Plunger system and casting method for a die casting machine

Abstract

A casting plunger system for a die casting machine includes a stationary system part and a system part which moves relative to the stationary system part in a respective casting cycle for the introduction of melt material into a casting mould. The moved system part has a plunger, a plunger rod and a rod drive unit, and is configured to decelerate at the end of a mould filling phase of the casting cycle under the effect of pressure on the melt material. A casting method for a die casting machine is provided with such a plunger system. The moved system part has a mass which can be adjusted variably between different casting cycles, and/or the moved system part consists of a moved main system part and an additional mass unit which is arranged so as to be movable relative to the main system part and is configured to decelerate, at the end of the mould fill phase of the casting cycle, later by a predefined delay time than the main system part.

Claims

1. A casting plunger system for a die casting machine, comprising: a stationary system part; and a system part which moves relative to the stationary system part in a respective casting cycle for introduction of melt material into a casting mould, the system part comprising a casting plunger, a casting plunger rod and a rod drive unit, and being configured to decelerate at an end of a mould filling phase of the casting cycle under the effect of pressure on the melt material, wherein the system part which moves comprises a moved main system part and an additional solid mass unit which is arranged so as to be movable relative to the moved main system part and is configured to decelerate, at an end of the mould filling phase of the casting cycle, later by a predefinable delay time than the main system part.

2. The casting plunger system according to claim 1, further comprising: one or more additional solid mass bodies which are each configured for releasable attachment to the moved main system part and in the attached state form a component of the moved main system part.

3. The casting plunger system according to claim 2, wherein a plurality of additional solid mass bodies is provided, of which at least two additional solid mass bodies have a different mass.

4. The casting plunger system according to claim 2, wherein the stationary system part comprises an additional solid mass storage unit for stored provision of the additional solid mass body or bodies.

5. The casting plunger system according to claim 2, further comprising: an additional solid mass handling unit which is configured for automatic attachment and removal of the one or more additional solid mass bodies to and from the moved main system part.

6. The casting plunger system according to claim 1, wherein the relatively movable arranged additional solid mass unit comprises an additional solid mass body which is arranged on the moved main system part to be slidingly movable between a starting position and an end position, where at least one of an initial end stop and an impact end stop is provided on the moved main system part, the initial end stop defining the starting position and the impact end stop defining the end position.

7. The casting plunger system according to claim 6, wherein at least one of: the initial end stop, or the impact end stop, is adjustable on the moved main system part.

8. The casting plunger system according to claim 6, further comprising: a locking unit for releasable locking of the additional solid mass body in the starting position or in the end position or in a predefinable locking position between the starting position and the end position.

9. A casting method for a die casting machine with a casting plunger system, said casting plunger system comprising: a stationary system part; and a system part which moves relative to the stationary system part in a respective casting cycle for introduction of melt material into a casting mould, the system part comprising a casting plunger, a casting plunger rod and a rod drive unit, and being configured to decelerate at an end of a mould filling phase of the casting cycle under the effect of pressure on the melt material, wherein the system part which moves includes a moved main system part and an additional solid mass unit which is arranged so as to be movable relative to the moved main system part and is configured to decelerate, at an end of the mould fill phase of the casting cycle, later by a predefinable delay time than the moved main system part, wherein the casting method comprises: detecting at least one casting parameter of a respective casting cycle; and variably adjusting a delay time for the relatively movably arranged additional mass unit for one or more future casting cycles depending on the at least one detected casting parameter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic side view of a plunger system and associated casting chamber and casting mould of a plunger system according to the invention with an additional mass body fixed to the plunger drive piston, for a die casting machine;

(2) FIG. 2 shows the view from FIG. 1 without casting chamber and casting mould, in an embodiment variant of the plunger system according to the invention with an additional mass body fixed to the plunger coupling;

(3) FIG. 3 shows the view from FIG. 2 for an embodiment variant of the plunger system according to the invention with an additional mass body fixed to the plunger rod;

(4) FIG. 4 shows the view from FIG. 2 for an embodiment variant of the plunger system according to the invention with optional additional mass bodies which may be coupled additionally;

(5) FIG. 5 shows the view from FIG. 2 for an embodiment variant of the plunger system according to the invention with a slidingly movably arranged additional mass body;

(6) FIG. 6 shows the view in FIG. 2 for an embodiment variant of the plunger system according to the invention with a set of several plungers and/or plunger rods and/or plunger couplings and/or plunger drive pistons, each of predefined different mass;

(7) FIG. 7 shows a schematic flow diagram to illustrate steps of interest in the present case of a casting method according to the invention; and

(8) FIG. 8 shows a characteristic curve diagram to illustrate the temporal melt pressure development in a casting mould during a casting process for different performance variants of a casting process according to the invention and not according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(9) FIG. 1 shows schematically a casting plunger system for a die casting machine, wherein the plunger system contains a stationary system part 1 and a moved system part 2. The stationary system part 1 comprises for example, as shown, a casting chamber 12 and a casting plunger drive cylinder 13, the latter often known in brief as a casting cylinder. The casting chamber 12 opens as usual in a casting mould 14 which is formed by a fixed casting mould half and a movable casting mould half of the die casting machine. The moved system part 2 is movable relative to the stationary system part 1 in order to introduce melt material into the casting mould 14 in a respective casting cycle, for which it comprises a casting plunger 3, a casting plunger rod 4 and a rod drive unit 5, and is configured to decelerate at the end of a mould filling phase of the casting cycle under the effect of pressure on the melt material.

(10) The plunger 3 is arranged fluid-tightly and axially movably in the e.g. cylindrical casting chamber 12. In the example shown, the plunger rod 4 carries the plunger 3 on its front end face region, and at its rear end face region is coupled to the rod drive unit 5, in particular to a plunger coupling 9 of the rod drive unit 5. In the example shown, the plunger coupling 9 couples the plunger rod 4 to a front end face region of a plunger drive piston 10 of the rod drive unit 5 which is guided so as to be axially movable in the plunger drive cylinder 13. Optionally, the plunger drive piston 10 is coupled to a pressure multiplier unit (not shown).

(11) The moved system part 2 has a solid mass which can be variably adjusted between different casting cycles, and/or—as in the exemplary embodiment of FIG. 5—consists of a moved main system part 2a and an additional solid mass unit Z.sub.E which is arranged so as to be movable relative thereto and configured to decelerate, at the end of the mould filling phase of the casting cycle, later by a predefinable delay time than the main system part 2a.

(12) In corresponding embodiments, the plunger system comprises one or more additional solid mass bodies which are respectively configured for releasable attachment to the moved system part 2, and in the attached state form an immovably coupled component of the moved system part 2. FIG. 1 shows an embodiment variant in this respect in which such an additional mass body ZK is releasably attached in particular to the plunger drive piston 10 of the moved system part 2. FIG. 2 shows an embodiment variant in this respect in which such an additional mass body ZK is releasably attached in particular to the plunger coupling 9 of the moved system part 2. FIG. 3 shows an embodiment variant in this respect in which such an additional mass body ZK is releasably attached in particular to the plunger rod 4 of the moved system part 2. It is understood that in this case, the additional mass body ZK is arranged at an axial portion of the plunger rod 4 which lies outside or behind an immersion depth, by which a front rod portion of the plunger rod 4 is immersed to a maximum in the casting chamber 1 in order to advance the plunger 3, so that the additional mass body ZK does not hinder the advance movement of the front immersion depth portion of the plunger rod 4 into the casting chamber 12. FIG. 4 shows an embodiment variant in this respect in which several such additional mass bodies ZK.sub.1, ZK.sub.2, ZK.sub.3 may be optionally releasably attached to the moved system part 2, e.g. to the plunger coupling 9 or the plunger drive piston 10, wherein FIG. 4 shows a situation in which only a first additional mass body ZK.sub.1 is releasably attached to the moved system part 2, here in particular to the plunger coupling 9. Preferably, it is provided that the assembly and disassembly of the one or more additional mass bodies ZK or ZK.sub.1, ZK.sub.2, . . . may be accomplished without tools and/or using a fast change system or a fast clamping system.

(13) In such embodiment variants with several additional mass bodies ZK.sub.1, ZK.sub.2, which may be releasably attached to the moved system part 2, it may be advantageous if at least two of the several additional mass bodies ZK.sub.1, ZK.sub.2, . . . have different masses. For example, these additional mass bodies ZK.sub.1, ZK.sub.2, . . . may differ in mass by powers of the number 2, i.e. the next heavier additional mass body has twice the mass of the next lighter additional mass body. With such a binary stepping of the masses of the additional mass bodies ZK.sub.1, ZK.sub.2, . . . , an arbitrary integral multiple of the smallest mass of the lightest additional mass body may be set, with a comparatively low number of additional mass bodies to be provided for the total mass of all additional mass bodies ZK.sub.1, ZK.sub.2, . . . .

(14) In corresponding embodiments, as in the exemplary embodiment of FIG. 4, the stationary system part 2 comprises an additional mass storage unit 6 for stored provision of the additional mass body or bodies ZK or ZK.sub.1, ZK.sub.2, . . . . For example, FIG. 4 shows an embodiment in which the additional mass bodies ZK.sub.1, ZK.sub.2, . . . are removably suspended on an additional mass holder 6a functioning as an additional mass storage unit 6, which in turn is arranged on the stationary system part 1, e.g. the plunger drive cylinder 13, or alternatively on another stationary fixed component of the respective die casting machine. The additional mass bodies ZK.sub.1, ZK.sub.2, . . . stored in this way may then as required be extracted individually or in arbitrary combinations from the additional mass storage unit 6 and releasably attached to the moved system part 2 in order to perform the respective casting cycle with the desired total mass of the moved system part 2.

(15) In corresponding implementations, the plunger system comprises an additional mass handling unit 7 which is configured for automatic attachment of the respective additional mass body ZK or ZK.sub.1, ZK.sub.2, . . . on the moved system part 2, and for automatic removal of the respective additional mass body ZK or ZK.sub.1, ZK.sub.2, . . . from the moved system part 2. Such an additional mass handling unit 7 is shown as a block diagram in FIG. 4, in the exemplary embodiment shown there. It may for example comprise a conventional handling robot which is specifically configured to perform the necessary handling measures. Alternatively, the additional mass body ZK or ZK.sub.1, ZK.sub.2, . . . may be attached to and removed from the moved system part 2 by corresponding operating personnel.

(16) In corresponding embodiments, the plunger system—as illustrated in FIG. 6—comprises a set of a plurality of casting plungers 3.sub.1 to 3.sub.n1, shown as a block diagram in FIG. 6, with predefined different mass, which differ in their mass by predefined mass increments and are configured for interchangeable use as a plunger 3 of the moved system part 2; and/or a set of a plurality of casting plunger rods 4.sub.1 to 4.sub.n2, shown as a block diagram in FIG. 6, with predefined different mass, which differ in their mass by predefined mass increments and are configured for interchangeable use as a plunger rod 4 of the moved system part 2; and/or a set of a plurality of casting plunger couplings 9.sub.1 to 9.sub.n3, shown as a block diagram in FIG. 6, with predefined different mass, which differ in their mass by predefined mass increments and are configured for interchangeable use as a plunger coupling 9 of the rod drive unit 5 of the moved system part 2; and/or a set of a plurality of casting plunger drive pistons 10.sub.1 to 10.sub.n4, shown as a block diagram in FIG. 6, with predefined different mass, which differ in their mass by predefined mass increments and are configured for interchangeable use as a plunger drive piston 10 of the rod drive unit 5 of the moved system part 2.

(17) Depending on application and the desired total mass of the moved system part 2, the plunger 3 actually used may be selected from the number n1 of present plungers 3.sub.1 to 3.sub.n1 of different mass; and/or the plunger rod 4 actually used may be selected from the number n2 of plunger rods 4.sub.1 to 4.sub.n2 of different mass; and/or the plunger coupling 9 actually used may be selected from the number n3 of plunger couplings 9.sub.1 to 9.sub.n3 of different mass; and/or the plunger drive piston 10 actually used may be selected from the number n4 of plunger drive pistons 10.sub.1 to 10.sub.n4 of different mass. Depending on system design, of the four said sets of plungers 3.sub.1 to 3.sub.n1, plunger rods 4.sub.1 to 4.sub.n2, plunger couplings 9.sub.1 to 9.sub.n3, and plunger drive pistons 10.sub.1 to 10.sub.n4, all four sets may be present for a given plunger system, or only one of the four sets, or any two or three of the four sets may be provided.

(18) In this type of embodiment of the invention, the mass of the moved system part 2 may be adjusted variably between different casting cycles by selection of a different plunger and/or a different plunger rod and/or a different plunger coupling and/or a different plunger drive piston. If necessary, in addition the releasable attachment of one or more additional mass bodies to the moved system part 2 may be provided, as illustrated in the example shown in FIG. 6 by the additional mass body ZK releasably attached to the plunger rod 4. Also, this type of embodiment may if necessary be supplemented by the above-mentioned additional mass unit Z.sub.E which is arranged so as to be movable relative to the moved main system part 2a.

(19) The mass increments by which the respective plungers 3.sub.1 to 3.sub.n1, plunger rods 4.sub.1 to 4.sub.n2, plunger couplings 9.sub.1 to 9.sub.n3, and plunger drive pistons 10.sub.1 to 10.sub.n4 differ in their mass may be predefined suitably depending on circumstances or requirements. Here it is usually convenient to keep the mass increments between each two components with successive mass, and/or the total mass difference between the lightest and the heaviest component of the respective set, within predefined limits. This may be achieved for example by predefining a suitable threshold value by which the mass increments of the respective component set may differ at most, and/or by which the mass of the heaviest component of the respective set may be greater at most than the mass of the lightest component of the set, e.g. given as a percentage.

(20) In corresponding embodiments, the additional mass unit Z.sub.E arranged so as to be movable relative to the main system part 2a comprises an additional mass body Z.sub.M which is arranged on the moved main system part 2 so as to be slidingly movable between a starting position and an end position, wherein the starting position is defined by an initial end stop IA on the moved main system part 2a and/or the end position is defined by an impact end stop AA on the moved main system part 2a. FIG. 5 shows a corresponding exemplary embodiment which has both the initial end stop IA and the impact end stop AA on the moved main system part 2.

(21) In advantageous implementations, at least the initial end stop IA or the impact end stop AA is adjustable on the moved main system part 2, wherein also an adjustability of both end stops IA, AA may be provided. The end stop may as required be adjusted manually, e.g. by a manually actuated screw spindle, or automatically by a corresponding actuator mechanism. In the exemplary embodiment of FIG. 5, the impact end stop AA is provided on the plunger coupling 9, while the initial end stop IA is provided by an initial end stop body 8 which is established so as to be axially adjustable on the plunger drive piston 10.

(22) The additional mass body Z.sub.M may accordingly move slidingly relative to the remainder of the moved system part, i.e. relative to the moved main system part 2a, by a slide stroke or stroke H corresponding to the axial spacing of the starting position and end position. If the moved main system part 2a together with the additional mass body Z.sub.M moves with a predefined advance speed during the mould filling phase, and the moved main system part 2a decelerates at the end of the mould filling phase, the slidingly movable additional mass body Z.sub.M retains this advance speed initially until it has covered its stroke H from the starting position to the end position, and then decelerates at the impact end stop AA. The additional mass body Z.sub.M thus decelerates, at the end of the mould filling phase of the casting cycle, later by a predefined delay time than the main system part 2a, which time results from the quotient of the stroke H divided by the advance speed of the moved system part 2 at the end of the mould filling phase immediately before deceleration of the moved main system part 2a.

(23) In the case of adjustability of at least one of the two end stops IA, AA, which means a corresponding adjustment of the stroke H, according to the above-mentioned functional connection with the stroke H, the delay time by which the additional mass body Z.sub.M decelerates later than the main system part 2a can be predefined variably in the desired fashion, without it being necessary to change the advance speed for the moved system part 2.

(24) In the exemplary embodiment of FIG. 5, the relatively movable additional mass unit Z.sub.E consists solely of the additional mass body Z.sub.M, while in alternative embodiments the relatively movable additional mass unit Z.sub.E comprises one or more further additional mass bodies which are arranged so as to be movable in a desired fashion relative to the moved main system part 2a. In further alternative embodiments, as well as the additional mass unit Z.sub.E, one or more additional mass bodies in the manner of the additional mass body ZK of FIGS. 1 to 3, or in the manner of the additional mass bodies ZK.sub.1, ZK.sub.2, . . . of FIG. 4 are provided, which are configured for releasable attachment to the moved system part 2 and in the attached state form a component of the moved system part 2 which is immovably coupled to the remainder of the moved system part.

(25) While the immovably coupled attachment of additional mass bodies, such as the one additional mass body ZK in FIGS. 1 to 3 or the several additional mass bodies ZK.sub.1, ZK.sub.2, . . . in the exemplary embodiment of FIG. 4, leads to a corresponding additional momentum transfer to the melt material at the end of the mould filling phase precisely at the time of the primary momentum transmission from deceleration of the moved system part 2 or moved main system part 2a, the relatively movable coupling of the additional mass unit Z.sub.E to the remainder of the moved system part, i.e. the main system part 2a, leads to an additional momentum transmission to the melt material which, at the end of the mould filling phase, takes place later by the predefinable delay time than the primary momentum transmission from the deceleration of the moved main system part 2a.

(26) To clarify this using an example with figures, let assume for example that the advance speed of the moved system part 2 towards the end of the mould filling phase is 5 m/s, and the fixed mass of the moved main system part 2a is 100 kg, the mass of the additional mass unit Z.sub.E is 20 kg, and the slide stroke H of the additional mass unit Z.sub.E is 50 mm. Then the additional mass unit Z.sub.E applies to the melt material an additional momentum of 20% relative to the momentum of the fixed mass of the moved main system part 2a, wherein this momentum transmission begins 10 ms after the momentum transmission from the deceleration of the moved main system part 2a. The delayed momentum transmission effect may, favourably for the process, bridge the time period between the first pressure peak, which trails 2 s behind the momentum transmission of the fixed mass of the moved main system part at the time of the end of mould filling, and an action of an optional pressure multiplier device which typically begins only approximately 20 ms to 35 ms after the end of mould filling, without here the first pressure peak being excessively raised, so that any over-injection of the mould can be avoided.

(27) The delayed timing of the additional momentum transmission to the melt material imposed by the additional mass unit Z.sub.E may be influenced in targeted fashion depending on the circumstances or casting parameters, in particular depending on the plunger speed and the structural casting arrangement. By adjusting the end stop, i.e. adjusting the slide stroke H, if required the delayed momentum transmission effect may be adjusted variably in order to optimise the process for the successive casting cycles. Here if desired, also the mass of the additional mass unit Z.sub.E may be varied e.g. by exchanging the additional mass unit Z.sub.E or by constructing the additional mass unit Z.sub.E out of a variable number of additional mass bodies which can be optionally coupled relatively movably to the moved main system part 2a. In this way, the strength and/or timing of this additional momentum transmission to the melt material at the end of the mould filling phase can be adjusted so as to achieve the desired optimal casting quality, which may be determined for example empirically or by computer simulation.

(28) In corresponding implementations of the invention, the moved system part 2 comprises several additional mass units Z.sub.E which are arranged so as to be movable relative to the main system part 2a and, at the end of the mould filling phase of the casting cycle, decelerate later by a respective individually predefinable delay time than the main system part 2a. For each additional mass unit Z.sub.E, in this case their mass and hence the strength of the additional momentum transmission applied to the melt material, may be established individually, as may the time at which they transmit the additional momentum to the melt material by their deceleration. If required, with this embodiment variant, a temporally staggered, successive additional momentum transmission to the melt material may be provided by the several successively decelerated additional mass units Z.sub.E.

(29) In advantageous implementations, the plunger system—as shown for the exemplary embodiment of FIG. 5—comprises a locking unit 11 for releasable locking of the additional mass body Z.sub.M in the starting position or in the end position or in a predefinable locking position between the starting position and the end position. For example, in the implementation of FIG. 5, the locking unit 11 is formed by a locking bar device with a locking bar which is held pivotably on the plunger coupling 9 and engages in a corresponding bar receiver on the additional mass body Z.sub.M when the additional mass body Z.sub.M has reached its end position, i.e. in this case, the impact end stop AA on the plunger coupling 9.

(30) The locking unit 11 ensures that the additional mass body Z.sub.M is held firmly in position after reaching its impact end stop AA. After completion of the casting process, the lock is released so that the additional mass body Z.sub.M can return to its starting position. The return movement of the additional mass body Z.sub.M may optionally, as in the example of FIG. 5, be supported by a return spring arrangement 15 which, in this example, is held on one side on the additional mass body Z.sub.M and on the other side in a receiver in the plunger coupling 9.

(31) FIG. 7 illustrates in a schematic flow diagram a casting method, with only the method steps of interest here, for a die casting machine equipped with a plunger system according to the invention, i.e. in an embodiment of the type shown in one of FIGS. 1 to 6. As known in itself, for the performance of a respective casting cycle, one or more casting parameters are detected which are derived from one or more preceding casting cycles and/or predefined for the impending casting cycle. These casting parameters are detected by a machine control system which is typically fitted to the die casting machine and also forms or comprises a control unit for the plunger system. The control unit for the plunger system, also known in itself, is configured to control or adjust the respective casting process.

(32) Characteristically, in the plunger system, the control unit determines the mass of the moved system part 2 to be set optimally for the impending casting cycle or cycles, and/or the delay time to be set optimally for the impending casting cycle or cycles for the additional mass unit Z.sub.E which is arranged so as to be movable relative to the main system part 2a. Preferably, for this the control unit evaluates actual values, detected by sensors or otherwise and belonging to one or more preceding casting cycles, for one or more casting parameters, in particular casting parameters which influence or represent the quality of the produced casting and/or the effectiveness of the casting process. The control unit is thereby able to optimise the casting cycle automatically depending on the design of the control system, either purely by control and/or iteratively and/or using computer simulations previously performed and/or by means of real-time control interventions during the respective casting process.

(33) According to the method therefore, as indicated in FIG. 7, the mass of the moved system part 2 and/or the delay time for the relatively movably arranged additional mass unit Z.sub.E, for one or more future casting cycles, is adjusted variably depending on the at least one detected casting parameter. Then the casting process is carried out with correspondingly optimised casting process management.

(34) In corresponding embodiments, as part of the performance of the casting processes according to the method and by means of an algorithm suitably stored therein, the control unit is configured to establish—from the plunger position, the plunger speed i.e. the advance speed of the moved system part 2, and the mass of the moved system part 2 or the mass of the moved main system part 2a and the mass of the slidingly movable additional mass unit Z.sub.E—the associated momentum or a momentum equivalent relevant for the momentum transmission to the melt material, and to provide this for further processing. This may for example also be used to indicate or depict, visually or otherwise, the determined momentum transmission effect as a measure of the compression effect of the first pressure peak taking place in the melt at the end of the mould filling phase.

(35) Furthermore, in corresponding embodiments, the control unit is configured to determine—for a desired height of the first pressure peak depending on the influence factors present for the given die casting machine or given plunger system—the necessary mass for the moved system part 2 or the moved system main part 2a and the relatively movable additional mass unit Z.sub.E, or establish this empirically or by computer simulation using a specific map belonging to the casting to be produced. In addition or alternatively, the control unit may be configured to determine the optimal additional mass without knowledge of the actual pressure peak, in this case e.g. empirically from the evaluated casting quality, wherein the plunger speed is varied without changing the momentum effect.

(36) The influence factors in particular are one or more of the following factors: the preselected or actual plunger speed in the mould filling phase; the mass of the moved system part 2 without the relatively movable additional mass unit Z.sub.E and without additional mass bodies ZK, ZK.sub.1, . . . to be releasably attached; the closing force of the mould closing unit of the die casting machine; the impacted area of the casting and/or sprue; the weight of the casting and/or sprue; the casting characteristics, in particular with respect to wall thicknesses; the composition of the melt material; the plunger diameter active in the casting chamber 12; the dimensions of the plunger drive, in particular with respect to diameter and hydraulically effective areas; the hydraulic drive pressure of the plunger drive; the parameters of the optional pressure multiplier device, in particular with respect to dimensions and hydraulically effective areas of the multiplier unit, predefined pressure profile and multiplier system pressure; and the actual and/or maximally possible value for the slide stroke H in the case of a present, relatively movable additional mass unit Z.sub.E.

(37) Also, the control unit may be configured to determine—for a desired height of the first pressure peak with known mass of the present, relatively movable additional mass unit Z.sub.E—the associated value for the slide stroke H depending on said influence factors, or to establish this from a map produced empirically or specifically by computer simulation for the casting to be produced. In this case too, the process may be similar if the actual pressure peak is not known, but the momentum transmission effect has been empirically assessed as good and only the plunger speed is to be varied, without changing the momentum transmission effect. An additional influence factor here, if the locking unit 11 is present, may be its locking state, i.e. whether or not the relatively movable additional mass unit Z.sub.E or the relatively movable additional mass body Z.sub.M is locked by the locking unit 11.

(38) It is understood that selected mass changes for the moved system part 2 may be suitably taken into account by the control unit for the total control of the plunger system. Thus a change in mass of the moved system part 2 requires correspondingly changed drive forces to accelerate the moved system part 2.

(39) The detection of the casting parameters is supported by suitable sensors, as will be readily understood by the person skilled in the art when knowing the sensor tasks. The sensors here may in particular include one or more of the following sensors: one or more limit switches for detecting the presence of immovably coupled additional mass bodies ZK, ZK.sub.1, . . . and/or the relatively movable additional mass unit Z.sub.E; hard-wired and/or wireless identification sensors for identifying individual additional mass bodies and/or assembly components of the plunger system, and in particular its moved system part 2; acceleration sensors, the sensor information from which may be analysed together with sensor data from the casting drive system, in particular with respect to position, pressures etc., in order to determine the total mass of the moved system part 2; a sensor for measuring the actual slide stroke H when the relatively movable additional mass unit Z.sub.E is present; a sensor to detect whether the relatively movable additional mass unit Z.sub.E or additional mass body Z.sub.M is in the starting position; and a sensor to detect, when the locking unit 11 is present, whether the relatively movable additional mass unit Z.sub.E or the relatively movable additional mass body Z.sub.M is in the locked state.

(40) In a characteristic curve diagram for exemplary embodiments, FIG. 8 illustrates the typical development of the internal mould pressure, i.e. the pressure p.sub.S of the melt material in the mould, as a function of the time t for the last part of the mould filling phase and the subsequent pressure-holding phase. Here, a first curve K1 (shown in dotted lines) illustrates a typical time development of the internal mould pressure p.sub.S for a conventional plunger system without pressure multiplier device. The plunger initially moves e.g. with largely constant advance speed, i.e. filling speed, and as soon as the end of the mould filling phase is reached at a time t.sub.E, pressure builds up in the mould which in turn leads to a pressure rise in the casting chamber, whereby the plunger is braked to a standstill, i.e. the momentum of the plunger or the moved system part of the plunger system is dissipated to zero with a corresponding increase of the internal mould pressure. The liquid melt material in the mould to a certain degree acts as compressible, i.e. as a hydraulic spring. At a time t.sub.S, the moved system part of the plunger system comes to a standstill for the first time and the maximum pressure value prevails in the mould, i.e. the first pressure peak. Then a certain damped after-oscillation of the internal mould pressure p.sub.S occurs because of a corresponding damped oscillation movement of the moved system part of the plunger system, between the compressible melt material on one side and the compressible hydraulic fluid in the driving casting apparatus on the other, as evident from the course of curve K1.

(41) A second curve K2 illustrates a typical casting process when a plunger system is used with additional mass immovably coupled to the moved system part 2, e.g. the additional mass body ZK according to FIGS. 1 to 3 or the additional mass bodies ZK.sub.1, ZK.sub.2, . . . according to FIG. 4, and with a pressure multiplier device. Until time t.sub.E at the end of the mould filling phase with the incipient strong pressure rise, the course of the casting process corresponds to that of the conventional case according to curve K1, and here too, said damped after-oscillation occurs on transition to the pressure-holding phase. However, here the internal mould pressure p.sub.S is higher in comparison with the conventional case at the time t.sub.S of the first pressure peak, i.e. curve K2 here lies above curve K1. Also at time t.sub.M, the effect of the pressure multiplier device begins, which then brings the internal mould pressure p.sub.S to a desired higher end value p.sub.F that lies significantly above the end value p.sub.K in the conventional case of the first curve K1 without pressure multiplier device. The rise in internal mould pressure p.sub.S at the time of the first pressure peak t.sub.S is attributable to the additional momentum transmission to the melt material in the mould from the additional mass which is immovably coupled to the moved system part 2 of the plunger system and provided by one or more of said additional mass bodies ZK, ZK.sub.1, ZK.sub.2, . . . and/or by the exchange of corresponding components of the moved system part 2, as explained in FIG. 6, by functionally equivalent components with different mass.

(42) A third curve K3 illustrates an exemplary casting process with use of the plunger system, in an embodiment corresponding to that explained above with respect to the second curve K2, but with additionally present, relatively movably arranged additional mass unit Z.sub.E. Since this additional mass unit Z.sub.E deploys its momentum-transmissive effect to the melt material only later by the predefinable delay time than the moved main system part 2a, the temporal development of the internal mould pressure p.sub.S in this exemplary embodiment, according to curve K3, corresponds to that of curve K2 up to a time t.sub.V at which this delay time has expired and the additional mass unit Z.sub.E decelerates and transmits its momentum additionally to the melt material. This results in a rise in the internal mould pressure p.sub.S at this time t.sub.V, and in the further course of the casting process until the end pressure p.sub.F is reached in the pressure-holding phase, the associated curve K3 lies above the second curve K2 by a corresponding additional pressure. As evident from a comparison of curves K2 and K3, because of the relatively movable arrangement of the additional mass unit Z.sub.E, it is possible to provide a desirable amount of pressure increase for the internal mould pressure p.sub.S in the period between the time is of the first pressure peak and the time t.sub.M of the start of the pressure multiplier effect.

(43) As the exemplary embodiments shown and explained above make clear, the invention provides an advantageous plunger system for use in die casting machines, with which the die casting processes can be significantly optimised or improved relative to conventional casting processes, in particular in the period of time at the end of the mould filling phase and on transition to the pressure-holding phase, which in turn allows an increase in the quality of the produced castings. In particular, the compression, strength, porosity and/or structure formation of the casting may be favourably influenced in that the momentum transmission to the melt material can be varied by the mass change of the moved system part without necessarily having to change the advance speed of the moved system part.

(44) The invention allows, independently of each other, a targeted influencing of the mould filling time imposed by the advance speed of the moved system part 2, i.e. the duration of the mould filling phase, and of the pressure value for the internal mould pressure at the time of the first pressure peak since, according to the invention, this pressure value may be changed by the mass change of the moved system part without changing the advance speed. The invention thus allows for example a plunger system to be used with minimal mass of the moved system part—which in principle is favourable for achieving short mould filling times because of higher predefinable advance speed—and the mass of the moved system part to be increased by said measures as required, in order to achieve a desired pressure level for the first pressure peak and/or a pressure rise in a period after the first pressure peak from the delayed action of the relatively movable additional mass unit, in particular as a bridging measure until a pressure multiplier effect begins.

(45) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.