Method and device for producing a component by means of die casting

Abstract

In a method for producing a component, in particular a vehicle wheel, by means of die casting, using a dosing bell (4), via an insertion funnel (6), molten metal is introduced into a casting chamber (5) upstream of a mold cavity (3) and from the casting chamber (5) into the mold cavity (3). Before and during the feeding of the liquid melt into the casting chamber (5), the mold cavity (3) is vented both on a side facing away from the casting chamber (5) and via the casting chamber (5) and the insertion funnel (6). The air pressure in the dosing bell (4) is reduced before the liquid melt is introduced into the casting chamber (5).

Description

[0001] Method and apparatus for manufacturing a component using pressure quenching

[0002] The present application claims priority from German patent application No. 102025 103862.7, the contents of which are incorporated herein in full by reference.

[0003] The invention relates to a method for manufacturing a component, in particular a vehicle wheel, by means of die casting. The invention further relates to a device for manufacturing a component, in particular a vehicle wheel.

[0004] A generic method and a generic device are known from WO2024 / 245987 A1.

[0005] EP 3645 192 B1 describes a method for manufacturing a vehicle wheel from a light metal material, in which the light metal material is introduced in liquid form into a mold cavity. The vehicle wheel is manufactured by pressurized casting, whereby the mold is heated to different temperatures in different areas.

[0006] The journal "Gießerei 05 / 2018" describes a so-called "vacuum-dosed die casting process" in which a filling nozzle is provided through which the liquid melt is introduced into a mold cavity by means of a dosing unit. The mold cavity is evacuated when the dosing process begins.

[0007] The problem with the solution described there is that during the strong evacuation of the mold cavity during dosing, liquid melt is drawn in and can enter the area of ​​the vacuum pump, which can lead to damage to the pump or disruption of the process carried out with it, which is why the solution described there is not suitable or at least only conditionally suitable for series production.

[0008] The fundamental problem with die casting larger components is that the mold should be evacuated as thoroughly as possible, meaning that as little air as possible should be present in the mold cavity to prevent air pockets in the component produced from the molten metal. The same applies to the injection chamber upstream of the mold cavity. This can be particularly difficult with large components, such as vehicle wheels, because the high velocity at which the molten metal is injected from the injection chamber into the mold cavity leaves very little time for the air to escape from the mold cavity or the injection chamber.

[0009] It is therefore an object of the present invention to provide a method and a device for manufacturing a component, in particular a vehicle wheel, with which even better casting results are achieved than with known solutions. According to the invention, this object is achieved by the features mentioned in claim 1.

[0010] In the inventive method for manufacturing a component, in particular a vehicle wheel, by die casting, liquid melt is introduced by means of a metering bell via an infeed funnel into a casting chamber located upstream of a mold cavity, and from the casting chamber into the mold cavity. The mold cavity is vented before and during the introduction of the liquid melt into the casting chamber both via one or more vent openings on a side facing away from the casting chamber and via the casting chamber and the infeed funnel. Before the liquid melt is introduced into the casting chamber, the air pressure in the metering bell is reduced.

[0011] According to the invention, the mold cavity is evacuated before the melt is metered into the mold cavity and the upstream casting chamber, so that less evacuation is required during metering and mold filling, and this can then be carried out with greater reliability. The inventive method also takes into account that the different pressure levels in the metering bell compared to the pressure levels in the casting chamber and the mold cavity do not lead to undefined or uncontrolled discharge, for example, by splashing of the melt, which could otherwise result in pre-solidification of the casting, rendering the method unsuitable for series production.

[0012] In particular, venting the mold cavity before introducing the melt via the casting chamber and the side facing away from the casting chamber ensures very rapid and effective venting of the mold cavity. This reduces the mixing of the liquid melt flowing into the mold cavity with air, thereby minimizing any potential impairment of the quality of the component produced by the inventive method. Ultimately, this results in a very homogeneous component with no or very few air inclusions or similar defects, making the inventive method particularly well-suited for the production of a vehicle wheel with the specific requirements of rapid yet uniform filling of the mold cavity.

[0013] By default, venting can occur via the vent openings on the side of the mold cavity facing away from the casting chamber during the first phase of the casting process within a time of, for example, 0.75 to 1.5 seconds. This means that venting can take place after the injection port has passed over the injection port and the filling level of the injection chamber has been increased from, for example, 50% to 100%. As described above, according to the present invention, venting also occurs before and during the metering of the liquid melt into the casting chamber and the mold cavity. This means that venting takes place after the metering bell has closed the injection port via the injection funnel.Evacuating before dosing eliminates the risk of molten metal being drawn in. This allows for very thorough evacuation, for example, via appropriately sized vents. Within 2-4 seconds, the mold cavity and casting chamber can be completely or partially vented before the liquid melt is dosed into the casting chamber. This process typically removes 80% of the air, achieving a pressure level of 300 mbar in the casting chamber and mold cavity. Therefore, only minimal additional evacuation is required during dosing and subsequent casting phases, specifically during the first and second stages. This further reduces the pressure to approximately 150 mbar.

[0014] This inventive venting of the mold cavity via the casting chamber prior to metering and subsequent introduction of the liquid melt into the mold cavity thus allows for a significantly longer venting period, enabling considerably more air to be removed without strong suction drawing in melt. In combination with venting on the side facing away from the casting chamber, suitable valve technology allows for controlled evacuation as soon as the mold cavity and the upstream casting chamber are closed, through a sealing concept between the metering bell and the feed funnel mounted above the casting chamber.The controlled profile allows for, for example, increased venting before dosing, then slightly less during dosing, and subsequently, more strongly again during the initial phase of the casting process as the casting piston moves towards the mold cavity. This allows the pressure to be adjusted to changes in pressure due to gas expansion, such as when the melt comes into contact with the lubricants, or to the degassing process that occurs when the melt is introduced into the significantly reduced pressure level in the casting chamber, or to the changing volume resulting from the piston's movement. This ensures that the residual air in the casting chamber is evacuated more evenly and smoothly, preventing it from mixing with the melt.

[0015] In a highly advantageous embodiment of the inventive method, the pressure in the metering bell above the melt can be reduced to a level below 700 mbar, preferably below 500 mbar. Additionally, it is possible to achieve a very low vacuum level of below 400 mbar, preferably below 300 mbar, in the mold cavity and the casting chamber by evacuating the system before metering. A smaller pressure differential compared to the pressure above the melt in the metering bell then prevents excessively rapid suction of the melt from the metering bell into the casting chamber during metering, which could, for example, cause uncontrolled splashing in the casting chamber and the mold cavity.For this reason, it is preferable to reduce the pressure above the melt in the metering bell to a slightly higher level, for example, using valve technology. This prevents an excessively high pressure differential between the pressure in the casting chamber and the mold cavity and the pressure in the metering bell above the melt, thus preventing excessively rapid suction and subsequent splashing. Through the described controlled venting from the moment the metering bell is closed on the feed hopper until the mold is filled, and the resulting reduction in pressure in the mold cavity, it is possible to reduce the pressure in the mold cavity to a level below 100 mbar by venting it during the feeding of the liquid melt on the side facing away from the casting chamber.This steadily decreasing vacuum also allows the molten metal to degasse during the filling of the casting chamber, and the additional gases produced are immediately extracted by lubricants, for example, and not bound in the component to be cast using the inventive method. After pre-evacuating the casting chamber and the mold cavity, the molten metal is metered into the casting chamber located upstream of the mold. Evacuation continues continuously, and after complete filling with molten metal, a fill level of, for example, 50% is reached in the chamber. Subsequently, the casting piston in the casting chamber pushes the molten metal towards the mold cavity, and the fill level steadily increases, with the aim that once a fill level of 100% is reached, the actual mold filling can begin. During this process, evacuation continues through all venting openings, ensuring defined extraction in all directions at all times.Such a multi-stage, adjusted, and stabilized, steadily decreasing vacuum, in conjunction with degassing of the melt and extraction of the gases generated during filling, enables a venting process through profiled valve technology. This process, in turn, provides ideal conditions for producing a homogeneous component, particularly a vehicle wheel. After the mold cavity has been vented, any remaining air can be easily removed as the melt flows into the cavity, primarily through the vent openings on the side of the mold cavity facing away from the casting chamber.

[0016] A further advantageous embodiment of the method according to the invention can consist of reducing the pressure in the casting chamber and in the mold cavity to a level below 300 mbar before the introduction of the liquid melt, reducing the pressure in the casting chamber and in the mold cavity to a level below 200 mbar during the introduction of the liquid melt, and reducing the pressure in the casting chamber and in the mold cavity to a level below 100 mbar during the filling of the mold cavity. The mold cavity is filled with the casting piston, which, by a corresponding movement, pushes the melt towards the mold cavity.

[0017] In a further highly advantageous embodiment of the method according to the invention, it can be provided that, after the mold cavity is closed, and before the mold cavity, the upstream casting chamber, and the feed hopper are sealed by the metering bell, the mold cavity is flooded with nitrogen or a noble gas, such as argon, through at least one vent opening located on the side facing away from the casting chamber, so that the oxygen content in both the mold cavity and the casting chamber is reduced to below 2%. This ensures that the melt has no opportunity to form oxides during the introduction of the melt into the casting chamber or during the casting process, since these oxides impair the component, particularly with regard to its operational strength.

[0018] Claim 5 specifies a device for manufacturing a component, in particular a vehicle wheel, by means of die casting.

[0019] This includes a mold with a mold cavity, a casting chamber located in front of the mold cavity, a metering bell for introducing liquid melt into the casting chamber, and respective valve devices for venting the mold cavity and the casting chamber.

[0020] The valve devices make it possible to carry out the above-described procedure for evacuating the mold cavity and the casting chamber in a very simple and reliable manner.

[0021] It is particularly advantageous if the valve devices are arranged in venting channels connected to the mold cavity and the casting chamber, since in this way the amount of extracted air can be controlled very easily by changing the cross-section of the respective venting channel, making it possible to carry out a very simple adapted evacuation or reduction of the pressure in the mold cavity and the casting chamber.

[0022] In order to be able to variably and controllably reduce the pressure level above the melt in the metering bell, so that no rapid uncontrolled suction occurs when the liquid melt is subsequently fed into the casting chamber, a valve device can be provided to reduce the pressure level above the melt in the metering bell.

[0023] Furthermore, with regard to simple control of the method according to the invention, it has proven advantageous if the valve devices are continuously controllable on the basis of a preset control profile.

[0024] Alternatively, the valve devices can be continuously controlled based on pressure measurements at the valve devices. This allows the process to be carried out with even greater precision.

[0025] Claim 10 specifies a further device for manufacturing a component, in particular a vehicle wheel, by means of die casting.

[0026] This has a mold having a mold cavity, a casting chamber located in front of the mold cavity and a metering bell for introducing liquid melt into the casting chamber, as well as at least one vent opening located on the side facing away from the casting chamber for flooding the mold cavity and the casting chamber with nitrogen or a noble gas, such as argon, before closing the mold cavity and the casting chamber by means of the metering bell.

[0027] This makes it possible to reduce the oxygen content in both the mold cavity and the casting chamber to below 2%, thus preventing the molten metal from forming oxides during the introduction of the melt into the casting chamber or during the casting process. This is highly advantageous, as oxides impair the component, particularly with regard to its operational strength.

[0028] Claim 11 specifies a further device for manufacturing a component, in particular a vehicle wheel, by means of die casting.

[0029] This includes a mold with a cavity, a casting chamber in front of the cavity, a metering bell for introducing liquid melt into the casting chamber, an insertion funnel for receiving the metering bell, and an air-cooled sealing device between the metering bell and the insertion funnel.

[0030] For this purpose, the dosing bell can have a flow cavity that uses air to cool the contact surface with the seal on the feed hopper. This cooling air makes it possible to increase the durability of the seal on the feed hopper, which is fixed to the casting chamber, and thus make it more suitable for series production.

[0031] The following are exemplary embodiments of the invention illustrated in principle with reference to the drawing.

[0032] It shows:

[0033] Fig. 1 shows a first embodiment of the device according to the invention;

[0034] Fig. 2 is an enlarged view of part of the device from Fig. 1;

[0035] Fig. 3 is a sectional view from Fig. 2;

[0036] Fig. 1 shows a device 1 for manufacturing a component not shown in the figures, in particular a vehicle wheel, by means of die casting. The basic design of the device 1 or of the die-casting machine comprising the device 1 is known from EP 3645 192 B1 and is therefore not described in detail here.

[0037] The device 1 has a mold 2, which in turn forms a mold cavity 3. The liquid melt used to form the component is introduced into the mold cavity 3 and solidifies there. For this purpose, the melt is introduced into a casting chamber 5 located upstream of the mold cavity 3 by means of a metering bell 4, for example made of ceramic. To ensure that all the melt reaches the casting chamber 5, the device 1 has a feed funnel 6, which projects into an opening 5a of the casting chamber 5 when the liquid melt is introduced. The melt flows into the casting chamber 5 according to arrow "A" in Fig. 3. The feed funnel 6 has an opening 6a, which can be seen in Fig. 3, to receive the metering bell 4. The feed funnel 6 has a sealing element 7 at its opening 6a, which can also be seen in Fig. 3.

[0038] The molten metal is a light metal suitable for the manufacture of vehicle wheels, in particular a suitable aluminum or magnesium alloy.

[0039] The dosing bell 4 can be fed to the feed hopper 6 via a handling device (not shown), for example a multi-axis robot. This can also ensure that the dosing bell 4 is pressed more firmly into the feed hopper 6.

[0040] Figure 3 shows another aspect of the device 1. The feed funnel 6, which serves to introduce the melt into the casting chamber 5, has an air outlet 8. A device 9 for extracting air from the casting chamber 5 and thus from the mold cavity 3 is connected to the air outlet 8. This device includes a vacuum pump 9a. This device 9 can be variably controlled and regulated by means of a valve assembly 10.

[0041] In the area in front of the air outlet 8, a device 11 is arranged to prevent the liquid melt from flowing out through the air outlet 8. The device 11 for preventing the flow of the liquid melt is preferably designed in a labyrinthine manner. In this case, the device 11 is formed by a sheet or similar material shaped in such a way that it presents an obstacle or resistance to any melt flowing along with the air drawn out of the mold cavity 3 by arrow "B", so that the air, but not the melt, can leave the inlet funnel 6 via the air outlet 8. The length of the device 11 and the resulting distance from the nearest wall of the area in front of the air outlet 8 can be adapted to the respective requirements.

[0042] The device 1 enables a method for manufacturing the component, in particular the vehicle wheel, by means of die casting, in which liquid melt is introduced via the metering bell 4 and the feed funnel 6 into the casting chamber 5, which is located upstream of the mold cavity 3, and from the casting chamber 5 into the mold cavity 3. In this method, before the melt is introduced into the mold cavity 3, the mold cavity 3 is vented via the casting chamber 5 by means of a vacuum extraction device 9 connected to the air outlet 8. Furthermore, in this method, both before and during the introduction of the liquid melt into the mold cavity, the mold cavity 3 is vented on a side facing away from the casting chamber 5 via a vent opening 12, which is shown very schematically in Fig. 1. This vent opening 12 can be variably controlled and regulated by means of a further valve device 13.Preferably, several vent openings 12 and associated valve devices 13 are provided. By venting the mold cavity 3 before introducing the liquid melt, the mold cavity 3 can be brought to a pressure level below 300 mbar. Simultaneously, the pressure level above the melt in the metering bell 4 is variably and controllably reduced by means of another valve device 14, so that no rapid, uncontrolled siphoning occurs when the liquid melt is subsequently fed into the casting chamber 5. During the introduction of the liquid melt, the pressure in the casting chamber 5 and in the mold cavity 3 is preferably brought to a level below 200 mbar. Additionally, the mold cavity 3 can be brought to a pressure level below 100 mbar during filling via the air outlet 8 or the device 9 and the vent opening 12.Accordingly, in this process, air is extracted from the mold cavity 3 via the casting chamber 5 both before and during the feeding of the melt. In combination with the extraction of air from the mold cavity 3 on the side opposite the casting chamber 5 via the vent opening 12, very low pressures can be achieved within the mold cavity 3.

[0043] The venting of the mold cavity 3 via the pouring chamber 5, in combination with the vent opening 12 located on the side facing away from the pouring chamber 5, begins even before the melt is poured into the pouring chamber 5 via the metering bell 4. The venting via the pouring chamber 5, in conjunction with the feed funnel 6, ends as soon as a pouring piston 15, which forces the melt from the pouring chamber 5 into the mold cavity 3, has passed through the opening 5a of the pouring chamber 5 in the direction designated "Y", since from this point on the pouring piston 15 is connected to the ambient pressure. From this point on, variable venting via the valve assembly 10 is no longer possible. Only variable venting of the mold cavity 3 via the vent opening 12 and the attached valve assembly 13 is possible from this point onward.

[0044] The casting chamber 5 and the cavity or mold cavity 3 are evacuated via valves 10 and 13 before the melt is metered. This evacuation can be carried out for, for example, four seconds. During metering to a fill level of, for example, 50% in the casting chamber 5, evacuation continues for another four seconds via valves 10 and 13. While the casting piston 15 slowly moves forward in the Y direction, evacuation continues via valves 10 and 13. As soon as the fill level of the casting chamber 5 reaches 100%, for example, after another 1.5 seconds, evacuation is carried out only via valves 13 assigned to mold cavity 3, for example, for a duration of 0.2 seconds. From this point on, valve 10 assigned to the casting chamber 5 no longer functions.

[0045] The opening and closing of the vent 12, which prevents the melt from flowing out of the mold cavity 3 via the vent 12, can be controlled in a manner known per se. Venting via the vent 12 can begin after the metering bell 4 has closed the feed hopper 6 and ends after the melt has filled the mold cavity 3. Venting can be variably controlled via the valve assembly 13 throughout the entire period before the melt is introduced, then during the metering of the melt from the metering bell 4 into the casting chamber 5, and subsequently during the casting process.

[0046] The valve devices 10 and 13 for venting the mold cavity 3 and the casting chamber 5 are arranged in respective venting channels connected to the mold cavity 3 and the casting chamber 5.

[0047] The valve assemblies 10, 13, and 14 can be continuously controlled based on a preset control profile, or they can be continuously regulated based on pressure measurements at the valve assemblies 10, 13, and 14. For example, the valve assemblies 10, 13, and 14 can be designed as proportional valves. However, this is not mandatory, and other options exist regarding the design of the valve assemblies 10, 13, and 14.

[0048] An air-cooled sealing device (not shown) may be provided between the metering bell 4 and the insertion funnel 6.

Claims

Patent claims 1. Method for manufacturing a component, in particular a vehicle wheel, by means of die casting, wherein liquid melt is introduced by means of a metering bell (4) via an introduction funnel (6) into a casting chamber (5) located upstream of a mold cavity (3) and from the casting chamber (5) into the mold cavity (3), wherein the mold cavity (3) is vented before and during the feeding of the liquid melt into the casting chamber (5) both on a side facing away from the casting chamber (5) and via the casting chamber (5) and the introduction funnel (6), and wherein the air pressure in the metering bell (4) is reduced before the introduction of the liquid melt into the casting chamber (5).

2. Method according to claim 1 , characterized by the fact that the pressure in the metering bell (4) above the melt is brought to a level below 700 mbar, preferably below 500 mbar.

3. Method according to claim 1 or 2, characterized by the fact that the pressure in the casting chamber (5) and in the mold cavity (3) is reduced to a level below 300 mbar before the introduction of the liquid melt, the pressure in the casting chamber (5) and in the mold cavity (3) is reduced to a level below 200 mbar during the introduction of the liquid melt, and the pressure in the casting chamber (5) and in the mold cavity (3) is reduced to a level below 100 mbar during the filling of the mold cavity (3).

4. Method according to claim 1, 2 or 3, characterized by the fact that After the mold cavity (3) has been closed, before the mold cavity (3), the upstream casting chamber (5) and the feed hopper (6) are closed by the metering bell (4), the mold cavity (3) is flooded with nitrogen or a noble gas, such as argon, through at least one vent opening (12) located on the side facing away from the casting chamber (5), so that the oxygen content in both the mold cavity (3) and the casting chamber (5) is reduced to below 2%.

5. Device for manufacturing a component, in particular a vehicle wheel, by means of die casting, comprising a mold (2) having a mold cavity (3), a casting chamber (5) located upstream of the mold cavity (3) and a metering bell (4) for introducing liquid melt into the casting chamber (5), characterized by respective valve devices (10,13) for venting the mold cavity (3) and the casting chamber (5).

6. Device according to claim 5, characterized by the fact that the valve devices (10,13) are arranged in vent channels connected to the mold cavity (3) and the casting chamber (5).

7. Device according to claim 5 or 6, characterized by a valve device (14) for reducing the pressure level above the melt in the metering bell (4).

8. Device according to claim 5, 6 or 7, characterized by the fact that the valve devices (10,13,14) are infinitely controllable on the basis of a preset control profile.

9. Device according to claim 5, 6 or 7, characterized by the fact that the valve devices (10,13,14) are continuously adjustable based on measurements of the pressure at the valve devices (10,13,14).

10. Device for manufacturing a component, in particular a vehicle wheel, by means of die casting, comprising a mold (2) having a mold cavity (3), a casting chamber (5) located upstream of the mold cavity (3), a metering bell (4) for introducing liquid melt into the casting chamber (5) and an introduction funnel (6) for receiving the metering bell (4), characterized by at least one vent opening (12) located on the side facing away from the casting chamber (5) for flooding the mold cavity (3) and the casting chamber (5) with nitrogen or a noble gas, such as argon, before closing the mold cavity (3) and the casting chamber (5) by means of the metering bell (4).

11. Device for manufacturing a component, in particular a vehicle wheel, by means of die casting, comprising a mold (2) having a mold cavity (3), a casting chamber (5) located upstream of the mold cavity (3), a metering bell (4) for introducing liquid melt into the casting chamber (5) and an introduction funnel (6) for receiving the metering bell (4), characterized by an air-cooled sealing device between the metering bell (4) and the insertion funnel (6).

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