabilized during the further process steps.

The alternative of adding a completely or partially smaller model blank 20 to the outer contour 22 of the lost model 21 using a material-applying method such as 3D printing has already been mentioned. <b> List of reference symbols </b> 1 Model mold core blank 32 second mold half 2 Model mold core 33 Positioning surface 34 Model sprue 10 Ceramic blank 35 Mold cavity 11 Core element 12th lost core 50 Machining holder 13th Connection point 51 Fixation 15th Stabilizing frame 52 Coupling piece 16 base 53 Machining bridge 20th Model blank 80 Investment mold 21 lost model 81 ceramic shape 22nd Outer contour 82 positioning connection 23 Sprue model 83 Sprue 24 Gate point 100 Casting 30th Model forming tool 101 Cavity structure 31 first mold half 102 fixed component

Claims (15)

1. A method of manufacturing a model mould core blank (1), in particular suitable for manufacturing a casting (100) having a cavity structure (101), using a 3D model of digital geometry coordinates of the casting (100), the method comprising the following steps:

   a) Positioning a ceramic blank (10) on a processing holder (50) and producing a fixation (51) between the ceramic blank (10) and the processing holder (50);

   b) Manufacturing a core member (11), wherein a lost core (12) is manufactured from the ceramic blank (10) based on the 3D model in a first CNC manufacturing process while the fixture (51) persists, wherein the processing holder (50) is fixed in a CNC machine for performing the first CNC manufacturing process;
   Manufacturing a stabilising frame (15) from the ceramic blank (10) during the first CNC manufacturing process and while the fixture (51) continues, wherein the stabilising frame (15) supports the lost core (12);
   Removing one or more support points (16) between the stabilising frame (15) and the lost core (12) after manufacturing the lost core (12) and before manufacturing the model blank (20);

   c) Producing a model blank (20) by casting model material around the lost core (12) and allowing the model material to solidify while the fixture (51) continues.
2. A method of manufacturing an investment cast mould (80), the method comprising the steps of:

   A) Carrying out a method for manufacturing a model mould core (2), wherein the following steps are carried out in the method (2):

   a. Carrying out the method of manufacturing a model mould core blank (1), in particular suitable for manufacturing a casting (100) with a cavity structure (101), by using a 3D model of digital geometry coordinates of the casting (100), the methos (1) comprising the following steps:

   a) Positioning a ceramic blank (10) on a processing holder (50) and manufacturing a fixation (51) between the ceramic blank (10) and the processing holder (50);

   b) Manufacturing a core member (11), wherein a lost core (12) is manufactured from the ceramic blank (10) based on the 3D model in a first CNC manufacturing process while the fixture (51) persists, wherein the processing holder (50) is fixed in a CNC machine for performing the first CNC manufacturing process;

   c) Producing a model blank (20) by casting model material around the lost core (12) and allowing the model material to solidify while the fixture (51) continues;

   b. Producing an outer contour (22) of a lost model (21) from and/or on the model blank (20) based on the 3D model in a second CNC manufacturing process while the fixture (51) persists, wherein the processing holder (50) is fixed in a CNC machine for performing the second CNC manufacturing process;

   B) applying a ceramic mould (81) to the outer contour (22) of the lost pattern (21) and forming a positioning connection (82) of the ceramic mould (81) to at least one attachment point (13) on the core element (11), wherein the processing holder has no direct connection to the ceramic mould;

   C) Removing the lost pattern (21) from the ceramic mould (81).
3. The method according to claim 2, comprising the following step:

   - manufacturing a stabilising frame (15) from the ceramic blank (10) during the first CNC manufacturing process and while the fixture (51) continues, the stabilising frame (15) supporting the lost core (12).
4. The method according to claim 3, comprising the following step:

   - Removing one or more support points (16) between the stabilising frame (15) and the lost core (12) after manufacturing the lost core (12) and before manufacturing the pattern blank (20).
5. A method according to any one of claims 1 or 3 or 4, comprising the step of:

   - Removal of the stabilising frame (15) after manufacturing the lost core (12) and before manufacturing the pattern blank (20).
6. A method according to any one of the preceding claims, comprising the step of:

   - Positioning the processing holder (50) before performing the first CNC manufacturing process and before fixing the processing holder (50) in the performing CNC machine.
7. A method according to any one of the preceding claims, wherein the processing holder (50) comprises a coupling piece (52) for reception in a zero point fixing system, and wherein the coupling piece (52) is received in a zero point fixing system of the performing CNC machine when performing the first CNC manufacturing process.
8. A method according to any one of the preceding claims, comprising the step of:

   - Formation of a sprue pattern (23) during manufacture of the pattern blank (20).
9. The method of claim 2 or of claim 2 in combination with any one of claims 3 to 8, comprising the step of:

   - Positioning the processing holder (50) before performing the second CNC manufacturing process and before fixing the processing holder (50) in the performing CNC machine.
10. The method of claim 2, or of claim 2 in combination with any one of claims 3 to 9, wherein the processing holder (50) comprises a coupling piece (52) for reception in a zero point fixing system, and wherein the coupling piece (52) is received in a zero point fixing system of the performing CNC machine when performing the second CNC manufacturing process.
11. A method according to claim 2 or according to claim 2 in combination with any one of claims 3 to 10, wherein a sprue pattern (23) is formed from the pattern blank (20) when producing the outer contour (22) of the lost pattern (21).
12. The method of claim 2 or of claim 2 in combination with any one of claims 3 to 11, wherein the following step is performed:

    - Releasing the fixation (51) between the processing holder (50) and the core element (11) and separating the core element (11) from the processing holder (50) before or after removing the lost pattern (21) from the ceramic mould (81).
13. The method of claim 12, wherein the following step is performed:

    - firing the assembly comprising the core element (11) and the ceramic mould (81) after separating the core element (11) from the processing holder (50).
14. A casting method for manufacturing a casting (100) having a cavity structure (101), wherein the following steps are carried out in the method:

    i) Performing the method of manufacturing an investment cast mould (80) according to any one of claims 2 to 13;

    ii) Pouring molten metal into the ceramic mould (81) around the lost core (12);

    iii) Solidification of the molten metal into a solid component (102);

    iv) Removing the ceramic mould (81) and the lost core (12) from the solid component (102).
15. The method of claim 14, wherein the following step is performed:
    i.b) removing the fixation (51) between the processing holder (50) and the core element (11) and separating the core element (11) from the processing holder (50) at the latest before pouring the molten metal into the ceramic mould (81).

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