Method for producing a model mold core blank and a precision casting mold, and a casting method for producing a cast part having a void structure

Abstract

A method for producing a model mould core blank uses a ceramic blank fixed to a processing holder. During fixing, a lost core is manufactured from the ceramic blank based on a CNC manufacturing process 3D model, the processing holder being fastened in the running CNC machine. A model blank is produced by casting model material around the lost core while fixing persists. The model blank becomes part of another method for producing a model mould core, wherein an outer contour of a lost model is produced from and/or on the model blank on the basis of a second CNC manufacturing process 3D model, wherein fixing and processing holder fastening also occurs. Another method produces a precision casting mould, in which a ceramic mould is applied to the outer contour of the lost model, and a cast part having a hollow cavity structure is produced by the precision casting mould.

Claims

1. A method for producing a model mold core blank (1), which is suitable for producing a cast part (100) having a void structure (101), using a 3D model with digital geometrical coordinates of the cast part (100), comprising the following steps: a) positioning a ceramic blank (10) on a processing mount (50) and producing a fixing (51) between the ceramic blank (10) and the processing mount (50); b) producing a core element (11), by manufacturing a lost core (12) from the ceramic blank (10) on the basis of the 3D model of the cast part (100) in a first CNC production process during the fixing (51) of step (a), wherein the processing mount (50) is fixed in a CNC machine for carrying out the first CNC production process; producing a stabilizing frame (15) from the ceramic blank (10) during the first CNC production process and during the fixing (51) of step (a), the stabilizing frame (15) supporting the lost core (12) manufactured from the same ceramic blank; and c) producing a model blank (20) by casting modelling material around the lost core (12) and allowing the modelling material to solidify during the fixing (51) of step (a).

2. The method as claimed in claim 1, comprising the following step: positioning the processing mount (50) before carrying out the first CNC production process and before the processing mount (50) is fixed in the CNC machine carrying out the process.

3. The method as claimed in claim 1, wherein the processing mount (50) has a coupling piece (52) for accommodation in a zero point fixing system, and wherein, when carrying out the first CNC production process, the coupling piece (52) is accommodated in a zero point fixing system of the CNC machine carrying out the process.

4. The method as claimed in claim 1, comprising the following step: removing one or more supporting points (16) between the stabilizing frame (15) and the lost core (12) after production of the lost core (12) and before producing the model blank (20).

5. The method as claimed in claim 1, comprising the following step: removing the stabilizing frame (15) after production of the lost core (12) and before producing the model blank (20).

6. The method as claimed in claim 1, comprising the following step: forming a sprue model (23) during production of the model blank (20).

7. The method as claimed in claim 1, wherein the 3D model with the digital geometrical coordinates of the cast part is optionally adapted in order to take into consideration a correction of manufacturing-related dimensional deviations due to shrinkage or material stresses.

8. A method for producing a precision casting mold (80), in which the following steps are carried out: A) carrying out a method for producing a model mold core (2), in which the following steps are carried out: a. a method for producing a model mold core blank (1), which is suitable for producing a cast part (100) having a void structure (101), using a 3D model with digital geometrical coordinates of the cast part (100), comprising the following steps: i) positioning a ceramic blank (10) on a processing mount (50) and producing a fixing (51) between the ceramic blank (10) and the processing mount (50); ii) producing a core element (11), wherein a lost core (12) is manufactured from the ceramic blank (10) on the basis of the 3D model in a first CNC production process during the fixing (51) of step a)(i), wherein the processing mount (50) is fixed in a CNC machine for carrying out the first CNC production process; iii) producing a model blank (20) by casting modelling material around the lost core (12) and allowing the modelling material to solidify during the fixing (51) of step a)(i); b. producing a lost model (21) with an outer contour (22) from the model blank (20) on the basis of the 3D model in a second CNC production process during the fixing (51) of step a)(i), wherein the processing mount (50) is fixed in a CNC machine for carrying out the second CNC production process; B) applying a ceramic mold (81) to the outer contour (22) of the lost model (21) and forming a positioning connection (82) of the ceramic mold (81) to at least one attachment point (13) on the core element (11), wherein the processing mount (50) does not have any direct connection to the ceramic mold (81); and C) removing the lost model (21) from the ceramic mold (81).

9. The method as claimed in claim 8, comprising the following step: positioning the processing mount (50) before carrying out the second CNC production process and before the processing mount (50) is fixed in the CNC machine carrying out the process.

10. The method as claimed in claim 9, wherein the processing mount (50) has a coupling piece (52) for accommodation in a zero point fixing system, and wherein, when carrying out the second CNC production process, the coupling piece (52) is accommodated in a zero point fixing system of the CNC machine carrying out the process.

11. The method as claimed in claim 8, wherein the processing mount (50) has a coupling piece (52) for accommodation in a zero point fixing system, and wherein, when carrying out the second CNC production process, the coupling piece (52) is accommodated in a zero point fixing system of the CNC machine carrying out the process.

12. The method as claimed in claim 8, wherein a sprue model (23) is formed during the producing of the lost model (21) with the outer contour (22) from the model blank (20).

13. The method as claimed in claim 8, wherein the following step is carried out: removing the fixing (51) between the processing mount (50) and the core element (11) and separating the core element (11) from the processing mount (50) before or after removing the lost model (21) from the ceramic mold (81).

14. The method as claimed in claim 13, wherein the following step is carried out: firing an arrangement comprising the core element (11) and the ceramic mold (81) after separating the core element (11) from the processing mount (50).

15. The method as claimed in claim 8, comprising the following step: producing a stabilizing frame (15) from the ceramic blank (10) during the first CNC production process and during the fixing (51) of step a)(i), wherein the stabilizing frame (15) supports the lost core (12).

16. The method as claimed in claim 15, comprising the following step: removing one or more supporting points (16) between the stabilizing frame (15) and the lost core (12) after production of the lost core (12) and before producing the model blank (20).

17. The method as claimed in claim 15, comprising the following step: removing the stabilizing frame (15) after production of the lost core (12) and before producing the model blank (20).

18. The method as claimed in claim 8, comprising the following step: positioning the processing mount (50) before carrying out the first CNC production process and before the processing mount (50) is fixed in the CNC machine carrying out the process.

19. The method as claimed in claim 8, wherein the processing mount (50) has a coupling piece (52) for accommodation in a zero point fixing system, and wherein, when carrying out the first CNC production process, the coupling piece (52) is accommodated in a zero point fixing system of the CNC machine carrying out the process.

20. The method as claimed in claim 8, comprising the following step: forming a sprue model (23) during production of the model blank (20).

21. A casting method for producing a cast part (100) having a void structure (101), in which the following steps are carried out: i.a) carrying out the method for producing a precision casting mold (80) as claimed in claim 8; ii) casting molten metal into the ceramic mold (81) around the lost core (12); iii) solidifying the molten metal to form a solid component (102); iv) removing the ceramic mold (81) and the lost core (12) from the solid component (102).

22. The method as claimed in claim 21, wherein the following step is carried out: i.b) removing the fixing (51) between the processing mount (50) and the core element (11) and separating the core element (11) from the processing mount (50) no later than before the molten metal is cast into the ceramic mold (81).

Description

(1) Further features, details and advantages of the invention become apparent from the phrasing of the claims and from the following description of exemplary embodiments with reference to the drawings, in which:

(2) FIG. 1 shows a ceramic core blank on a processing mount;

(3) FIG. 2 shows a core element with a lost core and with a stabilizing frame on a processing mount;

(4) FIG. 3 shows a lost core on a processing mount;

(5) FIG. 4 shows a lost core on a processing mount, wherein the lost core is arranged in a two-part model molding tool for producing a model blank;

(6) FIG. 5 shows a lost core on a processing mount, wherein the lost core is arranged in a model blank;

(7) FIG. 6 shows a lost core on a processing mount, wherein the lost core is arranged in a lost model;

(8) FIG. 7 shows a lost model and a lost core which are enveloped by a ceramic mold of a precision casting mold; and

(9) FIG. 8 shows a cast part with a solid component and a void structure.

(10) FIGS. 1 to 7 show a possible chronological sequence of method results after carrying out various method steps. Technical features having reference signs about which statements have already been made in a preceding figure are to some extent not described again. Rather, the preceding parts of the description apply correspondingly.

(11) Firstly, a ceramic core blank 10, which is fixed to a processing mount 50 via a fixing 51 on two sides, can be seen in FIG. 1. The fixing 51 can be formed for example by adhesive bonding or clamping. In the present case, the two sides of the fixing 51 are situated opposite one another and the ceramic core blank 10 is arranged between the two sides. In this respect, the processing mount 50 has a coupling piece 52 and a processing bridge 53. The processing bridge 53 extends between the two sides of the fixing 51 and is connected to or formed in a unipartite manner with the coupling piece 52. The coupling piece 52 is designed for accommodation in a zero point fixing system of CNC machine tools.

(12) The cubature of the ceramic core blank 10 is preselected or prefabricated such that a core element 11 which has a lost core 12 and is to be produced from the ceramic core blank 10 by material removal lies within this cubature.

(13) In this way, therefore, according to the method, it is necessary first to position the ceramic blank 10 on the processing mount 50 and to produce the fixing 51 between the ceramic blank 10 and the processing mount 50, in order to arrive at the method result according to FIG. 1.

(14) FIG. 2 illustrates a possible outcome of the starting situation according to FIG. 1 after or during the production of the core element 11, wherein the lost core 12 is manufactured from the ceramic blank 10 (see FIG. 1) in accordance with a 3D model in a first CNC production process, for example a CNC milling process, while the fixing 51 persists. At the same time, a (temporary) stabilizing frame 15 is produced from the ceramic blank 10 (see FIG. 1) in the first CNC production process while the fixing 51 persists. The (temporary) stabilizing frame 15 supports the lost core 12 by way of supporting points 16. Each of the supporting points 16 is arranged spaced apart from the fixing 51. The supporting points 16 are connecting webs or pegs, each of which is narrower than the adjoining region of the lost core 12.

(15) When carrying out the first CNC production process, the processing mount 50 is fixed to the coupling piece 52 in a CNC machine for the purpose of carrying out said first CNC production process.

(16) After completion of the first CNC production process, according to FIG. 3 the lost core 12 of the core element 11 remains, said lost core extending between the two sides of the fixing 51. It can be seen that the stabilizing frame 15 has been removed after the production of the lost core 12, in particular after removing the supporting points 16.

(17) The ceramic core blank 10 (see FIG. 1) has not been processed in the region of the fixing 51, in order not to weaken the fixing 51 and in order not to damage the processing mount 50. This unprocessed region of the ceramic core blank 10 (see FIG. 1) can also be referred to as fixing region. Already at this stage, the core element 11 also has two attachment points 13 to which later a ceramic mold 81 (see FIG. 7) is connected.

(18) According to FIG. 4, the arrangement as per FIG. 3 is reused in such a way that the lost core 12 is also fixed to the processing mount 50 via the fixing 51 and is arranged in a model molding tool 30 for producing a model blank 20 (see FIG. 5). The model molding tool 30 has a first and a second mold half 31, 32 and is supported on the processing mount 50 via positioning surfaces 33, in particular on the coupling piece 52 and on the processing bridge 53. In the region of the attachment points 13, the core element 11 protrudes out of the model molding tool 30 through openings. 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 out from above into this tool cavity 35.

(19) The starting situation, shown according to FIG. 4, is now suitable for carrying out production of a model blank 20 (see FIG. 5) in that modelling material is cast through the model sprue 34 into the tool cavity 35, in particular i.e. around the lost core 12 lying in the tool cavity 35. The modelling material can be, for example, a modelling wax. The modelling material should have a lower melting temperature than the core element 11. The modelling material is then allowed to solidify. In the process, the fixing 51 continues to exist. The lost core 12 is correspondingly positioned in a defined position relative to the model blank 20.

(20) The cubatures of the model blank 20 and of the tool cavity 35 are each greater than a lost model 21 to be produced therefrom (see FIG. 6).

(21) After the model molding tool 30 is removed according to the method state as per FIG. 4, the arrangement as per FIG. 5 remains. The manner in which the core element 11 with the lost core 12 is also fixed to the processing mount 50 via the fixing 51 can be seen in FIG. 5. Now, however, the lost core 12 is arranged additionally in the model blank 20 composed of the modelling material. The result of this is a model mold core blank 1. In a manner corresponding to the model sprue 34 of the model molding tool 30, a manufacturing-related sprue point 24 also still remains on the model blank 20.

(22) Using a corresponding cutout in the tool cavity 35, a conical sprue model 23 is also formed, as can be seen through the model blank 20.

(23) In order to arrive at the state as per FIG. 6 from that of FIG. 5, it is necessary to produce an outer contour 22 of the lost model 21 from the model blank 20, this being carried out in accordance with the 3D model in a second CNC production process, while the fixing 51 continues to persist. For this purpose, the processing mount 50 with the coupling piece 52 can be fixed again in a CNC machine for carrying out the second CNC production process, after said production mount has been positioned. This is achieved particularly easily by using a zero point fixing system. According to the method, the lost core 12 thus still assumes a defined position on the processing mount 50 and consequently the lost model 21 is also positioned correctly relative to the processing mount 50 and thus also to the lost core 12. The lost core 12 forms together with the lost model 21 a model mold core 2.

(24) The second CNC production process is a material-removing process, wherein preferably a machining process, and particularly preferably a milling process, are used.

(25) As an alternative, should the model blank 20 as a whole or in part have a smaller cubature than the later lost model 21, the outer contour 22 of the lost model 21 in these regions should be produced by a material-depositing process, for example in a (CNC) 3D printing process.

(26) The model mold core 2, specifically the lost model 21 and the lost core 12 arranged therein, can now be separated from the processing mount 50, because the aim of arranging the lost core 12 exactly in the lost model 21 is achieved and is not negatively influenced in the next steps. As can be seen in FIG. 7, the fixing 51 is in particular removed by separating the lost core 12 from the fixing region. Here, the fixing region can remain on the processing mount 50. The fixing region can be removed from said processing mount later as required.

(27) FIG. 7 also shows how the lost model 21 and the lost core 12 are enveloped by a ceramic mold 81 of a precision casting mold 80. Only the ends of the lost core 12 still protrude from the ceramic mold 81. For this purpose, according to the method, the ceramic mold 81 has been applied to the outer contour 22 of the lost model 21. The ceramic mold 81 can be applied to the outer contour 22 of the lost model 21 for example by virtue of repeated immersion into a ceramic slip, wherein, after each immersion, excess slip flows off and sanding with ceramic stucco and air drying take place. In this way, a plurality of ceramic layers which form the ceramic mold 81 on the outer contour 22 in the manner of a mold shell can be built up. Provision is made here according to the method that a positioning connection 82 of the ceramic mold 81 to the two attachment points 13 is produced on the core element 11, with the result that the lost core 12 is fixedly connected to the ceramic mold 81. For this purpose, the lost core 12 protrudes with the attachment points 13 out of the lost model 21. The model mold core 2 can be held during the production of the ceramic mold 81 at these protrusions, wherein the attachment points 13 should be kept clear.

(28) Before applying the ceramic mold 81, sprue and/or ventilation structural parts can optionally be attached to the lost model 21. These structural parts are then connected to the ceramic mold 81 preferably when it is being applied.

(29) It can be seen that, using the sprue model 23, a sprue 83 which is part of the ceramic mold 81 has also been formed.

(30) The lost model 21 can now be removed from the ceramic mold 81, for example by being melted out, wherein the molten modelling material can drain through the sprue 83. For this purpose, the arrangement as per FIG. 7 can be fed for example 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 precision casting mold 80.

(31) Where the precision casting mold 80 is not yet sufficiently stable for the subsequent method steps, it can firstly be fired.

(32) As soon as the precision casting mold 80 is finished, the casting process can be prepared and carried out. The preparation usually includes a change of work area and positioning in a casting device. The precision casting mold 80 is optionally preheated before the casting. According to the method, what follows is molten metal being cast through the sprue 83 into the ceramic mold 81 and around the lost core 12. The molten metal can be, for example, a titanium-based, nickel-based or cobalt-based alloy. After the metal melt 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 solid component 102, in particular in a destructive manner. The ceramic mold is typically broken open and/or milled open. The lost core 12 can be dissolved for example by chemical reactions, for example dissolved in water or dissolved in another way, and then runs out of the remaining void structures 101 in the solid component 102.

(33) A cast part 100 usually remains, as shown in FIG. 8, and comprises a solid component 102 as well as a void structure 101 in the solid component 102. According to the method, the lost model 21 is thus a positive model of the cast part 100 and the lost core 12 is a model of the void structure 101.

(34) The geometries to be created in the production processes, in particular of the lost core 12 and the lost model 21, are based on the geometrical data of the later cast part 100. The geometries to be created can be determined by using a 3D model with the digital geometrical coordinates of the cast part 100. If necessary, the geometries to be created are adapted with respect to the digital geometrical coordinates of the cast part 100. In this way, shrinkage, component stresses and the like can be taken into consideration in order to finally obtain a physical cast part 100, the form of which corresponds to the 3D model with the digital geometrical coordinates of the cast part 100.

(35) The invention is not restricted to one of the embodiments described above, but can be modified in a wide variety of ways.

(36) In a different variant, it is possible for example to retain a stabilizing frame 15 having supporting points 16 by way of the method state as per FIG. 2. The stabilizing frame 15 can then support the lost core 12 also during the production of the model blank 20 and optionally also during the production of the lost model 21. In this respect, the stabilizing frame 15 can be arranged at least partially in the model blank 20. Said stabilizing frame can, however, also lie at least partially outside the model blank 20. However, the stabilizing frame 15 should be arranged outside the lost model 21. Supporting points 16 of the stabilizing frame 15 can then protrude through the lost model 21 as far as the lost core 12. In this way, even lost cores 12 with an unstable configuration are stabilized during the further method steps.

(37) The alternative of adding a fully or partially smaller model blank 20 to the outer contour 22 of the lost model 21 by a material-depositing process such as 3D printing has already been mentioned.

(38) All of the features and advantages, including structural details, spatial arrangements and method steps, arising from the claims, the description and the drawing may be essential to the invention, both individually and in a wide variety of combinations.

LIST OF REFERENCE SIGNS

(39) TABLE-US-00001 1 Model mold core blank 2 Model mold core 10 Ceramic blank 11 Core element 12 Lost core 13 Attachment point 15 Stabilizing frame 16 Supporting point 20 Model blank 21 Lost model 22 Outer contour 23 Sprue model 24 Sprue point 30 Model molding tool 31 First mold half 32 Second mold half 33 Positioning surface 34 Model sprue 35 Tool cavity 50 Processing mount 51 Fixing 52 Coupling piece 53 Processing bridge 80 Precision casting mold 81 Ceramic mold 82 Positioning connection 83 Sprue 100 Cast part 101 Void structure 102 Solid component