EP1201335B1 - Device for producing pressure die castings, especially from non-ferrous metals - Google Patents

Abstract

Device for producing non-ferrous metal cast parts comprises a hot chamber die casting machine having a riser formed in the casting container; a mouthpiece (11) arranged before a feeder system; and a chamfer before a die casting mold (16, 16a). The chamfer is part of a hot channel feeder system (13) that provides heat for the channels (14) and the nozzles (15) up to the mold. Preferred Features: Nozzle tips (23, 23a) are formed on the nozzles and are connected with a cam or compartment feeder system directly to the mold. The nozzle tips and the nozzles have conical connections for sealing.

Description

The invention relates to a device for producing metal die-cast parts, in particular of non-ferrous metals, according to the preamble of claim 1.

Hot chamber die casting machines with associated mold design are known. In hot-chamber die casting, the non-ferrous metals zinc and magnesium and, to a lesser extent, lead or tin are cast. Metal has the ability to cool quickly. In die casting, it is therefore poured to achieve the best casting quality, at high speed and high pressure. Depending on the part size and minimum wall thickness, the mold filling process is between 5ms and 30ms. The closing force of hot chamber machines is up to 10000kN.

During the casting process, there are certain empirical values for the calculation of the casting system, which are, for example, for zinc at a maximum gate speed of approx. 50 m per second and for magnesium at a maximum of 100 m per second. At the high melting temperatures used of about 650 ° C for magnesium and about 420 ° C for zinc, these non-ferrous metals in the liquid state are almost as fluid as water. In order not to exceed the previously mentioned gate speed, the cross-section of the gate area, ie the part of the gate system which subsequently allows the separation of the gate from the mold, must be designed accordingly in its cross-section.

It is also known ("The Operation of the Die Casting Machine", Society of Die Casting Engineers, Detroit / USA Copyright 1972, page 7) that the hot chamber die casting process uses a fan or tangential sprue to evenly fill the die casting. This leads, especially when multiple forms are used, to a complex gate system, which remains after the metal has cooled as an unusable residue. This Angußanteil has, based on the diecast part, a weight proportion between 40% and 100%. The remaining after each shot sprue is then melted again, but this requires a considerable additional energy. There are also material losses due to burning, deburring of the sprue and recycling of the same.

In the patent US 3,903,956 a hot chamber die casting machine of the type mentioned is disclosed, which is of a type with a so-called self-tearing shape. The runner system in the local molding machine includes a runner which is heatable in a portion adjacent to an entry-side runner within a fixed runner block fixed to a fixed mold half and therefrom along a parting line between the fixed runner block and a movable mold fixed to a movable mold half Runner block and along a dividing line of solid and movable mold half leads to the mold. At the formabgewandten side has the movable Angußblock an undercut, with which it entrains the sprue of the cast part when opening the mold and thereby tearing off the material in the underlying Laufkanalabschnitt. Due to the system remains in this way a relatively long sprue. This type of machine is also only suitable for casting parts that are compatible with this self-tearing technique.

The invention has for its object to provide a configuration in a device of the type mentioned, can be used in the work with much less Angußanteil.

The invention solves this problem by a device having the features of claim 1. The inventive design, it is possible to keep the material in the always required, sometimes very complex runners in the liquid state, so that after the cooling of the metal in the Form no cooling of the material located in the runners occurs. This material can be reused on the next shot.

In plastic injection molding machines, it is in principle known to provide hot runner systems. However, since the heat-conducting properties of plastic deviate decisively from those of metals, it is not possible to transfer the design of such hot runner systems in which punctiform or through a tunnel the mold can be filled.

In a further development of the invention it is provided that nozzle tips are attached to the nozzles provided with a Kammanguß- or Fächerangußsystem and connect directly to the contour of the part, wherein the comb or Fächerangußsystem forms the gate or this is immediately upstream. This embodiment has the advantage that the metal melt located in the gate cross section of the nozzle tips at least in the semi-solid state passes, because the nozzle tips are not heated themselves. As a result, this material prevents metal from flowing out of the hot runner system after the mold has been opened, or from passing back into the mouthpiece, the riser channel or the casting container.

In a further development of the invention while nozzle tips and nozzles are each provided with conical plug-in connections, which ensure a sufficient seal by the application of metal to metal even at the aforementioned, very high temperatures of 650 ° C and 420 ° C.

The nozzle tips themselves can be plugged into heated nozzles and the nozzles in turn to the heated channels.

In a further development of the invention, the nozzle tips can be adapted to the particular shape of the part to be produced. The nozzle tips can be attached to this form laterally or centrally.

An alternative to preventing the backflow of the liquid metal into the riser and the pouring vessel can also be achieved by associating with the mouthpiece an unheated nozzle tip adjacent the runner system in which a plug forms after mold filling, which in turn forms the return flow in the mouthpiece and rising pipe melt can prevent the casting container. This plug is pressed in the next shot in the hot runner system, where a corresponding receiving space is provided for the plug into which the plug passes and thereby the further injection liquid material is not further hindered. The plug melts again in the hot runner system.

In order to avoid in each case a return to the casting container, in addition to or instead of the alternative just mentioned with a mouthpiece can also be provided that a check valve is arranged in the riser. A check valve can also be arranged in the casting piston, so that the disadvantage occurring so far in die casting machines, that when the withdrawal of the casting piston from the riser channel no material flows through the material occurring in the casting cylinder vacuum material flows past the piston rings in the casting cylinder, avoided can be. By arranging a check valve in the casting piston, material can now flow directly from the casting container through the casting piston into the casting cylinder. The check valves to be used in this case should be made of high-temperature resistant metal or ceramics in view of the high temperatures that occur.

Fig. 1

die schematische Darstellung der Gießeinheit einer Warmkammer-Druckgießmaschine mit dem an den Angußkanal der Form angesetzten Mundstück,

Fig. 2

die schematische Darstellung des nach der Erfindung vorgesehenen Heißkanalangußsystems, das in die Form führt,

Fig. 3

eine vergrößerte Darstellung des Übergangs aus dem Heißkanalsystem in die Form, gemäß der linken Form der Fig. 2,

Fig. 4

eine schematische Darstellung, der für die Formfüllung verwendeten Düsenspitze der Fig. 3 in etwa längs der Linie IV-IV der Fig. 3 geschnitten,

Fig. 5

eine vergrößerte Darstellung des Überganges vom Heißkanalsystem zur Form, entsprechend der rechten Form der Fig. 2,

Fig. 6

die Schnittdarstellung der Düsenspitze und des Angusses längs der Linie VI-VI der Fig. 5 geschnitten,

Fig. 7

eine Darstellung ähnlich den Fig. 3 oder 5, jedoch mit einer anderen Anordnung des Übergangs der Schmelze zur Form,

Fig. 8

die schematische aber vergrößerte Ansicht der Düsenspitze in Richtung des Pfeiles VIII jedoch ohne die vorgeschaltete Düse,

Fig. 9

eine Teilansicht der Gießeinrichtung einer Warmkammer-Druckgießmaschine ähnlich Fig. 1, jedoch mit Rückschlagventilen in der Steigbohrung und im Gießkolben und

Fig. 10

schließlich die schematische Darstellung des Endes des Mundstückes mit einer angesetzten nicht beheizten Düsenspitze.

The invention is illustrated by means of embodiments in the drawing and will be explained in the following. Show it:

Fig. 1

the schematic representation of the casting unit of a hot-chamber die casting machine with the attached to the runner of the mold mouthpiece,

Fig. 2

the schematic representation of the invention provided Heißkanalangußsystems that leads into the mold,

Fig. 3

an enlarged view of the transition from the hot runner system into the mold, according to the left-hand mold of Fig. 2,

Fig. 4

3 is a schematic representation of the nozzle tip used for the mold filling of FIG. 3 cut approximately along the line IV-IV of FIG. 3,

Fig. 5

an enlarged view of the transition from the hot runner system to the mold, according to the right-hand mold of Fig. 2,

Fig. 6

cut the sectional view of the nozzle tip and the sprue along the line VI-VI of Fig. 5,

Fig. 7

a representation similar to FIG. 3 or 5, but with a different arrangement of the transition of the melt to form,

Fig. 8

the schematic but enlarged view of the nozzle tip in the direction of arrow VIII, but without the upstream nozzle,

Fig. 9

a partial view of the casting of a hot-chamber die casting machine similar to FIG. 1, but with check valves in the riser and the casting and

Fig. 10

Finally, the schematic representation of the end of the mouthpiece with an attached unheated nozzle tip.

Fig. 1 shows first more or less schematically the casting container 1 of a hot-chamber die casting machine, which is inserted into the melt 2 of the metal to be cast, for example magnesium or zinc. This molten metal 2 is held within a crucible 3, which is used in a manner not shown in a holding furnace.

The casting container 1 has a casting cylinder 4 with a casting piston 5, which is not shown in detail, because known manner provided with a subsequent to its piston rod 6 drive, which may be hydraulic or electrical type. The casting cylinder 4 has in its upper region a lateral inflow opening 7, through which the melt 2 can flow into the interior of the casting cylinder 4 when the piston 5 is in a position lying above this opening 7. In the illustrated state, the casting piston 5 has exceeded the filling position and is moved in the direction of the arrow 8 down, wherein the melt located in the casting cylinder 4 and in the casting cylinder 4 subsequent riser 9 melt on the - heated - nozzle 10 is supplied to the sprue tip 11 which is located in the schematically indicated solid mold half 12.

While now lead in conventional die-casting process with hot-chamber die casting machines from Angusmundstück 11 from rotor channels each to the mold cavities and pass into these on the gates, in the device according to the invention, the Angussmundstück 11 part of a Heißkanalangußsytemes 13, which is a heating of the rotor channels 14 and these downstream nozzles 15 to the mold 16 provides.

It is known that, in the conventional die casting method, the molten metal pressed by the casting piston 5 through the riser bore and mouthpiece die 10, which enters the mold via the runner channels and the respective gates, is kept under pressure until it solidifies. After opening the mold and optionally after retraction of the cores, if such belong to the mold, the casting remains in the movable, not shown here mold half, while the casting piston 5 moves back to its original position, dashed in Fig. 1 with 5 ' is indicated. During this backward movement, the melt located in the nozzle mouthpiece 10 and in the rising bore 9 is sucked back into the casting cylinder 4. The melt in the mold is solidified.

After opening the mold and ejecting the parts, they must be deburred, which means that the runner, runner channels and overflows are separated from the casting. This entire cast residue is then melted down and processed again. As has already been indicated, this requires a relatively large amount of work and energy expenditure, because this casting residue is - in terms of weight percent - between 40% and 100% of the weight of the manufactured parts.

The hot runner system 13 according to FIG. 2 now avoids the occurrence of such considerable cast residues. It can initially be seen in FIG. 2 that the sprue tip 11 is surrounded by a heating sleeve 17 is surrounded, which is supplied via the connecting line 18 with energy. The heating sleeve, as well as the still to be provided heating sleeves 19 and the heating cartridge 20, which serve to heat the nozzles 15 and for heating the channel 14, be supplied with electric current. FIG. 3 now shows that the nozzle 15 is provided with a cone 21 in front of the mold cavity 16 and is inserted therewith into the associated receiving cone of the part 22 of the hot runner system 13 and kept sealed there. In this way, a metal to metal seal is achieved, which is required at the high temperatures when casting non-ferrous (NE) metals (650 ° C for magnesium and 420 ° C for zinc). In these heated nozzles 15, a nozzle tip 23 is now inserted at the end facing away from the cone 21, and also with a cone 24 which is inserted tightly and firmly into a corresponding counter-cone of the nozzle 15.

The nozzle 23 itself is provided at its lower end with comb-like injection channels 25 which open directly into the mold cavity 16. The cross-section of all the injection channels 25 must correspond as a whole to the gate cross-section, which is necessary according to the empirical values for the production of a particular shape which are valid for the hot-chamber die-casting method. In this way it is ensured that the casting speed occurring in these channels 25 does not exceed the permissible maximum speed, as has already been mentioned at the outset.

It is readily apparent that in this case the melt present in the hot runner system 13 can be maintained at a temperature at which it is still in the liquid state. The melt held under pressure in the mold 16 after completion of the pressure casting process solidifies relatively quickly. The melt located in the comb gate of the plurality of channels 25 is at least in the semi-solid state. The nozzle tip 23 is, as can be seen, not heated and it is located in the region of the mold cavity 16. This gate, which is formed by the plurality of channels 25 is separated on removal of the movable mold half 26 of the remaining on the fixed mold half 12 channel portion 27, so that no solidified sprue remains, the then again would have to be melted down.

The same applies to the form 16a, which is additionally indicated schematically and by way of example, and which is connected to the nozzle 23a via a gate fan 28 (FIG. 6) with a gate 29 merging into the mold cavity 16a. Here, in the nozzle 23a, the runners 25a are located at the bottom of the nozzle and extend substantially in the direction of the axis of the nozzle 15a. Below the nozzle tip 23a therefore arises during casting of the sprue fan 28, which merges via the gate 29 in the mold cavity 16a. When separating the movable mold half 26 from the part 27 of the Heißkanalangußsystems 13, the Sprue fan 28 is ejected with. He can then easily be separated from the finished part of his bleed 29. The nozzle tips 23 and 23a of Figs. 3 to 6 have each been designed so that the sprue takes place laterally at the nozzle.

FIGS. 7 and 8 now show a further possibility of configuring a nozzle tip 23b, which in turn is connected to the nozzle 15b via a cone 21b. This nozzle tip 23b is placed with its sprue channels 25b and 30 centrally on the mold cavity 16b and thereby causes the melt is pressed centrally directly into the mold cavity 16b. Due to the multiplicity of channels 25b or 30 also used here, all of which - as well as in the case of the nozzle tips 23 and 23a of FIGS. 3 to 6 - can have diameters of approximately 1 mm to 1.5 mm, a kind of comb casting also arises when opening the mold easily, both from the nozzle tip and then from the diecasting, solve.

By way of illustration, it should be pointed out that the non-ferrous metals used, such as, for example, magnesium and zinc in the liquid state, i. So at their melting temperatures of about 650 ° C for magnesium and about 420 ° C for zinc, almost as fluid as water. You can therefore easily push through the "Kammanguss" in the corresponding mold cavities. The mold filling process requires times of the order of between 5 ms and 30 ms. The material in the mold then solidifies relatively quickly, while the material in the small bores 25, 25a and 25b of the nozzle tips 23, 23a and 23b merges into the semisolid phase and thereby terminates the hot runner system 13 at the completion of the die casting process. On the next shot, this material, which is still in the semisolid phase, is pressed into the mold.

When using the Heißkanalangußsystems 13 is also important to ensure that no liquid metal on the nozzle 10 and the riser hole 9 is pulled out of the Heißkanalangußsystem 13 upon retraction of the casting 5. If that were the case, the next shot could only take place with a certain time delay, because the run channels of the hot runner system 13 and possibly also riser 9 and mouthpiece 10 would first have to be refilled with melt.

9 therefore provides that the casting piston 5 'is equipped with a check valve 31, which allows the molten metal in the container 3, in the withdrawal movement of the casting piston 5' in the direction of the arrow 32 from above through the casting piston in to flow in the space of the casting cylinder 4 below. A negative pressure in the casting cylinder 4 during the return movement of the casting piston 5 ', which occurs in conventional systems when the mouthpiece is completed, therefore does not arise. In addition, a further check valve 32 is inserted at the lower end of the riser 9, so that here, too, no reflux of melt due to its own weight can take place. The liquid melt therefore remains in the Heißkanalangußsystem 13, in the nozzle 10 and in the riser until the next shot. Since, in this respect, the hot melt is applied directly to the part or to the mold cavities 16, 16a, 16b, the casting process is shorter and more accurate to control.

Finally, FIG. 10 shows a further possibility of preventing the reflux of melt from the hot runner casting system 13 in a relatively simple manner. Between the sprue tip 11 of the Heißkanalangußsystems 13 and the heated in a known manner by an electrically or inductively acting heating coil 33 nozzle 10, a mouthpiece body 34 is used, which is not heated and therefore forms a "freezing zone". After each shot, a cold plug 35 will be created within this mouthpiece body 34, which seals the through hole of the nozzle 10. Melt in the hot runner system 13 can therefore not flow back through the Angussmundstück 11.

Fig. 2 shows that the Heißkanalangußsystem 13 in alignment with the passage bore 36 of the mouthpiece 10 on the rotor channel 14 has a receiving space 37 (Fig. 2), in which the plug 35 is collected at the next shot and therefore not through the channel system to the mold cavities can get. This plug melts in the hot runner system 13 until the next shot.

Claims (14)

1. Device for producing metal pressure die castings, in particular from non-ferrous metals, with a hot-chamber pressure die-casting machine which comprises a standpipe (9) formed in a casting vessel (1), a gooseneck nozzle (10) adjoining the standpipe and a gate system (13) which includes a gate gooseneck (11), which can be coupled to the gooseneck nozzle, and at least one runner (14) which leads away from the gate gooseneck and opens by way of a respective ingate into a pressure die-casting die (16, 16a, 16b), characterised in that the gate system is formed as a hot runner gate system (13) which has a plurality of runners and means (17 to 20) for heating the runners (14) up to the respective ingate opening into the pressure die-casting die.
2. Device according to Claim 1, characterised in that the hot-runner gate system is formed as a comb or fan gate system, wherein nozzle tips (23, 23a, 23b) applied to nozzles (15, 15a, 15b) are provided, these directly adjoining the die cavity (16, 16a, 16b) by way of comb- or fan-like gate ducting and therefore forming the respective ingate or being mounted directly before this.
3. Device according to Claim 2, characterised in that the nozzle tips (23, 23a, 23b) and nozzles (15, 15a, 15b) are in each case provided with conical plug-in connections (21, 21a, 21b) for sealing purposes.
4. Device according to Claim 2 or 3, characterised in that the nozzle tips (23, 23a, 23b) are fastened to the nozzles (15, 15a, 15b), and the nozzles are connected to the heatable runners (14) and can be heated.
5. Device according to Claim 2, characterised in that the nozzle tips (23, 23a, 23b) are formed so as to be adapted to the die (16, 16a, 16b).
6. Device according to Claim 5, characterised in that the nozzle tips (23, 23a, 23b) can be applied laterally or centrally to the associated die cavity (16, 16a, 16b).
7. Device according to any one of Claims 2 to 6, characterised in that the gate ducts (25, 25a, 25b) of the nozzle tips (23, 23a, 23b) have such a small cross section that the melt which is located therein changes to the semi-solid state after the die is filled.
8. Device according to Claims 1 and 2, characterised in that an unheated nozzle top (34), which lies against the gate system (13), is associated with the gooseneck nozzle (10), which tip is designed such that a plug forms therein after the die is filled.
9. Device according to Claim 8, characterised in that a collecting space (37) for the plug (35) ejected from the nozzle tip (34) when the next shot takes place is provided in the hot-runner gate system (13).
10. Device according to Claim 9, characterised in that the collecting space (37) is disposed in alignment with a bore (36) of the gooseneck nozzle (10) of the hot-chamber pressure die-casting machine.
11. Device according to any one of Claims 1 to 10, characterised in that a non-return valve (32) is disposed in the standpipe (9).
12. Device according to Claim 11, characterised in that the non-return valve (32) is provided at the bottom end of the standpipe (9).
13. Device according to any one of Claims 1 to 12, characterised in that a non-return valve (31) is disposed in the plunger (5').
14. Device according to any one of Claims 11 to 13, characterised in that the non-return valve(s) (32, 31) consist(s) of a high-temperature resistant metal or of a ceramic material.

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