Molding line casting plant with 3D printer and process for the mass production of castings

Abstract

Mold casting system (100) for the series production of castings (300) using the sand casting process, with: - a mold manufacturing station (110) which includes a 3D printer (115) that produces mold segments (210) from loose molding sand (S); - a desanding station (120) in which the mold segments (210) produced with the 3D printer (115) are desanded; - a joining station (130) in which the desanded mold segments (210) are joined to form a mold strand (220) having casting cavities (230); and - a casting station (140) in which the casting cavities (230) are filled.

Description

[0001] The invention relates to a mold casting plant and a method for the mass production of castings using the sand casting process.

[0002] Castings, for example those made of aluminum, copper, cast iron, or steel, can be produced using the sand casting process. In this process, a mold or sand mold is created from a molding material, such as sand or casting sand. The cavity of this mold is then filled with molten metal using gravity. After the casting has solidified, the sand is removed, and the casting can be taken out. The mold is thus destroyed after a single use to remove the casting (the principle of the expendable mold). Because the sand casting process is particularly suitable for producing castings with complex geometries, including cavities and undercuts, and with varying material cross-sections, it is widely used.

[0003] To enable the economical production of larger quantities using the sand casting process, the so-called DISAMATIC process has been established for several decades. A DISAMATIC is a fully automated, boxless molding system (molding machine) for producing a vertically split, boxless mold strand. The DISAMATIC (registered trademark) molding machine has a molding chamber into which molding material is fed and then compacted into a mold block by a piston. The mold block is then ejected and pushed onto a belt conveyor, with the successively ejected mold blocks forming a progressively advancing mold strand, the casting cavities of which are filled in a subsequent casting station. Such a system can also be referred to as a mold strand casting system. For the prior art, reference is made, for example, to the corresponding Wikipedia entry and to patent specification DE 600 11 307 T2.

[0004] In addition, reference is made to patent DE 10 2006 017 922 A1, which describes a mold string for the serial casting of workpieces, the mold blocks of which are composed of several separate mold block parts.

[0005] Based on this state of the art, the invention aims to provide an improved mold casting system and a method for the mass production of castings that can be carried out with it.

[0006] This problem is solved by a system according to the invention as defined in claim 1 and by a method according to the dependent claim. Further developments and embodiments of the invention are described analogously for both subject matter of the invention in the dependent claims, the following description, and the figures.

[0007] The mold casting system according to the invention comprises: - a mold manufacturing station that includes (at least) a 3D printer that produces or can produce mold segments from loose molding sand (or similar molding material); - a desanding or unpacking station in which the mold segments produced in the 3D printer are or can be desanded; - a joining or merging station in which the desanded mold segments are or can be joined together to form a mold string containing casting cavities or voids; and - a casting station in which, in particular one after the other or in series, the casting cavities (of the mold strand) are or can be filled.

[0008] These stations are arranged along a feed direction of the mold segments or the mold strand in the specified sequence. Preferably, they are stationary installations.

[0009] Key features of the system according to the invention are the 3D printer and the desanding station, which is located downstream of the 3D printer in the feed direction. Devices and methods for 3D printing are known from the prior art, for example, German patent DE 10 2013 021 891 A1. Using the 3D printer, mold segments are additively produced in series from loose molding sand and, optionally, with the aid of a suitable binder, with the mold segments typically differing from one another. After completion, the mold segments produced by the 3D printer are still coated with loose molding sand or embedded in loose molding sand (sand or powder bed) and are subsequently desanded in the desanding station, whereby, in particular, the cavity surfaces are also freed from loose molding sand.The use of a 3D printer to manufacture the mold segments allows for a significantly greater variety of shapes and the creation of complex, intricate, and / or undercut casting cavities, especially compared to the DISAMATIC molding machine described above. Furthermore, mold segments with different designs can be produced in series.

[0010] Preferably, a continuously operating 3D printer is used. With a conventional 3D printer, the mold segments are produced in a discontinuous manufacturing process. With a continuously operating 3D printer, the mold segments are produced in a continuous or quasi-continuous manufacturing process, e.g., using the proven layer-by-layer build-up process, in which the layer-by-layer build-up process (layer-by-layer additive manufacturing) takes place, in particular, on a conveyor belt (the mold segments can be built up, e.g., using an inclined printing process, on a moving conveyor belt or the like). Devices and methods for continuous 3D printing are known from the prior art, for which reference is made, for example, to patents DE 10 2013 021 891 A1, EP 2 289 462 A1 and DE 10 2010 015 451 A1.

[0011] Advantageously, continuous 3D printing generates a continuous feed motion, which can then be used for the further feeding of the mold segments or the mold strand through the entire system. Instead of the discontinuous, stepwise feed as described in DE 600 11 307 T2, the system according to the invention can employ a continuous feed, which offers many advantages. Preferably, all components of the system according to the invention are designed accordingly. The system according to the invention can therefore also be described as a continuously operating mold strand casting system.

[0012] The desanding station of the system according to the invention can have at least one air blowing device with which the mold segments can be freed from loose molding sand on the outside and, in particular, also on the inside (i.e., the cavity surfaces) by blowing or expelling it. Preferably, this is a compressed air lance that can be inserted between adjacent mold segments.

[0013] The system according to the invention can further comprise a demolding station, which is arranged downstream of the casting station in the feed direction and in which the castings (after solidification of the molten metal) are released or removed from the molding sand by breaking the mold segments. The demolding or removal of the castings from the molds can be carried out, for example, by shaking, tapping, blowing, sonication, bombardment, and the like, for which the demolding station is appropriately designed. EP 2 301 692 A1 describes a suitable device and a suitable method for unpacking and removing sand from molded parts, which can be adapted for the invention.

[0014] The system according to the invention preferably includes a conveying device for feeding the mold segments or the resulting mold assembly. The conveying device comprises, for example, several belt conveyors (transport or conveyor belts) or the like. Preferably, the belt conveyors are permeable, at least in the area of ​​the sand removal station and / or demolding station, so that the loose or dissolved molding sand can trickle through. Preferably, the molding sand is then reused.

[0015] The system according to the invention preferably also includes a control device that enables fully automated system operation and, in particular, also monitors the proper operation of the system.

[0016] The inventive method for the series production of castings comprises the following processing steps, which are carried out at the relevant stations in a mold casting plant according to the invention: - generative or primary forming production of the mold segments with the aid of, or using, a 3D printer, especially a continuously operating one; - Sand removal from the mold segments; - Combining the sanded mold segments into a mold strand containing casting cavities; - Pouring the casting cavities with molten metal (e.g., with molten aluminum, cast iron, or steel); and - if necessary, demolding or removing the castings from the mold segments after the molten metal has solidified.

[0017] Series production, also known as serial production, refers to the consecutive manufacture of identical or dissimilar castings. The mold segments, continuously produced in the mold-making station using a 3D printer, can be transported by the conveyor system to the individual stations of the mold-making line casting system according to the invention. This transport preferably occurs in a continuous, and especially horizontal, feed motion, where the aforementioned steps are then carried out repeatedly or cyclically in the specified sequence.

[0018] Preferably, the mold segments are manufactured with a substantially vertical division. This means that the mold segments have essentially vertical end and back surfaces, which act as contact surfaces between adjacent mold segments in the mold assembly. The vertical division allows for easy joining or merging of the desanded mold segments, for example, by simply moving them together in a horizontal feed direction, causing them to butt against each other and form the mold assembly.

[0019] To ensure optimal sand removal, the mold segments can be moved apart. For this purpose, they are transferred, for example, at the 3D printer's outfeed, to a conveyor belt with a higher conveying speed (relative to the conveying or extrusion speed in the 3D printer) and thus move apart. On this conveyor belt, which is typically a permeable belt, the mold segments are then sanded. After sand removal, the mold segments are reassembled. To do this, they are transferred to another conveyor belt with a lower conveying speed, where they collide and form the mold strand. In other words, by being transferred to the slower conveyor belt, the mold segments are completely reassembled into the mold strand.

[0020] Cavities and / or undercuts in the castings to be produced can be created using cores that are manufactured separately and inserted into the respective casting cavities before the mold segments are joined (as described, for example, in DE 600 11 307 T2). However, the use of a 3D printer according to the invention makes it possible to directly form cores, or at least core sections, onto the respective cavity surfaces during the production of the mold segments. These core sections then form a core when the mold segments are joined. Thus, to create cavities and / or undercuts in the castings, cores or core sections can be formed or molded onto the inner surfaces of the respective mold segments during the 3D printing process. In other words, the cores or core sections are produced integrally with the respective mold segments. The cores or core sections are essentially printed along with the mold.This results in significant simplifications.

[0021] The joining of the sand-free mold segments can be monitored by a testing device. Furthermore, the mold segments can have corresponding interlocking elements, which allow the respective mold segments to center and / or align themselves during joining. These elements include, for example, pins or mandrels and corresponding recesses or bushings. Preferably, such corresponding interlocking elements are integrally formed or molded during the 3D printing of the respective mold segments, for example, on the vertical end and back surfaces, so that these interlocking elements consist of solidified molding sand. The interlocking elements are essentially printed along with the mold.

[0022] In 3D printing of mold segments, the molding sand is typically bonded through solidification. This solidification occurs, for example, through sintering processes and / or the curing of a binder. In layer-by-layer printing, after each layer is applied, one or more predetermined areas of the applied layer can be selectively solidified and bonded to the layer below using high-energy radiation. Similarly, the molding sand, applied repeatedly in thin layers, can be selectively printed with a binder material using a print head, causing the printed areas to bond and solidify. Regardless of the specific manufacturing method, 3D printing can produce mold segments that consist entirely of uniformly solidified molding sand.The mold segments can also be manufactured using 3D printing in such a way that the molding sand is only partially solidified and / or has varying degrees of solidification in different areas. The mold segments can thus be produced, for example, in a shell construction with shell surfaces of varying thickness and / or hardness (including internal support structures). This results in energy and environmental advantages, such as reduced binder and sand consumption due to improved recycling. Furthermore, this can also be used to selectively influence the solidification conditions for the castings to be produced, since solidified molding sand exhibits better thermal conductivity than less solidified or loose molding sand due to the bonding bridges. This allows for the creation of different thermal conductivity and insulation conditions within a single mold segment.

[0023] The invention enables the serial production of identical (i.e., shape-identical) or similar castings. However, it also allows for the serial production of different (i.e., shape-different) castings in virtually any sequence, provided they do not exceed a size limited by the machine's capacity. The shape of the mold segments can be modified almost arbitrarily without any machine-related lead time, thus allowing for individual adaptation to the castings to be produced successively.

[0024] The invention is explained in more detail below by way of example and in a non-limiting manner with reference to the single figure. The features shown in the figure and / or explained below can, even independently of specific combinations of features, be general features of the invention and further develop the invention.

[0025] Fig. Figure 1 shows a schematic side / sectional view of a mold extrusion casting system according to the invention for the series production of metallic castings or cast components.

[0026] The mold casting system 100 comprises a mold making station 110, a desanding station 120, a joining or assembling station 130, a casting station 140, and a demolding station 150. The individual stations are stationary. In the mold making station 110, mold segments or parts 210 are continuously produced from molding sand. These are then desanded in the desanding station 120 and joined in the joining station 130 to form a mold string 220 with casting cavities 230. The casting cavities 230 are filled with molten metal M in the casting station 140. After the molten metal M has solidified, the castings 300 are removed from the mold segments 210 or the mold strand 220 in the demolding station 150.

[0027] The system 100 also includes a conveying device for the continuous feed of the mold segments 210 or the mold assembly 220. This conveying device comprises several transport or conveyor belts 161, 162, 163 and 164. The horizontal feed movement and its speed are illustrated by arrows V1, V2 and V3.

[0028] The mold manufacturing station 110 features a continuously operating 3D printer 115, which individually produces the mold segments 210 according to specifications from a control unit. The mold segments 210 are produced layer by layer with vertical divisions 215, so that they essentially have vertical front and back surfaces. Several mold segments 210 essentially form a mold with a casting cavity 230. A casting cavity 230 is thus distributed across several adjacent mold segments 210 produced in the corresponding sequence, with each mold segment 210 having at least one casting cavity section. Each casting cavity 230 is vertically subdivided by at least one division 215. The production of the mold segments 210 using 3D printers also enables the integral or integrated formation of cores or core sections 235.

[0029] The production of the mold segments 210 using a 3D printer requires that they be cleaned of loose molding sand after completion. Loose molding sand S is also found in the joints of the vertical partitions 215 and in the casting cavities 230. By moving the mold segments 210 apart, each casting cavity 230 can be opened, cleaned of sand, and then closed for the casting process by moving the same mold segments 210 together. For this purpose, the mold segments 210 exiting the mold manufacturing station 110 are transferred from the associated conveyor belt 161 to the conveyor belt 162 belonging to the desanding station 120, which has a higher conveying or transport speed (i.e., V2 > V1). This moves the mold segments 210 apart, increasing the distance between them. The loose molding sand S can now trickle off.Furthermore, the cavity interior surfaces are blown off using lance-like air blowing devices (compressed air lances) 170. The mold segments 210, produced by continuous 3D printing, are then continuously desanded in the desanding station 120. The conveyor belt 162 is permeable, allowing the loose or dissolved molding sand S to trickle through it.

[0030] After sand removal, the sand-free mold segments 210 are transferred from conveyor belt 162 to a slower conveyor belt 163 with a lower conveying speed (i.e., V3 < V2), where they are then pushed or pushed together, abutting or colliding to form a seamless, boxless mold assembly 220. For centering and alignment, the mold segments 210 can be equipped with corresponding interlocking elements 211 and 212. The mold assembly 220 is then conveyed on the same conveyor belt 163 to the casting station 140, where the casting cavities 230 are successively filled. The casting process is therefore carried out using sand molding or sand casting.

[0031] After solidification and / or after reaching the demolding temperature, the castings 300 are demolded in the demolding station 150, whereby the molds or mold segments 210 are destroyed and the cores 235 are removed. The conveyor belt 164 belonging to the demolding station 150 is also permeable. The removed molding sand can be recycled and reused.

[0032] The system 100 enables the continuous production of mold segments 210 as well as the continuous desanding, merging, pouring, and demolding. The castings 300, which are primarily cast components for motor vehicles, can be produced with comparatively short lead times and minimal handling and transport effort. The illustration in the Fig. Figure 1 is only schematic and therefore not to scale or represent a specific number. The in Fig.The plant shown produces 300 identical or at least similar castings in series. In principle, however, different castings can also be produced in almost any sequence. This results in very high production flexibility, which offers considerable economic advantages, especially with regard to increasing small production runs and rising levels of individualization (vehicle customization). Reference symbol list 100 mold strand casting plant 110 mold making station 115 3D printers 120 desanding station 130 joining station 140 Watering station 150 demolding station 161 Conveyor belt 162 Conveyor belt 163 Conveyor belt 164 Conveyor belt 170 air blower 210 Mold segment 211 Positive locking element 212 Positive locking element 215 division 220 mold strand 230 Casting cavity 235 core 300 cast part M Metal melt S Molding sand V1 Feed movement / speed V2 Feed movement / speed V3 Feed movement / speed

Claims

[1] Mould strand casting plant (100) for the series production of castings (300) using the sand casting process, with: - a mold manufacturing station (110) having a 3D printer (115) that produces mold segments (210) from loose molding sand (S); - a desanding station (120) in which the mold segments (210) produced with the 3D printer (115) are desanded; - a joining station (130) in which the sand-removed casting mold segments (210) are combined to form a mold strand (220) having casting cavities (230); and - a casting station (140) in which the casting cavities (230) are poured. [2] Mould strand casting plant (100) according to claim 1, characterized by that it is a continuously operating 3D printer (115). [3] Mould strand casting plant (100) according to claim 1 or 2, characterized by that the desanding station (120) has at least one air blowing device (170). [4] Method for the series production of castings (300) with a mold strand casting plant (100) according to one of the preceding claims, comprising the steps: - producing the mold segments (210) using the 3D printer (115); - Desanding the mold segments (210); - merging the desanded casting mold segments (210) to form a mold strand (220) having casting cavities (230); - Pouring the casting cavities (230). [5] Method according to claim 4, characterized by that the mold segments (210) are produced with a substantially vertical division (215). [6] Method according to claim 4 or 5, characterized by , that the mold segments (210) are moved apart for desanding, for which purpose they are transferred to a conveyor belt (162) with a higher conveying speed (V2), and that the casting mold segments (210) are brought together after desanding, for which purpose they are transferred to another conveyor belt (163) with a lower conveying speed (V3), where they then collide and form the mold strand (220). [7] Method according to one of claims 4 to 6, characterized by that the mold segments (210) are manufactured with integrated cores or core sections (235). [8] Method according to one of claims 4 to 7, characterized by that the casting mold segments (210) are produced with corresponding form-locking elements (211, 212) via which centering and / or alignment takes place when brought together. [9] Method according to one of claims 4 to 8, characterized by that the molding sand (S) is only partially solidified and / or solidified differently in certain areas during the production of the mold segments (210). [10] Method according to one of claims 4 to 9, characterized bythat different castings (300) can be produced in series.

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