Molding machine and operating method

Abstract

The invention relates to a die casting machine having a casting mold (1), a casting chamber (2), a casting piston (3) arranged in the casting chamber in an axially movable manner, 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, and to a method for operating such a die casting machine.

Description

TECHNICAL FIELD

[0001] The invention relates to a die casting machine having a casting mold, a casting chamber, a casting piston arranged in an axially movable manner in the casting chamber, a melt inlet channel leading into the casting chamber, a shut-off valve in the melt inlet channel, a melt outlet channel leading from the casting chamber to the casting mold, and a control unit for controlling the casting piston. The invention also relates to a method for operating such a die casting machine, in which, in order to carry out a corresponding casting process, in a mold filling phase, with the shut-off valve closed, the casting piston in the casting chamber is advanced from a casting start position to an end-of-fill position, and as a result, molten material is pressed via the melt outlet channel into the casting mold, and in a subsequent refill phase, the casting piston is moved back into the casting start position, and as a result, with the shut-off valve open, molten material is supplied back to the casting chamber via the melt inlet channel. BACKGROUND

[0002] Die casting machines of this type, of the general type and of similar type, and related methods of operation are generally used for casting specific components, also referred to as castings, in a corresponding casting process or casting cycle. The present die casting machine, in the following also referred to as machine, and the present method of operation are particularly suitable for metal die casting, for example for casting liquid or partially liquid metal melts, such as zinc, lead, aluminum, magnesium, titanium, steel, copper and alloys of these metals. The die casting machine can particularly be a hot-chamber die casting machine. In this implementation, the casting chamber is formed in a casting vessel which is immersed in a melt bath prepared by a melt vessel.

[0003] In the mold filling phase of the casting process, the advancement of the casting piston presses the molten material located in the casting chamber under pressure from the casting chamber via the melt outlet channel into a mold cavity formed by the casting mold, in order to form a corresponding casting. In this regard, the casting mold typically comprises stationary and movable mold halves between which the mold cavity, also referred to as mold hollow space, or simply as mold in a way synonymous with the casting mold formed thereby, is formed. In a typical implementation, the melt outlet channel comprises a riser region of the casting vessel which comprises the casting chamber on the inlet side and a spout body attached to the casting vessel on the outlet side, i.e. after leaving the casting chamber, the molten material reaches a melt inlet in a region directly in front of the mold cavity via the riser region and the spout body, a so-called sprue cone typically being located in this region.

[0004] In the refill phase, the casting piston is moved back from its end-of-fill position to its initial position, i.e. the casting start position, and the return movement of the casting piston refills the casting chamber with molten material via the melt inlet channel. The refill phase can thus also be referred to as piston return phase.

[0005] In the case of a corresponding machine type, as is particularly suitable for the present die casting machine, the melt outlet channel is guided out of the casting chamber separately from the melt inlet channel, i.e. the melt inlet channel and the melt outlet channel form two separate guiding channels for the molten material, which have 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 from the casting chamber. This configuration facilitates independent control of the melt flow in the melt inlet channel and the melt outlet channel, in particular the melt flow in the melt inlet channel can be controlled by a shut-off valve located there.

[0006] Depending on the system configuration, it is possible to use a purely melt pressure actuated non-return valve or an actively actuatable shut-off valve as a shut-off valve. The latter is referred to as a shut-off control valve in the present case and is controlled by a control unit. In these general types of die casting machines and associated methods of operation, the shut-off control valve is typically kept closed during the entire mold filling phase and kept open during the entire refilling phase. In comparison to a simple non-return valve, as an actively controllable or actuatable shut-off valve, it provides the option to influence or regulate the melt flow through the melt inlet channel as required, which is also independent of the melt pressure ratio in the casting chamber and / or the melt inlet channel.

[0007] Depending on the system configuration, the control unit comprises a single control device in which all control functions of the die casting machine are integrated, or a plurality of single control devices, each of which controls and / or regulates a particular machine component and preferably has a communication link to one another. In this case, the control unit can be at least partially configured in hardware and / or at least partially configured as software, as is customary. In the present case, the control unit controls, in particular, the casting piston, more precisely, the movement of the casting piston, and optionally, one or more further machine components, such as, in particular, a shut-off control valve, if a shut-off valve is implemented by such a shut-off control valve.

[0008] The patent publication EP 0 576 406 B1 discloses such a procedure for a system having a casting piston of the displacement type, as an alternative to the casting pistons known as rotary shaft type, and having a shut-off control valve arranged directly at the opening of the melt inlet channel into the casting chamber. In the case of the rotary shaft type, the outer dimensions of the casting piston correspond to the inner dimensions of the casting chamber, the piston being sealed against the casting chamber wall. Thus, in this case, when the casting piston advances, it pushes the molten material in the casting chamber completely forward and, in the process, exerts the pressure on the molten material that is required to press the molten material into the mold cavity. In the case of the displacement type, the outer dimensions of the casting piston are suitably smaller than the inner dimensions of the casting chamber, and thus the casting piston, when it advances, dips into the molten material of the casting chamber. In this case, the effect of the pressure on the molten material is caused by the displacement effect of the volume of the casting piston that dips into the molten material.

[0009] The publication DE 32 48 423 A1 likewise discloses a die casting machine of the general type and a related method of operation, in which, in the document, a casting piston having a displacement type of a front piston and a pressurized gas, which additionally can be fed to the casting chamber, are used, and the shut-off control valve is located in the casting vessel containing the casting chamber at a respective distance in terms of flow (upstream of the casting chamber and downstream of the inlet into the casting vessel in the melt inlet channel). During the mold filling phase, the shut-off control valve remains closed. During the refilling phase, the shut-off control valve opens and conducts an amount of pressurized gas into the casting chamber in order to avoid, before the shut-off control valve opens, the formation of a vacuum in the casting chamber and the resulting spraying of the melt pulled onto the casting piston parts behind the front piston, and to bias the gas pressure in the casting chamber by an amount above atmospheric pressure. After the required amount of melt is fed during the refilling phase, the shut-off control valve closes again.

[0010] In die casting, for economic reasons, the shortest cycle time (i.e. the duration of the corresponding casting process) is sought, and for reasons related to the quality of the cast, the lowest air fraction in the cast (i.e. the minimum air porosity of the cast) is sought. In particular with regard to the latter aspect, patent publication EP 1284168 B1 proposes that, at the beginning of the mold filling phase and / or before the actual mold filling phase, in a pre-filling phase, the casting piston is already advanced when the mold is still open far enough so that the molten material fills the riser region and the spout body region, the actual mold filling phase is performed before the mold is then closed and the casting piston is advanced again. In said document, the casting piston is of the rotating shaft type and functions as a shut-off member as such, wherein the casting piston opens the casting chamber inlet by performing a return movement behind the casting chamber inlet during the refill phase, and cuts off said casting chamber inlet by advancing beyond the casting chamber inlet during the mold filling phase.

[0011] Further aspects to be considered in general in the case of die casting machines of the type in question are, among others, the minimization of the wear effects of the relative positioning of the walls of the casting piston and the casting chamber due to the stroke movement of the casting piston in the casting chamber, in particular if the casting piston is of the rotating shaft type, and the prevention of the undesired formation of molten droplets in the region of the sprue cone, which conventionally forms the inlet-side abutment of the mold-side melt channel structure, which is open on the outlet side, with a sprue into the mold cavity, for the purpose of coupling to the spout body. SUMMARY

[0012] The present invention is based on the technical problem of providing a die casting machine of the type mentioned at the outset and a related method of operation, which offers advantages over the prior art described above, in particular with regard to achieving a relatively short casting cycle time and / or a relatively low air porosity in the cast, and / or with regard to a relatively low tendency of the casting piston and the casting chamber to wear and / or to avoid the formation of molten droplets in the region of the sprue cone.

[0013] The invention solves this problem by providing a method of operating a die casting machine (with the features of claim 1 or claim 9) and a die casting machine (with the features of claim 10 or claim 11). Advantageous refinements of the invention are specified in the dependent claims.

[0014] According to one aspect of the method of operation (according to the application), claim 1 relates to this aspect that, in the refill phase of the casting process, the previously opened shut-off valve is closed before the casting piston reaches its casting start position by its return movement and, due to a further return movement of the casting piston, the molten material in the melt outlet channel is sucked back, i.e. partially from the melt outlet channel into the casting chamber. The closure of the shut-off valve can be actively performed in the case of a shut-off control valve by the control unit and in the case of a check valve, for example, by a preloading element, such as a preloading spring, which preloads the valve in its closed position. Thus, in this method of operation, in the initial period of the refill phase, the shut-off valve is initially opened when the casting piston moves back, with the result that the casting chamber is refilled with molten material via the melt inlet channel, while in the remaining period of the refill phase, the shut-off valve is closed, with the result that a further movement back of the casting piston makes it possible to suck back the molten material in the melt outlet channel. For the opening, when implemented as a shut-off control valve, the shut-off valve is controlled by a specified control unit into its open position, and when implemented as a check valve, the shut-off valve is controlled by the negative pressure of the melt in the casting chamber.

[0015] This procedure according to the application advantageously combines the desired refilling of the casting chamber with molten material via the melt inlet channel with the partial sucking back of the molten material in the melt outlet channel. In the process, after the filling phase, the non-solidified molten material in the melt outlet channel is preferably not completely sucked back to the melt filling level present in the casting chamber or upstream melt pool, but can remain in the melt outlet channel to a degree, which can be set and / or predefined by correspondingly selecting the point in time of the closure of the shut-off valve and / or the associated position of the casting piston, and thus, in the subsequent casting process, it is not first necessary to advance to this filling level in the melt outlet channel.

[0016] Due to these properties, this procedure according to the application offers many advantages. In this way, the cycle time of the casting processes following one another can be shortened. Similarly, the movement stroke of the casting piston in the casting chamber can be reduced, so that the associated wear effects can be minimized. The wear at the parts of the casting chamber and the casting piston, including the usual piston rings, which are subject to wear, is also considerably reduced by this procedure according to the application, for example, compared to conventional systems in which the casting piston functions as a shut-off component for the melt inlet channel, since the negative pressure occurring during the return movement of the casting piston in the casting chamber can be kept significantly lower by appropriately controlling and / or switching the shut-off valve as required. Since the melt outlet channel can remain mainly filled with molten material between the casting processes following one another, air is present in the front portion of the melt outlet channel to a correspondingly small extent at the start of the respective casting process, so that the air porosity of the castings produced can be significantly reduced, which can thus considerably improve the quality of the castings produced.

[0017] The back suction of the non-solidified molten material in the melt outlet channel makes it possible to very advantageously prevent, to a controllable and / or monitorable extent, i.e. in a controllable and / or predefinable amount, the undesired formation of molten droplets in the region of the gate cone of the mold casting machine and / or of its molding tool, i.e. at the injection gate or at the transition or outlet of the melt outlet channel or spout body, by back suctioning the molten material more or less into the melt outlet channel, thereby forming an outlet-side portion of the melt outlet channel (with regard to the subsequent spout nozzle or spout tip). The extent of the back suction can expediently be set or predefined (i.e. selected) in a manner dependent on the requirements and conditions of the mold casting machine, such that, on the one hand, the formation of molten droplets is reliably prevented, and, on the other hand, the molten material still remains relatively front-facing, i.e. preferably in the front region or in a region located relatively front-facing, in the melt outlet channel.

[0018] In an advantageous implementation, in this respect, the molten material is back suctioned far enough that, on the one hand, it remains (i.e. is available) in the melt outlet channel as far as the front region or a region located relatively front-facing of the melt outlet channel, but, on the other hand, it is located behind the melt outlet channel at a certain, relatively low distance, for example approximately 5 mm to approximately 100 mm, from the gate cone or outlet of the melt outlet channel, at which, depending on the existing system, molten droplets would otherwise form, in particular at a distance from the outlet or from the melt point located not far behind the outlet, and at which, depending on the requirements, the viscosity of the molten material and / or the system configuration of the machine, the relatively liquid melt separates from the front-facing, already solidified or partially solidified melt in the gate cone or in the mold between approximately 10 mm and approximately 50 mm, preferably for example between approximately 30 mm and approximately 40 mm. In a corresponding typical embodiment of the mold casting machine, the back suction stroke required for this purpose, from the position of the cutting valve closed casting piston to the casting start position, is in the range of a few millimeters, for example between approximately 2 mm and 20 mm.

[0019] Furthermore, the back suction has the advantage that a corresponding travel of the stroke of the casting piston is thus obtained, which can be used in the subsequent casting process to accelerate the casting piston before it starts to press the molten material into the mold. This can also be primarily advantageous in the case of molds without an injection gate or with only a relatively small injection gate.

[0020] A further advantage of the counter suction can result in the case of an application in which the gating to the solidification of the casting is applied before the material still partly liquid in the flow channel. In this case it is possible to counter-suck the not yet solidified molten material from the sprue cone, as a result of which said molten material does not have to be melted again. Depending on the casting mould and other conditions, this can be a proportion of molten material of for example up to approximately 5% relative to the quantity of melt introduced into the casting mould.

[0021] In a refinement of the application, during the refilling phase, the casting piston moves back at a speed which is lower than during the preceding time period when the shut-off valve was still open. In other words, in this case the casting piston moves back during the final counter-suction period when the shut-off valve is closed at a speed which is lower than during the initial refilling period when the shut-off valve is open. This selection of the non-constant speed profile of the casting piston during the refilling phase advantageously combines a rapid initial refilling of the casting chamber with melt with a moderately slower subsequent counter-suction operation and the reaching of the casting start position by the casting piston.

[0022] In a refinement of the application, during the refilling phase of the casting process, the previously open shut-off valve is closed as soon as the casting piston reaches the valve switching position by means of its return movement. In the case of a shut-off control valve, this can be performed via an active controlled valve switching at this point in time, and in the case of a non-return valve this can be performed, for example, in which the casting piston stops in the valve switching position and / or the closed casting mould is opened and thus no further melt underpressure is generated in the casting chamber, as a result of which the non-return valve moves into its closed position in an automatically reset manner. Depending on the position of the casting piston (more precisely, depending on the reaching of a specific position by the casting piston, which is referred to as the valve switching position or valve reversal position in the present case), this measure switches the shut-off valve from its open position to its closed position. The closure of the shut-off valve ends the supply of molten material into the casting chamber via the melt inlet channel, and thus the molten material can be counter-sucked into the casting chamber from the melt outlet channel to the desired extent by a further return movement of the casting piston from its valve switching position to its casting start position. In the case of a non-return valve, an undesired opening of the shut-off valve during this time period can be prevented, for example, in which the casting mould is opened before the casting piston moves back from its valve switching position again. In an alternative embodiment, the actuation for reversing the shut-off valve from its open position into its closed position during the refilling phase of the casting process is triggered in a different manner, for example, by means of the passage of a time period (which can be predefined for this purpose) since the start of the refilling phase or since the start of the return movement of the casting piston.

[0023] In a development of the application, the stroke distance between the valve switching position and the casting start position of the casting piston can be variably predefined. This measure makes it possible to react flexibly to different system conditions. The stroke distance between the valve switching position and the casting start position of the casting piston determines the proportion of the final return movement of the casting piston from its valve switching position to its casting start position relative to the overall casting piston stroke, which is given by the distance between the filling end position and the casting start position and thus also by the degree of melt back suction in the melt outlet channel. This stroke distance is naturally greater than zero and less than the overall casting piston stroke (i.e. the stroke distance between the filling end position and the casting start position) and, depending on the requirements and system conditions of the die casting machine, can be set to a corresponding desired value or a value corresponding to the requirements of the respective use case, for example to a value between approximately 2 mm and 20 mm (and more particularly between approximately 4 mm and 8 mm), said value in a corresponding implementation being at most half or at most a third or at most a quarter of the overall casting piston stroke or even less. With an increasing stroke distance between the valve switching position and the casting start position, the degree of back suction of the molten material in the melt outlet channel increases; a shorter stroke distance reduces the amount of molten material back suctioned in the melt outlet channel. For example, the stroke distance between the valve switching position and the casting start position of the casting piston can be selected differently for different casting dies used interchangeably in the die casting machine. In an alternative embodiment, this stroke distance can be predefined in an unalterable manner if no variable adjustment is required.

[0024] In a development of the application, during the refilling phase of the casting process, the casting piston remains in the valve switching position during a pause period before its return movement back to its casting start position. The pause period for the return movement of the casting piston can be used to switch the shut-off valve from its open position into its closed position and, as required, to open the casting mold. Thus, the shut-off valve can be switched during a period in which there is no movement of the melt in the melt inlet channel and thus through the shut-off valve, but the molten material is stationary in the melt inlet channel. The pause period can be appropriately set in terms of its temporal duration (for example depending on the period required to switch the shut-off valve from the open position into the closed position and / or to open the casting mold), it being optionally also possible to provide a pause period of variably changeable specification. In an alternative embodiment, the shut-off valve is switched from its open position into 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.

[0025] In a refinement of the application, during the refill phase of the casting process, the casting mold remains closed at least as long as the shut-off valve remains open. As a result of this measure, the casting chamber is refilled with molten material via the melt inlet channel by means of the return movement of the casting piston, but no appreciable back-suction of molten material from the melt outlet channel takes place, provided the shut-off valve is in its open position. Subsequently, since the casting mold remains closed and contains the casting (which is substantially at least partially solidified at this point in time), no appreciable quantity of air can pass through the casting mold into the melt outlet channel, and thus, in this initial phase of the refill phase, no molten material is back-sucked from the melt outlet channel into the casting chamber. In an alternative embodiment, the casting mold is already open, and / or in any case, its opening begins while the shut-off valve is still open.

[0026] In a development of the application (which is particularly suitable if a shut-off control valve is used as the shut-off valve), during the refill phase of the casting process, the opening of the casting mold begins after the casting piston has reached its casting start position. This procedure causes the back-suction of molten material from the melt outlet channel, essentially not until the casting piston reaches its casting start position. Due to the return movement of the casting piston from the valve switching position, in which the shut-off control valve is closed (when the valve switching position is reached), into the casting start position, the casting piston first builds up a corresponding negative pressure, and after the opening of the casting mold begins, molten material is then back-sucked from the melt outlet channel into the casting chamber to a corresponding extent by the associated negative pressure effect.

[0027] In an alternative development of the application, during the refill phase of the casting process, the opening of the casting mold begins after the casting piston has reached its valve switching position and before the casting piston reaches its casting start position. In this procedure, during the further return movement of the casting piston into its casting start position, molten material can already be back-sucked in the melt outlet channel, or from the melt outlet channel into the casting chamber. It goes without saying that, in corresponding embodiments, the opening of the casting mold can begin at any desired point in time during the return movement of the casting piston from its valve switching position into its casting start position, and in corresponding embodiments, further alternatively, the opening of the casting mold can also begin before the casting piston reaches its valve switching position and the shut-off valve is closed.

[0028] In a further development of the application, in the refill phase of the casting process, as soon as the casting mold reaches a specific casting piston triggered mold opening position at its opening, the casting piston stops in its valve switching position and advances from its valve switching position into its casting start position. In this implementation, the further return movement of the casting piston after its stop in its valve switching position specifically matches the opening process of the casting mold in such a way that the casting piston does not advance to its casting start position until the casting mold is opened to a predefinable extent, which is defined by the set casting piston triggered mold opening position. Thus, the process of the molten material in the melt outlet channel during the last period of the refill phase of the casting process can be further optimized. In an alternative embodiment, the return movement of the casting piston takes place without taking into account the current opening position of the casting mold (assuming that there are no application-related requirements for this).

[0029] In a refinement of the application, in the case that the casting mold is not yet completely closed, the casting piston advances from its casting start position reached during the refill phase of the respective preceding casting process to a prefill position during the initial prefill phase of the mold filling phase of the subsequent casting process, and only after this, the casting mold is completely closed and the casting piston further advances from this prefill position to its filling end position. Thus, air that entered the front region of the melt outlet channel as a result of the back suction of the melt during the refill phase of the respective preceding casting cycle can quickly escape via the mold, which is still completely open or at least still partially open, at the beginning of the respective current casting cycle (before the mold is then completely closed and the actual filling of the mold with the molten material takes place).

[0030] According to a further aspect of the application (claim 9 relates to this further aspect, and this further aspect can be provided in addition or alternatively to the first mentioned aspect of claim 1), during the prefill phase of the casting process starting operation, which precedes the mold filling phase with closed shut-off valve, the casting piston in the casting chamber advances from the starting operation position into a given prefill position and then, upon opening of the shut-off valve, moves back into its casting start position. Depending on the requirements and use case, the casting mold can already be closed before or at the beginning of this prefill phase, or alternatively can remain open during the advance of the casting piston during this prefill phase and only be closed before the return movement of the casting piston or upon opening of the shut-off valve. In the first case, without further measures, it is ensured that no molten material can unintentionally leave via the still open mold during this prefill operation; in the latter case, air pressed out of the melt outlet channel by the prefill process can escape more quickly via the still open mold.

[0031] The specific start-up operating measure constitutes a specific start-up operation of the casting process when starting a cyclic casting operation of the mold casting machine by means of the cyclic casting of a plurality of identical castings by means of a specific casting mold, which follow one another in casting processes or casting cycles, for example, after the assembly of the casting mold or casting tool on the mold casting machine, or after the restart of the mold casting machine with a specific assembled casting mold.

[0032] In other words, the start-up operating casting process constitutes a first casting process or casting cycle for producing the desired castings after the start of the operation of the machine. At such a start of the operation, the molten material is not yet located in the front region of the melt outlet channel, but at most in the rear region of the melt outlet channel, for example, up to the level of the melt filling level in the casting chamber or melt pool, in which the casting vessel comprising the casting chamber is immersed. The specific start-up operating casting process ensures that after such a start of the operation of the machine, when the mold filling phase begins, for the first of the many casting processes following one another, the molten material is already present in the front region of the melt outlet channel as well, in which the casting piston advances from its casting start position in the direction of its filling end position in order to press the molten material into the casting mold.

[0033] For this purpose, before the mold filling phase, in a pre-filling phase of the start-up operating casting process, the casting piston is initially only advanced into a pre-filling position from its start-up operating position in which it is located at this point in time, the shut-off valve remaining closed, as a result of which molten material from the casting chamber can be pressed into the melt outlet channel. The pre-filling position of the casting piston is determined by the fact that when this pre-filling position is reached, the melt outlet channel is filled with molten material to a desired, pre-definable extent. The subsequent opening of the shut-off valve, and the return movement of the casting piston from its pre-filling position into its casting start position, which can correspond to the start-up operating position, or a more forward position of the casting piston in the casting chamber between the operating start position and the pre-filling position, re-fills the casting chamber with molten material via the melt inlet channel to the greatest extent possible from the amount previously pressed into the melt outlet channel from the casting chamber.

[0034] For a subsequent first casting process after the start of the operation of the machine, in this way, there are identical or similar conditions (in terms of the available molten material that has reached the front region of the melt outlet channel) as for the subsequent further casting processes in the starting casting operation of the machine. In other words, in this case, the molten material in the melt outlet channel is already available for this first casting process, has reached its front region, for example, in the entire volume of the riser channel portion and in the volume of the adjacent spout body portion of the melt outlet channel, to the front end region of the spout body, and thus also significantly above the bath level of the specified bath, from which the molten material is fed to the casting chamber. This leads to the advantage that, by virtue of this single prefilling, at the start of the operation, the casting piston stroke required for the subsequent actual mold filling phase can already be significantly reduced for the first casting cycle after the start of the operation. In an alternative embodiment, instead of this prefilling measure, the first casting process is carried out with a casting stroke of the casting piston after the start of the operation of the machine, which corresponds to the casting stroke of the further casting processes in the starting period of the operation.

[0035] In the case of the mold casting machine according to the application, in order to carry out the respective casting processes, in the mold filling phase, the control unit and the shut-off valve are configured to bring the shut-off valve into the closed position and to control the casting piston in the casting chamber from the casting start position to the filling end position in order to press the molten material via the melt outlet channel into the casting mold, and in the subsequent refilling phase, first to bring the shut-off valve into the open position and to control the casting piston to move back to the casting start position in order to feed the molten material via the melt inlet channel to the casting chamber.

[0036] The control unit and the shut-off valve are also configured to bring the shut-off valve again into its closed position still during the refilling phase before the casting piston reaches its casting start position by means of its return movement and to control the casting piston to counter-suck the molten material in the melt outlet channel by means of a further return movement of the casting piston and / or to control the casting piston during the casting processes of the starting operation to advance in the casting chamber from the starting operation position to a prefilling position during a prefilling phase of the starting operation of the casting processes before the mold filling phase with the shut-off valve closed and then to bring the shut-off valve into its open position and to control the casting piston to move back to its casting start position.

[0037] The mold casting machine is therefore particularly suitable for carrying out the mentioned aspects of the operating method according to the application.

[0038] In a refinement of the application, the shut-off valve is in the form of a shut-off control valve, and the control unit is configured to control the shut-off control valve. This allows the shut-off valve to be actively controlled by means of the control unit, in particular in order to bring the shut-off valve into its respective desired open or closed position during the casting process.

[0039] In a development of the application, the mould casting machine comprises a valve actuator actuated by the control unit for actuating the shut-off control valve. The actuator functions as a link element between the control unit and the shut-off valve and can be selected as appropriate depending on the type of control unit and shut-off valve (for example, electric, magnetic, hydraulic, pneumatic or mechanical type). As an alternative, the valve actuating function can be integrated directly in the control unit, for example.

[0040] In a refinement of the application, the shut-off valve is in the form of a non-return valve which is preloaded in its closed position. This constitutes an alternative to the implementation as a shut-off control valve. In this case, the shut-off valve is controlled or actuated depending on the pressure of the molten material acting on it, in particular depending on the melt pressure in the casting chamber.

[0041] In a refinement of the application, the mould casting machine comprises a valve sensor unit for sensing one or more measured variables of the shut-off valve. This can be used, for example, to give the control unit feedback via the valve sensor unit about the current position of the shut-off valve and / or to provide valve diagnostic information which provides information about whether the shut-off valve is operating error-free and / or in which state of use it is and whether it requires maintenance, for example. BRIEF DESCRIPTION OF DRAWINGS

[0042] Advantageous embodiments of the application are shown in the drawings. These and further embodiments of the application are explained in more detail below. In the drawings:

[0043] Figure 1 a schematic longitudinal sectional view showing the part of interest in the current situation of a mould casting machine having a shut-off control valve as shut-off valve,

[0044] Figure 2 a flow chart showing a method of operation of a mould casting machine from Figure 1 starting from the operation,

[0045] Figure 3 a view from Figure 2 during operation of the machine according to the method from Figure 1 starting at the beginning of the mould filling phase of a first casting cycle,

[0046] Figure 4 a view from Figure 3 during the mould filling phase,

[0047] Figure 5 a view from above of the mould filling phase, after the end of the mould filling phase and at the beginning of the refill phase of the first casting cycle, Figure 3

[0048] Figure 6 a view from above of the refill phase, Figure 3

[0049] Figure 7 a view from above of the end of the refill of the casting chamber with melt, after the end of the refill of the casting chamber with melt, Figure 3

[0050] Figure 8 a view from above of the melt back suction operation during the melt refill operation, Figure 3

[0051] Figure 9 a view from above of the end of the first casting cycle, Figure 3

[0052] Figure 10 a view from above of the end of the mould filling phase of the second casting cycle, Figure 3

[0053] Figure 11 a flow chart illustrating the operating method of the mould casting machine from above, Figure 1

[0054] Figure 12 a view from above of the machine during the operation according to the method from above, at the beginning of the initial prefill phase, Figure 11 Figure 3

[0055] Figure 13 a view from above of the machine at a later point in time of the initial prefill phase, with refill of the casting chamber with melt, Figure 12

[0056] Figure 14 a view from above of the machine at the end of the mould filling phase of the first casting cycle (after the initial prefill phase) in the method variant from above, Figure 11 Figure 12

[0057] Figure 15 a flow chart illustrating the operating method of the mould casting machine from above, with the variant of a cycle prefill before the mould filling phase of the respective casting cycle, and Figure 1

[0058] Figure 16 a view from above of the variant of the mould casting machine from above​​​​​​​​​​​​​Figure 1 The die casting machine has a check valve as shut-off valve. DETAILED DESCRIPTION

[0059] Figure 2 Figure 11 Figure 15 Various advantageous variants of the inventive method for operating a die casting machine are illustrated in flow charts. Figure 1 Figures 3-10 Figures 12-14 Figure 16 schematically illustrates the part of a die casting machine according to two embodiments of the invention which is of interest here, which can be operated via the inventive method. The die casting machine can in particular be one of the hot-chamber type for die casting liquid or partially liquid metal melts, such as zinc, lead, aluminum, magnesium, titanium, steel, copper and alloys of these metals. For this purpose, the die casting machine in particular comprises a casting mold 1 with a stationary mold half 1a and a movable mold half 1b, a casting chamber 2, a casting piston 3 arranged in an axially movable manner in the casting chamber 2, a melt inlet channel 4 opening 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.

[0060] In the example of Figure 1 Figures 3-10 Figures 12-14 , the shut-off valve 5 is configured as a shut-off control valve 5 S , i.e. as an actuatable shut-off valve, which is actuated directly by the control unit 7 or, as in the example shown, via an optional valve actuator 16. The valve actuator 16 can be any desired actuator of conventional type, as known to the person skilled in the art for actuating such valves as such. In this respect, depending on the requirements and the use case, the actuator 16 can in particular be an actuator type of conventional electrically operated, hydraulically operated, pneumatically operated or mechanically directly operated type, or an actuator type which is mechanically operated via a lever system or the like. In this respect, depending on the requirements and the use case, the valve actuator 16 can be an actuator type which is operated in a purely binary manner and switches the shut-off valve 5 only between a first open position and a second closed position, or, as an alternative, a proportional actuator type which can open the shut-off valve 5 continuously or in multiple stages, i.e. can also bring the shut-off valve 5 into one or more partially open positions between its fully open position and its fully closed position and hold it there. For this purpose, the valve actuator can comprise, as required, for example a variable end stop which can be adjusted manually or automatically. In the schematic view of Figure 1 Figure 16 a variant of the die casting machine is shown, which differs from the die casting machine in Figure 1 in that the shut-off valve 5 is configured as a check valve 5​​​​​​​​R .

[0061] In the present context, control unit 7 is understood to refer to all control elements of the casting machine for controlling and / or regulating various components of the machine. For this purpose, depending on the system configuration, control unit 7 may contain a single control device in which all control functions are integrated, or multiple separate control devices, each of which controls and / or regulates a specific machine component and preferably has a communication link with each other. Similarly, by convention, control unit 7 may be constructed at least partially in hardware and / or at least partially in software. Purely symbolic and representatively shown to illustrate all the machine control functions of control unit 7 are the actuation arrows 7a, 7b, and 7c, which lead from control unit 7 to the casting mold 1, the casting piston 3, and the valve stem 5d of the shut-off valve 5, respectively, the control functions belonging to these machine components being of primary interest in the present context. For simplicity, the schematic diagram of control unit 7 exists only in… Figure 1 In contrast, it is in Figures 3-10 as well as Figures 12-14 The middle part is omitted.

[0062] Unless otherwise described in more detail below, both the control unit 7 and the rest of the machine components have a structure that is conventional and familiar to those skilled in the art, and therefore requires no further explanation here. In the example shown, such as in... Figure 1 As seen in the image, the casting chamber 2 is formed in the casting container 8 of the casting unit, which is commonly used in this regard. The casting container 8 is immersed in the molten pool 9 located in the conventional melt container 10 during the casting operation.

[0063] In the example shown, the shut-off valve 5 is held on the casting vessel 8 by means of a valve body 5a. Located on the valve body 5a (alternatively, at different locations on the casting vessel 8) are one or more inlet openings, which take the form of an inlet 4a for a melt inlet channel 4, through which molten material 14 can pass from the molten pool 9 into the melt inlet channel 4. Specifically, the shut-off valve 5 is positioned in the melt inlet channel 4 by means of a fixed valve seat 5b and a movable valve closing body 5c. In the example shown, it is possible for the valve closing body 5c to be moved axially against the valve seat 5b and away from the valve seat 5b via the valve stem 5d, so as to close and open the shut-off valve 5 respectively, i.e., in, for example... Figure 1 The opening position VO shown in the figure is similar to, for example, Figure 3The shut-off valve 5 is switched between closed positions VS as shown. In this respect, depending on the valve construction and / or operating conditions, the open position VO can be the fully open or partially open position of the valve. In an alternative embodiment not shown, the shut-off valve 5 is arranged in the casting piston 3, in which case the melt inlet passage 4 is guided via the casting piston 3, specifically through the casting piston 3, as is known per se.

[0064] exist Figure 1 , Figures 3-10 ,as well as Figures 12-14 In the machine's construction, as already mentioned, shut-off valve 5 (i.e., shut-off control valve 5) S The switching movement is executed by the control unit 7 via an optional valve actuator 16. Figure 16 In the machine's structure, shut-off valve 5 (i.e., check valve 5) R The switching movement of the check valve 5 is performed based on the melt pressure in casting chamber 2. R The conventional preload unit 17 is biased in its closed position VS. When the corresponding melt negative pressure exists in the casting chamber 2, the check valve 5... R The negative pressure moves the preloading force of the preloading unit 17 from its closed position VS to its open position VO in opposition to the preloading force. Once the melt negative pressure is no longer present, the check valve 5... R The system automatically returns to its closed position VS under the action of the preloading unit 17. The preloading unit 17 can be implemented, for example, by a preloading spring (such as a compression or tension spring of appropriate design and arrangement). Figure 16 The preload unit 17 in the figure is shown purely by way of example and is schematically represented by a diagram of a tension spring.

[0065] The melt outlet channel 6 is conventionally guided out of the casting chamber 2 via an ascending channel area and / or ascending pipe section 6a formed in the casting vessel 8, and then continues to the area of ​​the mold 1 via the port body 6b. For this purpose, in the same conventional manner, the port body 6b is connected to the port attachment 11 on the inlet side, the ascending pipe section 6a is opened from the casting vessel 8 by means of the port attachment 11, and on the outlet side leads to the area of ​​the sprue cone 12 in the fixed mold half 1a in front of the mold cavity 13, the mold cavity 13 being formed by two mold halves 1a, 1b when the casting mold 1 is closed and designed according to the casting to be produced.

[0066] Figure 2 The method of operation according to the invention is shown in an exemplary embodiment variant at the start of operation of the die casting machine (i.e., after the machine is started in order to cast the desired number of the same castings in a corresponding number of casting processes or casting cycles (following each other)). Figure 1 as well as Figures 3-10 Schematic illustration of according to from Figure 2the machine in different operating phases during the operation of the embodiment variant. In this respect, in the following Figure 1 In the embodiment from Figures 3-10 for the sake of simplicity only, the machine in Figure 16 is shown, but the following related statements apply in the same way to the machine configuration from

[0067] In the initial operating phase B1 of the machine from Figure 2 , the machine is in a basic state at the beginning of the operation. Figure 1 The machine in this operating phase B1 is shown, except that the casting mold 1, which is still open in the basic state, is shown to have already assumed its closed state. The casting piston 3 is correspondingly located in an operating start position BS. The shut-off valve 5 is still open, and thus the molten material 14 is present up to the level of the bath level 9a of the bath 9. In particular, the molten material 14 is also located in the melt outlet channel 6 at the same melt level SH corresponding to the bath level 9a, the molten material 14 extending, for example, as far as the central or front region of the riser channel portion 6a, but not yet as far as the spout body 6b.

[0068] In the subsequent operating phase B2 of the machine from Figure 2 , a first casting cycle is started, and for this purpose the associated mold filling phase is carried out. For this purpose, the casting mold 1 is first closed, and the shut-off valve 5 is brought from its open position VO into its closed position VS and / or is held there, whether the shut-off valve 5 is in the form of a shut-off control valve 5 S controlled by the control unit 7 or in the form of a non-return valve 5 R controlled automatically by the preloading unit 17. Figure 3 The machine at this point in time is shown. Thereafter, the casting piston 3 is advanced from the operating start position BS to a filling end position FP (i.e., downward in each of Figure 1 , Figures 3-10 and Figures 12-14 , with the result that the molten material 14 is pressed from the casting chamber 2 via the melt outlet channel 6 into the casting mold 1. The advancing movement of the casting piston 3 is characterized in the corresponding figures by the associated movement direction arrow GV. The melt flow in the melt outlet channel 6 is symbolically indicated in Figure 4 by the corresponding flow arrow, Figure 4 The machine at the end of the mold filling phase is shown, which can include a so-called subsequent or holding pressure phase in which an additional, increased subsequent or holding pressure is applied on the molten material 14 in the mold 1 in a known manner.

[0069] In the subsequent operating phase B3 of the machine from Figure 2In the operating phase B3 of the machine, the mold filling phase ends and is followed by a refill phase and / or a piston return phase. For this purpose, the shut-off valve 5 is switched from its closed position VS into its open position VO and the casting piston 3 is moved back from its end-of-filling position FP, i.e. upwards in the respective figures. The switching of the shut-off valve 5 is controlled in the case of a shut-off control valve 5 S by the control unit 7 and in the case of a non-return valve 5 R by the melt underpressure, which is generated in the casting chamber 2 as a result of the return movement of the casting piston 3. It should be mentioned here that, naturally, depending on the machine type, the advance or return movement of the casting piston 3 can not be oriented in the vertical direction, as in the example shown, but rather perpendicularly or obliquely relative to the vertical direction. The casting mold 1 remains closed initially and a so-called cooling time elapses, during which the molten material 14 in the mold cavity 13 is cooled, with the result that the molten material 14 solidifies there and forms the desired casting 15. The return movement of the casting piston 3 draws the molten material 14 from the melt pool 9 and thus refills the casting chamber 2 via the melt inlet channel 4. Figure 5 and Figure 6 respectively show the machine at an initial point in time and at a later point in time of the refill phase, during which the molten material 14 from the melt pool 9 refills the casting chamber 2, as is shown by the corresponding flow arrows. The return movement of the casting piston 3 is characterized in the respective figures by the associated movement direction arrow GR.

[0070] In the operating phase B4 of the machine, Figure 2 the refill of the casting chamber 2 with molten material 14 from the melt pool 9 via the melt inlet channel 4 is ended by switching the shut-off valve 5 from its open position VO into its closed position VS. In the case of a shut-off control valve 5 S , this is caused by the control unit 7, while in the case of a non-return valve 5 R , this is caused by stopping the return movement of the casting piston 3 and thus no longer generating a melt underpressure in the casting chamber 2, with the result that the non-return valve 5 R automatically returns to its closed position VS by means of its preloading unit 17. At this point in time, the casting piston 3 is located in the corresponding valve reversal position and / or valve switching position VU. The casting piston 3 is preferably held there for a pause period, the temporary duration of which can in particular be appropriately predefined in such a way that when the pause period has elapsed, the shut-off valve 5 reaches its closed position VS. Alternatively, it is also possible in this respect to select the pause period corresponding to the switching duration of the shut-off valve 5 from its open position VO into its closed position VS or to monitor when the shut-off valve 5 reaches its closed position VS and then to end the pause period or to continue moving the casting piston 3. Figure 7The machine is shown at this point in time. At the same time, the cooling time for the molten material 14 in the casting mold 1 continues in order to form the cast part 15.

[0071] After the pause period has elapsed or the valve switching position VU has been passed, or after the shut-off valve 5 has closed, in the operating phase B5 of the machine Figure 2 , the casting piston 3 is moved further back to the casting start position GS for a subsequent second casting process, so that the melt suction-back process begins. The casting start position GS can be identical to the initial operating start position BS of the casting piston 3 or can differ therefrom to a limited extent. Figure 8 The machine is shown in an intermediate position ZS of the casting piston 3 during this return movement of the casting piston 3 beyond or outside the valve switching position VU.

[0072] In this respect, in the variant with the shut-off control valve 5 S , the shut-off control valve 5 S is held in its closed position VS in a controlled manner and the casting mold 1 has not yet been opened, with the result that a further return movement of the casting piston 3 causes a suction effect on the melt outlet channel 6 via the casting chamber 2. This generates a negative pressure in the region of the sprue cone 12, in which, in the specifically shown example of the mouthpiece body 6b, the molten material 14 has been drawn back slightly from the outlet of the melt outlet channel 6, which is located in front of the melt outlet channel 6, as is indicated by the suction-back arrow 14a in Figure 8 .

[0073] In the variant with the non-return valve 5 R , in contrast to the above procedure selected in the variant with the shut-off control valve 5 S and indicated in Figure 2 with respect to the operating phase B5, at this point in time before the further return movement of the casting piston 3, the casting mold 1 is at least opened to a predefinable extent, the cooling time elapses or is awaited to end. As a result, the melt outlet channel 6 is no longer sealed in a gas-tight manner with respect to the external atmosphere on the side of the casting mold 1, with the consequence that a melt underpressure no longer builds up in the casting chamber 2 during the further return movement of the casting piston 3. The non-return valve 5 R is therefore held in its closed position VS. Instead, the molten material 14, in particular in the front region of the mouthpiece body 6b, is drawn back further away from the region of the sprue cone 12, i.e. a limited suction-back of the molten material from the most front outlet-side region of the melt outlet channel 6 takes place, which prevents the formation of molten droplets in the region of the sprue cone 12.

[0074] The return movement of the casting piston 3 from the valve switching position VU to the casting start position GS preferably occurs at a piston speed that is significantly lower than the piston speed at which the casting piston 3 previously moved back from the filling end position FP to the valve switching position VU.

[0075] 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 melt outlet channel 6. Optionally, it may be assumed that this stroke distance can be variably preset or set by the user.

[0076] Although in the illustrated example, the timing of the shut-off valve 5 switching to its closed position VS to end the refilling of the casting chamber 2 with molten material 14 from the molten pool 9 is associated with the casting piston 3 reaching the valve switching position VU, in an alternative embodiment, the valve switching is triggered in another manner, for example, after a certain period of time has elapsed since the casting piston 3 began its return movement from its filling end position FP.

[0077] exist Figure 2 During operation period B6, the return movement of the casting piston 3 terminates after it reaches its casting start position GS. Meanwhile, with the shut-off control valve 5... S In the variant, the following situation also occurs: the cooling time for the complete solidification of the molded casting 15 in mold 1 has passed, and therefore in this variant, in the case of... Figure 2 In the subsequent operation period B7, it is possible that the casting mold 1 will be opened by correspondingly opening and moving the movable mold half 1b, as shown below. Figure 9 As shown in the figure, Figure 9 The machine is shown at this operating time. The opening of mold 1 makes it possible to immediately release the back suction negative pressure, which was previously controlled by shut-off valve 5. S In the variant, molten material 14 is generated in the region of the gate cone 12, and thus the molten material 14 in the front region of the melt outlet channel 6 (in the specific example shown, in the front region of the port holder body 6b) is drawn back further away from the region of the gate cone 12. Again, the drawing back of the molten material 14 from the foremost outlet side region of the melt outlet channel 6 (i.e., limited back suction) prevents the formation of molten droplets in the region of the gate cone 12, as described above with respect to the check valve 5. R The variations are explained as follows. In both variations, it is then possible that the casting 15 formed in each case is removed after the mold 1 is fully opened.

[0078] Figure 9The presence of the molten material 14 in the front region of the melt outlet channel 6 up to the retraction point RP, which is maintained at a desired sufficient distance AS from the region of the gate cone 12 or the outlet or melting point of the melt outlet channel at which the retracted molten material 14 detaches from the solidified or partially solidified molten material held in the mold 1 and the gate cone 12, is shown by way of example. This makes it possible to reliably prevent the formation of said droplets, Figure 9 The distance AS is merely exaggerated for the sake of clarity and is not shown to scale. The distance AS is for example approximately 5 mm to 100 mm from the gate cone 12 at which the molten droplets would otherwise form, in particular for example between approximately 10 mm and approximately 50 mm, preferably for example between approximately 30 mm and approximately 40 mm, depending on the requirements, the viscosity of the molten material and / or the system configuration of the machine, in particular the diameters of the casting piston, the rising bore and the spout body. As an alternative, the distance AS can also be greater, wherein more air is present in the outlet-side region of the melt outlet channel 6 as the distance AS becomes larger, before the next casting cycle begins.

[0079] However, in any case, the melt outlet channel 6 remains filled with molten material 14 above the melt bath level 9a of the melt bath 9, as a result of which, in the next casting cycle, the molten material 14 in the melt outlet channel 6 does not need to advance from the melt bath level 9a as in the first casting cycle, but rather the melt level SH in the melt outlet channel 6 is already considerably higher than the melt bath level 9a at the beginning of the next casting cycle, and the 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 the operating period B7 according to Figure 3 . Figure 2 .

[0080] To perform the next second casting cycle, the mold 1 is then closed in the operating period B8 according to Figure 2 , and the casting piston 3 is moved from its casting start position GS to its filling end position FP in order to once again press the molten material 14 from the casting chamber 2 via the melt outlet channel 6 into the closed mold 1. Figure 10 The machine is shown at the end of the mold filling phase of this second casting cycle corresponding to the machine state, in Figure 4 , at the end of the mold filling phase of the first casting cycle.

[0081] As in Figure 10In a second casting cycle, which is shown in a comparative manner, the axial movement stroke of the casting piston 3 from the casting start position GS to the filling end position FP is sufficient (smaller than in the first casting cycle for advancing the casting piston 3 from the operating start position BS to the filling end position FP) because for the second casting cycle the molten material 14 is already present significantly above the melt bath level 9a in the melt outlet channel 6. In other words, as Figure 10 In a second casting cycle, which is shown in a comparative manner, the axial movement stroke of the casting piston 3 from the casting start position GS to the filling end position FP is sufficient (smaller than in the first casting cycle for advancing the casting piston 3 from the operating start position BS to the filling end position FP) because for the second casting cycle the molten material 14 is already present significantly above the melt bath level 9a in the melt outlet channel 6. In other words, as Figure 10 In a second casting cycle, which is shown in a comparative manner, the axial movement stroke of the casting piston 3 from the casting start position GS to the filling end position FP is sufficient (smaller than in the first casting cycle for advancing the casting piston 3 from the operating start position BS to the filling end position FP) because for the second casting cycle the molten material 14 is already present significantly above the melt bath level 9a in the melt outlet channel 6. In other words, as

[0082] In other words, the stroke distance HA = FP - GS = FP2 - GS between the filling end position FP and the casting start position GS for the second and each further casting cycle of the corresponding active operating interval of the machine is lower than the corresponding stroke distance HA = FP - BS = FP1 - BS between the filling end position FP and the operating start position GS for the first casting cycle, the difference being determined by the amount of molten material 14 present in the melt outlet channel 6 above the melt bath level 9a after the first casting cycle and before the second casting cycle. The stroke difference is shown in Figure 10 In a second casting cycle, which is shown in a comparative manner, the axial movement stroke of the casting piston 3 from the casting start position GS to the filling end position FP is sufficient (smaller than in the first casting cycle for advancing the casting piston 3 from the operating start position BS to the filling end position FP) because for the second casting cycle the molten material 14 is already present significantly above the melt bath level 9a in the melt outlet channel 6. In other words, as

[0083] This shortening of the stroke length which the casting piston 3 has to travel during the mold filling phase correspondingly allows a shortening of the cycle time, i.e. the duration of the respective casting cycle for the second and each further casting cycle within the operating interval, for example, by up to 5% or 10%. Furthermore, since the molten material 14 remains in the melt outlet channel 6 above the melt bath level 9a between the casting cycles, the air fraction to be displaced in the outlet side portion of the melt outlet channel 6 is reduced, so the air incorporated in the castings can also be reduced, which benefits the quality of the castings. Furthermore, the shortening of the casting piston stroke makes it possible to reduce the wear effects of the casting piston and the casting chamber caused by the casting piston movement in the casting chamber.

[0084] The mold filling phase and the subsequent refilling phase of the second casting cycle then take place in the same manner as explained above for the first casting cycle, reference being made to this. This is shown in Figure 2The return from the operating phase B8 to the operating phase B3 is symbolized by a return arrow.

[0085] In the exemplary embodiment shown with the shut-off control valve 5 as shut-off valve 5 S , the casting mold 1 remains closed in the corresponding program during the entire refilling phase until the casting piston 3 reaches its casting start position GS as starting position for the next casting cycle. The fact that the mold 1 is opened only at this point in time then leads to the mentioned immediate back-suction effect. In an alternative program, the casting mold 1 can be opened earlier and thus the back-suction effect can be configured more uniformly in terms of time and / or attenuated. In this respect, in a corresponding operating variant, the casting mold 1 remains closed at least as long as the shut-off control valve 5 S is still open in order to refill the casting chamber 2 with molten material 14 from the melt pool 9. When the casting piston 3 reaches its valve switching position VU and the shut-off control valve 5 is closed thereby, the casting mold 1 is opened at an earlier or later point in time of the further return movement of the casting piston 3 from the valve switching position VU into the casting start position GS, depending on requirements. As soon as the opening of the mold 1 begins, more air can pass via the outlet of the melt outlet channel 6 into the front region of the melt outlet channel 6 and thus attenuate and / or reduce the negative pressure effect there.

[0086] In a further operating variant, the casting piston 3 remains in the valve switching position VU and the opening of the casting mold 1 then begins after the cooling time has elapsed. As soon as the casting mold 1 reaches a determined casting piston triggered mold opening position upon its opening, which can be predefined in a variable or permanent manner, for example, when the movable mold half lb is moved away from the stationary mold half la by a corresponding predefined travel length, the casting piston 3 is further moved from its valve switching position VU back to its casting start position GS. In this respect, the casting piston triggered mold opening position is chosen such that the entry of air at the melt outlet channel 6 via the sprue cone 12 or the spout nozzle is possible. This can then lead to a back-suction of the molten material 14 in the most front region of the melt outlet channel 6 in a relatively uniform variant over time without a sudden reduction of the negative pressure. This operating variant is for example also particularly suitable for the machine variant of Figure 16 with the shut-off control valve 5 as shut-off valve 5 R . Then, as soon as the mold 1 is opened in this way to such an extent that air can enter at the melt outlet channel 6, no melt negative pressure is generated in the casting chamber 2 by the further return movement of the casting piston 3 and the shut-off control valve 5 R automatically remains in its closed position VS by the action of the preloading unit 17.

[0087] Figure 11This illustrates yet another advantageous embodiment variation of the method according to the invention for operating a die casting machine, specifically relating to the performance of a corresponding first casting cycle after the start of machine operation, and primarily suitable for having a shut-off control valve 5 as a shut-off valve 5. S Machine variants. For this purpose, according to Figure 2 The initial operating period B1, this operating variant starts from the machine's basic state again at the beginning of the operating variant. However, with Figure 2 Comparison of operational variations, in Figure 11 In the operational variant, the start operation casting process (i.e., the specific first casting cycle) is now executed, where the initial pre-filling stage is performed upstream of the mold filling stage.

[0088] For this purpose, in Figure 11 During operation period B2a, this initial pre-filling stage is therefore achieved by advancing the casting piston 3 only as far as the start of operation position BS after the shut-off control valve 5 is closed and the mold 1 is closed. Figure 12 The initial prefill position VP is shown in the figure. Figure 12 The machine is shown during operation period B2a. Therefore, the melt outlet channel 6 is pre-filled above the molten pool surface 9a of the melt pool 9 with molten material 14, preferably all the way to the pre-filling point VA in the front region of the melt outlet channel 6 or in the gate body 6b. As a result, the pre-filling point VA is only at a relatively small distance DS from the melt outlet channel 6 to the outlet in the mold 1 or from the gate cone 12. This distance DS can approximately correspond to the distance AS between the back suction point RP and the outlet in the mold 1, for example, at a distance AS of... Figure 2 In the operational variations and such Figure 9 As shown, the molten material 14 exists after the back suction in the melt outlet channel 6 as explained above. Alternatively, the distance DS may also be slightly or significantly different from the distance AS.

[0089] After that, Figure 11 During operation period B2b, a predefined time period is waited until the overpressure generated during the pre-filling process is reduced by the compressed air in mold cavity 13. Then, in Figure 11 During operation period B2c, the shut-off control valve 5 reverses from its closed position VS to its open position OS, and the casting piston 3 moves from the pre-filled position VP back to its casting start position GS. Therefore, molten material is drawn from the molten pool 9 or refilled into the casting chamber 2 via the melt inlet channel 4, as in... Figure 13 The relevant flow arrows indicate this. Figure 13 The machine is shown at the end of the operation period B2c, at which point the casting piston 3 reaches its casting start position GS again.

[0090] The melt refilling process can be accompanied by some further back suction of the molten material 14 in the melt outlet channel 6, since an amount of air is still present in the closed mold 1 and the mold 1 can not yet be completely air-tight. Thus, the prefill point VA (up to which the prefilling of the molten material 14 in the melt outlet channel 6 exists) can accordingly be slightly shifted back, as shown in Figure 13 by the associated backflow arrows in the melt outlet channel 6, and the prefill point VA is located further back in the spout body 6b compared to Figure 12 However, the molten material 14 remains prefilled in the melt outlet channel 6 significantly above the melt bath level 9a of the melt bath 9, as far as the front region of said melt outlet channel.

[0091] In principle, for a machine variant with a check valve 5 R as shut-off valve 5, a similar prefilling process is also possible. In this case, the check valve 5 R remains closed by means of the melt pressure in the casting chamber 2 while the casting piston 3 is advanced from its operating start position BS to its prefilling position VP. When subsequently providing: an appropriate reduction of the overpressure in the operating phase B2b (as mentioned above), and then providing: a back suction of the molten material in the melt outlet channel 6 is sufficiently impeded or slowed down, for example by means of an actuatable closure in the melt outlet channel 6 and / or by means of a sufficiently fast return movement of the casting piston 3, the return movement of the casting piston 3 from the prefilling position VP to its casting start position GS can generate a negative pressure in the casting chamber 2 sufficient to open the check valve 5 R so that in this case, the molten material can also be sucked or refilled from the melt bath 9 into the casting chamber 2 via the melt inlet channel 4.

[0092] After the end of this initial prefilling phase, the mold filling phase of the first casting cycle is carried out according to the operating phase B2d Figure 11 For this purpose, the shut-off control valve 5 is again turned into its closed position VS, or the check valve 5 R again automatically closes after the melt negative pressure in the casting chamber 2 has disappeared, and the casting piston 3 is advanced from its casting start position GS to the filling end position FP, as a result of which the molten material 14 is again pressed from the casting chamber 2 into the casting mold 1 (in particular the casting cavity 13) via the melt outlet channel 6.

[0093] Compared to a first casting cycle without prefilling (as in Figure 2compared to the operation variant of the filling phase of the mold for the first casting cycle, the initial pre-filling has resulted in a shortening of the stroke distance HA = FP - BS between the filling end position FP and the operation start position BS. This shortening of the stroke for the first casting cycle is achieved analogously to the shortening of the stroke explained above, in that Figure 2 In the operation variant of the filling phase of the mold for the first casting cycle, this is achieved only for the further casting cycles, by cutting off the premature closing of the control valve 5 in the refill phase of the preceding casting cycle before the casting start position GS is reached and before the further return movement of the casting piston 3 to the casting start position GS. Figure 14 The machine is shown in the operating period B2d at the end of the mold filling phase of the first casting cycle, in which the filling end position FP is shortened to the position FP 1V (For the variant with initial pre-filling), the position FP 1V lies behind the filling end position FP1 in the first casting cycle (for the operation variant of the filling phase of the mold for the first casting cycle without pre-filling by stroke deviation HD1 = FP1 - FP 1V (For the operation variant of the filling phase of the mold for the first casting cycle with pre-filling from Figure 2 ). In other words, in this operation variant, as a result of the pre-filling measure, there is a shortened casting stroke for the mold filling operation already performed for the first casting cycle compared to the operation variant of the filling phase of the mold for the first casting cycle without pre-filling. Figure 2

[0094] Thus, in the operation variant of Figure 11 , the properties and advantages mentioned above with regard to the shortening of the stroke in the second casting cycle and in the further casting cycles in the operation variant of Figure 2 have been achieved for the first casting cycle by the operation variant of Figure 11 .

[0095] In addition to the operating period B3 there, the further progress of the first casting cycle can correspond to the progress of the operation variant of Figure 2 . As an alternative, Figure 11 the first casting cycle in the operation variant of may continue according to any desired conventional operation method.

[0096] Figure 15 The operation method of Figure 2 is shown in an advantageous variant with regard to the performance of the second casting cycle and the further casting cycles. In this method variant, the respective mold filling phase from the second casting cycle contains a pre-filling phase. In this regard, the operating situation at the end of the operating period B7 proceeds as shown in Figure 9 . In contrast to the operation variant of the operating period B8 according to Figure 2 , in the operation variant of the filling phase of the mold for the first casting cycle, this is achieved only for the further casting cycles, by cutting off the premature closing of the control valve 5 in the refill phase of the preceding casting cycle before the casting start position GS is reached and before the further return movement of the casting piston 3 to the casting start position GS. Figure 15In the operational variation, during the forward operation period B8a with the casting piston 3, without waiting for the mold 1 to fully close, but while the mold 1 is still open, the casting piston 3 has already advanced from the casting start position GS to the pre-fill position VP2 for the second casting cycle. This pre-fill position VP2 is also referred to as the cycle pre-fill position VP2 in the current case, to distinguish it from the previous one. Figure 11 Operational variations and Figure 12 The diagram shows the prefill position VP at the end of the initial prefill stage before the first casting cycle.

[0097] This cyclic prefilling measure allows the molten material 14 (which was previously based on...) to... Figure 2 During the operation period B5 to B7 of the modified operation (away from the outlet back suction of the melt outlet channel 6), the flow proceeds again in the direction of the outlet of the melt outlet channel 6, and thus it is possible to prefill the melt outlet channel 6 to a greater extent, and the air in the front end region of the melt outlet channel 6 can escape unimpeded through the mold 1 that has not yet been closed.

[0098] exist Figure 15 During operation period B8b, the casting piston 3 remains in the pre-fill position of the cycle until the mold 1 is fully closed. Subsequently, the remaining sequence of the mold filling phase of the associated second or subsequent casting cycle proceeds according to... Figure 15 The operation is performed during period B8c. For this purpose, the casting piston 3 advances from its pre-fill position to the end-fill positions FP and FP2 respectively, so as to press the molten material 14 from the casting chamber 2 into the closed mold 1 or its casting cavity 13 via the pre-filled melt outlet channel 6. The operating state of the machine at this point in time corresponds to... Figure 10 The operational status, or corresponding to Figure 2 The operation period B8 ends. In other words, in Figure 15 In the operational variation, after the mold filling stage ends, at the end of operation period B8c, a refilling stage continues, and from... Figure 2 The additional steps begin with operation period B3.

[0099] Pre-filling the mold at the beginning of the second and subsequent casting cycles allows for an additional reduction in the cycle time and air fraction in the produced castings. In the corresponding optimized program, Figure 2 , Figure 11 as well as Figure 15 The operational variations can be combined to achieve the following effects: For the corresponding operational interval of the die casting machine, at the start of the operation, firstly, the initial prefilling is based on... Figure 11 The modification is performed in the casting chamber using melt refilling, followed by the remainder of the first casting cycle according to... Figure 2the operation variant according to the invention is possible, with or without additional combinations with the cycles according to the invention Figure 15 the operation variant according to the invention is possible, with or without additional combinations with the cycles according to the invention Figure 15 the operation variant according to the invention is possible, with or without additional combinations with the cycles according to the invention Figure 11 the operation variant according to the invention is possible, with or without additional combinations with the cycles according to the invention Figure 2 the operation variant according to the invention is possible, with or without additional combinations with the cycles according to the invention

[0100] As shown, the die casting machine according to the invention is configured for carrying out the operating method according to the invention. In particular, in this respect, the control unit 7 is correspondingly configured to carry out the respective casting process, for which purpose, in the mold filling phase, the control unit 7 controls the casting piston 3 in the casting chamber 2 to advance from the casting start position GS to the filling end position FP in order to press the molten material 14 via the melt outlet channel 6 into the casting mold 1, and for this purpose, in the examples according to Figure 1 , Figures 3-10 and Figures 12-14 the shut-off control valve 5 S is controlled directly or via a valve actuator 16 into its closed position VS, while in the machine configuration according to Figure 16 the shut-off control valve 5 R is automatically held in its closed position VS under the influence of a preloading unit 17 and the melt pressure in the casting chamber 2. The control unit 7 is also configured to control the casting piston 3 to move back to the casting start position GS during the subsequent refill phase in order to supply the molten material 14 via the melt inlet channel 4 to the casting chamber 2, and for this purpose, in the machine configurations according to Figure 1 , Figures 3-10 and Figures 12-14 the shut-off control valve 5 S is first controlled into its open position VO, while in the machine configuration according to Figure 16 the shut-off control valve 5 R is brought into its open position VO by means of the negative pressure in the casting chamber 2.

[0101] The control unit 7 and the shut-off valve 5 can also be configured to switch the shut-off valve 5 again into its closed position VS (still in the refilling phase) before the casting piston 3 reaches its casting start position GS in dependence on its return movement, and to control the casting piston 3 in return movement again to counter-pump the molten material 14 in the melt outlet channel 6. As an alternative or in addition, the control unit 7 can also be configured to control the casting piston 3 at the start of the casting process (i.e. the first casting cycle) to advance in the casting chamber 2 from the operating start position BS to a pre-filling position VS during a pre-filling phase of the operating casting process before the mold filling phase at which the shut-off valve 5 is closed, followed by the provision that the shut-off valve 5 enters its open position VO and by the provision that the casting piston 3 is controlled to move back to its casting start position GS.

[0102] As in the shown example, the die casting machine can optionally have a valve sensor unit 18 for sensing one or more measured variables of the shut-off valve 5. The measured values detected by the valve sensor unit 18 with respect to the respective measured variables can be supplied to the control unit 7 as required in order to provide it with control feedback about the current position of the shut-off valve 5. In addition or as an alternative, the measured values can be used for diagnostic evaluation in order to diagnose the current state of the shut-off valve 5 (for example in terms of any faults) and to identify when the shut-off valve 5 requires maintenance.

[0103] Depending on the requirements and the use case, the valve sensor unit 18 can comprise one or more sensors, including optional limit switches with or without a link to the control unit 7, as already mentioned, the control unit 7 can be the entire machine control system of the die casting machine or a part of this machine control system. The valve sensor unit 18 can be configured to measure the stroke of the shut-off valve, for example, in order to derive error diagnoses therefrom, for example, whether the valve closure body 5c is torn off during the valve closure movement and whether the valve stem 5d exceeds its intended position, and / or whether the valve closure body 5c actually reaches its closed position or stops prematurely. The valve sensor unit 18 can also optionally comprise a force sensor in the valve stem 5d, which measures the closure force or contact pressure and / or the opening force of the valve closure body 5c for diagnostic monitoring. In the case of an electric or hydraulic and / or pneumatic valve drive, for example, via the valve actuator 16, the valve sensor unit 18 can also comprise a flow sensor or a pressure sensor of conventional design for this monitoring purpose, whether or not with a link to the control unit 7.

[0104] As clarified by the exemplary embodiments shown and the further exemplary embodiments explained above, the present application provides an advantageous method for operating a die casting machine which makes possible a short casting cycle time, a lower air fraction in the castings, a low wear tendency of the casting piston and the casting chamber in dependence on a reduced casting piston stroke, and / or the avoidance of the formation of melt droplets in the region of the sprue cone. The present application also provides a die casting machine which is suitable for carrying out this operating method, which can in particular be of the hot-chamber type.

Claims

1. A method for operating a die casting machine having a casting mold (1), a casting chamber (2), a casting piston (3) arranged in an axially movable manner in the casting chamber, a melt inlet channel (4) opening into the casting chamber, a shut-off valve (5) in the melt inlet channel, and a melt outlet channel (6) leading from the casting chamber to the casting mold, wherein in order to execute a corresponding casting process, in a mold filling phase, with the shut-off valve closed, the casting piston in the casting chamber is advanced from a casting start position GS to a filling end position FP and, as a result, molten material (14) is pressed via the melt outlet channel into the casting mold, and in a subsequent refilling phase, the casting piston is moved back to the casting start position and, as a result, with the shut-off valve open, the casting chamber is supplied with molten material via the melt inlet channel, characterized in that in the refilling phase of the casting process, the previously open shut-off valve (5) is closed before the casting piston (3) reaches its casting start position GS with its return movement and, as a result of a further return movement of the casting piston, molten material (14) in the melt outlet channel (6) is sucked back.

2. The method as claimed in claim 1, further characterized in that, in the refilling phase, the casting piston is moved back at a speed which is lower in the time period when the shut-off valve is closed than in the previous time period when the shut-off valve was still open, and / or in the refilling phase of the casting process, the previously open shut-off valve is closed as soon as the casting piston reaches a valve switching position VU with its return movement.

3. The method as claimed in claim 2, further characterized in that the stroke distance between the valve switching position and the casting start position of the casting piston can be variably predefined, and / or in the refilling phase of the casting process, the casting piston is held in the valve switching position during a pause period before it moves back again to its casting start position. in the refilling phase of the casting process, the casting mold remains closed at least as long as the shut-off valve is still open. in the refilling phase of the casting process, the opening of the casting mold is started after the casting piston reaches its casting start position. in the refilling phase of the casting process, the opening of the casting mold is started after the casting piston reaches its valve switching position and before the casting piston reaches its casting start position. in the refilling phase of the casting process, the casting piston is stopped in the valve switching position of the casting piston and, once the casting mold reaches a given casting piston triggered mold opening position with the casting mold open, the casting piston is advanced from the valve switching position of the casting piston to the casting start position of the casting piston. ​ ​ ​ 4. The method of any one of claims 1 to 3, further characterized by, ​ 5. The method of any one of claims 1 to 3, further characterized by, ​ 6. The method of any one of claims 1 to 3, further characterized by, ​ 7. The method of claim 6, further characterized by, ​ 8. The method of any one of claims 1 to 3, further characterized by, The casting piston advances from a casting start position of the casting piston to a prefill position before the casting mold has been completely closed, the casting piston reaches the casting start position during the refill phase of a respective preceding casting process and the prefill position is a position of the casting piston during an initial prefilling period of the mold filling phase of a subsequent casting process, and only thereafter the casting mold is completely closed and the casting piston advances to a filling end position of the casting piston.

9. The method of any one of claims 1 to 3, further characterized by, During a prefill phase of a start operation casting process before the mold filling phase with the shut-off valve (5) closed, the casting piston (3) in the casting chamber (2) advances from a start operation position BS to a prefill position VP and then the shut-off valve opens and the casting piston moves back to its casting start position.

10. A method for operating a die casting machine having a casting mold (1), a casting chamber (2), a casting piston (3) arranged in an axially movable manner in the casting chamber, a melt inlet channel (4) opening into the casting chamber, a shut-off valve (5) in the melt inlet channel, and a melt outlet channel (6) leading from the casting chamber to the casting mold, wherein, in order to carry out a respective casting process, during a mold filling phase with the shut-off valve closed, the casting piston in the casting chamber advances from a casting start position GS to a filling end position FP and, as a result, molten material (14) is pressed via the melt outlet channel into the casting mold, and during a subsequent refill phase, the casting piston moves back to the casting start position and, as a result, with the shut-off valve open, the casting chamber is supplied with molten material via the melt inlet channel, characterized in that During a prefill phase of a start operation casting process before the mold filling phase with the shut-off valve (5) closed, the casting piston (3) in the casting chamber (2) advances from a start operation position BS to a prefill position VP and then the shut-off valve opens and the casting piston moves back to its casting start position.

11. A die casting machine comprising a casting mold (1), a casting chamber (2), a casting piston (3) arranged in an axially movable manner in the casting chamber, a melt inlet channel (4) opening 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, ​ wherein In order to perform the respective casting process, in a mold filling phase, the control unit (7) and the shut-off valve (5) are configured to bring the shut-off valve into a closed position VS and to control the casting piston (3) in the casting chamber (2) from a casting start position GS to a filling end position FP in order to press molten material (14) via the melt outlet channel (6) into the casting mold (1), and in a subsequent refilling phase, first to bring the shut-off valve into an open position VO and to control the casting piston to move back into the casting start position in order to supply molten material to the casting chamber via the melt inlet channel, characterized in that the control unit (7) and the shut-off valve (5) are further configured to bring the shut-off valve (5) again into its closed position VS and to control the casting piston to back-purge molten material (14) in the melt outlet channel (6) by means of a further return movement of the casting piston before the casting piston (3) reaches its casting start position GS by means of its return movement, and / or the control unit (7) and the shut-off valve (5) are further configured to control the casting piston (3) during a casting process starting operation to advance in the casting chamber (2) from a start operation position BS to a pre-filling position FP before the mold filling phase with the shut-off valve (5) closed, a pre-filling phase of the casting process starting operation, and then to bring the shut-off valve to its open position VO and to control the casting piston to move back to its casting start position GS.

12. The moulding machine according to claim 11, further characterized in that The shut-off valve is in the form of a shut-off control valve, and the control unit is configured to control the shut-off control valve.

13. The moulding machine according to claim 12, further characterized by a valve actuator (16) actuated by the control unit for actuating the shut-off control valve.

14. The mold casting machine of claim 11, further characterized by, The shut-off valve is in the form of a check valve, which is preloaded in its closed position.

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

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