EP2804709B1 - Control device for the advancing motion of a casting plunger - Google Patents

Description

The invention relates to a device for controlling the advancing movement of a casting piston in a casting chamber of a cold chamber die casting machine by means of a control signal. Specifically, the invention is concerned with controlling the plunger feed motion during a time referred to herein as a chamber fill movement portion from a partial fill position of the casting plunger with partially filled pouring chamber initial volume to a full fill position of the casting plunger with filled casting chamber residual volume.

In cold chamber die casting, a melt to be cast, typically a melt of a metal alloy of essentially aluminum and / or magnesium and / or zinc, is known to be introduced into a horizontally arranged casting chamber and then conveyed into a casting mold with a casting piston driven hydraulically or in another way , This process is carried out cyclically for the purpose of multiple production of identical products, with each casting cycle once melt is pressed into the mold. In this case, almost exclusively cylindrical casting chambers with a circular cross-section are used. The introduction of the melt into the casting chamber can take place in different ways under atmospheric pressure, superatmospheric or negative pressure, for example by filling via a filling opening of the casting chamber by means of a ladle or by suction by generating a negative pressure in the casting chamber. The quantity of melt introduced into the casting chamber depends on the respective casting mold volume, ie the volume of the part to be cast, so that different fill levels in the casting chamber result depending on the casting and, after introduction of the melt, a certain overlying air volume remains in the horizontally arranged casting chamber cylinder, as long as the casting piston still in an initial position on one casting mold facing away, the rear side of the casting chamber cylinder is located behind a pouring chamber inlet. The term air volume in the present case generally also includes the case that it is an upper partial volume of the casting chamber filled or evacuated with another gas.

In a first phase of the casting-piston feed movement, the casting piston is advanced from its initial position, in which the casting chamber is partially filled, as far as the full filling position, in which the casting chamber volume which is successively reduced by the casting-piston advancing movement is completely filled with the filled-in melt. This is followed by the press-fitting process which is of no further interest in the present case, by means of which the melt from the casting chamber is pressed into the casting mold via a casting-mold outlet facing a casting mold on a front side of the casting-chamber cylinder and the subsequent so-called casting run. During the initial Kammerfüllungsbewegungsabschnitts results in the problem of unwanted air / gas inclusions in the melt at unfavorable course of the piston feed movement. Such air / gas inclusions in the melt can lead to increased porosity and thus depending on the use or further processing of the casting to unsatisfactory quality of the casting.

Two effects are responsible for this, as illustrated in three sub-images each with a successively advanced in a horizontally arranged casting chamber cylinder 1 casting piston 2 in Fig. 1 respectively. Fig. 2 are illustrated, wherein initially according to the respective uppermost part of the casting chamber 1 is partially filled with a melt material 3 and the casting piston 2 is located on a casting mold facing away, rear side 1a of the casting chamber 1 behind a pouring chamber inlet 4. Fig. 1 shows the emergence of a Wellenüberwurfs 5, ie an overturning wave of the casting piston 2 in the casting chamber 1 forward, ie in the direction of a mold facing, front side 1b of the casting chamber 1, pressed melt. 3 Fig. 2 illustrates the effect of premature wave separation from the casting piston 2 and / or premature wave reflection at a casting facing front end 1c of the casting chamber 1, ie in this unfavorable control of the piston feed movement starts a melt shaft 6 away from the piston 2 to move forward. When this wave 6 reaches the Gießkammerdecke directly or even after reflection, it constricts an air / gas volume 7 on the casting piston 2 from a front Gießkammerauslass 8 from, as in the lower part of Fig. 2 shown. Both effects lead to increased air / gas inclusions, as in the lowest part of Fig. 1 schematically symbolized as bubbles 9 in the case of the wave flashover.

The invention is based on the technical problem of providing a device of the type mentioned above, with which the advancing movement of the casting piston can be controlled specifically in the chamber filling movement section so that the amount of air / gas inclusions in the melt can be reduced or minimized, which typically too reduced porosity in the finished casting leads.

The invention solves this problem by providing a control device having the features of claim 1.

In the control device according to the invention, a respective course of an actuating signal is provided for different predetermined sets of values of a plurality of process parameters influencing the melt movement in the casting chamber during the chamber filling movement section, here also briefly referred to as parameters, with which it controls the advancing movement of the casting piston during the chamber filling movement section from an initial one Partial filling position with partially filled casting chamber initial volume up to the full filling position with filled residual casting chamber volume controlled. The control waveforms provided are those which determine that one of them best fits the parameter value set in question. "Best fitting" is to be understood here as meaning that the control signal curve assigned to the parameter value set in question leads to that course of the piston feed movement which, in the current situation described by the relevant parameter value set, better than all the other contours of the piston feed motion considered the undesirable effects of wave flashover and Luftvolumenabschnürung reduces or avoids. In addition to this primary quality criterion, the definition as "best fitting" of course also taking into account usual, relevant for the casting process criteria, such as the least possible time required for the casting cycle and thus for the piston feed movement. By choosing this best-fitting control waveform, therefore, the air / gas input into the melt and thus the porosity in the casting for each casting cycle can be kept as low as possible without significantly slowing the casting cycle compared to conventional Gießprozesssteuerungen.

The control device according to the invention is accordingly set up to apply this best-fitting control signal curve as a function of values of the process parameters present at the beginning of a casting cycle. For this purpose, it can preferably be provided that the possible best-fitting control signal waveforms for different predetermined sets of values of the parameters considered are determined in advance, ie before the runtime of the casting process or casting cycle, and stored in the control device. The control device then selects for each casting cycle the best suited to the current parameter value set control waveform for controlling the Gießkolbenvorschubbewegung during the Kammerfüllungsbewegungsabschnitts out. This preliminary determination of different courses of the piston feed movement, ie different courses of the relevant actuating signal, can be carried out empirically on the real object or preferably systematically and thus deterministically by means of appropriate computer simulations with suitable calculation models. The latter makes it possible to carry out a comparatively large number of "trials" with varying values of the relevant process parameters. When the simulation is performed prior to the runtime of the casting process, the computation time is not limited to the typical casting cycle time, which allows the use of a relatively computationally intensive model that comparatively describes the melt flow ratios in the casting chamber during the piston advancement movement. The simulated model system may in particular also be a simulated closed-loop control system with a controller which attempts to correct computationally recorded deviations from a desired melt flow characteristic with corresponding controller interventions. In this way, a suitable for the respective initial condition, as described by the currently used parameter value set best fitting control waveform can be determined very accurately using model-based control loop simulation. Alternatively, a direct determination of the provided control signal waveform during the term of the casting process can be provided.

The plurality of process parameters influencing the melt movement in the casting chamber during the chamber filling movement section comprises at least one parameter relating to the casting chamber geometry, at least one parameter relating to the fill quantity of melt material in the casting chamber, at least one parameter relating to the casting mold and / or at least one casting chamber and / or the melt temperature parameter. It turns out that taking into account one or more of these parameters already very useful control signal waveforms for the piston feed motion win, which avoid the unwanted effects regarding wave ripples or premature wave separation / wave reflection as far as possible. Depending on the application, one or more additional parameters can be taken into account. In the present case, each parameter is to be understood in such a way that, depending on the application, it may contain current values and / or values derived from one or more preceding casting cycles and / or values determined from such values, each of which is metrologically or computationally derived values can.

In a further development of the invention, the plurality of process parameters more particularly comprises at least one casting chamber length parameter, at least one casting chamber height parameter, at least one casting chamber fill level parameter, at least one melt temperature parameter, at least one pouring chamber temperature parameter and / or at least one melt viscosity parameter and Optionally, one or more additional parameters depending on the application. The geometry parameters describe the spatial boundary conditions for the melt movement in the casting chamber, the temperature / viscosity parameters describe the flow behavior of the melt and possibly also any boundary layer problems such as the so-called boundary layer solidification of the melt on the casting chamber inner wall.

In an advantageous development of the invention, the control signal waveforms provided are grouped into a plurality of types having a different number of successive stages, each stage representing an associated increase in melt height on the casting piston. This shows that, for example, depending on Schmelzenfüllmenge and thus filling level of the casting a single or multi-stage control waveform is favorable, each stage includes the melt level on the piston initially by a predetermined amount to raise faster and then to keep substantially constant or possibly slower to change. The grouping of all possible control signal waveforms in a discrete set of courses with different number of stages also has advantages in terms of storage space for storing previously determined, best-fitting control waveforms, with quick access to the stored data to select the best matching control waveform and with respect to the correspondingly stepped feed rate of the casting.

In a further embodiment of this aspect of the invention, each level is set so that it specifies an initially accelerated casting piston movement followed by a casting piston movement with a speed profile, which is determined from a predetermined course of a height of the melt material on the casting piston. Typically, this predetermined further course of melt height on the casting piston implies that the melt height, after having been relatively quickly raised to a higher level by the initial accelerated piston advance movement, is then substantially maintained at this new level or at least significantly more slowly increased further. It turns out that this connection of the piston feed movement to a specific time profile of the melt height on the casting piston can lead to very good, best-matching control signal curves for the piston feed movement. In addition, this offers the optional possibility of also intervening in the process of the piston feed movement by ongoing sensory detection of the melt height at the casting piston.

In a further development of the invention, the control signal waveforms provided are obtained by a model-based closed loop simulation system before or alternatively during a runtime of the casting piston feed movement, with the advantages indicated above. A preliminary determination allows the use of larger computer capacities and thus more accurate computational models. An alternative determination directly at runtime allows the consideration of any current disturbances may still during the casting cycle.

In a further embodiment of this aspect of the invention, the model-based simulation control loop system is integrated into the control device. It is thereby at the site of the control device, i. typically at the location of the associated casting machine, which is particularly favorable for the cases that a determination of the best matching control signal waveform is provided directly to the casting process or the casting machine user is to be able to determine even best-fitting control signal waveforms by model-based control loop simulation for the casting machine system in question.

Fig. 1

schematische Längsschnittansichten einer Gießkammer einer Kaltkammer-Druckgießmaschine in drei aufeinanderfolgenden Vorschubstellungen eines konventionell gesteuerten Gießkolbens, wobei ein Wellenüberwurf auftritt,

Fig. 2

drei schematische Längsschnittansichten entsprechend Fig. 1 für einen Fall einer konventionellen Gießkolben-Vorschubsteuerung, bei der eine vorzeitige Wellenablösung und/oder Wellenreflexion auftritt,

Fig. 3

ein Blockdiagramm einer erfindungsgemäßen Steuerungsvorrichtung,

Fig. 4

ein Blockdiagramm einer vorteilhaften Realisierung für einen Stellsignaltypen-Speicher der Steuerungsvorrichtung von Fig. 3 und

Fig. 5

schematische Längsschnittansichten einer Gießkammer einer Kaltkammer-Druckgießmaschine in aufeinanderfolgenden Vorschubstellungen eines mit der erfindungsgemäßen Steuerungsvorrichtung vorbewegten Gießkolbens.

Advantageous embodiments of the invention and the conventional examples explained above for better understanding thereof are shown in the drawings. Hereby show:

Fig. 1

schematic longitudinal sectional views of a casting chamber of a cold chamber die casting machine in three successive feed positions of a conventionally controlled casting piston, wherein a Wellenüberwurf occurs,

Fig. 2

three schematic longitudinal sectional views accordingly Fig. 1 for a case of a conventional plunger feed control in which premature shaft separation and / or wave reflection occurs,

Fig. 3

a block diagram of a control device according to the invention,

Fig. 4

a block diagram of an advantageous implementation for a Stellelltignyppen-memory of the control device of Fig. 3 and

Fig. 5

schematic longitudinal sectional views of a casting chamber of a cold chamber die casting machine in successive feed positions of a casting piston advanced with the control device according to the invention.

Hereinafter, advantageous embodiments of the invention will be explained in more detail with reference to the corresponding figures. In the figures, identical or functionally equivalent elements are designated by the same reference numerals for easier understanding.

In the Fig. 3 Control device illustrated in block diagram form serves to control the advancing movement of a casting piston of a casting unit of conventional design for a cold chamber die casting machine. Such a conventional pouring unit includes a typically cylindrical casting chamber of circular cross section, which is arranged with a horizontal cylinder longitudinal axis in the casting machine. The casting chamber and the casting piston may in particular be of the type described above Fig. 1 and 2 is explained. In this type of construction, the upper pouring-chamber side 1a has the filling opening 4 at the top, ie the pouring-chamber inlet, via which, for example, the melt material 3 is filled into the pouring chamber 1 in a predetermined metering quantity by means of a ladle. In the same way, the invention is also suitable for alternative designs of the casting unit, in which the melt material is sucked by means of negative pressure in the casting chamber or pressed by means of positive pressure in the casting chamber. On its front side 1b, the casting chamber 1 has the casting chamber outlet 8 in its upper region. During the press-in process, the molten material 3 is moved over the chamber outlet by advancing the casting piston 2 8 and the subsequent casting run pressed into the mold, to form there the casting. In this case, the chamber filling movement section explained above forms a first section of this piston movement up to the point in time at which the residual volume of the casting chamber 1 successively reduced by the advancing casting piston 2 substantially corresponds to the volume of filled melt material 3, ie to which the casting chamber residual volume is completely filled Melt material 3 is filled and the previously additionally contained in the casting chamber 1 air / gas volume over the Gießkammerauslass 8, the casting and provided for this purpose vents in the mold was almost completely removed from the casting chamber 1. As already mentioned, the invention specifically includes a characteristic design of the piston advancing movement control device in this initial chamber filling moving section. Moreover, the control device can be realized in any suitable manner, as is known per se for Gießkolbensteuerung in cold chamber die casting machines.

As in Fig. 3 illustrated, the control device to a data memory 10, in which a plurality of possible Stellellsignalverläufen is stored. For the respective casting cycle, the control device uses one of these actuating signal courses and thus controls the piston feed movement, in particular in said chamber filling movement section. This casting cycle is in Fig. 3 symbolizes as a real process 11, which is controlled by the selected actuating signal S.

The control device selects the actuating signal S as a suitable for the respective casting cycle according to predetermined criteria control signal. For this purpose, a corresponding selection logic 12 is implemented in it. Via an input stage 13 of the control device, the selection logic 12 for the respective casting cycle becomes a set of values a number m of predeterminable process parameters P ₁ , ..., P _m supplied, which describes the initial conditions of the upcoming casting cycle, as far as they are relevant for achieving a desired, recognized as favorable course of the piston feed movement in the chamber filling movement section. In particular, this desired, optimized control of the piston advance in this section at least largely avoid the above unfavorable explained effects of melt flow dynamics in the casting chamber, which lead to increased air / gas inclusions in the melt material, in particular those in the Fig. 1 and 2 Illustrated effects of Wellenüberwurfs and premature Wellenablösung or constriction of a piston-side air / gas volume.

The respectively considered as relevant process parameters P _i (i = 1, ..., m) are adjusted to the particular application and include at least one Gießkammergeometrieparameter, at least one Füllmengenparameter, at least one Gießformparameter and / or at least one Gießkammertemperatur- or melt temperature parameters. Typical casting chamber geometry parameters are, for example, the casting chamber length and the casting chamber height. The at least one filling quantity parameter describes the proportion to which the casting chamber volume is initially filled with the melt material. Specifically, this may be, for example, an initial fill level, a fill level as the ratio of the initial fill level to the maximum possible fill level, ie the casting chamber diameter, or the detected weight or volume of melt material introduced into the casting chamber. With the at least one Gießformparameter the influence of the mold can be described, in particular their minimum or maximum mold venting time, which determines how long the process of air / gas displacement in the casting chamber should last at least or maximum. The temperature and / or viscosity parameters describe the flow behavior of the melt and possibly also boundary layer effects, such as edge solidification or partial solidification of melt material on the casting chamber inner wall or in the interior of the melt.

Each such parameter may include, as needed, current values and / or values derived from one or more previous casting cycles and / or combinations of such current and / or past values. The individual parameter values may be measured values and / or calculated or estimated values. Thus, e.g. the at least one fill quantity parameter comprises an estimate for the current fill level and / or one or more measured or calculated actual fill level values from past casting cycles. Thus, at the time of the respective casting cycle, depending on the current machine state and its history, the current initial state, insofar as it is relevant for the piston advance movement considered here, can be described sufficiently accurately as an m-dimensional parameter space and fed via the input stage 13 as input information to the selection logic 12.

For the provision of suitable for different starting situations control signal waveforms, as in the embodiment of Fig. 3 are stored in the memory 10, there are several options, which will be discussed in more detail below.

In principle, the two alternatives come into consideration to provide the actuating signal for piston movement control to be used for the current casting cycle before or during the runtime of the casting process. The following will first discuss an implementation for a pre-runtime deployment. In an advantageous implementation, the acquisition of the best-fitting control signal waveforms, as they are then stored in the control signal memory 10, carried out by model-based computer simulation before the process duration. This computer simulation contains a model control loop, which includes a simple calculation model for precontrol determination and a high-precision calculation model for the real process as well as a model controller. Although, as an alternative to such a model control loop, a pure precontrol on the basis of a simple computational model without controller is possible, but the addition of the controller makes it possible to achieve a higher accuracy or better approximation of the real process and to use a relatively simple model for precontrol. The model controller supplements the control signal supplied by the precontrol to the actuating signal for the highly accurate mathematical model as a function of a deviation of a target profile supplied by the precontrol and of an actual course of one or more process variables used by the highly accurate mathematical model. The best-fitting control signals resulting from the mentioned process parameters, as obtained from this model-based control loop simulation, are then stored in the memory 10 as described and are available to the control device at the runtime of the casting process.

Under a best-fitting control signal waveform is, as already mentioned above, understood a control signal waveform through which thus controlled piston feed movement in Kammerfüllungsbewegungsabschnitt leads to a most favorable according to predetermined quality criteria casting and in particular leads to a behavior of the melt flow in the casting chamber, in which the above-mentioned effects of Wellenüberwurf and air / Gasabschnürung due to premature wave separation and / or wave reflection wholly or at least largely avoided, on the other hand, the casting cycle and thus the piston feed motion should proceed as quickly as possible. As the basis of the simple model for the pilot control design suitable modified shallow water equations come to describe the melt flow dynamics in the casting chamber into consideration, whereby fluid reflections at the front casting chamber end and also, to a good approximation, the usually circular casting chamber cross-section are taken into account. In this case, the Gießkammerdecke can be included as height restriction for the melt movement in the pilot control design, as well as the need for the position of the filling opening of the casting chamber, there to prevent leakage of melt at the beginning of casting piston movement safely.

Since in the variant considered here the simulation is carried out before the process run time, the simulation calculation is not subject to the immediate duration limitation of the real casting cycle. This allows the use of a comparatively accurate calculation model, whereby the quality of the previously determined best-fitting control signal waveforms for the real process can be significantly increased.

Thus, this run-time simulation using a model control loop can be used to determine very accurate, best-fitting control signal waveforms that can then be used for the real process as part of a pure control. A real regulation of the real process is basically possible in principle, however, is usually excluded in practice for the casting piston feed movement process considered here, if only because e.g. the recovery and return of the necessary control variable actual values is not sufficiently fast or too expensive. This is especially true for smaller machines, which have such short casting cycle times that from today's point of view a collection and control technical utilization of the required measured values is not practicable.

An alternative possibility provides for a corresponding model-based control loop simulation during the runtime of the casting process, in which case the control signal obtained by the simulation is used directly for the control the piston feed movement is used in the real process, which eliminates the control signal memory. In order to enable the simulation at runtime, the simple model for the precontrol and the high-precision computational model depicting the real process are to be selected appropriately, so that the simulation calculations can proceed sufficiently fast. Compared to a simulation before runtime, this means the use of higher computational capacities and / or the use of a simpler computational model or, as a whole, a simpler closed-loop control model.

The embodiment of Fig. 3 refers, as mentioned, to the embodiment in which a plurality n of best fitting control signals for a possibly larger number of sets of the considered process parameters P ₁ , ..., P _{m determined} beforehand, for example by the mentioned model-based control loop simulation and then in memory 10 has been filed. As is clear from the above explanations of the process parameters P ₁ ,..., P _m , there are such process parameter sets in a correspondingly m-dimensional parameter space even in the case where a special, identical casting is produced in multiple successive casting cycles, since in any case, a part of these process parameters can vary from one casting cycle to a casting cycle due to the process. For each casting cycle, the selection logic 12 can use appropriate criteria to determine a number p of selection coordinates K ₁ ,..., K _p for whose combinations the corresponding best-fitting control signals are generated individually beforehand in corresponding simulation processes. The control signal memory 10 then comprises a p-dimensional selection coordinate space for the plurality n of best-fitting control signal waveforms, as in FIG Fig. 3 illustrated, wherein the number p is less than or equal to the number m. It may be expedient to map as many of the parameters P ₁ ,..., P _m as few selection coordinates K ₁ ,..., K _p as possible, by the number n of possible ones For reasons of memory requirements and / or the previous computational effort to keep control signal waveforms as low as possible.

It should be mentioned at this point that, in particular in the case of a simulation prior to the runtime of the casting process, by employing a comparatively high-precision computational model and a high-performance simulation tool, virtually all essential parameters relevant to the real process of the piston-advancing movement during the chamber-filling-movement section can be taken into account. especially viscous and thermal effects such as viscosity variation and partial solidification. If necessary, a three-dimensional velocity field can be used to describe the melt flow dynamics in the casting chamber, which takes the circular casting chamber cross-section and vertical flows into account almost completely.

Investigations by the inventors have shown that the aforementioned unfavorable effects of wave throwing and constriction of a piston-side air / gas volume can be reduced or avoided in particular by a progression of the piston feed movement, which results in a stepped increase in the piston-side melt fill level in the casting chamber. These results make it possible to group the multiplicity n of determined best-fitting control signals in the p-dimensional space of the selection coordinates K ₁ ,..., K _p in groups of control signal profiles, in the present case also referred to as control signal trajectory types, with different numbers of such excitation stages. This simplifies the structure of the control signal waveform data to be stored in the memory 10 and improves or accelerates the selection of the respectively best-matching control signal waveform by the selection logic 12 on the basis of the input parameters P ₁ ,..., P _m .

For this purpose, for each set of process parameters P ₁ ,..., P _m in the preliminary determination of the best-matching control signal waveforms it is determined which trajectory type is best suited, ie with which number of such excitation stages the piston feed motion is to be controlled in this situation in order to achieve the desired best possible result achieve. Accordingly, this information is stored in the memory 10, see Fig. 4 , During the casting process, the selection logic 12 then decides on the basis of the supplied process parameter input information according to which stage type of the control signal curve the piston feed movement is to take place in the current casting cycle.

Each of said excitation stages represents a corresponding part of the piston feed movement, in which initially the piston is advanced relatively quickly in order to raise the Schmelzenfüllhöhe on the piston from a previous level to a predetermined higher level. Thereafter, a speed profile is predetermined for the piston advance, which is determined from a predetermined course of the melt material height at the casting piston, this predetermined course typically includes that the Schmelzenfüllhöhe on the piston is kept substantially constant or at best increased in time relatively slowly. The number of stages to use varies e.g. depending on the degree of filling. In the case of a lower initial melt level in the chamber, a piston advance is selected with more stages than in the case of higher fill levels.

Fig. 5 illustrates an example with a two-stage excitation. The example of Fig. 5 is illustrated by the casting chamber 1 and the casting piston 2, as shown in the Fig. 1 and 2 and the description thereof above, to which reference can be made here. In the example of Fig. 5 assumes the melt material 3 initially before the onset of piston movement a height H ₀ in the casting chamber 1, see the top part. Starting from that will the piston 2 initially advances acceleratedly to generate a first stage 3a of wave excitation of the liquid melt material 3, by which the Schmelzenfüllhöhe on the piston 2 is raised from the initial height H ₀ to a suitably predetermined greater height H ₁ . Subsequently, the piston 2 is advanced with reduced acceleration or at substantially constant speed such that the melt filling level at the piston 2 remains substantially at the height level H _{1 of} the first stage 3a, with the corresponding wave excitation propagating forward, as shown in the second and third upper part of Fig. 5 seen.

After a predetermined period of time, a second stage 3b for the wave excitation of the melt material 3 in the chamber 1 is generated by appropriate control of the piston feed. For this purpose, the piston 2 is again initially moved with greater acceleration until the melt level on the piston 2 has reached a predetermined, new, higher level H ₂ . In the example shown, the choice of a two-stage control waveform corresponds to this new height H _{2 of} the total chamber height, ie the diameter D of the casting chamber 1, see the middle part of image in Fig. 5 , Subsequently, the piston 2 is then again advanced with less acceleration or at a substantially constant speed such that the melt material 3 on the piston 2 substantially retains the new height level H ₂ , with the second wave excitation stage 3 b propagating forward, see the third lowest drawing in FIG Fig. 5 ,

In the last excitation level, in the example of Fig. 5 the second stage, thus the remaining air / gas volume, which is still the piston side in the chamber 1 between the melt material 3 and the chamber ceiling, from the piston side towards the casting chamber, ie Gießkammerauslass 8, displaced. By suitable coordination of the individual excitation levels, as for example by the mentioned model-based Control cycle simulation can be determined before the duration of the casting process, it can be achieved that the individual excited wave levels, in the example of Fig. 5 the two stages 3a and 3b, meet at the casting chamber end or unite and in this way a virtually complete displacement of the air / gas volume from the casting chamber 1 is effected, as in the second and lowest part of Fig. 5 illustrated. The determination of the associated best-fitting control signal waveforms is in this case completely systematic possible, since it can be computationally determined at what speed the individual wave excitation stages proceed in dependence on their respective height in the casting chamber.

A significant influencing factor, which can lead to increased air / gas inclusions in the melt 3, is a dosage inaccuracy of, for example, ± 5% volume error of the melt 3 introduced into the chamber 1. In order to take account of this factor, the gradual increase in the piston side takes place Melting height such that even at maximum predetermined metering error, the piston-side melt height remains safely below the Gießkammerdecke in all stages except the last stage. The last stage is relatively insensitive to metering inaccuracies. For a height error of the penultimate stage is all the more uncritical with respect to the presettable by the controller piston speed, the closer this penultimate step height is located on the Gießkammerdecke. The grading is therefore chosen so that the piston-side melt height in the penultimate stage on the one hand even with maximum overdose a predetermined minimum distance from the Gießkammerdecke complies and on the other hand does not exceed a predetermined maximum distance from the Gießkammerdecke even at maximum underdosing, so that through the last wave excitation level just desired complete air / gas displacement is achieved from the piston side. With this stepped control of the piston feed movement can thus the chamber ceiling the casting chamber cylinder systematically included in the determination of the best-fitting control signal waveform and at the same time a sufficient robustness against dosing errors are ensured.

It is understood that, depending on the present values for the beginning considered to be influential relevant process parameters P _1, ..., P _m in addition to the Fig. 5 shown two-stage control and a one-stage or more than two-stage control of the piston feed movement can be provided. In addition to the inclusion of metering errors mentioned above, the viscosity properties of the melt and thermal effects within the casting chamber, such as partial solidification, in which solidified fractions in the melt affect wave propagation, can be systematically included in the determination of the respectively best matching control signal curve for the piston feed movement.

In the described cases, in which the best-fitting control signal waveforms are determined by a model-based closed-loop control system, this model-based simulation closed-loop control system can be integrated into the control device, which is typically located at the place of use of the casting machine. In this case, the control device according to the invention may in turn be integrated in a central machine control of the die casting machine. Alternatively, the model-based closed-loop control system may be implemented outside the control device according to the invention, in which case the best-fitting control signal waveforms supplied by the model-based closed-loop control system are supplied or provided to the control device, for example by the aforementioned dropping in a control signal memory of the control device.

Claims (6)

1. Device for controlling the advancing movement of a casting plunger (2) in a casting chamber (1) of a cold-chamber die casting machine by means of an actuating signal, the advancing movement comprising a chamber filling movement phase from a partial filling position, with a partially filled casting chamber starting volume, to a full filling position, with a filled casting chamber remaining volume,
   characterized in that
   in the device a respective associated progression of the actuating signal is provided for different specified sets of values of a plurality of process parameters that influence the movement of the molten material in the casting chamber during the chamber filling movement phase, which progression is defined as the most suitable actuating signal progression for the particular set of parameter values,
   and the device is designed to use the most suitable actuating signal progression in dependence on values of this plurality of process parameters pertaining at the beginning of a casting cycle for controlling the casting plunger advancing movement during the chamber filling movement phase, the plurality of process parameters including at least one casting chamber geometry parameter, at least one filling amount parameter, at least one casting mold parameter, and/or at least one casting chamber temperature or molten material temperature parameter.
2. Control device as claimed in claim 1, further characterized in that the plurality of process parameters include at least one casting chamber length parameter, at least one casting chamber height parameter, at least one casting chamber filling degree parameter, at least one molten material temperature parameter, at least one casting chamber temperature parameter, and/or at least one molten material viscosity parameter.
3. Control device as claimed in claim 1 or 2, further characterized in that the actuating signal progressions provided are grouped into a plurality of types with a differing number of successive stages of the progression, each stage representing an associated rise in the height of the molten material at the casting plunger.
4. Control device as claimed in claim 3, further characterized in that each stage of the progression specifies an initially accelerated casting plunger movement followed by a casting plunger movement with a velocity progression that corresponds to a progression determined in advance for a height of the molten material at the casting plunger.
5. Control device as claimed in any one of claims 1 to 4, further characterized in that the actuating signal progressions provided are obtained by a model-aided closed-loop control simulation system before or during a running time of the advancing movement of the casting plunger.
6. Control device as claimed in claim 5, further characterized in that it includes the model-aided closed-loop control simulation system in integrated form.

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