Method for manufacturing a molded part, molded part and method for manufacturing a component

Abstract

The invention relates to a method for manufacturing a mold for use in a casting method, wherein the mold is manufactured by means of additive manufacturing, the method comprising the step of: - introducing at least one unloading joint into the mold during the manufacturing to avoid or reduce tensile stresses in the mold.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a molded part for use in a casting process, a molded part, particularly a casting core, and a method for manufacturing a component. Background Technology

[0002] It is known in the prior art that additive manufacturing methods are used to produce molded parts, such as casting cores. This is necessary because the geometry of the cores is often so complex that other methods for manufacturing cores are less suitable. For example, water jacket cores used in the manufacture of, for example, internal combustion engines for automobiles have such complex geometries. DE102018216271A1 discloses a sand core for use in a method for manufacturing a housing block having a channel structure, wherein the sand core is made by a generative method. However, problems have arisen in practice, namely, cracks can occur in cores made in this way, for example, due to inherent stress. Such cores cannot be used or, in other words, will lead to scrap when using such cores. Summary of the Invention

[0003] Therefore, the objective of this invention is to provide a method for manufacturing a molded part, a molded part, and a method for manufacturing a component, wherein the aforementioned problems are cost-effectively avoided.

[0004] Such a task is accomplished by the method according to the invention, by the molding according to the invention, and by the method according to the invention. Other advantages and features will become apparent from the description and the accompanying drawings.

[0005] According to the present invention, a method for manufacturing a molded part for use in a casting method ( wherein the molded part is made by means of additive manufacturing) comprises the following steps:

[0006] - During the manufacturing of the molded part, at least one unloading seam is introduced into the molded part to avoid or reduce stress in the molded part.

[0007] The stresses, particularly inherent stresses or tensile stresses, or generally stresses or forces (in molded parts), cause damage to the molded part, especially, for example, at least partially fracture or tear. Typically, (inherent) stresses are generated in sections or regions of the molded part during its manufacture or further use, rendering it unusable or potentially unusable for further use. Such stresses can, for example, prevent thermal expansion / contraction during the (thermal) hardening process of the molded part in additive manufacturing. Crack susceptibility can also be induced by mechanically and / or thermally induced stresses during the casting process. To eliminate these problems, it is now proposed to specifically introduce at least one unloading seam into a critical area, thereby particularly preventing uncontrolled crack formation.

[0008] According to one embodiment, the method includes the following steps:

[0009] Unloading seams are formed by introducing gaps that at least partially pass through the molded part.

[0010] Such gaps or slits act like floating bearings in crack-prone areas. The inherent stress can be reduced or avoided in the stress direction by introducing targeted material recesses (e.g., material recesses in the form of gaps or slits), which result in expansion / movement degrees of freedom. Unloading seams advantageously open up one or at least one additional degree of freedom for expansion / movement in the relevant area of ​​the molded part, thereby preventing the formation of significant (inherent) stress from the outset, for example, during printing / curing.

[0011] Here, the unloading joint is suitably designed so that molten casting cannot intrude, or at least largely prevents, molten casting from intruding. For this purpose, the gap is suitably constructed to be small. Alternatively, the unloading joint may be suitably relocated, whenever possible, to an area easily accessible for reprocessing, thereby enabling the cost-effective removal of any possible casting burrs or similar defects.

[0012] According to one embodiment, the method includes the following steps:

[0013] - This creates an unloading seam, making adjacent or generated molded sections immovable from each other in at least one spatial direction.

[0014] Appropriately, such a process can achieve the following: despite the additional degrees of freedom, the individual molded sections are still positioned and fixed, or rather, kept in place of each other.

[0015] According to a preferred embodiment, the unloading seam is accordingly configured as recessed or stepped, especially multi-stepped. According to one embodiment, the unloading seam forms at least one pouch-like portion or at least one side recess.

[0016] As already mentioned, the unloading seam is constructed to at least partially extend through the gaps or slits in the molded part. According to one embodiment, the gaps or slits are not constructed to be completely continuous. For example, small connecting elements, such as connecting tabs, may be constructed between the various molded part sections. These connecting elements serve as small theoretical break points and facilitate the handling of the core because they provide stability. It is also possible that the slits or tabs are not designed to create complete continuity from the outset.

[0017] According to one embodiment, the method includes the following steps:

[0018] - Unloading seams are created by intentionally preventing the starting material from curing during the manufacturing of molded parts.

[0019] The current approach is not specific to additive manufacturing methods. The basic approach for creating unloading seams through targeted non-curing can be applied to the most diverse methods.

[0020] According to one embodiment, molded parts are manufactured by means of binder jetting. In binder jetting (also known as 3D printing), powdered starting material can be bonded with binder at selected locations to thus produce a workpiece, currently a molded part. Particularly preferred is the manufacture of molded parts by means of sandblasting. The resulting sand layer can be wetted with binder and then thermally cured. Suitably, the method includes the following steps:

[0021] - An unloading seam is created by selectively stopping the adhesive input.

[0022] In other words, by selectively avoiding the introduction of adhesives, loose sand is left in the appropriate locations after the molded part has hardened.

[0023] The loose sand retained in the unloading joint due to the process advantageously ensures the passive positioning of each molded part segment relative to each other. The sliding of the loose sand balls within the unloading joint enables slight movement for unloading. In other words, the molded part segments can be advantageously supported by the sand balls.

[0024] Advantageously, the aforementioned bag-shaped or side-recessed portions are designed and formed such that loose sand / molding material is retained in this area of ​​the unloading joint, thereby enabling the individual molded sections to support each other. The loose sand is thus retained in the unloading joint, which locally functions similarly to a labyrinth seal structure.

[0025] Suitablely, the method includes the following steps:

[0026] - Clean, especially blow out, unloading seams before using molded parts.

[0027] The cleaning can be performed using compressed air. According to one embodiment, the unloading joint is completely removed of loose sand / molding material before further use of the molded part. Other preferred cleaning methods include suction and agitation. Alternatively, the cleaning can also be performed by displacement, particularly pivoting or rotating, or rotating the molded part (or alternatively, a combination thereof), so that loose particles, especially loose sand, can fall out.

[0028] According to one embodiment, the unloading joint is formed in such a way that complete removal of the (sand) particles is impossible, see the aforementioned side recess or bag-like portion. As already mentioned, the sand particles can be passively positioned. Here, the unloading joint is suitably formed in such a way that the particles do not fall out even during further use or handling of the molded part. If necessary, the particles can also be retained in the unloading joint throughout the casting process.

[0029] According to a preferred embodiment, the molded part is a core, particularly a sand core. According to a particularly preferred embodiment, the core is, for example, a crankcase or, more preferably, a cylinder head of an internal combustion engine, a fluid core, such as an oil chamber core and / or a water jacket core. According to one embodiment, the core is, for example, an exhaust manifold core or a water jacket core of a cylinder head of an internal combustion engine, preferably for passenger cars. However, the molded part is not limited to being used as a core.

[0030] According to one embodiment, the method includes the following steps:

[0031] - Before manufacturing the molded part, simulate and identify the crack-prone areas in the molded part.

[0032] - When manufacturing the molded part, at least one unloading seam is introduced into the area.

[0033] Suitablely, the unloading seam or multiple unloading seams are pre-reserved in the data model (on which the molded part is generated)

[0034] The present invention also relates to a molded part, particularly a casting core, which is manufactured according to the method according to the invention. Preferably, the molded part is used in metal casting methods, particularly gravity casting, low-pressure casting, or also in pressure casting. Regarding its use in pressure casting, it should be noted that alternative materials are used there for core manufacturing. Preferred molten metals are, for example, molten aluminum.

[0035] The material used for the molded part depends on its further application. When using molded parts / cores in sand casting or die casting, appropriate molding materials are used. Such molding materials include molding base material, molding material binder, and molding additives. Regarding the proposed scheme for introducing unloading seams, there are no restrictions on the choice of molding material.

[0036] The present invention also relates to a method for manufacturing a component, wherein at least one molded part according to the invention is used for the casting. According to a preferred embodiment, the component is a cast part, particularly a motor part, such as a cylinder head of an internal combustion engine for a passenger car, commercial vehicle, or motorcycle. The examples mentioned above should not be construed as limiting. Attached Figure Description

[0037] Other advantages and features will become apparent from the following description of the embodiments of the molded part with the aid of the accompanying drawings. In the drawings:

[0038] Figure 1 A schematic diagram of a molded part used to illustrate crack formation is shown;

[0039] Figure 2 A schematic diagram showing one embodiment of the molded part;

[0040] Figure 3 Two additional views showing one embodiment of the molded part;

[0041] Figure 4 Another view showing one embodiment of the molded part is shown. Detailed Implementation

[0042] Figure 1 A molded part 10, schematically shown, is formed, for example, by means of adhesive spraying. During the core printing process and in the subsequent curing process, the adhesive hardens by dehydration. At this time, inherent stresses are generated in the molded part 10, shown here by arrows pointing away from each other; these inherent stresses can lead to cracks, see crack 20 currently schematically shown. Such a molded part 10 is, for example, unsuitable for further use. If the molded part 10 is a cast core, unidentified core fractures and / or uncontrolled intrusion of molten material into cracks during the casting of the component can render the manufactured component unusable.

[0043] Figure 2 A schematic diagram of a molded part 10 is shown, which includes an unloading seam 40. Two molded part segments 11 and 12 are currently formed, each of which can move away from each other along the x-axis (see the coordinate system shown). The unloading seam 4 opens up a degree of freedom, thereby preventing significant inherent stresses from forming in critical regions, for example, during the printing / curing process.

[0044] Figure 3A further embodiment of the molded part 10 is illustrated schematically, the molded part including an unloading seam 40. The unloading seam 40 is currently designed such that the molded part segments 11 and 12 are form-locked to each other. The unloading seam is therefore constructed in a stepped manner, with the molded part 10 rotated 90° in the lower half of the figure. This formation of the unloading seam 40 ensures that the molded part segments 11 and 12 can support each other not only in the y-direction but also in the z-direction. Loose sand / molding material retained in the unloading seam 40 due to the process ensures that the molded part segments 11 and 12 are passively positioned relative to each other. Furthermore, the sliding of loose sand balls within the unloading seam allows for slight movement of the two molded part segments 11 and 12 relative to each other for unloading.

[0045] Figure 4 Another embodiment of the molded part 10, shown schematically, is provided in which the unloading seam 40 currently includes or is constructed with a pouch-like portion or side recess. Such side recesses can secure the respective molded part segments 11 and 12 in all spatial directions. Furthermore, this geometry allows the sand / molding material retained in the unloading seam 40 to remain there and not accidentally fall out during subsequent use of the molded part 10. This is advantageous because the two molded part segments 11 and 12 can be supported against each other via loose sand in the unloading seam 40, which contributes to the stability of the molded part 10.

[0046] List of reference numerals

[0047] 10 molded parts

[0048] 11-section molded parts

[0049] 12-mold part section

[0050] 20 cracks

[0051] 40 Unloading seams

[0052] x, y, z coordinate system, (spatial) direction.

Claims

1. A method for manufacturing a molded part (10) for use in a casting process, in, The molded part (10) is manufactured by means of additive manufacturing, the method comprising the following steps: - Before manufacturing the molded part (10), the crack-prone areas in the molded part are simulated and identified; and - During the manufacturing process, at least one unloading seam (40) is introduced into the region of the molded part (10) to avoid or reduce stress in the molded part (10).

2. The method according to claim 1, wherein the method comprises the following steps: - The unloading seam (40) is formed by introducing a gap that at least partially passes through the molded part (10).

3. The method according to claim 1 or 2, wherein the method comprises the following steps: - Form the unloading seam (40) such that adjacent or generated molding segments (11, 12) are immovable from each other in at least one spatial direction (x, y, z).

4. The method according to claim 1 or 2, wherein, The unloading joint (40) is constructed in a stepped manner.

5. The method according to claim 1 or 2, wherein the method comprises: - When manufacturing the molded part (10), unloading seams (40) are created by selectively preventing the starting material from curing.

6. The method according to claim 1 or 2, wherein, To manufacture the molded part (10), adhesive spraying is used, and the method includes the following steps: - Create unloading seams (40) by selectively stopping adhesive input.

7. The method according to claim 1 or 2, wherein the method comprises the following steps: - Clean the unloading seam (40) before using the molded part (10).

8. The method according to claim 1 or 2, wherein, The molded part (10) is a core.

9. The method according to claim 1 or 2, wherein, The unloading joint (40) is constructed in a multi-step manner.

10. The method according to claim 1 or 2, wherein, The method includes the following steps: - Before using the molded part (10), blow clean the unloading seam (40).

11. The method according to claim 1 or 2, wherein, The molded part (10) is a sand core.

12. A molded part (10) made according to any one of claims 1 to 11.

13. The molded part (10) according to claim 12, wherein, The molded part is a cast core.

14. A method for manufacturing a component, wherein, Use at least one molded part (10) as described in claim 12.

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