Method for Producing a Lost Casting Core

Abstract

The invention names a method for producing a lost casting core (G), which has a side surface (S1, S2), in a core box (1) that is divided into two core box parts (2, 3) in a parting plane (T), and which box delimits a mold cavity (8) in which an inner surface (14, 15) that reproduces the side surface (S1, S2) of the casting core (G) is provided, through which surface the parting plane (T) of the core box (1) runs. To prevent a burr in a critical section of the side surfaces (S1, S2) of the casting core (G), the following work steps are carried out: (a) producing a casting core insert (E) having a side surface section (SF1, SF2) that is equal to a corresponding section of the side surface of the casting core (G), from a casting core molding material (F); (b) positioning the casting core insert (E) in the mold cavity (8) of the core box (1) in such a manner that the side surface section (SF1, SF2) of the casting core insert (E) sits in the place of the corresponding section of the side surface (S1, S2) of the finished casting core (G), wherein the parting plane (T) runs through the side surface section (SF1, SF2); (c) introducing a casting core molding material (F) into the mold cavity (8) of the core box (1), so as to form the remaining casting core (G), wherein the introduced casting core molding material (F) comes into contact with the casting core insert (E); (d) solidifying the casting core molding material (F), thereby forming a shape-fit and/or material-fit connection between the introduced casting core molding material (F) and the casting core insert (E).

Claims

1. A method for producing a lost casting core (G), which has a side surface (S1, S2), in a core box (1) that is composed of at least two core box parts (2, 3), between which parts a parting plane (T) runs when the core box (1) is closed, and which box delimits a mold cavity (8) that determines the shape of the casting core (G) to be produced, and in which box an inner surface (14, 15) that reproduces the side surface (S1, S2) of the casting core (G) is provided, through which surface the parting plane (T) of the core box (1) runs, comprising the following work steps: (a) producing a casting core insert (E) in one piece from a casting core molding material (F), which is mixed together from a basic molding material and a binder, as well as, optionally, one or more additives, wherein the casting core insert (E) corresponds to a section of the casting core (G) to be produced, and wherein the casting core insert (E) carries at least one side surface section (SF1, SF2), which is equal to a corresponding section of the side surface of the casting core (G) to be produced; (b) positioning the casting core insert (E) in the mold cavity (8) of the core box (1) in a position in which the casting core insert (E) takes the place, with its side surface section (SF1, SF2), which the corresponding section of the side surface (S1, S2) of the casting core (G) takes in the finished, produced casting core (G), wherein the parting plane (T) of the core box (1) runs through the side surface section (SF1, SF2) of the casting core insert (E) positioned in the core box (1); (c) introducing a casting core molding material (F), which is mixed together from a basic molding material and a binder, as well as, optionally, from one or more additives, into the mold cavity (8) of the core box (1), so as to produce the remaining casting core (G), wherein the casting core molding material (F) that penetrates into the mold cavity (8) comes into contact with the casting core insert (E) that sits in the mold cavity (8); (d) solidifying the casting core molding material (F) that was introduced into the mold cavity (8), thereby forming a shape-fit and/or material-fit connection between the casting core molding material (F) that was introduced into the mold cavity (8) and the casting core insert (E).

2. The method according to claim 1, characterized in that the molding material from which the casting core insert (E) is formed differs from the casting core molding material (F) from which the remaining casting core (G) is formed.

3. The method according to claim 1, characterized in that the molding material from which the casting core insert (E) is formed is the same as the casting core molding material (F) from which the remaining casting core (G) is formed.

4. The method according to claim 1, characterized in that a surface structure having projections, recesses and/or undercuts is imparted to the casting core insert (E) during its production (work step (a)), on its surface sections that come into contact with the remaining casting core (G), on which sections shape-fit coupling of the casting core insert (E) with the casting core molding material (F) that comes into contact with it occurs when the casting core molding material (F) that was introduced into the core box (1) in work step (c) impacts the corresponding surface sections.

5. The method according to claim 1, characterized in that the volume of casting core molding material (F) that was introduced into the mold cavity (8) of the core box (1) in work step (c) is detected, and an alarm signal is issued if the volume introduced exceeds a limit value.

6. The method according to claim 1, characterized in that an additional molded element, such as a recess, a projection or a foreign body, is provided in the mold cavity (8), which element is shielded with regard to the remaining part of the mold cavity (8) after positioning of the casting core insert (work step (b)) in the mold cavity (8), by means of the casting core insert (E), that it is monitored whether a molded element is reproduced on the casting core (G) obtained after work step (d), which element corresponds, at least in certain sections, to a negative of the additional molded element provided in the mold cavity (8), and that in the event that such a molded element is found on the casting core (G) obtained, this casting core (G) is sorted out as a defective part.

7. The method according to claim 1, characterized in that the work steps (a)-(d) are carried out repeatedly in a serial sequence, and that the core box (1) comprises, in addition to the mold cavity (8) in which the casting core insert (E) is positioned in the one pass of the work step sequence (a)-(d) (work step (b)) and subsequently the casting core (G) to be produced is finish-formed by means of introduction of the casting core molding material (F) (work step (c)), an additional mold cavity (9) in which the new casting core insert (E′) is formed, at the same time when the casting core molding material (F) is filled into the mold cavity provided for the casting core (G) (work step (c)), which insert is required for the next pass to be carried out (work step (a) of the subsequent pass of the work steps (a)-(d)).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the following, the invention will be explained in greater detail using a drawing that shows an exemplary embodiment. The figures show, schematically, in each instance:

[0035] FIG. 1 a core box in the open position, in longitudinal section;

[0036] FIG. 2 a casting core insert in longitudinal section;

[0037] FIG. 3 the core box according to FIG. 1 in the open position, with a casting core insert according to FIG. 2 inserted into it, in a sectional representation corresponding to FIG. 1;

[0038] FIG. 4 the core box according to FIG. 3 in the closed position, in a sectional representation corresponding to FIG. 1;

[0039] FIG. 5 the core box according to FIG. 4 in the closed position, after casting core molding material has been shot in, in a sectional representation corresponding to FIG. 1;

[0040] FIG. 6 a casting core obtained after hardening of the casting core molding material and opening of the core box according to FIG. 5, in a sectional representation corresponding to FIG. 1;

[0041] FIG. 7 a casting core insert in a perspective view;

[0042] FIG. 8 a casting core in a perspective view corresponding to FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

[0043] For the production of a casting core G shown schematically in FIG. 6, in a sectional representation, and in greater detail in FIG. 8, a core box 1 is made available in a conventional core-shooter, not shown in any detail here, which box comprises an upper core box part 2 and a lower core box part 3.

[0044] In the upper and lower core boxes 1, recesses 4, 5, 6, 7 are formed, in each instance, of which the recess 4 of the upper core box part 2 and the recess 5 of the lower core box part 3 jointly form a mold cavity 8 when the core box 1 is closed (FIG. 4, 5), the shape of which cavity corresponds to a negative of the casting core G to be produced. The recess 6 of the upper core box part 2 and the recess 7 of the lower core box part 3, in contrast, form an additional mold cavity 9 when the core box 1 is closed, which cavity is independent of the first mold cavity 8 and represents a negative of a casting core insert E.

[0045] A separating join 10 runs between the core box parts 2, 3, which sit one on top of the other, in a parting plane T that extends horizontally here and intersects the mold cavities 8, 9. The separating join 10 opens, in each instance, into the mold cavities 8, 9.

[0046] Filling openings 11, 12, 13 are formed in the upper core box part 2, in a known manner. To fill casting core molding material F into the mold cavities 8, 9, shooting nozzles, not shown here, move into the filling openings 11-13 in a known manner, by way of which openings the casting core molding material F is shot in. Likewise in a known manner, ejectors, not shown here, are provided in the lower core box part 3, which eject the completed casting core G, in each instance, from the core box 1, which is then open.

[0047] For the casting core G, the provision applies that it is not allowed to have a casting core burr [typo previously mentioned] K on the side surfaces S1, S2 of a wall W that separates the recesses A1, A2 of the casting core G and is arranged in the interior of the casting core G, after unmolding from the core box 1, even if the recesses 4, 5 that mold the wall W on the casting core G to be produced are intersected by the parting plane T, so that the separating join 10 opens into the inner surfaces 14, 15 of the mold cavity 8 of the core box 1 that mold the side surfaces S1, S2 of the casting core G.

[0048] In order to fulfill this provision, a casting core insert E has been produced in the mold cavity 9 of the core box 1 in a separate work step. The shape of the mold cavity 9 corresponds to the shape of that section A of the mold cavity 8 in which the separating join 10 makes contact with the inner surfaces 14, 15 of the mold cavity 8, which surfaces reproduce the side surfaces S1, S2 on the casting core G. In this regard, the section A extends, proceeding from a thickened foot region, in the vertical direction, over about two-thirds of the height of the wall W of the casting core G to be produced, and in this regard covers the mouth region of the separating join 10.

[0049] In contrast to the section A of the mold cavity 8, however, the mold cavity 9 is oriented in such a manner that the parting plane T and, accordingly, the separating join 10 are oriented parallel to the inner surfaces 16, 17 of the mold cavity 9, which surfaces reproduce the flat side surface sections SF1, SF2 of the casting core insert E, which sections lie on opposite sides of the casting core insert E. The parting plane T and the separating join 10 therefore intersect the mold cavity 8, 9 not in the region of its inner surfaces 16, 17, which are oriented in the horizontal direction H here, but rather in the region of its narrow sides 18, 19, which extend in the vertical direction V.

[0050] To produce the casting core G, the casting core insert E is set into the recess 4 formed in the lower core box part 3, in section A of the core box 1, with its thickened foot (FIG. 3).

[0051] Subsequently, the upper core box part 2 is lowered until it sits tightly on the lower core box part 3 (FIG. 4). When the core box 1 is closed, the casting core insert E completely takes up the section A of the mold cavity 8, and lies tightly against the assigned inner surface 14, 15 of the mold cavity 9, in each instance, with its side surface sections SF1, SF2. In this regard, the side surface sections SF1, SF2 of the casting core insert E cover the mouth regions of the separating join 10, so that these are shielded with regard to the open remaining region 20 of the mold cavity 8, which was still free of molding material until then.

[0052] Subsequently, casting core molding material F is shot into the mold cavity 8 by means of the shooting nozzles already mentioned above, by way of the filling openings 11 and 12. The casting core molding material F fills the mold cavity 8 completely, and in this regard comes into contact with the narrow sides of the casting core insert E assigned to the open part of the mold cavity 8, so that after completion of the filling process, the casting core insert E is completely embedded in the casting core molding material F on its lateral narrows sides and at its top. At the same time that casting core molding material F is shot into the mold cavity 8, casting core molding material F is also shot into the mold cavity 9 for separate production of a new casting core insert E′, until this cavity is completely filled (FIG. 5).

[0053] Subsequently, the casting core molding material F filled into the mold cavities 8, 9 is hardened by means of heat application, moisture extraction or gassing, depending on the binder system used, in each instance. In this regard, a shape-fit connection is formed between the casting core insert E and the casting core molding material F that lies against it, by the grains of the casting core insert E that engage into one another on the side surfaces, and by the casting core molding material F that forms the remaining part of the casting core G that was not taken up by the casting core insert E. At the same time, at least locally, shape-fit connections form between the casting core molding material F of the casting core insert E and the casting core molding material F filled into the mold cavity 8, as the result of adhesion of the binder that is present in the casting core molding material F filled into the mold cavity 8, to the molding material grains of the casting core insert E. In this manner, in the finished, hardened casting core G, the casting core insert E is firmly integrated into the casting core G.

[0054] The transition regions U, at which the side surface sections SF1, SF2 make a transition into the adjacent side surface sections SF1, SF2 of the casting core G, are free of fissures or other uneven regions in this regard. Likewise, the side surface sections SF1, SF2 are completely burr-free, in accordance with the demands made on them. In contrast, a casting core burr K forms on the remaining surfaces not taken up by the side surface sections SF1, SF2 of the casting core insert E, where the separating join 10 opens into the mold cavity 8, in each instance.

[0055] The casting core insert E′ produced simultaneously with the casting core G is available for a further pass of the method described here, in which pass a further casting core G is produced, using the casting core insert E in question, which was pre-fabricated independently of it.

[0056] In the present example, the same commercially available casting core molding material F was used for the production of the casting core G and of the casting core insert E, which material was mixed together, in a known manner, from a molding sand, an organic or inorganic binder, and additives. Because of the completely independent production, however, a different molding material could also have been used for the production of the casting core insert E, for example so as to achieve a specific surface quality in the region of the side surface sections SF1, SF2.

REFERENCE SYMBOLS

[0057] 1 core box [0058] 2 upper core box part of the core box 1 [0059] 3 lower core box part of the core box 1 [0060] 4-7 recesses of the upper and lower core box part 2, 3 [0061] 8 first mold cavity of the core box 1 [0062] 9 additional mold cavity of the core box 1 [0063] 10 separating join of the core box 1 [0064] 11-13 filling opening of the upper core box part 2 [0065] 14, 15 inner surfaces of the mold cavity 8 [0066] 16, 17 inner surfaces of the mold cavity 9 [0067] 18, 19 narrow sides of the casting core insert E [0068] 20 free remaining region of the mold cavity [0069] A section of the of the mold cavity 8 taken up by the casting core insert E [0070] A1, A2 recesses of the casting core G [0071] E casting core insert [0072] E′ newly produced casting core insert [0073] H horizontal direction [0074] F casting core molding material [0075] G casting core [0076] K casting core burr [0077] S1, S2 side surfaces of the wall W of the casting core G [0078] SF1, SF2 side surface sections of the casting core insert E [0079] T parting plane of the core box 1 [0080] U transition regions U at which the side surface section SF1, SF2 make a transition into the adjacent side surface sections SF1, SF2 of the casting core G [0081] V vertical direction [0082] W wall of the casting core G