EP2926920A1 - Pressing device for processing a workpiece - Google Patents

Abstract

The invention relates to a press device (1), in particular a toggle press (2), for machining a workpiece (18) with lower tool unit (13) and with a movable upper tool unit (8), in which the upper tool unit (8) has a hold-down device (8). 20) with a shock-guiding part (21), by means of which the workpiece (18) to be machined with respect to the sub-tool unit (13) can be held down, and the lower tool unit (13) comprises a counter-holding device (24) with a further Stößeiteil (25), by means of which the workpiece to be machined (18) against a tool part (9) of the upper tool unit (8) is untenable comprise, wherein the plunger parts (21, 25) by means of a drive means (23, 27) relative to the upper tool unit (8) and / or Lower tool unit (13) are displaceable, and wherein the counter-holding means (24) and / or the hold-down means (20) bridging means (50) for bridging an acceleration Sphere of the respective drive means (23, 27), in which the respective drive means (23, 27) can be accelerated to the respective ram speed.

Description

The invention relates to a press device, in particular a toggle press, for machining a workpiece with a lower tool unit and with a movable upper tool unit, wherein the upper tool unit a hold-down device with a plunger part, by means of which the workpiece to be machined against the lower tool unit is untenable, and the lower tool unit a Counter holding device with a further plunger part, by means of which the workpiece to be machined against a tool part of the upper tool unit is untenable, comprising, wherein the plunger parts in each case by means of a drive device relative to the upper tool unit and / or the lower tool unit are displaced.

Generic press devices are known from the prior art. In some forming processes, such as gene cutting, a down and an anvil are needed to precisely machine the workpiece. As a rule, the holding-down device is located as a ram part in an upper tool unit and lies in a forming process flush on the material to be formed of the workpiece in order to counteract the compressive and tensile stresses occurring during the forming process. As a rule, the counterholder is located as a further plunger part immediately below the material to be formed. It keeps during the entire forming process with a force as constant as possible against a cutting punch coming from above to ensure a controlled forming process. Following the forming process can the counter-holder or the related additional plunger part serve as an ejector for the cut part. Lower and counter holders can be designed mechanically (for example, by mechanical spring elements), pneumatically or hydraulically (for example, by pneumatically or hydraulically driven spring elements).

The invention has for its object to further develop generic devices such that their manufacturing precision and reliability are further increased.

The object of the invention is achieved by a press device, in particular by a toggle press, for machining a workpiece with a lower tool unit and with a movable upper tool unit, in which the upper tool unit a hold-down device with a plunger part, by means of which the workpiece to be machined against the lower tool unit can be held down , and the lower tool unit comprises a counter holding device with a further plunger part, by means of which the workpiece to be machined against a tool part of the upper tool unit is untenable, the plunger parts are each displaced by means of a drive means relative to the upper tool unit and / or the lower tool unit, and wherein the press device characterized in that the counter-holding device and / or the hold-down device bridging means for bridging an acceleration phase of the respective Antriebssei include in which the respective drive means can be accelerated to the respective ram speed.

By means of such bridging means, it is possible to accelerate the respective plunger part bypassing its actual drive device immediately at the beginning of, for example, a cutting process or the like to the speed of the plunger part corresponding therewith.

According to the present invention, for example, a counterholder of the lower tool unit can move from the beginning exactly synchronously with the movement of the upper tool unit or a related punch or the like. As a result, the manufacturing precision can be significantly increased.

In the present case, a response time with a sufficiently large time window is available for the actual drive device in order to likewise accelerate the respective drive device to the respective ram speed before, for example, the drive device subsequently drives the counter-holder.

By virtue of the fact that these bridging means are integrated in the counter-holding device or cumulatively or alternatively in the hold-down device, the respective plunger part can be structurally very easily accelerated independently of its actual drive device by the respective corresponding plunger part.

With the present bridging means, therefore, the essential goal is achieved to provide a total drive, by means of which at the beginning of a cutting process a precise synchronization of the movement, in particular of the counter-holder can be made to a plunger part speed of the upper tool unit.

For example, after a successful cutting operation, the respective plunger part whose speed has been synchronized according to the invention, for example, take over an ejector function, which is preferably freely programmable with respect to its path.

The term "pressing device" in the context of the invention describes any type of presses in which the upper tool unit relative to the lower tool unit or vice versa, to thereby machine the workpiece by means of at least one tool. It is understood that this press device can be configured almost arbitrarily. It is particularly advantageous if it is designed as a toggle press and in this case especially as a precision cutting and forming press with servo toggle lever drive, since this is often involved in a variety of high-precision machining processes. Additional advantages are explained in detail below in connection with a press apparatus designed by way of example as a precision cutting and forming press with servo toggle lever drive.

The term "upper tool unit" herein describes a press ram of a press, which is moved to edit the workpiece against a press table.

Accordingly, the term "lower tool unit" herein describes a press table of a related press.

A tool or tool part used on the present press device can be of different nature. For example, it may be a cutting tool, as will be explained later.

The plunger part of the hold-down device comprises a hold-down device. Accordingly, the further plunger part of the counter-holding device comprises a counter-holder.

In contrast to the counter holding device, moving the bottom dead center of the upper tool unit, the movement of the hold-down device is not stopped. The hold-down device acts as a scraper during the upward movement of the upper tool unit via a defined path. While the stripping, the movement of the hold-down device must continue to run synchronously with the plunger movement.

In principle, two operating modes are provided for operating the low or counter holding devices: setting up and automatic. In addition to manual jogging, the operator can automatically approach a pre-entered target position or a coupling position suitable for the press position in set-up mode. The low or counter holding devices can be moved independently but never several at a time. The selection of the active device via buttons by means of a visualization unit. It is also possible, after entering the setpoints, to create a corresponding movement profile for the devices. Specifically for the counter-holding device, the desired function "counteract - eject (= 1)" or "eject only (= 2)" can be entered as a function number via an input field. In automatic mode, the selected device is activated and coupled via a cam to the movement of the upper tool unit. The values set in set-up mode are valid. Several facilities can be selected and activated together here.

In any case, by means of the present bridging means, it is advantageously possible to bridge the period of time required to accelerate the respective drive device in suitable catfish to the speed of the plunger part in order to exclusively drive, with a time delay, the plunger part assigned to it.

It is understood that the bridging means provided in the context of the invention can be of various shapes. A preferred embodiment, however, provides that the bridging means comprise a pneumatic spring device. Such a pneumatic spring device can be configured structurally simple in the lower tool unit or the upper tool unit.

The present pneumatic spring device is structurally particularly expediently realized when the pneumatic spring device comprises a nitrogen spring.

It is particularly advantageous if the bridging means comprise a reaction path of more than 10 mm or more than 20 mm, preferably 25 mm. By means of such a reaction path can be ensured that the respective drive means can be accelerated during the machining process to the speed of its associated plunger part.

In addition, the present reaction spring travel of 25 mm can be provided structurally simple and reliable by means of the nitrogen spring.

In this respect, the integration of the pneumatic spring device within a low or counter holding device to press devices is already advantageous for itself. For this reason alone, the features in relation to this pneumatic spring device are also advantageous without the other features of the invention.

Depending on the type of application, even a lesser reaction path of 10 mm or 20 mm may be sufficient to provide a required bridging period. Such a required bridging period can be reliably provided in any case when the reaction path is 25 mm.

It is understood that the reaction path can be chosen even larger. However, this does not make sense, since a response time of 25 mm can provide a sufficiently long response time. In addition, larger reaction spring travel only need unnecessarily much space.

In the present case, such a reaction path is simply formulated in a constructive manner if the reaction path is interrupted by means of a pressure chamber filled with a pressure medium a piston bottom of the piston part and a cylinder housing end wall of the cylinder housing is formed. The pressure medium can be of various types. It preferably comprises nitrogen.

The bridging means can be structurally particularly advantageous integrated into the upper tool unit or in the lower tool unit of the present press device, when the bridging means between the plunger part and the drive means are arranged.

Moreover, it is advantageous if the bridging means comprise a cylinder housing and a piston part, wherein the plunger part is arranged on the cylinder housing. As a result, components of the bridging means can be compactly integrated into the press device. This can be achieved constructively with the pneumatic spring device.

A region of the lower tool unit facing the upper tool unit can be overcome in a structurally simple manner by bridging means arranged within the lower tool unit, when the plunger part is arranged at a distance from the cylinder housing end wall on the cylinder housing by web elements.

The bridging means can be addressed in a structurally simple and rapid manner if the bridging means comprise a cylinder housing and a piston part guided therein, the cylinder housing being displaceably arranged in the lower tool unit in the pressing direction of the upper tool unit.

If the bridging means have a cylinder housing and a piston part guided therein, the cylinder housing being displaceably guided in a guide bush of the upper tool unit or the lower tool unit on the one hand, the cylinder housing are moved relative to the upper tool unit or the lower tool unit and, on the other hand, relative to the piston part.

Furthermore, it is advantageous if the bridging means comprise a cylinder housing and a piston part guided therein, wherein the cylinder housing is displaceable by means of the piston part with respect to the upper tool unit or the lower tool unit. As a result, the cylinder housing via the piston part by means of the drive device can be easily moved constructively. This is the case, for example, if the further plunger part of the counter-holding device is to be moved synchronously with the upper tool unit, or if the further plunger part of the counter-holding device is to function as an ejector for a machined workpiece.

The respective plunger part can easily be displaced with respect to the upper tool unit or the lower tool unit if the bridging means comprise a cylinder housing and a piston part guided therein, wherein the piston part is arranged on a connecting rod part of an eccentric drive of the drive device.

A sufficient counterforce can be applied, in particular, to the further plunger part of the lower tool unit if the pneumatic spring device is preloaded with a spring biasing force F having a value of more than 100 kN or a value of more than 200 kN, preferably a value of 300 kN.

A key feature of the present invention is in particular a synchronization of the other plunger part or the counter-holder on the speed of the plunger part and the upper tool unit at a time, which represents the beginning of about a cutting process or the like. By means of the present bridging means it can be ensured that the further plunger part or the counterholder moves from this point onwards at least approximately at the same speed as the plunger part or the upper tool unit.

The present object is achieved according to a further aspect of the invention by a press device, in particular toggle press, for machining a workpiece with a lower tool unit, with a movable thereto upper tool unit, and with an overload protection unit to protect the press device in case of malfunction, in which the upper tool unit a Hold-down device with a plunger part, by means of which the workpiece to be machined with respect to the lower tool unit is untenable, and the lower tool unit comprises a counter holding device with a further plunger part, by means of which the workpiece to be machined against a tool part of the upper tool unit is untenable, wherein the plunger parts in each case by means of a drive device relative to the upper tool unit and / or the lower tool unit are displaceable, and wherein the press device is characterized in that the Gegenhalteeinrichtun g and / or the hold-down device comprise bridging means for bridging a tripping time for triggering the overload protection unit.

Despite a variety of safety precautions, such as the provision of an overload protection unit, it often comes to irreparable or at least very costly damage to the pressing devices due to malfunction. The fact that these bridging means are integrated in the holding device or cumulatively or alternatively in the hold-down device can significantly reduce the risk of serious damage in the event of a malfunction of the pressing device. In this respect, by means of the bridging means already described in detail above, this danger can also be significantly reduced.

A malfunction may occur due to any failure of the press apparatus. For example, a workpiece from a previous cycle is not properly removed and it is still in the tool of the lower tool unit. Or the counter-holder device does not deviate due to a malfunction of its drive device

The overload protection unit can be of very different design. It is preferably such that, in the event of an error, in particular the drives of the counter-holding device and / or the hold-down device are switched torqueless (Safe Torque Off), so that a drive device designed essentially as a sliding-crank drive can be pressed into its lower stretched position, so that the respective one Plunger part no critical hold-down or counter-holding forces are generated.

A triggering of the actual overload safety unit can be made reliable when the press device comprises a control and / or regulating device, by means of which the overload protection unit in response to the bridging means can be triggered. By means of such a control and / or regulating device, the overload protection unit can be addressed quickly and in a timely manner.

By means of the pneumatic spring device already explained above, a first independent overload protection element can be provided, by means of which a mechanical overload of functional components on the press device can be avoided, even if it does not trigger the actual overload safety unit of the press device. In the present case, the reaction path also immediately provides an overload spring travel.

In this respect, the integration of the pneumatic spring device within a low or counter holding device on press devices is already advantageous for itself, as already described above. For this reason alone, the features in relation to this pneumatic spring device are also advantageous without the other features of the invention.

In particular, by an arrangement of the bridging means between the plunger member and the drive means, the first independent overload protection element can be arranged structurally simply close to a point at which overload forces structurally simple at least partially absorbed and compensated. This applies in particular to the pneumatic spring device.

By means of the present invention, it is particularly well possible to advantageously further develop the precision-cutting and forming presses with servo-toggle lever drive already mentioned above.

These precision cutting and forming presses meet in particular increasing quality requirements and increasing demands on minimum tolerances and especially the requirements, especially of suppliers in the automotive sector. Specifically, with these precision cutting and forming presses in the automotive sector, components with a higher level of smooth cutting can be produced. Thus, the present press apparatus is particularly advantageous for users in the quality field of normal and precision cutting, as these users can significantly expand their production spectrum and produce parts with increased cutting quality. Especially with a precision cutting and forming presses with servo toggle drive, the production costs can be reduced by manufacturing high-precision parts in progressive or transfer tools. In addition, minimal post-processing requirements save time-consuming process steps and accordingly reduce handling costs. In addition, the precision cutting and toggle presses with servo toggle drive for even greater system rigidity, enabling tight component tolerances and reliable repeatability accuracy, with different material thicknesses and strengths. In addition to the optimized design of the forming process by means of follow-on composite or transfer tools, additional process steps can be upstream or downstream. In particular, the precision cutting and forming presses with servo toggle drive during a press passage specifically allows cutting, pulling, embossing, punching and / or calibrating. In addition, upstream or downstream processes, such as thread forming, joining or welding can be integrated here. Thanks to the servo technology, the tappet profile can be optimally adapted to a forming and / or cutting process. In addition, the use of retrofittable low- and counter-holder modules makes it possible to produce sectional parts with an increased proportion of smooth cuts. For the customer, this means an increase in flexibility, output and tool life.

For example, manufacturing processes according to DIN 8580 are subdivided into six main groups, namely altering primary forms, forming, separating, joining, coating and material properties. The separation is made by changing the shape of a solid body, whereby the cohesion is locally canceled completely. The final shape is included in the starting form. The decomposition of composite bodies is also assigned to the separation. The main group separating in turn is further subdivided into cutting, cutting and ablation. Cutting or shearing is part of the subdivision. Precision cutting describes in the context of this work the production of cut parts with a cutting quality, which is to be classified between shear cutting and fine cutting. A further subdivision is made on the basis of the cutting process, depending on the cutting surface to the workpiece boundary. There is a distinction between cutting, punching, cutting, notching, cutting and trimming. Interesting for the precision cutting are the two cutting out procedures and punching. The special feature of cutting and punching is that these methods have a self-contained cutting line. While cutting out the pressed by a punch through the insert workpiece part forms the workpiece and the remainder of the sheet is removed as waste, the cut-out part is waste when punching. It creates an inner contour.

A cutting tool consists essentially of a cutting punch, a die or cutting plate and a hold-down. The hold-down prevents bending and overflowing of the material. The material to be cut of the workpiece can be pushed in the form of boards, as a band or as a strip between the punch and die and separated by downward movement of the cutting punch. In order to avoid jamming of a Butzen generated in this case, the breakthrough through the die is usually not cylindrical, but it is provided with a clearance angle. The actual tool design depends on the requirements of the cut workpiece.

Shearing can be divided into five phases. During the first phase, the hold-down device first applies to the sheet and a hold-down force F _NH is built up. In the second phase, the cutting punch is placed on the sheet, and there is an elastic deformation of the press device and tool. Due to the cutting gap, a bending moment arises in the sheet, which leads to a bending deformation. In the area of the cutting gap, an annular zone is formed. This is the contact area between the sheet surface and the cutting element. In the third phase it comes to the actual cutting phase. Here, the stamp penetrates into the sheet and it is plastically deformed. In the fourth phase, the fluidity of the material is exhausted. It comes to a separation break and the remaining cross-section of the sheet breaks. Due to the sudden demolition of the press device and especially the Upper tool unit or the press ram excited to vibrate. In the fifth and final phase of the punch presses until reaching the bottom dead center of the upper tool unit, the cut slug into the die channel. Usually, the height of fracture surface and smooth cut is evaluated as a proportion of the sheet thickness s. Based on these proportions sheets of different thicknesses can be compared. A high-quality cut part is characterized by a low edge indentation, a small fracture surface fraction and a small cutting burr with a high level of smooth cut and a fracture surface angle of 90 °. In addition to the material used, the material thickness and the state of wear of the cutting elements, the quality of the sectional image is mainly determined by the cutting gap u. If the cutting gap u is too small, cracks occur even when the sheet is cut. Reasons for this are relatively high transverse voltages. On the workpiece no straight cut surfaces, but cracks. If the cutting gap u is too large, cracks occur immediately after the force maximum. The possible cutting gap is u = 0.02 x sheet thickness s to u = 0.1 x sheet thickness s. Also dependent on the cutting gap is the life of the tools. The ratio of smooth cut to broken cut surface is about one-third to two-thirds for a sheared part. Due to the special functional requirements, the cut surfaces of such parts must be reworked. When cutting shear act in and on the sheet forces. "The vertical force components F _V and F _V 'and the horizontal force components F _H and F _H ' act at the cutting gap and form a dynamic equilibrium with the friction forces that occur In order to compensate for the warping, the required counter-torque can be applied by means of a counter-punch Without the holding-down force, the sheet would also be arched above the die To save on the post-processing effort (time, costs) Conventional shear sheath produced In part, methods have been developed which improve the cut surface qualities. During regrooving, the smooth cut portion is increased in two process stages due to better stress conditions in the material. In the first stage, the part is pre-cut with a small allowance to separate this Nachschneidzugabe in a second step by another shear cut. Counter cutting is also a two-step process. A special feature of this method is the double presence of the tool active elements. In the first step, the sheet is cut from one side to just before the break occurs. In the second step, the workpiece is separated from the other side by the second tool. With this method, burr-free and an improved smooth cut portion are achieved. The last modified shear cutting method mentioned is normal cutting with a small cutting gap u <0.05 x sheet thickness s. However, there are no systematic investigations (such as tool life) for this process. Just like conventional shear cutting, fineblanking according to DIN 8580 belongs to the main group separating, to the subdivision division. In contrast to shearing or shearing with a smooth cutting surface, fineblanking involves modified process parameters, which lead to improved quality characteristics of the cut part. Characteristic of the process are the tool design, the forces acting, the ring point and the cutting gap. With the placement of the blank holder ring prongs are pressed into the sheet. In addition, a counter punch presses from below against the sheet. The compressive stresses generated thereby influence the separation process such that the smooth cut portion extends over the entire thickness of the sheet. After the cutting process, the hold-down acts as a scraper. The counter punch acts as an ejector, which pushes the part up out of the die where the cutout is taken. The forces for the ring point and counterholder are generated hydraulically. The cutting force is generated mechanically for machines up to approx. 1,600 kN (≈ 160 t) and hydraulically for larger machines from 2,500 kN to 14,000 kN. The changed process parameters result in a different cutting force profile during fineblanking in contrast to Shearing. The elastic phase and the cutting phase are identical, but the tear-off phase and the swing phase are missing, so there is no cutting hit. As already mentioned, the quality of the cut surface is determined by the cutting gap. While the cutting gap in normal shear cutting is between five and ten percent, this is about 0.5% of the sheet thickness s to be cut during fineblanking.

• Die Nieder- bzw. Gegenhalteeinrichtungen können abhängig von der Bewegung der Oberwerkzeugeinheit verfahren werden
• Die Nieder- bzw. Gegenhalteeinrichtungen können unabhängig voneinander programmierbar werden
• Die Nieder- bzw. Gegenhalteeinrichtung können mit einer Presskraftmessung zur Prozessüberwachung ausgestattet sein
• Die Nieder- bzw. Gegenhalteeinrichtung können eine mechanische Überlastsicherung enthalten, um Schäden zu vermeiden bzw. zu verringern
• Es muss genügen Zeit und Weg zum Beschleunigen vorhanden sein
• Nach abgeschlossener Umformung soll der Gegenhalter der Gegenhalteeinrichtung als Auswerfer fungieren
• Der Bediener muss die Möglichkeit haben, über ein einfaches Bedienkonzept die Nieder- bzw. Gegenhalteeinrichtungen an den Umformprozess anzupassen und gegebenenfalls die Gegenhalte- oder Niederhaltekraft nachzustellen

Irrespective of their embodiments, the low or counterhold device ideally still fulfills the following basic conditions:

• The low or counter holding devices can be moved depending on the movement of the upper tool unit
• The low or counter holding devices can be independently programmable
• The low or counter holding device can be equipped with a press force measurement for process monitoring
• The low or counter holding device may include a mechanical overload protection to prevent or reduce damage
• It must be enough time and way to speed up
• After completion of forming the counter-holder of the counter-holding device should act as an ejector
• The operator must have the possibility of adapting the low or counter holding devices to the forming process by means of a simple operating concept and, if necessary, adjusting the holding or holding force

Figur 1

schematisch eine Ansicht einer Präzisionsschneid- und Umformpresse mit einem Servo-Kniehebelantrieb und mit Überbrückungsmitteln zum Überbrücken einer Auslösezeit zum Auslösen einer Überlastsicherungseinheit und mit einer Steuerungs- und/oder Regelungseinrichtung hierfür;

Figur 2A

schematisch eine Ausgangsstellung einer Antriebseinrichtung mit eingefederter Pneumatikfedereinrichtung der Gegenhalteeinrichtung der Präzisionsschneid- und Umformpresse aus der Figur 1;

Figur 2B

schematisch eine nachfolgende Stellung der Antriebseinrichtung mit ausgefederter Pneumatikfedereinrichtung der Gegenhalteeinrichtung der Präzisionsschneid- und Umformpresse aus der Figur 1;

Figur 2C

schematisch eine weitere Stellung der Antriebseinrichtung mit der synchron zu einer Oberwerkzeugeinheit bewegten Gegenhalteeinrichtung der Präzisionsschneid- und Umformpresse aus der Figur 1;

Figur 2D

schematisch eine andere Stellung der Antriebseinrichtung mit der in eine untere Umkehrlage bewegten Gegenhalteeinrichtung der Präzisionsschneid- und Umformpresse aus der Figur 1;

Figur 3

schematisch ein Schubkurbeltrieb zum beispielhaften Erläutern der Funktion einer Antriebseinrichtung einer Niederhalte- bzw. Gegenhalteeinrichtung der Präzisionsschneid- und Umformpresse aus den Figuren 1 und 2;

Figur 4

schematisch ein Diagramm einer Auswerferkinematik bezüglich der Gegenhalteeinrichtung aus den Figuren 1 bis 3;

Figur 5

schematisch einen Funktionsablauf während eines Bearbeitungsvorgangs an der Präzisionsschneid- und Umformpresse aus der Figur 1; und

Figur 6

schematisch ein Diagramm insbesondere bezüglich einer Kennlinie einer Gegenhalter-Auswerferfunktion im Zusammenhang mit einer Kennlinie eines Schneidstempels.

Further features, effects and advantages of the present invention will be explained with reference to the accompanying drawings and the following description, in which an example Präzisionsschneid- and forming press according to the invention with a toggle lever drive and with a bridging means for bridging a response time for operating an overload safety unit shown and are described. The same components need not be quantified and explained in all figures. In the drawing show:

FIG. 1

1 schematically shows a view of a precision cutting and forming press with a servo toggle drive and with bridging means for bridging a tripping time for triggering an overload safety unit and with a control and / or regulating device therefor;

FIG. 2A

schematically a starting position of a drive device with spring-loaded pneumatic spring means of the counter-holding device of the precision cutting and forming of the FIG. 1 ;

FIG. 2B

schematically a subsequent position of the drive means with spring-loaded pneumatic spring means of the counter holding device of the precision cutting and forming of the FIG. 1 ;

Figure 2C

schematically a further position of the drive device with the synchronously moved to a tool upper tool counter holding device of the precision cutting and forming of the FIG. 1 ;

FIG. 2D

schematically another position of the drive means with the moved in a lower reversing position counter holding device of the precision cutting and forming of the FIG. 1 ;

FIG. 3

schematically a slider crank drive for exemplifying the function of a drive means of a hold-down or counter-holding device of the precision cutting and forming of the FIGS. 1 and 2 ;

FIG. 4

schematically a diagram of an ejector kinematics with respect to the retainer of the FIGS. 1 to 3 ;

FIG. 5

schematically a functional sequence during a machining operation on the precision cutting and forming of the FIG. 1 ; and

FIG. 6

schematically a diagram in particular with respect to a characteristic of a counter-ejector function in connection with a characteristic of a cutting punch.

In the example in the FIG. 1 Pressing device 1 shown is a toggle press 2 and especially to a precision cutting and forming press 3 with a servo toggle lever drive 4. Since such a toggle lever drive 4 is known from the prior art, its components and operation will not continue here received.

The press device 1 has a welded press stand 5, on which on its upper side 6 the toggle lever drive 4 is arranged. Below the servo toggle lever drive 4, a press ram 7 is guided displaceably on the press stand 5 as an upper tool unit 8 in the vertical direction z (pressing direction or ejection direction). The upper tool unit 8 carries as a tool part 9, for example, a cutting punch 10 (see FIGS. 2A to 2C ). On the underside 11 of the press stand 5, a press table 12 is arranged as a lower tool unit 13, by means of which the press stand 5 is fixed on a base foundation 14. The lower tool unit 13 carries a further tool part 15, which in this embodiment a die 16 (see FIGS. 2A to 2D ), through which the cutting punch 10 a slug 17 (see Figure 2C ) can punch out of a in the conveying direction x cyclically promoted workpiece 18. For this purpose, the upper tool unit 8 is moved toward the lower tool unit 13 in the direction z. After punching, the upper tool unit 8 is moved in the direction z back from the lower tool unit 13. The workpiece 18 is in this case a metal strip 19 (see again Figures 2 ). In this exemplary embodiment, the press apparatus 1 additionally comprises an overload safety unit, not shown here, which then comes into action when a malfunction occurs during a machining operation in order to avert greater damage from the press apparatus 1. In order to hold down the workpiece 18 during a machining operation with respect to the lower tool unit 13, the upper tool unit 8 comprises a hold-down device 20. This hold-down device 20 has a plunger part 21 in the form of a hold-down 22. The plunger part 21 is in this case displaceable by means of a drive device 23 with respect to the upper tool unit 8; in the direction z. In order to be able to hold against the workpiece 18 against the actual pressing direction from below during the machining process, the lower tool unit 13 is equipped with a counter-holding device 24. The counter-holding device 24 has a further plunger part 25 in the form of a counter-holder 26. The further plunger part 25 is displaceable here by means of a further drive device 27 with respect to the lower tool unit 13; and also in the direction z. The two separately acting and working drive means 23 and 27 are designed substantially identical except for their respective plunger member 21 and 25 and in this embodiment each comprise an eccentric drive 28 and 29, which is driven by a motor 30 and 31 respectively.

1. 1. Gegenhalten (synchron zur Oberwerkzeugeinheit 8) bis zum Erreichen des unteren Totpunkts - Verweilen - Auswerfen
2. 2. Gegenhalten (synchron zur Oberwerkzeugeinheit 8) über den unteren Totpunkt hinaus - als "Nebeneffekt" auswerfen des ausgeschnittenen Materials
3. 3. Reine Auswerferfunktion

For controlling the press device 1, this comprises a control and / or regulating device 33. In this case, converters (not shown) are connected via EtherCAT connections 35 to a CX (not shown). Data is exchanged with a press control unit 39 and a visualization unit 40 via a PROFIBUS 38. Furthermore, motor-internal rotary encoders 41 for controlling the drive devices 23 and 27, as well as further rotary encoders 42 for determining the position of the low- and counter-holding devices 20 and 24 are connected directly to the converters. To a current or To be able to process simulated press angles in the CX, an axis controller 44 of the press device 1 and the controller or rotary encoder 42 of the drive devices 23 and 27 are connected via a real-time Ethernet (RT-Ethernet) 45. The independently configurable Ethernet ports on the CX allow one of the two ports to be used to connect the CX to a machine / corporate network. The other connection can be addressed independently and thus serves as a pure RT Ethernet connection 45. The counter hold and hold down forces are determined by piezo sensors. In order not to introduce another new system, the same sensors and evaluation units are used as they are also used for press force measurement on the press. The output signal of the piezo sensors is amplified in a charge amplifier and scaled to an analog output voltage of 0 V to 10 V. 0 V corresponds to F = 0 kN; 8V correspond to F = 300 kN. The "missing" 2 V serve as a reserve for the detection of overloads. The output signal of the charge amplifier is read in via the analogue input card and processed further. The low- and counter-holding devices 20 and 24 are position-controlled and partially moved synchronously with the upper tool unit 8. The control PC used in this case is connected directly to the press control unit 39 via a real-time Ethernet connection, so that a synchronous movement to the upper tool unit 8 can be ensured at any time, regardless of which curve is currently being driven by the press machine 1. The movement of the low and counter-holding devices 20 and 24 is preferably realized via an electronic cam. This cam is created individually depending on the process and the selected press curve. Using an input mask, the operator specifies interpolation points for the calculation of this curve. The trajectory for optimal motion control is automatically created by interpolation within the control. If the press device 1 has reached its bottom dead center, the counter-holding device 24 lingers there in the locked position. The ejection movement begins when a predetermined press angle is reached. The controller is programmed to have a Synchronous movement beyond the bottom dead center of the upper tool unit 8 also would be possible. The used configuration Motor - Inverter is regenerative. Free energies of the engine are preferably returned to the DC link of the inverter. If this is fully charged, this energy surplus is fed back into the connection network. In the event that the upper tool unit 8 should only work as a "classic" ejector, this can be selected via the operating mask. Thus, there are three possibilities:

1. 1. counterhold (synchronous to the upper tool unit 8) to reach the bottom dead center - linger - eject
2. 2. counter hold (synchronous with the upper tool unit 8) beyond the bottom dead center - as a "side effect" eject the cut material
3. 3. Pure ejector function

In order to equalize the movement of the further plunger part 25 to the movement of the plunger part 21 as quickly as possible at the time of a cutting start, the press device 1 according to the invention has bridging means 50 (see Figures 2 ) for bridging a response time for safe acceleration, in particular the further drive means 27 (see in particular Figures 2 ), wherein these bridging means 50 are preferably implemented directly in the hold-down device 20 and / or in the counter-holding device 24.

By means of the bridging means 50, the further plunger part 25 can be accelerated solely by the movement of the plunger part 21, thus bypassing the further drive device 27.

Likewise, sufficient time can be made available by means of the bridging means 50 in the event of a malfunction until the actual overload safety unit of the press device 1 can trigger and act.

According to the representations after the FIGS. 2A to 2D the bridging means 50 are explained in more detail by way of example in connection with the counter holding device 24, wherein the reference numerals for clarity on the individual FIGS. 2A to 2D are arranged distributed.

The bridging means 50 are arranged between the further plunger part 25 and a connecting rod 51 of the drive device 27, wherein the bridging means 50 in this embodiment is designed as a pneumatic spring device 52 with a nitrogen spring 53.

For this purpose, the pneumatic spring device 52 has a cylinder housing 54 and a piston part 55 guided therein, wherein the cylinder housing 54 and the piston part 55 include a pressure chamber 57 filled with nitrogen N ₂ as pressure medium 56.

The height 58 of the pressure chamber 57 is in this case selected such that the further plunger part 25 of the counter-holding device 24 can be displaced by approximately 25 mm in the direction z, bypassing the drive device 27. As a result, a sufficiently large time window is available in order to accelerate the drive device 27 accordingly, before the further plunger part 25 is driven with it. On the other hand, the additional plunger part 25 can be displaced downwards by at least 25 mm in the event of an emergency, without the piston part 55 or the drive device 27 having to be moved in this case. This time is gained until the actual overload protection unit can be activated.

In this respect, the pneumatic spring device 52 as a whole provides a reaction path 59 of 25 mm. This reaction path 59 is thus formed by means of the height 58 of the pressure chamber 57 between a piston head 60 of the piston part 55 and a cylinder housing end wall 61 of the cylinder housing 54. The pressure chamber 57 and in particular the piston head 60 are located in a cavity 62 formed overall by the cylinder housing 54.

In this case, the cylinder housing 54 is displaceably guided in a guide bush 63 of the lower tool unit 13, independently of the piston part 55. Thus, the entire cylinder housing 54 during a machining operation in the direction z down to the drive means 27 to be moved. In this case, the piston part 55 does not have to displace correspondingly with the cylinder housing 54.

Nevertheless, the cylinder housing 54 is displaceable relative to the lower tool unit 13 by means of the piston part 55, since the piston head 60 can interact with a shoulder region 64 of the cylinder housing 54 in such a way that the cylinder housing 54 is entrained by the piston part 55 when the piston part 55 moves downward in the direction z is moved to the ground foundation 14.

On the cylinder housing 54, the plunger part 25 by web elements 65 (only exemplified here) spaced from the cylinder housing end wall 61, wherein the web elements 65 through holes 66 (here only exemplified) a top plate 67 of the lower tool unit 13 are performed.

In particular, due to the more complex movements of the counter-holding device 24, it makes sense to subdivide these movements into two phases.

The first phase of countering can be described as a "die cushion phase". After the upper tool unit 8 has passed through its bottom dead center, then begins the second phase of ejection. A sufficiently high requirement for the counter-holding device 24 are with a holding force of 300 kN (= 30 t), with a stroke of 25 mm and with a synchronicity with the upper tool unit 8 at a press stroke of max. 60 strokes per min (based on the standard kinematics, without modification of the ram contour curve).

According to the representations of FIGS. 2A to 2D By way of example, four positions are shown using the example of the counter-holding device 24 during various operating states that are running correctly. The same mechanical conditions preferably also apply to the hold-down device 20.

In the in the FIG. 2A shown starting position, the further plunger part 25 is located on the underside of the metal strip 19. For this purpose, the further drive device 27 has been set such that the cylinder housing 54 has been moved toward the upper tool unit 8 in the direction z by means of the piston part 55. Here, the pressure medium 56 located in the pressure chamber 57 has been compressed such that the piston part 55 is displaced in the cavity 62 by 5 mm in the direction of the cylinder housing end wall 61, whereby the pressure chamber 57 is correspondingly reduced. Here, the upper edge of the cylinder housing 54 - and thus indirectly also the fixedly connected to the cylinder housing 54 counter-holder 26 - abuts against a stop 68. In particular, the nitrogen spring 53, which at once designed a mechanical overload protection, this is thus feathered by 5 mm.

If the upper tool unit 8 now moves in the direction of the lower tool unit 13, the piston part 55 moves downwards by 5 mm until the piston head 60 reaches the shoulder area 64 (see FIG FIG. 2B ). In this action, however, the further plunger part 25 remains unchanged in its previously assumed position (see FIG. 2A ), since the piston part 55 could still move freely in the cavity 62 until then. The pressure of the pressure medium 56 in the pressure chamber 57 is so high that the further plunger part 25, despite the increase in the pressure chamber 57 is not measurable or only negligible compared to the metal strip 19 moves. In this respect, the upper edge of the cylinder housing 54 continues on the stop 68 at. In essence, the movements of the further plunger part 25 and the upper tool unit 8 to this point are asynchronous to each other.

According to the position of the FIG. 2B reaches the tool part 9 of the upper tool unit 8 now the metal strip 19. Only at the beginning of the cutting process is now the other plunger member 25, bypassing the other drive means 27 synchronously moved with the cutting punch 10 down. In this connection, the pneumatic spring device 52 can serve as a "die cushion".

Only after this 5 mm "idle stroke", the further plunger member 25 can be moved directly through the further drive means 27 down (see Figures 2C and 2D ).

According to the other position after the Figure 2C a slug 17 is cut out of the sheet metal strip 19, wherein the further plunger part 25 is subsequently further displaced by the drive means 27 down. This is done inter alia by the fact that the cylinder housing 54 is entrained by the piston member 55.

According to the lower position after the FIG. 2D is the further plunger part 25 in its lowest position, from which it is moved by means of the drive means 27 again in the direction z on the upper tool unit 8. Here, the pressure medium 56 is compressed in the pressure chamber 57 again according to the manner described above and the cycle starts again from the beginning.

As shown by the FIG. 3 is an example of the function of the drive means 23 and 25 simplified by means of a sliding crank drive 75 with r - radius of the crank 76 (eccentricity) [mm]; l - length of the connecting rod 51 [mm]; z - stroke of the plunger part 25 [mm]; α - angle of rotation of the crank 76 [°] and λ - ratio between crank length and connecting rod length illustrated.

The following relationship applies here: $$r*\sin \alpha =l*\sin \beta$$

For the plunger position z, the relationship is established on the basis of the dimensions of the slider crank drive 75 and the angle of rotation α $$z=r-r*\cos \alpha +l-l*\cos \beta$$

und einem Umstellen von [3.1] nach sin β kann cos β folgendermaßen dargestellt werden: $$\cos \beta =\sqrt{1-{\left(\frac{r}{l}\right)}^2*{\sin }^2\alpha }$$

With the help of the known relationship $${\sin }^{}$$$${}^2\beta +{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="imgf0001.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\beta =1$$

and switching from [3.1] to sin β , cos β can be represented as follows: $$\cos \beta =\sqrt{1-{\left(\frac{\mathrm{<figure-callout\; id="2"\; label="r\; l"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r\; </figure-callout>}}{l}\right)}^2*{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\alpha }$$

Substituting equation [3.4] into equation [3.2] yields the ram stroke $$z=r\left(1-\cos \alpha \right)+l\left(1-\sqrt{1-{\left(\frac{\mathrm{<figure-callout\; id="2"\; label="r\; l"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r\; </figure-callout>}}{l}\right)}^2*{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\alpha }\right)$$

für das Schubstangenverhältnis folgt: $$z=r\left(1-\cos \alpha \right)+l\left(1-\sqrt{1-{\lambda }^2*{\sin }^2\alpha }\right)$$

With the abbreviation $\lambda =\frac{r}{l}$

for the push rod ratio follows: $$z=r\left(1-\cos \alpha \right)+l\left(1-\sqrt{1-{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}^2*{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\alpha }\right)$$

The calculation of the ram part stroke according to equation [3.6] gives positive values for z. However, a negative value is more useful for the calculation of the ejector's plunger position. Therefore, the right side of equation [3.6] is multiplied by -1.

As shown FIG. 4 A diagram 78 of the kinematic with respect to ejection for r = 12.5 mm and l = 252.5 mm is now shown.

For in the FIG. 5 In particular, the assumption that the counter-holding device 24 is located in the lower tool unit 13 and the hold-down device 20 in the upper tool unit 8 is valid during a machining process on the press apparatus 1. For the input of position values and for the calculation of the Auswerferverfahrkurve is further assumed that the other plunger member 25 is in the extended position (at top dead center) at α = 0 °. This means that the upper edge 80 of the further plunger part 25 is flush with the lower tool unit 13 or the tool. If the counter holding device 24 is completely lowered (bottom dead center), it is at α = 180 °; s = - 25 mm. To determine the hold-down curve, it makes more sense to work with positive kinematics. In the extended position, the plunger part 21 is fully extended and is at α = 0 °; s = + 25 mm. At a crank angle of α = 180 °, the plunger part 21 is flush with the hold-down device 20th

The speed of the respective ram is calculated with α = ω * t by the derivation of the stroke after the time. $$v=\frac{\mathit{dz}}{\mathit{dt}}=\frac{\mathit{dz}}{d\alpha }*\frac{d\alpha }{\mathit{dt}}=\omega *\frac{\mathit{dz}}{d\alpha }$$

With [3.6] follows from this $$v=r*\omega *\left(\sin \alpha +\frac{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}{2}*\frac{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png"\; state="\{\{state\}\}">sin</figure-callout>}2\alpha }{\sqrt{1-{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}^2*{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\alpha }}\right)$$

As an approximation, the speed can be calculated as follows. $$v_N=r*\omega *\left(\sin \alpha +\frac{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}{2}*\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png"\; state="\{\{state\}\}">sin</figure-callout>}2\alpha \right)$$

berechnet.The torque at the drive shaft at a given load is approximated with $$M\approx F*r*\sin \alpha$$

calculated.

Equation [3.10] describes only the required moment, which exerts the load on the drive. For the design of the drive, the acceleration torque must also be taken into account.

As already mentioned, the function of the counter-holding device 24 can be divided into two separate phases. The first phase is the "die cushion phase" in which the counter-holding device 24 deviates from a defined position in synchronism with the movement of the upper tool unit 8 and serves as a counterholder for the tool part 9 or the workpiece 18. The second phase is the "ejection phase". Upon reaching the bottom dead center of the upper tool unit 8, the first phase is completed. Advantageously, it is provided that the counter-holder device 24 remains in the position reached until then until the defined starting angle (crank angle of the press device 1) is reached at the beginning of the ejection phase.

For the ejection movement, the direction of movement of the counter-holding device 24 is reversed. The ejection phase is terminated at the latest when reaching the top dead center of the press device 1. The movement of the counter-holding device 24 begins with the start of the press device 1 at top dead center. The defined position, from which the counter-holding device 24 must be synchronous with the upper tool unit 8, describes the position of the plunger before the bottom dead center. With a press stroke of 60 strokes per minute and an impact position of 10 mm, the upper tool unit 8 takes about 0.4 seconds to reach the position. During this time, the counter-holding device 24 must have moved to a position of -5 mm.

As shown by the FIG. 6 In a coordinate system 90, for example, functional characteristics are shown using the example of the further plunger part 25 or of the respective counter-holder 26 in connection with the plunger part 21 or the respective cutting punch 10. In this case, the crank angle of the respective drive device 23 or 27 is plotted on the abscissa axis 91 of the coordinate system 90. On the ordinate axis 92, the path 93 of the counter-holder 26 on the one hand and the path 94 of the cutting punch 10 on the other hand are removed.

It can be clearly seen that the counter-holder 26 is displaced into the position 95 by means of the further drive device 27 and subsequently raised by the pneumatic spring device 52 of the bridging means 50 by a further 5 mm and thereby pressed against the underside of the workpiece 18 (cf. FIG. 2A ). If the cutting punch 10 is then moved toward the workpiece 18 from above (cf. FIG. 2B ), the backstop 26 is already at the beginning 96 of the Cutting process to the speed of the cutting punch 10, bypassing the actual further drive means 27 synchronized, up to the time 97, at which the cutting punch 10 is moved back up. Subsequently, the counter-holder 26 can pass through a freely programmable ejector movement 98, wherein the counter-holder 26 in this case is driven by the further drive device 27.

It is understood that the exemplary embodiment explained above is only a first embodiment of the press device 1 according to the invention. In this respect, the embodiment of the invention is not limited to this embodiment.

LIST OF REFERENCE NUMBERS

1

press apparatus

2

Toggle Press

3

Precision cutting and forming press

4

Servo toggle drive

5

press stand

6

top

7

press ram

8th

Upper tool unit

9

tool part

10

cutting punch

11

bottom

12

press table

13

Lower tool unit

14

floor foundation

15

another tool part

16

die

17

slugs

18

workpiece

19

metal strip

20

Hold-down device

21

plunger portion

22

Stripper plate

23

driving means

24

Backup device

25

another ram part

26

backstop

27

further drive device

28

eccentric

29

another eccentric drive

30

engine

31

another engine

33

Control and / or regulating device

35

EtherCAT connections

38

PROFIBUS

39

Press control unit

40

visualization unit

41

internal motor encoders

42

additional encoders

44

Motion

45

Real Time Ethernet connection

50

bridging agent

51

pleuel

52

Pneumatic spring device

53

nitrogen spring

54

cylinder housing

55

piston part

56

lever

57

pressure chamber

58

height

59

pathway

60

piston crown

61

Cylinder housing end wall

62

cavity

63

guide bush

64

shoulders

65

web elements

66

drilling

67

Top panel

68

attack

75

Slider crank mechanism

76

crank

78

diagram

80

top edge

90

coordinate system

91

abscissa

92

axis of ordinates

93

path

94

path

95

position

96

beginning

97

time

98

ejector

x

conveying direction

z

vertical direction

Claims (12)

Pressing device (1), in particular toggle press (2), for machining a workpiece (18) with a lower tool unit (13) and with a top tool unit (8) movable therefor, in which the upper tool unit (8) has a hold-down device (20) with a plunger part (8). 21), by means of which the workpiece (18) to be machined with respect to the lower tool unit (13) can be held down, and the lower tool unit (13) a counter holding device (24) with a further plunger part (25), by means of which the workpiece to be machined (18) against a tool part (9) of the upper tool unit (8) is untenable, wherein the plunger parts (21, 25) in each case by means of a drive means (23, 27) relative to the upper tool unit (8) and / or the lower tool unit (13) are displaceable thereby in that the counter-holding device (24) and / or the hold-down device (20) comprise bridging means (50) for bridging an acceleration phase of the respective drive means (23, 27), in which the respective drive means (23, 27) can be accelerated to the respective ram speed. Press device (1) according to claim 1, characterized in that the bridging means (50) comprise a pneumatic spring device (52). Press device (1) according to claim 2, characterized in that the pneumatic spring device (52) comprises a nitrogen spring (53). A press apparatus (1) according to one of claims 1 to 3, characterized ge denotes that the bridging means (50) includes a pathway of 25 mm, include (59) of more than 10 mm, or more than 20 mm, preferably. Press device (1) according to claim 4, characterized in that the reaction path (59) by means of a pressure medium (56) filled pressure chamber (57) between a piston head (60) of the piston part (55) and a cylinder housing end wall (61) of the cylinder housing ( 54) is formed. Press device (1) according to one of claims 1 to 5, characterized in that the bridging means (50) between the plunger part (21, 25) and the drive means (23, 27) are arranged. Press device (1) according to one of claims 1 to 6, characterized in that the bridging means (50) comprise a cylinder housing (54) and a piston part (55) guided therein, wherein on the cylinder housing (54) the plunger part (21, 25) is arranged. Press device (1) according to claim 7, characterized in that the plunger part (21, 25) by web elements (64) spaced from the cylinder housing end wall (61) on the cylinder housing (54) is arranged. Pressing device (1) according to one of claims 1 to 8, characterized in that the bridging means (50) comprise a cylinder housing (54) and a piston part (55) guided therein, wherein the cylinder housing (54) in the lower tool unit (13) in the pressing direction the upper tool unit (8) is arranged displaceably. Press device (1) according to one of Claims 1 to 9, characterized in that the bridging means (50) comprise a cylinder housing (54). and a piston member (55) guided therein, wherein the cylinder housing (54) is slidably guided in a guide bush (63) of the upper tool unit (8) or the lower tool unit (13). Press device (1) according to one of Claims 1 to 10, characterized in that the bridging means (50) comprise a cylinder housing (54) and a piston part (55) guided therein, the cylinder housing (54) being opposite to the piston housing (55) Upper tool unit (8) or the lower tool unit (13) is displaceable. Press device (1) according to one of Claims 1 to 11, characterized in that the bridging means (50) comprise a cylinder housing (54) and a piston part (55) guided therein, the piston part (55) being attached to a connecting rod part (51) of an eccentric drive (28, 29) of the drive means (23, 27) is arranged.

Images