Method and device for producing a component by means of diecasting

Abstract

In a method for producing a component, in particular a vehicle wheel, by means of diecasting, liquid melt is fed to a mould cavity (3) via a casting chamber (5) arranged upstream of the mould cavity (3). During the feeding of the liquid melt, the mould cavity (3) is vented on a side facing away from the casting chamber (5) and, before the introduction of the liquid melt into the mould cavity (3), the mould cavity (3) is vented via the casting chamber (5).

Description

[0001] Method and device for producing a component by means of pressure casting

[0002] This application claims the priority of German patent application No. 10 2023 114 209.7 as well as the priority of German patent application No. 10 2023 135 039.0, the contents of which are incorporated herein by reference.

[0003] The invention relates to a method for producing a component, in particular a vehicle wheel, by die casting. Furthermore, the invention relates to a device for producing a component, in particular a vehicle wheel.

[0004] EP 3 645 192 B1 describes a method for producing 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 produced by pressurized casting, with the mold being heated to different temperatures in different areas.

[0005] The magazine "Gießerei 05 / 2018" describes a so-called "vacuum-dosed die casting process," which involves a filler neck through which the liquid melt is introduced into a mold cavity by means of a dosing unit. When the dosing process begins, the mold cavity is evacuated.

[0006] The problem with the solution described there is that the filler neck seal is subject to very high wear, which either requires frequent replacement or permanently impedes the casting process. Furthermore, during the evacuation of the mold cavity, liquid melt can be sucked out and enter the area of ​​the vacuum pump, which can lead to damage to the pump or disruption of the process being carried out. Therefore, the solution described there is not suitable, or at least only partially suitable, for series production.

[0007] The fundamental problem with die casting of larger components is that the mold should be as well evacuated as possible, i.e. there should be as little air as possible in the mold cavity to prevent air pockets in the component produced from the liquid melt. The same applies to the casting chamber upstream of the mold cavity. This can be very difficult, especially with large components such as vehicle wheels, because the high speed at which the melt is fed from the casting chamber into the mold cavity means there is very little time for the air to escape from the mold cavity or casting chamber. In addition, the remaining air in the casting chamber and mold cavity is exposed to oxygen from the atmosphere, which creates oxides both during metering and when filling the mold cavity.These oxides impair the strength properties of the component and increase the range of variation in the fatigue strength during open testing and ultimately also during operation. Therefore, the object of the present invention is to provide a method and a device for manufacturing a component, in particular a vehicle wheel, which, also due to the special design of the device, can be carried out with greater reliability, while keeping the range of variation in the fatigue strength of the component as small as possible.

[0008] According to the invention, this object is achieved by the features mentioned in claim 1.

[0009] In the method according to the invention for producing a component by means of die casting, liquid melt is fed into a mold cavity via a casting chamber located upstream of the mold cavity, preferably using a dosing bell. During the feeding of the liquid melt, the mold cavity is vented on a side facing away from the casting chamber. For this purpose, corresponding venting openings are located on this side of the mold cavity facing away from the casting chamber. In addition, according to the present invention, the mold cavity is vented via the casting chamber before the liquid melt is introduced into the mold cavity.

[0010] In particular, venting the mold cavity before introducing the melt into it via 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, and in particular with the oxygen contained therein, thereby reducing any potential impairment of the quality of the component produced using the method according to the invention. Ultimately, this results in a highly homogeneous component without air inclusions or the like, making the method according to the invention particularly well-suited for the production of a vehicle wheel with the specific requirements of rapid yet uniform filling of the mold cavity.

[0011] If the mold cavity and the casting chamber are not closed, when the casting piston passes over the metering opening of the casting chamber leading to the casting chamber, venting can take place via the vent openings on the side of the mold cavity facing away from the casting chamber. For this reason, this venting can only take place within a time of, for example, 0.75 - 1.5 seconds during the first phase of the casting process, i.e. while the filling level of the casting chamber is brought from, for example, 50% to 100%. As described above, according to the present invention, a large part of the mold cavity is also vented before the melt is introduced or introduced into the casting chamber. For this purpose, an additional period of, for example, a further 4 - 6 seconds is available in which the mold cavity is vented via the casting chamber before the liquid melt is introduced into the mold cavity.Because the liquid melt is only introduced into the casting chamber via the casting chamber after the mold cavity has been evacuated, this reliably prevents the liquid melt from being sucked out of the casting chamber. It is possible to continue venting or evacuating the mold cavity while the liquid melt is being introduced, since at this point a comparatively high negative pressure has already been reached and there is no longer any risk of the liquid melt being sucked in. This inventive venting or evacuation of the mold cavity via the casting chamber before the liquid melt is introduced into the casting chamber and into the mold cavity therefore allows a significantly longer period for uniform venting of the mold cavity, so that significantly more air can be removed from it.In combination with the venting on the side facing away from the casting chamber, this creates the opportunity to evacuate a large portion of the air present in the mold cavity at the start of the casting process and prevent the air from mixing with the melt. Combined with the lower proportion of oxygen in the remaining air, this minimizes oxide formation during the casting process.

[0012] In a very advantageous development of the invention, it can be provided that the mold cavity is brought to a pressure level of below 700 mbar, preferably below 300 mbar, by venting it before the liquid melt is introduced into the mold cavity via the casting chamber. Such venting of the mold cavity via the casting chamber, preferably in conjunction with the introduction of nitrogen and / or a noble gas into the mold cavity before the liquid melt is introduced into the mold cavity, ensures that only very little air or oxygen is present in the mold cavity before the melt enters it. Thus, ideal conditions are ensured within the mold cavity even before the liquid melt enters it.

[0013] Due to the described venting via the casting chamber and the resulting reduction in pressure in the mold cavity, it is possible, in a further advantageous embodiment of the invention, to bring the mold cavity to a pressure level of less than 100 mbar, preferably less than 80 mbar, by venting the same during the supply of the liquid melt on the side facing away from the casting chamber. Such a negative pressure within the mold cavity, caused or generated by the combination of the two venting processes described above, offers ideal conditions for producing a homogeneous component, in particular a vehicle wheel. The air still present in the mold cavity after the venting of the mold cavity via the casting chamber as the melt flows into the mold cavity can therefore be easily discharged via the vent opening on the side of the mold cavity facing away from the casting chamber.

[0014] In order to reduce the oxygen content within the mold cavity and thus prevent the risk of oxide formation within the melt, it can further be provided that nitrogen and / or a noble gas is introduced into the mold cavity before the dosing bell is docked to the casting chamber and the liquid melt is introduced to displace the oxygen present in the mold cavity. For example, using a probe attached for this purpose, this residual oxygen can be checked, monitored, and documented before docking. By flooding the mold cavity with nitrogen or a noble gas, it is possible to reduce the oxygen content in the casting chamber and in the mold cavity to below 1% before closing by the dosing bell.

[0015] For quality assurance purposes, it can be advantageous to store measured pressure values, measured values ​​of extracted volumes, and / or measured oxygen levels. If the pressure values ​​within the mold cavity, the extracted volume values, and the measured oxygen levels are saved as a backup, the target values ​​achieved can be monitored to ensure the quality of the cast components. A quality table with a uniquely assignable ID could be used for this purpose.

[0016] Claim 6 specifies a device for producing a component, in particular a vehicle wheel, by means of die casting.

[0017] The device comprises a casting mold with a mold cavity, a casting chamber upstream of the mold cavity, a dosing bell for introducing liquid melt into the casting chamber, and a filling funnel, which protrudes on one side when the liquid melt is introduced into the casting chamber and on the other side has an opening for introducing the dosing bell. At its opening, the filling funnel further comprises a sealing element that interacts with a cone of the dosing bell to seal the connection between the dosing bell and the introduction funnel, and thus between the dosing bell and the casting chamber. This can assist the above-described venting or evacuation of the mold cavity.

[0018] To prevent damage to the sealing element, the cone has a device for preventing the liquid melt from adhering undefinedly to the dosing bell. This device reliably prevents undefined adhesion of the liquid melt to the dosing bell and thus ensures that the melt either cannot come into contact with the sealing element of the feed funnel or that only such contact of the melt with the sealing element is possible that ensures a consistent transition area between the cone and the sealing element, thus always ensuring a seal between the cone and the sealing element. This significantly increases the service life of the sealing element, allowing the device according to the invention to be operated over a very long period of time and, in particular, in an economical manner.

[0019] In a very advantageous development of the invention, the device for preventing undefined adhesion of the liquid melt can be designed as a coating. Such a coating can be easily applied to the cone of the dosing bell and reliably ensures that no liquid melt adheres to the dosing bell.

[0020] A coating such as a sizing agent or a glaze has proven particularly suitable in practice, as this ensures very high abrasion resistance. However, in an advantageous further development of the invention, the device for preventing the undefined adhesion of the liquid melt is also possible in the form of a microstructure. Such a microstructure can be incorporated into the feed funnel in various ways and, according to the lotus effect, is capable of preventing the liquid melt from adhering to the dosing bell.

[0021] The microstructure can be designed particularly easily and very precisely if it is formed using a laser beam.

[0022] In order to ensure a reliable seal of the dosing bell on the insertion funnel, a further advantageous embodiment of the invention can provide a device for removing melt residues on the dosing bell.

[0023] The device for removing melt residues from the dosing bell can comprise a container with an opening for inserting the dosing bell, which container has several air nozzles in the area of ​​its opening. With such an embodiment, melt residues can be removed from the dosing bell by means of an air flow directed at the dosing bell.

[0024] In conjunction with the extended evacuation time and the above-described device for removing melt residues from the dosing bell, which can also be referred to as a blow-off device, excessive cooling of the melt should be avoided. A further advantageous embodiment of the device according to the invention can thus consist in a plunger for opening and closing a discharge opening for the liquid melt being arranged within the dosing bell, wherein the plunger has an internal cavity in which a heating element is arranged. In this way, adhesion of the cooling liquid melt to the plunger or the inner surfaces of the dosing bell and thus premature solidification of the melt can be prevented; this could occur if the plunger or the outer surfaces cooling due to the blow-off process have a significantly lower temperature than the liquid melt, which is prevented by the heating element.

[0025] A further device for producing a component, in particular a vehicle wheel, by means of die casting is disclosed in claim 14.

[0026] This, in turn, comprises a casting mold with a mold cavity, a casting chamber upstream of the mold cavity, a dosing bell for introducing liquid melt into the casting chamber, and an inlet funnel that protrudes into the casting chamber when the liquid melt is introduced into the casting chamber and itself has an opening for introducing the dosing bell. The inlet funnel further comprises an air outlet for extracting air from the mold cavity. A device for preventing the liquid melt from flowing out through the air outlet is arranged in the area upstream of the air outlet of the inlet funnel. The device according to the invention enables air to be extracted from the casting chamber and thus from the mold cavity, whereby the advantages described above with reference to the method with regard to the effective venting of the mold cavity and the resulting rapid and uniform filling thereof can be realized particularly easily.The device located in front of the air outlet prevents the melt from escaping through the air outlet. This, in turn, ensures that the entire amount of liquid melt reaches the mold cavity, thus guaranteeing a high-quality die-cast component.

[0027] In a very advantageous development of the device according to the invention, the device for preventing the outflow of the liquid melt can be designed in a labyrinthine manner. This prevents the liquid melt from flowing out through the air outlet in a particularly reliable manner.

[0028] In the following, embodiments of the invention are shown in principle with reference to the drawing.

[0029] It shows:

[0030] Fig. 1 shows a first embodiment of the device according to the invention;

[0031] Fig. 2 is an enlarged view of part of the device from Fig. 1;

[0032] Fig. 3 is a sectional view of Fig. 2;

[0033] Fig. 4 is a plan view of part of the device according to the invention;

[0034] Fig. 5 shows a further embodiment of the device according to the invention; and

[0035] Fig. 6 shows a further embodiment of the device according to the invention.

[0036] Fig. 1 shows a device 1 for producing a component not shown in the figures, in particular a vehicle wheel, by die casting. The basic structure of the device 1 or the die casting machine comprising the device 1 is known from EP 3 645 192 B1 and is therefore not described in detail here.

[0037] The device 1 has a casting 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 upstream of the mold cavity 3 by means of a dosing bell 4, made of ceramic, for example. To ensure that all of the melt reaches the casting chamber 5, the device 1 has an inlet funnel 6, which protrudes 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. To accommodate the dosing bell 4, the inlet funnel 6 has an opening 6a, which can be seen in Fig. 4. At its opening 6a, the inlet funnel 6 has a sealing element 7, which can also be seen in Fig. 4.

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

[0039] In order to make the area where the dosing bell 4 is inserted into the insertion funnel 6 as tight as possible, the dosing bell 4 has a cone 8 at its end designed for insertion into the insertion funnel 6, which is best seen in Figures 2 and 3. The cone 8 of the dosing bell 4 allows for a very simple seal between the dosing bell 4 and the sealing element 7 of the insertion funnel 6, since the cone 8 reliably seals against the sealing element 7 when sufficient pressure is applied. In this case, both the cone 8 of the dosing bell 4 and the sealing element 7 have a round cross-section.

[0040] The dosing bell 4 can be fed to the insertion funnel 6 via a handling device (not shown), such as a multi-axis robot. This can also ensure that the dosing bell 4 is pressed more firmly into the insertion funnel 6 to improve the seal in this transition area.

[0041] The cone 8 is provided with a device 9, shown in Fig. 3, for preventing the undefined adhesion of the liquid melt to the dosing bell 4. The device 9 for preventing the undefined adhesion of the liquid melt to the dosing bell 4 can, for example, be designed as a coating 9a, as shown schematically in Fig. 3. The coating 9a can, for example, be a sizing agent or a temperature-stable glaze, i.e. a glaze that does not allow the melt to adhere even at temperatures of up to 700°C. Alternatively or additionally, however, it is also possible for the device 9 for preventing the undefined adhesion of the liquid melt to the dosing bell 4 to be a microstructure. Such a microstructure can, for example, be formed on the surface of the dosing bell 4 by means of a laser beam.

[0042] Fig. 3 shows a further aspect of the device 1. The feed funnel 6, which serves to introduce the melt into the casting chamber 5, has an air outlet 10. Connected to the air outlet 10 is a device 11 for extracting air from the casting chamber 5 and thus from the mold cavity 3, which device comprises a vacuum pump or suction pump 11a.

[0043] In the area in front of the air outlet 10, a device 12 is arranged to prevent the liquid melt from flowing out through the air outlet 10. The device 12 for preventing the liquid melt from flowing out is preferably designed in a labyrinth-like manner. In the present case, the device 12 is formed by a sheet metal or similar element shaped in such a way that it represents an obstacle or resistance to any melt flowing along with the air sucked out of the mold cavity 3 by the arrow "B", so that the air, but not the melt, can leave the feed funnel 6 via the air outlet 10. The length of the device 12 and the resulting distance from the nearest wall of the area in front of the air outlet 10 can be adapted to the respective requirements.

[0044] Fig. 5 shows a device 15 for removing melt residues from the dosing bell 4. This device has a container 16 with an opening 17 for inserting the dosing bell 4, which has a plurality of air nozzles 18 in the region of its opening 17. To remove the melt residues, the dosing bell 4 is inserted through the opening 17 into the container 16. The air nozzles 18 directed at the dosing bell 4 are then actuated and any melt residues are removed from the dosing bell 4, thus ensuring the sealing of the dosing bell 4 with respect to the insertion funnel 6.

[0045] Furthermore, Fig. 5 shows a plunger 19, shown in dashed lines, which is arranged within the dosing bell 4 and serves to open and close a discharge opening 20 for the liquid melt. For this purpose, the plunger 19 is movable in its longitudinal direction.

[0046] Fig. 6 shows the plunger 19 in more detail. Accordingly, the plunger 19 has an internal cavity 21 in which a heating element 22 is arranged. The heating element 22 can be used to heat the plunger 19, thereby significantly reducing the likelihood of melt adhering to it.

[0047] The device 1 can be used to carry out a method for producing the component, in particular the vehicle wheel, by die casting, in which method liquid melt is fed into the mold cavity 3 via the casting chamber 5 located upstream of 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 the device 11 connected to the air outlet 10 for extracting air from the casting chamber 5 by means of negative pressure. Furthermore, during the method, while the liquid melt is being fed into the mold cavity, the mold cavity 3 is vented on a side facing away from the casting chamber 5 via a vent opening 13 indicated very schematically in Fig. 1.

[0048] By venting the mold cavity 3 before and, if necessary, also during the introduction of the liquid melt therein, the mold cavity 3 can be brought to a pressure level of less than 700 mbar, preferably less than 300 mbar. By subsequently venting the mold cavity 3 while the liquid melt is being fed in via the vent opening 13, the mold cavity 3 can be brought to a pressure level of less than 100 mbar, preferably less than 80 mbar. Accordingly, in the process, the air is sucked out of the mold cavity 3 via the casting chamber 5 before the melt is fed in. During this suction of the air before the melt is fed into the casting chamber 5, the casting chamber 5 is sealed by the dosing bell 4 bearing against the feed funnel 6.In combination with the suction of air from the mold cavity 3 on the side opposite the casting chamber 5 via the vent opening 13, very low pressures can be realized within the mold cavity 3.

[0049] The venting of the mold cavity 3 via the casting chamber 5 thus begins even before the melt is poured into the casting chamber 5 via the dosing bell 4. It ends as soon as a pouring piston 14, which presses the melt from the casting chamber 5 into the mold cavity 3, has moved in the direction designated by "x" over the opening 5a of the casting chamber 5, since from this point onward the pouring piston 14 closes the air outlet 10. From this point onward, the venting of the mold cavity 3 via the vent opening 13 begins or is supported.

[0050] Furthermore, prior to attaching the dosing bell 4 and introducing the liquid melt into the mold cavity 3, nitrogen and / or a noble gas, such as argon, can be introduced into the mold cavity 3. This can reduce the oxygen content within the mold cavity 3 and prevent the risk of oxidation of the melt. Preferably, the oxygen content within the mold cavity 3 can be reduced to below 2%, preferably below 1%.

[0051] The control of the opening and closing of the vent opening 13, which prevents the melt from flowing out of the mold cavity 3 via the vent opening 13, can be carried out in a manner known per se.

[0052] Venting via the vent openings 13 can take place within a time of, for example, 0.75 - 1.5 seconds during the movement of the casting piston 14. Venting of the mold cavity 3 via the casting chamber 5 during the dosing process can take place within a further 4 - 6 seconds. The total time required for venting the mold cavity 3 is therefore between 4.75 and 7.5 seconds, which is significantly longer than with known solutions.

Claims

Patent claims 1. Method for producing a component, in particular a vehicle wheel, by means of die casting, wherein liquid melt is supplied to a mold cavity (3) via a casting chamber (5) upstream of the mold cavity (3), wherein the mold cavity (3) is vented on a side facing away from the casting chamber (5) during the supply of the liquid melt, and wherein the mold cavity (3) is vented via the casting chamber (5) before the introduction of the liquid melt into the mold cavity (3).

2. Method according to claim 1, characterized in that the mold cavity (3) is brought to a pressure level of less than 300 mbar by venting it before the liquid melt is introduced into the mold cavity (3) via the casting chamber (5).

3. Method according to claim 2, characterized in that the mold cavity (3) is brought to a pressure level of less than 80 mbar by venting it during the supply of the liquid melt on the side facing away from the casting chamber (5).

4. Method according to claim 1, 2 or 3, characterized in that nitrogen and / or a noble gas is introduced into the mold cavity (3) before the liquid melt is introduced into the mold cavity (3).

5. Method according to one of claims 1 to 4, characterized in that measured pressure values, measured values ​​of extracted volumes and / or measured values ​​of oxygen contents are stored.

6. Device (1) for producing a component, in particular a vehicle wheel, by means of die casting, with a casting mold (2) having a mold cavity (3), with a casting chamber (5) upstream of the mold cavity (3), with a dosing bell (4) for introducing liquid melt into the casting chamber (5) and with an introduction funnel (6) which projects into the casting chamber (5) when the liquid melt is introduced into the casting chamber (5) and has an opening (6a) for introducing the dosing bell (4), wherein the introduction funnel (6) has a sealing element (7) at its opening (6a), wherein the dosing bell (4) has a cone (8) at its end designed for introduction into the introduction funnel (6), and wherein the cone (8) has a device (9) to prevent the undefined adhesion of the liquid melt to the dosing bell (4).

7. Device (1) according to claim 6, characterized in that the device (9) for preventing the undefined stopping of the liquid melt is designed as a coating (9a).

8. Device (1) according to claim 7, characterized in that the coating (9a) is a sizing or a glaze.

9. Device (1) according to claim 6, 7 or 8, characterized in that the device (9) for preventing the undefined stopping of the liquid melt is a microstructure.

10. Device (1) according to claim 9, characterized in that the microstructure is formed by means of a laser beam.

11. Device (1) according to one of claims 6 to 10, characterized by a device (15) for removing melt residues on the dosing bell (4).

12. Device (1) according to claim 11, characterized in that the device (15) for removing melt residues on the dosing bell (4) has a container (16) with an opening (17) for inserting the dosing bell (4), which has a plurality of air nozzles (18) in the region of its opening (17).

13. Device (1) according to one of claims 6 to 12, characterized in that a plunger (19) for opening and closing a dispensing opening (20) for the liquid melt is arranged within the dosing bell (4), the plunger (19) having an inner cavity (21) in which a heating element (22) is arranged.

14. Device (1) for producing a component, in particular a vehicle wheel, by means of pressure die casting, with a casting mold (2) having a mold cavity (3), with a casting chamber (5) arranged upstream of the mold cavity (3), with a dosing bell (4) for introducing liquid Melt into the casting chamber (5) and with an inlet funnel (6) which projects into the casting chamber (5) when the liquid melt is introduced into the casting chamber (5) and has an opening (6a) for introducing the dosing bell (4), wherein the inlet funnel (6) has an air outlet (10) for sucking air out of the casting chamber (5), and wherein in the area in front of the air outlet (10) a device (12) for preventing the liquid melt from flowing out through the Air outlet (10) is arranged.

15. Device (1) according to claim 14, characterized in that the device (12) for preventing the outflow of the liquid melt is designed in a labyrinthine manner.

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