EP1793946B1 - Method for producing a workpiece by forming under bending conditions - Google Patents

Abstract

A method of producing a workpiece by bending a panel in a bending press, in particular an edge bending press, with measures for compensating deformations of the edge bending press due to load. The measures involve detecting the displacement forces of drive means whilst the panel is being bent at a bending depth of the bending tools that is slightly shorter than a bending depth needed to produce a predefined bending angle. From the detected displacement forces, the bending deformation of the press beams corresponding to them are determined and the displacement force of the drive means is reduced, after which a compensating device is displaced in order to set a complementary camber in support surfaces for the bending tools or tool holders, and the panel is finally bent by displacing the press beam to the bending depth corresponding to the predefined bending angle.

Description

The invention relates to a method for producing a workpiece by bending deformation of a board in a bending press, in particular a press brake, as described in the preamble of claim 1.

In order to counteract a machine deformation, in particular the bending of a table beam and / or a press beam, occurring during loading of a bending press during the bending deformation of workpieces, devices are already known by which bending tools or tool receiving devices for the bending tools are arched in the opposite direction in accordance with an expected bending , An adjustment of these devices and thus the curvature takes place on the basis of empirical values or calculation models for a number of load cases, which result from the position of the tools, tool length and workpiece-dependent forming force.

From the DE 37 09 555 A1 For example, such a device is known in which a plurality of pairs of upper and lower wedges are arranged at intervals for setting up a pressing tool in a convex state between the lower pressing tool and the pressing table at intervals along the longitudinal direction of the press brake. A coordinated sliding movement of the wedges is achieved by a, acted upon by a control drive, extending over the entire length of the press brake, elastic spring element, whereby a bearing surface for the tools or a receiving device for the tools occupies a tailored to the requirements curvature and thus a Compensation for the bending of the table beam and / or press bar is achieved over an entire bending length and so the immersion depth of the bending tools over the entire bending length is approximately equal.

Next is from the DE 32 45 755 A1 a method for correcting the bending line of the bending tool of a bending presses, in particular a press brake, known, in which the lower tool is divided in the direction of the bending line and divided into tool segments tool halves are adjustable transversely to the bending line. The bending line of the upper tool is measured in the vertical plane by means of several encoders. The tool segments of the lower tool are partially motorized analogously to the determined measured values for forming a bending split taper or narrowing in the horizontal plane corresponding to the bending line adjusted, so that the result is an automatic detection and correction of the bending line is guaranteed.

From the CH 508 426 A a press brake is known in which the table bar and / or the press bar have a running over almost the entire length, extending over the entire thickness slot. Through this slot formation and by means of the slot bridging adjusting means, it is possible to give a tool support forming region of the table beam or press bar, depending on the respective position of the actuating means curvature, taking into account the expected bending line.

From the WO 00/13813 A1 Finally, a press brake is known in which the table beams, starting from two-sided end portions extending in the direction of the center, the table beams in its entire thickness severing slots are provided and thus form the support surface for the bending tools forming areas of the table beam cantilevered by means of adjusting devices Change the slot width to achieve a curvature of the support surface to be deformed.

The object of the invention is to provide measures by means of which a variety of occurring load cases of press brakes bill, an exact adjustment of a curvature of load-dependent bending deformations of the table beam and / or press bar is achieved.

This object of the invention is achieved by the reproduced in claim 1 feature combination. The surprising advantage of this is that a compensation corresponding to the real load and thus deformation values is achieved to ensure a high-quality bending deformation, wherein it is further essential according to the invention to convert the bending into a pre-bending and finish-bending operation with a relief of the bending press from the adjusting forces to divide the operations so as to make an adjustment of a compensating device for forming a counter to the deformations of the bending press counter-curvature of at least one support surface for the bending tools or tool holders in a load-free state and thus with significantly reduced restoring forces and high setting accuracy.

But are also advantageous measures according to claims 2 to 4, because thus a low detection effort is achieved with a rapid translation.

The advantageous measure according to claim 5 ensures the effects of asymmetrical loads to compensate for the bending behavior of the table beam and the press bar.

The measures described in claims 6 and 7 ensure that by determining the adjusting forces of the drive means directly in a forming process of a workpiece, stored in a data store deformation data that are included for a number of different load cases in a data matrix, and thus directly a required curvature of a support surface for the bending tools, to compensate for the resulting bending deformation of the table beam or the press bar, manually or mechanically adjustable on a compensating device.

But are also advantageous measures according to claims 8 to 10, whereby a rapid and thus the production process only slightly stressful preparation for a serial but also individual production is achieved.

According to the reproduced in claim 11 measures is advantageously achieved that the deformation data of a bending deformation are determined directly from the determined adjusting forces of the drive means and thus the actual load case by means of arithmetic operation.

However, it is also possible a procedure according to claim 12, whereby a faulty setting is avoided and thus avoiding false creations.

By reproduced in claim 13 measures a largely automated operation is achieved.

Finally, the measures mentioned in claims 14 and 15 ensure variants in the design for adaptation to economic requirements.

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

Fig. 1

eine erfindungsgemäße Abkantpresse in Ansicht;

Fig. 2

eine Detailansicht der Abkantpresse;

Fig. 3

eine schaubildliche Darstellung eines Belastungsfalles bei der Biegeumformung eines Werkteils;

Fig. 4

eine Detailansicht mit schematischer Darstellung eines Umformvorganges, in Ansicht.

Show it:

Fig. 1

a press brake according to the invention in view;

Fig. 2

a detailed view of the press brake;

Fig. 3

a perspective view of a load case in the bending deformation of a workpiece;

Fig. 4

a detailed view with a schematic representation of a forming process, in view.

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 location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and are to be transferred to the new situation mutatis mutandis when a change in position. 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 a simplified schematic representation of a press brake 1 shown, which is formed from a machine frame 2, consisting of side cheeks 3, 4, a fixed press bar 5 and a transverse dressing 6. In guide assemblies 7 of the side cheeks 3, 4 and the cross-dressing 6 another press bar 8 is adjustably mounted in a plane formed by the press bar 5 and relative to this, in the embodiment shown by on the side cheeks 3, 4 immovably arranged drive means 9, 10th a drive device 11, for example hydraulic cylinder 12 of a hydraulic system 13, is actuated, wherein at least one respective hydraulic cylinder 12 engages opposite end regions 14 of the adjustable press beam 8 with piston rods 15 whereby two axle positions 16, 17 for force introduction of the adjusting forces of the drive means 9, 10 are formed on the press beam 8.

On opposite support surfaces 18, 19 of the fixed press bar 5 and the adjustable press bar 8 tool holders 20 are arranged and fastened releasably and adjustably in these opposed bending tools 21, 22.

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 centered with respect to the length 23 of the press beams 5, 8 positioned, resulting in the drive means 9, 10 equally large adjustment forces and symmetrical bending lines on the press beams 5, 8 occur.

In practice, however, eccentric arrangements - as shown in subsequent figures - often common. If shorter bending tools 21, 22 deviating from the length 23 are used, they are often off-center with respect to a center plane 27 running perpendicular to a contact surface 26 and parallel to the side walls 3, 4, e.g. positioned to form two or more tool sets, consisting of the bending tools 21, 22, for alternately use the assembly of the press brake 1 or to achieve better access with already partially formed, angled workpieces 4 to the bending tools 20, 21.

However, such an eccentric arrangement of the bending tools 20, 21 causes an unbalanced load on the press brake 1 because different sized adjusting forces are the result and of course an asymmetrical bending deformation of the table beam 5 and the press bar 8 occurs.

The drive device 11 comprises in the illustrated embodiment, the hydraulic system 13 and has this substantially a container 28 for a pressure medium, such as hydraulic oil, a pump unit 29, a control unit 30 and corresponding connecting lines 31 for acting on the hydraulic cylinder 12.

Further, various detection means 32 are provided for the control of the hydraulic system 13, wherein, as known from the prior art, pressure sensors 33 are arranged in the connecting lines 31, preferably the input side directly to the hydraulic cylinders 12 for pressure determination during a working stroke of the press bar 8 in the Bending operation on the workpiece 4, are attached.

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, as well as 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 detection means, as these correspond to the prior art and are provided on such folding machines. Furthermore, a position measuring device 42 is often connected to the control and / or regulating device 34, by means of which the respective setting position of the adjustable press bar 8 with respect to a reference position - selected zero position - measured and monitored during an adjustment and as a variable control parameter in a control program a device for Verstellwegsteuerung is used.

Preferably, the path measuring device 42 is formed by at the two opposite end portions 14 of the adjustable press beam 8, between this and the fixed side walls 3, 4, known from the prior art, opto-electronic linear scales 43 and an electronic Auswertemessoptik. The arrangement of this path measuring device 42 at the opposite end portions 14 of the press bar 8 thus also allows the determination of parallelism in the adjustment of the press bar 8 and thus the opposing bending tools 21, 22, and thus also the determination and monitoring of an angular position, as in different Adjustment of the drive means 9, 10 occurs or to compensate for the different springing of the side cheeks 3, 4, caused by asymmetric load at eccentric position of the bending tools 21, 22 at different Verstellkräften - according to arrows 44, 45 - and the adjustment can on these deformations be matched.

Of course, other devices known in the art, e.g. Distance lasers, etc. are used.

To determine the resilience of the side cheeks 3, 4 are also a number of methods or devices, such. on the side cheeks 3, 4 arranged strain sensors 46, or in the side cheeks 3,4 or press beams 5, 8 or the piston rod 15 integrally arranged piezoelectric elements or distance lasers etc. possible.

The measures for compensating the occurring under load deformations of the press brake 1 significant determination of the adjustment - according to arrows 44, 45 - takes place directly from the detection of the working pressure of the pressure medium in the hydraulic cylinders 12 by means of the pressure sensors 33rd

However, a further possibility should be pointed out here, namely the adjusting forces - arrow 44, 45 - calculated from the measured springing of the side cheeks 3, 4 using the known machine data, such as cross-sectional dimensioning of the side walls 3, 4 and material-related strength value to determine ,

On the basis of the following FIGS. 2 and 3 is discussed in more detail on the measures to compensate for the deformations of the press brake, the stress-related effects are explained using the example of the adjustable press bar 8, which apply in an approximate form but also for the fixed press bar 5, but with the opposite direction of action.

The position of the bending tools 21, 22 with respect to the length 23 is determined from the measured or calculated adjusting forces - arrow 44, 45 - in an arithmetic operation carried out in the computer 35 and from the workpiece 24, using the working part for the control of the working process dependent Biegelänge 50 on a, from a number of load cases with the associated deformation values, which are stored in the data memory 36 as load cases, accessed. Each of these, stored in the data storage load cases corresponds to a specific bending line 51, and thus a certain Gegenwölbung 52 for correction to the press beams 5, 8 and thus directly a dimensional deviation or angular position of the bending tools 21, 22, the is set when loaded against a neutral line 53 in the unloaded state. From this dimensional deviation, setting values are generated in the computer 35 as corrective measures for adjusting the counter-curvature 52 of the support surfaces 18, 19 on the compensation devices 54.

In Fig. 3 the conditions on the adjustable press bar 8 are shown. Approximately with the same effect is the fixed press bar 5 to judge. Instead of this described method, with the load cases stored in the data memory 36 and the deformation values derived therefrom, it is of course also possible and to be mentioned as a further exemplary embodiment that the determination of the deformation values is carried out by arithmetic operation carried out in the computer 35, using the determined adjustment forces - arrow 44, 45 - and the machine data, to be determined directly upon detection of the adjusting forces.

The balancers 5, 8 are equipped with the adjustable balancing devices 54, and form the support surfaces 18, 19 for the tool holders 20. Such balancers 54 are as manually adjustable or adjustable via drives devices for achieving the Gegenwölbung 52 of the support surfaces 18, 19 for the tool holders 20th

In the illustrated embodiment, the bending tools 21, 22 are provided in an eccentric position to the center plane 27. A resulting force in accordance with arrow 55 from a line load to be applied for the bending deformation of the workpiece 24 according to the bending length 50 is offset by a distance 56 from the center plane 27 in the direction of one of the drive means 9, 10 in the assumed load case.

To determine the necessary for the bending deformation of the workpiece 24 adjusting forces according to - arrow 44, 45 - is now carried out by applying the drive means 9, 10, a forming operation, wherein an engagement depth of the tools 21, 22 - as later described in detail - by regulating the Adjustment of the adjustable press bar 8 is selected smaller than this is required for the production of the final forming angle on the workpiece 24.

This process serves to determine the actual adjusting forces - according to arrow 44, 45.

The adjusting forces which are introduced in the axle positions 16, 17 are determined from the medium pressure measured by the pressure sensors 33 and the pressure surface of the hydraulic cylinders 12. From the sum of the different sized adjusting forces - according to arrow 44, 45 - calculated the resulting total force, - according to arrow 55 - which is required for the deformation of the workpiece 24 and results from the torque set the position "X" for a line of action 57 of resulting total force - arrow 55 - which runs parallel to the adjusting forces - according to arrow 44, 45 -. Thus, the position of the tools 21, 22 with the adjustment forces - according to arrow 44, 45 - and the resulting forming force - according to arrow 53 - measured perpendicular distances 58, 59 is fixed, as shown in detail of Fig. 3 can be seen.

The position of the bending tools 20, 21 and the resulting total force - arrow 55 - and bending length 50 define the concrete load case.

In order to achieve a balance of the deviation from the neutral line 53 caused by bending under the load on the basis of this specific load case, a close load case is now used, from a number of load cases stored in the data memory 36 in the data memory.

These load cases and the resulting deformation measures are for different adjustment forces - arrow 44, 45 and given machine data, e.g. Support length 60, between the axis positions 16, 17 and the dimensional data of the table beam 5, press bar 8, side bolsters 3.4 and the material-related strength values, determined by model calculations and stored in a data matrix in the data memory 36.

Each of these load cases is a characteristic value, e.g. K1 to K10 for example, ten stored load cases, assigned as a predetermined set value for the compensation device 54.

After carrying out a sample deformation on the workpiece 4 and thereby determining the adjustment - arrow 44, 45 is thus directly to the control and / or regulating device 34, a characteristic K1 to K10 displayed which is used for the adjustment of the balancing device 54.

Advantageously, machine-adjustable, e.g. with actuators 61 controllable via the control and regulating device 34, e.g. for a stepwise adjustment of the balancing device 54 according to the characteristic values K1 to K10.

Instead of, for a certain number of load cases stored in the data store deformation data for the bending deformation of the table beam 5, press bar 8 and / or springing the side cheeks 3,4, it is of course also possible, this data by arithmetic operations in real time due to a stored in the computer 35 computer program directly from the determination of the adjusting forces - according to arrows 44, 45 - to determine using the fixed machine data and assign the result to the load case approximately corresponding characteristic, whereby adjustment data for the balancing device 54 are available to set a counter-curvature at the support surfaces 18, 19 ,

In the Fig. 4 is shown in a schematic representation of the forming and adjusting process to achieve a high-quality deformation of a board 25 and described with reference to the figure. The forming process on the board 25 to form a predetermined forming angle 65 is divided into a pre-bending and a finish bending process. In the figure, the pre-bending and in continuous lines the finished bending situation of the board 25 is shown in broken lines.

The illustration shows the fixed press bar 5 and the compensation device 54 which forms the support surface 19 on which the tool holder 20 is attached to the bending tool 22. This arrangement is opposite to the press bar 8, also arranged with the compensating device 54 and the tool holder 20 and bending tool 21 adjustable. The drive means 9 is in the example shown, the hydraulic cylinder 12 with a divided into a pressure chamber 66 and an annular space 67 by a piston 68 cylinder space. The supply of the pressure medium from the hydraulic system via the hydraulic control unit 30 and the connecting lines 31. The pressure chamber 66 is connected upstream as a detection means 32 for an adjusting force during the forming process, a pressure sensor 69th

As already mentioned, the bending process is divided into two stages, this being another Possibility of a single-stage bending process can optionally be done.

In a Vorbiegevorgang an adjustment of the press bar 8 to an engagement depth 70 of the bending tools 21, 22 in which a bending angle 71 is slightly greater than or equal to the predetermined forming angle 65 is achieved. In this case, the adjustment force and thus the load case and the deformation values and from this the correction values for adjusting the compensation device 54 are determined, as already described earlier.

In the annular space 67 is preferably a pressure level upright essentially results from the weight of the press bar 8 thus an additional load entry by the weight of the press bar 8 on the Board is prevented.

This essentially achieves an unloaded state of the press beams 5, 8 but also of the compensation device 54 and an adjustment of the compensation device 54 to form the required counter-curvature of the support surfaces 18, 19, without substantial force-related resistances, e.g. by high friction values on adjusting means of the compensating device, feasible.

After making the appropriate adjustment of the balancing device 54 takes place by acting on the pressure chamber 66 with the pressure medium and thus the adjustment of the press bar 8 for the Fertigbiegevorgang. In this case, a bending engagement 72 of the bending tools 21, 22 is reached in the end position which is greater than the engagement depth 70 and which, taking into account a material-dependent springback behavior for the predetermined deformation angle 65 on the board 25 is required and by the measures of determination and formation of the counter-curvature achieved with maximum accuracy over an entire bending length.

It should be mentioned in conclusion that in mass production, the measures described with the adjustment of the compensation device 54 can be made only at the beginning of a series, ie the first part and the further production can be done with the existing settings or the measures described.

However, if a high production quality is required, or are material-related load fluctuations due to differences in strength of the boards 25 to be expected, of course, the two-stage bending process for each part of a series of parts is applicable.

The embodiments show possible embodiments of the press brake, it being noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but also various combinations of the individual embodiments are mutually possible and this variation possibility due to the teaching of technical action by representational Invention in the skill of those skilled in this technical field. There are therefore also all possible embodiments, which are possible by combinations of individual details of the illustrated and described embodiment, the scope of protection. In particular, there is no limitation with respect to the drive device to operation by means of a pressure medium. Also conceivable are electromechanical drives, e.g. Electromotive spindle drives on which the adjusting forces - arrow 44, 45 - measured or determined by the power consumption of the motors. Also, the reference to the characteristic values K1 to K10 for the adjustment of the compensation device 54 is only to be understood as an example and can be set as needed - whereby a stepless control is conceivable.

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 partially unevenly and / or enlarged and / or reduced in size.

The problem underlying the independent inventive solutions can be taken from the description.

REFERENCE NUMBERS

1

press brake

2

machine frame

3

side cheek

4

side cheek

5

press beams

6

cross-dressing

7

guide assembly

8th

press beams

9

drive means

10

drive means

11

driving device

12

hydraulic cylinders

13

hydraulic system

14

end

15

piston rod

16

axis position

17

axis position

18

support surface

19

support surface

20

tool holder

21

bending tool

22

bending tool

23

length

24

work part

25

circuit board

26

footprint

27

midplane

28

container

29

pump unit

30

control unit

31

connecting line

32

detection means

33

pressure sensor

34

Control and / or regulating device

35

computer

36

data storage

37

Switching and control elements

38

energy

39

power grid

40

management

41

management

42

Path measuring device

43

linear scale

44

arrow

45

arrow

46

Strain gauge sensor

50

bending length

51

elastic line

52

counter-dish

53

neutral line

54

balancer

55

arrow

56

distance

57

line of action

58

distance

59

distance

60

support length

61

adjustment

65

Umformwinkel

66

pressure chamber

67

annulus

68

piston

69

pressure sensor

70

depth of engagement

71

bending angle

72

bending intervention

Claims (15)

1. Method of producing a workpiece (24) by bending a panel (25) in a bending press, in particular an edge bending press (1), with a machine frame (2) preferably comprising two side walls (3, 4) spaced at a distance apart from one another and, connected to them, a press beam (5) equipped with a first bending tool (22) and a press beam (8) equipped with another bending tool (21) which can be displaced in guides relative to it in guides, and having drive means (9, 10) of a drive system (11) for the press beam (8) and a control and/or regulating unit (34) with a computer (35) and data memory (36), and detection means (32) hard-wired to the control and/or regulating unit (34), e.g. pressure sensors, distance measuring sensors, and a compensating device (54) for creating a complementary camber (52) in oppositely lying support surfaces (18, 19) of the press beams (5, 8) for the bending tools (21, 22) or tool holders (20) to counter a bending deformation of the press beams (5, 8) which occurs under load due to displacement forces of the drive means (9, 10), characterised in that once the panel (25) has been positioned between the mutually spaced bending tools (5, 8), the latter are positioned by displacing the displaceable press beam (8) at a bending depth (70) slightly shorter than a bending angle (72) needed to produce a predefined bending angle (65) and to this end the displacement force of each drive means (9, 10) is derived from a measurement value of the detection means (32) in the computer (35), after which the bending deformation of the press beams (5, 8) corresponding to the displacement forces is determined as a function of machine data stored in the computer (35) or from data stored in the data memory (36) and the displacement force of the drive means (9, 10) is reduced, after which the complementary camber (65) of the support surfaces (18, 19) is set by displacing the compensating device (54) and then the panel (25) is actually bent by displacing the press beam (8) by the bending angle (72) corresponding to the predefined bending angle (65).
2. Method as claimed in claim 1, characterised in that the bending deformation of the table beam (5) and/or the press beam (8) is derived from the detected displacement forces and the production data for bending the panel (25) and the machine data.
3. Method as claimed in claim 1, characterised in that the displacement forces for each drive means (9, 10) are determined whilst the panel (25) is being bent on the basis of the pressure level in a pressurising medium applied to the drive means (9, 10).
4. Method as claimed in claim 1, characterised in that the displacement forces for each drive means (9, 10) are determined whilst the panel (25) is being bent on the basis of the power consumption of a drive of the drive means, e.g. an electric motor for a spindle drive.
5. Method as claimed in one of the preceding claims, characterised in that a position of the bending tools (21, 22) by reference to a length (23) of the table beam (5) and/or the press beams (8) is determined on the basis of the displacement force of each drive means (9, 10).
6. Method as claimed in claim 1, characterised in that the bending deformation of at least one press beam (5, 8) and/or the flexing of the side walls (3, 4) is stored in a data matrix in the data memory (36) for a predefined number of load situations.
7. Method as claimed in claim 6, characterised in that once the displacement forces have been determined on the basis of a stored load situation approximately corresponding to the current one, associated setting values for the compensating device (54) are retrieved and the compensating device (54) is adjusted in accordance with the setting values.
8. Method as claimed in claim 1 or 7, characterised in that a characteristic value in the data matrix is assigned to each load situation for setting up the compensating device (54).
9. Method as claimed in claim 8, characterised in that the characteristic value is displayed at the control and/or regulating unit (34).
10. Method as claimed in one of the preceding claims, characterised in that a specific setting is assigned to the characteristic value at the compensating device (54).
11. Method as claimed in claim 1, characterised in that the bending deformation of at least one press beam (5, 8) is derived by a computing operation of the computer (35) from the detected displacement forces of the drive means (9, 10) as well as the position of the bending tools (21, 22) and the bending length (50) and the machine data.
12. Method as claimed in claim 1 or 11, characterised in that a characteristic value is assigned to respective predefined ranges of the bending deformation.
13. Method as claimed in one of the preceding claims, characterised in that control signals are generated from the characteristic value in the control and regulating unit (34), and displacement drives (61) of the compensating device (54) are activated in order to set up the compensating device (54) on the basis of the characteristic values.
14. Method as claimed in one of the preceding claims, characterised in that the compensating device (54) is set in stages predefined by the characteristic values.
15. Method as claimed in one of the preceding claims, characterised in that the compensating device (54) is set steplessly.

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