CASTING DEVICE AND CASTING METHOD

Abstract

A device for casting a metallic component comprising an outer undercut comprises a base body with a first end portion and a circumferential side wall comprising a tapering inner surface; a first die part that is insertable into the base body and that forms a first molding surface for the component to be cast; a plurality of side die parts, which are insertable into the base body and which, in the inserted state, are radially supported against the circumferential side wall of the base body and form a die ring comprising an inner molding surface for the component to be cast; a second die part which is moveable into the die ring formed by the side die parts to a casting position, and which forms a second molding surface for the component to be cast, wherein in the casting position, the second die part is arranged in a completely contact-free manner with respect to the first die part.

Claims

1.-15. (canceled)

16. A device for casting a metallic component, comprising: a base body including a first end portion and a circumferential side wall, wherein the side wall has an inner surface that is tapered in a direction towards the first end portion; a first die part that is insertable into the base body and that forms a first molding surface; a plurality of side die parts that are insertable into the base body, wherein the side die parts are radially supported against the circumferential side wall of the base body in an inserted state, and form a die ring comprising an inner molding surface; a second die part which is movable into the die ring formed by the side die parts up to a casting position for casting, and which forms a second molding surface, wherein, in the inserted state, the second die part is axially movable relative to the side die parts, and is arranged in a contact-free manner with respect to the first die part in the casting position.

17. The device according to claim 16, further comprising an operating device for moving the second die part in the axial direction, wherein the second die part is movable beyond the casting position in a direction towards the first die part to apply pressure to the component to be cast.

18. The device according to claim 16, further comprising a die end ring including a molding surface that is tapered in a direction towards the first end portion, wherein the mold end ring is attached to the base body.

19. The device according to claim 16, wherein the side die parts have outer contact surfaces that interact with the tapered inner surface of the base body such that the side die parts are moved radially inside towards one another upon an axial inserting movement into the base body.

20. The device according to claim 18, wherein the mold end ring is firmly connected to one of the base body and the first die part.

21. The device according to claim 18, wherein the inner molding surface of the die ring formed by the side die parts, and a partial section of the tapering molding surface of the die end ring, connect to one another axially and together form a side wall of the mold cavity.

22. The device according to claim 16, wherein, in the inserted state of the side die parts, a gap is formed between the lower annular edge of the side die parts and the molding surface of the first die part, which gap forms a part of the mold cavity to be filled.

23. The device according to claim 16, wherein the side die parts are each fastened to a respective carrier element, wherein the carrier elements are jointly axially movable for inserting the side die parts into the base body.

24. The device according to claim 16, wherein at least one pressure application unit is provided for applying pressure axially to the side die parts in the inserted state.

25. The device according to claim 23, wherein at least two side die parts and carrier elements are provided, wherein the carrier elements are held in a radially displaceable manner with respect to a holding plate.

26. The device according to claim 25, wherein at least one ramp assembly is provided, which is configured to translate an axial movement in the opening direction into a radial movement of the carrier elements away from one another.

27. The device according to claim 26, wherein at least one axially displaceable operating member is provided, wherein the ramp assembly comprises at least one operating ramp that is assigned to the operating member, and at least one corresponding setting ramp that is assigned to a respective one of the carrier elements, wherein upon axial movement of the operating member in the opening direction the at least one setting ramp slides along the corresponding operating ramp, wherein for each carrier element a respective ramp assembly is provided, wherein the axially displaceable operating member comprises all operating ramps, so that all carrier elements are jointly movable upon axial movement of the operating member.

28. The device according to claim 16, wherein the mold cavity, which is enclosed by the first die part, the side die parts and the second die part, has a volume of at least 0.5 liters.

29. A method for producing a metallic component by a casting device comprising: a base body including a first end portion and a circumferential side wall, wherein the side wall has an inner surface that is tapered in a direction towards the first end portion; a first die part that is insertable into the base body and that forms a first molding surface; a plurality of side die parts that are insertable into the base body, wherein the side die parts are radially supported against the circumferential side wall of the base body in an inserted state, and form a die ring comprising an inner molding surface; a second die part which is movable into the die ring formed by the side die parts up to a casting position for casting, and which forms a second molding surface, wherein, in the inserted state, the second die part is axially movable relative to the side die parts, and is arranged in a contact-free manner with respect to the first die part in the casting position; the method comprising axially inserting the side die parts in a direction of the base body, wherein the outer surfaces of the side die parts are guided along the tapered inner surface of the base body, so that the side die parts are moved radially inside towards one another, until the side die parts are supported against one another in a circumferential direction and form the die ring, and the lower annular edge of the die ring sealingly abuts on the tapered molding surface of the mold end ring.

30. The method according to claim 29, further comprising: die casting a melt of a metal alloy into the casting device, wherein the melt is introduced through an opening in the first die part into the mold cavity from below at a casting pressure, wherein a holding pressure is exerted on the side die parts and the second die part, which pressure is larger than the casting pressure; sensing a pressure signal, which represents the internal pressure in the mold cavity; reducing the casting pressure, when a sudden pressure rise is sensed; after a predetermined time with reduced pressure has passed, applying pressure to the component, which solidifies from the melt, by moving the second die part relative to the first die part, wherein a molding pressure, which is larger than the casting pressure, is applied to the component.

Description

SUMMARY OF THE DRAWINGS

[0026] Example embodiments will be described below by means of the description below referring to the drawing figures, which show:

[0027] FIG. 1 shows an example device for casting a metallic component in the closed state in a perspective view;

[0028] FIG. 2 shows the device of FIG. 1 in an axial view;

[0029] FIG. 3 shows the device of FIG. 1 for casting a metallic component in the longitudinal section in the closed state;

[0030] FIG. 4 shows a detail of the device from FIG. 3 in enlarged illustration;

[0031] FIG. 5 shows the device of FIG. 1 in axially displaced position between upper unit and lower unit in a longitudinal section;

[0032] FIG. 6 shows the device of FIG. 1 in axially displaced position between upper unit and lower unit and partially laterally open position of the side die parts in a longitudinal section;

[0033] FIG. 7 shows the device of FIG. 1 in the completely open state in a longitudinal section;

[0034] FIG. 8 shows the side die parts of the device shown in FIGS. 1 to 7 as a detail in the closed state in a perspective view;

[0035] FIG. 9 shows the side die parts of FIG. 8 in an axial view;

[0036] FIG. 10 shows a detail of a device for casting a metallic component according to a further embodiment.

DETAILED DESCRIPTION

[0037] FIGS. 1 to 10 will be described together below. An exemplary device 2 for molding a component from a metal melt is shown.

[0038] The device 2, which can also be referred to as a casting and molding tool, comprises a base body 3, into which a first die part 4, a plurality of side die parts 5, and a further die part 6 are inserted. In the closed state, said die parts 4, 5, 6 together form a mold cavity 7 for the component 8, which is to be cast. The die parts can also be referred to as mold parts. The shape of the casting device 2 and of the individual die parts 4, 5, 6, respectively, is substantially determined by the shape of the cast component to be produced. All castable metals and metal alloys, respectively, can be used as casting materials which are correspondingly selected according to the technical demands on the component 8 to be produced. The mold cavity can have a volume of between 0.5 and 50 liters, for example.

[0039] In the present embodiment, the device 2 is configured for producing rotationally symmetrical bodies in the form of wheels, for which in particular metal alloys of light metal, such as aluminum, magnesium, titanium and/or further alloy components, can be used. The rotationally symmetrical component 8 to be produced comprises a circumferential undercut 11 between two rim edges 9, 10 arranged at opposite axial ends of the component.

[0040] In the present embodiment, the first die part 4 is arranged at the bottom, respectively is inserted into the base body 3 from the top, which is why it can also be referred to as bottom die part or lower die part. Accordingly, the second die part 6 is arranged above the first die part 5 and can thus also be referred to as upper die part.

[0041] It is to be understood, however, that the arrangement could also be reversed, that is, the first die part could be at the top and the second die part at the bottom.

[0042] The base body 3 is designed in a cup-shaped manner and has an end portion 12, on which the first die part 4 is axially supported in a first direction, as well as a circumferential side wall 13, which extends away from the end portion. The end portion 12 forms a bottom comprising a central opening 14, in which the first die part 4 sits with a connecting section so as to form a seal. The first die part 4 has a central opening 15, through which the metal melt can be pressed into the mold cavity 7 from below the lower die part 4 with hydraulic pressure. The base body 3 can be fastened to a stationary carrier plate 38 that can also be referred to as support plate.

[0043] Starting at the end portion 12, the side wall 13 has an inner surface 16, which widens in the direction towards the free end of the side wall 13 and which is formed conically in the present embodiment. In the inserted state, as shown in FIG. 3, the side die parts 5 are axially and radially supported against the circumferential side wall 13 of the base body 3 and form a circumferentially closed die ring 17 comprising an inner molding surface 18 for the component to be cast. Insofar, the die ring can also be referred to as mold ring. In the present case, the number of the side die parts 5 is four, whereby it is understood that a different number, such as two, three or more than four can be used as well. The division of the individual side die parts 5 is made at regular intervals, that is, four segments are provided, which each extend approximately across one-fourth of the total circumference.

[0044] The side die parts 5 have outer contact surfaces 19, which are designed so as to correspond to the tapered inner surface 16 of the base body 3 and which cooperate therewith in a ramp-like manner. In the present embodiment, the inner surface 16 and the corresponding outer surfaces 19 are designed conically or cone segment-like, respectively, so that the side die parts 5 when being axially inserted into the case body 3 move radially inwardly towards one another, that is, in the direction towards the longitudinal axis A. The die parts 5 thereby increasingly approach one another, until they finally come to rest against one another in the circumferential direction and form a closed, i. e., a gap-free, outer die ring 17, as can be seen in particular in FIGS. 8 and 9. Due to the inner-conical guide surface 16 of the base body 3, a further axial insertion of the die ring 17 into the base body 3 is not possible, so that an end position, respectively a closed position, is defined. In this closed position, the die ring 17 is supported axially and radially against the base body 3.

[0045] As can be seen in particular in FIG. 4, a mold end ring 20 is provided in an end region of the component 8 to be cast, which end ring has a molding surface 22 that is tapered in the direction towards the bottom 12 of the base body 3. In the present embodiment, the mold end ring 20 is inserted into the base body 3 and is attached thereto. The connection can be realized in a force locking manner, for example by a press-fit, in a form-locking manner, for example by screws, and/or in a materially connecting manner, for example by welding. The tapered molding surface 22 of the mold end ring 20 and the inner surface 16 of the side wall 13 form a common inner guide surface for the side die parts 5 to be inserted. From a geometrical and functional view, the mold end ring 20 is thus an integral part of the base body 3, wherein the molding surface 22 of the mold end ring 20 forms a part of the inner surface 16 of the side wall 13. In the inserted condition of the side die parts 5, the casting mold is closed securely with a small clearance. At the same time, the cone surface 19 of the die ring 17 interacts with the counter cone 16 of the base body 3 and the mold end ring 20, respectively, so as to effect a good centering of the mentioned components relative to one another. The axial height of the mold end ring 20 is selected such that, in the closed position, the lower annular edge 21 of the side die parts 5 is arranged inside the mold end ring 20 and sealingly contacts the inner surface 22 thereof.

[0046] To that extent, the surface mating between the tapered outer surfaces 19 of the side die parts 5 on the one side, and the inner surface 16 of the base body 3, respectively the inner surface 22 of the mold end ring 20 on the other side, fulfill a double function, namely that a statically determined sealing stop is formed. Thus, a heat expansion of the die parts 4, 5 that occurs during casting is compensated for by automatic axial fine positioning of the side die parts 5, wherein the side die parts 5 are self-centered with respect to the first die part 4. There is no separate axial end stop for the side die parts, so that a static overdeterminacy is avoided.

[0047] An annular gap 24 is formed between the annular edge 21 of the side die parts 5 and the molding surface 23 of the first die part 4, which gap forms the part of the mold cavity 7 that is to be cast for the rim edge 9. The radially outer end of the molding surface 23 of the first die part 4 is laterally delimited by the tapering inner surface 22 of the mold end ring 20 that here forms a lateral molding surface section for the component 8 to be cast. The inner molding surface 18 of the die ring 17 formed by the side die parts 5, and the molding surface section of the mold end ring 20, axially connect to one another and together form an outer side wall of the mold cavity for the component to be cast.

[0048] An inner side wall of the mold cavity is formed by the second die part 6 that is inserted into the base body 3 prior to the casting and brought into a casting position. This is carried out by a correspondingly suitable operating device 37. In the present embodiment, a main inserting movement of the central die part 6 takes place together with the side die parts 5. For this, said die parts 5, 6 are jointly moved in the direction of the base body 3, until the side die parts 5 have reached their end position, in which they are radially and axially supported against the base body 3 and against the mold end ring 20, respectively. In this end position of the side die parts 5, the second die part 6 can be moved even further relative to the side die parts 5 and the first die part 4, respectively, in order to adjust the mold cavity to the desired dimension. For this purpose, the second die part 6 is moved axially relative to the first die part 4, until the required casting position is reached. It is provided that in the casting position, the second die part 6 is arranged in a completely contact-free manner relative to the first die part 4. On its end portion 28 delimiting the mold cavity 7, the upper die part 6 comprises a circumferential outer surface 29 that forms a seal together with a corresponding circumferential inner surface 30 of the die ring 17. In casting position, the two sealing surfaces 29, 30 have an axial overlap, so that a precise axial adjustment of the casting position is possible by corresponding axial movement of the upper die part 6, without hereby affecting the sealing function.

[0049] The relative movement between the second die part 6 and the first die part 4 is carried out by an operating device 37, which effects the main inserting movement as well as the accurate positioning of the upper die part into the casting position. The operating device 37 is furthermore suitable to move the second die part 6 in the direction towards the base body 3 and towards the first die part 4, beyond the casting position, in order to apply pressure to the component after the casting during the solidification. The operating device 37 is configured to realize different operating functions, namely to effect the axial displacement of the second die part 6 as well as of the side die parts 5 in the axial direction, i. e. towards the base body 3 (closing direction) and away therefrom (opening direction), as well as a displacement movement of the side die parts 5 in the radial direction, i. e. in the direction towards the longitudinal axis A (closing direction) and away therefrom (opening direction).

[0050] For each side die part 5, a respective carrier element 26 is provided to transfer a force to the respective side die part 5 and to move same, respectively. The carrier elements 26 are in each case fastened to an end portion of the side die parts 5, in particular to a front side of the side die parts 5. The fastening can be effected by screws, for example, without being limited thereto. It can be seen in FIGS. 8 and 9 that in the present embodiment four side die parts 5 and correspondingly four carrier elements 26 are provided. The carrier elements 26 engage with their connecting sections 28 through openings 31 of a stationary holding plate 27. The openings 31 are designed as elongated holes, so that the carrier elements 26 can be moved radially with respect to the stationary holding plate.

[0051] The carrier elements 26 can be force-loaded and moved by a respective power unit 25, wherein the power unit 25 acts upon and/or engages a connecting section 27 of the respective carrier element 26. To introduce power evenly into the side die parts 5, the power units 25 act simultaneously on the carrier elements 26. The power units 25 in particular take over the function of holding the side die parts 5 in the closed position in the inserted state, when pressure is introduced into the solidifying component via the operating device 37. The power units 25 can thus also be referred to as holding devices.

[0052] For each side die part 5, a ramp assembly 32 is provided, which is configured to effect an axial movement of the operating plate 33 in the opening direction R2 into a radial movement of the carrier elements 26 in the direction away from the longitudinal axis A. For each carrier element 26, the operating plate 33 thus has two operating ramps 34, which cooperate with a corresponding setting ramp 35 of the carrier element 26. When the operating plate 33 is axially moved in the opening direction R2, the setting ramps 35 of the carrier elements 26 slide along the corresponding operating ramps 34 that are inclined radially outwardly. The operating ramps 34 thereby act on the carrier elements 26 radially to the outside, so that the respective carrier element 26 and the side die part 5 connected thereto, are moved radially outwardly.

[0053] A casting cycle will be described below with respect to FIGS. 3 to 7. FIG. 3 shows the casting device 2 in the closed state, that is, the side die parts 5 are inserted into the casting body 3 and into the mold end ring 20, respectively, up to the end position and the upper die part 6 is adjusted to the casting position, so that the desired mold cavity 7 is at hand. The casting of the melt takes place from below through the opening 15 into the mold cavity 7 by a suitable device (not illustrated). The melt can be pressed in by means of a hydraulic pressure of more than 100 bar, in particular more than 150 bar. The metallic melt is preferably pressed into the mold cavity 7 in a semi-solid state, that is, by a temperature of below the liquidus line of the melt.

[0054] During the pressure filling, a counter pressure (holding pressure), which is larger than the casting pressure, is applied to the side die parts 5 and the upper die part 4. The counter pressure for the side die parts 5 can be introduced by means of the power units 25. The counter pressure for the upper die part 4 can be effected by the net weight thereof or via the central operating unit 37.

[0055] Pressure sensors (not illustrated) can be provided, which sense a pressure signal representing the hydraulic pressure in the mold cavity. By the pressure die casting, the melt gradually fills the mold cavity 7, until it is completely filled. On reaching the completely filled state, the hydraulic pressure rises suddenly, i. e., a measurable hydraulic pressure peak is generated. The casting process is controlled preferably in such a way that the casting pressure exerted on the melt is initially reduced for a defined time, for example for a time period of between one and ten seconds, when sensing such a pressure peak. During this time, the melt solidifies at least partially, in particular in the area of the rim edges 9, 10. The pressure is then increased again, namely to a molding pressure, which is larger than the casting pressure and which can be more than 500 bar, for example. The molding pressure is introduced into the workpiece via the second die part 4.

[0056] After the compete solidification of the workpiece, the casting device 2 is opened again. This takes place in several partial steps, as described below.

[0057] As shown in FIG. 5, the upper die part 6 and the side die parts 5 are initially retracted axially out of the lower die part 4 and the base body 3, respectively. This first retracting takes place as pure axial movement in the direction R2. In the present case, the device 2 is designed such that the upper die part 6 and the side die parts 5 are moved relative to lower die part 4 and base body 3. It is understood, however, that a reverse kinematics is also possible, that is, that upper part and lateral parts are held in a stationary manner and the base body is moved jointly with the lower part accommodated therein. The axially pulled-out position is shown in FIG. 5.

[0058] In the next step, the side die parts 5 are opened, that is, are moved radially outwardly. This takes place by means of the ramp assemblies 32, as described above, in that the carrier elements 26 slide with their setting ramps 35 along the respective operating ramps 34 of the operating plate 33, wherein a further axial movement of the operating plate 33 is transformed into a radial movement of the side die parts 5 away from the longitudinal axis A. The ramp assemblies 32 are dimensioned and/or configured such that the radial movement effected thereby is larger than the depth of the undercut 11 of the component 8 to be produced. FIG. 6 shows a radially open position of the side die parts 5, in which the operating plate 33, with the upper die part 6 fastened thereto, is moved axially upwards relative to the side die parts 5, so that the latter are pushed radially to the outside.

[0059] Subsequently, the upper unit and the lower unit are moved axially further apart, so that the component 8, which is produced, can be removed. This completely open position is shown in FIG. 7.

[0060] FIG. 10 shows a detail of a device 2 for casting a metallic component in a slightly modified embodiment. The device 2 according to FIG. 10 substantially corresponds to the device according to FIGS. 1 to 9, to the description of which reference is made in this respect. Identical details are thereby provided with identical reference numerals, as in the embodiment according to FIGS. 1 to 9.

[0061] The only difference lies in the configuration of the first die part 4 and of the mold end ring 20, which will be described below. In the embodiment according to FIG. 10, the first die ring 4 extends radially to the outside beyond the inner surface 22 of the mold end ring 20. The mold end ring 20 is connected to the base body 3 and is supported, respectively braced, against the first die ring 4 at least in the axial direction. This can be effected by means of screws, for example, which are inserted into the bottom section 12 from below, are guided through corresponding through-openings in the first die part 4 and are screwed into the mold end ring 20 from below. The mold end ring 20 is thus fixedly braced against the upper side of the first die part 4, so that a gap formed between these parts is minimal. A radial gap is preferably provided radially outside between a circumferential outer surface of the first die part 4 and an inner surface of the base body 3, so that heat expansions of the die part 4 can be compensated.

[0062] The described device 2 and method, respectively, always enable a secured closing of the casting mold. The tapering contact surfaces of the lateral parts 5 on one side, and the base body 3 and the mold end ring 20 on the other contribute to this; said contact surfaces can be designed as cone and counter cone for a rotationally symmetrical component. A static overdeterminacy of the system is avoided. Different temperature gradients, which appear in the individual die parts upon casting, have at best only a small impact on the reliable closing of the casting mold. The clearances and the wear are thus small and the production accuracy is correspondingly high. Workpieces comprising an undercut can be produced in a near-net-shape. When using a high pressure-supported casting method, no extensive mechanical locking mechanisms, such as for example a toggle lever mechanism, are required. In fact, the locking can take place solely by correspondingly applying axial pressure to the side die parts 5 and to the upper die part 6, for example by means of hydraulic presses. Due to the stop-free design of the second die part 6 relative to the first die part 4, pressure can still be applied to the component 8 after the casting and after at least partial solidification.

LIST OF REFERENCE NUMERALS

[0063] 2 device [0064] 3 base body [0065] 4 first die part [0066] 5 side die part [0067] 6 second die part [0068] 7 mold cavity [0069] 8 component [0070] 9 rim edge [0071] 10 rim edge [0072] 11 undercut [0073] 12 end portion [0074] 13 side wall [0075] 14 opening [0076] 15 opening [0077] 16 inner surface [0078] 17 die ring [0079] 18 molding surface (5) [0080] 19 contact surfaces [0081] 20 mold end ring [0082] 21 annular edge [0083] 22 molding surface (20) [0084] 23 molding surface (4) [0085] 24 annular gap [0086] 25 power unit [0087] 26 carrier element [0088] 27 holding plate [0089] 28 end portion [0090] 29 outer surface [0091] 30 inner surface [0092] 31 opening [0093] 32 ramp assembly [0094] 33 operating plate [0095] 34 operating ramps [0096] 35 setting ramps [0097] 36 molding surface (6) [0098] 37 operating unit [0099] 38 carrier plate [0100] A axis [0101] R direction