EP2588261B1 - Method for filling the mold cavity of a pressure die casting device, valve arrangement and die casting device for carrying out the method - Google Patents

Description

The invention relates to a method for filling the mold cavity of a die casting device with liquid casting material according to the features of the preamble of claim 1.

From the EP 0 827 794 B1 a die casting device is known with a mold cavity, which is connected via a filling channel with a casting chamber and a vent channel with a gas outlet. In the casting chamber, a press-in piston is slidable back and forth between a retracted position and an advanced position. Via a filling hole liquid casting material can be filled into the casting chamber. This may be, for example, an aluminum or magnesium melt. The liquid casting material can be pressed by means of the injection piston via the filling channel into the mold cavity. Gas, which is located in the mold cavity, so in particular air, can escape from the mold cavity via the vent channel. The vent channel is for this purpose in fluid communication with the gas outlet. The latter can for example be designed as a suction device.

In the production of castings, there is a risk that air bubbles form, which reduces the quality of the finished casting. To achieve improved casting results, therefore, it has already been proposed to withdraw gases from the casting chamber during the pressing in of the casting material, in particular air. However, this has the disadvantage that wave formation, flashover or turbulence in the liquid casting material can occur during the pressing in case of a non-uniform feed movement of the press-in piston. This involves the risk of trapping air and other gases in the liquid casting material.

From the US 5,219,409 A a vacuum die casting method is known in which a mold cavity of a die casting device is filled with liquid casting material. The die casting device comprises a press-in piston, which is displaceable in a casting chamber. Liquid casting material can be filled into the casting chamber and pressed into the mold cavity by means of the injection piston. During a first press-in phase, the press-fit piston is moved at a first feed rate, and during a second press-in phase, the press-in piston is moved at a second feed rate, the second feed rate being higher than the first feed rate. During the first press-in phase, the mold cavity is sucked off, and during the second press-in phase, the mold cavity is closed airtight.

From the US 5,785,112 A a method for filling the mold cavity of a die casting apparatus is known in which the liquid casting material is acted upon during the filling process with compressed air. A corresponding procedure, namely the penetration of the casting material into the mold cavity against a prevailing gas pressure, is also in the DE 31 42 081 A1 proposed.

Object of the present invention is to develop a method of the generic type such that the risk of air and gas inclusions in the liquid casting material is reduced when pressed into the mold cavity.

This object is achieved by a method having the features of patent claim 1.

In the method according to the invention, an overpressure is generated in the casting chamber while the liquid casting material is pressed into the mold cavity. For this purpose, compressed air is passed into the casting chamber. It has been found that thereby a wave formation of the liquid casting material also suppressed in a non-uniform feed movement of the press-in piston can be like the formation of turbulence or a rollover of the liquid casting material. The overpressure acting on the casting material in the casting chamber ensures that even with a non-uniform movement of the press-in piston in the casting chamber, no strong waves of the liquid casting material form. Rather, the liquid level of the casting material remains fairly uniform, so that despite the pressurization of the casting material with compressed air, the risk of air or other gas inclusions can be considerably reduced.

The press-in piston is moved during a first press-in phase at a first feed rate and during a subsequent second press-in phase at a second feed rate, wherein the second feed rate is higher than the first feed rate. This gives the possibility of initially moving the press-in piston slowly in order to supply the liquid casting material to a filling channel adjoining the casting chamber. If the liquid casting material has reached the filling channel or also the inlet opening of the mold cavity, the press-in piston is then accelerated very strongly, so that it presses the liquid casting material into the mold cavity at a significantly higher feed rate, and during the hardening of the pressed-in casting material the injection piston can continue act on the casting material. According to the invention, the casting material in the casting chamber is subjected to compressed air only during the first press-in phase. The pressurization of the casting material with compressed air thus takes place only during the relatively slow movement of the press-in piston, this slow movement usually ends when the liquid casting material has reached the filling channel or the inlet opening of the mold cavity. If this is the case, the admission of the casting material in the casting chamber is terminated with compressed air.

According to the invention, the mold cavity is sucked off after the application of compressed air to the casting material. The risk of air bubbles can be further reduced.

The piston movable in the casting chamber is reciprocable between a retracted position and an advanced position. In the retracted position of the piston, the casting chamber can be filled via the filling hole with liquid casting material. Subsequently, the piston is moved to the advanced position, wherein it passes over the filling hole. The casting material is only then subjected to compressed air in the casting chamber when the piston has passed over the filling hole of the casting chamber. The beginning of the pressurization can thus take place in dependence on the position of the piston in the casting chamber, for example, such that the casting chamber compressed air is supplied as soon as the piston has passed over the filling hole. The compressed air can then be supplied to the casting chamber in particular via the mold cavity and the filling channel.

In an advantageous embodiment of the method according to the invention, the compressed air is supplied to the casting chamber via the mold cavity. For supplying compressed air into the casting chamber thus no additional compressed air channels in the die casting apparatus are required.

The pressure of the compressed air is preferably monitored. For this purpose, a pressure sensor can be used.

It is particularly advantageous if the pressure of the compressed air is regulated. This gives the possibility to form a virtually constant pressure within the casting chamber, which acts on the liquid casting material.

It can be provided that in the region between the casting chamber and the mold cavity, in particular in the filling channel, a metal front contact sensor is arranged, which responds to the contact with casting material, and that the casting material is applied in the casting chamber as long as compressed air until the casting material Metal front contact sensor achieved. The metal front contact sensor can be arranged, for example, at the inlet of the filling channel or at its output. When the liquid casting material reaches the metal front contact sensor, it sends a signal to a control device the die casting device. Due to this signal, the admission of the casting material in the casting chamber can then be terminated with compressed air.

It can be provided, for example, that the mold cavity during the second press-in, in which the press-in piston is moved at a relatively high feed speed, is sucked through the vent channel. The vent channel thus serves on the one hand to supply compressed air via the mold cavity and the filling channel of the casting chamber, on the other hand, the mold cavity can be sucked through the vent channel.

The mold cavity is expediently sucked off as soon as a metal front contact sensor arranged in the filling channel, in particular at its inlet, responds to contact with liquid casting material. During the first press-in phase, in which the press-in piston is moved at a relatively low feed rate, the liquid casting material in the casting chamber can be subjected to compressed air. The application of compressed air in this case lasts until the preferably arranged at the entrance of the filling channel metal front contact sensor responds to the contact with liquid casting material. Subsequently, the mold cavity can be sucked through the vent channel.

Conveniently, a signal is triggered as soon as the piston has passed over the filling hole in the casting chamber, and then the casting material is pressurized in the casting chamber with compressed air. The signal may be provided, for example, by a displacement sensor coupled to the displaceable piston. By means of the displacement sensor, the position of the piston can be detected in a structurally simple manner, and depending on the piston position, the admission of the casting material located in the casting chamber can be triggered with compressed air.

In a particularly preferred embodiment of the method according to the invention is to the output of a vent channel of the die casting connected to a valve assembly having a first and a second port, wherein the first port is connected to a compressed air supply device and the second port to a gas outlet device, and wherein in the first press-in phase, in which the press-in piston is moved at a first feed rate, the flow connection released from the outlet of the venting channel to the compressed air supply device and the flow connection from the outlet of the venting duct to the gas outlet device is interrupted, and wherein in the second press-in phase, in which the press-in piston is moved at a second feed rate which is higher than the first feed rate, the flow connection from the output of the Venting channels to the compressed air supply device interrupted and the flow connection is released from the outlet of the venting channel to the gas outlet. By means of the valve arrangement can be controlled in a simple manner, the pressurization of the liquid casting material within the casting chamber and the negative pressure of the casting material in the mold cavity. In particular, the valve arrangement can be connected to the outlet of the venting channel of a conventional die casting apparatus. Elaborate conversion work can be dispensed with at the die casting machine and yet the risk of air and gas trapping in the casting material can be reduced.

It is advantageous if the valve arrangement is controlled by means of sensors.

By way of example, the valve arrangement can have at least one electromagnetic valve which can be controlled electrically by a control device on the basis of sensor signals which are provided, for example, by a metal front contact sensor, a displacement sensor and / or a pressure sensor.

The valve assembly is conveniently located at the exit of a bleed valve of the die casting apparatus positioned in the bleed passage. A valve arrangement for carrying out the method explained above conveniently comprises three connections, wherein a compressed air supply device can be connected to a first connection and the first connection is in fluid communication with the third connection via a compressed air supply line, and wherein a gas outlet device can be connected to the second connection and the second port via a gas outlet to the third port is in flow communication, and wherein the output of a venting channel of the die-casting device can be connected to the third port. In addition, the preferred valve arrangement comprises two controllable valves, wherein the flow connection between the first and the third connection by means of a first controllable valve is selectively releasable and lockable and wherein the flow connection between the second and the third connection by means of the second controllable valve is selectively releasable and lockable ,

The valve arrangement is preferably designed as an independently manageable unit.

The valve arrangement can be connected to the outlet of the venting channel of a known die casting device and then makes it possible in a structurally simple manner to pressurize the casting material in the casting chamber with compressed air and subsequently to remove the air in the mold cavity together with other gases from the mold cavity , The supply of compressed air takes place as well as the delivery of air and gases via controllable valves. A first controllable valve controls the supply of compressed air to the casting chamber via the vent passage and the mold cavity, and the second controllable valve controls the delivery of air and gases from the mold cavity via the vent passage. The two controllable valves are alternatively opened and closed. If the first controllable valve assumes its open position, then the flow connection between the compressed air supply device and the venting channel is free, so that compressed air via the venting channel and flow the mold cavity to the casting chamber and there act on the liquid casting material. During this phase, the second controllable valve is closed. If the first controllable valve assumes its closed position, then the flow connection between the compressed air supply device and the venting channel is interrupted. In this state, the second controllable valve may assume its open position, so that a flow connection is established between the gas outlet device and the mold cavity, so that gases in the mold cavity as well as compressed air can be removed. As already mentioned, the gas outlet device can be designed, for example, in the form of a suction device or else in the form of an air outlet.

It is advantageous if the compressed air supply line and the gas outlet line open into a common connecting line. The common connection line can be connected via the third connection directly to the outlet of the venting channel of the die casting device.

In the gas outlet line, a filter is preferably arranged.

A die casting apparatus for carrying out the method mentioned above conveniently comprises a mold cavity, which is connected via a filling channel with a casting chamber and a vent channel with a gas outlet, wherein in the casting chamber a press-in piston is slidably mounted and at the outlet of the venting channel a valve arrangement of the above Art is arranged, wherein the third port of the valve assembly is connected to the outlet of the venting channel.

As already explained, the use of the valve assembly in a die casting apparatus allows pressurized air to be applied to the liquid casting material in the casting chamber to prevent curling, flashover or turbulence in the liquid casting material within the casting chamber. After the application of compressed air can during the further Pressing the liquid casting material of the mold cavity of the die casting device are connected via the valve assembly to a gas outlet. The use of a gas outlet device in the form of a suction device makes it possible here to pressurize the mold cavity with negative pressure, in particular during the second press-in phase.

The die casting device preferably comprises a venting valve arranged in the venting channel with an outlet which forms the outlet of the venting duct. At the outlet of the vent valve, the third port of the valve assembly may be connected. The vent valve may be formed, for example, as a mechanical closing valve, in particular in the form of a piston valve. Alternatively it can be provided that the vent valve comprises a narrow gap, solidifies in the liquid casting material. In particular, it can be provided that the venting valve is designed in the manner of a washboard valve. Such safety board valves are known per se to those skilled in the art and therefore require no further explanation in the present case.

Figur 1:

eine schematische Darstellung einer Druckgießvorrichtung mit einer Ventilanordnung;

Figur 2.

eine vergrößerte Darstellung der Ventilanordnung aus Figur 1;

Figur 3.

eine schematische Darstellung einer ersten Ausführungsform eines Entlüftungsventiles der Druckgießvorrichtung aus Figur 1;

Figur 4:

eine schematische Darstellung einer zweiten Ausführungsform eines Entlüftungsventiles der Druckgießvorrichtung aus Figur 1;

Figuren 5, 6 und 7:

schematische Darstellungen von Gießkammern üblicher Druckgießvorrichtungen, wobei das flüssige Gießmaterial in der Gießkammer Wellen, einen Überschlag oder Turbulenzen ausbildet.

The following description of a preferred embodiment of the invention serves in conjunction with the drawings for further explanation. Show it:

FIG. 1:

a schematic representation of a die casting device with a valve assembly;

FIG. 2.

an enlarged view of the valve assembly FIG. 1 ;

FIG. 3.

a schematic representation of a first embodiment of a vent valve of the die casting from FIG. 1 ;

FIG. 4:

a schematic representation of a second embodiment of a vent valve of the die casting from FIG. 1 ;

FIGS. 5, 6 and 7:

schematic representations of casting chambers of conventional die casting, wherein the liquid casting material in the casting chamber waves, a rollover or turbulence is formed.

In the drawing, a pressure casting 10 is shown schematically with a mold cavity 12 which is connected via a filling channel 14 with a casting chamber 16, in which a press-in piston 18 is slidably mounted. Via a filling hole 20, liquid casting material, for example an aluminum or magnesium melt, can be introduced into the casting chamber 16. For this purpose, the press-in piston 18 assumes its retracted position in a known manner so that the casting material can enter the casting chamber 16 without being obstructed by the injection piston 18. If the press-in piston 18 is displaced from its retracted position to its advanced position, then the liquid casting material 22 located in the casting chamber 16 is pressed into the mold cavity 12 via the filling channel 14. Casting chambers of the above-explained type are often referred to as Füllgüchse.

In the mold cavity 12 located gases and air can be delivered to a known per se and therefore in the drawing to achieve a better overview not shown gas outlet, for example, to a suction device or an air vent. The mold cavity 12 is for this purpose via a vent channel 24 with an in FIG. 2 enlarged illustrated valve assembly 26 in fluid communication. The latter comprises a first controllable valve, which is referred to below as the air inlet valve 28, and a second controllable valve, which is referred to below as the gas outlet valve 30. The two valves 28, 30 are in the form of solenoid valves and can be controlled electrically by a control device of the die casting device 10. Such controllers are known in the art and therefore not shown in the drawing to achieve a better overview.

The Einpresskolbens 18 is driven by means of a known per se and therefore only roughly schematically illustrated in the drawing Einpresssystems 19. With the help of Einpresssystems 19, the press-in piston 18 can be moved back and forth in the casting chamber 16 and acted upon by high mechanical pressure.

The input of the air inlet valve 28 forms a first port 32 of the valve assembly 26. To the first port 32, a first line 33 is connected, via which the valve assembly 26 connected to a known per se and therefore to achieve a better overview in the drawing compressed air supply device is. The compressed air supply device may for example have a compressor or a compressed air reservoir.

The outlet of the gas outlet valve 30 forms a second port 34 of the valve assembly 26. Connected to the second connection 34 is a second line 35, via which the valve arrangement 26 is in flow communication with a gas outlet device. The gas outlet device can be designed, for example, in the form of a suction device or else in the form of an air outlet. Such gas outlet devices are known per se to those skilled in the art.

The valve arrangement 26 has a third connection 36, which is connected directly to an outlet 38 of the ventilation channel 24. The third port 36 is disposed on a valve block 40 of the valve assembly 26. The valve block 40 forms the third port 36 adjacent to a connecting line 42, to which a compressed air supply line 44 connects in the direction of the air inlet valve 28, via which the connecting line 42 is in flow communication with the air inlet valve 28.

In the direction of the gas outlet valve 30, a gas outlet line 46 connects to the connecting line 42, via which the connecting line 42 with the gas outlet valve 30 is in flow communication. In the gas outlet 46, a filter 48 is arranged.

In order to avoid that liquid casting material can escape from the mold cavity via the venting channel 24, a vent valve is arranged in the venting channel 24. A first embodiment of a vent valve is in FIG. 3 shown schematically and occupied by the reference numeral 50. It has a flow labyrinth 51, via which the mold cavity 12 is in flow communication with the valve arrangement 26. If liquid casting material enters the flow labyrinth, it solidifies within the flow labyrinth and therefore can not escape from the venting channel 24. If the venting valve 50 is positioned in the venting channel 24, the outlet of the venting valve 50 forms the outlet 38 of the venting channel 24.

In FIG. 4 an alternative embodiment of a vent valve is shown schematically, which is generally designated by the reference numeral 54. It is designed in the manner of a washboard valve, which is known per se to the person skilled in the art. By means of such washboard valves can also be prevented that liquid casting material emerges from the vent passage 24. If the venting valve 54 is positioned in the venting channel 24, then the outlet of the venting valve 54 forms the outlet 38 of the venting channel 24.

The valve arrangement 26 can preferably be mounted directly on the venting valve 50 or on the venting valve 54. Conveniently, the valve block 40 and in particular the geometry of the connecting line 42 can be adapted to the outlet of the venting valve 50 or 54 for this purpose.

To produce a casting, the mold cavity 12 is closed and then liquid casting material is poured into the casting chamber 16 via the filling hole 20, wherein the press-in piston 18 assumes its retracted position. The injection piston 18 is then during a first Einpressphase at a relatively low speed in the direction of filling channel 14 postponed. If the press-fit piston 18 has run over the filling hole, a signal is triggered and then the air inlet valve 28 is opened so that compressed air flows via the compressed air supply line 44, the venting channel 24, the mold cavity 12 and the filling channel 14 into the casting chamber 16 and into the casting chamber 16 located liquid casting material can pressurize. At the entrance of the filling channel 14, a metal front contact sensor 56 is arranged, which is connected via a signal line 57 with the control device of the die casting device 10, not shown in the drawing. If the liquid casting material encounters the metal front contact sensor 56 with increasing feed movement of the press-fit piston 18, this provides a signal which results in the air inlet valve 28 being closed. At the same time, the gas outlet valve 30 is opened, so that the mold cavity 12 is in fluid communication with the gas outlet device connected to the second connection 34 of the valve arrangement 26 via the venting channel 24 and the gas outlet line 46. It can be provided that the gas outlet device has a suction device, so that the mold cavity 12 can be subjected to negative pressure during the further pressing of the liquid casting material.

As already mentioned, the press-fit piston 18 has a relatively low feed rate during the first press-in phase. The first press-in phase ends with the liquid casting material reaching the metal front contact sensor 56. Subsequently, the speed of the press-fit piston 18 is greatly increased and during a second press-in phase, the liquid casting material is pressed by the injection piston 18 via the filling channel 14 into the mold cavity 12. During the second press-in phase, the mold cavity, as explained above, can be sucked off.

The supply of compressed air via the air inlet valve 28 and the compressed air supply line 44 can be monitored by means of a pressure sensor 59 which is in fluid communication with the compressed air supply line 44 via a branch line 60.

The pressurization of the liquid casting material 22 in the Geißkammer 16 with compressed air ensures that form in the casting chamber 16 no large waves of liquid casting material 22 and the liquid casting material 22 also does not overturn or turbulence forms. Such corrugation, flashover or turbulence in the liquid casting material 22 could result in air and gases being trapped in the liquid casting material 22. The FIGS. 5, 6 and 7 illustrate such conditions of a liquid casting material 122, which may form in the casting chambers 116 of conventional die casting devices, in particular, when the known press-in piston 118 performs a non-uniform feed movement. The formation of such conditions is avoided by the inventive loading of the liquid casting material with compressed air. The risk that air and other gases are trapped in the casting chamber 16 in the liquid casting material 22 can thereby be kept very low.

Claims (10)

1. Method for filling the die cavity (12) of a pressure die casting apparatus (10) with liquid casting material (22), the pressure die casting apparatus (10) comprising an injection plunger (18) which is displaceable in a casting chamber (16), wherein the casting material (22) is filled into the casting chamber (16) through a filling hole (20) and pressed into the die cavity (12) by means of the injection plunger (18), the injection plunger (18) being moved during a first injection phase at a first feed rate and during a subsequent second injection phase at a second feed rate, the second feed rate being higher than the first feed rate, characterized in that the casting material (22) is only subjected to compressed air in the casting chamber (16) during the first injection phase, and after the casting material (16) has been subjected to compressed air the die cavity (12) is evacuated, the casting material (22) only being subjected to compressed air in the casting chamber (16) when the injection plunger (18) has moved over the filling hole (20) of the casting chamber (16).
2. Method in accordance with claim 1, characterized in that the compressed air is supplied to the casting chamber (16) via the die cavity (12).
3. Method in accordance with claim 1 or 2, characterized in that the pressure of the compressed air is monitored.
4. Method in accordance with any one of the preceding claims, characterized in that the pressure of the compressed air is controlled.
5. Method in accordance with any one of the preceding claims, characterized in that a metal front contact sensor (56) which responds to contact with casting material (22) is arranged in the region between the casting chamber (16) and the die cavity (12), and in that the casting material (22) is subjected to compressed air in the casting chamber (16) until the casting material (22) reaches the metal front contact sensor.
6. Method in accordance with any one of the preceding claims, characterized in that the die cavity (12) is evacuated during the second injection phase via a vent channel (24) of the pressure die casting apparatus (10).
7. Method in accordance with any one of the preceding claims, characterized in that a signal is triggered once the injection plunger (18) has moved over the filling hole (20) in the casting chamber (16), and in that the casting material (22) is thereupon subjected to compressed air in the casting chamber (16).
8. Method in accordance with any one of the preceding claims, characterized in that a valve assembly (26) comprising a first and a second connection (32, 34) is connected to the outlet (38) of a vent channel (24) of the pressure die casting apparatus (10), wherein the first connection (32) is connected to a compressed air supply device and the second connection (34) to a gas outlet device, and wherein in the first injection phase in which the injection plunger (18) is moved at a first feed rate, the flow connection from the outlet of the vent channel to the compressed air supply device is enabled and the flow connection from the outlet of the vent channel to the gas outlet device is interrupted, and wherein in the second injection phase in which the injection plunger (18) is moved at a second feed rate, which is higher than the first feed rate, the flow connection from the outlet of the vent channel to the compressed air supply device is interrupted and the flow connection from the outlet of the vent channel to the gas outlet device is enabled.
9. Method in accordance with claim 8, characterized in that the valve assembly (26) is controlled by means of sensors (56, 59).
10. Method in accordance with claim 8 or 9, characterized in that the valve assembly (26) is arranged at the outlet of a vent valve (50, 54) of the pressure die casting apparatus (10), which is positioned in the vent channel (24).

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