EP1902792B1 - Method for operating a bending press, in particular a press brake - Google Patents

Description

The invention relates to a method as described in the preamble of claim 1.

From the WO 02/13986 A1 the same applicant is a method for operating a bending press, in particular press brake, known, according to which during a forming process for a workpiece IST - pressing forces of drives of the drive assembly are determined and deposited by means of this in a data storage for production and machine data, for different load cases stored machine data adjustment paths of the drives for the power stroke are regulated differently.

US4524582-A describes a method according to the preamble of claim 1.

The object of the invention is to provide a method for controlling Verstellphasen the drive device, with which a minimization of the cycle time is achieved by an automatic detection of the application time of drive means for initiating a Eilrückhubes.

This object of the invention is achieved by the reproduced in the characterizing part of claim 1 measures. The surprising advantage is that the time for the activation of the feed device for a Eilrückhub of the press bar in the upper reversing position in response to the varying Verstellkräfte on the detection of the parameter upon reaching a predetermined target value automatically and without due to a safety time overhead Time delay occurs, whereby on the one hand a gentle operation of the press brake is secured and the cycle time is reduced for a forming process.

Also advantageous are the measures according to claims 2 and 3, whereby the applied during the forming process on a workpiece by the drive device and decisive for a deformation of the relevant machine elements of the press brake adjusting forces are detected as parameters for control measures for relief.

According to the measures mentioned in claims 4 and 5, machine-specific a suitable control function for a controlled reduction of the forces acting on the components of the press brake deformation forces are set.
However, measures are also possible as in claim 6, because a shortening of the discharge phase and thus a shortening of the cycle time of a forming process is achieved.

Also possible are the advantageous measures according to claim 7, whereby a shortening of the return stroke for the press bar is achieved.

By the mentioned in claim 8, advantageous measures, the discharge state is detected without delay.

According to the measures mentioned in claims 9 to 11 further physical parameters can be used for the regulation of a discharge phase.

The object of the invention is also achieved by the reproduced in claim 12 measures. The surprising advantage here is that by determining a discharge stroke from the effectively detected adjusting force of the drive means in conjunction with the stroke position easily controllable by the stroke position, another parameter for the control of the drive means is present, for example, draw for a comparison in the control method zoom is, or directly causes control functions.

Possible advantageous measures also describe claims 13 to 18, according to which all necessary data for determining a differential path and thus a discharge stroke between a theoretical lower reversing position and an effective lower reversing position are available during a forming process.

Also advantageous are measures according to claim 19, because this eliminates the creation of large files and storage capacity is saved and the required results are quickly available from the computer.

According to the measures described in claim 20, a very simple control and monitoring process is achieved.

Also advantageous are the measures according to claims 21 to 23, whereby rule variants, as they are useful for different machine configurations, are available.

Finally, measures according to claims 24 and 25 are also advantageous, because thereby an adaptation of the control function "rapid return stroke" effecting the actual value of the adjusting force to the process-related different effective adjustment values is achieved.

For a better understanding of the invention, this will be explained in more detail with reference to the embodiments shown in FIGS.

Fig. 1

eine erfindungsgemäße Fertigungsanlage in Ansicht zur Durchführung des Verfahrens;

Fig. 2

ein erfindungsgemäßes Antriebssystem der Fertigungsanlage in vereinfachter Darstellung;

Fig. 3

eine Detaildarstellung eines Umformvorganges an einer Platine mit in einer unteren Umkehrposition befindlichem Biegewerkzeug eines verstellbaren Pressenbalkens.

Show it:

Fig. 1

a production plant according to the invention in view for carrying out the method;

Fig. 2

an inventive drive system of the manufacturing plant in a simplified representation;

Fig. 3

a detailed view of a forming process on a board with located in a lower reversing position bending tool of an adjustable press bar.

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the position information selected in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and are to be transferred to a new position analogous to the new situation. Furthermore, individual features or combinations of features from the different exemplary embodiments shown and described can also represent independent, inventive or inventive solutions.

In the Fig. 1 is shown in a simplified, schematic representation of a press brake 1, which is formed from a machine frame 2, consisting of side posts 3, 4, a fixed table bar 5 and a cross-dressing 6. In guide assemblies 7 of the side walls 3, 4 and the cross-dressing 6 is a press bar 8 in a plane formed by the table bar 5 level and relative to this adjustable, in the embodiment shown by the side posts 3, 4 immovably arranged drive means 9, 10 a Drive device 11, for example hydraulic cylinder 12 of a hydraulic system 13, is actuated, depending on a hydraulic cylinder 12 is attached to the side posts 3, 4 and hinged to opposite end portions 14 of the adjustable press bar 8 with piston rods 15 and thus two axis positions 16, 17 for the initiation of Forming adjusting forces on the press bar 8.

On opposite end faces 18, 19 of the table beam 5 and the adjustable press bar 8 tool receiving devices 20 are arranged and secured in these opposing bending tools 21, 22 or tool sets from a juxtaposition of individual tools.

In the illustrated embodiment, the bending tools 21, 22, which do not extend over an entire length 23 of the table beam 5 and the press bar 8, for the manufacture of a work piece 24, e.g. by bending deformation of a board 25, e.g. from a sheet metal blank, positioned off-center with respect to the length 23 of the table beam 5 and press bar 8.

Such an arrangement is often customary if shorter bending tools 21, 22 deviating from the length 23 are used, which are then positioned eccentrically with respect to a center plane 27 running perpendicular to a contact surface 26 and parallel to the side cheeks 3, 4, For example, if two or more sets of tools consisting of the bending tools 21, 22, the alternation of the press brake 1 are provided for the alternate use.

The drive device 11 comprises in the illustrated embodiment, the hydraulic system 13 and essentially has a container 28 for a pressure medium, such as hydraulic oil, a pump unit 29, a control unit 30 and corresponding connecting lines for acting the hydraulic cylinder 12. Further, detection means 32 are provided for the regulation of the hydraulic system 13, reference being made in particular to pressure sensors 33 in the connection lines 31, which are preferably arranged directly on the hydraulic cylinders 12.

The operation of the press brake 1 is controlled and regulated by a control and / or regulating device 34, which essentially comprises a computer 35 with data memory 36 and the correspondingly required switching and control elements 37. The controller 34 is powered by a power source 38, e.g. a power grid 39, fed via lines 40 with energy and is connected via lines 41 to be controlled and supplied with energy control, detection and securing means. Furthermore, the control and / or regulating device 34 comprises a path measuring device 42, by means of which the respective setting position of the adjustable press bar 8 is measured and monitored with respect to a reference position during an adjustment process and used as a variable control parameter in a control program for Verstellwegsteuerung.

Preferably, the Wegmessvorrichtung 42 is formed by an opto-electronic measuring devices which are arranged at the two opposite end portions 14 of the press bar 8 and determine the respective position of the bending beam on arranged on the fixed side walls 3, 4, known from the prior art linear scales 43 and their measurement results are transmitted to the control and / or regulating device 34 and evaluated.

The arrangement of this Wegmessvorrichtung 42 at the opposite end portions 14 of the press bar 8 thus also allows the determination of the parallelism of the adjustment of the press bar 8 with respect to the table bar 5 and thus the opposing bending tools 21, 22, as well as the determination or monitoring of an angular position, such as it occurs at different displacement of the drive means 9, 10 or to compensate for different springing of the side stand 3, 4 - caused by asymmetric load by eccentric position of the bending tools 21, 22, and connected by different in the axle positions 16, 17 to be introduced adjusting forces - according to Arrows 44, 45 - in order to apply them as needed to these deformations.

Of course, the path measuring device 42 may be any other device known in the art, e.g. a distance laser can be used. To determine the resilience of the side stands 3, 4 are also a number of methods or devices, such as. Dehnmesssensoren 46 arranged on the side posts 3, 4 or piezo elements or laser beam measuring devices integrated in the side cheeks 3,4 are possible.

For the control and thus the operation of the press brake 1, the detection of the load condition and derived physical parameters is essential. The load state is directly from the operating state of the drive means 9, 10 and thus from the measured values of the detection means 32, e.g. derive the pressure sensors 33 or in the case of electric drives determined by current measuring means drive power, e.g. to calculate according to predetermined formulas in the computer 35 or to determine by comparison with stored in the data memory 36 models or files.

In any case, essential for the operation of the press brake is a production method for a precise production of the workpieces in an economical use of the press brake, i. among other things under operating conditions, which guarantee trouble-free long-term operation with minimized cycle times.

An essential factor for minimizing the total cycle time of a forming operation is a relief phase in which controlled relaxation of the entire system by depressurization and deformation recovery in a discharge stroke from a lower reversing position (= bottom dead center) of the adjustable press bar 8 takes place before an impingement of the drive means 9, 10 is initiated for an express return.

In this unloading the occurring depending on the adjusting force return spring forces of the board 25 or workpiece and restoring forces from the springing of the side cheeks 3, 4 and the bending of the press bar 8 degraded before without detrimental effects for the drive device 11 and the loaded components of the press brake is reversed to Eilrückhub. In the case of the described press brake 1 with the hydraulic drive device 11, the exact time for reversal by means of the medium pressure in the hydraulic cylinders 12 on the piston side as a parameter detected Pressure sensors 33 detected automatically.

In the Fig. 2 is a simplified representation of a hydraulic drive system 50 for the press bar 8 by means of the hydraulic cylinder 12 is shown, wherein the representation and description is limited to a drive side of a naturally symmetrical drive device 11 and independently of course also per drive side, based on a center plane 27, a plurality For example, four hydraulic cylinders 12 may be provided for operating the press bar 8.

In essence, the hydraulic drive system 50 preferably forms a central reservoir 28 for the pressure medium and the controllable pump unit 29, from which a pressure line 31 leads to the control valve 30 formed by a proportional control valve 30 via which the hydraulic cylinder 12 via connecting lines 53, 54 depending on Regulation of the proportional control valve 52 in a piston pressure chamber 55 or rod pressure chamber 56 is applied to the medium. Between the proportional control valve 52 and the container 28 further extends a return line 57 for the return of the medium from the hydraulic cylinder 12, which according to the position of the proportional control valve 52 either with the connecting line 53, which acts on the piston pressure chamber 55, or with the connecting line 54, which acts on the rod pressure chamber 56, fluidly connected.

Further required for controlling the movement of the press bar 8 control components are for example a connected to the connecting line 53 for the piston pressure chamber 55 suction valve 58 with a Nachsaugleitung 59 for the medium from the container 28. Further controls are in the control circuit with the connecting line 54 for the rod pressure chamber 56th provided hold-up valve 60 and a counter-valve 61st

In the connecting line 53 for the application of the piston pressure chamber 55 or directly on the input side, the pressure sensor 33 is provided on the hydraulic cylinder 12.

The movement control of the press bar 8 is effected by the corresponding control of the control arrangement 62 described from the aforementioned valves via the control and regulating device 34. The valves are preferably provided with electric drives 63, which are connected via lines 64 to the control and / or regulating device 34 are and many a one-sided admission of the valves against the measures provided for in the valve spring assemblies 65 which cause a basic position takes place.
As a precautionary measure, it is pointed out that, for simplification of the illustration and description, only the components of the drive system 50 guaranteeing the function of the press brake 1 according to the invention are shown and described, and furthermore a number of monitoring and control means may be provided in the drive system 50.

To carry out a working stroke - according to arrow 44 - and a return stroke - according to arrow 66 - is carried out below.

The working stroke - according to arrow 44 - is carried out to minimize the duty cycle in accordance with the specified safety guidelines with different speeds for express, approach and Umformzustellung, the Umsteuerpunkte for the speed change by the control program depending on the assembly of the press brake 1, according to the used Bending tools and to be carried out on the workpiece forming part and be indexed via the path measuring device 42.

In the Fig. 3 is in full lines the engagement position of the bending tools 21, 22 for forming the circuit board 25 to achieve a predetermined bending angle for the workpiece 24 67 shown. Due to a material-dependent springback behavior of the board 25 and a real thickness 68 of the board 25, and other factors such as bending radius, tool training, etc., an immersion depth 69 is to be specified, which is greater than a theoretical insertion depth 70 to achieve the bending angle 67.

Further, the adjustment force to be applied during the working stroke - as indicated by arrow 44 - causes a reaction force 71 on the press brake 1 and thus springing of the side cheeks 3, 4 and bending of the press bar 8 - as shown in broken lines on the press bar 8. This, as well as the springback of the board 24 require a correction of the travel of the press bar 8, a differential path 72 in an effective lower reversing position relative to a theoretically lower reversing position. This differential path 72 is equal to the dependent of the required forming force springing the side cheeks 3, 4, the bending or deformation of the table beam 5, press bar 8, bending tools 21, 22 and springing of the board and is therefore to be based on a correction of the stroke, and is preferably in a load / deformation matrix in the data memory of the control - And / or control device deposited and based on the parameter of the pressure of the pressure medium, as determined by the pressure sensor 33 during the forming process, the control of the movement of the press bar 8 basis.

After reaching the required for the required bending angle 67 immersion depth 69 is to minimize the duty cycle, a quick reversal of the hydraulic cylinder 12 to a quick return stroke according to - arrow 66 - strive for.

For this purpose, it is provided by the method according to the invention that after reaching the immersion depth 69, before the reversal of the hydraulic cylinder 12 to return stroke and pressurization of the rod pressure chamber 56, a discharge phase for reducing the return spring force of the board 25 and the restoring forces from the springing of the side cheeks. 3 , 4 and springback of the bending or deformation of the machine and tool components as already described above caused reaction force 71 controlled by pressurization of the hydraulic cylinder 12, according to a stored in the data storage 36 control function to a predetermined target value to reduce harmful load surges in the drive device 11th and the construction elements of the press brake 1 during a reversal of the drive device (11) or to act on the drive means 9, 10 to avoid.

The control of the hydraulic cylinder 12 for pressurizing the rod pressure chamber 56 is carried out to minimize a reaction time after reaching the predetermined target value corresponding to a control ramp of the control function automatically by the permanent detection of the physical parameter by the pressure sensor 33. If this target value is reached, the reversal takes place the hydraulic cylinder 12 on Eilrückhub.

However, according to the method of the invention, a control process is also possible which is initiated by increasing the pressure in the rod pressure chamber 56 to system pressure, which corresponds to the maximum pressure of the hydraulic drive system 50, in order to generate the largest possible pressure in the piston pressure chamber 55. This pressure is necessary to a corresponding to obtain large pressure difference at the proportional control valve 63 and thereby achieve a high but controlled decompression speed. This process continues until, in the piston pressure chamber 55, the system pressure has been reduced via the area ratio of the rod-side annular piston surface to the piston surface. Now, the pressure in the piston pressure chamber 55 along the control ramp of the control function is lowered by means of the proportional control valve 63. This process is ended when the ambient pressure, preferably approximately 1 to 3 bar, above atmospheric pressure is applied to the pressure sensor 33 as a set value. Thus, the restoring forces arising from the deformations on the machine elements as well as on the bending part on the controlled and controlled pressure reduction in the piston pressure chamber 55 are reduced to an extent to the admission of the hydraulic cylinder 12 for a rapid return stroke with simultaneous opening of the Nachsaugventils 58 via the control and / or To make control device 34 without occurrence of shock loads.

The control ramp determined in the control function can be linear, stepped or exponential, wherein preferably an exponential curve of the control ramp is provided.

The method according to the invention also makes it possible to monitor or determine the unloading state by determining the load-dependent unloading stroke via the parameter of the adjusting force to be applied to the drive means 9, 10 for forming the plate 25. Starting from this parameter, the machine-related deformation files stored in the data memory 36 are used , Bar models, etc., or determined by calculations in the computer 35 according to stored equations of the deformation, consisting of springing of the side stand 3,4, deflection of the press bar 8 and Rückfederweg the board 25. The result thus determined is equal to the discharge stroke for reducing the reaction force and is controllable by means of the path measuring device 45 and can additionally or as a comparison value for the determination of the switching point for the Eilrückhub application.

It should be noted that the illustrated embodiment of the press brake is only one possible embodiment and is not to be considered as a limitation for the application of the method according to the invention. Of course, the described methods are also applicable according to the invention in deviating from the illustrated embodiments training.

In particular, it should be noted that a hydraulic drive system for a press brake has been used for the detailed description. However, it is to be understood that the same load dependent effects will also occur in a drive system with other drive systems. electric drives, such as electric motor operated eccentric, crank or spindle drives occur on a press brake and the inventive method can equally be used in these drive systems for the application and thus the application also falls for such solutions under the scope of the method.

For the sake of order, it should finally be pointed out that for a better understanding of the construction of the press brake, these or their components have been shown partly unevenly and / or enlarged and / or reduced in size. <B> Reference Numbers </ b> 1 press brake 36 data storage 2 machine frame 37 Switching and control elements 3 kickstand 38 energy 4 kickstand 39 power grid 5 bench beam 40 management 6 cross-dressing 41 management 7 guide assembly 42 Displacement measuring device 8th press beams 43 linear scale 9 drive means 44 arrow 10 drive means 45 arrow 11 driving device 46 Strain gauge sensor 12 hydraulic cylinders 50 drive system 13 hydraulic system 14 end 51 pressure line 15 piston rod 52 A proportional control device 53 connecting line 16 axis position 54 connecting line 17 axis position 55 Piston pressure chamber 18 support surface 19 support surface 56 Rod pressure chamber 20 tool holder 57 Return line 58 cavitation valve 21 bending tool 59 subsequent suction 22 bending tool 60 High holding valve 23 length 24 work part 61 Back-pressure valve 25 circuit board 62 control arrangement 63 drive 26 footprint 64 management 27 midplane 65 spring assembly 28 container 29 pump unit 66 arrow 30 control unit 67 bending angle 68 thickness 31 connecting line 69 Immersion depth 32 detection means 70 Immersion depth 33 pressure sensor 34 Control and / or regulating device 71 reaction force 35 computer 72 Differential travel

Claims (25)

1. A method for operating a bending press, in particular a press brake (1), with a machine frame (2) consisting substantially of lateral uprights (3, 4) and a bench beam (5) and with a press beam (8) mounted adjustably relative to the bench beam (5) in a guide arrangement (7) on the lateral uprights (3, 4), and with a drive device (11), e.g. hydraulic drive system (50), or electromotive spindle drive etc., with at least one drive means (9, 10) for the press beam (8) and with a control- and/or regulating arrangement (34) with a computer (35) and data memory (36) and with a distance measurement device (42) for an adjustment travel of the press beam (8) between an upper and lower reversal position and with at least one detection means (32) for the detection at least of one physical parameter for determining the adjustment force applied on the press beam (8) by the drive device (11) or respectively the drive means (9, 10), characterized in that a reaction force (71) determined in the lower reversal position from the parameter detected by the detection means (32), brought about by spring-back forces of the lateral uprights (3, 4), press beam (8) and of a workpiece, is detected as actual value and is reduced to a predetermined desired value according to a control function deposited in data memory (36) or computer (35) with permanent detection of the physical parameter, and thereafter the drive means (9, 10) is acted upon with energy for a rapid return stroke into the upper reversal position.
2. The method according to claim 1, characterized in that the physical parameter detected by the detection means (32) is a pressure of a pressure medium.
3. The method according to claim 1 or 2, characterized in that as parameter, the pressure of the medium in a piston pressure chamber (55) of a hydraulic cylinder (12) is detected.
4. The method according to one of the preceding claims, characterized in that the control function forms a linearly-running control ramp.
5. The method according to one of the preceding claims, characterized in that the control function forms an exponentially-running control ramp.
6. The method according to one of the preceding claims, characterized in that the control function for the reduction of the reaction force makes provision that the medium pressure in a rod pressure chamber (56) of the hydraulic cylinder (12) is increased to a pressure dependent on the piston speed, until a medium pressure reduced via an area ratio of ring piston area to piston area is reached in the piston pressure chamber (55), thereafter the medium pressure in the rod pressure chamber (56) is reduced to a circulation pressure and thereafter the medium pressure in the piston pressure chamber (55) is reduced according to the control function and thereafter the hydraulic cylinder (12) in the piston pressure chamber (55) is acted upon with the pressure medium for a rapid return stroke into the upper reversal position.
7. The method according to one of the preceding claims, characterized in that simultaneously with the action upon the hydraulic cylinder (12) for the rapid return stroke, a suction valve (58) of the drive device (11) is opened to achieve a high adjustment speed.
8. The method according to one of the preceding claims, characterized in that a permanent evaluation of the parameter detected by the detection means (32) takes place in the computer (35) of the control- and/or regulating device (34).
9. The method according to claim 1, characterized in that the parameter for detection of the adjustment- or respectively reaction force is determined by a measured value of a measurement device for a deformation force, e.g. tensile force, bending force etc., on the lateral upright, press beam etc., wherein the measurement device comprises strain gauge sensors (46) arranged on the lateral uprights (3, 4), or piezo elements arranged in an integrated manner in the lateral uprights (3,4), or laser beam measurement devices.
10. The method according to claim 1, characterized in that the parameter is determined by a measured value of a current measurement means measuring a current- or power consumption of an electric drive means (9, 10), e.g. electric motor of an eccentric drive, crank drive, spindle drive etc.
11. The method according to claim 1, characterized in that the parameter is determined by detection of a drive power e.g. of a torque applied by the drive means (9, 10) for the adjustment of the press beam (8).
12. The method according to claim 1, characterized in that during a working stroke for deformation of a plate (25) into the lower reversal position, the adjustment force applied by the drive device (11) for the adjustment of the press beam (8) is determined by the computer (35) of the control- and regulation device (34) from a physical parameter measured by the detection means (32), whereupon the deformation data of the lateral uprights (3, 4) and of the press beam (8) occurring as a function of the adjustment force and a spring-back travel of the plate (25) is determined as differential travel (72) between a theoretical and an effective lower reversal position of the press beam (8), which is established as relief stroke from the lower reversal position in the direction of the upper reversal position, which is carried out by activation of the drive means (9, 10) with energy, according to the control function deposited in the control- and/or regulation device (34) or in the data memory (36), and thereafter the action upon the drive means (9, 10) of the drive device (11) with energy takes place for a rapid return stroke.
13. The method according to claim 12, characterized in that the machine data for the deformation data for a predetermined number of loading cases are deposited in a load-deformation matrix in the data memory (36).
14. The method according to claim 12 or 13, characterized in that the deformation data of the bench beam (5) and/or of the press beam (8) are determined from a bench model deposited in the data memory (36).
15. The method according to one of claims 12 to 14, characterized in that the spring-back travel of the plate (25) is determined by calculation from material- and deformation-specific data.
16. The method according to one of claims 12 to 15, characterized in that the spring-back travel of the plate (25) is determined by models deposited in the data memory (36).
17. The method according to one of claims 12 to 16, characterized in that the spring-back travel of the plate (25) is determined by test deformation at least of one plate (25).
18. The method according to one of claims 12 to 17, characterized in that the deformation data of the lateral uprights (3, 4) are determined from an upright model deposited in the data memory (36).
19. The method according to claim 12, characterized in that the deformation data for the resilience of the lateral uprights (3, 4) and/or for the flexion of the bench beam (5) and/or of the press beam (8) in real time are determined by a computer operation according to deposited equations, in particular FEM equations, by the computer (35) from the measured values determined by the detection means (32) for the adjustment forces of the drive means (9, 10).
20. The method according to claim 12, characterized in that the relief stroke from the effective into the theoretical reversal position is monitored by the distance measurement device (42) and on reaching the theoretical reversal position, the action upon the drive means (9, 10) with energy takes place for the rapid return stroke via the control- and regulation device (34).
21. The method according to one of claims 12 to 20, characterized in that the reduction of the adjustment forces during the relief stroke is regulated via the control function according to a linearly-running control ramp.
22. The method according to one of claims 12 to 21, characterized in that the reduction of the adjustment forces during the relief stroke is regulated via the control function according to an exponentially-running control ramp.
23. The method according to one of claims 12 to 22, characterized in that the reduction of the adjustment forces during the relief stroke is regulated via the control element (32) according to a control ramp running in a stepped manner.
24. The method according to one of claims 12 to 23, characterized in that a desired value of the adjustment force after the relief stroke is approximately 2% to 30% of the actual value of the adjustment force before the relief stroke.
25. The method according to claim 1 or 12, characterized in that the detection of the actual value of the reaction force and the control process for reduction of the actual value to the predetermined desired value takes place cyclically, i.e. per method cycle for a deformation process on the workpiece.

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