Deep drawing die and method for deep drawing a workpiece

Abstract

A deep drawing die is provided having a top die with a hold-down clamp, a bottom die with a die plate, and at least one device arranged in a flange region, by which the distance between the hold-down clamp and the die plate can be modified in portions or partially. A method for deep drawing a workpiece with a deep drawing die includes inserting a workpiece between top and bottom dies, deep drawing by closing the dies, and controlling at least one actuator to generate a holding force during deep drawing. By selectively increasing forces in the flange feed at selected locations between hold-down clamp and die plate, it is possible to control the flow of material into the die plate and relieve load on regions having high deforming work, so that tears or cracks at these points in the finished component can be prevented.

Claims

1. A deep drawing die comprising a top die having a hold-down clamp configured to contact one surface of a workpiece to be deep-drawn, a bottom die having a die plate configured to contact another surface of the workpiece, and a device arranged in at least one portion between the hold-down clamp and the die plate, said device comprising a die insert and at least one actuator acting upon said die insert for modifying a distance between the hold-down clamp and the die insert at the at least one portion, wherein the device is configured to generate a holding force and comprises a base plate and an adapter, wherein the at least one actuator is arranged between the adapter and the base plate, wherein the holding force can be controlled, wherein the adapter comprises at least one flexure hinge between a fastening region and an oscillation region of the adapter, and wherein both regions are movable relative to each other.

2. The deep drawing die according to claim 1, wherein the top die and/or the bottom die comprises a seat in which the device is held in a positive-fit, force-fit, and/or positive substance-fit manner.

3. The deep drawing die according to claim 1, wherein the device is arranged within at least one of the top die and the bottom die.

4. The deep drawing die according to claim 1, wherein the actuator is a piezo-electric actuator.

5. The deep drawing die according to claim 1, wherein the device further comprises at least one stop setting a minimum distance between adapter and base plate.

6. The deep drawing die according to claim 5, wherein the base plate is composed of modules.

7. The deep drawing die according to claim 6, wherein the modules have a strip-shaped form.

8. The deep drawing die according to claim 7, wherein the modules are connectable to each other.

9. The deep drawing die according to claim 1, wherein each of the at least one actuator comprises a series resistor that protects against rapid discharge and/or disconnects a defective actuator from a line supplying electric power to each actuator.

10. A method for deep drawing a workpiece with a deep drawing die according to claim 1, the method comprising the steps of: a) inserting the workpiece between the top die having the hold-down clamp configured to contact one surface of a workpiece and the bottom die having the die plate configured to contact another surface of the workpiece; b) closing the top and the bottom dies to deep draw the workpiece; and c) introducing a holding force during the deep drawing by the at least one actuator which is arranged in at least one portion between the hold-down clamp and the die plate.

11. The method according to claim 10, wherein the device is arranged in at least one portion between the top die and the bottom die, and wherein the device modifies the distance between the top die and the bottom die in the at least one portion.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

(2) FIG. 1 is a schematic, sectional side view through a deep drawing die according to a first embodiment of the invention; and

(3) FIG. 2 is a schematic, lateral sectional view of a deep drawing die according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 is a sectional side view showing a deep drawing die 1 comprising a top die 2 and a bottom die 3. The top die 2 comprises a hold-down clamp 2a, subjecting a sheet metal plate, being disposed between the top die 2 and the bottom die 3, to a holding force.

(5) Bottom die 3 comprises a die plate 3a, in which a seat 5 for a device 6 is arranged, where the device can generate and modify additional holding force in the deep drawing die 1. The seat 5 within the bottom die 3 is selected in terms of size and dimensions, such that the device 6 can be accommodated therein. The depth of the seat there corresponds to the height of device 6, so that the surface 3b of bottom die 3 connects to the surface 6a of device 6 at the same level. This means that the surfaces 6a, 3b of device and bottom die together form a flat plane of the same surface.

(6) Device 6 is received in a force-fit manner in seat 5, so that only a motion along the height of the device is possible. Other joining techniques are of course also possible, which do allow a modification/displacement along the height of device 6 though holding device 6 in its position. In addition to a force-fit, also a positive-fit and/or a positive substance-fit connection is possible.

(7) Device 6 in the illustrated embodiment comprises a base plate 7 on which piezo-electric actuators 8 are disposed. The piezoelectric actuators extend at a right angle to base plate 7, where they are arranged with one end on base plate 7 and with another end on an adapter 9. Adapter 9 is supported on base plate 7 via a frame 10. Base plate 7, frame 10 and adapter 9 together form a casing in which the piezoelectric actuators 8 are encapsulated. The encapsulation or the casing has the advantage that device 6 with its piezoelectric actuators 8 is protected from oil, grease or dirt, for example.

(8) Adapter 9 comprises a fastening region 9a and an oscillation or movable region 9b. A flexure hinge 11 is located between the two regions. This allows a relative motion between the fastening region and the oscillation region.

(9) A flexure hinge 11 is not a conventional joint; the mobility with a flexure hinge is instead based on the principle of elastostatics. The function of the flexure hinge is ensured by a region of reduced flexural rigidity, which connects the two adjoining regions of higher flexural rigidity to each other. In other words, as shown in FIG. 1, a flexure hinge is a cross-sectional narrowing in a component, namely as in presently illustrated adapter 9.

(10) Due to the fact that piezoelectric actuators comprise piezoelectric ceramic and also have similar fracture behavior like ceramic, device 6 additionally comprises two stops 12a and 12b which limit movement of the movable region 9b of adapter 9 in the direction of base plate 7. The piezoelectric actuators can thereby be protected against mechanical overload.

(11) The one stop 12a is there formed as a shoulder on frame 10. The underside of adapter 9 can rest thereon without the piezoelectric actuators being further compressed in the direction of the base plate.

(12) The same applies to stop 12b which is formed similar to a piezoelectric actuator 8, but is produced from similar material as frame 10 or base plate 7, so that it also prevents movement of the movable region 9b of adapter 9 in the direction of base plate 7. A minimum distance between the adapter and the base plate can be set in this manner.

(13) Adapter 9 or fastening region 9a is connected in a force-fit manner via frame 10 to base plate 7. This can be realized, for example, by a bolted connection. Other types of connections, such as welding, are of course possible.

(14) Device 6 furthermore comprises a die insert 14, which is formed similar to a cup and in the depression of which a force diversion surface 13, adapter 9, frame 10, and base plate 7 are received.

(15) A force flow is generated by use of this configuration which, starting from the generators, the piezoelectric actuators, acts upon adapter 9 or upon its oscillation region 9b and then upon force diversion surface 13.

(16) By supporting actuators 8 on base plate 7, oscillation region 9b and force diversion surface 13 move upwardly. The force flow furthermore flows from force diversion surface 13 toward die insert 14, which is thereby raised from seat 5. The forces generated or the force flow thereby presses die insert 14 against sheet metal plate 4. Consequently, in the region of device 6 or in the region of die insert 14, sheet metal plate 4 is pressed against hold-down clamp 2a with a force higher than in the regions between hold-down clamp 2a and die plate 3a, in which no device 6 is disposed.

(17) The advantage of generating an additional force at a particular location, between hold-down clamp 2 and die plate 3a or in the flange of the workpiece or the sheet metal plate located between the draw ring and the hold-down clamp, is controlling the feed or the inflow of the flange into the die plate.

(18) In other words, due to the force of hold-down clamp 2a, adjustable in the forming process in the portion in which device 6 is arranged, pressure can be exerted onto sheet metal plate 4, which changes the flow characteristics of the sheet metal material in the portion subjected to the pressure. The increased pressure influences the flow characteristics in such a manner that an increased level of friction is generated, particularly in the region between sheet metal plate 4 and top die 2 or hold-down clamp 2a and also between sheet metal plate 4 and bottom die 3 or die plate 3a.

(19) The flow characteristics of the regions of sheet metal plate 4 located around this portion are thereby of course also influenced. Because, while in one region the flow is prevented by a higher holding force, more material flows from other surrounding regions. Consequently, the flow characteristics of sheet metal plate 4 or its material can be controlled during a deep drawing process by the skillful arrangement of device 6.

(20) FIG. 1 also shows that seat 5 within die insert 14 has a depth that enables device 6 to be accommodated entirely therein. In the present example, die insert 14 is even configured such that its height corresponds exactly to the height of seat 5.

(21) The force diversion surface 13 therefore serves as a fitting piece adjusting the correct height of base plate 7, frame 10, adapter 9, and force diversion surface 13 to the exact depth of the cup of die insert 14.

(22) In the event that die insert 14 does not have the exact depth of seat 5, the height of device 6 can be adapted by use of force diversion surface 13 to the depth of seat 5, i.e. the distance from the bottom of seat 5 to the upper edge of seat 5. A planar surface between surface 3b of bottom die 3 and surface 6a of device 6 can thereby be created, or surfaces 6a and 3b can in this manner be made to connect at the same level.

(23) The piezoelectric actuators 8 are connected to a controller (not shown) that allows the actuators to expand or contract.

(24) In the event of actuation of piezoelectric actuators 8 for expansion, i.e. elongation, a force acts upon the moving region 9b of adapter 9, whereby the latter is spaced from base plate 7. Due to the increase of the spacing between adapter 9 and base plate 7, an additional holding force is transmitted via force diversion surface 13 onto die insert 14, which presses sheet metal plate 4 in the region of its extension against top die 2 or against hold-down clamp 2a. In this manner, sheet metal plate 4 is held during deep drawing with a greater force between hold-down clamp 2a and device 6 or die insert 14, whereby the flow of material into the die plate mold caused by a punch (not shown) can be manipulated. It is possible thereby to relieve regions having high deforming work.

(25) Advantageously for this, device 6 is arranged in the vicinity of such a region. Particularly preferably, at least two such devices are arranged adjacent to a region having increased deforming work, which are located in particular at corner areas. A so-called tear in the deep-drawn mold can be prevented in this manner.

(26) FIG. 1 also shows that piezoelectric actuators 8 are arranged consecutively. It is shown in the specific view of FIG. 1 that actuators 8 are arranged in a row. Also, further piezoelectric actuators are located behind the illustrated actuators 8, so that in total, an arrangement in rows and columns of piezoelectric actuators 8 on base plate 7 arises.

(27) FIG. 2 shows a further embodiment of the invention, which is identical to the one previously presented in FIG. 1, but with the difference that base plate 7 is built up of various modules 15, i.e. is modular.

(28) The starting point for the modular structure is that piezoelectric actuators 8, after polarization completing the essential manufacturing steps for initiating the electromechanical properties, do not exhibit uniform length. In an arrangement in rows and columns, selection of the piezoelectric actuators according to length and their division into classes can be necessary to homogenize the distribution of forces.

(29) This means that, for the use of many classes, it is proposed to set up rows of actuators using actuators of one class, i.e. having the same length and the same expandability, on a module of a strip-shaped base plate and to assemble it, as shown in FIG. 2, to form a base plate 7.

(30) The individual modules 15 forming base plate 7 are connected to each other such that they are connected in a force-fit manner, for example by bolts (not shown).

(31) Here, the bolt connection of the strip-shaped modules is a viable solution and is effected in that all actuators 8 uniformly abut adapter 9. Subsequent processing of the undersides of the assembled strip-shaped modules 15 results in the contact surface 16 being plane-parallel to the connection plane of the piezoelectric actuators for support in deep drawing die 1. Grinding over piezoelectric actuators 8 as an alternative solution is problematic, in particular due to the effort for preventing mechanical stress and also due to the risk of contamination.

(32) As shown in FIG. 2, the connected modules 15as already mentionedhave a different height profile which results from the different lengths of piezoelectric actuators 8. Nevertheless, in order to obtain a planar surface on the underside of device 6, it is possible to machine the uneven underside of modules 15 and base plate 7 by use of a milling cutter or a grinding machine, such that a planar surface is created along indicated contact surface 16.

(33) A further option according to the invention for creating a common planar underside of the joined strip-shaped base plates is leveling by use of a high-strength casting compound (not shown). Here, after connecting the individual modules to form a base plate 7, the base plate is inserted in a mold into which a casting compound is introduced to create a planar contact surface.

(34) In both cases described, device 6 comprises die insert 14, force diversion surface 13, adapter 9, frame 10, and base plate 7, whereby the distance created by the piezoelectric actuators 8 or the holding force generated is transmitted directly onto sheet metal plate 4.

(35) It is instead possible that the device comprise merely adapter 9, frame 10 and base plate 7. However, the holding force generated is then transmitted indirectly onto sheet metal plate 4 via force diversion surface 13 and die insert 14.

(36) The invention relates to a deep drawing die having a top die and a bottom die, wherein the top die has a hold-down clamp and the bottom die has a die plate, and wherein at least one device is arranged in a flange region, by which the distance between hold-down clamp and die plate can be modified in portions or partially.

(37) The invention further relates to a method for deep drawing a workpiece with a deep drawing die, wherein a workpiece is inserted between a top die and a bottom die and deep-drawn by closing the top and bottom dies, and wherein at least one actuator is controlled to generate a holding force during deep drawing.

(38) Essentially, the invention presented controls the flange feed of a workpiece in the tool by pressure distributions which are adjustable in the forming process. By selectively increasing forces in the flange feed at selected locations between hold-down clamp and die plate, it is possible to control the flow of material into the die plate during deep drawing. Using this control, it is possible to relieve the load on regions having high deforming work, so that tears or cracks at these points in the finished component can be prevented. This involves increasing the friction between die plate and plate or between plate and hold-down clamp by generating holding forces, as a result of which the material is held fast and prevented from flowing at this location.

(39) It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.