EP2629901B1 - Drawing press with dynamically optimized blank holding and deep drawing method - Google Patents

Description

The invention relates to a drawing press and a method for Tiefzichen, which is particularly suitable for integration in press lines, press lines, hybrid presses or transfer presses for the production of body parts. The drawing press according to the invention is particularly suitable for high stroke rates.

In the production of body parts or other large-scale, spatially shaped sheet metal parts, the first press stage is usually a drawing press, which gives a previously flat board a spatial form. This is done in a drawing tool that clamps the edge of the board, and also allows controlled to slide towards the center of the sheet, while the enclosed by the blank holder part of the sheet between a die and a stamp receives the desired spatial shape.

Today, drawing presses have become established in which the stamp is supported in a resting position on a press table and the associated die is held on the vertically movable plunger up and down. The blank holder surrounds the plunger and is pressed down against the force of a die cushion from the edge of the die during the drawing operation. In this basic configuration, the convexly curved sheet side is formed on the sheet metal part above, as it is also desired for the subsequent press stages. In the subsequent press stages in particular punching operations are performed. For body parts, it is usually required that the resulting burr on the hollow side, ie the concave underside of the sheet metal part is located. After turning stations and the like are to be rejected between the individual press stages, the design mentioned here has established itself as a standard. Designs with bottom die and top punch (and overhead plate holder) such as from the DE 10117578 B4 Therefore, they are less commonly used.

Presses, the type mentioned above, with overhead die and lying down, resting stored stamp are for example from DE 10 2006 025271 B3 known. In this press, both the plunger and the die cushion of servo motors is driven by screw jacks. After the plunger and the die each make a reciprocating motion, the servomotors must reverse their motion. The motion reversal takes place at the respective dead center of the movement of the die cushion or plunger. This means that the braking and acceleration phases of the servomotors noticeably increase the cycle time required to pull a sheet metal part.

In addition, it comes in such a press to considerable energy sales. To depress the sheet holder is a significant force, namely to overcome the plate holding force. This force can not be reduced arbitrarily - on the contrary, it must be larger with increasing sheet strength. The path to be traveled by the blank holder in this concept can likewise not be reduced arbitrarily, because it substantially corresponds to the depth of draw and is thus predetermined by the geometry of the workpiece. Even if the energy converted by the die cushion can be fed back into a store, into a network or to other consumers, energy losses are almost inevitable.

In addition, the disclosed EP 2 017 071 A1 a press according to the preamble of claim 1 with a spindle drive for the plunger and a method for deep drawing The plunger with the spindle drive keeps the tool closed for a while, the ram drive resting temporarily.

It is therefore an object of the invention to provide a press concept and a forming process, with which can be produced at a high stroke rate with low energy consumption while providing the desired in the following subsequent press stages component orientation thermoforming.

• Die erfindungsgemäße Ziehpresse weist wie üblich ein Pressengestell auf, das ein- oder mehrteilig ausgebildet sein kann. Es kann einen Kopf, einen Tisch und dazwischen angeordneten Ständern umfassen. Es ist ein Stößel zur Aufnahme eines Matrizenwerkzeugs vorgesehen, der in einer Verstellrichtung verstellbar gelagert ist. Zu seinem Antrieb dient mindestens ein Stößelantrieb, der mindestens einem Servomotor aufweist, der mit dem Stößel über ein Koppelgetriebe oder ein Kurvengetriebe verbunden ist. Als Koppelgetriebe wird jedes Getriebe verstanden, bei dem eine gleichmäßige Drehbewegung in eine periodisch veränderliche Bewegung umgeformt wird. Es weist somit mindestens einen Umkehrpunkt auf, bei dem die erzeugte Linearbewegung umkehrt, ohne dass die Drehrichtung des antreibenden Servomotors umkehren müsste. Eine solche Bewegungscharakteristik kann alternativ auch mit einem Kurvengetriebe erreicht werden, das z.B. aus einer drehenden Kurvenscheibe oder einem Nocken und einem linear beweglichen Kurvenfolgerelement besteht.

This object is achieved with the drawing press according to claim 1 and the method according to claim 12:

• As usual, the drawing press according to the invention has a press frame, which can be designed in one or more parts. It can include a head, a table and uprights in between. It is provided a plunger for receiving a Matrizenwerkzeugs, which is adjustably mounted in an adjustment. At least one ram drive, which has at least one servomotor which is connected to the ram via a coupling gear or a cam mechanism, serves for its drive. Coupling gear is understood to be any gear in which a uniform rotational movement is converted into a periodically variable movement. It thus has at least one reversal point, in which the generated linear motion reverses, without reversing the direction of rotation of the driving servomotor would. Such a movement characteristic can alternatively be achieved with a cam gear, which consists for example of a rotating cam or a cam and a linearly movable cam follower element.

In the press according to the invention the plunger takes the reversal point U _t in at least two temporally spaced points in time TA, TB in a single press stroke, running servo motor and closed die tool. The term "closed tool" is understood to mean that state in which the die tool is in contact with the workpiece, for example a sheet metal part.

By at least two times taking the turning point dynamic advantages are achieved, which allow a significant increase in the press working speed with reduced or constant machine load and possibly lower peak loads on the servomotors involved. The plunger drive has the task of closing movement and the generation of the plate holding force. Instead of braking to the reversal point U _t , the braking of the servomotor is initiated late, such that an overflow takes place. The area of the overflow is preferably of the order of magnitude which results, for example, in an eight-membered press drive with a blank holder. The forming process, in which the stamping tool deforms the board held at the edge, can be started upon reaching the reversal point U _t , ie, clearly before reaching the holding position of the plunger. Thus, with the first reaching of the reversal point U _{t of} the plunger and the die tool, the table drive associated with the plunger tool can be started. Well in time before the upper end position of the table drive is reached, the servomotor accelerates the sheet metal holding drive, So the ram, in the reverse direction of rotation such that the second reaching the reversal point coincides with still closed die tool at least approximately to the time of reaching the movement end point of the table drive. The movement end point of the table drive may be an extended position of its coupling elements, if it is designed as a toggle mechanism or as an eccentric or other coupling mechanism.

As a result of the mode of operation presented, the tappet with the die tool, that is to say the sheet metal holding drive, already has an initial rotational speed at the second reaching of the reversal point, which accelerates the lifting of the die tool from the sheet metal part. Thus, the open time of the tool is increased overall, so that the press in turn can work faster overall. Compared to a mechanically identical press of identical design, in which the servomotor of the ram drive stops exactly at the reversal point U _t , can be achieved by significantly more than 10% increased stroke rates.

Preferably, the table drive is designed as a coupling transmission, whose elements are in an extended position upon reaching the upper end position. Thus structurally simple eccentric drives can be used both in the ram drive and in the table drive. At the same time for the ram drive already extending to only 200 ° degree of the circumference of the drive wheel of the eccentric teeth sufficient. For the table drive a toothing extends, which extends by 120 ° degrees to the drive of the eccentric. 360 ° all-round gears are superfluous. This leads to significantly less expensive designs of the drives.

In addition, it is possible to match the drive ranges of the servo motors of the ram drive and the table drive so that one of the servomotors regeneratively regenerates energy which is fed into a memory or at least one of the servomotors of the respective other drive, there to accelerate the servomotor contribute.

The concept presented allows the provision of a sheet metal holder, which may be supported for example on a stationary abutment. This blank holder rests relative to the punch tool which is moved into the die tool by the movement of the table during the drawing operation. The purpose of the table drive. Due to the stationary during the drawing operation positioning of the sheet holder, no, or at least almost no energy is required to apply the sheet holding force. The plunger carrying the die tool is held by the plunger drive substantially in the vicinity of the reversal point U _t . While this is done with cam gears ideal and without reversal of motion of the corresponding servo motor, this is achieved when using a linkage with extended position with expiring and reversing servomotor by the almost maintained stretched position of the coupling elements. The occurring movements of the plunger in the direction of movement are small and can be compensated for example by the elastic springing of the press frame. Alternatively, it is possible to equip the abutment of the sheet metal holder with a preferably kurzhubigen and hard suspension or with a force control device, eg hydraulic or mechanical nature.

As explained, the plunger drive preferably has a blocking position, in which acts on the plunger Forces are at least largely, if not completely bypassed the actual drive source, such as a servomotor, are introduced into the press frame. It can find eccentric, toggle, cam or similar gear application. In an eccentric gear, the extended position is the position in which the lever arm of the eccentric (connecting line between the center of rotation of the eccentric and the center of the eccentric) is aligned with the connected connecting rod.

The table drive provides the punch stroke, which is required for shaping the sheet metal part, preferably while the ram drive is in blocking position or other rest position. The die tool rests during the drawing process, in particular, it applies the sheet holding force against the likewise stationary sheet holder. The sheet-holding force is thus preferably initiated statically in the press frame both on the part of the plunger and the die carried by him, as well as on the part of the sheet holder and does not have to be applied by drives. This considerably reduces the power required to drive the ram as well as to drive the table. The power required to move the plunger is low. Apart from the power required to dynamically accelerate and decelerate the ram and die, the ram drive need only be uniquely constructed prior to the start of a pull stroke, after placing the die tool on the board. It is then held statically by the press frame. Alternatively, the sheet holding force can also be applied by a short-stroke plate holder drive. The plate holder drive may also have a blocking position. For example, it can be used as a short-stroke eccentric drive or be designed as a cam drive, which biases the blank holder against the edge of the die tool and introduces the clamping forces directly into the press frame. A blocking position is reached here when the eccentric drive is in an extended position or a cam drive is on a cam portion of maximum radius. A movement of the driving servomotor has no or only a negligible minimum sheet holder movement result.

To drive the table is only the work of deformation for the board to afford.

The proposed press concept minimizes the power to be applied to the ram drive and the table drive and the power exchange between these drives. In that regard, the press comes, compared to presses where an intense exchange of energy between ram drive and die cushion takes place, with the same power with smaller drives.

In addition, in the presented press concept the otherwise required total stroke of, for example, 1300 mm in two strokes, namely the stroke of the plunger and the stroke of the table, divided. While the stroke of the ram mainly serves to open and close the tool, the stroke of the table is used to move the punch and thus to carry out the actual drawing process. The ram stroke may e.g. only 100 mm and the table lift, e.g. only 300 or 400 mm. Also for this reason, the plunger drive can turn out smaller than a conventional drive.

The proposed press concept allows the continued use of existing tool sets, which in themselves for operation with resting stamp and during the drawing process down Moving blank holder were provided. Also, conventional transfer devices can continue to be used without significant adaptation. In the drawing press according to the invention, the linearly movable table can have a group of passages through which supporting elements extend. These support elements, for example in the form of straight pressure pins, extend through these passages and support the blank holder on an abutment. The abutment is preferably arranged stationary with respect to the press frame. This means that the position of the sheet holder with respect to the press frame is fixed or optionally fixed by an adjustment. If the board lying on the blank holder is clamped by the die against the blank holder and then the plunger drive is in blocking position (ie, for example, its gear in an extended position), the blanking force is determined by the springing of the press frame. This springing can be in the range of a few millimeters to a few 10 mm. The elastically stored in the press frame energy can be transferred back on the return stroke of the plunger on the ram drive, which further reduces the gross energy consumption of the drawing press.

It is, as mentioned, also possible to associate an abutment hydraulic or mechanical nature of the abutment. For example, the adjustment as explained above, a short-stroke toggle mechanism or an eccentric or the like. The adjustment stroke will typically be at most a few 10 mm. This concept is particularly advantageous when the plunger drive between the two times in which it has its reversal position U _t , performs a certain movement, or if he can drive with little force in its blocking position and lock there, as it is in a Cam mechanism may be the case. In this case, the blank holder force can be applied after blocking the plunger of the short-stroke plate holder drive. The Verstellhub the sheet holder drive is then preferably at least as large as the total occurring springing of the press frame.

Independently of each other, both the ram drive and the table drive are preferably servomotor drives. The servomotors work on the plunger or the table preferably via gears that have at least one rest position. A rest position is a position in which the reduction between servo motor and plunger or table in at least one point is very large or even infinite. This applies to eccentric gear as well as toggle mechanism in the extended position of the elements involved. Multi-unit transmissions with multiple stretched positions can be used to advantage.

• Figur 1 - eine erfindungsgemäße Ziehpresse in schematisierter Darstellung bei offenem Werkzeug,
• Figur 2 - die Presse nach Figur 1 zu Beginn eines Ziehvorgangs,
• Figur 3 - die Presse nach Figur 1 bei Abschluss eines Ziehvorgangs,
• Figur 4 - eine abgewandelte Ausführungsform der erfindungsgemäßen Ziehpresse in schematisierter Darstellung,
• Figur 5 - ein abgewandelter Antrieb der als Stößelantrieb oder alternativ auch als Tischantrieb bei der erfindungsgemäßen Ziehpresse dienen kann,
• Figur 6 - ein weiterer abgewandelter Antrieb der als Stößelantrieb bei der erfindungsgemäßen Ziehpresse dienen kann,
• Figur 7 - Weg/Zeit-Diagramme des Stößelantriebs.

Further details of advantageous embodiments of the invention will become apparent from the claims, the drawings or the description. Show it:

• FIG. 1 a drawing press according to the invention in a schematic representation with an open tool,
• FIG. 2 - the press after FIG. 1 at the beginning of a drawing process,
• FIG. 3 - the press after FIG. 1 upon completion of a drawing operation,
• FIG. 4 - A modified embodiment of the drawing press according to the invention in a schematic representation,
• FIG. 5 a modified drive which can serve as a ram drive or alternatively also as a table drive in the drawing press according to the invention,
• FIG. 6 a further modified drive which can serve as a ram drive in the drawing press according to the invention,
• FIG. 7 - Distance / time diagrams of the ram drive.

In FIG. 1 a drawing press 10 is illustrated, which can be used for the production of large sheet metal parts, such as body parts. To the drawing press 10 includes a press frame, the at least one, preferably a plurality, preferably vertically oriented stand 11, 12, a head 13, which is supported by the uprights 11, 12 and a pedestal 14 belonging under or between the uprights 11 , 12 is arranged. The head 13, the stand 11, 12 and the base 14 form a closed frame. In this, a plunger 15 is mounted linearly movable in a vertical movement direction 16, for example. For the purpose of supporting the plunger 15, for example, linear guides 17 provided on the uprights 11, 12 are used.

The plunger 15 serves to receive an upper tool part, which is designed as a die tool 18. It is in FIG. 1 shown in section and has a rim 19, which serves for clamping and holding the edge of a workpiece during the drawing process. The workpiece is formed by a board 20, ie an initially flat sheet. The rim 19 surrounds a tool cavity 21 into which the workpiece is to be deformed.

To drive the plunger 15 is a ram drive 22 which comprises one or more servo motors 23, 24 which are connected via one or more gear 25, 26 with the plunger 15. The two gear 25, 26 are coupling gear suitable design. In the present exemplary embodiment, each example is an eccentric gear designed mirror-symmetrically with respect to one another. They each comprise an eccentric 27, 28, which is coupled via a connecting rod 29, 30 with the plunger 15.

Furthermore, the drawing press 10 has a press table 31, on which a travel table 32 can be arranged. Of the Drive table 32 is used in a known manner the tool change. The drive table 32 carries the lower tool part, to which a tool support 33, with a punch tool 34 arranged thereon and a blank holder 35 belong. The punch tool 34 is a male whose upper contour corresponds to the cavity 31. It is surrounded by the rectangular-shaped sheet holder 35 in most cases, wherein the sheet holder 35 and the punch tool 34 are movable relative to each other with respect to the movement direction 16.

The unit consisting of the punch tool 34, the tool support 33, the drive table 32 and the press table 31 rests on a table drive 36 which is movable in the direction of movement 16 (see corresponding arrow) in the direction of the plunger 15 and away from it. The press table 31, or its table drive 36, is linearly movable in the press frame on the uprights 11, 12 and / or the base 14 by means of guide means 37 in the direction of movement. To the table drive 36 include one or more gear 38, 39, which, like the transmission 25, 26, each constructed as a coupling gear. You have a blocking position. They are e.g. designed as an eccentric gear that bring the press table 31 with one or more servomotors 40, 41 in drive connection. The gear 38, 39 each comprise an eccentric 42, 43, which is connected via a connecting rod 44, 45 with the press table 31.

The blank holder 35 is supported on suitable abutment elements, for example in the form of pressure pins 46, on an abutment 47. The abutment 47 may be arranged stationary in the simplest case with respect to the base 14. Alternatively, it may be associated with an adjustment device 48 which can adjust the position of the abutment 47 with respect to the direction of movement 16, for example. this happens usually in no-load condition. However, the adjustment 48 may also be designed so that it can adjust the abutment 47 under load, for example, to specifically influence or regulate the force acting on the blank holder 35 and thus on the drawing edge of the workpiece force. The adjusting apparatus 48 may be in the form of hydraulic cylinders, toggle adjusters, Hubspindelverstellapparaten or the like. Between the abutment 47 and the table drive 36 16 oriented linear guides 49 may be provided in the direction of movement.

• Zunächst befindet sich die Ziehpresse 1 in Offenstellung. Dazu ist der Stößel 15 durch entsprechende Drehung der Exzenter 27, 28 in eine obere Position verfahren. Der Pressentisch 31 ist durch entsprechende Drehung der Exzenter 42, 43 in eine untere Position gefahren. Somit steht das Stempelwerkzeug 34 wenig oder nicht wenig über den Blechhalter 35 vor. Eine im Wesentlichen ebene Platine 20 kann auf den Blechhalter 35 aufgelegt werden.

The drawing press 10 described so far operates as follows:

• First, the drawing press 1 is in the open position. For this purpose, the plunger 15 is moved by appropriate rotation of the eccentric 27, 28 in an upper position. The press table 31 is driven by corresponding rotation of the eccentric 42, 43 in a lower position. Thus, the punch tool 34 protrudes little or not much above the sheet holder 35. A substantially planar board 20 can be placed on the blank holder 35.

As soon as corresponding workpiece transport means, not shown here, such as feeder, suction spiders or other grippers, have moved out of the tool room, the tool can close. For this purpose, the drawing press 10 in the in FIG. 2 illustrated position transferred. The servo motors 23, 24 not shown here have the eccentric 27, 28 turned so far that the plunger 15 has reached its lower reversal point U _{t for the} first time. Shortly before reaching the lower reversal point U _t , the edge 19 of the Matrizenwerkzeugs 18 on the edge of the board 20 and begins this against the Sheet holder 35 to press. The blank holder 35 rests unrelentably on the abutment 47 via the support elements 46, so that now the press frame is tensioned in the direction of movement 16. Its spring constant determined in conjunction with the set position of the sheet holder 35, the force acting on the edge of the board 20 clamping force very precise.

If the lower reversal point U _t of the plunger 15 and thus the clamping position of the Matrizenwerkzeugs 18 at a time TA ( FIG. 7 , Curve I), the servomotors 23, 24 are completely or at least almost free of load. The sheet-holding force is supported on the head 13 via the Pleuelexzenteranordnung located in the extended position of the transmission 25 and 26. No energy is consumed to maintain the holding force acting on the edge of the board 20. There is also no energy exchange between ram drive and any die cushion instead.

The servo motors 23, 24 begin to brake when approaching the reversal point U _t , pass through the reversal point U _t and then stop, as shown in the diagram FIG. 7 , there curve I emerges. The plunger 15 thus performs after passing through the time TA a barely noticeable movement away from the reversal point U _t . The servomotors 23, 24 then stop at time TC and immediately or shortly thereafter reverse their direction of rotation to again pass through the reversal point U _t . This happens at the time TB. Preferably, the gears 38, 39 reach their extended positions at this exact time, marking the completion of the drawing operation. From here on, the opening movement of the die tool 18 starts by moving away from the turnaround point U _t in the case of already rotating, ie, in the time interval from TC to TB, pre-accelerated servomotors 23, 24. The opening of the tool is done very quickly, faster in any case, than it the case would be, the servomotors would still stand still at time TB.

The same applies already for the closing of the tool. The braking of the servomotors when approaching the plunger position to the reversal point U _t can be done relatively late, so that despite possibly full braking power at TA still no engine stall is reached, but only at TC.

Starting from the state at time TA, the actual drawing process is initiated via TC to TB, the end of which in FIG. 3 is illustrated. To carry out the drawing operation, the servomotors 40, 41 are activated, so that the eccentrics 42, 43 with the connecting rods 44, 45 go into an extended position, and thus reach the top dead center of the table drive 36. In this, the punch tool 34 is fully retracted into the die tool 18. When approaching the extended position, the reduction between the servomotors 41, 42 and the press table 31 approaches infinity, so that the punch tool 34 can apply very high pressures to the workpiece.

Furthermore, after TB, the tool consisting of the die tool 18 and the punch tool 34 is opened again as described above, by moving the plunger 15 upwards and the press table 31 downwards while the sheet holder 35 continues to rest.

The drawing press 10 so far described offers a concept which is suitable for the further use of drawing tools which have hitherto been used in presses with drawing cushions arranged at the bottom. For this purpose, the press table 31 has a group 50 of openings 51, 52, 53, through which the support elements 46 can optionally be inserted therethrough. In that regard, tools of different sizes can be used, whose blank holder 35 span different distances. This results in a geometrically variable introduction of force for the sheet holder 35. This also provides increased freedom or comfort in tool design. The presented operating concept with at least two passes of the reversal point U _t during a press cycle shortens the cycle time and increases the stroke rate and output.

Numerous modifications are possible on the presented press concept while maintaining the basic principle. For example, the plunger 15 can be moved by the gear 25, 26 pulling when the servomotors 23, 24 are arranged on the base 14.

Further, the drive of the press table 31 in this and in all other embodiments by a single servo motor 40 can be effected when the gears of the eccentric 42, 43 mesh with each other or when the eccentric 42, 43 are connected in any other way by suitable transmission means. In addition, the eccentric 42, 43 may optionally be formed as a full circle. This measure can also be found in the eccentrics 27, 28 and their gears application.

Also shows FIG. 5 a drive device which can be used either as a ram drive 22 as well as a table drive 36 application. Also, this drive has a rest position when its links 52, 53 are in an extended position. In this extended position causes a rotation of the driving servo motor 23, 24 (or corresponding to 40, 41) no or only an extremely low linear adjustment of the connected member, such as the plunger 15. These forces acting on straight paths by the handlebars 52, 53 at the machine frame supported without the Load servo motors.

FIG. 6 schematically shows a transmission 22, which is designed as a cam gear 54. It has a driven by the servo motor 23 cam 55 and a cam follower 56, for example in the form of a roller, which follows the curve circumference and thus performs a predetermined by the different radii of the cam linear, reciprocating motion. The cam follower 56 is guided in a linear guide 57 and connected to the plunger 15. The cam gear can the movement curve II of FIG. 7 provide. For example, the cam 55 has at its one portion 58 of constant radius. This determines the reversal point U _t .

For the function of a press with this cam mechanism 54, the preceding functional description applies accordingly. In addition, the servomotor 23 can be operated not only reversing, but alternatively also continuously. The plunger 15 then moves to the reversal point U _t , takes this during the time TA, the time TB and possibly other times eg between TA and TB. The plate holding force does not have to be applied by the rotating servomotor in this phase, because forces acting on the plunger 15 produce no torque because of the radius of the cam which is constant in this section 58. Depending on the design of the cam 55, the servomotor 23 can be operated at a constant speed, at a varying speed, with a constant direction of rotation or with alternating directions of rotation. It also eliminates time to slow down and accelerate the servomotor before and after the drawing process. As with the previous example with eccentric gear, these acceleration phases can be moved into the period of the drawing process. Alternatively, at least in the embodiment of FIG 6 are partly or completely dispensed with acceleration and braking operations.

The drawing press (10) according to the invention has for driving its plunger (15) a direction-reversing gear (22, 54), for example a coupling gear, and at least one servo motor (23). The servo motor (23) passes through that of the reversal point U _{t of} the plunger movement is determined by the kinematics of the linkage, for example, the extended position of an eccentric drive. During the closing of the tool (18), that is to say during a press stroke, the servo motor (23) is driven in such a way that it first passes through this reversal point U _t , then stops, reverses and then again passes through again to open the tool (18) , Thus, the still braking and re-accelerating the servomotor for the upper plunger (15) still or even during the actual drawing operation, ie during the sheet metal forming takes place, which significantly shortens the cycle time.

LIST OF REFERENCE NUMBERS

10

drawing press

11, 12

stand

13

head

14

base

15

tappet

16

movement direction

17

linear guide

18

die tool

19

edge

20

circuit board

21

cavity

22

ram drive

23, 24

servomotor

25, 26

transmission

27, 28

eccentric

29, 30

pleuel

31

press table

32

traveling table

33

Tool base

34

stamp tool

35

blankholder

36

table drive

37

linear guide

38, 39

transmission

40, 41

servomotor

42, 43

eccentric

44, 45

pleuel

46

support elements

47

abutment

48

adjustment device

49

linear guide

50

group

51, 52, 53

openings

52, 53

handlebars

54

cam gear

55

cam

56

cam follower

57

guide

58

section

Claims (12)

1. Drawing press (10)
   with a press frame,
   with a ram (15) provided for receiving a die tool (18) and mounted adjustably in an adjustment direction,
   with at least one ram drive (22) having at least one servomotor (23) which is connected to the ram via a coupling gear or a curve gear (43) having at least one reversing point (Ut),
   wherein a metal blank holder (35) is provided opposite the ram (15) and is supported on an abutment (47), and
   wherein a table (31) is provided for receiving a stamping tool (34), to which a table drive (36) is assigned in order to move this in the adjustment direction (16), wherein the table drive (36) assigned to the stamping tool is started when the ram (15) and die tool (18) first reach the reversing point U_t,
   characterized by
   a control system which is configured to control the at least one servomotor (23) such that on a single press stroke, with running servomotor (23) and closed die tool (18), the ram (15) reaches the reversing point (U_t) at least at two times (TA, TB) temporally spaced apart, and the servomotor (23) completes a reversal of rotation direction between the times (TA, TB).
2. Drawing press according to claim 1, characterized in that the coupling gear is an eccentric gear.
3. Drawing press according to claim 1, characterized in that the abutment (47) is arranged stationarily on the press frame.
4. Drawing press according to claim 1, characterized in that the abutment (47) and the ram (15) are arranged sprung relative to each other.
5. Drawing press according to claim 1, characterized in that an adjustment drive (48) for controlling the blank holding force is assigned to the abutment (47).
6. Drawing press according to claim 1, characterized in that the table drive (36) has a gear (25, 38) with at least one rest position in which no movement is transmitted from its gear output to a servomotor (24, 40) connected to its gear input.
7. Drawing press according to claim 6, characterized in that the gear (22, 38) is a coupling gear.
8. Drawing press according to claim 7, characterized in that the coupling gear is an eccentric gear ().
9. Drawing press according to claim 8, characterized in that the table drive (36) has in each case at least one servomotor (23, 40) operated in reversing mode.
10. Drawing press according to claim 9, characterized in that the table drive (36) contains an eccentric gear, the eccentric (42) of which passes through a rotary angle of less than 90 degrees on a press stroke.
11. Drawing press according to claim 1, characterized in that the press frame has a head (13), a table (31) and stands (11, 12) arranged in-between.
12. Method for deep-drawing of a metal blank, in particular a bodywork component, with a drawing press (10) which has a ram (15) for receiving a die tool (18) and movable between an open position and a closed position, wherein on a press stroke, the ram (15) reaches and passes through a reversing point (U_t) and hence its bottom dead centre marking the closed position, wherein the servomotor (23) driving it is braked and reversed in order to transfer the ram (15) into the open position after passing through the dead centre again, wherein the table drive (36) assigned to the stamping tool is started when the ram (15) and the stamping tool (18) first reach the reversing point (Ut).

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