Patent Application
20250091121
This document claims priority to German Patent Application No. 10 2023 124 831.6 filed on Sep. 14, 2023, the disclosure of which is incorporated herein by reference.
This disclosure relates to a casting device for a vacuum-assisted pressure die casting system, a vacuum-assisted pressure die casting system comprising the casting device, and a method for operating the vacuum-assisted pressure die casting system.
The state of the art knows vacuum-assisted pressure die casting systems in which a melt is introduced into a pressure die casting tool having a cavity using pressure by means of a casting chamber operated with a plunger, the gas present in the pressure die casting tool being evacuated from the pressure die casting tool at the same time at an end of the pressure die casting tool opposite the introduction of the melt by means of an underpressure system. This prevents air from being trapped in the pressure die casting tool, allowing work pieces of a particularly high quality to be produced.
A further source of air inclusions is the gap between the plunger and the casting chamber, which cannot be prevented due to the high thermal load. The vacuum in the cavity draws gas from the environment, referred to as false air, through the gap, which can cause the melt in the casting chamber to foam. In order to prevent the inclusion of gas in the melt, it is known from DE 20 2010 006 752 U1 for the back of the plunger to be sealed with a special seal. Also, it is known for the casting chamber to be evacuated using an underpressure system. The evacuation device is disposed at a rear part of the casting chamber. Therefore, suctioning of the false air which supports the seal cannot take place until the plunger passes the suction device. Hence, this is of secondary importance for preventing the entry of false air.
DE 10 2010 046 041 A1 teaches suctioning false air off through a gap in the plunger so that it does not reach the casting chamber. Suctioning takes place through a groove disposed in the rear part of the plunger. Hence, the complete and effective prevention of the entry of false air by suction cannot begin before the groove in the plunger has passed the filling hole. Until this point, the false air can enter the casting chamber via the filling hole.
Document DE 11 2019 003 928 T5 discloses suctioning the false air off through a groove disposed in the longitudinal direction at the top of the casting chamber while the plunger is moving. At the same time, the casting chamber is evacuated by design. However, this can cause swirling in the casting chamber, which also causes the melt to foam.
A disadvantage of the state of the art is that the sole suctioning of the false air can only take place at a late stage, which means an air inclusion in the melt, which weakens the subsequent work piece, may have already formed at this point in time. In addition, in the case of the evacuation device located in the rear part of the casting chamber, the evacuation opening may have to be closed as soon as the plunger starts to move, as melt could be pressed into it otherwise. This means that it cannot prevent the ingress of false air. This problem also exists in the version with the groove aligned in the longitudinal direction relative to the plunger. If the melt solidifies in the groove, the suction device is at least partially blocked, making it difficult to reuse the casting chamber.
Hence, there is a great need for a reliable, reusable and easy-to-clean casting device with a casting chamber that can effectively prevent the inclusion of gas in the melt, in particular through the ingress of false air, in order to produce high-quality work pieces and/or ensure the quality of the work pieces to be produced. At the same time, it should be possible to quickly fill the casting device and the casting chamber with melt and process the melt in a simple and reliable manner. In addition, the casting device with a casting chamber should be inexpensive to produce, durable and individually adaptable to the work piece to be produced. Hence, the object of the invention is to provide a casting device comprising a casting chamber with the intention to overcome the difficulties mentioned above.
This object is attained in a surprisingly simple yet effective manner by a casting device comprising a casting chamber, a vacuum-assisted pressure die casting system comprising at least one casting device, and a method for operating a vacuum-assisted pressure die casting system according to this disclosure.
In accordance with this disclosure, a casting device for a vacuum-assisted pressure die casting system is proposed, the casting device comprising a casting chamber having a wall surface and a plunger configured to move longitudinally into the casting chamber and completing the casting chamber at a first end, the casting chamber comprising a filling hole at the first end, preferably in the wall surface of the casting chamber, and the casting chamber comprising a gate at a second end opposite the first end, preferably on an end face. The casting device is characterized in that at least one suction groove is disposed tangentially in the inner side of the wall surface, at least in sections, at least one suction hole being disposed in the suction groove.
The principal idea is that the tangentially disposed suction groove can be used to start suctioning off the false air, which flows along the sides of the plunger and is caused by the evacuation of the cavity, as soon as the front end of the plunger has passed it completely. The tangential configuration means that this happens early on, so the suctioning can be started comparatively early. Swirling in the casting chamber is precluded, as the gas trapped in the casting chamber escapes through the suction groove to a small extent only. This effectively prevents the melt from foaming as a result of the false air and/or swirling. This significantly improves the quality of the work pieces to be produced. It has also been recognized in the context of the invention that, due to the tangential configuration of the groove, no melt or only small amounts of melt are pressed into the groove, and if this happens, it does so at low pressure, as the plunger closes the groove after a short distance. After the plunger has passed the groove, any melt that may have remained in the groove can be easily discharged sideways and can be removed from the casting chamber.
The casting chamber with the wall surface serves to receive the melt to be introduced into a pressure die casting tool. Preferably, the casting chamber is essentially cylindrical, but any shape of a hollow extrusion body is possible. In order to be able to introduce the melt received from the casting chamber into the pressure die casting tool by means of pressure, the casting device further comprises a plunger. The plunger can be moved from a first end of the casting chamber to a second end of the casting chamber. The first and second ends of the casting chamber complete the casting chamber in the extrusion direction, i.e., at the end faces. For this purpose, the peripheral geometry of the plunger is adapted to the interior of the casting chamber, although a small gap between the casting chamber and the plunger cannot be avoided due to the thermal load on the casting chamber. When the melt is filled into the casting chamber, the plunger is located in a first position at the first end of the casting chamber and closes it at this end. In other words, the melt is confined by an end face of the plunger facing the casting chamber. To introduce the melt into the pressure die casting tool by means of pressure, the plunger is moved from the first end to the second end of the casting chamber. In the process, the plunger exerts the necessary pressure on the melt to force it through the gate located at the second end. The gate is preferably located frontally at the second end so that the majority of the melt, preferably the entire melt, can be easily discharged from the casting chamber. This means pressure is exerted on the melt by the movement of the plunger, causing the melt to be introduced from the casting chamber into the pressure die casting tool through the gate. In order to introduce the melt into the casting chamber, the latter comprises a filling hole.
Before the melt is poured in, the casting chamber is filled with a gas, usually air. This gas should be removed from the casting chamber, preferably completely, before and/or while the melt is being introduced into the pressure die casting tool by means of pressure. At the same time, swirling of the gas and/or entry of gas from the environment should be prevented as far as possible during pouring and/or gating by means of pressure through the gate, as this can cause small gas inclusions in the melt, which can weaken the work piece to be produced. Swirling of the gas in the casting chamber can be prevented by the evacuation of the gas through the pressure die casting tool, which has already begun during pouring. The gas already has a predetermined direction of flow. Another source of air inclusions in the melt is gas from the environment, known as false air, flowing along the sides of the plunger when the plunger has covered or passed the filling hole. To prevent the occurrence of false air, the invention provides for at least one suction groove to be formed in the inner side of the wall surface of the casting chamber, at least in sections, with at least one suction hole. Preferably, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 suction grooves of the same or different design are disposed in the inner side of the wall surface, at least in sections. Furthermore, preferably at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 suction holes of the same or different design are disposed in the suction groove(s). The suction holes can be disposed in the suction groove(s) in a regular or irregular pattern. If at least two suction grooves are disposed in the wall surface, it is possible for the suction holes to be distributed evenly or unevenly across the suction grooves. The suction hole is an opening that starts at the bottom and/or the floor of the suction groove and ends at the outer side of the wall surface. The suction hole allows the false air flowing along the sides of the plunger to be suctioned off as the plunger moves past it. The suction groove preferably has a width of between 4 mm and 12 mm, more preferably between 5 mm and 11 mm, even more preferably between 6 mm and 10 mm, most preferably between 7 mm and 9 mm, in particular 8 mm.
In the context of the disclosure, the suction groove is disposed tangentially in the inner side of the wall surface. The tangential orientation allows the plunger to close the suction groove at an early stage. As soon as the plunger closes the suction groove, the suctioning of the false air caused by the evacuation of the cavity is possible without swirling occurring in the gas present in the casting chamber. In the context of the invention, the term “to close” means that the plunger is located in front of the suction groove, thus sealing it. It is understood that the seal must not be 100% airtight, as otherwise suctioning and/or evacuation would not be possible, as described elsewhere. The false air occurs as long as a gas flow through the casting chamber is possible. This means that as soon as the melt completely or almost completely fills the casting chamber, no more false air can occur. This happens while the plunger is moving from the first end to the second end. This reduces the volume of the casting chamber. As soon as this state occurs, suctioning of the false air is no longer necessary. The terms “longitudinal”, “longitudinally” and “longitudinal direction” refer to an orientation along the axis of the chamber. The terms “tangential”, “tangentially” and “tangential orientation” refer to an orientation in a circumferential direction of the chamber. It spans a plane that is orthogonal to the axis. The invention makes it possible to provide a casting device that is durable while also effectively preventing gas inclusions in the melt when pressure is built up and as soon as during the pouring of the melt into the casting chamber, thus significantly improving the quality of the cast parts to be produced. Moreover, the casting chamber can be filled faster and more effectively with a higher throughput, which contributes to a significant reduction in costs.
In a preferred embodiment of the invention, the suction groove is disposed behind the filling hole. By arranging the suction groove behind the filling hole, it is possible to start the extraction of the false air at the earliest possible time and to maintain it for as long as possible. False air only occurs when the plunger covers or has already passed the filling hole. Before the plunger closes the filling hole, the gas flows from the environment around the casting chamber through the filling hole into the casting chamber since the flow resistance is significantly lower here compared to the gap between the plunger and the casting chamber wall, through which the false air flows. As described elsewhere, the suctioning should be maintained as long as possible until the melt completely fills the decreasing volume of the casting chamber. Furthermore, the problem of the extraction of the false air failing because it enters the casting chamber through the filling hole and causes swirling in the casting chamber does not exist when the suction groove is disposed behind the filling hole. Although swirling can occur due to partial aspiration of ambient gas through the filling hole towards the suction groove, the plunger is already completely in front of the filling hole at this point. Hence, the swirling occurs in the area of the plunger and not in the area of the melt. The term “behind” refers to a reference direction in the longitudinal direction, viewed from the first end of the casting chamber.
An underpressure system and/or a vacuum pump can be connected to the suction hole. Using the underpressure system and/or the vacuum pump, suctioning through the suction groove can take place in a simple but effective manner. In this manner gas inclusions in the melt caused by false air flowing in can be prevented as far as possible. This increases the quality of the work pieces to be produced. The underpressure system and/or the vacuum pump can be operated until the plunger has completely passed the suction groove. It is conceivable for the same underpressure system and/or vacuum pump to evacuate the pressure die casting tool and bring about the extraction of the false air at the suction groove, or for a second underpressure system and/or vacuum pump to be provided for evacuating the casting tool. Furthermore, it is conceivable that if more than one suction hole is disposed in the wall surface, all suction holes are connected to an underpressure system and/or a vacuum pump. Preferably, it is conceivable that a first suction hole or a first portion of the suction holes is connected to a first underpressure system and/or vacuum pump and a second suction hole or a second portion of the suction holes is connected to a second underpressure system and/or vacuum pump. Further preferably, the casting device comprises a regulating and/or control device for the targeted extraction of the false air through the suction holes in one or more suction grooves and/or for the targeted evacuation of the pressure from the pressure die casting tool.
In an embodiment of the invention, the suction groove can extend in part of the wall surface, preferably between 10° and 120°, particularly preferably 90°. It has been recognized in the context of the invention that if the suction groove is not disposed circumferentially all around, but is only provided in the upper side of the wall surface, melt that has been introduced into the suction groove during the movement of the plunger can subsequently flow out of the suction groove at the sides and/or the melt does not fill the volume of the casting chamber to such an extent that the melt reaches the suction groove before the plunger covers the suction groove. The angle across which the suction groove extends should not be too small, as otherwise the surface tension of the melt prevents it from flowing out and/or the false air extraction does not take place completely and instead part of the false air passes the suction groove in the lower area and enters the casting chamber. However, it should not be too large, as otherwise the melt can accumulate at the groove end faces due to gravity and/or the entry of melt cannot be prevented. The groove preferably extends across an angle of at least 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 85°, 90°, 95°, 100°, 105°, 110° or 115°. Even more preferably, the groove extends across an angle of no more than 115°, 110°, 105°, 100°, 95°, 90°, 85°, 80°, 75°, 70°, 65°, 60°, 55°, 50°, 45°, 40°, 35°, 30°, 25°, 20° or 15°.
In an embodiment, the suction groove may flatten out at the end faces and thus have at least one flattened portion, preferably two flattened portions. This can prevent the accumulation of melt in the edge areas of the suction groove. The melt is drawn out of the groove under the influence of gravity. In addition, any false air can be specifically suctioned off in the edge areas.
In a preferred embodiment, the filling hole is disposed in the wall surface in a third of the wall surface adjacent to the first end. In a particularly preferred embodiment, the filling hole is disposed in the wall surface so close to the first end that the end face of the plunger is adjacent to a front edge of the filling hole when the plunger is in the position at the first end. When the filling hole is positioned in this manner, the plunger closes the filling hole early on when moving from the first end to the second end, so the gas surrounding the casting chamber can enter the casting chamber through the filling hole to a limited extent only and the pressure die casting tool can be evacuated very effectively. In a further embodiment, it is conceivable that the suction groove is disposed in a first third of a section of the wall surface, the section extending from a rear edge of the filling hole to the second end of the casting chamber. The suction groove is preferably disposed at a maximum distance of 20 mm from the rear edge of the filling hole, particularly preferably at a maximum distance of 19 mm, 18 mm, 17 mm, 16 mm, 15 mm, 1 4 mm, 13 mm, 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, 7 mm, 6 mm or 5 mm from the rear edge of the filling hole. In a particularly preferred embodiment, the suction groove is disposed directly behind the filling hole, the term “directly behind” referring to the most minimum distance from the rear edge of the filling hole in terms of safety. In this manner, the above-mentioned and preferred effect that the extraction of the false air can take place at an early stage and can be maintained for as long as possible can be exploited particularly well. This is the case in particular if the filling hole is disposed directly at the first end, as described elsewhere.
Furthermore, the diameter of the filling hole may increase from an inner side to an outer side of the wall surface and the suction groove may at least partially extend below the filling hole. In this manner, the suction groove can be brought closer to the edge of the filling hole in terms of manufacturing technology. In doing so, the advantages described elsewhere are achieved. In addition, the filling hole forms a funnel, which makes it easier to pour in the melt.
In a further development of the invention, the suction groove may have a rectangular cross section. A rectangular cross section is easy to produce from a manufacturing point of view. In particular, the at least one suction hole can be easily placed at the bottom of the rectangular cross section.
Moreover, the suction groove and/or the suction hole may be disposed at a top of the casting chamber. The gas present in the casting chamber is less dense than the melt under normal conditions, so the gas is displaced toward the top of the casting chamber by the melt when the melt is poured in. The top-side placement is particularly expedient if the top is formed by a section of the wall surface. In other words, the plunger is moved in the casting chamber essentially horizontally. False air occurs in particular in the area of the plunger that is not covered by melt at the end face.
In another embodiment, the casting device may comprise two to ten suction grooves, the suction grooves being disposed one behind the other in the longitudinal direction. The suction time can be extended by selectively controlling the suctioning through the individual suction grooves. In this case, suctioning takes place at the individual suction grooves as long as they are covered by the plunger. This means that even with short plungers, the extraction of the false air can continue until the melt completely fills the volume of the casting chamber, which is being reduced by the movement.
In a particularly preferred embodiment, the suction grooves are disposed at a distance from one another, the distance between adjacent suction grooves being smaller than a length of the plunger, in particular equal to the length of the plunger minus the widths of the adjacent suction grooves. This configuration enables the suctioning to be maintained continuously.
It is understood that the definitions and/or the explanations of the terms used above apply to all aspects described in this description and below, unless otherwise stated. It is understood that the explanations made in connection with the method and/or for the further device refer in an equivalent manner, albeit not in the same wording, to the casting device according to the invention and vice versa.
Furthermore, the invention proposes a vacuum-assisted pressure die casting system comprising at least one casting device as described elsewhere, a drive for driving the plunger, at least one pressure die casting tool, and at least one underpressure system and/or vacuum pump. The vacuum-assisted pressure die casting system may comprise two or more underpressure systems and/or vacuum pumps, one of which is connected to the pressure die casting tool and the other to the suction hole in each case. This enables the respective suctioning and/or evacuation processes to be decoupled in a simple manner. Furthermore, the vacuum-assisted pressure die casting system may comprise at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 pressure die casting tools, the pressure die casting tools preferably having different cavities for producing different components. The vacuum-assisted pressure die casting system makes it possible to achieve the advantages of the casting device described elsewhere.
Furthermore, the invention proposes a method for operating a vacuum-assisted pressure die casting system described elsewhere, the method comprising the following steps:
The extraction of the gas flowing along the sides of the plunger, i.e., the false air, when moving the plunger, prevents gas inclusions from forming in the melt. If the plunger is subsequently moved from the first end to the second end of the casting chamber, the melt, which is low in gas inclusions or preferably free of gas inclusions, is introduced into the pressure die casting tool by means of pressure. By evacuating the gas from the pressure die casting tool, the formation of gas inclusions in the pressure die casting tool and thus in the component to be produced is prevented simultaneously. The casting chamber, which is connected to the pressure die casting tool via the filling hole, can also be evacuated in the process. When the false air is extracted, gas present in the casting chamber and/or gas flowing in through the filling hole can be additionally extracted for a short time and/or over a longer period of time without impairing the method according to the invention. It is preferably conceivable to not start the evacuation of the pressure die casting tool and, if necessary, the casting chamber until the plunger closes the filling hole and/or the suction groove. It is even more preferably conceivable to not start the extraction of the false air until the plunger closes the filling hole and/or the suction groove. In addition, it is conceivable to end the extraction of the false air when the plunger has passed the suction groove and/or the melt completely fills the volume of the casting chamber. With the method according to the invention, work pieces of high quality can be produced quickly, easily and effectively.
In a variation of the method, gas present in the casting chamber, gas flowing into the casting chamber and/or gas flowing along the sides of the plunger may be extracted and/or gas in the pressure die casting tool may be evacuated in step b). If the actions are intended to take place in step c) in accordance with the invention, the actions take place in addition to step b). For instance, the actions may take place exclusively in step b), exclusively in step c), or in step b) and step c). In this manner, swirling of the gas present in the casting chamber can be prevented when the melt is poured in.
Within the scope of the invention, the method may comprise further steps in addition to those explicitly discussed, as described elsewhere.
Furthermore, it is conceivable for individual steps or all steps to be repeated any number of times. Moreover, it is conceivable for the method to be partially or fully automated.
Further details, features and advantages of the invention are apparent from the following description of the preferred embodiment in conjunction with the dependent claims. The respective features can be realized individually or in combination with one another. The invention is not limited to the embodiment. The embodiment is shown schematically in the figures. Identical reference numbers in the individual figures denote identical or functionally identical elements or elements corresponding to one another in terms of their function.
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| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2023 124 831.6 | Sep 2023 | DE | national |
