Die-casting machine and operation method

Abstract

To provide a die-cast machine and a method of operating / controlling the same.SOLUTION: The present invention relates to a die-cast machine having a casting metal mold (1), a casting chamber (2), a casting piston (3) arranged axially movably within the casting chamber, a melt-material inlet channel (4) leading to an interior of the casting chamber, a shut-off valve (5) in the melt-material inlet channel, a melt-material outlet channel (6) leading from the casting chamber to the casting metal mold, and a control unit (7) for controlling the casting piston, and a method of operating such a die-cast machine. The control unit and shut-off valve control the casting piston in the casting chamber into advancement from a casting-start position to a charge-ending position with the shut-off valve put in a close position and, in a replenishment stage, controls the casting piston to return to the casting-start position with the shut-off valve put in an open position, and controls the casting piston in order to reverse-draw the melt material due to further return movement of the casting piston.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a die-casting machine having a casting mold, a casting chamber, a casting piston axially movably disposed within the casting chamber, a melt inlet channel leading into the casting chamber, a shut-off valve in the melt inlet channel, a molten material outlet channel leading from the casting chamber to the casting mold, and a control unit for controlling the casting piston. The present invention also relates to a method for operating such a die-casting machine, comprising: advancing the casting piston in the casting chamber from a start-of-casting position to an end-of-filling position with the shut-off valve closed to perform a respective casting operation during a mold-filling phase, so that molten material is forced into the casting mold via the molten material outlet channel; and returning the casting piston to the start-of-casting position during a subsequent refilling phase, so that molten material is supplied to the casting chamber via the melt inlet channel with the shut-off valve open. [Background technology]

[0002] This type of die casting machine, both generic and similar, and the associated operating method are typically used to cast specific components, also referred to as cast parts, in each casting process or cycle. The die casting machine of the present invention, hereinafter simply referred to as machine, and the operating method of the present invention are particularly suited to casting metal die castings, e.g., liquid or partially liquid molten metal materials such as zinc, lead, aluminum, magnesium, titanium, steel, copper, and alloys of these metals. The die casting machine may, in particular, be a hot pressurized chamber die casting machine. In this embodiment, a casting chamber is formed in a casting vessel that is immersed in a bath of molten material provided by a molten material reservoir.

[0003] During the mold-filling stage of the casting process, the advancement of the casting piston forces the molten material located in the casting chamber through the melt outlet channel and into the mold cavity formed by the casting mold under pressure from the casting chamber to form the corresponding cast part. In this regard, the mold usually includes a fixed mold half and a movable mold half, between which the mold cavity, also called the mold hollow space, is formed, or the casting mold, simply called the mold, forms the mold cavity. In a typical implementation, the molten material outlet channel includes, at its inlet side, a riser pipe region of a casting vessel having a casting chamber, and at its outlet side, a mouthpiece body attached to the casting vessel. That is, after leaving the casting chamber, the molten material arrives at the melt inlet in the front region of the mold cavity, where, via the riser pipe region and the mouthpiece body, what is known as a conical gate is located.

[0004] In the refill phase, the casting piston returns from its end-of-fill position to its initial, i.e., start-of-cast position, and the return of the casting piston refills the casting chamber with molten material via the melt inlet channel. Therefore, the refill phase can also be called the piston return phase.

[0005] For a corresponding machine type, particularly suited to the present die-casting machine, the melt outlet channel exits the casting chamber separately from the melt inlet channel, i.e., the melt inlet and outlet channels form two separate guide channels for the molten material with a casting chamber inlet at which the melt inlet channel opens into the casting chamber and a separate casting chamber outlet at which the melt outlet channel opens out of the casting chamber. This configuration facilitates independent control of the molten material flow in the melt inlet and melt outlet channels, and the flow of molten material in the melt inlet channel can be controlled, in particular, by a shut-off valve disposed therein.

[0006] Depending on the system configuration, the shutoff valve can be a check valve operated purely by melt pressure, or an actively actuable shutoff valve. The latter, in this case referred to as a shutoff control valve, is controlled by a control unit. In a typical type of die casting machine and associated operating method, the shutoff control valve is typically kept closed during the entire mold filling phase and open during the entire refill phase. As an actively controllable or actuable shutoff valve, compared to a simple check valve, it provides the option of influencing or regulating the flow of molten material in the melt inlet channel as needed, which is also independent of the melt pressure ratio in the casting chamber and / or in the melt inlet channel.

[0007] Depending on the system configuration, the control unit may comprise a single controller in which all control functions of the die-casting machine are integrated, or a number of single controllers, each controlling and / or regulating a specific machine component, preferably with a communication link between them. In this case, as is usual, the control unit may be configured at least partly in hardware and / or at least partly as software. In this case, the control unit controls in particular the casting piston, more precisely the movement of the casting piston, and optionally one or more machine components, in particular the shut-off control valve, if the shut-off valve is implemented by such a shut-off control valve.

[0008] Patent Document 1 discloses such a method for a system that includes a displacement-type casting piston, known as an alternative to a spool-type casting piston, and a shutoff control valve located directly at the opening of the melt inlet channel to the casting chamber. In the spool-type case, the outer dimensions of the casting piston correspond to the inner dimensions of the casting chamber, and the piston is sealed against the casting chamber wall. As a result, in this case, when the casting piston is advanced, it pushes the molten material in the casting chamber completely forward, exerting pressure on the molten material necessary to force it into the mold cavity. In the displacement-type case, the outer dimensions of the casting piston are preferably smaller than the inner dimensions of the casting chamber, so that the casting piston is immersed in the molten material in the casting chamber as it advances. In this case, the pressure acting on the molten material is caused by the displacement effect of the volume of the casting piston immersed in the molten material.

[0009] Patent Document 2 also discloses a similar general type die casting machine and related operating method. This document uses a casting piston with a displacement-type forward piston and pressurized gas supplied into the casting chamber, and shut-off valves are located in the casting vessel having the casting chamber, upstream of the casting chamber and downstream of the casting vessel from the molten material inlet channel. During the mold filling phase, the shut-off control valve remains closed. During the refilling phase, the shut-off control valve is opened to introduce a certain amount of pressurized gas into the casting chamber, which in turn prevents the formation of a vacuum in the casting chamber and the resulting spray of molten material drawn into the casting piston before the shut-off control valve was opened, and sends the gas to the rear of the forward piston, increasing the gas pressure in the casting chamber by a certain amount above atmospheric pressure. After the required amount of molten material has been supplied during the refilling phase, the shut-off control valve is closed again.

[0010] In die casting, economic reasons require a short cycle time, i.e., the duration of each casting step, while quality reasons require a low percentage of air in the cast part, i.e., a minimum air porosity of the cast part.

[0005] Specifically, to explain the latter aspect, Patent Document 3 proposes advancing the casting piston at the beginning of the mold filling phase and / or before the actual mold filling phase, when the mold is still fully open and the molten material fills the riser tube region and the mouthpiece body region, before the mold is closed and the casting piston advances again to carry out the actual mold filling phase. In this document, the casting piston is of a spool type and functions as a closure member in that it opens the casting chamber entrance by moving back behind it during the refill phase and blocks the casting chamber entrance by moving beyond it during the mold filling phase.

[0011] Further aspects that are generally taken into consideration in this type of die casting machine are the minimization of wear effects on the casting piston and on the opposing walls of the casting chamber, particularly as a result of the stroke movement of the casting piston within the casting chamber, especially if it is of the spool type, as well as the prevention of undesired formation of melt droplets in the area of ​​the conical gate, which conventionally forms the inlet-side interface of the mold-side melt channel structure that opens into the mold cavity on the outlet side with a gate for connection to the mouthpiece body. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] European Patent No. 0576406(B1) [Patent Document 2] DE 3248423 A1 [Patent Document 3] European Patent No. 1284168(B1) Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention is based on the technical problem of providing a die casting machine of the type mentioned at the outset and an associated operating method which offers advantages over the above-mentioned prior art, in particular in terms of achieving shorter casting cycle times and / or lower air porosity in the cast part, and / or in terms of lower wear tendency of the casting piston and the casting chamber, and / or in terms of avoiding the formation of molten material droplets in the conical gate area. [Means for solving the problem]

[0014] The present invention solves this problem by providing a method for operating a die-casting machine having the features of claim 1 or 9 and a die-casting machine having the features of claim 10 or 11. Advantageous refinements of the invention are specified in the dependent claims.

[0015] According to one aspect of the present invention, claim 1 provides that during the refilling phase of the casting process, the previously opened shut-off valve is closed before the casting piston reaches its casting start position through its return movement, and as a result of further return movement of the casting piston, the molten material in the melt outlet channel is back-sucked, i.e., partially back-sucked from the melt outlet channel into the casting chamber. Closing of the shut-off valve may be actively performed by a control unit in the case of a shut-off control valve, or by a preloading element, such as a preloading spring, that preloads the valve to a closed position in the case of a check valve. Thus, in this operating method, during the initial stage of the refilling phase, the shut-off valve is first opened as the casting piston moves backward, thereby filling the casting chamber with molten material via the melt inlet channel, while during the remaining stages of the refilling phase, the shut-off valve is closed, thereby allowing further backward movement of the casting piston to back-suck the molten material in the melt outlet channel. For the purpose of opening, if implemented as a shut-off control valve, the shut-off valve is controlled in its open position by an assigned control unit, and if implemented as a check valve, the shut-off valve is controlled by the negative pressure of the molten material in the casting chamber.

[0016] This procedure according to the present invention advantageously combines the necessary refilling of the casting chamber with molten material via the melt inlet channel and partial back-suction of molten material in the melt outlet channel. In this process, after the filling stage, the unsolidified molten material in the melt outlet channel is preferably not completely back-suctioned to the molten material fill level present in the casting chamber or in the upstream molten material bath. Rather, it is left in the melt outlet channel up to its front region, to an extent that can be set and / or predefined by correspondingly selecting the time for which the shut-off valve is closed and / or the associated position of the casting piston. Therefore, in the subsequent casting process, it is not necessary to first advance to this fill level in the melt outlet channel.

[0017] These characteristics of the procedure according to the invention provide several advantages. In this way, the cycle time of subsequent casting steps can be shortened. Similarly, the stroke of the casting piston in the casting chamber can be reduced, thereby minimizing the associated wear effects. Thus, wear on wear-sensitive parts of the casting chamber and the casting piston, including conventional piston rings, is also significantly reduced by this procedure compared to, for example, conventional systems in which the casting piston serves as a shutoff element for the melt inlet channel, since the negative pressure generated during the return movement of the casting piston in the casting chamber can be kept significantly lower by appropriately controlling and / or switching the shutoff valve as needed. Since the melt outlet channel can remain substantially filled with molten material between subsequent casting steps, air is present in front of the melt outlet channel to a correspondingly small extent at the start of each casting step. As a result, the air porosity of the resulting cast parts can be significantly reduced, thereby significantly improving the quality of the resulting cast parts.

[0018] The back-suction of non-solidified molten material in the melt outlet channel can advantageously prevent the undesired formation of molten material droplets by more or less back-suctioning the molten material from the outlet region of the melt outlet channel to a controllable and / or monitorable extent, i.e., a controllable and / or predetermined amount, in the region of the conical gate of the die-casting machine and / or its forming tool, i.e., at the transition or outlet of the sprue or melt outlet channel or mouthpiece body, up to the subsequent mouthpiece nozzle or mouthpiece tip. The degree of back-suction can be appropriately set or predefined, i.e., selected, depending on the requirements and conditions of the die-casting machine, advantageously in such a way that, on the one hand, the formation of said molten material droplets is reliably prevented, and, on the other hand, the molten material still remains relatively forward, i.e., in a forward region or region preferably located forward of the melt outlet channel.

[0019] In a preferred embodiment, the molten material is sucked back at a sufficient distance to remain. That is, the molten material is available in the melt outlet channel away from the forward region or in a region relatively far from the forward region of the melt outlet channel. However, on the other hand, the molten material is positioned a certain distance behind the melt outlet channel, a relatively short distance, for example, a specific relatively short distance of about 5 mm to 100 mm from the outlet of the conical gate or the melt outlet channel. Otherwise, molten material droplets form at a certain distance from this outlet or from the melt point located immediately behind this outlet, depending on the existing system. The molten material that remains relatively liquid is then separated from the already solidified or partially solidified molten material in the conical gate or mold. Depending on the requirements, the viscosity of the melting point material, and / or the system configuration of the machine, the remaining liquid may be, for example, between about 10 mm and about 50 mm, preferably, for example, between about 30 mm and about 40 mm, suspended from the already solidified or partially solidified molten material. In a corresponding typical embodiment of a die casting machine, the backstroke of the casting piston required for this purpose, from the position of the casting piston where the shut-off valve is closed to the casting start position, is in the range of 1 mm to several millimeters, for example, between about 2 mm and 20 mm.

[0020] Countersuction is also used in subsequent casting processes to accelerate the stroke of the casting piston before it forces molten material into the mold during the first stage of the mold filling phase, which can be advantageous primarily for molds that have no gate or only a relatively small gate.

[0021] A further advantage of back-suction can be achieved in applications where the gate to the cast part solidifies before the still partially liquid material in the runner. In that case, it is possible to back-suction the not-yet-solidified molten material from the conical gate, so that it does not have to be melted again. Depending on the mold and other conditions, this may be a percentage of molten material, for example, up to about 5%, relative to the amount of molten material introduced into the mold.

[0022] In a refinement of the invention, during the refilling phase, the casting piston is moved back during the period when the shut-off valve is closed at a lower speed than during the previous period when the valve is still open. In other words, in this case, the casting piston is returned during the final back-suck stroke when the shut-off valve is open and closed at a lower speed than in the initial refilling stage. The selection of a non-constant velocity profile for the casting piston during this refilling phase advantageously combines a rapid initial refilling of the casting chamber with molten material, followed by a moderately slow back-suck stroke and the casting piston reaching its casting start position.

[0023] In a refinement of the present invention, during the refill phase of the casting process, the previously open shut-off valve is closed as soon as the casting piston reaches the valve switch position through its return movement. In the case of a shut-off control valve, this may be performed by actively controlled valve switching at this point; in the case of a check valve, for example, the casting piston is stopped at the valve switch position and / or the closed mold is opened, thus preventing further molten material underpressure from being generated in the casting chamber, so that the check valve automatically resets to its closed position. This method causes the shut-off valve to switch from its open position to its closed position depending on the position of the casting piston, more precisely, depending on reaching a specific position, in this case the valve switch position or another valve return position. Closing the shut-off valve terminates the supply of molten material to the casting chamber via the melt inlet channel, so that molten material can be re-sucked into the casting chamber to the desired extent from the melt outlet channel by further return movement of the casting piston from its valve switch position to its start-of-casting position. In the case of a check valve, undesired opening of the shut-off valve during this time can be prevented, for example, by opening the mold before the casting piston has returned from its valve switching position again. In alternative embodiments, the shut-off valve is triggered in a different way to reverse from its open position to its closed position during the refill phase of the casting process, for example, by the lapse of a predetermined time from the start of the fill phase or from the start of the return movement of the casting piston.

[0024] In a further development of the invention, the stroke distance of the casting piston between the valve switch position and the casting start position can be variably predetermined. This measure allows for flexible adaptation to different system conditions. The stroke distance of the casting piston between the valve switch position and the casting start position determines the ratio of the final return movement of the casting piston from its valve switch position to its casting start position to the total casting piston stroke, which is given by the distance between the filling end position and the casting start position and, therefore, the degree of backsuction of molten material in the melt outlet channel. This stroke distance is naturally greater than zero and less than the entire casting piston stroke, i.e., the stroke distance between the filling end position and the casting start position. It can be set to a desired value or values ​​corresponding to the respective conditions of the respective application situation, for example, a value between approximately 2 mm and 20 mm, more particularly a value between approximately 4 mm and 8 mm, depending on the conditions of the die casting machine or the system conditions. In corresponding embodiments, this value is at most half, at most one-third, or at most one-quarter of the entire casting piston stroke. The extent of back-suction of molten material in the melt outlet channel increases as the stroke distance between the valve switch position and the casting start position increases. Selecting a shorter stroke distance reduces the amount of molten material back-suctioned in the melt outlet channel. The stroke distance between the valve switch position and the casting start position of the casting piston may be selected differently for different molds used interchangeably in a die casting machine, for example. In an alternative embodiment, if variable adjustment is not required, this stroke distance may be predefined in a fixed manner.

[0025] In a further development of the invention, during the refilling phase of the casting process, the casting piston is held in the valve switching position for a pause period before moving back to its start-of-casting position. The pause period for the casting piston's return movement can be used to switch the shut-off valve from its open position to its closed position and, if necessary, open the mold. Consequently, the shut-off valve is switched during a period when the molten material is stationary in the melt inlet channel, and thus not moving through the shut-off valve. The pause period can be appropriately set in terms of its duration, for example, depending on the time required for the shut-off valve to switch from the open position to the closed position and / or the time required to open the mold; it is also possible to provide a variably changeable specification of the pause period. In an alternative embodiment, the shut-off valve is switched from its open position to its closed position without interrupting the return movement of the casting piston, i.e., without the casting piston being completely stopped in its return movement after reaching its valve switching position.

[0026] In a refinement of the invention, during the refill phase of the casting process, the mold remains closed at least as long as the shut-off valve is still open. This measure results in the casting chamber being refilled with molten material through the melt inlet channel by the return movement of the casting piston, but without significant back-suction of molten material in the melt outlet channel when the shut-off valve is in its open position. Since the mold is then still closed and generally contains a cast part that is already at least partially solidified at this point, a significant amount of air cannot enter the melt outlet channel through said mold, and therefore, during this initial stage of the refill phase, molten material is still not back-suctioned from the melt outlet channel into the casting chamber. In another embodiment, the mold is already open, and / or in any case, mold opening has begun while the shut-off valve is still open.

[0027] In a development of the present invention, particularly suitable for use with a shut-off control valve, during the refill phase of the casting process, mold opening is initiated after the casting piston reaches the mold start position. This procedure essentially results in back-suction of molten material in the melt outlet channel until the casting piston reaches the casting start position. As a result of the casting piston's return movement from the valve switching position, the shut-off control valve is closed and, upon entering the casting start position, the casting piston first creates a corresponding negative pressure. After mold opening begins, molten material is then back-suctioned from the melt outlet channel into the casting chamber to a corresponding extent due to the associated negative pressure effect.

[0028] In an alternative development of the invention, during the refill phase of the casting process, opening of the mold is initiated after the casting piston has reached its valve switching position but before it has reached its start-of-casting position. In this procedure, molten material can be sucked back into the casting chamber in or from the melt outlet channel as the casting piston moves back to the start-of-casting position. Naturally, in a corresponding embodiment, opening of the mold can be initiated at any desired time during the return movement of the casting piston from its valve switching position to its start-of-casting position, and alternatively, in a corresponding embodiment, opening can be initiated already after the casting piston has reached its valve switching position and before the shut-off valve is closed.

[0029] In a further development of the invention, during the refill phase of the casting process, the casting piston is stopped at its valve switching position, and the mold advances from its valve switching position to the start-of-casting position as soon as it reaches the mold-opening position at which it triggers when the mold is opened. In this embodiment, the further return movement of the casting piston after stopping at the valve switching position is adapted to the mold-opening process so that the casting piston does not advance to its start-of-casting position until the mold has opened to a predetermined extent, defined in particular by the mold-opening position at which it triggers the casting piston. As a result, the process of back-suctioning the molten material in the melt outlet channel in the final stage of the refill phase of the casting process can be further optimized. In an alternative embodiment, the return movement of the casting piston is performed without taking into account the current open position of the mold, provided there are no application-related requirements for this.

[0030] In a refinement of the invention, the casting piston is advanced from the start-of-casting position reached during the refill of the respective previous casting operation to a prefill position during the initial prefill stage of the mold filling phase of the subsequent casting operation, while the mold is not yet fully closed, and only then is the casting mold fully closed and the casting piston advanced further from this prefill position to its end-of-fill position, so that air that entered the front region of the melt outlet channel due to back-suction of molten material during the refill phase of the respective previous casting cycle can rapidly escape at the start of each current casting cycle through the still fully or at least partially open mold, after which the mold is fully closed and actual filling of the mold with molten material takes place.

[0031] According to a further aspect of the present invention, claim 9 is directed, which may be provided in addition to or as an alternative to the first-mentioned aspect of claim 1. During the start-up casting process, in a pre-filling stage of the start-up casting process before the mold filling stage, the shut-off valve is closed, and the casting piston in the casting chamber is advanced from the start-up position to a given pre-filling position, and then returned to the start-up position when the shut-off valve is opened. Depending on the requirements and usage, the mold can be closed before or at the start of this pre-filling stage, or alternatively, the mold can remain open during the advancement of the casting piston in this pre-filling stage and close only before the return movement of the casting piston or when the shut-off valve is opened. In the first case, no further measures are required to ensure that molten material does not inadvertently escape through the still-open mold during this pre-filling operation. In the latter case, air forced out of the melt outlet channel by the pre-filling stage can escape more quickly through the still-open mold.

[0032] The procedure according to the invention constitutes a specific initiation means which can be advantageously used when a cyclically repeated casting process of a die casting machine for casting a plurality of identical cast parts with a particular die of the casting process or casting cycle is initiated, for example after assembly of the die or casting tool on the die casting machine or after restarting the die casting machine with the particular assembled die.

[0033] In other words, a start-up casting step constitutes the first casting step or cycle for producing the desired cast part after the machine has started operating. At such start-up, molten material is not yet located in the front region of the melt outlet channel, but rather is located in the rear region of the melt outlet channel, for example, up to the level of the molten material fill level of the molten material reservoir in which the casting chamber or the casting vessel housing the casting chamber is immersed. A specific start-up casting step is one in which, as the mold filling phase begins, the casting piston advances away from its start-up position toward its end-of-fill position, ensuring that molten material is already present in the front region of the melt outlet channel for the first of many subsequent casting steps to force the molten material into the mold.

[0034] For this purpose, prior to this mold filling stage, during the pre-fill stage of the start-up casting process, the casting piston is initially advanced from its start-up position, located at this time, to a pre-fill position only, with the shut-off valve remaining closed, so that molten material from the casting chamber can be forced into the melt outlet channel. The pre-fill position of the casting piston is determined by the fact that, when it is reached, molten material has filled the melt outlet channel to a desired predetermined extent. The subsequent opening of the shut-off valve and return movement of the casting piston from its pre-fill position to its start-up position can correspond to the start-up position or a position of the casting piston further forward in the casting chamber, between the start-up position and the pre-fill position, and the amount of molten material previously forced from the casting chamber into the melt outlet channel is refilled into the casting chamber via the melt inlet channel.

[0035] For the first subsequent casting operation after the machine starts up, the same or similar conditions regarding the molten material already available up to the front region of the melt outlet channel thus exist for subsequent further casting operations in the initiated casting run of the machine. In other words, in this case, the molten material in the melt outlet channel is already available for this first casting operation up to its front region, for example, in the entire volume of the riser pipe section and in the volume of the mouthpiece body section adjacent to the melt outlet channel, up to the front end region of the mouthpiece body, and thus significantly above the assigned molten material bath level at which the molten material is supplied to the casting chamber. This offers the advantage that, thanks to this unique pre-filling, the casting piston stroke required for the subsequent actual mold filling phase can be significantly reduced already for the first casting cycle after the start of operation. In an alternative embodiment, instead of this pre-filling measure, the first casting operation after the machine starts up is performed with a casting piston stroke that is correspondingly longer than that of the further casting operations.

[0036] In the die casting machine of the present invention, for each casting operation during the mold filling phase, the control unit and the shut-off valve are configured to bring the shut-off valve to a closed position and control the casting piston in the casting chamber to move from the start-of-casting position to the end-of-filling position, forcing molten material into the mold through the melt outlet channel. During the subsequent refilling phase, the shut-off valve is first brought to an open position and the casting piston is controlled to move back to the start-of-casting position, forcing molten material into the casting chamber through the melt inlet channel.

[0037] The control unit and the shut-off valve are further configured to control the casting piston to still bring the shut-off valve back to the closed position during the refill stage before the casting piston reaches the casting start position by its return movement, and to control the casting piston so that the casting piston back-sucks the molten material in the melt outlet channel by its further return movement, and / or to control the casting piston during the start-up casting process to advance the casting chamber from the start-up position to the pre-fill position during the pre-fill stage of the start-up casting process, and then to bring the shut-off valve to the open position and control the casting piston to return to the casting start position.

[0038] As a result, this die casting machine is particularly suitable for carrying out the above-described aspects of the operating method according to the invention.

[0039] In a refinement of the invention, the shut-off valve is in the form of a shut-off control valve and the control unit is arranged to control the shut-off control valve, whereby the control unit can actively control the shut-off valve, in particular in order to place it in the desired open or closed position, respectively, during the casting process.

[0040] In a further development of the invention, the die casting machine comprises a valve actuator for actuating the shut-off control valve, which is actuated by the control unit. The actuator serves as a linking element between the control unit and the shut-off valve and can be appropriately selected depending on the type of control unit and the shut-off valve, for example, electric, magnetic, hydraulic, pneumatic or mechanical. Alternatively, the valve actuation functionality can be integrated directly in the control unit, for example.

[0041] In a refinement of the invention, the shut-off valve is in the form of a check valve preloaded in its closed position, which constitutes an alternative to the implementation as a controlled shut-off valve, in which case the shut-off valve is controlled or activated depending on the pressure of the molten material acting on it, in particular the melt pressure in the casting chamber.

[0042] In a refinement of the invention, the die casting machine comprises a valve sensor unit for sensing one or more measurement variables of the shut-off valve, which can be used, for example, to give feedback to the control unit via the valve sensor unit regarding the current position of the shut-off valve and / or to provide valve diagnostic information that provides information on whether the shut-off valve operates in an error-free manner and / or in which service state the shut-off valve is in and whether the shut-off valve, for example, requires maintenance.

[0043] The drawings show advantageous embodiments of the invention. These and further embodiments of the invention are explained in more detail below. [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 shows a longitudinal cross-sectional view of the main part of the present invention of a die casting machine having a shut-off control valve as a shut-off valve. [Figure 2] FIG. 2 is a flow chart showing the operation method of the die casting machine of FIG. 1 from the start of operation. [Figure 3] FIG. 3 shows the view of FIG. 1 during operation of the machine according to the method of FIG. 2, early in the mold filling stage of the first casting cycle. [Figure 4] FIG. 4 shows the view from FIG. 3 during the mold filling stage. [Figure 5] FIG. 5 shows the view from FIG. 3 at the beginning of the refill phase of the first casting cycle, after the mold filling phase has finished. [Figure 6] FIG. 6 shows the view from FIG. 3 during the refilling stage. [Figure 7] FIG. 7 shows the view from FIG. 3 after the refilling of the casting chamber with molten material has been completed. [Figure 8] FIG. 8 shows the view from FIG. 3 during the back-suction step of the molten material following the molten material refilling operation. [Figure 9] FIG. 9 shows a view from FIG. 3 towards the end of the first casting cycle. [Figure 10]FIG. 10 shows the view from FIG. 3 at the end of the mold filling stage of the second casting cycle. [Figure 11] FIG. 11 is a flow chart illustrating a method of operation for the die casting machine from FIG. 1 at various initial prefill stages after the first run. [Figure 12] FIG. 12 shows the view from FIG. 3 during operation of the machine according to the method from FIG. 11 at the beginning of the initial prefill stage. [Figure 13] FIG. 13 shows the view from FIG. 12 at a point after the initial pre-fill stage of refilling the casting chamber with molten material. [Figure 14] FIG. 14 shows the view from FIG. 12 at the end of the mold filling stage, following the initial pre-fill stage, of the first casting cycle in a variant of the method from FIG. [Figure 15] FIG. 15 shows a flow chart illustrating the method of operation of the die casting machine from FIG. 1 in a modified embodiment with pre-filling periodically repeated before the mold filling stage of each casting cycle. [Figure 16] Figure 16 shows a diagram from Figure 1 for a modified version of the die-casting machine with a check valve as a shut-off valve. DETAILED DESCRIPTION OF THE INVENTION

[0045] Figures 2, 11, and 15 show, in flow diagrams, various advantageous variants of the inventive method for operating a die-casting machine. Figures 1, 3 to 10, 12 to 14, and 16 show, in schematic form, the main parts of two embodiments of a die-casting machine according to the invention, which can be operated by the method according to the invention. This die-casting machine may in particular be one of the hot-pressure chamber type for die-casting liquid or partially liquid molten metal materials, such as zinc, lead, aluminum, magnesium, titanium, steel, copper, and alloys of these metals. For this purpose, the die-casting machine comprises, in particular, a casting mold 1 having a fixed mold half 1a and a movable mold half 1b, a casting chamber 2, a casting piston 3 axially movable within the casting chamber 2, a melt inlet channel 4 leading into the casting chamber 2, a shut-off valve 5 in the melt inlet channel 4, a melt outlet channel 6 leading from the casting chamber 2 to the casting mold 1, and a control unit 7.

[0046] In the examples of FIGS. 1, 3 to 10, and 12 to 14, the shutoff valve 5 is a shutoff control valve 5 SThe valve actuator 16 is configured as a shut-off valve, i.e., a valve that is activated by the control unit 7 directly or, as illustrated, by a valve actuator 16 of any conventional type, as known to those skilled in the art for actuating such valves themselves. In this regard, depending on the requirements and the circumstances of use, the actuator 16 may in particular be a conventional electrically, hydraulically, pneumatically, or directly mechanically actuated actuator type, or a mechanically actuated actuator type, such as by a lever system. In this regard, depending on the requirements and the circumstances of use, the valve actuator 16 may be either a purely binary actuator type that switches the shut-off valve 5 only between a first open position and a second closed position, or a proportional actuator type that can open the shut-off valve 5 continuously or in multiple stages, i.e., can also move the shut-off valve 5 to and hold it in one or more partially open positions between its fully open position and its fully closed position. For this purpose, the valve actuator may, if necessary, be provided with, for example, a variably settable end stop, which can be adjusted manually or automatically. In the schematic diagram corresponding to FIG. 1, FIG. 16 shows a configuration in which the shutoff valve 5 is replaced with a check valve 5 R 1. This shows a modified embodiment of the die casting machine which differs from that shown in FIG. 1 in that it is configured as follows.

[0047] In this case, control unit 7 is understood to encompass all control elements of the die casting machine for controlling and / or regulating the various components of the machine. To this end, control unit 7 may, depending on the system configuration, comprise a single controller integrating all control functions or a number of individual controllers, each controlling and / or regulating a specific machine component and preferably connected to one another. Similarly, as is typical, control unit 7 may be configured at least partially as hardware and / or at least partially as software. To illustrate all machine control functions of control unit 7, actuation arrows 7a, 7b, and 7c leading from control unit 7 to casting mold 1, casting piston 3, and valve rod 5d of shut-off valve 5, respectively, are shown in a purely symbolic and representative manner; the control functions belonging to these machine components are of primary interest here. For simplicity's sake, a schematic diagram of control unit 7 is shown only in FIG. 1 and, by contrast, omitted in FIGS. 3-10 and 12-14.

[0048] Unless mentioned in more detail below, both the control unit 7 and the rest of the mentioned machine components are themselves conventional and have a structure well known to those skilled in the art and therefore do not require further explanation here. For example, as can be seen in Figure 1, in the example shown the casting chamber 2 is formed in a casting vessel 8 of a casting unit which is conventional in this respect, and the casting vessel 8 is immersed in a bath of molten material 9 arranged in a conventional molten material vessel 10 during the casting operation.

[0049] In the illustrated example, the shut-off valve 5 is held on the casting vessel 8 by a valve housing body 5a. Alternatively, one or more inlet openings in the form of inlets 4a for the melt inlet channel 4 may be arranged on the valve housing body 5a at different positions on the casting vessel 8. That is, the molten material 14 can pass from the molten material bath 9 into the melt inlet channel 4 via the inlets 4a. The shut-off valve 5 is specifically arranged in the melt inlet channel 4 with a fixed valve seat 5b and a movable valve closing body 5c, where the valve closing body 5c is axially stationary relative to the fixed valve seat 5b and can be moved away from it by a valve rod 5d. That is, the shut-off valve 5 can be switched between an open position VO, e.g., as shown in FIG. 1, and a closed position VS, e.g., as shown in FIG. 3, to close and open the valve 5, respectively. In this regard, the open position VO may be a fully open or partially open position of the valve, depending on the valve configuration and / or operating conditions. In an alternative embodiment, not shown, the shut-off valve 5 is arranged in the casting piston 3, in which case the melt inlet channel 4 leads through the casting piston 3, in particular in a manner known per se.

[0050] As already described in the mechanical configurations of FIGS. 1, 3 to 10, and 12 to 14, the switching of the shutoff valve 5, i.e., the shutoff control valve 5 S The valve actuator 16 is operated by the control unit 7. In the mechanical configuration of FIG. R The switching is performed according to the melt pressure in the casting chamber 2, and the check valve 5 R The check valve 5 is biased into the closed position VS by a conventional preload unit 17. When a corresponding molten material underpressure exists in the casting chamber 2, the check valve 5 R is moved from the closed position VS to the open position VO by this negative pressure against the preload of the preload unit 17. As soon as the negative pressure of the molten material no longer exists, the check valve 5 Rautomatically returns to its closed position VS by the action of the preload unit 17. The preload unit 17 may for example be implemented by a correspondingly designed and arranged preload spring, such as a compression spring or a tension spring, the preload unit 17 in Figure 16 being represented purely by way of example and diagrammatically by way of illustration of a tension spring.

[0051] The melt outlet channel 6 is led in a conventional manner from the casting chamber 2 via a riser channel region and / or riser pipe section 6a formed in the casting vessel 8 and then continues in the region of the mold 1 via a mouthpiece body 6b. For this purpose, also in a conventional manner, the mouthpiece body 6b is connected on the inlet side to a mouthpiece attachment 11, whereby the riser pipe section 6a opens out to the outside of the casting vessel 8 and is led on the outlet side in the region of a conical gate 12 in the fixed mold half 1a in front of the mold cavity 13, which is formed by the two mold halves 1a, 1b when the casting mold 1 is closed and which is designed depending on the cast part to be produced.

[0052] Figure 2 illustrates the method of operation of a die casting machine according to the invention in a variant of an exemplary embodiment at the start of operation, i.e., after the machine has been started with the purpose of casting a desired number of identical cast parts in a corresponding number of subsequent casting steps or cycles. Figures 1 and 3 to 10 show the machine diagrammatically at different stages of operation during operation according to the variant embodiment of Figure 2. In this regard, the machine of Figures 3 to 10 is shown only in the embodiment of Figure 1 for simplicity, but the following relevant description applies equally to the machine configuration of Figure 16 unless otherwise stated.

[0053] In the initial operating stage B1 of Figure 2, the machine is in a base state at the start of operation. Figure 1 shows the machine in this operating stage B1, except that the mold 1, which is still open in the base state, is shown already closed. Accordingly, the casting piston 3 is positioned in the start-of-operation position BS. The shut-off valve 5 is still open, so that the molten material 14 is present in the molten material reservoir 9 anywhere up to the molten material reservoir level 9a. In particular, the molten material 14 is also located in the molten material outlet channel 6 at the same molten material reservoir level SH corresponding to the molten material reservoir level 9a, for example, but not extending to the central or front region of the riser pipe section 6a and the mouthpiece body 6b.

[0054] In the subsequent operational stage B2 of Fig. 2, the first casting cycle is initiated, for which the associated mold filling phase is carried out. For this purpose, first the mold 1 is closed and the shut-off valve 5 is moved from its open position VO to its closed position VS and / or held there. This is done by the shut-off control valve 5, which is controlled by the control unit 7. S or a check valve 5 automatically controlled by a preload unit 17. R , or in the form of a filler. FIG. 3 shows the machine at this point. Thereafter, casting piston 3 advances from start-of-operation position BS to end-of-fill position FP, i.e., downward in each of FIGS. 1, 3-10, and 12-14, so that molten material 14 is forced from casting chamber 2 into casting mold 1 via melt outlet channel 6. The forward movement of casting piston 3 is symbolically indicated in the corresponding figures by an associated direction-of-movement arrow GV. The flow of molten material in melt outlet channel 6 is indicated by corresponding flow arrows in FIG. 4, which shows the machine at the end of this mold-filling phase, which may include what is known in known manner as a follow-up or holding pressure phase, in which additional, increased follow-up or holding pressure is applied to molten material 14 in mold 1.

[0055] In the operational stage B3 of Fig. 2, the mold filling phase ends and is followed by a refill and / or piston return phase. For this purpose, the shut-off valve 5 is switched from its closed position VS to its open position VO, and the casting piston 3 is retracted from the end-of-fill position FP, i.e., moved upward in the relevant diagram. The switching of the shut-off valve 5 is effected by the shut-off control valve 5 S In this case, the control unit 7 controls the check valve 5 R In this case, the forward or backward movement of the casting piston 3 is controlled by the negative pressure of the molten material generated in the casting chamber 2 by the return movement of the casting piston 3. It should be noted here that, depending on the type of machine, the forward or backward movement of the casting piston 3 may be oriented perpendicular or at an angle to the vertical, rather than vertical as in the illustrated example. The mold 1 initially remains closed, and a so-called cooling period elapses, during which the molten material 14 in the mold cavity 13 cools, so that the solidified molten material 14 forms the desired cast part 15. The return movement of the casting piston 3 draws the molten material 14 from the molten material reservoir 9 through the melt inlet channel 4 into the casting chamber 2, thus filling it. Figures 5 and 6 show the machine at an early and slightly later point in the refill phase, respectively, during which the molten material 14 from the molten material reservoir 9 refills the casting chamber 2, as indicated by the corresponding flow arrows. The return movement of the casting piston 3 is symbolized in the corresponding figures by the associated movement direction arrow GR.

[0056] 2, the refilling of the molten material 14 from the molten material reservoir 9 to the casting chamber 2 via the melt inlet channel 4 is terminated by switching the shut-off valve 5 from its open position VO to its closed position VS. S In this case, this is effected by the control unit 7 and the check valve 5 R In this case, this is brought about by stopping the return movement of the casting piston 3, thereby no longer creating a negative pressure of the molten material in the casting chamber 2, and consequently closing the check valve 5 RThe valve 5 is automatically returned to its closed position VS by its preload unit 17. At this point, the casting piston 3 is in the corresponding valve reversal position and / or valve switching position VU. The casting piston 3 is preferably held there for a pause, the duration of which can be appropriately predetermined in such a way that the valve 5 reaches its closed position VS when the pause has elapsed. Alternatively, it is possible to select the pause corresponding to the time for the valve 5 to switch from its open position VO to its closed position VS, or to monitor when the valve 5 reaches its closed position VS and then terminate the pause or continue moving the casting piston 3. Figure 7 shows the machine at this point. Meanwhile, the cooling time of the molten material 14 in the casting mold 1 continues in order to form the cast part 15.

[0057] After the stop period has elapsed, or after the valve position VU has been passed, or after the shut-off valve 5 has been closed, the casting piston 3 is returned further to the casting start position GS in operating stage B5 of Fig. 2, after which the second casting process is started, so that the back-suction of the molten material begins. Note that the casting start position GS may be the same as the initial operating start position BS of the casting piston 3, or may differ from it to a limited extent. Fig. 8 shows the machine in an intermediate position ZS of the casting piston 3 during this return movement of the casting piston 3 beyond or away from the valve position VU.

[0058] In this regard, in the variant with the shut-off control valve 5s, the shut-off control valve 5s is held in a controlled closed position VS and the mould 1 is not yet opened, so that further return movement of the casting piston 3 creates a suction effect on the melt outlet channel 6 via the casting chamber 2. This creates a negative pressure in the area of ​​the conical gate 12, and in the particular example shown of the mouthpiece body 6b, the molten material 14 is already somewhat drawn back from the forward outlet of the melt outlet channel 6, as shown by the reverse suction arrows 14a in Figure 8.

[0059] Check valve 5 R In a variant having a shut-off control valve 5S 2 with respect to operating stage B5, the mold 1 is opened at least to a predetermined extent before the further return movement of the casting piston 3 and waits until the cooling time has elapsed or is completed. As a result, the melt outlet channel 6 is no longer sealed gas-tight against the external atmosphere on the side of the casting mold 1, which results in no underpressure of the molten material in the casting chamber 2 during the further return movement of the casting piston 3. Therefore, the check valve 5 R remains in its closed position VS. Instead, the molten material 14, particularly in the forward region of the mouthpiece body 6b, is drawn back further away from the region of the conical gate 12, i.e., a limited back-suction of molten material takes place from the forwardmost outlet region of the melt outlet channel 6, thereby preventing the formation of molten material droplets in the region of the conical gate 12.

[0060] The further return movement of the casting piston 3 from the valve switching position VU to the casting start position GS is preferably carried out at a piston speed significantly slower than the piston speed at which the casting piston 3 was previously returned from the filling end position FP to the valve switching position VU.

[0061] The stroke distance between the valve switching position VU and the casting start position GS of the casting piston 3 determines the degree of back-suction of the molten material 14 in the molten material outlet channel 6, and this stroke distance can optionally be provided as being variably predefined or settable by the user.

[0062] In the example shown, the casting piston 3 reaches the valve switching position VU at the moment of switching of the shut-off valve 5 to the closed position VS in order to finish refilling the casting chamber 2 with molten material 14 from the molten material bath 9. In alternative embodiments, this valve switching is triggered in a different way, for example after a certain period of time has elapsed since the start of the return movement of the casting piston 3 from its end-of-fill position FP.

[0063] In the operation stage B6 of FIG. 2, the return movement of the casting piston 3 is terminated after it reaches its casting start position GS. Meanwhile, the shutoff control valve 5 S 2, the cooling time for the complete solidification of the formed cast part 15 in the mold 1 has elapsed, and therefore in this variant, in a subsequent operating stage B7 of FIG. 2, the opening of the mold 1 can be initiated by a corresponding opening movement of the movable mold half 1b, as shown in FIG. 9, which shows the machine in operating time. By opening the mold 1, the shut-off control valve 5 S In a variant, the negative pressure of the pre-established counter-suction can be instantly released in the region of the conical gate 12 using the check valve 5, so that the molten material 14 shown in the front region of the molten material outlet channel 6, specifically in the front region of the mouthpiece body 6b, is drawn back further away from the region of the conical gate 12. R As described above with respect to the variant having , the pullback of molten material 14 from the outlet region of the molten material outlet channel 6 to the most forward position, i.e., the limited backsuction, prevents the formation of molten material droplets in the region of the conical gate 12. In both variants, the respectively formed cast part 15 can be removed after the mold 1 has been fully opened.

[0064] 9 shows, by way of example, the molten material 14 present in the forward region of the melt outlet channel 6 up to the back-suction point RP, which is a desired and sufficient distance AS from the region of the conical gate 12 or the outlet of the melt outlet channel or melt point, at which the back-suctioned molten material 14 separates from the solidified or partially solidified molten material remaining in the mold 1 and the conical gate 12. This ensures that droplet formation is prevented; the distance AS in FIG. 9 is exaggerated for clarity and is not drawn to scale. The distance AS is, for example, about 5 mm to 100 mm from the conical gate 12, at which distance molten droplets would otherwise form, for example, about 10 mm to 50 mm, preferably about 30 mm to 40 mm, depending on the requirements, the viscosity of the molten material, and / or the system configuration of the machine, particularly the diameter of the casting piston, the rising bore, and the mouthpiece body. Alternatively, the distance AS can also be made larger, where the larger the distance AS, the more air there is in the outlet region of the melt outlet channel 6 before the start of the next casting cycle.

[0065] In either case, however, the melt outlet channel 6 remains filled with molten material 14 above the molten material bath level 9a in the molten material bath 9, so that in the next casting cycle, the molten material 14 in the melt outlet channel 6 does not have to advance from the molten material bath level 9a, as in the first casting cycle after the start of the operating procedure according to Figure 3; rather, the molten material bath level SH in the melt outlet channel 6 is already well above the molten material bath level 9a at the start of the next casting cycle, and molten material 14 is preferably already available in the front region of the melt outlet channel 6. In this way, the first casting cycle ends after operating stage B7 in Figure 2.

[0066] To perform the second subsequent casting cycle, the mold 1 is then closed in operational stage B8 of Figure 2 and the casting piston 3 moves from its start-of-casting position GS to its end-of-filling position FP to again force molten material 14 from the casting chamber 2 through the melt outlet channel 6 into the closed mold 1. Figure 10 shows the machine at the end of the mold-filling phase of the second casting cycle, which corresponds to the machine state shown in Figure 4 at the end of the mold-filling phase of the first casting cycle.

[0067] 10, it is sufficient that the axial stroke of the casting piston 3 from the start of casting position GS to the end of filling position FP in the second casting cycle is smaller than in the first casting cycle in which the casting piston 3 is advanced from the start of operation position BS to the end of filling position FP, because in the second casting cycle the molten material 14 is already present in the melt outlet channel 6 at a level significantly above the molten material bath level 9a. In other words, as shown schematically in FIG. 10, the end of filling position FP in the second casting cycle is located further behind the end position FP1 assumed by the casting piston 3 as the end of filling position FP in the first casting cycle, i.e., at an end position FP2 relative to its position in the casting chamber 2, which is shown at the top in FIG.

[0068] In other words, the stroke distance HA = FP - GS = FP2 - GS between the end of fill position FP and the start of casting position GS for the second casting cycle of the corresponding operating interval of the machine is smaller than the corresponding stroke distance HA = FP - BS = FP1 - BS between the end of fill position FP and the start of casting position GS for the first casting cycle, this difference being determined by the amount of molten material 14 present in the melt outlet channel 6 above the molten material bath level 9a after the first casting cycle and before the second casting cycle. The stroke difference is illustrated in FIG. 10 by the corresponding stroke deviation HD = FP1 - FP2 of the end of fill position FP1 after the first casting cycle relative to the end of fill position FP2 after the second casting cycle. This stroke length reduction for the second and further casting cycles may be, for example, up to 30% or up to 50% or more, depending on the type of machine and the cast parts 15 being produced.

[0069] This reduction in the stroke length that the casting piston 3 must travel during the mold filling phase allows for a corresponding reduction in cycle time, i.e., the duration of each casting cycle for the second and each additional casting cycle, by, for example, 5% or 10% within the operating interval. Furthermore, because the molten material 14 remaining in the melt outlet channel 6 is above the molten material bath level 9a between casting cycles, the amount of air porosity displaced into the outlet portion of the melt outlet channel 6 is reduced, resulting in less air being incorporated into the cast part, which benefits the quality of the cast part. The reduction in the casting piston stroke also reduces the wear effect on the casting piston and the casting chamber associated with the movement of the casting piston within the casting chamber.

[0070] The mold filling and subsequent refilling stages of the second casting cycle then proceed in the same manner as described above for the first casting cycle and can be referenced thereto, as indicated in Figure 2 by the return arrow from operating stage B8 to operating stage B3.

[0071] Shut-off control valve 5 as shut-off valve 5 S In the embodiment shown, the casting mold 1 remains closed in a corresponding procedure during the entire refilling phase until the casting piston 3 reaches the casting start position GS as the starting position for the next casting cycle. The fact that the mold 1 is only opened at this point reaches the casting start position GS for the next casting cycle and then only at that point leads to the momentary back-suction effect mentioned at that time. In an alternative procedure, the casting mold 1 can be opened earlier, so that the back-suction effect can be configured and / or weakened more uniformly over time. In this connection, in a corresponding variant, the casting mold 1 at least has a shut-off control valve 5 for refilling the casting chamber 2 with molten material 14 from the molten material bath 9. S The casting piston 3 reaches its valve switching position VU, thereby closing the shut-off control valve. 5 S is closed, depending on the requirements, the casting mold 1 opens earlier or later upon further return movement of the casting piston 3 from the valve switching position VU to the casting start position GS. As soon as the opening of the mold 1 begins, more air can enter the front region of the melt outlet channel 6 through the outlet side of the melt outlet channel 6, thereby weakening and / or alleviating the negative pressure effect there.

[0072] In yet another embodiment, the casting piston 3 is held in the valve switching position VU, and the mold 1 is opened after a cooling time has elapsed. As soon as the casting mold 1 opens, a predetermined mold opening position, which may be variably or permanently predefined, is reached, which triggers the casting piston. For example, when the movable mold half 1b moves away from the fixed mold half 1a by a corresponding predetermined distance, the casting piston 3 is further returned from its valve switching position VU to its casting start position GS. At this point, the mold opening position which triggers the casting piston is selected so that air can enter the melt outlet channel 6 via the conical gate 12 or the mouthpiece nozzle. This allows the molten material 14 to be back-sucked relatively uniformly over time in the forward-most region of the melt outlet channel 6 without a sudden drop in negative pressure. This operation can be modified, for example, by using a check valve 5 as the shut-off valve 5. R 16. Then, as soon as the mold 1 has thus been opened sufficiently to allow the melt to enter the melt outlet channel 6, the further return movement of the casting piston 3 no longer creates a negative pressure of the molten material in the casting chamber 2, and the check valve 5 is opened. R remains automatically in its closed position VS by the action of the preload unit 17.

[0073] FIG. 11 illustrates a more advantageous embodiment of the method for operating the die casting machine according to the present invention. Specifically, it relates to the performance of each first casting cycle after the start of operation of the machine, and mainly focuses on the shutoff control valve 5. S For this purpose, this operating variant again proceeds from the basic state of the machine at the start of operation according to the initial operating stage B1 of Fig. 2. However, in contrast to the operating example of Fig. 2, in the operating variant of Fig. 11, at the start of the casting process, i.e. in the particular first casting cycle, an initial pre-filling stage is carried out upstream of the mold filling phase.

[0074] For this purpose, in operating stage B2a of FIG. 11, this initial prefill phase begins with the casting piston 3 advancing from the operating start position BS only to the initial prefill position VP, as shown below. FIG. 12 shows the machine after the shutoff control valve 5 is closed and the mold 1 is closed. FIG. 12 shows the machine in this operating stage B2a. As a result, the melt outlet channel 6 is prefilled with molten material 14 above the molten material bath level 9a in the molten material bath 9, preferably up to a prefill point VA in the front region of the melt outlet channel 6 or the mouthpiece body 6b. As a result, the prefill point VA is only a relatively small distance DS from the outlet of the melt outlet channel 6 into the mold 1 or from the conical gate 12. This distance DS corresponds approximately to the distance AS between the outlet of the melt outlet channel 6 into the mold 1 and the back-suction point RP, which exists, for example, in the operating example of FIG. 2 and after the aforementioned back-suction of molten material 14 in the melt outlet channel 6, as shown in FIG. 9. Alternatively, the distance DS may also differ slightly or significantly from the distance AS.

[0075] After this, in operational stage B2b of Figure 11, a predetermined time is waited for excess pressure built up as a result of the pre-fill process due to compressed air in the mold cavity 13 to subside. Then, in operational stage B2c of Figure 11, the shut-off control valve 5 is reversed from its closed position VS to its open position OS, and the casting piston 3 is returned from the pre-fill position VP to its start-of-casting position GS. As a result, molten material is drawn or filled into the casting chamber 2 from the molten material reservoir 9 via the melt inlet channel 4, as illustrated by the associated flow arrows in Figure 13. Figure 13 shows the machine at the end of this operational stage B2c, at which point the casting piston 3 has again reached its start-of-casting position GS.

[0076] This molten material refilling process may involve some further backsuction of the molten material 14 in the melt outlet channel 6 because a certain amount of air is also present in the closed mold 1, which is also likely not completely airtight. As a result, the pre-fill point VA where the molten material 14 was pre-filled in the melt outlet channel 6 may be displaced somewhat rearward accordingly, as shown in Figure 13, by the associated backflow arrow in the melt outlet channel 6 and the pre-fill point VA being located further rearward in the mouthpiece body 6b compared to Figure 12, but the molten material 14 remains pre-filled in the melt outlet channel 6 well above the molten material bath level 9a in the molten material bath 9, up to the front region of said melt outlet channel.

[0077] In principle, a check valve 5 is used as a shutoff valve 5 R A similar pre-filling process can be carried out for variants of machines having a check valve 5. R remains closed by the molten material pressure in the casting chamber 2, and the casting piston 3 is advanced from its start-of-operation position BS to its pre-fill position VP. Thereafter, as described above, a suitable reduction in the excess pressure in the operating stage B2b is provided, and then the return movement of the casting piston 3 from the pre-fill position VP to its start-of-casting position GS is stopped by the check valve 5 when the back-suction of molten material in the melt outlet channel 6 is sufficiently prevented or slowed down, for example, by an operable closure in the melt outlet channel 6 and / or by a sufficiently rapid return movement of the casting piston 3. R A negative pressure sufficient to open the casting chamber 2 can be generated in the casting chamber 2, so that in this case too, molten material can be sucked or refilled into the casting chamber 2 from the molten material reservoir 9 via the molten material inlet channel 4.

[0078] After this initial pre-filling stage is completed, the mold filling stage of the first casting cycle is carried out according to operational stage B2d of FIG. 11, for which purpose the shut-off control valve 5 is again returned to the closed position VS or the check valve 5 is closed. Rautomatically closes again after the negative pressure of the molten material in the casting chamber 2 has decreased, and the casting piston 3 advances from its casting start position GS to its filling end position FP, so that the molten material 14 again flows from the casting chamber 2 through the melt outlet channel 6 into the casting mold 1, in particular mold It is pushed into the cavity 13 .

[0079] Compared to a first casting cycle without pre-filling, the initial pre-filling, as in the operating variant illustrated in FIG. 2, results in a shortening of the stroke distance HA between the end-of-filling position FP and the start-of-operation position BS for this mold-filling phase of the first casting cycle by HA=FP-BS. This stroke shortening for the first casting cycle is achieved similarly to the stroke shortening described above, which, in the operating variant of FIG. 2, is achieved only for further casting cycles by early closing of the shut-off control valve 5 in the re-filling phase of the preceding casting cycle, before reaching the start-of-casting position GS and before further return movement of the casting piston 3 to the start-of-casting position GS. FIG. 14 shows the machine in operating stage B2d at the end of the mold-filling phase of the first casting cycle. The end-of-filling position FP is determined by the stroke deviation HD1=FP1-FP 1V FP1 for the operating variant with the first pre-fill, which is located after the end-of-fill position FP1 of the first casting cycle for the operating variant of FIG. 2 without pre-filling according to 1V In other words, in this operating variant, as a result of this pre-filling measure, there is a shortened casting stroke for performing the mold filling operation for the first casting cycle compared to the operating variant of Figure 2 without pre-filling.

[0080] Therefore, in the operating variant of FIG. 11, the stroke shortening in the second casting cycle and the characteristics and advantages described above in relation to the further casting cycle in the operating variant of FIG. 2 are achieved.

[0081] Further progression of the first casting cycle can correspond to progression of the operating variant of Figure 2, apart from operating stage B3. Alternatively, the first casting cycle in the operating variant of Figure 11 may continue according to any desired conventional method of operation.

[0082] FIG. 15 illustrates an advantageous variant of the operating method of FIG. 2 for the execution of a second and further casting cycles. In this variant of the method, each mold filling phase from the second casting cycle includes a prefill stage. In this respect, we proceed from the operating situation at the end of operating stage B7, as shown in FIG. 9. In contrast to the operating variant according to operating stage B8 of FIG. 2, the operating variant from FIG. 15 in operating stage B8a with the advancement of the casting piston 3 does not wait for the mold 1 to be completely closed. Rather, while the mold 1 is still open, the casting piston 3 is already advanced from the casting start position GS to a prefill position VP2 for the second casting cycle, also referred to herein as a periodically repeated prefill position VP2, to distinguish it from the prefill position VP at the end of the first prefill stage before the first casting cycle, according to the operating variant of FIG. 11 and the example of FIG. 12.

[0083] This periodically repeated pre-filling means allows the molten material 14 previously sucked from the outlet side of the molten material outlet channel 6 in accordance with operating stages B5 to B7 of the operating variant of Figure 2 to be advanced again in the direction of the outlet side of the molten material outlet channel 6, thereby allowing the molten material outlet channel 6 to be pre-filled to a greater extent, and air in the front end region of the molten material outlet channel 6 can escape unhindered through the unclosed mold 1.

[0084] In operational stage B8b of Fig. 15, the casting piston 3 is held in this cyclically repeated pre-fill position until the mold 1 is fully closed. The remaining steps of the mold-filling phase of the associated second or further casting cycle are then carried out according to operational stage B8c of Fig. 15, with the casting piston 3 advancing from the cyclically repeated fill position to the end-filling positions FP and FP2 to force molten material 14 from the casting chamber 2 through the pre-filled melt outlet channel 6 into the closed mold 1 or its casting cavity 13. The operational state of the machine at this point corresponds to that of Fig. 10 or to the end of operational stage B8 of Fig. 2. In other words, in the operational variant of Fig. 15, after the mold-filling phase is finished, at the end of operational stage B8c, the re-filling phase and further phases, starting from operational stage B3 of Fig. 2, continue.

[0085] The periodically repeated pre-filling at the beginning of the mold filling phase of the second and further casting cycles allows the cycle time and the air porosity of the cast parts to be additionally reduced by a corresponding amount. In a correspondingly optimized manner, the operating variants of Figures 2, 11 and 15 can be combined in their effect, so that at the beginning of each operating period of the die-casting machine, an initial pre-filling is carried out by refilling the casting chamber with molten material according to the operating variant of Figure 11, then the remaining steps of the first casting cycle are carried out according to the operating variant of Figure 2, and then the second and further casting cycles are carried out according to the operating variant of Figure 15. Alternatively, operational variants according to the invention allow for these method variants, which use only specific initial pre-filling stage steps and molten material refilling steps after the start of the operational operation according to FIG. 11, or only the back-suction means according to operational stages B3 to B8 of FIG. 2, with or without additional combination with periodically repeated (cyclic) refilling steps according to FIG. 15.

[0086] The die-casting machine according to the invention is configured to carry out the operating method according to the invention, as shown in the figures. In particular, a control unit 7 is correspondingly configured to carry out the respective casting process, for which purpose the control unit 7 controls the casting piston 3 in the casting chamber 2 to advance it from a casting start position GS to a filling end position FP during the mold filling phase, forcing the molten material 14 into the casting mold 1 via the melt outlet channel 6, for which purpose in the examples of Figures 1, 3 to 10 and 12 to 14 the shut-off control valve 5 is operated. S is controlled to its closed position VS directly or via a valve actuator 16, while in the machine configuration according to FIG. R The casting piston 3 automatically remains in its closed position VS under the action of the preload unit 17 and the molten material pressure in the casting chamber 2. The control unit 7 also controls the casting piston 3 to return to the casting start position during the subsequent refilling phase, supplying the molten material 14 into the casting chamber 2 via the melt inlet channel 4, and for this purpose in the machine configurations of Figures 1, 3-10 and 12-14 the shut-off control valve 5 S 16 is controlled to its open position VO, while the non-return valve 5 R is brought into its open position VO by the negative pressure in the casting chamber 2.

[0087] The control unit 7 and the shut-off valve 5 may also be configured to switch the shut-off valve 5 back to the closed position VS during the filling phase before the casting piston 3 reaches the start-of-casting position GS in its return movement, and to control the casting piston 3 in its return movement to back-suck the molten material in the melt outlet channel 6. Alternatively or additionally, the control unit 7 may be configured to control the casting piston 3 in the first phase of the casting process, i.e. in the first casting cycle, from the start-of-operation position BS to the pre-fill position GS during a pre-fill phase at the start of the casting process before the mold filling phase, when the shut-off valve 5 is closed. VPinto the casting chamber 2 until the shut-off valve 5 moves to its open position VO and the casting piston 3 moves back to its start-of-casting position GS.

[0088] As in the illustrated example, the die casting machine optionally includes a valve sensor unit 18 for sensing one or more variables of the shut-off valve 5. Measurement values ​​for each measurement variable detected by the valve sensor unit 18 may be supplied to the control unit 7 as needed to provide feedback control regarding the current position of the shut-off valve 5. Additionally or alternatively, the measured values ​​may be used for diagnostic evaluation, for example to diagnose the current state of the shut-off valve 5 with respect to any faults and to identify when the shut-off valve 5 requires maintenance.

[0089] Depending on the requirements and the situation of use, the valve sensor unit 18 may comprise one or more sensors, including optional limit switches, with or without a link to the control unit 7, which, as already mentioned, may be the entire machine control system of the die-casting machine or part of this machine control system. The valve sensor unit 18 may be configured to measure the stroke of the shut-off valve in order to derive error diagnoses therefrom, for example, whether the valve closing body 5c tears and the valve rod 5d overruns its intended position during the valve closing movement, and / or whether the valve closing body 5c actually reaches its closed position or stops early. The valve sensor unit 18 may also optionally comprise a force sensor in the valve rod 5d for diagnostic monitoring, measuring the closing force or contact pressure and / or opening force of the valve closing body 5c. For example, in the case of electrical or hydraulic and / or pneumatic valve actuation by the valve actuator 16, the valve sensor unit 18 may comprise a flow or pressure sensor of conventional design for this monitoring, with or without a link to the control unit 7.

[0090] As is evident from the exemplary embodiment shown and the further exemplary embodiments described above, the present invention provides an advantageous method for operating a die-casting machine, which makes it possible to achieve short casting cycle times, lower air porosity in the cast part, less wear on the casting piston and the casting chamber due to a reduced casting piston stroke, and / or avoidance of the formation of molten material droplets in the conical gate area. The present invention also provides a die-casting machine suitable for carrying out this operating method, which may in particular be of the hot pressurized chamber type.

Claims

1. 1. A method for operating a die casting machine having a casting mold (1), a casting chamber (2), a casting piston (3) axially movably arranged within the casting chamber, a melt inlet channel (4) leading into the casting chamber, a shut-off valve (5) in the melt inlet channel, a melt outlet channel (6) leading from the casting chamber to the casting mold, and a control unit (7) for controlling the casting piston (3) and the shut-off valve (5), 1. A method for performing each casting operation during a mold filling phase, wherein the casting piston in the casting chamber is advanced from a start-of-casting position (GS) to a finish-of-filling position (FP) with the shut-off valve closed, so that molten material (14) is forced into the casting mold via the melt outlet channel, and during a subsequent refill phase, the casting piston is moved back to the start-of-casting position with the shut-off valve open, so that molten material is supplied to the casting chamber via the melt inlet channel. During the refilling stage of the casting process, the previously opened shut-off valve (5) is closed before the casting piston (3) reaches the casting start position (GS) by its return movement, and the control unit (7) controls the casting piston (3) and the shut-off valve (5) so that as a result of further return movement of the casting piston, the molten material (14) in the melt outlet channel (6) is back-sucked. A method characterized by:

2. 1. A method of operating a die casting machine having a casting mold (1), a casting chamber (2), a casting piston (3) axially movably arranged within the casting chamber, a melt inlet channel (4) leading into the casting chamber, a shut-off valve (5) in the melt inlet channel, a melt outlet channel (6) leading from the casting chamber to the casting mold, and a control unit (7) for controlling the casting piston (3) and the shut-off valve (5), 1. A method for performing each casting operation during a mold filling phase, wherein the casting piston in the casting chamber is advanced from a start-of-casting position (GS) to a finish-of-filling position (FP) with the shut-off valve closed, so that molten material (14) is forced into the casting mold via the melt outlet channel, and during a subsequent refill phase, the casting piston is moved back to the start-of-casting position with the shut-off valve open, so that molten material is supplied to the casting chamber via the melt inlet channel. The control unit (7) controls the casting piston (3) and the shut-off valve (5) so that, in a pre-filling stage of a start-of-operation casting process before a mold filling stage, the casting piston (3) in the casting chamber (2) moves from a start-of-operation position (BS) to a pre-filling position (VP) with the shut-off valve (5) closed, and then opens the shut-off valve so that the casting piston returns to the start-of-operation position. A method characterized by:

3. The method described in claim 1, wherein, during the pre-filling stage of the start-of-operation casting process prior to the mold filling stage, with the shut-off valve (5) closed, the casting piston (3) in the casting chamber (2) advances from the start-of-operation position (BS) to the pre-filling position (VP), and then the control unit (7) controls the casting piston (3) and the shut-off valve (5) so that the casting piston returns to the start-of-operation position by opening the shut-off valve.

4. During the refilling phase, the casting piston moves back while the shut-off valve is closed at a low speed during the preceding period while still open, and / or 4. The method according to claim 1, wherein during the refilling stage of the casting process, the previously opened shut-off valve closes as soon as the casting piston reaches a valve switching position (VU) with its return movement.

5. The stroke distance of the casting piston between the valve switching position and the casting start position can be variably predetermined, and / or 5. The method of claim 4 further characterized in that during the refill stage of the casting process, the casting piston is held in a valve switching position during a dwell period before being returned to a start-of-casting position.

6. 6. The method of any one of claims 1 to 5, further characterized in that during the refill stage of the casting process, the casting mold remains closed at least while the isolation valve remains open.

7. 7. The method of claim 1, further comprising the step of: during a refill stage of the casting process, opening of the casting mold is initiated after the casting piston has reached its start-of-casting position.

8. 7. The method of claim 1, further comprising the step of: during a refill stage of the casting process, opening of the casting mold is initiated after the casting piston has reached its valve switching position but before it has reached a start-of-casting position.

9. 9. The method of claim 8, wherein during the refill phase of the casting process, the casting pistons are stopped in a valve changeover position, and the casting pistons are advanced from the valve changeover position to their start-of-cast position as soon as the casting mold reaches a mold-open position that triggers a given casting piston when the casting mold opens.

10. 10. The method of any one of claims 1 to 9, further characterized in that the casting piston is advanced from a start-of-casting position reached in the refill phase of each previous casting operation to a pre-fill position during an initial pre-fill stage of the mold filling phase of a subsequent casting operation, when the casting mold is not yet fully closed, and only thereafter the casting mold is fully closed and the casting piston is advanced to an end-of-fill position.

11. A die casting machine, A casting mold (1), a casting chamber (2); a casting piston (3) arranged in the casting chamber so as to be axially movable; a melt inlet channel (4) leading to the casting chamber; a shut-off valve (5) in the melt inlet channel; a melt outlet channel (6) leading from the casting chamber to the casting mold; a control unit (7) for controlling the casting piston (3) and the shut-off valve (5); In order to carry out each casting process during a mold filling stage, the control unit (7) and the shut-off valve (5) are configured to bring the shut-off valve to a closed position (VS) and control the casting piston (3) in the casting chamber (2) to move from a casting start position (GS) to a filling end position (FP), forcing molten material (14) into the casting mold through the melt outlet channel, and in a subsequent refilling stage, bring the shut-off valve to an open position (VO) and control the casting piston to move back to the casting start position, for supplying molten material to the casting chamber through the melt inlet channel. the control unit (7) and the shut-off valve (5) are configured to control the casting piston (3) to bring the shut-off valve back to its closed position (VS) during the refilling phase before the casting piston (3) reaches the casting start position by its return movement and to back-suck the molten material (14) in the melt outlet channel (6) by its further return movement; and / or 10. The die casting machine according to claim 9, wherein the control unit (7) and the shut-off valve (5) are further configured to control the casting piston (3) during a start-of-casting operation to advance from a start-of-operation position (BS) to a pre-fill position (FP) in the casting chamber (2) in a pre-fill phase of the start-of-casting operation prior to the mold filling phase with the shut-off valve (5) closed, thus bringing the shut-off valve to an open position (VO) and moving the casting piston back to a start-of-casting position (GS).

12. The shutoff valve is a shutoff control valve (5 S ) and the control unit is in the form of the shut-off control valve (5 S 12. The die casting machine of claim 11, configured to control a

13. 13. The die casting machine according to claim 12, characterized by a valve actuator (16) activated by the control unit for driving the shut-off control valve.

14. The shut-off valve is a check valve (5) preloaded in the closed position. R 12. The die casting machine of claim 11 further characterized in that it is in the form of a

15. A die casting machine according to any one of claims 11 to 14, further characterised by a valve sensor unit (18) for sensing one or more measured variables of the shut-off valve.

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