DE10043209A1 - Flexible tool for forming a workpiece - Google Patents

Abstract

The invention relates to a flexible tool for forming a contact surface for a workpiece when the workpiece is formed. The tool comprises: DOLLAR A a tool frame (4), DOLLAR A a first shaped element (11) which forms part of the contact surface, DOLLAR A and a second shaped element (11) which forms a second part of the contact surface and relative to the first Shaped element (11) axially, namely in a direction perpendicular to the contact surface, is movably mounted in the tool frame (4). DOLLAR A In a tool designed as a die, the second shaped element (11) is axially resiliently mounted in such a way that it can be moved axially from a starting position into a fixed end position against a resistance force (D; Dn).

Description

The invention relates to the forming of workpieces using a flexible Tool.

"Forming sheet metal tubes", 12-1991, pp 33-37, is a forming device for Thermoforming known with a flexible thermoforming stamp. The tool consists of a matrix of several individually adjustable rod elements, which together form the Form the deep-drawing die. The setting of the bar elements takes place outside the forming device in an adjusting device. The stamp is on the desired final shape and set back in for forming workpieces the forming device installed. DE 44 17 460 A1 proposes the flexible Stamp as a flexible die for forming with a printing medium use. During the forming process, a free forming zone is first formed, and the workpiece lies against the die in the course of the forming process. By a suitable, not specified movement of the die should Forming process can be influenced positively.

A flexible draw die is known from WO 96/17697 for stretch drawing. The stamp is formed by a multiplicity of stamp elements which form one Matrix are summarized. The final shape of the stamp is adjusted by the Stamp elements formed in the stretching device.  

An object of the invention is also by reshaping a workpiece to be able to produce complex workpiece shapes precisely.

The invention relates to the forming of workpieces by pressing or Applying to a shape and / or pressing a shape against the workpiece. Becomes the workpiece for forming by means of a force directed against the mold pressed the form, for example in a deep drawing, so forms a die Shape. Is the forming force by extending the mold against the workpiece from applied to the form, such as during stretch drawing, forms a Stamp the shape. As far as the term "tool" is used in the following, should this term encompasses both a die and a stamp.

The workpiece is preferably one before forming flat, preferably flat workpiece, for example a thin plate Sheet metal or a similar semi-finished product. The tool forms a contact surface for the Workpiece. It has a frame and at least two form elements, each one Form part of the contact surface. At least one form element of the at least two Shape elements is relative to the other shape element of the at least two Shaped elements axially movable in the frame, so that the through Form elements formed contact surface can be changed. Act in this sense the tool is a flexible tool. "Axial" is in the sense of Invention any direction that is related to a tool Workpiece underside has a vertical directional component. Preferably the shaped element is mounted so that it can be moved in a straight line. The form elements of a die according to the invention are also called die elements below. Accordingly, the shaped elements of a stamp according to the invention in also referred to as stamp elements.  

According to the invention, the axially movable die element is axially flexible stored. The matrix element is under the action of a on the contact surface of the Force acting element and axially move against a resistance force and is resilient in this sense. When storing the at least one movable die element is preferably a plain bearing. The workpiece can or at least during the entire forming process during part of the forming process permanently against such a gradual yielding die element pressed and in permanent contact into the desired final shape can be formed. This allows the material flow in the Workpiece to be checked precisely. Even three-dimensional curved shapes can be manufactured more precisely. Deep drawing, a particularly preferred one Forming or deepening can be done in several stages. As well can the movable die elements or the at least one movable Move the die element continuously during the entire forming process become. Advantageously, the workpiece is used throughout Forming process fully supported. Tears in the formed workpiece avoided more safely. The advantages mentioned above can be fundamentally through the flexible stamp according to the invention can also be obtained during stretch drawing.

The resistance force in the case of a die is preferably a fluid damping force. The damping force can be achieved by displacing an incompressible fluid, i. H. one Hydraulic fluid, or a compressible fluid, such as air, is generated become. A spring force can also use the resistance force alone or in combination form with a damping force. When using a compressible fluid as Damping fluid is inherently a spring damping force. In preferred embodiments, however, the resistance is solely by a displacing hydraulic fluid generated. Basically, giving in can also be done alone against mechanical frictional resistance. Likewise, a motorized method with motorized travel speed still as  giving in, although this is not preferred embodiments.

Although already a matrix with only two matrix elements, at least of which one is designed according to the invention, advantageously in deep drawing, for example or depths or even just bending the workpiece, the die preferably has a plurality of die elements which are as in the well-known stamps are combined into a matrix, but each individually in the die frame against one resistance or one for all or several the die elements are resiliently mounted with the same resistance. The Resistance is preferably individual for each of the die elements variable.

The workpiece can be pressed against the die using a stamp.

However, the forming is preferably carried out using a pressure fluid, particularly preferred by a pressurized hydraulic fluid, with which one of the Workpiece top facing away from the die.

In a further development, the die according to the invention can also be more flexible Stamps are used to advance the workpiece, especially through Stretch forming. The matrix elements become stamp elements. Preferably, the die elements with the workpiece clamped over them actively extended individually to the final shape of the stamp formed and this Workpiece pre-stretched. After the stretching is finished, the workpiece is through Applying a compressive force to the top of the workpiece, for which the Stamp elements are switched to compliance and again the inventive, resilient into the final form is formed.

If the tool is a flexible stamp that is relative to each other has axially movable stamp elements during the shaping, so this becomes axial  movable stamp element according to the invention by applying fluid pressure extended. A preferably hydraulic extension, but basically also a pneumatically operated extension, has a mechanical or electric drive on the advantage that larger forming forces can be achieved and the Driving force can be applied directly to the respective stamp element and not only via mechanical transmission elements, such as gears and Couplings. If the flexible tool forms a stamp, it is preferably around a stamp for hydroforming, in which a back pressure is generated hydraulically by means of a membrane or without a membrane.

If the movements of the form elements, in particular the movements of the Matrix elements that can be controlled individually or in sections by forming groups form elements arranged on the edges of the tool can function a jig, d. H. the function of the commonly used Hold down, take over and fix the workpiece. This can be achieved be that with these form elements with a correspondingly high Resilience is worked. On a separate jig to be dispensed with. The local surface pressure that the workpiece has on the individual Experienced shaped elements, but advantageously not only due to the invention on the edges of the tool, but over the entire contact surface of the Tool used for targeted control of the material flow in the workpiece by adding resistance to each of the die elements or the Driving force for each of the stamp elements individually or in groups predefined in different sizes or individually or in groups is changeable.

The tool according to the invention can be simple in terms of its final shape Be designed tool, d. H. the final shape of the tool is not in this case variable. The tool in this embodiment is flexible only with respect to  its compliance from an initial form to the non-variable final form. The final form that cannot be varied can be obtained in that the shaped elements are axial be driven on block, for example by forming the shaped elements in different lengths or by inserting different thicknesses Between pieces.

Preferably, however, the final shape of the tool, i. H. the final form of plant surface formed by the tool, changeable to different shaped parts To be able to create shape. The tool according to the invention is in this sense doubly flexible, namely on the one hand through the resilience to a final shape and on the other hand through the changeability of this final form. The final shape of the tool, d. H. the end position of the feature or the end positions of the several According to the invention movable form elements during the forming be advantageously changed in the forming device. For this, the axial Position of preferably each individual shaped element via a position measuring system, for example capacitive, magnetic or opto-electronic, determined and via a Control with a predetermined, individual stopping point for each one Form element compared. A shape element has its specified breakpoint reached, this form element is fixed by an actuator from the controller. If the resistance force or the driving force is a fluid pressure force, this can Actuator are formed by a controllable valve. It is enough here basically that the controllable valve from flow to lock and vice versa can be controlled. The controllable valve can advantageously be a Flow control valve, or it can be in addition to a shut-off valve Flow control valve can be provided in order to be able to change the fluid damping force.

However, it is preferred to set the pressure independently of the fluid pressure force Damping or the drive by a dedicated actuator pro Form element causes. Fixing the at least one movable molding element  is preferably effected by means of a clamping sleeve, through which the Form element is passed. Preferably, each of the axially movable Shape elements individually by means of at least one shape element in question surrounding ferrule in a desired position with respect to the Direction of movement of the relevant element is fixed. The Clamping sleeve has a radially flexible and preferably in the axial direction stable sleeve jacket, which is pressed against the molded element by force becomes. Preferably, the sleeve shell is covered with an outer surface Hydraulic fluid pressurized and thereby pressed against the shaped element. The radial compliance is preferably due to axial weaknesses in the Sleeve casing reached.

The size of the resistive force in the case of a die and the driving force in the case a stamp is preferably changeable to the travel speed of the Being able to change form elements, for example depending on the Workpieces to be formed and / or depending on the degree of deformation.

The resistance against which the form elements of a die in the Giving retracted and the driving force by which the form elements of a Extended stamp can be the same size for all form elements. Also in In this case, the workpiece is constantly at least one during the forming yielding or extending molded element or preferably the plurality yielding or extending form elements and is created in this way deformed in a controlled manner through extensive support.

In the case of a die, if the resistance force is a fluid damping force, then a particularly simple forming device can be obtained in that the movable die elements during forming into a fluid-filled common pressure vessel are driven in and the fluid underneath  Suppress generation of damping force against flow resistance. The Flow resistance can easily be created by forming a fluid outlet a specific flow cross-section, orifice or simple throttle or more preferably be adjusted by a controllable flow control valve. In a Further development is a separate one for each movable die element Damping fluid filled cylinder provided, the damping force as described above is generated individually for each of these cylinders. Analogous this also applies to the generation of those formed by a fluid pressure force Driving force in the case of the formation of the flexible tool as a stamp.

In preferred embodiments, heads of the shaped elements with which the Press the form elements against the workpiece, tangential to the formed one Contact surface connected elastically. The connection is preferred formed by an elastic membrane with which the heads of the shaped elements such are connected to each other, which is always a very uniform, continually arching contact surface is offered. This can also improve the uniformity of the elastic contact surface be that the contact surface between the formed by the shaped elements Support points directed against the workpiece with a fluid pressure force, preferably a hydraulic fluid pressure force, and thereby additionally supported becomes. The formation of voids between the workpiece and the contact surface can be minimized or completely prevented if this is desired.

Preferred embodiments of the invention are described below with reference to Figures explained. The features disclosed in the exemplary embodiments form in the disclosed combinations and each individually the subject matter of the claims.

Show it:

Fig. 1 shows a forming device with a flexible tool before the forming of a workpiece,

Fig. 2 shows the forming system of Fig. 1 after the forming of the workpiece,

Fig. 3, the forming device to a fluid circuit,

Fig. 4 is a tool rack and a fluid supply for a clamping device,

Fig. 5 shows the device with a receiving device for a pre-stretching of the workpiece,

Fig. 6 shows the device according to the pre-stretching,

Fig. 7 is a clamping sleeve,

Fig. 8, the clamping sleeve in the tool rack,

Fig. 9, the tool frame,

Fig. 10, the shaped elements of the tool,

Fig. 11 alternative embodiments of shaped element heads and

Fig. 12 shows a star-shaped shaped element head.

Fig. 1 shows a forming device for deep-drawing, depths or only bending a panel 10. The reshaping is effected hydraulically by pressing or placing the workpiece 10 on a die which has a plurality n of rod-shaped, individually displaceable die elements 11 . The die can also form a flexible stamp and is therefore neutral called a tool.

The tool is formed by a tool frame 4 and the axially movable in the frame 4 forming elements. 11 The frame 4 is shown in Fig. 9 without shaped elements. The n shaped elements 11 are shown in FIG. 10 in accordance with their arrangement in the frame 4 , but without the frame. The frame 4 is formed by a fixed plate with vertical through holes in a regular arrangement next to each other. A receiving sleeve 7 is inserted in each of the through bores 5 . The shaped elements 11 are closely guided in the receiving sleeves 7 . Instead of inserted sleeves, the shaped elements 11 could also simply be slid directly through the frame body, as is shown in simplified form in FIG. 1.

Each of the shaped elements 11 has a head 15 , a guide rod 12 and a support guide region 13 arranged between them. The head 15 forms a contact surface for the workpiece 10 at its free end. All of the shaped elements 11 together form the contact surface of the tool, but an elastic membrane 2 is still arranged between the tool contact surface and the workpiece. In the area of its guide rod 12 , the individual shaped element 11 is axially slidably guided in the frame 4 . The support guide area 13 is thickened relative to the guide rod 12 and shaped in such a way that the support guide areas 13 of adjacent shaped elements 11 slide against one another during axial movements of the shaped elements 11 and in this way a guide for the shaped elements 11 in addition to the sliding guide of the guide bars 12 in the guide sleeves 6 is achieved. The heads 15 of the shaped elements 11 are movably mounted, so that the individual heads 15 and thus the entire contact surface of the tool automatically adapt to the shape of the workpiece 10 that changes during the forming. The movable mounting of each of the heads 15 takes place by means of a ball joint, which is formed by a ball body 14 connected to the support guide region 13 and a spherical cap on the side of the head 15 .

A pressure vessel 1 is divided into two parts, a lower and an upper pressure chamber. The frame 4 is clamped between two parts of the pressure vessel 1 or inserted into the one-piece pressure vessel 1 and separates the two pressure spaces from one another. A circumferential flange 3 is formed on the free upper edge of the pressure container 1 . Finally, the elastic membrane 2 covers the heads 15 of the shaped elements 11. The workpiece 10 lies flat on the membrane 2 . In principle, however, the workpiece 10 could lie directly on the heads 15 of the shaped elements 11 without the membrane 2 .

The forming force is applied to the workpiece 10 by means of a pressure fluid, preferably a hydraulic fluid. For this purpose, a sufficient fluid pressure is built up in a pressure chamber 20 over the entire top of the workpiece. To form the pressure chamber 20 , a further pressure vessel 17 is placed on the pressure vessel 1 and is pressed against the flange 3 of the pressure vessel 1 by means of hydraulic cylinders 22 of a pressing device 21 . In this way, the pressure chamber 20 delimited by the pressure container 17 is formed over the entire top of the workpiece. In the exemplary embodiment, the pressure chamber 20 is closed in a fluid-tight manner on its side facing the workpiece 10 by an elastic membrane 19 . The membrane 19 lies directly on the workpiece 10 when the two pressure vessels 1 and 17 are placed one on top of the other. In this way, the workpiece 10 is packed on its top and on its underside between the two elastic membranes 19 and 2 . The pressure chamber 20 is thus formed in the form of a bubble which can be expanded by pressure. Although less preferred, the pressure chamber 20 could, however, also be formed without the membrane 19 , namely if a tight seal of the pressure chamber 20 is otherwise ensured. The pressure fluid is conveyed into the pressure chamber 20 by one or more fluid feeds 18 incorporated in the pressure container 17 , for example by means of a pump and / or from a pressure reservoir.

In Fig. 1, the mold elements 11 assume their starting position, in which all the mold elements 11 have moved against the underside of the workpiece. In the case of a flat workpiece 10 , as in the exemplary embodiment, all of the shaped elements 11 are at the same height with respect to the underside of the workpiece. However, the heads 15 of the shaped elements 11 can also assume different heights in other starting positions immediately before the pressure is applied to the upper side of the workpiece.

Fig. 2 shows the forming apparatus after the forming of the workpiece 10. The shaped elements 11 assume their end positions. In the end positions, the contact surface parts formed by the shaped elements 11 together form the final shape, ie the counter shape, for the workpiece 10 pressed on by the pressure force P. An even more uniform contact surface is obtained through the membrane 2 .

The lower pressure chamber of the pressure container 1 is completely filled with a damping fluid, preferably a hydraulic fluid. The matrix frame 4 with the shaped elements 11 forms an at least largely tight seal for the lower pressure chamber of the pressure container 1 . The space above the die frame 4 can also be filled with the damping fluid. Preferably, as in the exemplary embodiment, this space is actually filled with the damping fluid, as a result of which a particularly uniformly curved contact surface and additionally lubrication for the support guide regions 13 sliding against one another is obtained. It would also be possible to generate the damping primarily or only in the upper pressure chamber. In this case, the shaped elements 11 would serve for fixing in the desired end position or in intermediate positions in the case of a deformation carried out in stages. However, the shaped elements 11 preferably form piston rods with pistons, alone in order to facilitate returning to a starting position. A free pressure equalization can take place between the two spaces separated by the die frame 4 , but this is not absolutely necessary.

The deformation of the workpiece 10 and the resulting yielding of the shaped elements 11 in the axial direction into the lower pressure space increases the pressure in this fluid space in accordance with the ratio of the retracting volume of the shaped elements 11 to the volume of the fluid space. As a result, a damping force D which counteracts the compressive force P in the axial direction of each shaped element 11 acts on the shaped elements 11. The guide rods 12 form piston rods with pistons. The pressure chamber with the damping fluid enclosed by the lower part of the pressure container 1 and the die frame 4 is provided with an outlet through which the damping fluid can flow out at a specific flow rate. When a hydraulic fluid is used as the damping fluid, the damping force D can be set precisely as a function of the pressure force P. The upper pressure space is also reduced by the shaping of the workpiece 10 , so that a fluid damping pressure prevails over the entire surface of the membrane 2 on the underside of the elastic membrane 2 . In the case of free pressure equalization between the two pressure spaces, the fluid pressure D also prevails in the upper pressure space.

The elastic membrane 2 is integrally connected to the heads 15 , for example by gluing or by vulcanization. In principle, the membrane 2 can also be mechanically connected to the heads 15 , although this is less preferred. The heads 15 are elastically connected to one another by the membrane 2 tangentially to the contact surface formed. Although less preferred, the elastic connection can only be established by pressing the workpiece 10 . However, a firm connection to the heads 15 prevents the membrane 2 from snapping back when the pressure in the pressure chamber 20 is reduced.

In Fig. 3 the forming device is shown together with a fluid guide system immediately before the assembly of the two pressure vessels 1 and 17 . The shaped elements 11 are in the starting position shown in FIG. 1. Fig. 3 shows on a discharge side of the damping fluid provided in fluidic positions which they occupy during the forming process. Furthermore, a fluid guide system for fixing the shaped elements 11 in end or intermediate positions is shown.

The pressure in the pressure chamber 20 required for the forming is generated by actuating a pressure intensifier 24 . A drive pressure is generated on one side of the pressure booster 24 by means of a motor-driven pump 23 . A double piston of the pressure booster 24 is displaced by the drive pressure, as a result of which the pressure on the output side of the pressure booster 24 , which is connected to the pressure chamber 20 , is increased in a closed fluid system. This fluid system comprises the driven side of the double piston 24 , the pressure chamber 20 , a fluid reservoir 25 formed in a pressure container and the corresponding connecting lines, as shown schematically in FIG. 3. The pressure in the pressure chamber 20 is measured by means of a pressure sensor 26 . A motor M for the pump 23 is driven in a controlled manner in accordance with the measurement signal of the pressure sensor 26 in order to build up and maintain a specific pressure in the pressure chamber 20 or to run a predetermined pressure profile.

The lower pressure chamber and the upper pressure chamber in the pressure container 1 are completely filled with the damping fluid and vented. The pressure in the lower pressure chamber is recorded with a pressure sensor 45 . The output signal of the pressure sensor 45 is used to control or only to monitor the outflow of the damping fluid. On the discharge side, the damping fluid is discharged into a discharge manifold 42 through a discharge line 37 connected to the outlet. A controllable shut-off valve 38 and a flow control valve 41 are connected in series in the discharge line 37 . The shut-off valve 38 is opened during the forming. The flow rate of the outflowing damping fluid and thus also the damping force D generated in the lower fluid space of the pressure container 1 are adjusted by means of the flow control valve 41 . Furthermore, a reservoir 43 is formed in a pressure container in the discharge line 37 and a pressure limiting valve 44 is arranged. The damping fluid flows out of the upper fluid space in the pressure container 1 through a discharge line 39 . The discharge line 39 opens into the discharge line 37 behind the shut-off valve 38 and before the flow control valve 41 and preferably also before a flow sensor 46 . A current sensor 47 and a controllable shut-off valve 40 are arranged in the discharge line 39 . The outflow rates from both fluid spaces in the pressure container 1 are determined with the current sensor 46 and the current sensor 47 arranged in the discharge line 37 .

Instead of moving the shaped elements 11 collectively into a common pressure container, a pressure container can be provided individually for each of the shaped elements 11. In this case, a piston-cylinder system is provided for each of the n shaped elements 11 instead of the lower pressure chamber. The pressure in the upper pressure chamber is preferably less than the pressures of the piston-cylinder systems in order to be able to individually determine the travel speed of the shaped elements. The free ends of the shaped elements 11 facing away from the heads 15 are each designed as pistons, each of which is slidably guided in its own pressure cylinder and each of which generates an individual damping force Dn in the individual cylinders as a result of the pressure force P in the pressure chamber 20 . In this case, a discharge line 37 with a shut-off valve 38 and a flow control valve 41 and preferably also a flow sensor 46 is provided individually for each of the shaped elements 11 or the associated pressure cylinders. By generating the damping forces Dn for each of the molded elements 11 independently of the other molded elements 11, the speed of the axial movement of each individual molded element 11 can be individually adjusted by appropriate control of the individual flow control valves 41 and, if necessary, also changed in a targeted manner during the forming. In this way, the material flow in the workpiece 10 can be controlled particularly precisely during the entire forming process. The position along the travel path is determined for each of the shaped elements 11 with the aid of corresponding sensors and compared in a control with the end position to be approached. As soon as the end position of a molded element 11 has been determined, the shut-off valve 38 provided in the discharge line for this molded element 11 is switched over by the control to locks. When using a hydraulic fluid as a damping fluid, the relevant molding element 11 is already fixed directly in the predetermined end position.

A pressure intensifier 31 for generating a clamping pressure for the shaped elements 11 is provided in the fluid guide system for fixing the shaped elements. A drive side of the pressure booster 31 is connected to a pressure line 30 . The output side of the pressure booster 31 is connected to the tool frame 4 . The pressure fluid is fed via a feed line 34 per shaped element 11 into the die frame 4 directly up to each of the receiving sleeves 7 . A controllable shut-off valve 33 is arranged in each of the feed lines 34 . During the forming process, the shut-off valves 33 are blocked until the molded elements 11 are individually fixed. To fix the shaped elements 11 in the position desired in relation to the direction of movement, the shut-off valve 33 of the shaped element 11 to be fixed is opened, thereby causing the force-fitting clamping of the relevant shaped element 11, as will be explained below with reference to FIGS. 7 and 8. A fluid reservoir 32 is also formed in a pressure container on the supply side for the pressurized fluid. A vent line 35 is also provided in the tool frame 4 for each of the shaped elements 11, and a check valve 36 is provided in each vent line 35 .

In FIG. 4, the feeding of the pressurized fluid at individual clamping capacity of the mold members 11 is shown. An individual feed line 34 with a controllable shut-off means 33 is guided into the tool frame 4 for each of the shaped elements 11.

FIGS. 5 and 6 show how the flexible tool can also be used as a flexible stamp. The usability as a stamp allows the workpiece 10 to be pre-stretched before deep drawing or deep drawing. Pre-consolidation is obtained by pre-stretching. By pre-stretching, the strength of weakly arched molded parts can be increased compared to deep drawing or deep drawing. Likewise, the flexible punch can also be used with advantage as a pure stretching tool or even only as a bending tool, although a tool which can form both a die and a punch represents a preferred further development of the pure die and the pure punch.

For pre-stretching, the workpiece 10 is clamped on the elastic membrane 2 in a clamping device. The clamping device is formed by laterally arranged, movable clamping jaws 8 and hydraulic cylinders 9 which serve to clamp the clamping jaws 8 .

Fig. 5 shows the mold elements 11 in the initial position before the pre-stretching. In this starting position, the workpiece 10 is clamped close to the plasticity limit by the clamping device 8 , 9 . For the combined forming, namely pre-stretching with subsequent deepening or deep-drawing, the starting position of the shaped elements 11 is selected such that the pre-stretching elements 11 are first pushed out against the underside of the workpiece and then for deepening or deep-drawing again, as already described, via that in FIG. 5 shown starting position can also be retracted and retracted.

The later damping fluid is preferably also used as pressure fluid for extending the shaped elements 11. To extend the mold elements 11, the lower fluid space in the pressure container 1 , or the individual pressure containers for each of the mold elements 11, are pressurized from a supply side for the damping fluid. The supply side for the pressurized fluid for extending is the same as for filling the pressure vessel or containers for generating the damping force when retracting. The fluid discharge side for the damping fluid is advantageously taken over identically. However, the shut-off valves 38 and 40 are in their blocking states on the discharge side when they are extended. When extending the shaped elements 11, the same distance measuring system is used as when entering.

As soon as the control has determined with the aid of the position measuring system that one of the shaped elements 11 has reached its desired extended end position, the shut-off valve 33 in the feed line 34 of the clamping device for this shaped element 11 is switched to flow and thereby instantaneously causes the relevant shaped element 11 to be clamped. As soon as all of the shaped elements 11 have reached their desired extended end positions and the pre-stretching has thus ended, the pressure chamber 20 can be pressurized as described and the forming can be initiated in the opposite direction. At the beginning of this subsequent forming, the shaped elements 11 assume the starting positions shown in FIG. 6. As already described, they are moved from these starting positions, for example into the retracted end positions shown in FIG. 2.

FIGS. 7 and 8 show a preferred clamping means, with which each of the mold members 11 at both movability in a collective pressure container may also be fixed at movability in individual pressure containers in any desired position with respect to its direction of movement independently of the other mold elements 11 as. For this purpose, 7 clamping sleeves 6 are inserted into the receiving sleeves. Each of the clamping sleeves 6 is received in a receiving sleeve 7 with a fixed axial and radial seat. The installation situation of a single clamping sleeve 6 in the tool frame 4 is shown in FIG. 8.

During assembly, a receptacle sleeve 7 is first inserted into a circular cylindrical through hole in the frame 4 . The receiving sleeves 7 are fixed radially and axially in the frame 4 . A clamping sleeve is then inserted 6 to against a formed in the receiving sleeve flange 7 in each of the receptacles. 7 Finally, a locking sleeve into each of the receptacles 7 is preferably screwed used 7 a. Each of the clamps 6 is mounted between the radially inwardly projecting flange of its receiving sleeve 7 and the closure sleeve 7 axially with a tight fit. Preferably, each of the clamping sleeves 6 at its two end faces a radially outwardly projecting flange which provides already for a fixed radial seat of the clamping sleeve 6 in its receiving sleeve. 7 The clamping sleeve 6 is essentially formed by a radially flexible, axially rigid sleeve jacket. In the assembled state, an annular gap remains between this radially flexible sleeve jacket and the surrounding receiving sleeve 7 , which is sealed in the axial direction by sealing rings 7 b. At least one sealing ring 7 is b in a groove in the flange of the receiving sleeve 7 and at least one further seal ring 7 is inserted in a groove of the closure sleeve 7 a b. These at least two sealing rings 7 b seal the annular gap around the sleeve jacket of the clamping sleeve 6 against the guide rod 12 of the molded element guided by the respective clamping sleeve 6 . The radial flexibility of the clamping sleeve 6 is obtained by axially weakening the sleeve shell, for example by means of axial recesses or slots. If the sleeve jacket of the clamping sleeve 6 is broken, the sleeve jacket is surrounded by a closed cover sleeve.

Pressure fluid is individually supplied through the fluid supply lines 37 into the annular gaps formed between the clamping sleeves 6 and the receiving sleeves 7 . Each of the annular gaps is vented via its individual ventilation line 35 . The check valves 36 ( FIG. 4) arranged in the vent lines 35 close after a predetermined pressure has been reached in the respective annular gap. The check valves 36 close before a fluid pressure sufficient to generate a clamping force is built up in the annular gaps. After venting the annular gaps and closing the check valves 36 , the shut-off valves 33 in the feed lines 34 ( FIG. 4) are closed before a pressure sufficient for clamping is reached. In this state, the guide rods 12 of the shaped elements 11 can be moved free of the clamping sleeves 6 and through the receiving sleeves 7 and their sealing sleeves 7 a closely slidably. On the supply side for the pressure fluid, ie upstream of the shut-off valves 33 , a fluid pressure sufficient to clamp the guide rods 12 is built up and maintained during the forming process. As soon as one of the shaped elements 11 has reached its end position for the respective shaping process, or an intermediate position during shaping in several stages, the associated shut-off valve 33 is opened and the annular gap around the clamping sleeve 6 is pressurized. The clamping sleeve 6 widens radially inwards due to the external hydraulic pressure. The shape element 11 in question is hereby instantaneously clamped and fixed in the position just reached.

In Figs. 11 and 12 alternative embodiments of the mold member heads 15 are shown. The heads 15 are preferably resilient in the direction of movement of the shaped elements 11. The elastic compliance can be achieved, for example, by the heads 15 themselves being formed from an elastomeric material. However, the elasticity can also be obtained by appropriately shaping the heads 15 , for which the head 15 shown in FIG. 12 provides an example. The elastic flexibility in the direction of movement of the molded element 11 can also be achieved by a combination of material elasticity and design elasticity. The head 15 of FIG. 12 has a full central region in plan view from the workpiece and arms which protrude radially from it at equal angular intervals and which become thinner towards the outside.

With the tool according to the invention, the workpiece 10 is supported at all times over the entire surface or at least almost over the entire surface. The shaped elements 11, each of which is individually resiliently supported against a collective or individual damping force and / or can be extended by a collective or individual fluid pressure, form a support surface adapted to the shape of the workpiece at any moment. It is also conceivable, however, to let individual mold elements 11 of a die yield almost without resistance or with a much lower resistance than the neighboring mold elements 11 or even to produce local cavities into which the workpiece 10 then preferably deforms. On the other hand, the formation of local cavities can be minimized or completely prevented by an elastic connection of the shaped element heads and the application of a damping pressure. It is also advantageous that a flexible stamp can be formed very easily from the tool according to the invention. The invention was described using the exemplary embodiments only in the preferred interaction with a pressure fluid for generating the pressure force P. However, the flexible die can advantageously also be used in conjunction with a stamp that cannot be changed during the forming process or a flexible stamp of the type described as a counterpart for generating the forming force.

LIST OF REFERENCE NUMBERS

1

pressure vessel

2

Pick-up device, clamping device, elastic membrane

3

flange

4

Matrizengestell

5

Through Hole

6

collet

7

receiving sleeve

7

a sealing sleeve

8th

Clamping device, jaw

9

Clamping device, hydraulic cylinder

10

workpiece

11

Molded element, clamping device

12

Guide rod, piston rod

13

Supporting guide area

14

Bullet

15

head

16

locknut

17

pressure vessel

18

fluid supply

19

elastic membrane

20

pressure chamber

21

pressing device

22

hydraulic cylinders

23

pump

24

Pressure intensifier

25

reservoir

26

pressure sensor

27

-

28

-

29

-

30

pressure line

31

Pressure intensifier

32

reservoir

33

shut-off valve

34

feed

35

vent line

36

check valve

37

discharge

38

shut-off valve

39

discharge

40

shut-off valve

41

Flow control valve

42

Abführsammelleitung

43

reservoir

44

Pressure relief valve

45

pressure sensor

46

current sensor

47

current sensor
D collective damping force
Dn damping force individually per molded element
F collective driving force
Fn driving force individually per shaped element
P pressure force

Claims (17)

1. Flexible tool for forming a contact surface for a workpiece when the workpiece is formed, the tool being a die, the tool comprising:

• a) a tool frame ( 4 ),
• b) a first shaped element (11) which forms part of the contact surface,
• c) and a second shaped element (11), which forms a second part of the contact surface and is axially movable relative to the first shaped element (11), namely in a direction perpendicular to the contact surface, in the tool frame ( 4 ),

characterized in that

• a) the second shaped element (11) is axially resiliently mounted such that it can be moved axially against a resistive force (D; Dn) during the shaping from an initial position into a fixed end position.

2. Flexible tool according to claim 1, characterized in that the size the resistance (D; Dn) is changeable. 3. Flexible tool according to one of the preceding claims, characterized characterized in that the resistance force (D; Dn) is a fluid damping force.   4. Flexible tool according to the preceding claim, characterized in that the second shaped element (11) displaces a damping fluid from a pressure container ( 1 ) against a flow resistance during an axial yielding. 5. Flexible tool according to the preceding claim, characterized in that a flow control valve ( 41 ) forms the flow resistance. 6. Flexible tool according to one of the preceding claims, characterized characterized in that the second shaped element (11) with a drive device coupled and active in another end position by means of the drive device is movable so that a flexible stamp is formed by the tool can be. 7. Flexible tool for forming a contact surface for a workpiece when the workpiece is formed, the tool being a stamp, the tool comprising:

• a) a tool frame ( 4 ),
• b) a first shaped element (11) which forms part of the contact surface,
• c) and a second shaped element (11), which forms a second part of the contact surface and is axially movable relative to the first shaped element (11), namely in a direction perpendicular to the contact surface, in the tool frame ( 4 ),

characterized in that

• a) the second molded element (11) forms a piston rod ( 12 ) with a piston which can be acted upon with a fluid pressure in a pressure container ( 1 ) and the fluid pressure is sufficient to shape the workpiece by axially extending the molded element (11).

8. Flexible tool according to one of the preceding claims, characterized in that
the second shaped element (11) extends through a clamping sleeve ( 6 ) and the second shaped element (11) can be non-positively fixed in relation to the axial direction by means of the clamping sleeve ( 6 ),
a radial clamping force of the clamping sleeve ( 6 ) effecting the frictional connection is preferably generated by pressurizing a jacket of the clamping sleeve ( 6 ) with a hydraulic fluid. 9. Flexible tool according to one of the preceding claims, characterized in that a head ( 15 ) of the second molded element (11), with which the second molded element (11) presses against the workpiece, is elastically flexible in the direction of movement of the second molded element (11) , 10. Flexible tool according to one of the preceding claims, characterized in that
the die elements ( 11 ) have heads ( 15 ) with which they press against the workpiece,
and the heads ( 15 ) are connected to one another elastically tangentially to the contact surface. 11. Flexible tool according to one of the preceding claims, characterized in that
the contact surface of the tool is formed by a plurality of shaped elements (11)
and several of the shaped elements (11), preferably all shaped elements (11) of the tool, are second shaped elements (11). 12. Forming device for forming a workpiece by means of an active fluid, the device comprising:

• a) a receiving or clamping device ( 2 , 11 ; 8 , 9 ) for the workpiece ( 10 ),
• b) a pressure chamber ( 20 ) for applying a pressure force (P) to an upper side of the workpiece ( 10 ),
• c) and a flexible tool for forming a contact surface for the workpiece ( 10 )
  • 1. a tool frame ( 4 ),
  • 2. a first shaped element (11) which forms a first part of the contact surface,
  • 3. a second shaped element (11), which forms a second part of the contact surface and is axially movable relative to the first shaped element (11), namely in a direction perpendicular to the contact surface, in the die frame ( 4 ),

characterized in that

• a) the second shaped element (11) is axially resiliently mounted such that it can be moved axially during the shaping from an initial position into a fixed deformation against a resistance force (D; Dn).

13. Forming device according to the preceding claim, characterized characterized in that the second shaped element (11) from the pressure force (P) is moved against a fluid damping force (D; Dn). 14. Method for forming a workpiece, in which
the workpiece ( 10 ) is formed by applying a pressure force (P) to an upper side of the workpiece and pressed with a lower side of the workpiece against a flexible tool divided into several shaped elements (11) and
thereby being transformed from an initial shape into a final shape formed by the shaped elements (11),
characterized in that
the shaped elements (11) are moved from initial positions which they assume before the forming, relative to one another into end positions in which they form the final form, and support the workpiece ( 10 ) against the compressive force (P) during the forming. 15. The method according to the preceding claim, characterized in that the shaped elements (11) form the initial shape in the starting positions and rest on the underside of the workpiece. 16. The method according to any one of the preceding claims, characterized characterized in that the shaped elements (11) by the pressure force (P) and each against a fluid damping force (D; Dn) are moved into the end positions. 17. The method according to any one of the preceding claims, characterized in that the workpiece ( 10 ) is pre-stretched in a direction opposite to the shaping before the shaping, in that the shaped elements (11) are actively extended to a bottom pre-stretch shape against the underside of the workpiece.