EP2946852A1 - Vacuum pressure casting system, and method for operating a vacuum pressure casting system - Google Patents

Abstract

The invention relates to a vacuum pressure casting plant and to a method for operating a vacuum pressure casting plant.

Description

The invention relates to a vacuum pressure casting apparatus according to the preamble of claim 1 and to a method for operating such a vacuum pressure casting plant.

Vacuum die casting is known for the production of castings from metals and metal alloys, in particular from alloys of the metals Al, Mg, Zn and Cu. Corresponding plants for vacuum die casting are for example in the DE 4312647 A1 , of the DE 102004057324 A1 or the DE 102006101560 A1 described.

Vacuum die casting is used in particular where high demands are placed on tightness, elongation at break, strength and weldability of the castings. Vacuum die casting results in a higher quality of the castings as less air and gas is trapped in the material. This applies in particular to castings made of aluminum or an aluminum alloy, which are still heat-treated or welded in a later stage of the process.

In addition to the use of liquid metals or Metaillegierungen there are various special processes in vacuum die casting, as described for example in "Rolf Roller (Hrsg.): Expertise in foundry-related professions, Haan-Gruiten, 2007, pages 186-187". The present invention also encompasses such special processes, as far as the corresponding vacuum die casting plants have a casting chamber with a filling opening, a casting piston movable in the casting chamber and a piston rod, the latter connecting the casting piston to a casting drive and an annular gap between the outer jacket of the casting piston and the inner wall of the casting chamber is formed, which usually forms a leak - as described below - forms.

In vacuum die casting, as is known, a negative pressure or vacuum is generated in the mold cavity of the casting mold of the vacuum pressure casting system after the casting chamber has been filled with molten casting and the casting piston has passed the filling opening of the casting chamber.

In order to minimize the vacuum generated in the mold cavity or in the casting chamber connected to the mold cavity during vacuum die casting, it is necessary to seal all possible leaks or defects within the complete vacuum system as far as possible.

An extremely significant leak in this case is the annular gap between the inner wall of the casting chamber and the outer shell of the casting piston. At this leak, from the back of the casting piston forth penetrating gases foam the casting melt in the standing under vacuum casting chamber and produce in the casting a gas porosity, which minimize or exclude a heat treatment and weldability.

The DE 43 12 647 A1 offers a solution for closing this leak, after which a technically very complicated evacuatable sliding sleeve is pushed over the Gießkammer- or Gießkolbensystem to produce a vacuum behind the piston. The disadvantage here is in particular the very high maintenance of such Vakuumdruckgussanlagen.

The invention has for its object to avoid the disadvantages of the prior art and to improve the process for the production of vacuum die castings, so that the quality of the castings increases. The invention is also based on the object of improving the tightness, elongation at break, strength, heat-treatability and / or weldability of the castings produced by vacuum-pressure casting. A further object of the invention is to accelerate the cycle time in vacuum die casting and thus to increase the production output, Furthermore, the invention has for its object to improve the process for the production of vacuum die cast parts or a vacuum die casting system such that a higher vacuum in the mold cavity is adjustable.

According to the invention, this object is achieved in a vacuum pressure casting plant having a casting chamber with filling opening, a casting piston movable in the casting chamber and a piston rod which connects the Gisßkolben with a casting drive, wherein between the outer shell of the casting piston and the inner wall of the casting chamber, an annular gap is formed achieved, that the casting piston has at least one evacuable depression or cavity in fluid communication with the annular gap, and means are provided, via which the depression or cavity, preferably a groove, can be evacuated.

The term piston rod is inventively broad. It comprises not only a piston rod in the narrower sense, which is preferably advantageous for the majority of applications, but also other actuating means which move the casting piston linearly within the casting chamber. For certain applications, it may be advantageous if the piston rod is a connecting rod. For certain applications, it may in turn be useful if the casting piston driving rod is part of an eccentric.

It has been found that the critical parameters for the flow rate of the gases within the leak between the inner wall of the casting chamber and the outer jacket of the casting piston are the thickness of the gap between the casting piston and the casting chamber and the pressure difference across the gap.

Since it is not possible to work gap-free due to large heat differences in Gießkammerbereich, is achieved by the inventively provided recess or cavity that - when this is evacuated - less, or preferably no gases or air through the gap in the, the casting melt containing casting chamber flow, when in the mold cavity or in the flow associated with this casting chamber a negative pressure is generated.

It is virtually created a preferably substantially pressure difference-free area, so that compared to the prior art less, preferably only minimal to flow no gas or air through the gap in the casting mold filled with casting.

According to the invention, the negative pressure in the depression or cavity can even be greater than in the casting chamber filled with casting melt, so that the flow direction virtually inverted with respect to the prior art and gases and air flow from the casting chamber filled with casting melt into the depression or cavity , In the latter case, of course, then again a desired pressure difference across the annular gap is present.

As a result, an effective sealing of the annular gap between the outer shell of the casting piston and the inner wall of the casting chamber during vacuum die casting is achieved, such that no gases or air flow through the annular gap into the casting chamber filled with casting melt. In addition, an undesirable, so-called advancing the melt from the casting chamber is prevented in the mold cavity.

The castings produced with the vacuum die casting system according to the invention are characterized by improved tightness, elongation at break, strength, heat treatability and weldability.

Compared to the prior art, the invention is characterized in particular by the fact that the functionality of the vacuum pressure casting plant is easy to check and the vacuum die casting system for the sealing of the annular gap between casting piston and casting additional moving components needed which would be very susceptible to wear and maintenance.

Advantageously, all components of the vacuum pressure casting system according to the invention for maintenance work on the vacuum pressure casting system are very easily accessible and easily replaceable.

Overall, the development according to the invention is also inexpensive to produce for already in use vacuum die casting.

The control effort for evacuation of the depression or excavation is minimal and preferably takes place via a travel and / or time control.

The further development of known vacuum die-casting systems according to the invention advantageously does not lead to an extension of the cycle time. Rather, a shortening or acceleration of the cycle time, ie the period between the completion of two castings, can be achieved. This is in addition to the minimization to eliminate the unwanted leakage through the annular gap due to a little complex process control of the vacuum die casting system according to the invention, which tends to little plant failures and maintenance.

In addition, the invention development can be implemented without alterations to the mold itself and can be applied to various sized vacuum die casting.

Another advantage of the invention is that a higher vacuum can be achieved in the mold cavity, thereby further improving the quality of the castings.

For certain applications, it may be advantageous if the recess or cavity is formed in the casting piston itself. This can be done advantageously by prototyping such a casting piston or preferably later by a machining the casting piston, in particular by milling or grinding.

For other Anwendungsüngsfälle it may be advantageous if the recess or cavity is formed directly or indirectly behind the casting piston by arranging at least one workpiece behind the casting piston, wherein the arrangement of the recess or cavity behind the casting piston is such that the depression or cavity before their evacuation in the non-filled with molten casting region of the casting chamber by moving in the casting piston can be brought into the casting chamber.

For certain purposes, the recess or cavity may be formed in the workpiece itself. For other applications, it may be advantageous if the workpiece is spaced from the casting piston such that the recess or cavity is formed between the casting piston or at least one further workpiece arranged behind the casting piston and the first workpiece. For other purposes, it may also be advantageous if the recess or cavity in the workpiece itself is formed in combination with the aforementioned spaced arrangement.

In particular, for retrofitting existing die casting systems, it may be advantageous if the workpiece is designed like a ring and is preferably pushed onto the piston rod and fixable. In particular, by a conical design of the ring opening and / or the piston rod, such a workpiece can be fixed in a simple manner by clamping on the piston rod. Of course, the workpiece by other, although less preferred, but still advantageous for certain applications fastening types, in particular by screwing, press-fitting or welding, are arranged behind the casting piston.

For certain applications, it may be expedient if the casting piston is designed in several parts. Preferably, however, the casting piston is formed in one piece or in one piece.

In addition, it may be advantageous if the casting piston is solid.

In order to prevent undesirable substances, for example flakes or lubricants, from passing through the annular gap into the at least one evacuable depression or cavity during vacuum die-casting, it may be expedient if at least one collecting recess is provided, which is in flow connection with the annular gap and before at least one an evacuable depression or cavity is arranged. The at least one collecting recess then serves as a sort of dirt trap and, in particular, also prevents the undesired substances from entering the vacuum system or clogging the vacuum suction lines emanating from the at least one evacuable depression or cavity.

It may be advantageous if the collecting recess and / or evacuatable recess is formed as a recess surrounding the outer jacket of the casting piston, the piston rod and / or the workpiece, preferably in the form of an annular groove.

A circumferential evacuable depression is advantageously arranged completely within the flow path of the gases or the air, so that little to preferably no gases or air pass through the gap between the casting chamber and the casting piston into the casting chamber. A known in the prior art undesirable pressure difference, which arises during evacuation of the mold cavity or the casting chamber and leads to the influx of gases or air through the annular gap in the casting chamber is significantly reduced to preferably eliminated. Even more preferably, the undesired pressure difference is even reversed by the negative pressure within the recess or cavity is selected to be greater than in the casting chamber filled with casting melt or as in the flow with the casting chamber connected mold cavity of the mold. Thus, a desired pressure difference arises which causes a reversal of the flow direction.

A circumferential collecting well may be particularly useful to provide as comprehensive a limit as possible on undesirable matter and to substantially prevent the penetration of such matter into the well or cavity.

For certain applications, it may also be advantageous if the collecting recess and / or the evacuable recess or cavity is provided only in the upper outer shell region of the casting piston, the piston rod and / or the workpiece. It has been shown that, depending on the vacuum die casting system used or the dimension and weight of the casting piston movable in the casting chamber, the annular gap between the outer shell of the casting piston and the inner wall of the casting chamber is not uniform, but is larger at the top than at the bottom.

Furthermore, it may be expedient if a plurality of recesses or cavities spaced from one another in the circumferential direction of the casting piston, the piston rod and / or the workpiece are provided.

Thus, it may be advantageous if these recesses are arranged distributed over the circumference of a workpiece designed as a ring. These recesses may be bores through the inside of the ring. The workpiece can be arranged immediately behind the casting piston, with only a vacuum on the inside of the ring needs to be applied to evacuate these wells. A circumferential recess can be created advantageous if said ring has a smaller outer diameter than the casting piston, then for producing the circumferential recess behind the ring another workpiece, preferably also a ring, is arranged, which has the same outer diameter as the casting plunger. In this case, the single form Wells or bore then a kind of nozzle field, can be uniformly evacuated through the single circumferential recess.

In addition, it may be expedient if a plurality of collecting recesses spaced apart from one another in the circumferential direction of the casting piston, the piston rod and / or the workpiece are provided.

It may be expedient if the evacuable depression or cavity is dimensioned and evacuable such that less or preferably no gases or air flow through the annular gap into the casting chamber during evacuation of the casting cavity or the casting chamber, and particularly preferably the flow direction in the annular gap is reversed and the gases or air flow in the direction of evacuable depression or cavity. A prevailing in the prior art in evacuating the mold cavity or the casting chamber pressure difference, which leads to the influx of gases or air through the gap in the casting chamber, i. virtually a pressure difference between the filled with molten casting chamber before the casting piston and the recess or cavity is minimized by the evacuation of the recess or cavity according to the invention, preferably eliminated, particularly preferably reversed.

It may be advantageous if the evacuable depression or cavity is subjected to a vacuum in such a way that less or preferably no gases or air flow through the said gap into the casting chamber when evacuating the casting cavity or the casting chamber, and the flow direction in the flow chamber is particularly preferred Gap inverted and the gases or air flow towards evacuable depression or cavity.

It may be advantageous if the means for evacuating the depression or cavity have at least one recess, in particular a longitudinal recess, within the piston rod, which fluidly communicates with its one end the evacuable depression or cavity and are connected at the other end fluidly connected to a vacuum system.

It may be of particular advantage if the at least one evacuable well, if not being evacuated, is usable for introducing a lubricant or other functional substance into the casting chamber, the lubricant or other functional material then passing over the at least one connected to the depression vacuum suction line or another provided for this purpose line in the recess or cavity and thus in the casting chamber can be introduced.

It may be particularly advantageous if the means for evacuating the depression or cavity comprise at least one line or bore contained in the piston rod, in particular a coolant line or bore.

Conveniently, the means comprise at least one, preferably two or more suction lines, in particular suction tubes, which are each fluidically connected at one end to the evacuable depression or cavity and at the other end to a vacuum system.

It may be advantageous if the suction line, in particular the suction tube, extends along the piston rod, preferably in a groove introduced on the outside of the piston rod, and merges with its one end through the piston or workpiece area facing the piston rod into the recess or cavity and is fluidically connected to this.

It can be advantageous if the cross section of the recess or the suction recess, in particular of the suction tube, is chosen to be so large that the vacuum which can be set in the recess or cavity, despite existing leakage between recess or cavity and the area behind the depression or cavity . Excavation arranged and over the emanating from the recess or cavity and to the piston rod leading annular gap with the recess or cavity is maintained over a predetermined time, in particular over the time in which the casting chamber and the mold cavity are evacuated and a negative pressure in the mold cavity is maintained.

It may be expedient if at least one suction tube is provided within the piston rod that merges with its one end in the recess or cavity and is fluidically connected thereto.

It may be advantageous if the vacuum die casting plant is a cold chamber vacuum die casting plant.

It may be advantageous if a control is provided for the vacuum pressure casting system, which is connected to a controller for the vacuum system and via this connection a start signal is transmitted to the vacuum system for evacuation of the depression or cavity.

A development of the invention provides that the depression or cavity is arranged as close as possible to the region of the casting piston facing the casting chamber filled with melt. This ensures that the recess or cavity is evacuated early, so that the switching time or usage time of the vacuum increases and the quality of the cast products is further improved by a correspondingly improved vacuum.

1. a) Einbringen einer Gießschmelze durch die Einfüllöffnung in die Gießkammer
2. b) Bewegen des Gießkolbens, bis die Vertiefung oder Aushöhlung die Einfüllöffnung passiert hat, oder dichtes Verschließen der Einfüllöffnung und gegebenenfalls Bewegen des Gießkolbens, bis die Vertiefung oder Aushöhlung in der Gießkammer positioniert ist, und
3. c) Evakuieren der Vertiefung oder Aushöhlung, derart, dass weniger bis vorzugsweise keine Gase oder Luft durch den Spalt zwischen Gießkolben und Gießkammer in die Gießkammer einströmen, besonders bevorzugt derart, dass sich die Strömungsrichtung im Spalt umkehrt und die Gase oder Luft in Richtung evakuierbare Vertiefung oder Aushöhlung strömen.

Finally, the invention also relates to a method for operating a vacuum pressure casting system, in particular one according to one of claims 1 to 21, comprising the following method steps:

1. a) introducing a casting melt through the filling opening into the casting chamber
2. b) moving the casting plunger until the depression or cavity has passed through the filling opening, or tightly closing the filling opening and optionally Moving the plunger until the depression or cavity is positioned in the casting chamber, and
3. c) Evacuating the depression or cavity, such that less or preferably no gases or air flow through the gap between casting piston and casting chamber in the casting chamber, particularly preferably such that the flow direction in the gap reverses and the gases or air in the direction evacuated depression or hollow out.

The inventive method leads to a significant improvement in the quality of Gusstelle.

It may be advantageous if the evacuation of the recess or cavity for some applications via a route control and for other applications via a timer is started. For certain applications, a combination of travel and time control can also be advantageous.

• Fig. 1 in a) einen Schnitt durch eine erfindungsgemäß ausgebildete Kolbenstange und in b) eine Ansicht (mit Teilschnitten) von oben auf den Gießkolben samt Kolbenstange und umlaufender Vertiefung,
• Fig. 2 einen Ausschnitt der Gießkammer mit erfindungsgemäß ausgebildetem Gießkolben mit einer Teilansicht der Kolbenstange,
• Fig. 3 in a) einen Schnitt durch eine erfindungsgemäß ausgebildete Kolbenstange, wie in Fig. 1 a), und in b) eine Ansicht (mit Teilschnitten) von oben auf den Gießkolben samt Kolbenstange und umlaufender Vertiefung mit Düsenfeld und
• Fig. 4 in a) einen Schnitt durch eine erfindungsgemäß ausgebildete Kolbenstange, wie in Fig. 1 a), und in b) eine Ansicht (mit Teilschnitten) von oben auf den Gießkolben samt Kolbenstange und umlaufender Vertiefung sowie vorgeschalteter Sammelvertiefung.

Further details and advantageous embodiments of the invention will become apparent from the following description taken in conjunction with the drawings. In this show:

• Fig. 1 in a) a section through a piston rod designed according to the invention and in b) a view (with partial sections) from above onto the casting piston together with the piston rod and the circumferential depression,
• Fig. 2 a detail of the casting chamber with a casting piston designed according to the invention with a partial view of the piston rod,
• Fig. 3 in a) a section through an inventively designed piston rod, as in Fig. 1 a) , and in b) a view (with partial sections) of the top of the casting piston together with piston rod and circumferential recess with nozzle array and
• Fig. 4 in a) a section through an inventively designed piston rod, as in Fig. 1 a) , and in b) a view (with partial sections) of the top of the casting piston together with the piston rod and circumferential recess and upstream Sammelvertiefung.

Become in the Fig. 1 to 4 Like reference numerals used, they also designate the same parts or areas.

The vacuum die casting plant according to the invention has a casting mold, not shown here, which is constructed from, for example, two mold halves. The interior of the mold, so the cavity or the mold cavity is connected to the casting chamber 10, which is filled with melt for the casting process. This is filled through the filling opening 12 and pressed by means of the casting piston 14 in the mold cavity. The gas present in the mold cavity is sucked off via a venting valve, not shown here, for example a so-called washboard. During the casting process, the solidifying metal rises up to this vent valve. The casting piston 14 is moved by a casting drive not shown here via a casting piston rod 16, that is displaced in the casting chamber 10. The control is carried out by the casting plant control.

The vacuum pressure casting system also has a vacuum system, not shown here, which are connected via corresponding vacuum lines with the casting chamber 10 and / or the mold cavity and the mold cavity together with the space located before the casting piston 32 of the casting chamber 10, for example, at a predetermined time during the casting process, evacuated after a predetermined distance of the casting piston 14 or according to other criteria.

Since in this case between the inner wall of the casting chamber 10 and the outer shell of the casting piston 14, an annular gap 18 is present, through the air or gases from the rear side of the casting piston 14 into the casting chamber 10 and in the filled therein Melt be pulled, the penetrating gases foam the melt in the standing under vacuum casting chamber and produce in the produced casting a gas porosity, which minimize or exclude a heat treatment and welding ability, is now provided according to the invention that the casting piston 14 at least one with the Annular gap 18 fluidly connected, evacuatable recess 20 and means are provided, via which the depression or cavity is evacuated.

As a result, a known from the prior art, evacuating the casting chamber and / or the mold cavity of the mold adjusting pressure difference, which leads to the influx of gases or air into the casting chamber, minimized to preferably eliminated, more preferably even vice versa that the flow direction changes and gases or air from the space 32 of the casting chamber 10, which is located in front of the casting piston 14, flow through the annular gap 18 into the recess 20.

The evacuable recess 20 is here - as in the Fig. 1 to 4 shown - formed as a casting piston 14 circumferential annular groove 24 and is thus advantageously completely in the flow path of the prior art actually through the annular gap 18 into the space 32 of the casting chamber 10 flowing gases or air.

The means for evacuating the recess 20 comprise two suction tubes 22, which are each fluidically connected at one end 24 with the evacuatable annular groove 20 and at the other end with the aforementioned fluid or another vacuum system. The suction tubes 22 are in this case arranged opposite one another along the piston rod 16 in a groove 26 respectively introduced on the outside of the piston rod 16, wherein the ends 24 pass into the annular groove 20 through the piston region 28 facing the piston rod 16 and are fluidically connected thereto. The piston rod 16 itself is hollow and has a piston cooling 30.

The casting piston 14 may be integrally formed, wherein the piston portion 28 is then part of the integral casting piston 14 and the recess 20 is introduced in the form of an annular groove bispielsweise by machining milling in the casting piston 14.

Another of the numerous possibilities for producing the recess 20 is that the piston portion 28 is a separate workpiece, for example in the form of a connection ring, which is spaced from the casting piston 14, in particular clamped on the piston rod 16. This will, as in Fig. 1 can be seen, a recess 20 formed in the form of an annular groove.

In Fig. 3 another of the numerous possibilities for producing the recess 20 is shown. There, a first workpiece in the form of a ring 34 is arranged behind the casting piston 14, wherein the ring 34 has a smaller outer diameter than the casting piston 14. The ring 34 has distributed over the circumference numerous depressions in the form of holes 36 which are fluidically connected on the inside of the ring. It is advantageous here that an evacuation on the inside of the ring leads to a uniform evacuation of the circumferential recess 20. This numerous depressions in the form of holes 26 in this case form a kind of nozzle field. To the ring 24 connects another workpiece in the form of a connection ring. This connection ring then forms the abovementioned piston region 28 and corresponds in external diameter to that of the casting piston 14.

Fig. 4 finally shows the device according to Fig. 1 , However, has an additional collecting recess 38 in the form of an annular groove, which serves to trap unwanted substances, such as tinsel or lubricant, and is connected upstream of the evacuated depression.

The control for the vacuum die-casting system is advantageously connected to a control of the vacuum system for evacuating the annular groove 20, wherein a simple, on the vacuum system transmitted away or timed start signal to evacuate the annular groove 20 is sufficient.

In the method according to the invention for operating a vacuum pressure casting plant, in particular according to one of claims 1 to 10, it is advantageous that, after introduction of the casting melt through the filling opening 12 into the casting chamber 10, the casting piston 14 is first moved to the extent that the annular groove 20 Feed opening 12 has happened. Subsequently, preferably substantially simultaneously with the evacuation of the mold cavity and the casting chamber 10, the annular groove 20 is evacuated such that no gases or air flow through said gap 18 into the casting chamber 10.

LIST OF REFERENCE NUMBERS (is not part of the description)

10

casting chamber

12

fill opening

14

casting plunger

16

piston rod

18

gap

20

ring groove

22

suction tube

24

The End

26

groove

28

piston area

30

piston cooling

32

Room of the casting chamber in front of the casting piston

34

ring

36

Recess / bore

38

collection recess

Claims (17)

Vacuum pressure casting system comprising a casting chamber (10) with filling opening (12), a casting piston (14) movable in the casting chamber (10) and a piston rod (16) which connects the casting piston (14) to a casting drive, wherein between the outer jacket of the casting piston ( 14) and the inner wall of the casting chamber (10) an annular gap (18) is formed, characterized in that the casting piston (14) at least one with the annular gap (18) in fluid communication, evacuated depression or cavity and means are provided over the recess or cavity is evacuated. Vacuum pressure casting plant, in particular according to claim 1, characterized in that the depression or cavity is formed in the casting piston itself. Vacuum pressure casting plant, in particular according to claim 1 or 2, characterized in that the recess or cavity is formed directly or indirectly behind the casting piston by arranging at least one workpiece behind the casting piston, wherein the arrangement of the recess or cavity behind the casting piston is such that the recess or cavity can be brought into the casting chamber before it is evacuated into the region of the casting chamber which is not filled with molten casting by moving the casting plunger in. Vakuumdruckgussanlage, in particular according to claim 2, characterized in that the recess or cavity in the workpiece itself is formed and / or that the workpiece is spaced from the casting piston, that between casting piston or at least one further arranged behind the casting piston workpiece and the first workpiece Deepening or excavation forms. Vacuum pressure casting plant, in particular according to claim 3 or 4, characterized in that the workpiece is a ring which is preferably pushed onto the piston rod and fixable. Vacuum pressure casting plant, in particular according to one of claims 1 to 5, characterized in that at least one collecting recess is provided which communicates with the annular gap in flow communication and is arranged in front of the at least one evacuable depression or cavity. Vacuum pressure casting plant, in particular according to one of claims 1 to 6, characterized in that the collecting recess and / or the evacuable recess as a the outer shell of the casting piston, the piston rod and / or the workpiece circumferential recess, preferably in the form of an annular groove is formed. Vacuum pressure casting plant, in particular according to one of claims 1 to 7, characterized in that the recess or cavity is provided only in the upper outer shell region of the casting piston of the piston rod and / or the workpiece. Vacuum pressure casting plant, in particular according to one of claims 1 to 8, characterized in that a plurality, in the circumferential direction of the casting piston, the piston rod and / or the workpiece spaced recesses or cavities are provided. Vakuumdruckgussanlage, in particular according to one of claims 1 to 9, characterized in that the evacuable recess or cavity is dimensioned and evacuated so that when evacuating the mold cavity or the casting less or preferably no gases or air through the gap between casting piston and casting chamber the casting chamber flow in and, more preferably, the flow direction in the gap is reversed and the gases or air flow in the direction of evacuable depression or cavity. Vakuumdruckgussanlage, in particular according to one of claims 1 to 10, characterized in that the evacuable recess or cavity is so applied with a vacuum that when evacuating the mold cavity or the casting less or preferably no gases or air through the annular gap between casting piston and casting chamber flow into the casting chamber and particularly preferably the flow direction in the gap reverses and the gases or air flow in the direction of evacuable depression or hollow. Vakuumdruckgussanlage, in particular according to one of claims 1 to 11, characterized in that the means for evacuating the recess or cavity comprise at least one recess, in particular longitudinal recess, within the piston rod, which at one end fluidly with the evacuated recess or cavity and with their other end fluidly connected to a vacuum system. Vakuumdruckgussanlage, in particular according to one of claims 1 to 12, characterized in that the means for evacuating the recess or cavity comprise at least one contained in the piston rod line or bore, in particular Kuhlmittelleitung or bore. Vakuumdruckgussanlage, in particular according to one of claims 1 to 13, characterized in that the means comprise at least one, preferably two or more suction lines, in particular suction tubes, each with its one end fluidly with the evacuable recess or cavity and with its other end fluidically connected to a vacuum system. Vacuum pressure casting plant, in particular according to claim 14, characterized in that the suction line, in particular the suction tube, along the piston rod, preferably in a groove introduced on the outside of the piston rod, extends and with its one end by the piston rod facing the piston or workpiece area in the Groove or hollow passes and is fluidically connected to this. Vakuumdruckgussanlage, in particular according to one of claims 10 to 15, characterized in that the cross section of the recess or the suction line, in particular the suction tube is chosen so large that the adjustable in the recess or cavity vacuum despite existing leakage between recess or cavity and the region which is located behind the recess or cavity and is connected to the depression or cavity via the annular gap leading from the depression or cavity and leading to the piston rod is maintained for a predetermined time, in particular over the time in which the casting chamber and the mold cavity are evacuated and a vacuum in the mold cavity is maintained. Method for operating a vacuum pressure casting system, in particular according to one of claims 1 to 16, comprising the following method steps: a) introducing a casting melt through the filling opening into the casting chamber b) moving the casting plunger until the depression or cavity has passed through the filler opening, or tightly closing the filler opening and optionally moving the casting piston until the depression or cavity is positioned in the casting chamber, and c) evacuating the depression or cavity, preferably in such a way that less or preferably no gases or air flow into the casting chamber through the gap between casting piston and casting chamber, particularly preferably such that the flow direction in the gap is reversed and the gases or air can be evacuated in the direction Groove or hollow out.

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