Abstract:
Aspects of the present invention relate to an automated handling device for handling a forged piece during a forging press. A method in accordance with an implementation of the present invention involves positioning the workpiece between two tools in a predetermined shaping position in at least one working region of a shaping machine (positioning step), particularly one that operates percussively, moving the tools of the shaping machine relative to one another and shaping the workpiece between the tools during at least one shaping step, holding the workpiece in its shaping position by at least two handling devices during each shaping step, and thus also when the tool(s) strike the workpiece, and automatically controlling or regulating by mutual coordination the motions and positions of at least two handling devices by use of at least one control device.

Description:
This application is a 371 of PCT/EP04/05782, filed May 28, 2004. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a method and a device for shaping a workpiece. 
   2. Background and Related Art 
   Shaping machines, especially of the percussive type, such as hammers, crank presses, and screw presses, in particular flywheel screw presses, are known for industrial forging of workpieces. Percussive shaping machines comprise a working region in which two tools are movable, generally in a straight line, relative to one another. The workpiece is positioned between the two tools, and is then shaped by the impact force or impact energy from the striking of the tools on the workpiece and the resulting shaping energy. 
   According to VDI-Lexikon “Produktionstechnik Verfahrenstechnik” [Manufacturing Process Engineering], Prof. Dr. Hiersig, Publisher, VDI-Verlag, 1995, pages 1107-1113, forging hammers may be subdivided into anvil hammers—which in turn are subdivided into drop hammers and double-acting hammers—and counterblow hammers. An anvil hammer comprises an anvil (or support) as a tool that is stationary with respect to the workpiece, and a striking hammer, or hammer for short, as a tool that is movable, generally vertically, with respect to the workpiece and to the anvil. A counterblow hammer comprises two striking hammers that are movable, vertically or also horizontally, with respect to one another and relative to the base or the hammer frame. The drives for the hammers of forging hammers are generally hydraulic or pneumatic. In the actual shaping or work procedure, both the hammer frame and the hammer drives of a forging hammer are relieved of the shaping force so as not to overload the forging hammer. For screw presses, the workpiece that is moved is generally referred to as a tappet. The tappet is moved by a spindle in a straight line toward the stationary tool. The drive of the spindle, and thus of the tappet, is provided by a drive motor and/or a flywheel as an energy store (VDI-Lexikon, see above). 
   The shaping pressure force and the shaping temperature are dependent on the material of which the workpiece is composed, as well as the requirements for dimensional accuracy and surface quality. In principle, forgeable workpieces include all ductile metals and metal alloys, and therefore also ferrous materials such as steels, as well as nonferrous metals such as aluminum, titanium, copper, nickel, and alloys thereof. The temperatures arising during forging may be in the range of room temperature for so-called cold shaping, between 550° C. and 750° C. for warm shaping, and above 900° C. for so-called hot shaping. The shaping temperature is also typically set in a temperature range in which the material is shapeable or flowable and in which recovery and recrystallization processes in the material can take place, and also in which undesired phase transformations are avoided. 
   For automatic handling of workpieces during pressing or forging, the use of handling devices such as manipulators and industrial robots is known from VDI-Lexikon “Produktionstechnik Verfahrenstechnik”, Prof. Dr. Hiersig, Publisher, VDI-Verlag, 1995, pages 848, 849, and 1214. Such handling devices have grippers for grasping and temporarily holding workpieces, and insert the workpieces into or remove them from the forging machine. Manipulators are manually controlled motion devices which as a rule have distinct, process-specific controls or programs. Industrial robots are universally applicable automatic motion devices with a sufficient number of degrees of freedom, implemented by a corresponding number (5 to 6) axes of motion, and a freely programmable control for achieving practically any given motion trajectories of the workpiece within an area which the industrial robot can traverse or reach. 
   One problem with the use of such handling devices is the high impact forces from a percussive shaping machine, which during the shaping impact can impose significant stress and cause damage to the handling device when the handling device is holding the workpiece which is struck by the hammer or tappet. 
   BRIEF SUMMARY OF THE INVENTION 
   The object of the invention, therefore, is to propose a method and a device for shaping workpieces by which the referenced disadvantages may be at least partially overcome. It is an also an object to enable rapid setup of the machine, in particular after tool replacement or tool remachining, while at the same time ensuring a high degree of process reliability. 
   To solve the problem of the reaction to the impact of the hammer or tappet of the shaping machine, DE 42 20 796 A1 and DE 100 60 709 A1 have proposed handling devices which can be flexibly positioned during the impact to damp the impact forces and vibrations transmitted from the workpiece to the drive, and which can be rigidly positioned during transport of the workpiece. 
   DE 42 20 796 A1 discloses a handling device for holding a forged piece during a forging process, in which a traveling mechanism carries a gripping mechanism via a sleeve, the gripping mechanism having vise-grip pincers that grip the forged piece during the forging process. The sleeve may be optionally brought into a flexible state and a rigid state by hydraulic means. 
   A handling device, designed as a manipulator or robot, for handling a forged piece during a forging press is known from DE 100 60 709 A, having a gripping jaw and a gripping arm which supports the gripping jaw. The gripping arm is connected via a flexible block piece, made of an elastically deformable material, to an arm region which by means of a first electromotor may be pivoted up and down, and by means of a second electromotor, raised and lowered. These two motions of the arm region are synchronized by a control device. Due to the flexibility of the block piece, the front region of the gripper comprising the gripping arm and gripping jaw is pivotable in the block piece with respect to the rear region comprising the arm region and the drive motors, as a type of articulating joint. If the gripper now places a forged workpiece on a forging die of a forging hammer, and the striking tool strikes the workpiece from above, vibrations or impacts thus produced may become damped and absorbed in the elastic block piece, thereby relieving the load on the drives. For handling the workpiece before or after the actual shaping process in the forging hammer, the elastic block piece is bridged by a rigid control rod which produces a rigid connection between the gripper arm and the arm region via the block piece. The rigid control rod is fixed in place when the front gripper arm and the rear arm region are in the parallel position, and when the workpiece is lying on the forging die of the forging hammer the rigid control rod can be released by raising the rear arm region. 
   Workpieces that tend to buckle, in particular elongated workpieces, are problematic for automated forging processes according to the prior art. Because of their motor sensitivity and experience, during the forging process human operators are able to compensate for or prevent buckling of the workpiece by handling, although they are holding the workpiece only on one side. In contrast, the known handling devices do not permit automated forging in which the workpiece can reliably be prevented from buckling. 
   Lastly, there is an additional problem in the handling of forged parts, in that the forged parts may sometimes have significant deviations in shape, particularly at the ends which are grasped by the handling devices, due to manufacturing or processing tolerances in previous shaping or reshaping steps. For this reason, significant deviations in the position of the forged part relative to the handling device, and thus relative to the tool of the shaping machine as well, may result during gripping with the known automatic gripping mechanisms, which may lead to a high reject rate and, in extreme cases, even to damage of the tools. 
   It would now be possible to detect the position of the workpiece in the tool of the shaping machine, for example by image analysis, and to correspondingly control the handling device to correct a deviation in the position of the workpiece from a target position relative to the tool. However, this is quite costly, and in practice functioning systems are not yet available. 
   Because of the referenced problems, automated handling of workpieces in forging processes with percussive shaping machines has not yet achieved widespread acceptance in actual practice. Instead, in practice the workpiece is still manually held in the forging hammer using a gripping tool, since appropriately trained operators control the correct handling of the workpiece when it is struck by the hammer along with the striking tool. 
   The object of the present invention is to partially alleviate or totally avoid the aforementioned problems of the prior art. This object is achieved according to the invention by a method having the features of claim  1 , and a device having the features of claim  40 . 
   The method according to the invention is suitable for shaping, in particular forging, at least one workpiece, and specifies and comprises the following process steps:
     a) Positioning the workpiece between two tools in a predetermined or predeterminable shaping position in at least one working region of a shaping machine (positioning step), particularly one that operates percussively,   b) Moving the tools of the shaping machine relative to one another and shaping the workpiece between the tools during at least one shaping step,   c) Holding the workpiece in its shaping position by at least two handling devices during each shaping step, and thus also when the tool(s) strike the workpiece, and   d) Automatically controlling or regulating by mutual coordination the motions and positions of at least two handling devices by use of at least one control device.   

   The device according to the invention is suitable for shaping at least one workpiece, and in particular for use in a method according to the invention, or for carrying out a method according to the invention, and specifies and comprises the following:
     a) At least one shaping machine, particularly one that operates percussively, having at least two tools that are moveable with respect to one another for shaping a workpiece in a predetermined or predeterminable shaping position during at least one shaping step,   b) At least two handling devices for holding the workpiece in the shaping position during the shaping step, and   c) At least one control device for controlling or regulating the motions and positions of the handling devices.   

   The motion of the tools relative to one another in the shaping machine naturally also includes the case that only one of the two tools moves relative to the floor or machine frame or some other external reference system, and the other tool remains stationary with respect to this external system, for example for a double-acting hammer or drop hammer, or a screw press, as well as the case that both tools move relative to the external reference system, for a counterblow hammer, for example. The shaping position of the workpiece refers to its absolute and adjustable geometric position in space relative to an external coordinate system. A change in the shaping position generally consists of translatory and/or rotational changes in position or motion; i.e., the workpiece may be displaced and/or rotated. The working region of the shaping machine(s) is the area between the tools in which the actual shaping takes place. Multiple working regions may also be formed between two tools, which for example may be defined by various gravures in a forging die. For controlling the handling devices, the motion proceeds according to a predetermined or predeterminable motion sequence or motion profile, or a correspondingly stored control program (no feedback or “open-loop control”), whereas for regulation, the motions of the handling devices are metrologically measured and adjusted to predetermined target motions (reference input variables for the motion) or regulated (feedback or “open-loop control”). The term “automatic” means that at least during the shaping step itself it is no longer necessary to manually intervene or hold the workpiece, since this is automatically performed by the handling devices (or robotic motion devices) by controlling the control device. The motions or positions of the handling devices are coordinated with one another to enable precise handling of the workpiece, in particular to enable the workpiece to be fixed in the shaping position when struck in the shaping machine. Thus, there is no kinematic coupling between the two handling devices when the workpiece is handled during shaping. 
   The present invention is based on the concept that the workpiece is secured or held by gripping in at least two locations by a respective handling device, at least when struck by the tool(s), in particular striking tool(s), of the shaping machine during the shaping step. 
   This has the primary advantage that the workpiece is fixed at two locations when struck by the tool(s), and therefore can be more reliably kept from breaking out or sliding out from the tools. 
   A further advantage is that buckling of a long workpiece on one side can be prevented, since the handling devices are able to fix the workpiece on both sides and stabilize it during shaping. 
   One particular advantage of the invention is the possibility of compensating for a deviation in the position of the workpiece relative to the tools as a result of a corresponding deviation of the shape of the workpiece in a region in which a first of the handling devices engages. This is accomplished by using the second handling device to grip and secure the workpiece in a second region. The workpiece is brought into a sort of center position between the two handling devices by the measures according to the invention, whereas when grasped by only handling device, such as with the handling devices of the prior art, the workpiece is displaced or twisted on account of the tolerances. This problem of preproduction tolerances is irrelevant for manual handling of the workpiece, since a human operator easily corrects a deviation in the position of the workpiece and correctly inserts it. Thus, automatic correction of the position of the workpiece by use of automated image analysis to determine the position of the workpiece is not necessary according to the invention. In the invention, deviations are corrected mechanically, so to speak, by the fact that both handling devices constrain the workpiece in the target position by fixing or grasping it at two locations, optionally with corresponding deformation of the workpiece. 
   Advantageous embodiments and refinements of the method and the device for shaping a workpiece according to the invention are disclosed or otherwise recited in the specification and claims herein. 
   The kinematic coupling of the handling devices may be achieved by mechanical means, but preferably is implemented electronically or by using control or regulation devices by coupling with the actuation of the drive systems of the handling devices. 
   In addition to securely holding the workpiece during shaping, the handling devices may also perform other handling functions, in particular one or more of the following:
         Ventilating the workpiece immediately after the shaping blow or impact   Transferring the workpiece from one working region of a shaping machine to the next, or from one gravure of a tool to the next, or from one shaping position to the next   Rotating or swiveling the workpiece, in particular to change a shaping position   Regripping the workpiece to account for its change in shape after a shaping step   Receiving the workpiece from a pickup device   Conveying the workpiece to or from the shaping machine, in particular to a deposit station.       

   In one advantageous embodiment, for at least a portion of the handling of the workpiece by two handling devices, both handling devices are moved synchronously and/or along trajectories essentially at a constant distance with respect to one another, and/or essentially at the same speed. 
   The control device controls or regulates both handling devices, in particular the respective drive mechanisms thereof, in one embodiment according to a master-slave control principle, in which a handling device acting as the slave follows the motions of a handling device acting as the master. 
   In an alternative preferred embodiment, the control device controls both handling devices, in particular the drive mechanisms thereof, independently of one another, in mutually adapted control sequences. 
   In general, during a motion and/or handling of the workpiece each handling device or its contact point on the workpiece travels along a trajectory determined in advance with a predetermined speed characteristic, and/or follows stored successive trajectory points at regular time intervals. 
   The associated trajectory of the handling device or its contact point on the workpiece is preferably learned in advance, but may also be calculated or simulated. 
   In one special embodiment, the trajectory of one of at least two handling devices or their contact points on the workpiece are learned, and the trajectory of at least one additional handling device or its contact point on the workpiece is calculated in advance from the learned trajectory of the first handling device, and is stored or calculated in real time. 
   During training of the trajectory of a handling device or its contact point on the workpiece, in general the associated trajectory is traversed, and the trajectory points are successively determined and stored at regular time intervals. The speed characteristic during training is preferably specified according to the subsequent speed characteristic for the process. For any given speed characteristic during training, the actual speed characteristic during operation may also subsequently be taken into account, and new trajectory points may be calculated and stored. During movement and/or handling of the workpiece, the handling device or its contact point on the workpiece in each case follows the trajectory points stored during learning, optionally after speed correction, in the same time intervals and in the same sequence as during learning. 
   During handling actions at the shaping machine, the two handling devices preferably are situated on opposite sides of the working region or of the shaping machine tools. Furthermore, the handling devices may also preferably be moved into a parked position to make the working region(s) of the shaping machine(s) accessible. 
   In one advantageous embodiment of the device, each handling device has
     a) at least one gripping mechanism having at least two gripping elements that are movable relative to one another for gripping the workpiece,   b) at least one support apparatus to which the gripping mechanism is or may be fastened, and   c) at least one conveying device for conveying the support apparatus along with the gripping mechanism.   

   The device is now preferably refined by the fact that a flexible connection of the support apparatus and conveying device in a flexible state results in at least partial absorption or damping of impacts or vibrations that are transmitted from the workpiece in the shaping machine to the gripping devices during the shaping process, thereby protecting the conveying device from these mechanical stresses, and that, in contrast, a rigid connection or position of the support apparatus and conveying device in a rigid state is used when the workpiece is handled during transport, or during rotation or swiveling before or after shaping steps. 
   In one preferred application of the invention, a forging hammer or screw press is used as the shaping machine. 
   The invention is further explained below, with reference to exemplary embodiments. In this regard reference is made to the drawings, wherein 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a device having two handling devices for grasping a workpiece, in a side view, 
       FIG. 2  shows the device according to  FIG. 1 , in which the two handling devices hold the workpiece placed in a shaping machine, in a side view, 
       FIG. 3  shows a cross section through one of the handling devices according to  FIG. 1 , in the sectional plane described by III-III, 
       FIG. 4  shows a sectional view according to  FIG. 3 , with the gripping mechanism and actuating device swiveled, 
       FIG. 5  shows the device according to  FIG. 1  or  FIG. 2 , in which after the shaping impact the two handling devices ventilate the workpiece located in the shaping machine, in a side view, 
       FIG. 6  shows a device for shaping a workpiece, having two handling devices which handle the workpiece along predetermined paths of motion, in a schematic perspective view, 
       FIG. 7  shows a device for shaping a workpiece, having two handling devices, during handling of the workpiece, in a top view, and 
       FIG. 8  shows a device for shaping a workpiece, having two handling devices in the parked position, in a top view, each in schematic representation. Corresponding variables and parts are provided with identical reference numbers in  FIGS. 1 through 8 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A first handling device is designated by reference number  2 , and a second handling device, by  2 ′. Each of the handling devices  2  and  2 ′ may be designed as manipulators or robots. In the exemplary embodiments illustrated in  FIGS. 1 through 5 , both handling devices  2  and  2 ′ have essentially the same design, each comprising a gripping mechanism (or gripping pincer) designated by  3  or  3 ′, a support shaft by  4  or  4 ′, a support device (or rigid control device) by  5  or  5 ′, a bearing part by  6  or  6 ′, a flexible element by  7  or  7 ′, a pivot drive (or rotary drive) by  8  or  8 ′, an articulated joint by  9  or  9 ′, an actuating device by  11  or  11 ′, and a conveying device by  16  or  16 ′. 
   Each gripping mechanism  3  or  3 ′ comprises two gripping levers  32  and  33  or  32 ′ and  33 ′, each having an associated gripping jaw (or gripping element, pincer jaw)  30  and  31  or  30 ′ and  31 ′, which by means of the actuating device  11  or  11 ′ are able to swivel with respect to one another about a swivel axis E or E′ in a swivel bearing  34  or  34 ′ for opening and closing the gripping mechanism  3  or  3 ′. The actuating device  11  or  11 ′ engages the gripping lever  33  or  33 ′ in an engagement bearing  35  or  35 ′, and is mounted in a swivel bearing  14  or  14 ′ so as allow swiveling about a swivel axis D or D′ on a holding part  61  or  61 ′ on the bearing part  6  or  6 ′. 
   The gripping lever  32  or  32 ′ of the gripping mechanism  3  or  3 ′ is coaxially connected via the support shaft  4  or  4 ′ to an intermediate part  60  or  60 ′ of the bearing part  6  or  6 ′, along an axis M. The flexible element  7  or  7 ′ is mounted between the intermediate part  60  or  60 ′ and the rotary drive  8  or  8 ′, which is connected to the articulated joint  9  or  9 ′ along a second axis N. Each of the flexible elements  7  or  7 ′ is connected via a flange  67  and  87  or  67 ′ and  87 ′ to the intermediate part  60  or  60 ′ and the rotary drive  8  or  8 ′, respectively, and is made of an elastic material, preferably an elastomer. 
   The front unit of the handling device  2  or  2 ′, namely, the gripping mechanism  3   3 ′, support shaft  4  or  4 ′, and bearing part  6  or  6 ′, in addition to the actuating device  11  or  11 ′ on the one hand, and the rear unit of the handling device  2  or  2 ′, namely, the rotary drive  8  or  8 ′ and the articulated joint  9  or  9 ′ in addition to the conveying device  16  or  16 ′ on the other hand, and, therefore, also the axes M and N thereof, are able to swivel with respect to one another in the flexible element  7  or  7 ′. 
     FIGS. 3 and 4  show an exemplary embodiment for a swivel motion, in a sectional view through the lifting cylinder for the actuating device  11  and the support shaft  4 , as well as the support part  50  of the handling device  2  according to  FIG. 1 . 
     FIG. 3  shows a vertical position in which a center axis B of the support part  50  of the support device  5  and a center axis C of the actuating device  11  and of the bearing part  6  coincide, and the actuating device  11  is thus positioned in the direction of the gravitational force G, seen from above the intermediate part  60  of the bearing part  6 . 
   In  FIG. 4 , the front unit of the handling device  2  is now swiveled or rotated to the right, in the clockwise direction, about a swivel angle β. The support shaft  4  thereby rotates about the rotational axis R in its support bearing  54  in the support apparatus  5 . The center axis C of the front unit, in particular of the bearing part  6  and actuating device  11 , and thus the gripping mechanism  3  as well, are now swiveled relative to the center axis B of the support device  5 , about the swivel angle β. In this manner a workpiece  10  may be rotated about the corresponding swivel angle β. 
   The support device  5  or  5 ′ for the handling devices  2  and  2 ′ according to  FIGS. 1 and 2  comprises a longitudinal connecting rod  53  or  53 ′ on which are situated a first fastening part  51  or  51 ′ extending transversely upward for connecting the connecting rod  53  or  53 ′ to the rotary drive  8  or  8 ′, and further to the rear, a second fastening part  52  or  52 ′ extending transversely upward for connecting the connecting rod  53  or  53 ′ to the articulated joint  9  or  9 ′, and in the front region an upwardly projecting support part  50  or  50 ′, transverse to the connecting rod  53  or  53 ′, for fixing or supporting the support shaft  4  or  4 ′. The support part  50  or  50 ′ has a recess as a support bearing (or shaft seat)  54  or  54 ′ for the support shaft  4  or  4 ′ (see  FIGS. 3 and 4 ). 
   In the state shown in  FIG. 1 , the handling devices  2  and  2 ′ are moved toward the workpiece  10  or  10 ′ in the direction of the illustrated arrows, axes M and N running coaxially with respect to one another as well as horizontally, i.e., perpendicular to gravitational force G, and the flexible element  7  or  7 ′ being essentially undeformed. The connecting rod  53  or  53 ′ now runs parallel to the axes M and N, and the support part  50  or  50 ′ supports the support shaft  4  or  4 ′, and thus the gripping mechanism  3  or  3 ′ connected thereto, in its support bearing  54  or  54 ′. The support device  5  or  5 ′ thus represents a mechanical bridge over the flexible element  7  or  7 ′, and in the position according to  FIG. 1  removes the flexibility of the handling device  2  or  2 ′ in the flexible element  7  or  7 ′, at least in the direction of the gravitational force G, and in the downwardly directed, lateral directions between the gravitational force G and the horizontal direction. The rigid connection is maintained solely by the intrinsic weight of the parts of the handling device  2  or  2 ′. The gripping mechanisms  3  and  3 ′ are in their vertical positions, and are open. 
   When they reach the workpiece  10  the gripping mechanisms  3  and  3 ′ close, thereby grasping the workpiece  10  at its ends  10 A and  10 B. The workpiece is conveyed to a shaping machine by conveying devices  16  and  16 ′, where it is placed on a tool in the shaping position for shaping. The handling device  2  or  2 ′ is thereby held in the rigid state by the support device  5  or  5 ′. 
     FIG. 2  shows the workpiece  10  in the laid-out state on the lower tool or forging die  12  of a forging hammer. By raising the lower unit of the handling devices  2  and  2 ′, i.e., by inclining the center axis N or N′ of the rotary drive  8  or  8 ′ and articulated joint  9  or  9 ′ about the angle of inclination a relative to the center axis M or M′ of the front unit about the flexible element  7  or  7 ′, the support device  5  or  5 ′ is disengaged from the support shaft  4  or  4 ′, since the support device  5  or  5 ′ together with the rotary drive  8  or  8 ′ and articulated joint  9  or  9 ′ remain aligned along the axis N or N′, and the support part  50  or  50 ′ therefore is at a sufficient distance from the support shaft  4  or  4 ′. During the inclined motion about angle α or α′, the forging die  12  is used as an abutment via the workpiece  10 . 
   The striking tool  13  on the striking mechanism of the forging hammer (not illustrated) now strikes the workpiece  10  in the impact direction A. Significant impact and vibrational stresses arise in the striking motion which are transmitted through the workpiece  10  to the handling devices  2  and  2 ′. However, the elastic elements  7  or  7 ′ now largely decouple these impacts or vibrations from the conveying device  16  or  16 ′ and rotary drive  8  or  8 ′, thereby protecting these drive devices from overload. Depending on the workpiece  10  and the desired shaping process, however, in many shaping processes it may be necessary to rotate the workpiece  10 , in particular about a rotational axis that extends through the workpiece  10 , its longitudinal axis, for example, before placing it on the forging die  12 . For such a rotational or swiveling motion, the gripping mechanisms  3  and  3 ′ together with the grasped workpiece  10  in the supported state, i.e., in engagement with the support device  5  located in the support shaft  4 , are swiveled about the desired rotational angle β in the same rotational direction and at the same rotational or angular velocity in order to rotate the workpiece into its desired shaping position without torsion. To this end, a rotational motion of a drive shaft of a drive motor, situated in the drive housing  80  or  80 ′ of the rotary drive  8  or  8 ′, or optionally via a transmission, is transmitted through the drive flange  87  or  87 ′ and the flexible element  7  or  7 ′ to the connecting flange  65  or  65 ′, which in turn also rotates the intermediate part  60  or  60 ′, support shaft  4  or  4 ′, and gripping mechanism  3  or  3 ′. Such swiveling motions occur, for example, during bending of a workpiece in a first forging process or forging step, and subsequent flat shaping or forging. The rotatability of the gripping mechanisms  3  and  3 ′ may be omitted if rotation is not desired. 
   Proceeding from  FIG. 2 ,  FIG. 5  shows the situation shortly after the striking tool  13  strikes the workpiece  10  and the surrounding regions of the tool  12 . The striking tool  13  is again set in upward motion away from the tool  12  by the recoil or, optionally, by a drive, into a recovery position RH. The workpiece  10  is now lifted from the tool  12  by a distance d, or ventilated. This ventilating motion by the two handling devices  2  and  2 ′ and the workpiece  10  held thereby follows the upwardly moving striking tool  13 , in the same direction as the recovery direction RH. The handling devices  2  and  2 ′ generally remain in the flexible position, as illustrated in  FIG. 5 . During or after this ventilating motion, scale material is blown out of the lower tool  12  by means of a blower. The ventilation also shortens the time that the workpiece  10  is in contact with the lower tool or forging die  12 . After the ventilation procedure, the workpiece  10  may now either be placed on the tool  12  again, on another forging die, or on another gravure of the tool  12 , and may be reshaped by the striking tool  13 . However, the shaping process may also be ended and the workpiece  10  moved by the two handling devices  2  and  2 ′, out of the ventilated position shown in  FIG. 5  and out of the working region of the shaping machine, and conveyed to a depositing device. 
     FIG. 6  shows an exemplary embodiment for handling a workpiece  10  with two handling devices  2  and  2 ′, starting with receiving at a pickup device  41  and eventually placing the workpiece on a tool  12  of a percussive shaping machine. The paths of motion or trajectories of the two handling devices  2  and  2 ′ are designated by S and S′, while the directions of motion are represented by arrows. 
   The two handling devices  2  and  2 ′ are each started at time t0 from a parked or starting position S(t 0 ) and S′(t 0 ) and move toward the workpiece  10  on the pickup device  41 . At time ti the handling devices  2  and  2 ′ reach the respective ends  10 A and  10 B of the workpiece  10  at the respective positions S(ti) and S′(ti). The gripping mechanisms  3  and  3 ′ now grasp the respective end  10 A or  10 B of the workpiece  10 , and the handling devices  2  and  2 ′ convey the workpiece  10  along trajectories S and S′. The two trajectories S and S′ run parallel to one another, and the handling devices  2  and  2 ′ are synchronously moved relative to one another. The motion of the workpiece  10  is therefore essentially only translational, and not rotational. The difference vector Δ=S′(tj)−S(tj) is thus always the same at any given time tj. At the end of the trajectories S and S′ the handling devices  2  and  2 ′ guide the workpiece  10  into the working region between the tools  12  and  13  of the percussive shaping machine, and move the workpiece  10  downward into a predetermined shaping position on the tool  12 , in an end position S(tn) for handling device  2  and S′(tn) for handling device  2 ′ at an end time tn, on opposite sides of the working region or tool  12  of the shaping machine. The workpiece  10 , indicated by dashed-dotted lines, is now in the shaping position on the tool  12  and may be shaped. 
   During shaping, the handling devices  2  and  2 ′, likewise indicated by dashed-dotted lines, once again hold the ends  10 A and  10 B of the workpiece  10 . After the workpiece  10  is shaped by impacting or striking the striking tool  13  on the workpiece  10 , a ventilating motion by the handling devices  2  and  2 ′ may now proceed, as shown in  FIG. 5 . Furthermore, the workpiece  10  may additionally or alternatively be transferred from one gravure of the tool to another, or may also be conveyed from the shaping machine to a depositing or transporting device. 
   As a rule, tools  12  and  13  are shaping tools, so-called forging dies, having gravures correspondingly matched to the desired shape of the workpiece. The handling devices generally hold the workpiece  10  during the entire forging cycle, and jointly and synchronously perform all handling motions necessary for the forging process. Handling motions include, among others, ventilating motions inside a gravure, as well as transferring motions from the supply device to the first gravure of the forging die, transferring motions between gravures in the forging die, and transferring motions from a gravure in the forging die to a transporting device. 
   Furthermore, workpieces are preferably forged whose ends, which are held by the handling devices during handling, are not symmetrical with respect to the workpiece axis. These workpieces are stretched in previous work steps, thereby forming unsymmetrical workpiece ends. The workpiece  10  is automatically aligned by being grasped at both ends  10 A and  10 B by respective handling devices  2  and  2 ′, and is thus placed precisely in its shaping position into the gravure or the tool  12 . 
   The joint and synchronous travel of both handling devices  2  and  2 ′ is achieved by an electronic coupling between the two handling devices  2  and  2 ′, the coupling being made via the master-slave operation of electrical drives, or, alternatively, by simultaneously starting independently operating drives. The start signal for the individual handling steps is supplied by a control device which controls the sequence between the percussive shaping machine and the two handling devices  2  and  2 ′. This control device may also perform the entire signal exchange. As a rule, the control device operates with the assistance of at least one digital processor, in particular a microprocessor or digital signal processor, and corresponding memories in which the sequence programs, control algorithms, and data for the motions are stored. Master-slave control devices known as such may be used for a master-slave operation. For independently operating drives, identical distances and speeds as well as error feedback and error reactions are provided between the independently operating drives to ensure precise and, in the event of malfunctions, reliable operation. 
   In a typical forging cycle, a workpiece is supplied by means of a supply device or pickup device. Both handling devices  2  and  2 ′ subsequently grip the workpiece  10  and jointly and synchronously place it into a gravure in the forging die of the percussive forging die shaping machine. The percussive forging die shaping machine is now actuated at a variable point in time during or at the end of the handling motion, and after striking is actuated the further handling of the workpiece is initiated at a variable point in time during or at the end of the striking motion. This further handling is once again performed jointly and synchronously by both handling devices  2  and  2 ′, and may be a ventilation motion of the workpiece in the same gravure, a joint and synchronous transfer of the workpiece to another gravure, or the joint and synchronous transfer of the workpiece to a depositing device for the finished, shaped workpiece. 
   If the workpiece  10  is designed so that the first handling and forging steps can be performed by only one handling device, the second handling device  2 ′ likewise grips the workpiece  10  at a later time in the forging cycle, and after this point in time both handling devices  2  and  2 ′ perform forging jointly and synchronously, as already described. The partial transfer or forging with only one handling device is particularly meaningful when more than two handling devices are used, since in this manner the additional handling device(s) can pick up a new workpiece and optionally forge it while the other two handling devices finish forging the previous workpiece or place it in a transporting device. By use of this design, shorter cycle times may be achieved with at least three handling devices. 
     FIG. 7  shows a further exemplary embodiment of a device for handling a workpiece during a forging process. This device once again comprises two handling devices  2  and  2 ′ with respective gripping mechanisms  3  and  3 ′, schematically illustrated as industrial robots. The two handling devices  2  and  2 ′ take a workpiece  10  from a pickup device  41 , such as a feed conveyor belt or other automated supply device, for example, and place the workpiece in a first gravure  17  in a tool  12  of a percussive forging die shaping machine. The counter-tool or striking tool of this forging die shaping machine is not illustrated, but in the top view shown would be located above the plane of the drawing. During or at the end of the handling motion, or the transfer motion from the pickup device  41  to the first gravure  17  in the tool  12 , the striking tool of the shaping machine is actuated. After the striking action has been actuated, a new sequence is initiated for further handling of the workpiece  10  at a time during or at the end of the striking motion by the striking tool. The workpiece  10  is then fixed in its shaping position on the gravure  17  by both handling devices  2  and  2 ′ and held securely at both ends, up until and during the time that the striking tool strikes the workpiece  10 . After the workpiece  10  is struck and released by the striking tool, the workpiece  10  is jointly and synchronously handled by both handling devices  2  and  2 ′ according to the stored routine for further handling. The workpiece  10  is then ventilated, as already described with reference to  FIG. 5 , and then is either processed once again in the first gravure  17  or immediately transferred to the second gravure  18  in the tool  12 . After the workpiece is transferred to the second gravure  18  a shaping step is carried out again, with actuation of the shaping machine and its striking tool at a variable point in time during or at the end of the handling motion between the first gravure  17  and the second gravure  18 . After the striking motion is actuated, once again the further joint, synchronous handling of the workpiece  10  is initiated at an adjustable point in time during or at the end of the striking motion. The workpiece may now be jointly and synchronously ventilated again by both handling devices  2  and  2 ′ in the second gravure  18  and, optionally, inserted once again into the gravure  18  for additional processing, or the workpiece  10  may be immediately transferred to the depositing device  42  for the finished, shaped workpiece  10 . 
     FIG. 8  shows a parked or rest position of both handling devices  2  and  2 ′ in a device according to  FIG. 7 . In the parked position of the handling devices it is possible to access the tools  12  and  13  of the shaping machine for replacing tools, reworking, or performing manual test operations on the percussive shaping machine. 
   The motion of the handling devices  2  and  2 ′, and thus the handling motions for the workpiece  10 , are generally learned. To this end, in a training process the workpiece  10  together with the two handling devices  2  and  2 ′ is guided along the provided trajectory, optionally with rotational motions, and the individual spatial points or the corresponding motion parameters in the motion system of the handling devices  2  and  2 ′ are stored at regular time intervals, typically 16 ms. In the exemplary embodiment of  FIG. 6 , for example, the trajectories S and S′ of handling devices  2  and  2 ′ are respectively [stored] in the form of discrete data sets, each being associated with a point on the trajectories, beginning with the path point S(t 0 ) and S′(t 0 ), through S(ti) or S′(ti) and S(tj) or S′(tj), to the endpoint S(tn) or S′(tn). For the subsequent process the motion is guided along the stored trajectories S and S′. 
   If the actual speed characteristic has already been established during the training process, the spatial points S(tm) or S′(tm) determined in the training process for 0≦m≦n may be directly traversed by stepwise traversal from time t 0  to time tn in the predetermined time intervals Δ=tm+1−tm of, for example, 16 ms. If the speed characteristic for the training process does not correspond to the actual subsequent speed characteristic, the path points stored during the training process are recalculated by corresponding transformation or imaging to the path points provided for the subsequent process. This type of training of robotic motions is known as such, and therefore does not require a detailed description. 
   Instead of guiding a reference workpiece during the training process using two handling devices  2  and  2 ′, due to the mutually coordinated and generally synchronous motion of the handling devices  2  and  2 ′ it is also possible for only the motion of one of the handling devices  2  or  2 ′ to be learned, and the motion of the other handling device  2 ′ or  2  to be adapted to the motion of the handling device which has been trained. 
   This may be achieved in particular by a master-slave operation, in which in particular the second, untrained handling device follows in a stepwise fashion the motions of the trained handling device. 
   Alternatively, for the parts of the handling motions in which both handling devices  2  and  2 ′ are jointly and synchronously moved, as in the exemplary embodiment according to  FIG. 6 , for example, only one handling device, for example handling device  2 , is trained, and the associated motion trajectory S or, in a more general sense, the associated motion sequence that can be characterized by translational and rotational motions, is stored. Then, by simple translational imaging via the translation vector Δ according to  FIG. 6 , the trajectory S′ of the second handling device  2 ′ is calculated. Thus, the handling devices  2  and  2 ′ may have independent drive systems and control systems on the hardware side, yet be electrically or electronically coupled by mutually adapted control programs and sequences which permit the synchronous motions. Compared to a master-slave operation, this embodiment has the advantage that there is no longer any trailing distance between the two handling devices  2  and  2 ′ as a result of the stepwise tracking, as is the case for master-slave operation, but instead the two handling devices  2  and  2 ′ are located on mutually synchronous or parallel path points at any point in time tm. 
   In addition to the embodiments described with reference to  FIGS. 1 through 4 , other manipulators or industrial robots may also be used for the handling devices  2  and  2 ′, in which preferably a good damping of the moving articulated joints and other motion mechanisms is provided to relieve the drives from recoil and vibrations from impact of the striking tool of the shaping machine. The aforementioned handling devices according to DE 42 20 796 A1 and DE 100 60 709 A1, for example, may also be used. 
   In addition to the described handling motions, as an addition or alternative thereto other handling motions may also be provided by handling devices  2  and  2 ′, with or without the workpiece  10 . 
   The distance between the gripping mechanisms, distance vector Δ in  FIG. 6 , for example, generally depends on the length, or the dimension measured along this distance, of the workpiece, and as a rule remains constant during the joint and synchronous handling. 
   However, a change in the volume or the shape of the workpiece after the shaping process, in particular a lengthening of the workpiece, may also be considered. This is achieved by changing the contact points of the handling devices  2  and  2 ′ on the workpiece, such as by gripping farther out for a lengthening of the workpiece, for example. To this end, in particular the gripping pressure of gripping mechanisms  3  and  3 ′ may be reduced, and—without releasing the workpiece or opening the gripping mechanisms  3  and  3 ′—the gripping mechanisms  3  and  3 ′ of the handling devices  2  and  2 ′ may be moved farther out along the workpiece  10 . 
   In addition, the motion trajectories of both handling devices may also differ from one another in a mutually matched fashion, for example in an offset or correction, for example, if the workpieces have different ridges or some other different shape at the contact areas. 
   In a further embodiment, instead of a training process it is also possible to use an industrial robot having a motion characteristic that is controllable in a targeted manner inside an area accessible by the robot, in which the transformational description in the robot&#39;s three-dimensional coordinate system permits any given motion inside the area, without the motion previously having been made. This may be achieved in particular in a 3-D simulation. 
   The workpiece may also be rotated about a rotational axis, in particular by use of the embodiments of the handling devices described with reference to  FIGS. 1 through 4 . Of course, additional rotational motions or portions thereof are also possible in order to reach narrow areas on the transport path, for example. 
   The error communication via the control device illustrated in  FIGS. 7 and 8  allows the process to be interrupted, in particular the handling devices to be stopped, when there is an impermissible deviation of one of the handling devices from the specified trajectory at a given point in time. 
   LIST OF REFERENCE NUMBERS 
   
       
         2 ,  2 ′ Handling device 
         3 ,  3 ′ Gripping mechanism 
         4 ,  4 ′ Support shaft 
         5 ,  5 ′ Support device 
         6 ,  6 ′ Bearing part 
         7 ,  7 ° Flexible element 
         8 ,  8 ′ Rotary drive 
         9 ,  9 ′ Articulated joint 
         10  Workpiece 
         11 ,  11 ′ Actuating device 
         12  Forging die 
         13  Striking tool 
         14 ,  14 ′ Swivel bearing 
         15 ,  15 ′ Lifting cylinder 
         16 ,  16 ° Conveying device 
         17 ,  18  Gravure 
         30 ,  31 ,  30 ′,  31 ′ Gripping jaw 
         32 ,  33 ,  32 ′,  33 ′ Gripping lever 
         34 ,  34 ′ Swivel bearing 
         35 ,  35 ′ Engagement bearing 
         41  Pickup device 
         42  Depositing device 
         43  Control device 
         50 ,  50 ′ Support part 
         51 ,  52 ,  51 ′,  52 ′ Fastening part 
         53 ,  53 ′ Connecting rod 
         54 ,  54 ′ Support bearing 
         60 ,  60 ′ Intermediate part 
         61 ,  61 ′ Holding part 
         65 ,  65 ′ Connecting flange 
         80 ,  80 ′ Drive housing 
         87 ,  87 ′ Drive flange 
       M Front axis 
       N Rear axis 
       A Impact direction 
       B, C Axis 
       D, E Swivel axis 
       F Swivel axis 
       G Gravitational force 
       R Rotational axis