EP3928889A1 - Pressure die casting machine and method of operation - Google Patents

Abstract

1. Die casting machine and operation procedure.2.1. The invention relates to a die casting machine with a casting mold (1), a casting chamber (2), a casting plunger (3) arranged to be axially movable in the casting chamber, a melt inlet channel (4) leading into the casting chamber, a shut-off valve (5) in the melt inlet channel, a melt outlet channel (6) leading from the casting chamber to the casting mold and a control unit (7) for controlling the casting plunger and a method for operating such a die casting machine.2.2. In the die casting machine according to the invention, the control unit (7) and the shut-off valve (5) are set up, according to one aspect of the invention, to bring the shut-off valve (5) into a closed position and the casting piston (3) in the mold filling phase in order to carry out a respective casting process to control the casting chamber (2) to advance from a casting start position to a filling end position in order to press melt material (14) via the melt outlet channel (6) into the casting mold (1), and in a subsequent refilling phase to first bring the shut-off valve into an open position and to control the casting plunger to move back into the casting start position in order to supply melt material to the casting chamber via the melt inlet channel, and to control the shut-off valve back into its closed position before the casting plunger has reached its casting start position as a result of its return movement, and to control the casting plunger to suck back melt material in the melt outlet channel through the further retraction ng of the plunger to control.2.3. Use e.g. in hot chamber die casting machine technology.

Description

The invention relates to a die casting machine with a casting mold, a casting chamber, a casting piston arranged axially movable 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 respective casting process in a mold filling phase, the casting piston in the casting chamber with the shut-off valve closed is moved from a casting start position to a filling end position, thereby pressing melt material into the casting mold via the melt outlet channel and in a subsequent refilling phase, the casting piston is moved back into the casting start position and, as a result, melt material is fed back to the casting chamber via the melt inlet channel with the shut-off valve open.

Such, generic and similar die casting machines and associated operating methods are generally used to cast a specific component, also called a cast part, in the respective casting process or casting cycle. The present die-casting machine, hereinafter also referred to as the machine for short, and the present operating method are particularly suitable for metallic die-casting, e.g. 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 in particular be a hot chamber die casting machine. In this embodiment, the casting chamber is formed in a casting container which is immersed in a melt bath which is held ready by a melt container.

In the mold filling phase of the casting process, melt material located in the casting chamber is pressed out of the casting chamber via the melt outlet channel through the forward movement of the casting piston under pressure into a mold cavity formed by the casting mold in order to form a corresponding casting. The casting mold here usually contains a fixed and a movable mold half, the between them form the mold cavity, which is also called the mold cavity or, synonymous with the casting mold forming this, for short. In typical implementations, the melt outlet channel comprises a riser pipe area of a casting container containing the casting chamber on the inlet side and a mouthpiece body attached to the casting container on the outlet side, i.e. after leaving the casting chamber, the melt material reaches a melt inlet in the area directly in front of the mold cavity via the riser pipe area and the mouthpiece body there is typically a so-called sprue cone.

In the refilling phase, the casting piston is moved back from its filling end position to its starting position, i.e. the casting start position, and the return movement of the casting piston refills the melt material into the casting chamber via the melt inlet channel. The refill phase can therefore also be referred to as the piston return phase.

In a corresponding machine type, as it is particularly suitable for the present die casting machine, the melt outlet channel leads away from the casting chamber separately from the melt inlet channel, ie the melt inlet channel and melt outlet channel form two separate guide channels for the melt material with a casting chamber inlet at which the melt inlet channel opens into the casting chamber. and a casting chamber outlet separate from this, at which the melt outlet channel opens out from the casting chamber. This configuration facilitates independent control of the melt flows in the melt inlet channel and in the melt outlet channel, with the melt flow in the melt inlet channel in particular being able to be controlled by the shut-off valve located there.

Depending on the system design, a check valve operated purely by melt pressure or an actively controllable shut-off valve can be used as the shut-off valve. The latter is referred to here as a shut-off control valve and is controlled by the control unit. In these generic die-casting machines and associated operating methods, the shut-off control valve is usually kept closed during the entire mold filling phase and kept open during the entire refilling phase. Compared to a simple check valve, as an actively controllable or controllable shut-off valve, it offers the possibility of regulating the melt flow in the melt inlet channel if necessary, to influence or regulate independently of the melt pressure conditions in the casting chamber or in the melt inlet channel.

Depending on the system design, the control unit comprises a single control device in which all control functionalities of the die casting machine are integrated, or several individual control devices which each control or regulate specific machine components and are preferably in communication with one another. As usual, the control unit can be implemented at least partially in hardware and / or at least partially in software. In the present case, the control unit controls in particular the casting piston, more precisely its movement, and optionally one or more further machine components such as in particular the shut-off control valve if the shut-off valve is implemented by such a valve.

The patent specification EP 0 576 406 B1 discloses such a procedure for a system with a casting piston of the displacement type, as it is known as an alternative to a casting piston of the slide type, and with a shut-off control valve arranged directly at a confluence of the melt inlet channel into the casting chamber. In the case of the slide type, the piston external dimension of the casting piston corresponds to the internal dimension of the casting chamber, the piston being sealed off from the casting chamber wall. As a result, in this case the casting piston pushes the melt material in the casting chamber completely forwards as it moves forward, thereby exerting the necessary pressure on the melt material in order to press the same into the mold cavity. In the displacement type, the external dimension of the casting piston is suitably smaller than the internal dimension of the casting chamber, so that the casting piston dips into the melt material of the casting chamber as it moves forward. The pressure on the melt material is brought about in this case by the displacement effect of the plunger volume immersed in the melt material.

The disclosure document DE 32 48 423 A1 also discloses a generic die casting machine and an associated operating method, where a casting piston with a piston of the displacement type and a pressurized gas that can be additionally supplied to the casting chamber is used and the shut-off control valve is located upstream in a casting container containing the casting chamber with the respective fluidic distance the casting chamber and downstream of an inlet into the casting container in the melt inlet channel. The shut-off control valve is kept closed during the mold filling phase. During the refilling phase, the shut-off control valve is opened and a certain amount of pressurized gas is fed into the casting chamber in order to prevent the formation of a vacuum in the casting chamber and the splashing of the melt that has been torn in on the casting piston part behind the piston before the opening of the shut-off control valve and to prevent the gas pressure in bias the casting chamber to a certain extent above atmospheric pressure. After the required amount of melt has been supplied during the refill phase, the shut-off control valve is closed again.

In die casting, for economic reasons the shortest possible cycle time, ie duration of a particular casting process, and for reasons of the quality of the cast part, the lowest possible amount of air in the cast part, ie a minimum air porosity of the cast part, is sought. In order to take account of the last-mentioned aspect in particular, the patent specification EP 1 284 168 B1 It is suggested that at the beginning of the mold filling phase or before the actual mold filling phase in a pre-filling phase, while the mold is still open, the casting piston should be moved so far that the melt material fills the riser area and the mouthpiece body area, before the mold is closed and the casting piston continues to carry out the actual mold filling phase is moved forward. The casting piston there is of the slide type and functions itself as a shut-off device by releasing it during the refill phase through its return movement behind the casting chamber inlet and shutting it off during the mold filling phase through its forward movement beyond the casting chamber inlet.

Further aspects to be considered in general with die casting machines of the present type include minimizing the wear effects of the opposing walls of the casting piston and casting chamber due to the stroke movement of the casting piston in the casting chamber, especially if it is of the slide type, and preventing undesirable melt droplets from forming in the area of the sprue cone , which usually forms the entry-side interface of a mold-side, exit-side melt channel structure opening into the mold cavity with a gate for coupling to the mouthpiece body.

The technical problem underlying the invention is the provision of a die-casting machine and an associated operating method of the type mentioned at the outset, which have advantages over the prior art explained above, in particular with regard to achieving relatively short casting cycle times and / or a relatively low air porosity in the casting and / or with regard to a relatively low tendency to wear the casting piston and casting chamber and / or avoiding the formation of melt droplets in the sprue cone area.

The invention solves this problem by providing a die-casting machine operating method with the features of claim 1 or 9 and a die-casting machine with the features of claim 10 or 11. Advantageous further developments of the invention are specified in the subclaims.

According to one aspect of the operating method according to the invention, to which claim 1 is directed, the previously opened shut-off valve is closed in the refill phase of the casting process before the casting piston has reached its casting start position through its return movement, and the further return movement of the casting piston sucks melt material back into the melt outlet channel , ie partially sucked back from the melt outlet channel into the casting chamber. In the case of a shut-off control valve, the shut-off valve can be closed actively by the control unit, in the case of a check valve, for example, by a pretensioning element, such as a pretensioning spring, which pretensions the valve into its closed position. In this operating method, the shut-off valve is therefore initially open in an initial section of the refill phase when the casting piston moves back so that melt material is refilled into the casting chamber via the melt inlet channel, while the shut-off valve is closed in the remaining section of the refill phase, so that the further Moving back the casting piston melt material can be sucked back in the melt outlet channel. To open the shut-off valve is controlled in the implementation as a shut-off control valve by the associated control unit in its open position, in the implementation as a check valve by the melt vacuum in the casting chamber.

This procedure according to the invention advantageously combines a required refilling of the casting chamber with melt material via the melt inlet channel with a partial back suction of melt material in the melt outlet channel. After the filling phase, the non-solidified melt material in the melt outlet channel is preferably not completely sucked back down to a melt fill level present in the casting chamber or an upstream melt pool, but can be set or predefined by a corresponding selection of the closing time of the shut-off valve or the associated position of the casting piston Measure up to a front area of the melt outlet channel in this and therefore does not have to be moved forward in the melt outlet channel up to this filling level in a next casting process.

Due to these properties, this procedure according to the invention offers several advantages. In this way, the cycle time for the successive casting processes can be shortened. The stroke of movement of the casting piston in the casting chamber can also be reduced, so that the associated wear effects can be minimized. The wear on parts of the casting chamber and the casting piston that are subject to wear, including conventional piston rings, is also significantly reduced by this procedure according to the invention, for example in comparison with conventional systems in which the casting piston acts as a shut-off device for the melt inlet channel, because the movement of the The negative pressure occurring in the casting piston can be kept noticeably lower if necessary, in that the shut-off valve is suitably controlled or adjusted. Since the melt outlet channel can remain largely filled with melt material between successive casting processes, there is correspondingly little air in the front section of the melt outlet channel at the beginning of the respective casting process, whereby the air porosity of the cast part can be significantly reduced, which accordingly can significantly improve the quality of the cast part manufactured .

By sucking back non-solidified melt material in the melt outlet channel to a controllable or controlled extent, ie in a controllable or predeterminable amount, an undesired formation of a melt droplet in the area of the sprue cone of the die casting machine or its molding tool, ie on the sprue or at the transition or outlet of the melt outlet channel or a section forming it on the outlet side Prevent the mouthpiece body to a subsequent mouthpiece nozzle or mouthpiece tip in that the melt material is sucked back more or less far into the melt outlet channel away from the exit area of the melt outlet channel there. The amount of back suction can be suitably set or specified, ie selected, depending on the requirements and the circumstances of the die casting machine, expediently in such a way that on the one hand the said melt droplet formation is reliably avoided and on the other hand the melt material is still relatively far forward, i.e. preferably in a front or area far to the front, remains in the melt outlet channel.

In advantageous implementations, the melt material is sucked back so far that, on the one hand, it remains in the melt outlet channel up to a front or relatively far forward area of the melt outlet channel, ie it is there, but on the other hand with a certain, relatively small distance of, for example, approx 100mm to the sprue cone or outlet of the melt outlet channel, at which the melt droplet would otherwise form, is located behind it, in particular at a distance from this outlet or, depending on the system in question, to a melting point located shortly behind this outlet, at which the even more liquid melt from the previously solidified or partially solidified melt in the sprue cone or in the mold, for example between approx. 10 mm and approx. 50 mm, preferably between approx. 30 mm and approx. 40 mm, depending on requirements, the viscosity of the melt material and / or system design of the machine. In corresponding, typical versions of the die casting machine, the required return stroke of the casting piston from the casting piston position to which the shut-off valve is closed to the casting start position is in the range of one to a few millimeters, e.g. between approx. 2mm and 20mm.

Sucking back also has the advantage that it provides a corresponding Gießkolbenhubweg, which can be used in a first section of the mold filling phase in the subsequent casting process to accelerate the casting piston before the casting piston begins to press the melt material into the mold. This can be beneficial especially in the case of molds with no or only a relatively small sprue.

Another advantage of sucking back can result in applications in which the gate to the cast part solidifies before the still partially liquid material in the sprue channel. It is then possible to suck back not yet solidified melt material from the sprue cone so that it does not have to be melted again. Depending on the casting mold and the other circumstances, this can be a proportion of melt material of, for example, up to approx. 5% based on the amount of melt introduced into the casting mold.

In a further development of the invention, the casting piston is moved back in the refill phase in the period with the shut-off valve closed at a lower speed than in the previous period with the shut-off valve still open. In other words, in this case the casting piston is moved back during the final suck back section with the shut-off valve closed at a lower speed than in the initial refill section with the shut-off valve open. This choice of a non-constant speed profile of the casting piston in the refill phase advantageously combines a rapid initial refilling of melt into the casting chamber with a moderately slower subsequent sucking back process and reaching the casting start position by the casting piston.

In a further development of the invention, the previously opened shut-off valve is closed in the refilling phase of the casting process as soon as the casting piston has reached a valve changeover position due to its return movement. In the case of a shut-off control valve, this can be done by actively controlled valve switching at this point in time and in the case of a check valve, for example, by stopping the casting piston in the valve changeover position and / or opening the closed casting mold so that no further negative melt pressure is generated in the casting chamber , whereby the check valve automatically moves back into its closed position. With this measure, the shut-off valve is switched from its open position to its closed position depending on the position of the casting piston, more precisely depending on its reaching a certain position, here referred to as valve changeover position or valve changeover position. Closing the shut-off valve ends the supply of melt material into the casting chamber via the melt inlet channel, so that the further return movement of the casting piston from its valve changeover position to in order to reach its casting start position, melt material can be sucked back into the casting chamber to the desired extent from the melt outlet channel. In the case of a check valve, undesired opening of the shut-off valve during this period can be prevented, for example, by opening the casting mold before the casting piston is moved further back from its valve changeover position. In alternative versions, the triggering for the reversal of the shut-off valve from its open position to its closed position is triggered in a different way during the refill phase of the casting process, e.g. by the expiry of a predetermined period of time since the start of the refill phase or since the start of the return movement of the casting piston.

In one embodiment of the invention, a stroke distance between the valve changeover position of the casting piston and the casting start position can be specified in a variable manner. With this measure, it is possible to react flexibly to different system conditions. The stroke distance of the valve changeover position of the casting piston from the casting start position determines the proportion of the final return movement of the casting piston from its valve changeover position to its casting start position in the entire casting piston stroke, which is given by the distance between the filling end position and the casting start position, and thus also the amount of melt suction in the melt outlet channel. This stroke distance is naturally greater than zero and smaller than the entire Gießkolbenhub, ie the stroke distance of the filling end position from the pouring start position, and can be set to a desired value or the requirements of the respective application, e.g. to a value between about 2mm and 20mm and more specifically between approx. 4mm and 8mm, depending on the requirements and the system features of the die casting machine, whereby in corresponding implementations it is at most half or at most a third or at most a quarter of the entire casting piston stroke or even less. The greater the stroke distance between the valve changeover position and the casting start position, the greater the amount of back suction of melt material in the melt outlet channel; the selection of a shorter stroke distance reduces the amount of melt material sucked back into the melt outlet channel. The stroke distance of the valve changeover position from the casting start position of the casting piston can, for example, be selected differently for different casting molds that are used interchangeably in the die casting machine. In alternative versions, this can The stroke distance cannot be changed if a variable setting is not required.

In one embodiment of the invention, in the refilling phase of the casting process, the casting piston is stopped in the valve changeover position for a stop period before it is moved back further to its casting start position. The stopping time for the return movement of the casting piston can be used to switch the shut-off valve from its open position to its closed position and, if necessary, to open the casting mold. As a result, the shut-off valve can be switched over in a period of time in which there is no moving melt flow in the melt inlet channel and thus through the shut-off valve, but instead the melt material is in the melt inlet channel. The duration of the stop can be set appropriately, e.g. depending on the time that the shut-off valve needs to switch from the open position to the closed position and / or that is required to open the casting mold, with an optionally variable specification of the stop time can be provided. In alternative embodiments, the shut-off valve is switched from its open position to its closed position without interrupting the return movement of the casting piston, i.e. without the casting piston being completely stopped in its return movement after it has reached its valve changeover position.

In a further development of the invention, in the refilling phase of the casting process, the casting mold is kept closed at least as long as the shut-off valve is still open. As a result of this measure, melt material is refilled into the casting chamber via the melt inlet channel due to the return movement of the casting piston, but there is still no noticeable sucking back of melt material in the melt outlet channel as long as the shut-off valve is in its open position. Since the casting mold is still closed and the casting usually already contains at least partially solidified cast part, no noticeable amount of air can enter the melt outlet channel via it, so that in this initial section of the refill phase no melt material is sucked back from the melt outlet channel into the casting chamber will. In alternative embodiments, the casting mold is already opened or in any case started to open while the shut-off valve is still open.

In one embodiment of the invention, which is particularly suitable when a shut-off control valve is used as a shut-off valve, the casting mold begins to open in the refill phase of the casting process after the casting piston has reached its casting start position. With this procedure, melt material is sucked back in the melt outlet channel essentially only when the casting piston has reached its casting start position. By moving the casting piston back from the valve changeover position, when the shut-off control valve is reached, into the casting start position, the casting piston first builds up a corresponding negative pressure, and after the casting mold has started to open, the melt material is then drawn out of the melt outlet channel to a corresponding extent by the associated negative pressure effect the casting chamber sucked back.

In an alternative embodiment of the invention, an opening of the casting mold is started in the refilling phase of the casting process after the casting piston has reached its valve switching position and before it has reached its casting start position. With this procedure, melt material can already be sucked back into the casting chamber during the further return movement of the casting piston into its casting start position in the melt outlet channel or from the melt outlet channel. It goes without saying that, in corresponding embodiments, the opening of the casting mold can be started at any time during the return movement of the casting piston from its valve changeover position to its casting start position, in corresponding implementations also alternatively even before the casting piston has reached its valve changeover position and the shut-off valve is closed will.

In a further embodiment of the invention, in the refilling phase of the casting process, the casting piston is stopped in its valve changeover position and moved from its valve changeover position to its casting start position as soon as the casting mold has reached a certain casting piston trigger mold opening position when it is opened. In this implementation, the further return movement of the casting piston after stopping in its valve changeover position is coordinated with the opening process of the casting mold, specifically in such a way that the casting piston is only moved into its casting start position when the casting mold has moved by a predeterminable amount, defined by the specified casting piston trigger. Mold opening position, has opened. This allows the process of the Back suction of melt material in the melt outlet channel in the last section of the refill phase of the casting process can be further optimized. In alternative versions, the return movement of the casting piston takes place without taking into account the current opening position of the casting mold, provided there is no need for this due to the application.

In a further development of the invention, the casting piston is moved forward from its casting start position reached in the refilling phase of a previous casting process in an initial prefilling section of the mold filling phase of a next casting process with the casting mold not yet completely closed into a prefilling position, and only then is the casting mold completely closed and the casting piston moved forward from this pre-filling position into its filling end position. As a result, air that got into the front area of the melt outlet channel as a result of the back-sucking of melt in the refill phase of the previous casting cycle can quickly escape via the fully open or at least partially open mold at the beginning of the current casting cycle, before the mold is completely open is closed and the actual mold filling takes place with the melt material.

According to a further aspect of the invention, to which claim 9 is directed and which can be provided in addition or as an alternative to the first-mentioned aspect of claim 1, the casting piston is in the casting chamber during a start-of-operation casting process in a prefilling phase of the start-up operation-casting process before the mold filling phase with the shut-off valve closed, it is advanced from an operating start position to a specific pre-filling position and then moved back into its casting start position with the shut-off valve open. Depending on requirements and the application, the casting mold can be closed before or at the beginning of this pre-filling phase or, alternatively, it can be kept open during the forward movement of the casting piston in this pre-filling phase and only closed before the casting piston is moved back or when the shut-off valve is opened. In the former case it is ensured without further measures that no melt material can inadvertently escape via the still open mold during this pre-filling process, in the latter case air that is pressed out of the melt outlet channel by the pre-filling process can escape more quickly via the still open mold.

This procedure according to the invention represents a specific operational start measure that can advantageously be used when a cyclic casting operation of the die casting machine is started for the cyclic casting of a plurality of identical cast parts with a specific casting mold in successive casting processes or casting cycles, e.g. after the casting mold has been assembled or of the casting tool on the die casting machine or after restarting the die casting machine with a certain mounted casting mold.

In other words, the operating start casting process represents a first casting process or casting cycle for producing the desired cast part after the machine has started operating. When the machine is started up, the melt material is not yet in a front area of the melt outlet channel, but at most in a rear area of the Melt outlet channel, for example, up to the level of a melt filling level in the casting chamber or a melt bath into which a casting container containing the casting chamber is immersed. The special start-of-operation casting process ensures that the melt material is already present in a front area of the melt outlet channel for the first of several successive casting processes after such a start-up of the machine, when the mold filling phase is started by pulling the casting piston out of its casting start position is advanced in the direction of its filling end position in order to press the melt material into the casting mold.

For this purpose, prior to this mold filling phase in the pre-filling phase of the operation start casting process, the casting piston is initially only moved forward from its operation start position into the pre-fill position, with the shut-off valve remaining closed so that melt material can be pressed out of the casting chamber into the melt outlet channel. The pre-filling position of the casting piston is determined by the fact that, when it is reached, the melt material has filled the melt outlet channel to a desired, predeterminable amount. By subsequently opening the shut-off valve and moving the casting piston back from its pre-filling position to its casting start position, which can correspond to the operating start position or a further forward position of the casting piston in the casting chamber between the operating start position and the pre-filling position, the maximum amount of melt material in which it was previously pressed out of the casting chamber into the melt outlet channel, is refilled into the casting chamber via the melt inlet channel.

For the subsequent first casting process after the machine has started operating, the same or similar conditions with regard to melt material already present up to a front area of the melt outlet channel exist as for the subsequent further casting processes in the started casting operation of the machine. In other words, for this first casting process, the melt material is already available in the melt outlet channel up to a front area of the same, e.g. in the entire volume of a riser channel section and in the volume of an adjoining mouthpiece body section of the melt outlet channel up to the front end area of the mouthpiece body and thus also well above the bath level an assigned melt bath from which the melt material is fed to the casting chamber. This results in the advantage that this one-off pre-filling at the start of operation can significantly reduce the casting piston stroke required for the subsequent actual mold filling phase for the first casting cycle after the start of operation. In alternative embodiments, instead of this pre-filling measure, after the machine has started operating, the first casting process is carried out with a correspondingly longer casting stroke of the casting piston than the further casting processes in the started operating period.

In the die casting machine according to the invention, the control unit and the shut-off valve are set up to bring the shut-off valve into a closed position in order to carry out a respective casting process in a mold filling phase and to control the casting piston in the casting chamber for advancing from a casting start position into a filling end position in order to control melt material via the melt outlet channel into the casting mold, and in a subsequent refilling phase, first of all to bring the shut-off valve into an open position and to control the casting piston to move back into the casting start position in order to feed melt material into the casting chamber via the melt inlet channel.

Furthermore, the control unit and the shut-off valve are set up to bring the shut-off valve back into its closed position during the refill phase before the casting piston has reached its casting start position by its return movement, and the To control the casting piston for sucking back melt material in the melt outlet channel through the further return movement of the casting piston, and / or in the case of an operating start casting process, the casting piston for moving forward in the casting chamber in a pre-filling phase of the operating start casting process before the mold filling phase with the shut-off valve closed from an operating start position to a pre-filling position to control and then to bring the shut-off valve into its open position and to control the casting piston to move back into its casting start position.

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

In a further development of the invention, the shut-off valve is designed as a shut-off control valve, and the control unit is set up to control the shut-off control valve. This enables active control of the shut-off valve by means of the control unit, in particular in order to bring it into its respectively desired open or closed position in the course of a casting process.

In one embodiment of the invention, the die-casting machine contains a valve actuator activated by the control unit for actuating the shut-off control valve. The actuator acts as a link between the control unit and the shut-off valve and can be suitably selected depending on the type of control unit and shut-off valve, e.g. of an electrical, magnetic, hydraulic, pneumatic or mechanical type. Alternatively, the valve actuation functionality can e.g. be integrated directly into the control unit.

In a further development of the invention, the shut-off valve is designed as a check valve that is pretensioned into its closed position. This represents an alternative to implementation as a shut-off control valve. In this case, the shut-off valve is controlled or actuated as a function of the pressure of the melt material acting on it, in particular the melt pressure in the casting chamber.

In a further development of the invention, the die-casting machine contains a valve sensor unit for sensing one or more measured variables of the shut-off valve. This can be used, for example, for the control unit via the valve sensor unit to provide feedback on the current position of the shut-off valve and / or to provide valve diagnostic information that provides information on whether the shut-off valve is working properly or in what state of use it is and whether it requires maintenance, for example.

Fig. 1

eine schematische Längsschnittansicht eines vorliegend interessierenden Teils einer Druckgießmaschine mit einem Absperrsteuerventil als Absperrventil,

Fig. 2

ein Flussdiagramm zur Veranschaulichung eines Betriebsverfahrens für die Druckgießmaschine von Fig. 1 ab einem Betriebsstart,

Fig. 3

die Ansicht von Fig. 1 bei Betrieb der Maschine gemäß dem Verfahren von Fig. 2 zu Beginn einer Formfüllphase eines ersten Gießzyklus,

Fig. 4

die Ansicht von Fig. 3 während der Formfüllphase,

Fig. 5

die Ansicht von Fig. 3 nach beendeter Formfüllphase zu Beginn einer Nachfüllphase des ersten Gießzyklus,

Fig. 6

die Ansicht von Fig. 3 während der Nachfüllphase,

Fig. 7

die Ansicht von Fig. 3 nach beendetem Nachfüllen von Schmelze in die Gießkammer,

Fig. 8

die Ansicht von Fig. 3 während einer an die Schmelzenachfüllung anschließenden Schmelzerücksaugung,

Fig. 9

die Ansicht von Fig. 3 gegen Ende des ersten Gießzyklus,

Fig. 10

die Ansicht von Fig. 3 am Ende der Formfüllphase eines zweiten Gießzyklus,

Fig. 11

ein Flussdiagramm zur Veranschaulichung eines Betriebsverfahrens für die Druckgießmaschine von Fig. 1 in einer Variante mit anfänglicher Vorfüllphase nach Betriebsstart,

Fig. 12

die Ansicht von Fig. 3 bei Betrieb der Maschine gemäß dem Verfahren von Fig. 11 zu Beginn der anfänglichen Vorfüllphase,

Fig. 13

die Ansicht von Fig. 12 zu einem späteren Zeitpunkt der anfänglichen Vorfüllphase mit Schmelzenachfüllung in die Gießkammer,

Fig. 14

die Ansicht von Fig. 12 am Ende einer an die anfängliche Vorfüllphase anschließenden Formfüllphase des ersten Gießzyklus in der Verfahrensvariante von Fig. 11,

Fig. 15

ein Flussdiagramm zur Veranschaulichung eines Betriebsverfahrens für die Druckgießmaschine von Fig. 1 in einer Variante mit zyklischer Vorfüllung vor der Formfüllphase eines jeweiligen Gießzyklus und

Fig. 16

die Ansicht von Fig. 1 für eine Variante der Druckgießmaschine mit einem Rückschlagventil als Absperrventil.

Advantageous embodiments of the invention are shown in the drawings. These and further embodiments of the invention are explained in more detail below. Here show:

Fig. 1

a schematic longitudinal sectional view of a presently interesting part of a die casting machine with a shut-off control valve as a shut-off valve,

Fig. 2

a flow chart to illustrate an operating method for the die casting machine of FIG Fig. 1 from a start of operation,

Fig. 3

the view of Fig. 1 when operating the machine according to the procedure of Fig. 2 at the beginning of a mold filling phase of a first casting cycle,

Fig. 4

the view of Fig. 3 during the mold filling phase,

Fig. 5

the view of Fig. 3 after the end of the mold filling phase at the beginning of a refilling phase of the first casting cycle,

Fig. 6

the view of Fig. 3 during the refill phase,

Fig. 7

the view of Fig. 3 after the melt has been refilled into the casting chamber,

Fig. 8

the view of Fig. 3 during a melt back suction following the melt replenishment,

Fig. 9

the view of Fig. 3 towards the end of the first casting cycle,

Fig. 10

the view of Fig. 3 at the end of the mold filling phase of a second casting cycle,

Fig. 11

a flow chart to illustrate an operating method for the die casting machine of FIG Fig. 1 in a variant with an initial pre-filling phase after the start of operation,

Fig. 12

the view of Fig. 3 when operating the machine according to the procedure of Fig. 11 at the beginning of the initial pre-filling phase,

Fig. 13

the view of Fig. 12 at a later point in the initial pre-filling phase with melt refilling in the casting chamber,

Fig. 14

the view of Fig. 12 at the end of a mold filling phase of the first casting cycle that follows the initial prefilling phase in the process variant of Fig. 11 ,

Fig. 15

a flow chart to illustrate an operating method for the die casting machine of FIG Fig. 1 in a variant with cyclical pre-filling before the mold filling phase of a respective casting cycle and

Fig. 16

the view of Fig. 1 for a variant of the die casting machine with a check valve as a shut-off valve.

In the Fig. 2 , 11th and 15th various advantageous variants of the die-casting machine operating method according to the invention are illustrated in a flowchart. the Fig. 1 , 3 to 10 and 12 to 14 or the Fig. 16 show schematically the part of a die casting machine that is of interest here in two implementations according to the invention, which can be operated with the method according to the invention. This die casting machine can in particular be of the hot chamber type for die casting of 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 comprises in particular a casting mold 1 with a fixed mold half 1a and a movable mold half 1b, a casting chamber 2, a casting piston 3 arranged axially movably in the casting chamber 2, a melt inlet channel 4 leading into the casting chamber 2, a shut-off valve 5 in the melt inlet channel 4, a melt outlet channel 6 leading from the casting chamber 2 to the casting mold 1 and a control unit 7.

The shut-off valve 5 is in the example of Fig. 1 , 3 to 10 and 12 to 14 designed as a shut-off control valve 5s, ie as a controllable shut-off valve, which is controlled by the control unit 7 directly or, as in the example shown, via an optional valve actuator 16. The valve actuator 16 can be any desired actuator of a conventional type, as is known per se to the person skilled in the art for actuating such a valve. The actuator 16 can in particular be of a conventional electrical, hydraulic, pneumatic or mechanical direct or a lever system etc. Depending on requirements and the application, the valve actuator 16 can be a purely binary actuator type that reverses the shut-off valve 5 only between a first, open position and a second, closed position, or alternatively a proportional actuator type that continuously switches the shut-off valve 5 or can open in several stages, ie the shut-off valve 5 can also spend and hold in one or more partial open positions between its fully open position and its fully closed position. For this purpose, the valve actuator can, for example, include variably adjustable end stops that can be adjusted manually or automatically. Fig. 16 shows in a schematic representation accordingly Fig. 1 a variant of the die casting machine that differs from the one in Fig. 1 differs in that the shut-off valve 5 is designed as a check valve 5 _R.

In the present case, the control unit 7 is to be understood as comprehensively all control elements of the die casting machine for controlling or regulating the various components of the machine, for which purpose the control unit 7, depending on the system design, can contain a single control device in which all control functionalities are integrated, or several individual control devices that Control or regulate specific machine components in each case and are preferably in communication with one another. Likewise, the control unit 7 can, as usual, at least partially in hardware and / or at least partially in software be executed. To illustrate all machine control functionalities of the control unit 7, control arrows 7a, 7b, 7c are shown only symbolically, which lead from the control unit 7 to the casting mold 1, to the casting piston 3 or to a valve rod 5d of the shut-off valve 5, with the control functions associated with these machine components primarily interested. For the sake of simplicity, the schematic illustration of the control unit 7 is only shown in FIG Fig. 1 included in the Figures 3 to 10 and 12 to 14 however omitted.

Unless this is discussed in more detail below, both the control unit 7 and the other machine components mentioned are of a conventional structure that is familiar to the person skilled in the art, which therefore does not require any further explanation here. In the example shown is how, for example Fig. 1 As can be seen, the casting chamber 2 is formed in a casting container 8 of a casting unit that is conventional in this respect, the casting container 8 being immersed in a melt bath 9 during the casting operation, which is located in a conventional melt container 10.

In the examples shown, the shut-off valve 5 is held on the casting container 8 with a valve housing body 5a. On the valve housing body 5a, alternatively at another point of the casting container 8, there are one or more inlet openings as inlet 4a of the melt inlet channel 4, ie melt material 14 can get from the melt bath 9 via the inlet 4a into the melt inlet channel 4. The shut-off valve 5 is located specifically with a fixed valve seat 5b and a movable valve-closing body 5c in the melt inlet channel 4, whereby the valve-closing body 5c in the example shown can be moved axially against the valve seat 5b via the valve rod 5d and moved away from it, around the shut-off valve 5 to close or open, ie between a e.g. in Fig. 1 open position VO shown and an example in Fig. 3 to change the closed position VS shown. The open position VO can be a fully open position or a partially open position of the valve, depending on the valve design and / or operating situation. In alternative embodiments not shown, the shut-off valve 5 is arranged in the casting piston 3, in which case the melt inlet channel 4 is guided over the casting piston 3, in particular through it, as is known per se.

In the machine version of the Fig. 1 , 3 to 10 and 12 to 14 the switching movement of the shut-off valve 5, ie the shut-off control valve 5s, takes place, as already mentioned, by the control unit 7 via the optional valve actuator 16. In the machine version of the Fig. 16 the switching movement of the shut-off valve 5, ie the check valve 5 _R , takes place depending on the melt pressure in the casting chamber 2, the check valve 5 _R being biased into its closed position VS by a biasing unit 17 of conventional type. If there is a corresponding negative melt pressure in the casting chamber 2, the check valve 5 _{R is moved} by this negative pressure against the pretensioning force of the pretensioning unit 17 from its closed position VS into its open position VO. As soon as the melt vacuum is no longer present, the check valve 5 _R automatically returns to its closed position VS due to the action of the pretensioning unit 17. The pretensioning unit 17 can be implemented, for example, by a pretensioning spring, such as a correspondingly designed and arranged compression or tension spring, the pretensioning unit 17 in Fig. 16 is represented only by way of example and schematically by a tension spring illustration.

The melt outlet channel 6 leads out of the casting chamber 2 in a customary manner via a riser channel area or riser pipe section 6a formed in the casting container 8 and then continues via a mouthpiece body 6b to the area of the mold 1. For this purpose, the mouthpiece body 6b is also conventionally coupled on the inlet side to a mouthpiece attachment 11, with which the riser pipe section 6a opens out of the casting container 8, and is guided on the outlet side up to the area of a sprue cone 12 in the fixed mold half 1a in front of a casting cavity 13 which, when the casting mold is closed 1 is formed by the two mold halves 1a, 1b and is designed depending on the cast part to be produced.

Fig. 2 illustrates the operating method according to the invention in an exemplary embodiment variant when the die casting machine starts operating, ie after starting the machine for casting a desired number of identical cast parts in a corresponding number of successive casting processes or casting cycles. the Fig. 1 and 3 to 10 illustrate the machine schematically in different operating stages during operation according to the variant embodiment of FIG Fig. 2 . The machine is in the Figures 3 to 10 just for the sake of simplicity in the execution of Fig. 1 shown the associated However, the following statements apply equally to the machine design of Fig. 16 unless otherwise stated.

In an initial operating stage B1 of Fig. 2 the machine is in a basic state at the start of operation. Fig. 1 shows the machine in this operating stage B1 with the exception that the casting mold 1, which is still open in the basic state, is already shown in its closed state. The casting piston 3 is accordingly in an operating start position BS. The shut-off valve 5 is still open, so that the melt material 14 is present everywhere up to the level of a melt pool level 9 a of the melt pool 9. In particular, the melt material 14 also lies in the melt outlet channel 6 on a melt level SH corresponding to the melt pool level 9a, the melt material 14 extending, for example, into a central or front area of the riser channel section 6a and not yet as far as the mouthpiece body 6b.

In a subsequent operating stage B2 of Fig. 2 a first casting cycle is initiated and an associated mold filling phase is carried out. For this purpose, the mold 1 is first closed, and the shut-off valve 5 is brought from its open position VO to its closed position VS and held there, either as Absperrsteuerventil 5s controlled by the control unit 7, or as a check valve 5 _R automatically by the bias unit 17th Fig. 3 shows the machine at this point in time. The casting piston 3 is then moved forward from the operating start position BS into a filling end position FP, ie into the Fig. 1 , 3 to 10 and 12 to 14 downwards in each case, so that melt material 14 is pressed out of the casting chamber 2 via the melt outlet channel 6 into the casting mold 1. The forward movement of the casting piston 3 is symbolized in the corresponding figures with an associated arrow GV in the direction of movement. The melt flow in the melt outlet channel 6 is in Fig. 4 indicated symbolically with corresponding flow arrows, where Fig. 4 shows the machine at the end of this mold filling phase, which can include a so-called holding pressure phase in a manner known per se, in which an additional, increased holding pressure is exerted on the melt material 14 in the mold 1.

In an operating stage B3 of Fig. 2 the mold filling phase is ended and a refilling phase or piston return phase follows. For this purpose, the shut-off valve 5 is switched from its closed position VS to its open position VO, and the casting piston 3 is moved back out of its filling end position FP, ie upwards in the relevant figures. The switching of the shut-off valve 5 occurs in the case of Absperrsteuerventils 5s controlled by the control unit 7, in the case of the check valve 5 by the resultant _R in the casting chamber 2 due to the return movement of the casting piston 3 melt under pressure. It should be mentioned at this point that, of course, the forward and backward movement of the casting piston 3, depending on the machine type, cannot be oriented in the vertical direction, as in the example shown, but rather perpendicular or inclined to the vertical direction. The casting mold 1 initially remains closed, and the so-called cooling time runs, during which the melt material 14 is cooled in the casting cavity 13, so that a desired cast part 15 is formed by the melt material 14 solidifying there. As a result of the return movement of the casting piston 3, melt material 14 is sucked from the melt bath 9 via the melt inlet channel 4 into the casting chamber 2 and is thus refilled. the Figures 5 and 6 show the machine at an initial or somewhat later point in time of the refilling phase, while the melt material 14 is being refilled from the melt bath 9 into the casting chamber 2, as illustrated by the corresponding flow arrows. The return movement of the casting piston 3 is symbolized in the corresponding figures with an associated arrow GR for the direction of movement.

In an operating stage B4 of Fig. 2 the refilling of melt material 14 from the melt bath 9 via the melt inlet channel 4 into the casting chamber 2 is ended in that the shut-off valve 5 is switched from its open position VO to its closed position VS. This is in the case of Absperrsteuerventils 5s effected by the control unit 7, in the case of the check valve 5 _R fact that the return movement of the casting plunger 3 is stopped, and thus no melt negative pressure is produced any longer in the casting chamber 2, so that the check valve 5 _R automatically by its Biasing unit 17 returns to its closed position VS. At this point in time, the casting piston 3 is in a corresponding valve reversing position or valve reversing position VU. The casting piston 3 is preferably stopped there during a stopping period, the length of which can be suitably predetermined, in particular such that the shut-off valve 5 has reached its closed position VS when the stopping period has expired. Optionally, for example, it can also be provided that the stop duration corresponds to a To select the changeover period of the shut-off valve 5 from its open position VO to its closed position VS, or to monitor when the shut-off valve 5 has reached its closed position VS, and then to end the stop period or to move the plunger 3 further. Fig. 7 shows the machine at this point. In the meantime, the cooling time for the melt material 14 in the casting mold 1 to form the cast part 15 continues.

After the stop time has elapsed or the valve changeover position VU has been passed or after the shut-off valve 5 has been closed, the casting piston 3 is in an operating stage B5 of Fig. 2 moved further back into a casting start position GS for a next, second casting process, whereby a melt back suction process begins. The casting start position GS can be identical to the initial operating start position BS of the casting piston 3 or deviate therefrom to a limited extent. Fig. 8 shows the machine in an intermediate position ZS of the casting piston 3 during this return movement of the casting piston 3 beyond the valve changeover position VU or out of the valve changeover position VU.

In the variant with the shut-off control valve 5s, this is kept in its closed position VS in a controlled manner, and the casting mold 1 is not yet opened, so that the further return movement of the casting piston 3 causes a suction effect via the casting chamber 2 on the melt outlet channel 6. This creates a negative pressure in the area of the sprue cone 12 in that the melt material 14 is already slightly retreating from the front outlet of the melt outlet channel 6, in the example shown specifically the mouthpiece body 6b, as in FIG Fig. 8 indicated by a back suction arrow 14a.

In the variant with the check valve 5 _R , in so far as a deviation from the above selected for the variant with the shut-off control valve 5s, in Fig. 2 Procedure specified for operating stage B5, at this point in time before the further return movement of the casting piston 3, the casting mold 1 is opened at least by a predeterminable amount, the cooling time having expired or the end of it being awaited. As a result, the melt outlet channel 6 on the part of the casting mold 1 is no longer hermetically sealed from the outside atmosphere, with the result that, with the further return movement of the casting piston 3, there is no longer any negative melt pressure in the Casting chamber 2 builds up. Accordingly, the check valve 5 _R remains in its closed position VS. Instead, the melt material 14, especially in the front area of the mouthpiece body 6b, is withdrawn further away from the area of the sprue cone 12, that is, melt material is drawn back to a limited extent from the foremost, exit-side area of the melt outlet channel 6, which prevents the formation of a melt droplet in the area of the sprue cone 12 .

The further return movement of the casting piston 3 from the valve changeover position VU to the casting start position GS preferably takes place at a piston speed that is noticeably lower than the piston speed with which the casting piston 3 was previously moved back from the filling end position FP to the valve changeover position VU.

The stroke distance of the valve changeover position VU to the casting start position GS of the casting piston 3 determines the amount of sucking back of melt material 14 in the melt outlet channel 6, whereby it can optionally be provided that this stroke distance can be variably predefined or set by the user.

While in the example shown, the point in time at which the shut-off valve 5 is switched to its closed position VS to complete the refilling of melt material 14 from the melt bath 9 into the casting chamber 2 is linked to the reaching of the valve changeover position VU by the casting piston 3, this valve switching is shown in alternative embodiments in triggered in another way, for example after a certain period of time since the beginning of the return movement of the casting piston 3 from its filling end position FP.

In an operating stage B6 of Fig. 2 the return movement of the casting piston 3 is then completed after reaching its casting start position GS. In the meantime, in the variant with the shut-off control valve 5s, the cooling time for complete solidification of the cast part 15 formed in the mold 1 has expired, and accordingly in this variant in a next operating stage B7 from Fig. 2 can be started with the opening of the mold 1 by a corresponding opening movement of the movable mold half 1b, as in FIG Fig. 9 illustrates which the machine is showing at this point in time of operation. By opening the mold 1, the suction back pressure previously generated in the variant with the shut-off control valve 5s can be reduced in the Immediately reduce the area of the sprue cone 12, as a result of which the melt material 14 in the front area of the melt outlet channel 6, in the example shown specifically in the front area of the mouthpiece body 6b, retreats further away from the area of the sprue cone 12. In turn, prevents the retraction, that is, limited rear eyes, of the molten material 14 from the forward, outlet-side region of the Schmelzeauslasskanals 6, as mentioned the formation of a melt drop in the region of the sprue cone 12 above the variant with the check valve 5 _R. In both variants, the cast part 15 formed can then be removed in each case after the mold 1 has been completely opened.

Fig. 9 shows an example of the standing of the melt material 14 in the front area of the melt outlet channel 6 up to a suck back point RP, which maintains a desired, sufficient distance AS to the area of the sprue cone 12 or the outlet of the melt outlet channel or the melting point at which the sucked back melt material 14 from in the mold 1 and in the sprue cone 12 remaining, solidified or partially solidified melt material tears off. The aforementioned drop formation can thus be reliably prevented, this distance AS in Fig. 9 is exaggerated and not to scale only for the sake of clarity. The distance AS is, for example, approx. 5mm to 100mm from the sprue cone 12, at which the melt droplet would otherwise form, in particular between approx. 10mm and approx. 50mm, preferably between approx. 30mm and approx. 40mm, depending on the viscosity, for example the melt material and / or the system design of the machine, including depending on the diameter of the casting piston, riser bore and mouthpiece body. Alternatively, the distance AS can also be greater, with the increasing distance AS, more air being available in the outlet-side area of the melt outlet channel 6 before the start of the next casting cycle.

In any case, however, the melt outlet channel 6 remains filled with melt material 14 up to above the melt pool level 9a of the melt pool 9, so that in the next casting cycle the melt material 14 in the melt outlet channel 6 is not as in the first casting cycle after the start of operation Fig. 3 needs to be moved forward from the melt pool level 9a, but the melt level SH in the melt outlet channel 6 is already well above the melt pool level 9a at the beginning of the next casting cycle and the melt material 14 is preferably already in front area of the melt outlet channel 6 is present. This means that after operating stage B7 of Fig. 2 the first casting cycle completed.

In order to carry out the next, second casting cycle, an operating stage B8 of Fig. 2 the mold 1 is closed and the casting piston 3 is moved from its casting start position GS to its filling end position FP in order in turn to press the melt material 14 from the casting chamber 2 via the melt outlet channel 6 into the closed mold 1. Fig. 10 shows the machine at the end of the mold filling phase of this second casting cycle corresponding to that in Fig. 4 Machine status shown at the end of the mold filling phase of the first casting cycle.

As in Fig. 10 Comparatively shown, in the second casting cycle a smaller axial movement stroke of the casting piston 3 from the casting start position GS into the filling end position FP than in the first casting cycle is sufficient for the advance movement of the casting piston 3 from the operating start position BS into the filling end position FP, since the melt material 14 is already used for the second casting cycle is present in the melt outlet channel 6 well above the melt pool level 9a. In other words, as in Fig. 10 schematically indicated, the Füllendposition FP in the second molding cycle at a related to the position in the casting chamber 2 end position FP ₂ opposite to those end position FP _1, 3 occupied by the casting piston as Füllendposition FP in the first molding cycle, further back, ie in Fig. 10 further up, lies.

In other words, a stroke distance HA = FP-GS = FP ₂ -GS of the filling end position FP from the casting start position GS for the second and each subsequent casting cycle of a corresponding active operating interval of the machine is less than the corresponding stroke distance HA = FP-BS = FP ₁ -BS the filling end position FP from the operating start position GS for the first casting cycle, the difference being determined by the amount of melt material 14 that is present in the melt outlet channel 6 above the melt pool level 9a after the first and before the second casting cycle. The stroke difference is in Fig. 10 illustrated by a corresponding stroke difference HD = FP ₁ -FP _{2 of} the filling end position after the first pouring cycle FP ₁ compared to the filling end position FP ₂ after the second pouring cycle. The shortening of this stroke length for the second and the further casting cycles can be, for example, up to 30% or up to 50% and more, depending on the machine type and the cast part 15 to be produced.

This shortening of the stroke length that the casting piston 3 has to cover during the mold filling phase enables a corresponding reduction in the cycle time, i.e. the duration of the respective casting cycle, for the second and each subsequent casting cycle within the operating interval, e.g. by up to 5% or 10%. In addition, due to the melt material 14 remaining in the melt outlet channel 6 beyond the melt pool level 9a between the casting cycles, the proportion of air to be displaced in the outlet-side part of the melt outlet channel 6 is reduced, whereby the air trapped in the cast part can also be reduced, which benefits the quality of the cast part. In addition, by shortening the casting piston stroke, the wear effects for the casting piston and the casting chamber caused by the casting piston movement in the casting chamber can be reduced.

The mold filling phase and the subsequent refilling phase of the second casting cycle then proceed in the same way as explained above for the first casting cycle, to which reference can be made. This is in Fig. 2 symbolized by a return arrow from operating stage B8 to operating stage B3.

In the embodiment shown with the shut-off control valve 5s as the shut-off valve 5, the casting mold 1 remains closed during the entire refilling phase with appropriate operational management until the casting piston 3 has reached its casting start position GS as the start position for the next casting cycle. The opening of the mold 1 only at this point in time then leads to the instantaneous suck-back effect mentioned. In alternative operational management, the casting mold 1 can be opened earlier and thereby the suck-back effect can be made more uniform over time and / or weakened. In corresponding operating variants, the casting mold 1 remains closed at least as long as the shut-off control valve 5s is still open for the purpose of refilling melt material 14 from the melt bath 9 into the casting chamber 2. When the casting piston 3 has reached its valve changeover position VU and the shut-off control valve 5 has thereby been closed, the casting mold 1 is opened as required at an earlier or later point in time of the further return movement of the casting piston 3 from the valve changeover position VU to the casting start position GS. As soon as the opening of the mold 1 begins, more air can reach the front area of the melt outlet channel 6 via the outlet of the melt outlet channel 6 and thereby weaken or attenuate the negative pressure effect there.

In a further operating variant, the casting piston 3 is stopped in the valve changeover position VU, and the opening of the casting mold 1 is then started after the cooling time has elapsed. As soon as the casting mold 1 has reached a specific, variable or fixed predeterminable pouring piston trigger mold opening position when opening, e.g. when the movable mold half 1b has moved a corresponding predeterminable distance away from the fixed mold half 1a, the pouring plunger 3 is moved from its valve changeover position VU to its pouring start position GS moved further back. The casting piston trigger mold opening position is selected in such a way that air access to the melt outlet channel 6 is possible via the sprue cone 12 or the mouthpiece nozzle. This can then result in the melt material 14 being sucked back in the foremost region of the melt outlet channel 6 in a relatively uniform time course without sudden vacuum reduction. This operating variant is particularly suitable, for example, for the machine variant of Fig. 16 with the non-return valve 5 _R as shut-off valve 5. Because as soon as the mold 1 has been opened in this way by an amount sufficient for air to enter the melt outlet channel 6, the further return movement of the casting piston 3 no longer generates negative melt pressure in the casting chamber 2, and the non-return valve 5 _R remains automatically in its closed position VS due to the action of the pretensioning unit 17.

Fig. 11 illustrates the die casting machine operating method according to the invention in a further advantageous embodiment variant, which specifically relates to the implementation of the first casting cycle after the machine has started operating and which is particularly suitable for the machine variant with the shut-off control valve 5s as the shut-off valve 5. For this purpose, this operating variant in turn starts from the basic state of the machine at an operating start according to the initial operating stage B1 from Fig. 2 out. In contrast to the operating variant of Fig. 2 is now, however, in the operating variant of Fig. 11 an operating start casting process, ie a special first casting cycle, is carried out in which the mold filling phase is preceded by an initial prefilling phase.

For this purpose, this initial pre-filling phase begins in an operating stage B2a of Fig. 11 so that after closing the shut-off control valve 5 and closing the mold 1, the casting piston 3 from the operating start position BS only up to an in Fig. 12 initial pre-fill position VP shown is advanced, wherein Fig. 12 the machine in this Operating stage B2a shows. The melt material 14 is thereby prefilled in the melt outlet channel 6 beyond the melt pool level 9a of the melt pool 9, preferably up to a prefilling point VA in the front area of the melt outlet channel 6 or the mouthpiece body 6b, so that the prefilling point VA is only a relatively small distance DS from the outlet of the Melt outlet channel 6 into the mold 1 or from the sprue cone 12. This distance DS can, for example, correspond approximately to the distance AS of the suck back point RP from the outlet of the melt outlet channel 6 into the mold 1, as is the case after the above-explained suck back of melt material 14 in the melt outlet channel 6 in the operating variant of Fig. 2 is present and in Fig. 9 is shown. Alternatively, the distance DS can also differ slightly or significantly from the distance AS.

Subsequently, in an operating stage B2b of Fig. 11 waited a certain, predefinable period of time until an overpressure formed in the casting cavity 13 by the pre-filling process due to the compressed air has been reduced. Thereafter, in an operating stage B2c of Fig. 11 the shut-off control valve 5 is reversed from its closed position VS to its open position OS, and the casting piston 3 is moved back from the pre-filling position VP into its casting start position GS. As a result, melt material is sucked in or refilled from the melt bath 9 via the melt inlet channel 4 into the casting chamber 2, as indicated by an associated flow arrow in FIG Fig. 13 illustrates, in which the machine is shown at the end of this operating stage B2c, at which the casting piston 3 has again reached its casting start position GS.

This melt refilling process can be accompanied by a certain further sucking back of melt material 14 in the melt outlet channel 6, since a certain amount of air is also contained in the closed mold 1 and the mold 1 may also not be completely airtight. As a result, the pre-filling point VA, up to which the melt material 14 is pre-filled in the melt outlet channel 6, can shift somewhat to the rear, as in FIG Fig. 13 by an associated backflow arrow in the melt outlet channel 6 and one in comparison to FIG Fig. 12 illustrates pre-filling point VA located further back in the mouthpiece body 6b. Nevertheless, the melt material 14 remains pre-filled in the melt outlet channel 6 well beyond the melt pool level 9 a of the melt pool 9 up to the front region of the melt outlet channel 6.

In principle, an analogous pre-filling process is also possible for the machine variant with the check valve 5 _R as the shut-off valve 5. In this case, the check valve 5 _R remains closed by the melt pressure in the casting chamber 2, while the casting piston 3 is advanced from its operating start position BS to its pre-filling position VP. If then a suitable reduction of the overpressure in the operating stage B2b is ensured, as mentioned above, and then it is ensured that a sucking back of melt material in the melt outlet channel 6 is sufficiently difficult or slowed down, e.g. by a controllable closure in the melt outlet channel 6 and / or By moving the casting piston 3 back sufficiently quickly, the return movement of the casting piston 3 from the pre-filling position VP to its casting start position GS _{can generate sufficient negative pressure in the casting chamber 2 to open the check valve 5 R} , so that in this case too, melt material from the melt pool 9 overflows the melt inlet channel 4 can be sucked into the casting chamber 2 or refilled.

After completion of this initial pre-filling phase, the mold filling phase of the first casting cycle becomes in accordance with an operating stage B2d of Fig. 11 accomplished. For this purpose, the shut-off control valve 5 is switched back to its closed position VS, or the check valve 5 _R closes again automatically after the melt vacuum in the casting chamber 2 has ceased, and the casting piston 3 is moved forward from its casting start position GS into the filling end position FP, so that again Melt material 14 is pressed from the casting chamber 2 via the melt outlet channel 6 into the casting mold 1, specifically the casting cavity 13.

As a result of the initial pre-filling, compared to the first casting cycle without pre-filling, as in the case of in Fig. 2 illustrated operating variant, a shortening of the stroke distance HA = FP-BS of the filling end position FP from the operating start position GS already for this mold filling phase of the first casting cycle. This shortening of the stroke for the first casting cycle is analogous to the shortening of the stroke explained above, which occurs in the operating variant of Fig. 2 is only achieved for the further casting cycles by the early closing of the shut-off control valve 5 in the refill phase of the previous casting cycle before reaching the casting start position GS and the further return movement of the casting piston 3 to the casting start position GS. Fig. 14 shows the machine in this operating stage B2d at the end of the mold filling phase of the first casting cycle the shortening of the filling end position FP to a position FP _1V for the variant with initial pre-filling, which is a stroke difference HD ₁ = FP ₁ -FP _1V behind the filling end position FP ₁ in the first casting cycle for the operating variant of Fig. 2 without pre-filling. In other words, in this operating variant, this pre-filling measure is already for the first casting cycle compared to the operating variant of Fig. 2 without pre-filling, a shortened pouring stroke to carry out the mold filling.

Thus, with the operating variant of Fig. 11 those above for shortening the stroke in the second and in further casting cycles in the operating variant of Fig. 2 mentioned properties and advantages through the operating variant of Fig. 11 already achieved for the first casting cycle.

The further course of the first casting cycle can then correspond to that of the operating variant of Fig. 2 from the operating stage B3 there. Alternatively, the first casting cycle in the operating variant of Fig. 11 can be continued by any conventional method of operation.

Fig. 15 illustrates an advantageous variant of the operating method of FIG Fig. 2 with regard to the implementation of the second and further casting cycles. In this variant of the method, the respective mold filling phase includes a pre-filling section from the second casting cycle. For this purpose, the operating situation at the end of operating stage B7 is assumed, as shown in Fig. 9 is illustrated. Deviating from the operating variant according to operating stage B8 of Fig. 2 is used in the operating variant of Fig. 15 In an operating stage B8a, the forward movement of the casting piston 3 does not wait until the mold 1 is completely closed, but the casting piston 3 is moved forward from the casting start position GS into a pre-filling position VP ₂ for the second casting cycle while the mold is still open, this pre-filling position VP ₂ to differentiate the pre-filling position VP at the end of the initial pre-filling phase before the first casting cycle according to the operating variant of Fig. 11 and the illustration in Fig. 12 In the present case, it is also referred to as the cyclic pre-filling position VP ₂ .

This cyclical pre-filling measure can be used beforehand according to the operating stages B5 to B7 of the operating variant from Fig. 2 Melt material 14 sucked back away from the outlet of the melt outlet channel 6 is moved forward again in the direction of the outlet of the melt outlet channel 6, thereby further pre-filling the melt outlet channel 6, the air at the front end area of the melt outlet channel 6 being able to escape unhindered via the not yet closed mold 1.

The casting piston 3 is then in an operating stage B8b of Fig. 15 held in this cyclic pre-filling position until the mold 1 is completely closed. The remainder of the mold filling phase of the associated second or further casting cycle then takes place in accordance with an operating stage B8c from Fig. 15 , for which the casting piston 3 is moved forward from its cyclical pre-filling position into the filling end position FP or FP _{2 in} order to press the melt material 14 from the casting chamber 2 via the pre-filled melt outlet channel 6 into the closed mold 1 or its casting cavity 13. The operating status of the machine at this point in time corresponds to that of Fig. 10 or at the end of the operating stage B8 of Fig. 2 . In other words, in the operating variant of Fig. 15 after the end of the mold filling phase at the end of operating stage B8c with the refilling phase and the further steps from operating stage B3 from Fig. 2 continued.

Due to the cyclical pre-filling at the beginning of the mold filling phase of the second and the subsequent casting cycles, the cycle time and the proportion of air in the cast part produced can also be reduced by a corresponding amount. In a correspondingly optimized operational management, the operational variants of the Fig. 2 , 11th and 15th be combined in such a way that for a respective operating interval of the die casting machine at the start of operation, the initial pre-filling with melt refilling in the casting chamber according to the variant of FIG Fig. 11 is carried out, then the remaining first casting cycle according to the operating variant of Fig. 2 is carried out and then the second and further casting cycles according to the operating variant of Fig. 15 be performed. Alternatively, operational variants according to the invention are possible, the variants mentioned only the special initial pre-filling and melt refilling according to the start of operation Fig. 11 or only the back suction measure according to the operating stages B3 to B8 of Fig. 2 with or without an additional combination with the cyclical pre-filling according to Fig. 15 to use.

As shown, the die-casting machine according to the invention is set up to carry out the operating method according to the invention. In particular, the control unit 7 is configured accordingly to carry out a respective casting process, for which purpose it controls the casting piston 3 in the casting chamber 2 to move forward from the casting start position GS into the filling end position FP in the mold filling phase, in order to transfer the melt material 14 via the melt outlet channel 6 into the casting mold 1 to press, and in the example the Fig. 1 , 3 to 10 and 12 to 14 the shut-off control valve 5s controls directly or via the valve actuator 16 in its closed position VS, while in the machine design according to Fig. 16 the check valve 5 _R automatically remains in its closed position VS under the action of the biasing unit 17 and the melt pressure in the casting chamber 2. Furthermore, the control unit 7 is set up to control the casting piston 3 to move back into the casting start position GS in the subsequent refill phase in order to supply the melt material 14 to the casting chamber 2 via the melt inlet channel 4, and for this in the machine version of the Fig. 1 , 3 to 10 and 12 to 14 to control the shut-off control valve 5s initially in its open position VO, while in the machine design according to Fig. 16 the check valve 5 _R reaches its open position VO due to the negative pressure in the casting chamber 2.

Furthermore, the control unit 7 and the shut-off valve 5 can be set up so that the shut-off valve 5 is switched back to its closed position VS during the refilling phase, before the casting piston 3 has reached its casting start position GS due to its return movement, and for sucking back melt material 14 in the melt outlet channel 6 to control the casting piston 3 moving further back. Alternatively or additionally, the control unit 7 can also be set up to move the casting piston 3 forward in the casting chamber 2 in the pre-filling phase of the operating start casting process before the mold filling phase with the shut-off valve 5 closed from the operating start position BS during an operational start casting process, ie a first casting cycle to control in the pre-filling position VS, then it is ensured that the shut-off valve 5 reaches its open position VO and the casting piston 3 is controlled to move back into its casting start position GS.

As in the examples shown, the die casting machine optionally has a valve sensor unit 18 for sensing one or more measured variables of the Shut-off valve 5. The measured values recorded by the valve sensor unit 18 with regard to the respective measured variable can, if necessary, be fed to the control unit 7 in order to give it control feedback about the current position of the shut-off valve 5. Additionally or alternatively, the measured values can be used for diagnostic evaluation in order to diagnose the current state of the shut-off valve 5, for example with regard to possible malfunctions, and to recognize when the shut-off valve 5 requires maintenance.

The valve sensor unit 18 can include one or more sensors including optional limit switches with or without a connection to the control unit 7, depending on requirements and application, which, as already mentioned, can be an entire machine control of the die casting machine or a part of this machine control. The valve sensor unit 18 can, for example, be set up to measure the stroke of the shut-off valve in order to derive an error diagnosis, e.g. whether the valve closing body 5c has been torn off and the valve rod 5d passes its target position during the valve closing movement and / or whether the valve closing body 5c is in its closed position actually reached or stops prematurely. The valve sensor unit 18 can optionally also comprise a force sensor in the valve rod 5d, which measures the closing force or the contact pressure and / or the opening force of the valve closing body 5c for diagnostic monitoring. In the case of an electrical or hydraulic or pneumatic valve drive, e.g. via the valve actuator 16, the valve sensor unit 18 can also comprise a current sensor or pressure sensor of conventional design for this monitoring purpose, be it with or without a connection to the control unit 7.

As the exemplary embodiments shown and those explained above make clear, the invention provides an advantageous method for operating a die casting machine with which short casting cycle times, a low proportion of air in the cast part, a low tendency to wear the casting piston and casting chamber due to a reduced casting piston stroke and / or avoid the formation of melt droplets in the sprue cone area. The invention further provides a die-casting machine which is suitable for carrying out this operating method and which can in particular be of the hot-chamber type. - - - - - - - - - - - - - - -

Claims (14)

A method for operating a die-casting machine which has a casting mold (1), a casting chamber (2), a casting piston (3) arranged axially movable in the casting chamber, a melt inlet channel (4) leading into the casting chamber, a shut-off valve (5) in the melt inlet channel and one of the casting chamber has the melt outlet channel (6) leading to the casting mold, wherein - To carry out a respective casting process in a mold filling phase, the casting piston in the casting chamber with the shut-off valve closed is moved from a casting start position (GS) to a filling end position (FP) and, as a result, melt material (14) is pressed into the casting mold via the melt outlet channel and in a subsequent refilling phase The casting piston is moved back into the casting start position and, as a result, melt material is fed to the casting chamber via the melt inlet channel with the shut-off valve open, characterized in that - In the refilling phase of the casting process, the previously opened shut-off valve (5) is closed before the casting piston (3) has reached its casting start position (GS) due to its return movement, and melt material (14) is sucked back in the melt outlet channel (6) by the further return movement of the casting piston will. The method of claim 1, further characterized in that - The casting piston is moved back in the refill phase in the period with the shut-off valve closed at a lower speed than in the previous period with the shut-off valve still open and / or - In the refill phase of the casting process, the previously opened shut-off valve is closed as soon as the casting piston has reached a valve changeover position (VU) due to its return movement. The method of claim 2, further characterized in that a stroke distance between the valve changeover position of the casting piston and the casting start position can be variably specified and / or - In the refill phase of the casting process, the casting piston is stopped in the valve changeover position during a stop period before it is moved back further to its casting start position. Method according to one of Claims 1 to 3, further characterized in that, in the refilling phase of the casting process, the casting mold is kept closed at least as long as the shut-off valve is still open. Method according to one of Claims 1 to 4, further characterized in that, in the refilling phase of the casting process, the casting mold begins to open after the casting piston has reached its casting start position. Method according to one of Claims 1 to 4, further characterized in that, in the refilling phase of the casting process, the casting mold begins to open after the casting piston has reached its valve changeover position and before it has reached its casting start position. The method according to claim 6, further characterized in that in the refilling phase of the casting process the casting piston is stopped in its valve changeover position and is moved on from its valve changeover position to its casting start position as soon as the casting mold has reached a certain casting piston trigger mold opening position when opening. The method according to one of claims 1 to 7, further characterized in that the casting piston is advanced from its casting start position reached in the refill phase of a respective previous casting process in an initial prefilling section of the mold filling phase of a next casting process with the casting mold not yet completely closed into a pre-filling position and only then the The casting mold is completely closed and the casting piston is advanced into its filling end position. A method for operating a die-casting machine which has a casting mold (1), a casting chamber (2), a casting piston (3) arranged axially movable in the casting chamber, a melt inlet channel (4) leading into the casting chamber Has shut-off valve (5) in the melt inlet channel and a melt outlet channel (6) leading from the casting chamber to the casting mold, in particular according to one of Claims 1 to 8, wherein - To carry out a respective casting process in a mold filling phase, the casting piston in the casting chamber with the shut-off valve closed is moved from a casting start position (GS) to a filling end position (FP) and, as a result, melt material (14) is pressed into the casting mold via the melt outlet channel and in a subsequent refilling phase The casting piston is moved back into the casting start position and, as a result, melt material is fed to the casting chamber via the melt inlet channel with the shut-off valve open, characterized in that - The casting piston (3) in the casting chamber (2) is moved forward from an operating start position (BS) to a pre-filling position (VP) during an operational start-up casting process in a pre-filling phase of the operational start-up casting process before the mold filling phase with the shut-off valve (5) closed, and then the shut-off valve opened and the casting piston is moved back into its casting start position. Die casting machine with - a casting mold (1), - a casting chamber (2), - a casting piston (3) arranged axially movable in the casting chamber, - a melt inlet channel (4) leading into the casting chamber, - a shut-off valve (5) in the melt inlet channel, - A melt outlet channel (6) and leading from the casting chamber to the casting mold - a control unit (7) for controlling the casting piston, - The control unit (7) and the shut-off valve (5) being set up to bring the shut-off valve into a closed position (VS) and move the casting piston (3) in the casting chamber (2) forward to carry out a respective casting process in a mold filling phase from a casting start position (GS) to a filling end position (FP) in order to press melt material (14) into the casting mold (1) via the melt outlet channel (6), and in a subsequent refill phase to first bring the shut-off valve into an open position (VO) and controlling the casting piston to move back into the casting start position in order to supply melt 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 set up to bring the shut-off valve (5) back into its closed position (VS) during the refill phase before the casting piston (3) moves back to its casting start position (GS) has reached, and to control the casting piston for sucking back melt material (14) in the melt outlet channel (6) by the further return movement of the casting piston, and / or - The control unit (7) and the shut-off valve (5) are further set up to move the casting piston (3) forward in the casting chamber (2) in a pre-filling phase of the operating start-pouring process before the mold filling phase with the shut-off valve (5) closed during an operational start-up casting process ) from an operating start position (BS) to a pre-filling position (FP) and then to bring the shut-off valve into its open position (VO) and to control the casting piston to move back into its casting start position (GS). Die casting machine according to claim 10, further characterized in that the shut-off valve is designed as a shut-off control valve (5s) and the control unit is set up to control the shut-off control valve (5s). Die casting machine according to Claim 11, further characterized by a valve actuator (16) controlled by the control unit for actuating the shut-off control valve. Die casting machine according to Claim 10, further characterized in that the shut-off valve is designed as a check valve (5 _R ) which is pretensioned into its closed position. Die casting machine according to one of Claims 10 to 13, further characterized by a valve sensor unit (18) for sensing one or more measured variables of the shut-off valve.

Images