EP0581786B1 - Method of controlling the casting parameters in a die-casting machine - Google Patents

Method of controlling the casting parameters in a die-casting machine Download PDF

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Publication number
EP0581786B1
EP0581786B1 EP92907302A EP92907302A EP0581786B1 EP 0581786 B1 EP0581786 B1 EP 0581786B1 EP 92907302 A EP92907302 A EP 92907302A EP 92907302 A EP92907302 A EP 92907302A EP 0581786 B1 EP0581786 B1 EP 0581786B1
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Prior art keywords
casting
filling
chamber
casting chamber
molten metal
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EP92907302A
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German (de)
French (fr)
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EP0581786A1 (en
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Friedrich Stummer
Wolfgang Lutz
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Maschinenfabrik Mueller Weingarten AG
Mueller Weingarten AG
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Maschinenfabrik Mueller Weingarten AG
Mueller Weingarten AG
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20Accessories: Details
    • B22D17/32Controlling equipment

Definitions

  • the invention relates to a method for controlling casting parameters in a die casting machine according to the preamble of claim 1.
  • the metal melt is metered as follows: In cold chamber die casting machines, the casting metal is removed from a holding furnace and filled into the casting chamber of the casting set. In manual operation, this is done by scooping the liquid metal with a spoon from the holding furnace and emptying it into the filling opening of the casting chamber. Dosing and loading devices have also become known, by means of which the filling process of the casting chamber with liquid metal can be automated. In Brunhuber (loc. Cit.) Pp. 105 to 110, a device is described that works with a measuring spoon that dips into the holding melt, absorbs a correspondingly measured amount of metal and empties it into the filling opening after transport to the casting chamber. The spoon is adjustable so that it allows an exact dosage of the desired amount of metal. Excess metal flows back into the holding oven when the bucket is raised. The dosing accuracy is specified for a specific device with +/- 0.8% in the dosing range from 0.1 to 15 kg aluminum alloy.
  • the quality of the cast parts is determined by a large number of process parameters.
  • the metering accuracy of the molten metal influences the casting quality to a great extent, whereby negative influences can influence the entire casting process in the sense of an unwanted and unfavorable shift in the starting points of the casting phases, the change in the piston speed and the casting pressure.
  • thermocouples It is also known to use sensors which are designed as thermocouples and register the melt temperature at a certain fill level.
  • This arrangement relates to automatic metering of molten metal in the manufacture of mass castings. It does not concern any regulation of the casting parameters depending on the molten metal in a casting chamber of a cold chamber die casting machine.
  • the method according to the invention with the characterizing features of claim 1 has the advantage over the known methods or devices that a regulation of the casting parameters depending on the level in the casting chamber is created, with an accurate dosing and charging device for the molten metal in the casting chamber Die casting machine is provided.
  • the level of the casting chamber and thus the amount of melt can be determined precisely.
  • the exact level enables exact determination of the so-called machine data.
  • These are, in particular, the response and calculation times of the control or regulation as well as the other working hours of the hydraulic components. This enables the points of application of the changes in the speed of the casting piston in the individual phases of the casting piston and the associated casting pressure to be determined and regulated extremely precisely.
  • the exact lead phase or the exact lead stroke of the casting piston within the casting chamber up to the state of complete filling of the "remaining casting chamber” and thus the beginning of the mold filling phase can thus be determined exactly. This is only possible in that the filling quantity in the chamber volume of the casting chamber can be determined precisely. In this way, the pre-run phase, the mold filling phase and the post-pressure phase of the casting process can be precisely determined and regulated by their timing, which leads to an improvement in the quality of the castings.
  • the most precise determination of the fill level of the molten metal in the casting chamber also enables a most precise dosing and loading process, since this can be regulated on the basis of the fill level measurement.
  • the casting parameters can be calculated and controlled very precisely. These casting parameters are, for example, the triggering of quantity-dependent positions of the casting piston in the lead-up phase and in particular the regulation of the speed of the casting piston. Furthermore, a quantity-dependent triggering of the position of the casting piston in the mold filling phase or the triggering of the mold filling phase can take place. B. again speeds of the casting piston and damping processes can be detected. In the end an exact dosage and thus an exact knowledge of the amount of the melt can cause a precise triggering of the holding phase.
  • the figure shows a schematic representation of a casting chamber in a fixed platen of a die casting machine with a measuring and control device according to the invention for carrying out the method according to the invention.
  • a cold chamber die casting machine not shown, there is a casting chamber 2 with a horizontal longitudinal axis 3 in the fixed platen 1.
  • a casting piston moves from right to left in the figure and presses the molten metal 5 filled into the casting chamber with the melt surface or the melt stand 6 in the direction of the casting mold (not shown) (path "s").
  • the molten metal 5 is through the upper filling opening 7 in the casting chamber z. B. entered by means of a dosing spoon described above.
  • the dosing accuracy with which the molten metal can be fed to the casting chamber is of the order of +/- 1%. This dosing accuracy can only be achieved with great effort with appropriate dosing spoons. Usually only +/- 2% dosing accuracy is achieved with reasonable effort.
  • the filling level of the casting chamber can vary considerably depending on the application. As shown in the figure, it is often more than 50% of the chamber volume, i. H. the melt level 6 lies somewhat above the longitudinal axis 3 of the casting chamber.
  • the chamber volume is reduced by the slow forward stroke of the casting piston until the liquid level 6 of the molten metal reaches the uppermost edge of the casting chamber, i. H. the "remaining volume" of the casting chamber is completely filled with molten metal. Only then does the actual mold filling phase for filling the casting mold begin. When this point in time is reached is determined exclusively by the amount of molten metal poured into the casting chamber. Is z. B. the casting chamber is only 50% full, the casting piston must cover about 50% of its advance stroke to completely fill the casting chamber. If the casting chamber is filled by more than 50%, the advance stroke is already reached after less than 50% of the total stroke.
  • the amount of molten metal poured into the casting chamber also determines the casting piston speed to be set in order to achieve a uniform rise in the molten metal without air pockets.
  • the exact fill level and the determination of the exact amount accordingly determine the exact times of the end of the prefilling phase and the beginning of the mold filling phase.
  • a stationary measuring device 8 is provided according to the invention, which is firmly connected to the platen 1 via a web 9.
  • the fill level 6 of the melt in the casting chamber can be determined spatially above the casting chamber 2 by means of ultrasound or laser.
  • the measuring device 8 with the measuring eye 10 is installed at a distance a from the filling opening 7 of the casting chamber 2, with which it is protected against heat or other damage. Furthermore, this enables unhindered access to the filling opening 7, for example by means of a spoon (not shown). Finally, it is possible to suppress disturbance variables such as shields, etc. in the area of the casting chamber.
  • the measurement of the level or the degree of filling 6 of the melt 5 in the casting chamber 2 by the measuring device 8 with a built-in sensor is carried out continuously or discontinuously by an ultrasound or laser beam 11 as a measuring beam 11, which reflects on the melt surface 6 and is received again as a reflection beam .
  • the transit time of the measuring beam is a measure of the level h in the casting chamber 2.
  • the transit time of the measuring beam or reflection beam is transformed into a path signal which indicates the level.
  • the computer 12 controls the movement of the casting piston via line 13.
  • the level h or melt level 6 in the casting chamber 2 determined in this way, a number of regulations can be carried out during the casting process.
  • the filling process of the molten metal can be monitored directly by continuous measurement, the desired filling quantity can be limited after reaching the desired level.
  • the wave movement within the casting chamber when the melt is poured in can be compensated for by averaging the wave crest and wave trough.
  • strongly fluctuating melting levels 6 can also be averaged mathematically and the actual filling level can thus be determined. Only a completely exact determination of the filling quantity guarantees the correctness of the casting parameters to be set subsequently.
  • the level of the melt in the casting chamber can also be measured after the casting chamber has been filled.
  • the amount in the casting chamber is predetermined by the level 6 reached, so that the casting parameters must be based on this.
  • these are the movement sequence of the casting piston 4 and the advance stroke of the casting piston 4 into the casting chamber to the point until the melt completely fills the entire casting chamber, ie extends to the upper edge of the casting chamber.
  • the subsequent mold filling phase only begins at this precise point in time. The triggering of the mold filling phase is therefore dependent on the quantity of the melt and thus also on the exact position of the casting piston 4 in the casting chamber.
  • the run-up phase ie the phase in which the casting piston 4 compresses the poured metal melt in the casting chamber until the casting chamber 2 is completely filled, is significantly influenced in its course and its speed by the fill level.
  • the triggering of the third phase ie the holding pressure phase, is decisively influenced by the amount of melt present, so that the exact point in time also depends on the filling amount.
  • a device for continuous non-contact level measurement in containers with liquids is known in principle.
  • a sensor emits ultrasonic pulses at a frequency of approximately 46 kHz.
  • the sound waves are reflected by the surface of the liquid and picked up again by the sensor.
  • the transit time of the sound which elapses between the transmission and reception of the sound pulse, is evaluated electronically and passed on to the connected devices as a signal proportional to the fill level.
  • the distance a between the measuring probe 10 and the maximum fill level is given in the order of magnitude a ⁇ 45 to 70 cm. However, other distances can also be set.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Casting Support Devices, Ladles, And Melt Control Thereby (AREA)

Abstract

The invention concerns a method of controlling the casting parameters in the pre-fill, mould-filling and/or dwell pressure phase of the casting process in a cold-chamber die-casting machine, the casting phases being controlled as a function of the travel of a piston, which can be displaced longitudinally inside the casting chamber, in conjunction with the amount of molten metal introduced. In order to ensure precise control of the most diverse casting parameters during the pre-fill, mold-filling or dwell pressure phase of the casting process, the exact amount of molten metal (5) present in the casting chamber (2) is determined without contact by means of an optical measurement device (8), the signal from which is processed in a control device (12).

Description

Die Erfindung betrifft ein Verfahren zur Regelung von Gießparametern in einer Druckgießmaschine nach dem Oberbegriff des Anspruchs 1.The invention relates to a method for controlling casting parameters in a die casting machine according to the preamble of claim 1.

Stand der Technik:State of the art:

Aus der Literaturstelle Ernst Brunhuber: "Praxis der Druckgußfertigung" 3. Aufl., 1980, S. 82 ff. ist die Maschinensteuerung von Druckgießmaschinen bekannt. Gemäß S. 84, 85 dieser Literaturstelle unterscheidet man zwischen Vorlauf-, Formfüll- und Nachdruckphase, wobei der Kolbenhub des Gießkolbens und damit die Metallschmelze in der Gießkammer in jeder Phase geregelt werden. Dabei spielt die Füllmenge in der Gießkammer eine entscheidende Rolle, da z. B. der Beginn der Formfüllphase abhängig ist von der Füllmenge und der Stellung des Gießkolbens.The machine control of die casting machines is known from the literature reference Ernst Brunhuber: "Praxis der Druckgußfertigung", 3rd ed., 1980, p. 82 ff. According to pp. 84, 85 of this literature reference, a distinction is made between the pre-flow, mold filling and holding pressure phases, with the piston stroke of the casting piston and thus the molten metal in the casting chamber being regulated in each phase. The filling quantity in the casting chamber plays a crucial role, since e.g. B. the beginning of the mold filling phase depends on the filling quantity and the position of the casting piston.

Die Dosierung der Metallschmelze geschieht wie folgt:
Bei Kaltkammer-Druckgießmaschinen wird das Gießmetall einem Warmhalteofen entnommen und in die Gießkammer der Gießgarnitur gefüllt. Dies geschieht bei manueller Betriebsweise durch Schöpfen des flüssigen Metalls mit einem Löffel aus dem Warmhalteofen und Entleerung in die Füllöffnung der Gießkammer. Es sind auch Dosier- und Beschickungseinrichtungen bekannt geworden, mittels welchen der Füllvorgang der Gießkammer mit flüssigem Metall automatisiert werden kann. Bei Brunhuber (a.a.O.) S. 105 bis 110 ist eine Vorrichtung beschrieben, die mit einem Dosierlöffel arbeitet, der in die Warmhalteschmelze eintaucht, eine entsprechend bemessene Metallmenge aufnimmt und diese nach Transport zur Gießkammer in die Füllöffnung entleert. Der Löffel ist so verstellbar, daß er eine genaue Dosierung der gewünschten Metallmenge ermöglicht. Überschüssiges Metall fließt dabei beim Hochfahren des Löffels in den Warmhalteofen zurück. Die Dosiergenauigkeit wird für ein bestimmtes Gerät mit +/- 0,8 % im Dosierbereich von 0,1 bis 15 kg Aluminiumlegierung angegeben.
The metal melt is metered as follows:
In cold chamber die casting machines, the casting metal is removed from a holding furnace and filled into the casting chamber of the casting set. In manual operation, this is done by scooping the liquid metal with a spoon from the holding furnace and emptying it into the filling opening of the casting chamber. Dosing and loading devices have also become known, by means of which the filling process of the casting chamber with liquid metal can be automated. In Brunhuber (loc. Cit.) Pp. 105 to 110, a device is described that works with a measuring spoon that dips into the holding melt, absorbs a correspondingly measured amount of metal and empties it into the filling opening after transport to the casting chamber. The spoon is adjustable so that it allows an exact dosage of the desired amount of metal. Excess metal flows back into the holding oven when the bucket is raised. The dosing accuracy is specified for a specific device with +/- 0.8% in the dosing range from 0.1 to 15 kg aluminum alloy.

Bei Kaltkammer-Druckgießverfahren wird die Qualität der Gußteile von einer Vielzahl von Verfahrensparametern bestimmt. Dabei beeinflußt die Dosiergenauigkeit der Metallschmelze die Gußqualität in hohem Maße, wobei negative Einflüsse den gesamten Gießvorgang im Sinne einer ungewollten und ungünstigen Verschiebung der Einsatzpunkte der Gießphasen, der Veränderung von Gießkolbengeschwindigkeit und des Gießdrucks beeinflussen können.In cold chamber die casting processes, the quality of the cast parts is determined by a large number of process parameters. The metering accuracy of the molten metal influences the casting quality to a great extent, whereby negative influences can influence the entire casting process in the sense of an unwanted and unfavorable shift in the starting points of the casting phases, the change in the piston speed and the casting pressure.

Um eine hohe Dosiergenauigkeit bei Druckgießmaschinen zu erreichen, ist es aus der DE 84 22 336 U1 bekannt geworden, den Füllstand in der Druckgießform mittels eines Kontaktstiftes zu erfassen, bei welchem die in der Gießform ansteigende Metallschmelze zwei Kontakte kurzschließt und damit ein Signal erzeugt. Dieses Meßsignal kann dann einer Steuerungs- bzw. Regelungseinheit zugeführt und zur Maschinensteuerung herangezogen werden.In order to achieve high dosing accuracy in die casting machines, it has become known from DE 84 22 336 U1 that the fill level in the die casting mold can be achieved by means of a To detect contact pin, in which the molten metal rising in the mold short-circuits two contacts and thus generates a signal. This measurement signal can then be fed to a control or regulating unit and used for machine control.

Bekannt ist auch die Verwendung von Sensoren, die als Thermoelement ausgebildet sind und die Schmelzentemperatur bei einem bestimmten Füllstand registrieren.It is also known to use sensors which are designed as thermocouples and register the melt temperature at a certain fill level.

Die Anbringung derartiger Sensoren in der Gießkammer selbst führt häufig zu unzuverlässigen Ergebnissen, da diese aufgrund der hohen Temperaturen und der rauhen Handhabung in der Gießkammer erheblich strapaziert werden, so daß genaue und reproduzierbare Werte kaum einstellbar sind.The attachment of such sensors in the casting chamber itself often leads to unreliable results, since these are considerably stressed due to the high temperatures and the rough handling in the casting chamber, so that exact and reproducible values can hardly be set.

Darüber hinaus tritt in der Gießkammer häufig eine wellenförmige oder schwappende Bewegung der Schmelze auf, die aufgrund unterschiedlicher Schmelzenhöhen falsche Füllwerte anzeigen kann. Das abgegebene Signal entspricht demnach nicht dem tatsächlich vorhandenen Füllstandspegel. Hierdurch kann eine entsprechende Fehlsteuerung die Folge sein.In addition, a wavy or sloshing movement of the melt often occurs in the casting chamber, which can indicate incorrect fill values due to different melt heights. The signal emitted does not therefore correspond to the level actually present. This can result in a corresponding incorrect control.

Aus der DE 33 44 537 C1 ist weiterhin ein Verfahren zum taktweisen Dosieren einer flüssigen Metallmenge beim Druckgießen bekannt geworden. Bei diesen Verfahren wird eine definierte bemessene Metallmenge über ein Steigrohr aus einem Ofen über einen definierten Druckluftstoß aus einer Konstantdruckwelle der Gießkammer zugeführt. Dieses Verfahren erfordert einen hohen apparativen Aufwand und ein ständiges Kompensieren der Dosierzeit in Abhängigkeit der Ofenfüllung und der Butzenlänge am Werkstück. Eine Regelung der Gießkolbenbewegung ist hiermit nicht vorgesehen.From DE 33 44 537 C1 a method for the intermittent dosing of a liquid amount of metal during die casting has become known. In this process, a defined, measured quantity of metal is fed from a furnace via a riser pipe via a defined burst of compressed air from a constant pressure wave to the casting chamber. This process requires a lot of equipment and constant compensation of the dosing time depending on the furnace filling and the slug length on the workpiece. This does not provide for regulating the movement of the plunger.

Aus der DE 23 07 846 A1 ist weiterhin ein Verfahren zum selbständigen Entnehmen von schmelzflüssigem Metall bekannt geworden, bei welchem die Dosierung der Schmelzemenge über eine Gewichtsmessung erfolgt. Über eine kombinierte Druckbeaufschlagung des Warmhalteofens und einer Gewichtsmessung sowohl der vom Warmhalteofen abgegebenen als auch von der Gießform aufgenommenen Gießmenge wird der genaue Füllstand erfaßt. Dabei ist ein zusätzliches Abtasten des Gußsteigers oder direkt der Gießform während des Gießvorgangs über eine auf die Gießform gerichtete Fotozelle vorgesehen, die mit einer Steueranlage verbunden ist. Der Gießvorgang soll dann über die Fotozelle (Infrarotauge) überwacht werden. Nach Erreichen eines Sollwerts, z. B. in der Gießform, soll ein Ventil, z. B. in der Druckleitung, geöffnet werden. Hierdurch erfolgt ein starkes Absenken des Drucks, so daß ein Überschwappen des schmelzflüssigen Metalls vermieden wird.From DE 23 07 846 A1 a method for the independent removal of molten metal has also become known, in which the quantity of melt is metered by means of a weight measurement. The exact filling level is determined by means of a combined pressurization of the holding furnace and a weight measurement of the casting quantity emitted by the holding furnace and also taken up by the casting mold. Additional scanning of the casting riser or directly of the casting mold is provided during the casting process via a photocell which is directed towards the casting mold and is connected to a control system. The casting process should then be monitored via the photocell (infrared eye). After reaching a setpoint, e.g. B. in the mold, a valve, for. B. in the pressure line. This results in a sharp drop in pressure so that the molten metal does not spill over.

Diese Anordnung betrifft eine automatische Dosierung von schmelzflüssigem Metall bei der Herstellung von Massengußstücken. Sie betrifft keine Regelung der Gießparamater in Abhängigkeit der Metallschmelze in einer Gießkammer einer Kaltkammer-Druckgießmaschine.This arrangement relates to automatic metering of molten metal in the manufacture of mass castings. It does not concern any regulation of the casting parameters depending on the molten metal in a casting chamber of a cold chamber die casting machine.

Vorteile der Erfindung:Advantages of the invention:

Das erfindungsgemäße Verfahren mit den kennzeichnenden Merkmalen des Anspruchs 1 hat gegenüber den bekannten Verfahren bzw. Einrichtungen den Vorteil, daß eine Regelung der Gießparameter in Abhängigkeit der Füllstandsmenge in der Gießkammer geschaffen wird, wobei eine genaue Dosier- und Beschickungseinrichtung für die Metallschmelze in die Gießkammer einer Druckgießmaschine vorgesehen ist. Hierdurch kann der Füllstand der Gießkammer und damit die Schmelzenmenge genauestens bestimmt werden. Der genaue Füllstand ermöglicht eine exakte Bestimmung der sogenannten Maschinendaten. Dies sind insbesondere die Reaktions- und Berechnungszeiten der Steuerung bzw. Regelung sowie die sonstigen Arbeitszeiten der Hydraulikbauelemente. Damit können die Einsatzpunkte der Veränderungen von Gießkolbengeschwindigkeit in den einzelnen Phasen des Gießkolbens sowie der zugehörige Gießdruck äußerst präzise bestimmt und geregelt werden. Die exakte Vorlaufphase bzw. der exakte Vorlaufhub des Gießkolbens innerhalb der Gießkammer bis zu dem Zustand der vollständigen Füllung der "Restgießkammer" und damit der Beginn der Formfüllphase kann damit exakt bestimmt werden. Dies ist nur dadurch möglich, daß die Füllmenge im Kammervolumen der Gießkammer genauestens bestimmbar ist. Hierdurch können Vorlaufphase, Formfüllphase und Nachdruckphase des Gießprozesses von ihrem Zeitablauf exakt bestimmt und geregelt werden, was zu einer Qualitätsverbesserung der Gußteile führt.The method according to the invention with the characterizing features of claim 1 has the advantage over the known methods or devices that a regulation of the casting parameters depending on the level in the casting chamber is created, with an accurate dosing and charging device for the molten metal in the casting chamber Die casting machine is provided. Hereby the level of the casting chamber and thus the amount of melt can be determined precisely. The exact level enables exact determination of the so-called machine data. These are, in particular, the response and calculation times of the control or regulation as well as the other working hours of the hydraulic components. This enables the points of application of the changes in the speed of the casting piston in the individual phases of the casting piston and the associated casting pressure to be determined and regulated extremely precisely. The exact lead phase or the exact lead stroke of the casting piston within the casting chamber up to the state of complete filling of the "remaining casting chamber" and thus the beginning of the mold filling phase can thus be determined exactly. This is only possible in that the filling quantity in the chamber volume of the casting chamber can be determined precisely. In this way, the pre-run phase, the mold filling phase and the post-pressure phase of the casting process can be precisely determined and regulated by their timing, which leads to an improvement in the quality of the castings.

Die genaueste Ermittlung des Füllstandes der Metallschmelze in der Gießkammer ermöglicht umgekehrt auch einen genauesten Dosier- und Beschickungsvorgang, da dieser aufgrund der Füllstandsmessung geregelt werden kann. Liegen die genauesten Füllstandswerte der Schmelze in der Gießkammer vor, so können die Gießparameter genauestens errechnet und geregelt werden. Diese Gießparameter sind beispielsweise die Auslösung von mengenabhängigen Positionen des Gießkolbens in der Vorlaufphase und insbesondere die Regelung der Geschwindigkeit des Gießkolbens. Weiterhin kann hierdurch eine mengenabhängige Auslösung der Position des Gießkolbens in der Formfüllphase bzw. die Auslösung der Formfüllphase erfolgen, wobei z. B. wiederum Geschwindigkeiten des Gießkolbens und Dämpfungsvorgänge erfaßbar sind. Schließlich kann eine genaueste Dosierung und damit eine genaue Kenntnis der Menge der Schmelze eine genaueste Auslösung der Nachdruckphase bewirken.Conversely, the most precise determination of the fill level of the molten metal in the casting chamber also enables a most precise dosing and loading process, since this can be regulated on the basis of the fill level measurement. If the most accurate fill level values of the melt are available in the casting chamber, the casting parameters can be calculated and controlled very precisely. These casting parameters are, for example, the triggering of quantity-dependent positions of the casting piston in the lead-up phase and in particular the regulation of the speed of the casting piston. Furthermore, a quantity-dependent triggering of the position of the casting piston in the mold filling phase or the triggering of the mold filling phase can take place. B. again speeds of the casting piston and damping processes can be detected. In the end an exact dosage and thus an exact knowledge of the amount of the melt can cause a precise triggering of the holding phase.

In den Unteransprüchen sind vorteilhafte Weiterbildungen und Verbesserungen des erfindungsgemäßen Verfahrens angegeben. In der nachfolgenden Beschreibung eines Ausführungsbeispiels für das erfindungsgemäße Verfahren sind weitere Einzelheiten und Vorteile der Erfindung näher erläutert.Advantageous further developments and improvements of the method according to the invention are specified in the subclaims. The following description of an exemplary embodiment of the method according to the invention explains further details and advantages of the invention.

Die Figur zeigt eine schematische Darstellung einer Gießkammer in einer festen Aufspannplatte einer Druckgießmaschine mit einer erfindungsgemäßen Meß- und Regeleinrichtung zur Durchführung des erfindungsgemäßen Verfahrens.The figure shows a schematic representation of a casting chamber in a fixed platen of a die casting machine with a measuring and control device according to the invention for carrying out the method according to the invention.

Beschreibung der Erfindung:Description of the invention:

Das erfindungsgemäße Verfahren wird anhand der Figurendarstellung wie folgt näher erläutert:
In einer nicht näher dargestellten Kaltkammer-Druckgießmaschine befindet sich in der festen Aufspannplatte 1 eine Gießkammer 2 mit horizontaler Gießkammerlängsachse 3. In der Gießkammer 2 bewegt sich ein Gießkolben in der Figur von rechts nach links und drückt die in die Gießkammer eingefüllte Metallschmelze 5 mit der Schmelzenoberfläche bzw. den Schmelzestand 6 in Richtung zur nicht näher dargestellten Gießform (Weg "s"). Die Metallschmelze 5 wird durch die obere Füllöffnung 7 in die Gießkammer z. B. mittels eines eingangs beschriebenen Dosierlöffels eingegeben.
The method according to the invention is explained in more detail using the figure representation as follows:
In a cold chamber die casting machine, not shown, there is a casting chamber 2 with a horizontal longitudinal axis 3 in the fixed platen 1. In the casting chamber 2, a casting piston moves from right to left in the figure and presses the molten metal 5 filled into the casting chamber with the melt surface or the melt stand 6 in the direction of the casting mold (not shown) (path "s"). The molten metal 5 is through the upper filling opening 7 in the casting chamber z. B. entered by means of a dosing spoon described above.

Wie eingangs beschrieben, besteht die Dosiergenauigkeit, mit welcher die Metallschmelze der Gießkammer zuführbar ist, in der Größenordnung von +/- 1 %. Diese Dosiergenauigkeit kann nur mit hohem Aufwand bei entsprechenden Dosierlöffeln erzielt werden. Üblicherweise werden nur +/- 2 % Dosiergenauigkeit mit vertretbarem Aufwand erzielt.As described at the beginning, the dosing accuracy with which the molten metal can be fed to the casting chamber is of the order of +/- 1%. This dosing accuracy can only be achieved with great effort with appropriate dosing spoons. Usually only +/- 2% dosing accuracy is achieved with reasonable effort.

Der Füllgrad der Gießkammer kann je nach Anwendungsfall beträchtlich schwanken. Wie in der Figur dargestellt, beträgt er oftmals mehr als 50 % des Kammervolumens, d. h. der Schmelzestand 6 liegt etwas oberhalb der Gießkammer-Längsachse 3. Während der sogenannten Vorlaufphase wird das Kammervolumen durch den langsamen Vorlaufhub des Gießkolbens soweit verkleinert, bis der Flüssigkeitsspiegel 6 der Metallschmelze den obersten Rand der Gießkammer erreicht, d. h. das "Restvolumen" der Gießkammer vollständig mit Metallschmelze gefüllt ist. Erst ab diesem Zeitpunkt beginnt die eigentliche Formfüllphase zur Befüllung der Gießform. Wann dieser Zeitpunkt erreicht ist, ergibt sich ausschließlich aus der in die Gießkammer eingefüllten Metallschmelzenmenge. Ist z. B. die Gießkammer nur zu 50 % gefüllt, so muß der Gießkolben etwa 50 % seines Vorlaufhubes zurücklegen, um die Gießkammer vollständig zu füllen. Ist die Gießkammer um mehr als 50 % gefüllt, so ist der Vorlaufhub bereits nach weniger als 50 % des Gesamthubs erreicht.The filling level of the casting chamber can vary considerably depending on the application. As shown in the figure, it is often more than 50% of the chamber volume, i. H. the melt level 6 lies somewhat above the longitudinal axis 3 of the casting chamber. During the so-called preliminary phase, the chamber volume is reduced by the slow forward stroke of the casting piston until the liquid level 6 of the molten metal reaches the uppermost edge of the casting chamber, i. H. the "remaining volume" of the casting chamber is completely filled with molten metal. Only then does the actual mold filling phase for filling the casting mold begin. When this point in time is reached is determined exclusively by the amount of molten metal poured into the casting chamber. Is z. B. the casting chamber is only 50% full, the casting piston must cover about 50% of its advance stroke to completely fill the casting chamber. If the casting chamber is filled by more than 50%, the advance stroke is already reached after less than 50% of the total stroke.

Die Menge der in die Gießkammer eingefüllten Metallschmelze bestimmt auch die einzustellende Gießkolbengeschwindigkeit, um ein gleichförmiges Ansteigen der Metallschmelze möglichst ohne Lufteinschlüsse zu erzielen. Der genaue Füllstand und die Bestimmung der genauen Menge bestimmen demnach die genauen Zeitpunkte der Beendigung der Vorfüllphase und den Beginn der Formfüllphase.The amount of molten metal poured into the casting chamber also determines the casting piston speed to be set in order to achieve a uniform rise in the molten metal without air pockets. The exact fill level and the determination of the exact amount accordingly determine the exact times of the end of the prefilling phase and the beginning of the mold filling phase.

Um die genaue Dosiermenge und damit den genauen Füllstand der Schmelzmenge in der Gießkammer zu erfassen, ist gemäß der Erfindung eine ortsfeste Meßeinrichtung 8 vorgesehen, die über einen Steg 9 fest mit der Aufspannplatte 1 verbunden ist. Mittels dieser Meßeinrichtung kann durch Ultraschall oder Laser räumlich über der Gießkammer 2 der Füllstand 6 der Schmelze in der Gießkammer ermittelt werden. Die Meßeinrichtung 8 mit dem Meßauge 10 ist dabei in einer Entfernung a von der Füllöffnung 7 der Gießkammer 2 entfernt installiert, womit sie gegen Wärme oder sonstige Beschädigung geschützt ist. Weiterhin ist hierdurch ein ungehinderter Zugang zur Füllöffnung 7 beispielsweise durch einen nicht näher dargestellten Gießlöffel möglich. Schließlich ist eine Ausblendung von Störgrößen wie Abschirmungen usw. im Bereich der Gießkammer möglich.In order to detect the exact dosing quantity and thus the exact filling level of the melting quantity in the casting chamber, a stationary measuring device 8 is provided according to the invention, which is firmly connected to the platen 1 via a web 9. Using this measuring device, the fill level 6 of the melt in the casting chamber can be determined spatially above the casting chamber 2 by means of ultrasound or laser. The measuring device 8 with the measuring eye 10 is installed at a distance a from the filling opening 7 of the casting chamber 2, with which it is protected against heat or other damage. Furthermore, this enables unhindered access to the filling opening 7, for example by means of a spoon (not shown). Finally, it is possible to suppress disturbance variables such as shields, etc. in the area of the casting chamber.

Die Messung des Füllstandes oder auch des Füllgrades 6 der Schmelze 5 in der Gießkammer 2 durch die Meßeinrichtung 8 mit eingebautem Sensor erfolgt kontinuierlich oder diskontinuierlich durch einen Ultraschall- oder Laserstrahl 11 als Meßstrahl 11, der an der Schmelzenoberfläche 6 reflektiert und als Reflektionsstrahl wieder empfangen wird. Dabei ist die Laufzeit des Meßstrahls ein Maß für die Füllstandshöhe h in der Gießkammer 2. In einem schematisch dargestellten Rechner 12 wird die Laufzeit des Meßstrahls bzw. Reflektionsstrahls in ein Wegsignal transformiert, welches die Füllstandshöhe angibt. Der Rechner 12 regelt über die Leitung 13 die Gießkolbenbewegung.The measurement of the level or the degree of filling 6 of the melt 5 in the casting chamber 2 by the measuring device 8 with a built-in sensor is carried out continuously or discontinuously by an ultrasound or laser beam 11 as a measuring beam 11, which reflects on the melt surface 6 and is received again as a reflection beam . The transit time of the measuring beam is a measure of the level h in the casting chamber 2. In a schematically illustrated computer 12, the transit time of the measuring beam or reflection beam is transformed into a path signal which indicates the level. The computer 12 controls the movement of the casting piston via line 13.

Mittels der so ermittelten Füllstandshöhe h bzw. des Schmelzestands 6 in der Gießkammer 2 können eine Reihe von Regelungen beim Gießvorgang vorgenommen werden. Zum einen kann der Einfüllvorgang der Metallschmelze unmittelbar durch ein kontinuierliches Messen überwacht werden, wobei die gewünschte Einfüllmenge nach Erreichen des gewünschten Füllstandes begrenzt werden kann. Die beim Einfüllen der Schmelze sich bildende Wellenbewegung innerhalb der Gießkammer kann durch eine Mittlung von Wellenberg und Wellental kompensiert werden. Hierdurch können auch stark schwankende Schmelzstände 6 rechnerisch gemittelt und damit der tatsächliche Füllstand ermittelt werden. Nur eine völlig exakte Bestimmung der Füllmenge gewährleistet die Richtigkeit der nachfolgend einzustellenden Gießparameter.Using the level h or melt level 6 in the casting chamber 2 determined in this way, a number of regulations can be carried out during the casting process. On the one hand, the filling process of the molten metal can be monitored directly by continuous measurement, the desired filling quantity can be limited after reaching the desired level. The wave movement within the casting chamber when the melt is poured in can be compensated for by averaging the wave crest and wave trough. As a result, strongly fluctuating melting levels 6 can also be averaged mathematically and the actual filling level can thus be determined. Only a completely exact determination of the filling quantity guarantees the correctness of the casting parameters to be set subsequently.

Die Messung des Füllstandes der Schmelze in der Gießkammer kann auch nach erfolgter Befüllung der Gießkammer erfolgen. In diesem Fall ist die Menge in der Gießkammer durch den erreichten Füllstand 6 vorgegeben, so daß sich die Gießparameter hiernach richten müssen. Insbesondere sind dies der Bewegungsablauf des Gießkolbens 4 und der Vorlaufhub des Gießkolbens 4 in die Gießkammer bis zu dem Punkt, bis die Schmelze die gesamte Gießkammer vollständig ausfüllt, d. h. bis zum oberen Rand der Gießkammer reicht. Erst ab diesem genauen Zeitpunkt beginnt die nachfolgende Formfüllphase. Die Auslösung der Formfüllphase ist deshalb mengenabhängig von der Schmelze und damit auch abhängig von der genauen Position des Gießkolbens 4 in der Gießkammer. Auch die Vorlaufphase, d. h. die Phase, in welcher der Gießkolben 4 die eingefüllte Metallschmelze in der Gießkammer bis zur vollständigen Füllung der Gießkammer 2 zusammendrückt, wird in ihrem Verlauf und ihrer Geschwindigkeit maßgeblich von dem Füllstand beeinflußt. Schließlich wird auch die Auslösung der dritten Phase, d. h. die Nachdruckphase entscheidend von der vorhandenen Menge an Schmelze geprägt, so daß der genaue Zeitpunkt auch abhängig von der Füllmenge ist.The level of the melt in the casting chamber can also be measured after the casting chamber has been filled. In this case, the amount in the casting chamber is predetermined by the level 6 reached, so that the casting parameters must be based on this. In particular, these are the movement sequence of the casting piston 4 and the advance stroke of the casting piston 4 into the casting chamber to the point until the melt completely fills the entire casting chamber, ie extends to the upper edge of the casting chamber. The subsequent mold filling phase only begins at this precise point in time. The triggering of the mold filling phase is therefore dependent on the quantity of the melt and thus also on the exact position of the casting piston 4 in the casting chamber. The run-up phase, ie the phase in which the casting piston 4 compresses the poured metal melt in the casting chamber until the casting chamber 2 is completely filled, is significantly influenced in its course and its speed by the fill level. Finally, the triggering of the third phase, ie the holding pressure phase, is decisively influenced by the amount of melt present, so that the exact point in time also depends on the filling amount.

Eine Einrichtung zur kontinuierlichen berührungslosen Füllstandmessung in Behältern mit Flüssigkeiten ist grundsätzlich bekannt. Bei einer solchen Meßeinrichtung strahlt ein Sensor Ultraschall-Impulse mit einer Frequenz von ca. 46 kHz ab. Die Schallwellen werden von der Flüssigkeitsoberfläche reflektiert und vom Sensor wieder aufgenommen. Die Laufzeit des Schalls, die zwischen Aussenden und Empfangen des Schallimpulses verstreicht, wird elektronisch ausgewertet und als füllhöhenproportionales Signal an die angeschlossenen Geräte weitergegeben. Der Abstand a der Meßsonde 10 bis zum maximalen Füllstand wird in der Größenordnung a ≈ 45 bis 70 cm angegeben. Es sind jedoch auch andere Abstände einstellbar.A device for continuous non-contact level measurement in containers with liquids is known in principle. In such a measuring device, a sensor emits ultrasonic pulses at a frequency of approximately 46 kHz. The sound waves are reflected by the surface of the liquid and picked up again by the sensor. The transit time of the sound, which elapses between the transmission and reception of the sound pulse, is evaluated electronically and passed on to the connected devices as a signal proportional to the fill level. The distance a between the measuring probe 10 and the maximum fill level is given in the order of magnitude a ≈ 45 to 70 cm. However, other distances can also be set.

Die Erfindung ist nicht auf das zuletzt beschriebene Ausführungsbeispiel des Verfahrens beschränkt. Sie umfaßt auch vielmehr alle fachmännischen Weiterbildungen und Ausgestaltungen im Rahmen der AnsprücheThe invention is not restricted to the exemplary embodiment of the method described last. Rather, it also includes all professional developments and refinements within the scope of the claims

Claims (9)

  1. A method of controlling casting parameters in the advance and/or mould filling and/or secondary pressure phase during the casting process in a cold chamber pressure casting machine, the casting phases being controllable as a function of the travel(s) of a casting chamber piston adapted for movement lengthwise in a casting chamber, characterised in that a precise dispensing and/or determination of the quantity of molten metal filling (5) within the casting chamber (2) is ascertained by a stationary optical or acoustic measuring means (8), the measuring beam penetrating a filling aperture (7) of the casting chamber (2) and being reflected by the surface (6) of the molten mass, the running time of the measuring beam (11) and of the reflected beam serving as a measurement to indicate the height (h) of filling and thus the filled quantity of molten mass (5) and in that control means (12) are provided which regulate the movement of the casting piston and thus the commencement of individual phases as a function of the filling level (6) or the associated quantity of molten metal (5) filled into the mould.
  2. A method according to claim 1, characterised in that measurement of the filling level (6) takes place during or in conjunction with the supply of molten mass whereby there may possibly be a secondary dispensing of molten mass (5) during or in conjunction with measurement of the filling level and whereby the filling level measurements act directly upon the dimension required for secondary dispensing.
  3. A method according to claim 1 or 2, characterised in that the casting piston position (4) within the casting chamber (2) at the commencement of the mould filling phase is so positioned that the residual volume of the casting chamber is filled to a predetermined degree with molten metal (5).
  4. A method according to claim 1 or 2, characterised in that an undulating motion on the surface (6) of the molten mass during the process of filling the mould with the molten metal (5) can be recognised by averaging the measured filling level values so that it becomes possible to compensate for deviations.
  5. A method according to one or more of the preceding claims, characterised in that measurement of the filling level (6) in the casting chamber (2) is supplemented and monitored by prior measurement of the filling level of a dispensing ladle.
  6. A method according to claim 5, characterised in that the dispensing ladle emptying movement occurs as a function of the measured filling level of the dispensing ladle.
  7. A method according to one or more of the preceding claims 1 to 4, characterised in that the measured filling quantity of molten metal (5) in the casting chamber (2) is used for regulating the casting parameters in the advance phase and in particular for triggering quantity-dependent positions of the casting piston (4) in the casting chamber (2) during the advance phase.
  8. A method according to one or more of the preceding claims, characterised in that the measured filling quantity of molten metal (5) in the casting chamber (2) is used for controlling the casting parameters in the mould filling phase and in particular for triggering quantity-dependent positions of the casting piston (4) in the mould filling phase.
  9. A method according to one or more of the preceding claims, characterised in that the measured filling level of molten metal (5) in the casting chamber (2) is used for regulating the casting parameters in the secondary pressure phase and in particular for triggering the secondary pressure phase during the casting process.
EP92907302A 1991-04-19 1992-04-01 Method of controlling the casting parameters in a die-casting machine Expired - Lifetime EP0581786B1 (en)

Applications Claiming Priority (3)

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DE4112753 1991-04-19
DE4112753A DE4112753A1 (en) 1991-04-19 1991-04-19 METHOD FOR CONTROLLING CASTING PARAMETERS IN A DIE CASTING MACHINE
PCT/DE1992/000266 WO1992018274A1 (en) 1991-04-19 1992-04-01 Method of controlling the casting parameters in a die-casting machine

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EP0581786A1 EP0581786A1 (en) 1994-02-09
EP0581786B1 true EP0581786B1 (en) 1994-12-28

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WO (1) WO1992018274A1 (en)

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DE59201105D1 (en) 1995-02-09
US5375646A (en) 1994-12-27
EP0581786A1 (en) 1994-02-09

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